Anti-FGFR2 antibodies in combination with chemotherapy agents in cancer treatment

Abstract

This application relates to uses of antibodies against fibroblast growth factor receptor 2 (FGFR2), including antibodies against the FGFR2 isoform FGFR2-IIIb (also known as FGFR2b), in treatment of certain cancers in combinations with mFOLFOX6 chemotherapy.

Description

(19) *EP004650004A2* (11) EP 4 650 004 A2 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: 19.11.2025 Bulletin 2025 / 47 (21) Application number: 25192038.5 (22) Date of filing: 15.05.2018 (51) International Patent Classification (IPC): A61P 35 / 00 (2006.01) (52) Cooperative Patent Classification (CPC): C07K 16 / 28; A61K 39 / 00; A61K 39 / 395; A61P 35 / 00; C07K 16 / 22; A61K 2039 / 505; A61K 2039 / 54; A61K 2039 / 545; A61K 2300 / 00; C07K 2317 / 90 (84) Designated Contracting States: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR (30) Priority: 16.05.2017 US 201762507053 P 06.11.2017 US 201762581992 P (62) Document number(s) of the earlier application(s) in accordance with Art. 76 EPC: 18730518.0 / 3 624 837 (71) Applicant: Five Prime Therapeutics, Inc. South San Francisco, CA 94080 (US) (72) Inventors: • COLLINS, Helen L. South San Francisco California, 94080 (US) • HNATYSZYN, James South San Francisco California, 94080 (US) • XIANG, Hong South San Francisco California, 94080 (US) • ZHANG, Xiang South San Francisco California, 94080 (US) (74) Representative: Dörries, Hans Ulrich df-mp Patentanwälte Rechtsanwälte PartG mbB Theatinerstraße 16 80333 München (DE) Remarks: •The complete document including Reference Table(s) and the Sequence Listing(s) can be downloaded from the EPO website •This application was filed on 28‑07‑2025 as a divisional application to the application mentioned under INID code 62. •Claims filed after the date of filing of the application / after the date of receipt of the divisional application (Rule 68(4) EPC). (54) ANTI‑FGFR2 ANTIBODIES IN COMBINATION WITH CHEMOTHERAPY AGENTS IN CANCER TREATMENT (57) This application relates to uses of antibodies against fibroblast growth factor receptor 2 (FGFR2), in- cluding antibodies against the FGFR2 isoform FGFR2- IIIb (also known as FGFR2b), in treatment of certain cancers in combinations with mFOLFOX6 chemother- apy. EP 4 65 0 00 4 A 2 Processed by Luminess, 75001 PARIS (FR) Description

[0001] This application claims the benefit of priority to United States Provisional Application No. 62 / 507,053, filed on May 16, 2017, and United States Provisional Application No. 62 / 581,992, filed on November 6, 2017, and which are incorporated by reference in their entirety. FIELD

[0002] This application relates to uses of antibodies against fibroblast growth factor receptor 2 (FGFR2), including antibodies against the FGFR2 isoform FGFR2-IIIb (also known as FGFR2b), in treatment of certain cancers in combinations with mFOLFOX6 chemotherapy. BACKGROUND

[0003] The fibroblast growth factor (FGF) family members bind to four known tyrosine kinase receptors, fibroblast growth factor receptors 1‑4 (FGFR1‑4) and their isoforms, with the various FGFs binding the different FGFRs to varying extents (Zhanget al., J. Biol. Chem.281:15694, 2006). Aprotein sequenceof humanFGFR2 is provided in,e.g.,GenBank Locus AF487553. Each FGFR consists of an extracellular domain (ECD) comprising three immunoglobulin (Ig)‑like domains (D1, D2 andD3), a single transmembrane helix, and an intracellular catalytic kinase domain (Mohammadi et al., Cytokine Growth Factor Revs, 16:107, 2005). FGFs bind to the receptors primarily through regions in D2 and D3 of the receptors. There is a contiguous stretch of acidic amino acids in the linker between D1 and D2 called the "acid box" (AB). The region containing D1 andAB is believed to be involved in autoinhibition of the receptor, which is relieved by binding to ligand.

[0004] The FGFRs are characterized by multiple alternative splicing of their mRNAs, leading to a variety of isoforms (Ornitz et al., J. Biol. Chem. 271:15292, 1996; seealsoSwiss-Prot P21802and isoformsP21802‑1 to ‑20 for sequences of FGFR2and its isoforms).Notably, there are formscontainingall three Ig domains (α isoform)or only the two IgdomainsD2 and D3 domains without D1 (β isoform). In FGFR1, FGFR2, and FGFR3, all forms contain the first half of D3 denoted IIIa, but two alternative exons can be utilized for the second half of D3, leading to IIIb and IIIc forms. For FGFR2, these are respectively denoted FGFR2-IIIb and FGFR2-IIIc (or just FGFR2b and FGFR2c); the corresponding beta forms are denoted FGFR2(beta)IIIb and FGFR2(beta)IIIc. The FGFR2-IIIb form of FGFR2 (also denoted K-sam-II) is a high affinity receptor for both FGF1andKGF familymembers (FGF7, FGF10, andFGF22)whereas FGFR2-IIIc (also denotedK-sam- I) binds both FGF1 and FGF2 well but does not bind the KGF family members (Miki et al., Proc. Natl. Acad. Sci. USA 89:246, 1992). Indeed, FGFR2-IIIb is the only receptor for KGF family members (Ornitz et al., 1996, op. cit.) and is therefore also designated KGFR.

[0005] The FGFRs and their isoforms are differentially expressed in various tissues. FGFR2-IIIb (and the IIIb forms of FGFR1andFGFR3) is expressed inepithelial tissues,whileFGFR2-IIIc is expressed inmesenchymal tissues (Duanetal., J.Biol.Chem.267:16076, 1992;Ornitzet al., 1996,op. cit.).Certainof theFGF ligandsof these receptorshaveanopposite pattern of expression. Thus, KGF subfamily members, including FGF7 (KGF), FGF10, and FGF22, bind only to FGFR2- IIIb (Zhang et al., op. cit.) and are expressed inmesenchymal tissues, and somay be paracrine effectors of epithelial cells (Ornitz et al., 1996, op. cit.). In contrast, the FGF4 subfamily members FGF4‑6 bind to FGFR2-IIIc and are expressed in both epithelial and mesenchymal lineages, and so may have either autocrine or paracrine functions. Because of the expression patterns of the isoforms of FGFR2 and their ligands, FGFR2 plays a role in epithelial-mesynchymal interactions (Finch et al., Dev. Dyn. 203:223, 1995), so it is not surprising that knock-out of FGFR2-IIIb in mice leads to severe embryonic defects and lethality (De Moerlooze et al., Development 127:483, 2000).

[0006] KGF (FGF7) and KGFR (FGFR2-IIIb) are overexpressed in many pancreatic cancers (Ishiwata et al., Am. J. Pathol. 153: 213, 1998), and their coexpression correlateswith poor prognosis (Choet al., Am. J. Pathol. 170:1964, 2007). Somatic mutations of the FGFR2 gene were found in 12% of a large panel of endometrial (uterine) carcinomas, and in several tested cases were required for tumor cell survival (Dutt et al., Proc. Natl. Acad. Sci. USA 105:8713, 2008). In two tumors the FGFR2mutationwas found to be the sameS252Wsubstitution associatedwith Apert syndrome. Amplification and overexpression of FGFR2 is associated with the undifferentiated, diffuse type of gastric cancer, which has a particularly poor prognosis, and inhibition of the FGFR2 activity by small molecule compounds potently inhibited proliferation of such cancer cells (Kunii et al., Cancer Res. 68:2340, 2008; Nakamura et al., Gastroenterol. 131:1530, 2006).

[0007] Inhibition of FGFR signaling has been reported to improve anti-tumor immunity and impair metastasis in breast cancer. (See, e.g., T. Ye et al., Breast Cancer Res. Treat. 143: 435‑446 (2014).) Anti-FGFR2 antibodies have also been tested in models of gastric cancer, for example. Particular anti-FGFR2 antibodies are described, for example, in U.S. Patent No. 8,101,723 B2, includingmonoclonal antibodies that bind human FGFR2-IIIb but bind lesswell or do not bind to FGFR2-IIIc and vice versa. U.S. Patent Publication No. 2015‑0050273 A1 describes certain afucosylated antibodies that 2 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 bind to FGFR2-IIIb. SUMMARY

[0008] The present disclosure includes, for example, methods of treating gastrointestinal cancer, such as gastric cancer, in a subject comprising administering to the subject a therapeutically effective amount of an anti-fibroblast growth factor receptor 2 (anti-FGFR2) and modified FOLFOX6 (mFOLFOX6) chemotherapy. In some embodiments, the anti- FGFR2 antibody is an anti-FGFR2-IIIb antibody. In some embodiments, the anti-FGFR2-IIIb antibody has one or more of the following properties: binds to FGFR2-IIIb with higher affinity than to FGFR2-IIIc or does not detectably bind to FGFR2- IIIc; inhibits bindingofFGF2 tohumanFGFR2; inhibits bindingofFGF7 tohumanFGFR2; inhibits growthof ahuman tumor in amouse tumormodel; inducesanADCCactivity; possessesenhancedADCCactivity; is afucosylated; and is capableof increasing the number of one or more of PD-L1 positive cells, NK cells, CD3+ T cells, CD4+ T cells, CD8+ T cells, and macrophages in tumor tissue in a mouse tumor model compared to a control.

[0009] In some embodiments, the anti-FGFR2-IIIb antibody comprises heavy chain and light chain variable regions, wherein the heavy chain variable region comprises: a heavy chain hypervariable region H1 (HVR-H1) comprising the aminoacid sequenceofSEQ IDNO: 6; anHVR-H2comprising theaminoacid sequenceofSEQ IDNO:7; andanHVR-H3 comprising the amino acid sequence of SEQ ID NO: 8; and the light chain variable region comprises: a light chain hypervariable region L1 (HVR-L1) comprising the amino acid sequence of SEQ ID NO: 9; HVR-L2 comprising the amino acid sequence of SEQ ID NO: 10; and HVR-L3 comprising the amino acid sequence of SEQ ID NO: 11. In some embodiments, the heavy chain variable domain of the anti-FGFR2-IIIb antibody comprises an amino acid sequence at least 95% identical to the amino acid sequence of SEQ IDNO: 4. In someembodiments, the light chain variable domain of theanti-FGFR2-IIIbantibodycomprisesanaminoacidsequenceat least 95% identical to theaminoacidsequenceofSEQ ID NO: 5. In some embodiments, the heavy chain variable domain of the anti-FGFR2-IIIb antibody comprises the amino acid sequence of SEQ ID NO: 4. In some embodiments, the light chain variable domain of the anti-FGFR2-IIIb antibody comprises the amino acid sequence of SEQ ID NO: 5. In some embodiments, the heavy chain of the anti-FGFR2-IIIb antibody comprises an amino acid sequence at least 95% identical to the amino acid sequence of SEQ IDNO: 2. In some embodiments, the anti-FGFR2-IIIb antibody comprises an amino acid sequence at least 95% identical to the amino acid sequence of SEQ IDNO: 3. In some embodiments, the heavy chain of the anti-FGFR2-IIIb antibody comprises the amino acid sequence of SEQ ID NO: 2. In some embodiments, the light chain of the anti-FGFR2-IIIb antibody comprises the amino acid sequence of SEQ ID NO: 3. In some embodiments, the anti-FGFR2-IIIb antibody is chimeric, humanized, or human. In some embodiments, the anti-FGFR2-IIIb antibody is selected from a Fab, an Fv, an scFv, a Fab’, and a (Fab’)2.

[0010] In some embodiments of the methods herein, the anti-FGFR2-IIIb antibody has one or more of the following properties: lacks a fucose at position Asn297; comprises a κ light chain constant region; comprises an IgG1 heavy chain constant region; has enhancedADCCactivity in vitro compared to an antibody having the sameamino acid sequence that is fucosylated at position Asn297; has enhanced affinity for Fc gamma RIIIA compared to an antibody having the same aminoacid sequence that is fucosylated at positionAsn297; and is capable of increasing thenumber of one ormore of PD- L1 positive cells, NK cells, CD3+ Tcells, CD4+ Tcells, CD8+ Tcells, and macrophages in tumor tissue in a mouse tumor model compared to a control.

[0011] In some embodiments of the methods herein, the subject has a gastric cancer that is locally advanced, unresectable or metastatic. In some embodiments, the gastric cancer is gastroesophageal cancer.

[0012] In some embodiments of the methods herein, the anti-FGFR2-IIIb antibody is administered at a dose of 6‑15 mg / kg, 10‑15mg / kg, 6mg / kg, 7mg / kg, 8mg / kg, 9mg / kg, 10mg / kg, 11mg / kg, 12mg / kg, 13mg / kg, 14mg / kg, or 15mg / kg. In someembodiments, the anti-FGFR2-IIIb antibody is administeredonceevery 10‑21days, onceevery 10‑15days, once every10days,onceevery11days, onceevery12days,onceevery13days,onceevery14days,onceevery15days, once every 16days, onceevery 17days, onceevery18days, onceevery 19days, onceevery 20days, or onceevery21days. In someembodiments, the anti-FGFR2-IIIb antibody is administeredat a doseof 6mg / kg, 10mg / kgor 15mg / kg,wherein the anti-FGFR2-IIIb antibody is administered once every 14 days.

[0013] In some embodiments, the anti-FGFR2-IIIb antibody is administered in a dosage regime as follows: (a) at a dose of 6‑15mg / kg,wherein the anti-FGFR2-IIIb antibody is administered onceevery 14 days; (b) at a doseof 6mg / kg,wherein the anti-FGFR2-IIIb antibody is administered once every 14 days; (c) at a dose of 10 mg / kg, wherein the anti-FGFR2-IIIb antibody is administered once every 14 days; or (d) at a dose of 15 mg / kg, wherein the anti-FGFR2-IIIb antibody is administeredonceevery14days. In someembodiments (a) theanti-FGFR2-IIIbantibody is administeredat adoseof 6‑15 mg / kg, 10‑15mg / kg, 6mg / kg, 7mg / kg, 8mg / kg, 9mg / kg, 10mg / kg, 11mg / kg, 12mg / kg, 13mg / kg, 14mg / kg, or 15mg / kg once every 11‑17 days, every 12‑16 days, every 13‑15 days, or every 14 days, and (b) at least one intervening dose of 3‑8 mg / kg, 5‑8mg / kg, 7‑8mg / kg, 3mg / kg, 4mg / kg, 5mg / kg, 6mg / kg, 7mg / kg, or 8mg / kg is administered between twodoses of (a), and wherein the dose of (b) is lower than the dose of (a). In some embodiments, (i) the dose of (a) is 10‑15 mg / kg every 13‑15 days; (ii) the dose of (a) is 15mg / kg every 13‑15 days; (iii) the dose of (b) is 5‑8mg / kg and is administered 6‑8 days after at least one dose of (a) and 6‑8 days before the subsequent dose of (a); (iv) the dose of (a) is 10‑15mg / kg every 3 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 13‑15 days and the dose of (b) is 7‑8mg / kg and is administered 6‑8 days after at least one dose of (a) and 6‑8 days before the subsequent dose of (a); (v) the dose of (a) is 15 mg / kg every 14 days and the dose of (b) is 7‑8 mg / kg and is administered 7 days after at least one dose of (a) and 7 days before the subsequent dose of (a); (vi) the dose of (a) is 15 mg / kg every 14 days and the dose of (b) is 7.5 mg / kg and is administered 7 days after at least one dose of (a) and 7 days before the subsequent dose of (a); and / or (vii) the dose of (b) is administered after the first administration of the dose of (a) in any of (i) through (vi). In some embodiments, the anti-FGFR2-IIIb antibody is administered at a dose of 15 mg / kg once every 14 days, while 6‑8 days following the first administration of the anti-FGFR2-IIIb antibody, the anti-FGFR2-IIIb antibody is further administered at a dose of 7.5 mg / kg. In some such embodiments, the anti-FGFR2-IIIb antibody is administered at a dose of 15 mg / kg once every 14 days, while 7 days following the first administration of the anti-FGFR2- IIIb antibody, the anti-FGFR2-IIIb antibody is administered at a dose of 7.5 mg / kg. In some such embodiments, the 7.5 mg / kg dose is given only one time, i.e. between the first and second 15 mg / kg administrations.

[0014] In someembodiments of themethods herein, themFOLFOX6 comprises administration of 85mg / m2 oxaliplatin, 400 mg / m2 leucovorin, and 400 mg / m2 5-fluorouracil (5-FU) by intravenous (IV) infusion or IV bolus. In some embodi- ments, the mFOLFOX6 comprises administration of 85 mg / m2 oxaliplatin, 400 mg / m2 leucovorin, and 400 mg / m2 5- fluorouracil (5-FU) by intravenous (IV) infusion or IV bolus followed by administration of 2400 mg / m2 5-FU by IV infusion over 44‑48hours. In someembodiments, themFOLFOX6 is administered onceevery 10‑21days, once every 10‑15days, onceevery10days, onceevery11days, onceevery12days, onceevery13days, onceevery14days,onceevery15days, once every 16 days, once every 17 days, once every 18 days, once every 19 days, once every 20 days, or once every 21 days. In someembodiments, themFOLFOX6 isadministeredonceevery14days. In someembodiments, themFOLFOX6 comprises administration of 85 mg / m2 oxaliplatin, 400 mg / m2 leucovorin, and 400 mg / m2 5-fluorouracil (5-FU) by intravenous (IV) infusion or IV bolus followed by administration of 2400 mg / m2 5-FU by IV infusion over 44‑48 hours, wherein the mFOLFOX6 is administered once every 14 days.

[0015] In some embodiments of the methods herein, the anti-FGFR2-IIIb antibody and the mFOLFOX6 are adminis- teredconcurrently or sequentially. In someembodiments, oneormoreadministrationsof themFOLFOX6aregivenprior to administering the anti-FGFR2-IIIb antibody. In someembodiments, two administrations of themFOLFOX6are given prior to administering theanti-FGFR2-IIIbantibody. In someembodiments, theanti-FGFR2-IIIBantibody is administeredon the same day as the mFOLFOX6 and prior to mFOLFOX6 administration.

[0016] In someembodiments, the gastric cancer haspreviously beendetermined to overexpressFGFR2-IIIb and / or the gastric cancer has previously been determined to have an FGFR2 gene amplification. In some embodiments, themethod further comprises determining whether the gastric cancer overexpresses FGFR2-IIIb and / or determining whether the gastric cancer has an FGFR2gene amplification. In someembodiments, FGFR2-IIIb overexpression is determined at the protein level by immunohistochemistry (IHC). In some embodiments, the overexpression was previously determined or is determined by an IHC signal of 3+ in at least 10%, 20%, 30%, 40%, or 50% of tumor cells. In some embodiments, FGFR2 gene amplification was previously determined or is determined by obtaining the ratio of FGFR2 to chromosome 10 centromere (CEN10) using fluorescence in situ hybridization (FISH), wherein the FGFR2 gene is considered amplified if theFGFR2 / CEN10 ratio determinedbyFISH is greater thanor equal to 2. In someembodiments, theFGFR2amplification was previously detected or is detected in circulating tumor DNA (ctDNA).

[0017] Someembodiments of the present disclosure encompassmethods of treating locally advanced, unresectable or metastatic gastric cancer in a subject comprising administering to the subject a therapeutically effective amount of an anti- fibroblast growth factor receptor 2 IIIb (anti-FGFR2-IIIb) antibody and modified FOLFOX6 (mFOLFOX6) chemotherapy, wherein the anti-FGFR2-IIIb antibody comprises heavy chain and light chain variable regions, wherein the heavy chain variable region comprises: (i) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 6; (ii) HVR-H2 comprising the amino acid sequence of SEQ ID NO: 7; and (iii) HVR-H3 comprising the amino acid sequence of SEQ ID NO: 8; and the light chain variable region comprises: (iv) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 9; (v) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 10; and (vi) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 11;

[0018] wherein the anti-FGFR2-IIIb antibody is administered intravenously at a dose of 10‑15 mg / kg followed by administration of the mFOLFOX6 comprising administration of 85 mg / m2 oxaliplatin, 400 mg / m2 leucovorin, and 400 mg / m2 5-fluorouracil (5-FU) by IV infusion or IV bolus followed by administration of 2400 mg / m2 5-FU by IV infusion over 44‑48 hours; and wherein the anti-FGFR2-IIIb and mFOLFOX6 are administered every 2 weeks. Some embodiments of the present disclosure encompass methods of treating locally advanced, unresectable or metastatic gastric cancer in a subject comprising administering to the subject a therapeutically effective amount of an anti-fibroblast growth factor receptor 2 IIIb (anti-FGFR2-IIIb) antibody and modified FOLFOX6 (mFOLFOX6) chemotherapy, wherein the anti- 4 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55

[0019] FGFR2-IIIb antibody comprises heavy chain and light chain variable regions, wherein the heavy chain variable region comprises: (i) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 6; (ii) HVR-H2 comprising the amino acid sequence of SEQ ID NO: 7; and (iii) HVR-H3 comprising the amino acid sequence of SEQ ID NO: 8; and the light chain variable region comprises: (iv) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 9; (v) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 10; and (vi) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 11; wherein theanti-FGFR2-IIIbantibodyandmFOLFOX6areadministeredevery13‑15days, andoptionallywhereinasingle dose of 3‑8 mg / kg anti-FGFR2-IIIb antibody is administered 6‑8 days after the first dose of 6‑15 mg / kg anti-FGFR2-IIIb antibody and before the second dose of 6‑15 mg / kg anti-FGFR2-IIIb antibody. In some such embodiments, (a) the anti- FGFR2-IIIb antibody is administered intravenously at a dose of 15 mg / kg, (b) the anti-FGFR2-IIIb antibody and mFOLFOX6 are administered every 14 days on the same day, and (c) a single dose of 7.5 mg / kg anti-FGFR2-IIIb antibody is administered 7days after the first doseof 15mg / kg anti-FGFR2-IIIb antibody andbefore the seconddoseof 15 mg / kg anti-FGFR2-IIIb antibody.

[0020] In some embodiments herein, the gastric cancer has previously been determined to overexpress FGFR2-IIIb as indicated by an IHC signal of 3+ in at least 10%of tumor cells and / or the gastric cancer has previously been determined to have an FGFR2 gene amplification in ctDNA. In some such embodiments, the subject received two administrations of mFOLFOX6 prior to the first administration of the anti-FGFR2-IIIb antibody.

[0021] The present disclosure also encompasses compositions comprising an anti-FGFR2-IIIb antibody as described hereinandeachof oxaliplatin, leucovorin, and5-FU, for example, for use in treatinggastrointestinal cancer, suchasgastric cancer, in a patient according to any of the above methods. In some embodiments, the compositions comprise a combination of an anti-FGFR2-IIIb antibody as described herein and at least one of oxaliplatin, leucovorin, and 5-FU. In some embodiments, the anti-FGFR2-IIIb antibody and the at least one of oxaliplatin, leucovorin, and 5-FU are in separate containers or compartments. In some such embodiments, the compositions comprise a combination of the antibodyandeachofoxaliplatin, leucovorin, and5-FU inseparate containersor compartments. In someembodiments, the compositions further comprise instructions for use in gastrointestinal cancer, e.g. gastric cancer, treatment.

[0022] In some embodiments of the methods or compositions herein, the anti-FGFR2-IIIb antibody has the heavy and light chain hypervariable region (HVR) H1, H2, H3, L1, L2, and L3 amino acid sequences of monoclonal antibodies GAL- FR21, GAL-FR22, or GAL-FR23, described in U.S. Patent No. 8,101,723 B2. In some embodiments the anti-FGFR2-IIIb antibody heavy chain variable region comprises: (i) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 6; (ii) HVR-H2 comprising the amino acid sequence of SEQ ID NO: 7; and (iii) HVR-H3 comprising the amino acid sequence of SEQ IDNO: 8; and the light chain variable region comprises: (iv) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 9; (v) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 10; and (vi) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 11.

[0023] In someembodiments, theanti-FGFR2-IIIbantibodyhasaheavychain variable domain that is at least 95%, such as at least 97%, at least 98%, or at least 99% identical to the amino acid sequence of SEQ IDNO:4, or that comprises the amino acid sequence of SEQ ID NO: 4. In some embodiments, the anti-FGFR2-IIIb antibody has a light chain variable domain that is at least 95%, suchasat least 97%,at least 98%, or at least 99% identical to the aminoacid sequenceofSEQ ID NO:5, or that comprises the amino acid sequence of SEQ ID NO: 5. In some embodiments, the heavy chain variable domain is at least 95%, such as at least 97%, at least 98%, or at least 99% identical to the amino acid sequence of SEQ ID NO:4, or that comprises theaminoacid sequenceofSEQ IDNO:4and the light chain variable domain is at least 95%, such as at least 97%, at least 98%, or at least 99% identical to the amino acid sequence of SEQ IDNO:5, or that comprises the amino acid sequence of SEQ ID NO: 5. In some embodiments, the anti-FGFR2-IIIb antibody has a heavy chain that is at least 95%, suchasat least 97%, at least 98%, or at least 99% identical to the aminoacid sequence ofSEQ IDNO: 2, or that comprises the amino acid sequence of SEQ ID NO: 2. In some embodiments, the anti-FGFR2-IIIb antibody has a light chain that is at least 95%,suchasat least 97%,at least 98%,orat least 99% identical to theaminoacidsequenceofSEQID NO:3, or that comprises theaminoacid sequenceofSEQ IDNO:3. In someembodiments, theheavy chain is at least 95%, such as at least 97%, at least 98%, or at least 99% identical to the amino acid sequence of SEQ IDNO:2, or that comprises the amino acid sequence of SEQ IDNO: 2 and the light chain is at least 95%, such as at least 97%, at least 98%, or at least 99% identical to the amino acid sequence of SEQ ID NO:3, or that comprises the amino acid sequence of SEQ ID NO: 3.

[0024] In someembodiments theanti-FGFR2-IIIbantibodyheavy chain variable regioncomprises: (i)CDR1comprising the amino acid sequence of SEQ ID NO: 16; (ii) CDR2 comprising the amino acid sequence of SEQ ID NO: 17; and (iii) CDR3 comprising the amino acid sequence of SEQ ID NO: 18; and the light chain variable region comprises: (iv) CDR1 comprising the amino acid sequence of SEQ IDNO: 20; (v) CDR2 comprising the amino acid sequence of SEQ IDNO: 21; 5 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 and (vi) CDR3 comprising the amino acid sequence of SEQ ID NO: 22.

[0025] In someembodiments, theanti-FGFR2-IIIbantibodyhasaheavychain variable domain that is at least 95%, such as at least 97%, at least 98%, or at least 99% identical to the amino acid sequence of SEQ IDNO: 15, or that comprises the amino acid sequence of SEQ ID NO: 15. In some embodiments, the anti-FGFR2-IIIb antibody has a light chain variable domain that is at least 95%, suchasat least 97%,at least 98%, or at least 99% identical to the aminoacid sequenceofSEQ IDNO: 19, or that comprises the amino acid sequence of SEQ IDNO: 19. In some embodiments, the heavy chain variable domain is at least 95%, such as at least 97%, at least 98%, or at least 99% identical to the amino acid sequence of SEQ ID NO: 15, or that comprises the amino acid sequence of SEQ ID NO: 15 and the light chain variable domain is at least 95%, such as at least 97%, at least 98%, or at least 99% identical to the amino acid sequence of SEQ ID NO: 19, or that comprises the amino acid sequence of SEQ ID NO: 19.

[0026] In some embodiments the anti-FGFR2-IIIb antibody is afucosylated. In some embodiments, the antibody lacks fucose at Asn297. In some embodiments, the anti-FGFR2-IIIb antibody comprises a kappa light chain constant region. In some embodiments, the antibody comprises an IgG1 heavy chain constant region. In some embodiments, an afucosy- lated antibody has enhanced ADCC (antibody-dependent cell cytotoxic) activity in vitro and / or in vivo compared to an antibody having the same amino acid sequence that is fucosylated at Asn297. In some embodiments, an afucosylated antibody has enhanced affinity for Fc gammaRIIIA compared to an antibody having the sameamino acid sequence that is fucosylated at position Asn297. In some embodiments, the afucosylated antibody is capable of increasing the number of oneormoreofPD-L1positive cells,NKcells,CD3+Tcells,CD4+Tcells,CD8+Tcells, andmacrophages in tumor tissue in amouse xenograft and / or syngeneic tumormodel compared to a control (e.g. as compared to a control antibody that does not target FGFR2).

[0027] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claims. The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described. All references cited herein, including patent applications and publications, are incorporated herein by reference in their entireties for any purpose. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Fig. 1 shows administration schedules for the dose escalation part I of the clinical trial described below in Example 1. The initial cohort is at dose level 1, and further enrollments will be at dose levels 1, 2, or ‑1 as shown in the figure according to analysis of the presence of dose-limiting toxicities (DLTs) as provided below in Table 2. Fig. 2provides a flow-chart showing patient assessments to beperformed for part I of the clinical trial described below in Example 1. Fig. 3showsadministrationschedules for thedoseescalation (phase1)of theclinical trial described inExample2.The initial cohorts are cohorts 1 and 2, with cohort 3 opened if needed and a further cohort 4 (not shown) also opened if needed. Further details are provided in Example 2 below. DESCRIPTION OF PARTICULAR EMBODIMENTS Definitions

[0029] Unless otherwise defined, scientific and technical terms used in connectionwith the present invention shall have the meanings that are commonly understood by those of ordinary skill in the art. Further, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular.

[0030] Exemplary techniques used in connection with recombinant DNA, oligonucleotide synthesis, tissue culture and transformation (e.g., electroporation, lipofection), enzymatic reactions, and purification techniques are known in the art. Many such techniques and procedures are described, e.g., in Sambrook et al. Molecular Cloning: A Laboratory Manual (2nd ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (1989)), among other places. In addition, exemplary techniques for chemical syntheses, chemical analyses, pharmaceutical preparation, formulation, anddelivery, and treatment of patients are also known in the art.

[0031] In this application, the use of "or" means "and / or" unless stated otherwise. In the context of amultiple dependent claim, the use of "or" refers back tomore than one preceding independent or dependent claim in the alternative only. Also, terms such as "element" or "component" encompass both elements and components comprising one unit and elements and components that comprise more than one subunit unless specifically stated otherwise.

[0032] As utilized in accordance with the present disclosure, the following terms, unless otherwise indicated, shall be understood to have the following meanings: 6 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55

[0033] The terms "nucleic acid molecule" and "polynucleotide" may be used interchangeably, and refer to a polymer of nucleotides. Such polymers of nucleotidesmay contain natural and / or non-natural nucleotides, and include, but are not limited to, DNA, RNA, and PNA. "Nucleic acid sequence" refers to the linear sequence of nucleotides that comprise the nucleic acid molecule or polynucleotide.

[0034] The terms "polypeptide" and "protein" are used interchangeably to refer to a polymer of amino acid residues, and are not limited to aminimum length. Such polymers of amino acid residuesmay contain natural or non-natural amino acid residues, and include, but are not limited to, peptides, oligopeptides, dimers, trimers, and multimers of amino acid residues. Both full-length proteins and fragments thereof are encompassed by the definition. The terms also include post- expressionmodifications of the polypeptide, for example, glycosylation, sialylation, acetylation, phosphorylation, and the like. Furthermore, for purposes of the present invention, a "polypeptide" refers to a protein that includes modifications, such as deletions, additions, and substitutions (generally conservative in nature), to the native sequence, as long as the protein maintains the desired activity. These modifications may be deliberate, as through site-directed mutagenesis, or may be accidental, such as through mutations of hosts that produce the proteins or errors due to PCR amplification.

[0035] "FGFR2" refers to human fibroblast growth factor receptor 2 including any of its alternatively spliced forms such as the IIIa, IIIb and IIIc splice forms.The termFGFR2encompasseswild-typeFGFR2andnaturally occurringmutant forms such as FGFR2 activating mutant forms such as FGFR2-S252W, which is found in some cancer cells. "FGFR2-IIIb" or "FGFR2b" areused interchangeably to refer to thehumanfibroblast growth factor receptor 2 IIIb splice form.Anexemplary human FGFR2-IIIb sequence is shown in GenBank Accession No. NP_075259.4, dated July 7, 2013. A nonlimiting exemplary mature human FGFR2-IIIb amino acid sequence is shown in SEQ ID NO: 1. "FGFR2-IIIc" or "FGFR2c" are used interchangeably to refer to the human fibroblast growth factor receptor 2 IIIc splice form. An exemplary human FGFR2-IIIc sequence is shown in GenBank Accession No. NP_000132.3, dated July 7, 2013. A nonlimiting exemplary mature FGFR2-IIIc amino acid sequence is shown in SEQ ID NO: 12.

[0036] An "FGFR2 extracellular domain" or "FGFR2 ECD" refers to an extracellular domain of human FGFR2, including natural and engineered variants thereof. An example of an FGFR2 ECD is provided in SEQ ID NOs: 13.

[0037] The term "antibody" as used herein refers to a molecule comprising at least hypervariable regions (HVRs) H1, H2, andH3 of a heavy chain and L1, L2, and L3 of a light chain, wherein themolecule is capable of binding to antigen. The term antibody includes, but is not limited to, fragments that are capable of binding antigen, such as Fv, single-chain Fv (scFv), Fab, Fab’, and (Fab’)2. The term antibody also includes, but is not limited to, chimeric antibodies, humanized antibodies, human antibodies, and antibodies of various species such asmouse, human, cynomolgusmonkey, etc. It also includes antibodies conjugated to other molecules such as small molecule drugs, bispecific antibodies and multispecific antibodies.

[0038] An "anti-FGFR2" antibody refers to an antibody that specifically binds to FGFR2. An "anti-FGFR2-IIIb" antibody or "anti-FGFR2b" antibody refers to an antibody that specifically binds to FGFR2-IIIb (aka. FGFR2b). Such an antibody has a higher affinity for FGFR2-IIIb than for other isoforms of FGFR2, such as FGFR2-IIIc. In some embodiments, the antibody may not detectably bind to FGFR2-IIIc. The terms "anti-FGFR2 antibody," "anti-FGFR2-IIIb antibody" and "anti- FGFR2b antibody" specifically include afucosylated forms of such antibodies.

[0039] The term "heavy chain variable region" refers to a region comprising heavy chain HVR1, framework (FR) 2, HVR2, FR3, and HVR3. In some embodiments, a heavy chain variable region also comprises at least a portion of an FR1 and / or at least a portion of an FR4.

[0040] The term "heavy chain constant region" refers to a region comprising at least three heavy chain constant domains, CH1, CH2, and CH3. Nonlimiting exemplary heavy chain constant regions include γ, δ, and α. Nonlimiting exemplary heavy chain constant regions also include ε and µ. Each heavy constant region corresponds to an antibody isotype. For example, an antibody comprising a γ constant region is an IgG antibody, an antibody comprising a δ constant region is an IgD antibody, and an antibody comprising an α constant region is an IgA antibody. Further, an antibody comprising a µ constant region is an IgM antibody, and an antibody comprising an ε constant region is an IgE antibody. Certain isotypes can be further subdivided into subclasses. For example, IgG antibodies include, but are not limited to, IgG1 (comprisinga γ1 constant region), IgG2 (comprisinga γ2 constant region), IgG3 (comprisinga γ3 constant region), and IgG4 (comprising a γ4 constant region) antibodies; IgA antibodies include, but are not limited to, IgA1 (comprising an α1 constant region) and IgA2 (comprisinganα2 constant region) antibodies; and IgMantibodies include, but arenot limited to, IgM1 and IgM2.

[0041] The term"heavychain" refers toapolypeptidecomprisingat least aheavychainvariable region,withorwithout a leader sequence. In someembodiments, a heavy chain comprises at least a portion of a heavy chain constant region. The term "full-length heavy chain" refers to a polypeptide comprising a heavy chain variable region anda heavy chain constant region, with or without a leader sequence.

[0042] The term "light chain variable region" refers to a region comprising light chainHVR1, framework (FR) 2,HVR2, FR3, and HVR3. In some embodiments, a light chain variable region also comprises an FR1 and / or an FR4.

[0043] The term "light chain constant region" refers to a region comprising a light chain constant domain, CL. Nonlimiting exemplary light chain constant regions include λ and κ. 7 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55

[0044] The term "light chain" refers to a polypeptide comprising at least a light chain variable region, with or without a leader sequence. Insomeembodiments, a light chain comprisesat least aportionofa light chainconstant region.The term "full-length light chain" refers toapolypeptidecomprisinga light chainvariable regionanda light chainconstant region,with or without a leader sequence.

[0045] The term "hypervariable region" or "HVR" refers to each of the regions of an antibody variable domain that are hypervariable in sequence and / or form structurally defined loops ("hypervariable loops"). Generally, native four-chain antibodies comprise six HVRs; three in the VH (H1, H2, H3), and three in the VL (L1, L2, L3). HVRs generally comprise amino acid residues from the hypervariable loops and / or from the "complementarity determining regions" (CDRs), the latter being of highest sequence variability and / or involved in antigen recognition. Exemplary hypervariable loops occur at amino acid residues 26‑32 (L1), 50‑52 (L2), 91‑96 (L3), 26‑32 (H1), 53‑55 (H2), and 96‑101 (H3). (Chothia and Lesk, J. Mol. Biol. 196:901‑917 (1987).) Exemplary CDRs (CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, andCDR-H3) occur at amino acid residues 24‑34 of L1, 50‑56 of L2, 89‑97 of L3, 31‑35B of H1, 50‑65 of H2, and 95‑102 of H3. (Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, MD (1991)). The terms hypervariable regions (HVRs) and complementarity determining regions (CDRs) both refer to portions of the variable region that form the antigen binding regions.

[0046] "Affinity" or "bindingaffinity" refers to the strengthof the sum total of noncovalent interactions betweenasingle binding site of a molecule (e.g., an antibody) and its binding partner (e.g., an antigen). In some embodiments, "binding affinity" refers to intrinsic binding affinity, which reflects a 1:1 interaction betweenmembers of a binding pair (e.g., antibody and antigen). The affinity of a molecule X for its partner Y can generally be represented by the dissociation constant (Kd).

[0047] "Antibody-dependent cell-mediated cytotoxicity" or "ADCC" refers to a formof cytotoxicity in which secreted Ig bound onto Fc receptors (FcRs) present on certain cytotoxic cells (e.g.NKcells, neutrophils, andmacrophages) enable these cytotoxic effector cells to bind specifically to an antigen-bearing target cell and subsequently kill the target cell with cytotoxins. The primary cells for mediating ADCC, NK cells, express FcγRIII only, whereas monocytes express FcγRI, FcγRII, and FcγRIII. FcR expression on hematopoietic cells is summarized in Table 3 on page 464 of Ravetch and Kinet, Annu. Rev. Immunol 9:457‑92 (1991). To assess ADCC activity of a molecule of interest, an in vitroADCC assay, such as that described in US Pat. Nos. 5,500,362 or 5,821,337 or U.S. Pat. No. 6,737,056 (Presta), may be performed. Useful effector cells for such assays include PBMC and NK cells. Alternatively, or additionally, ADCC activity of the molecule of interest may be assessed in vivo, e.g., in an animal model such as that disclosed in Clynes et al. Proc. Natl. Acad. Sci. (USA) 95:652‑656 (1998). Additional antibodieswith alteredFc region aminoacid sequencesand increasedor decreased ADCC activity are described, e.g., in U.S. Pat. No. 7,923,538, and U.S. Pat. No. 7,994,290.

[0048] Anantibodyhavingan "enhancedADCCactivity" refers toanantibody that ismoreeffectiveatmediatingADCC in vitro or in vivo compared to the parent antibody, wherein the antibody and the parent antibody differ in at least one structural aspect, andwhen the amounts of suchantibody andparent antibody used in the assay are essentially the same. In some embodiments, the antibody and the parent antibody have the same amino acid sequence, but the antibody is afucosylatedwhile theparent antibody is fucosylated. In someembodiments,ADCCactivitywill bedeterminedusing the in vitroADCCassaysuchasdisclosed inUSPublicationNo.2015‑0050273-A1, but otherassaysormethods for determining ADCC activity, e.g. in an animal model etc., are contemplated. In some embodiments, an antibody with enhanced ADCC activity also has enhanced affinity for Fc gamma RIIIA. In some embodiments, an antibody with enhanced ADCC activity has enhanced affinity for Fc gamma RIIIA (V158). In some embodiments, an antibody with enhanced ADCC activity has enhanced affinity for Fc gamma RIIIA (F158).

[0049] "Enhanced affinity for Fc gamma RIIIA" refers to an antibody that has greater affinity for Fc gammaRIIIA (also referred to, in some instances, as CD16a) than a parent antibody, wherein the antibody and the parent antibody differ in at least one structural aspect. In some embodiments, the antibody and the parent antibody have the same amino acid sequence, but the antibody is afucosylated while the parent antibody is fucosylated. Any suitable method for determining affinity for Fc gamma RIIIA may be used. In some embodiments, affinity for Fc gamma RIIIA is determined by a method described in U.S. Publication No. 2015‑0050273-A1. In some embodiments, an antibody with enhanced affinity for Fc gammaRIIIA also has enhanced ADCC activity. In some embodiments, an antibody with enhanced affinity for Fc gamma RIIIA has enhanced affinity for Fc gamma RIIIA (V158). In some embodiments, an antibody with enhanced affinity for Fc gamma RIIIA has enhanced affinity for Fc gamma RIIIA (F158).

[0050] A "chimeric antibody" as used herein refers to an antibody comprising at least one variable region from a first species (such as mouse, rat, cynomolgus monkey, etc.) and at least one constant region from a second species (such as human, cynomolgus monkey, etc.). In some embodiments, a chimeric antibody comprises at least one mouse variable region and at least one human constant region. In some embodiments, a chimeric antibody comprises at least one cynomolgus variable region and at least one human constant region. In some embodiments, a chimeric antibody comprises at least one rat variable region and at least one mouse constant region. In some embodiments, all of the variable regions of a chimeric antibody are from a first species and all of the constant regions of the chimeric antibody are from a second species.

[0051] A "humanized antibody" as used herein refers to an antibody in which at least one amino acid in a framework 8 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 regionofanon-humanvariable regionhasbeen replacedwith thecorrespondingaminoacid fromahumanvariable region. In someembodiments, a humanized antibody comprises at least one human constant region or fragment thereof. In some embodiments, a humanized antibody is a Fab, an scFv, a (Fab’)2, etc.

[0052] A "human antibody" as used herein refers to antibodies produced in humans, antibodies produced in non- humananimals that comprisehuman immunoglobulin genes, suchasXenoMouse®, andantibodies selectedusing in vitro methods, such as phage display, wherein the antibody repertoire is based on a human immunoglobulin sequences.

[0053] An "afucosylated" antibody or an antibody "lacking fucose" refers to an IgG1 or IgG3 isotype antibody that lacks fucose in its constant region glycosylation. Glycosylation of human IgG1 or IgG3 occurs at Asn297 (N297) as core fucosylated biantennary complex oligosaccharide glycosylation terminated with up to 2 Gal residues. In some embodi- ments, an afucosylated antibody lacks fucose at Asn297. These structures are designated asG0,G1 (α1,6 orα1,3) orG2 glycan residues, depending on the amount of terminalGal residues.See, e.g.,Raju, T. S., BioProcess Int. 1: 44‑53 (2003). CHO type glycosylation of antibody Fc is described, e.g., in Routier, F. H., Glycoconjugate J. 14: 201‑207 (1997).Within a population of antibodies, the antibodies are considered to be afucosylated if <5% of the antibodies of the population comprise fucose at Asn297.

[0054] "Effector functions" refer to biological activities attributable to the Fc region of an antibody, which vary with the antibody isotype. Examples of antibody effector functions include: Clq binding and complement dependent cytotoxicity (CDC); Fc receptor binding; antibody-dependent cell-mediated cytotoxicity (ADCC); phagocytosis; down regulationof cell surface receptors (e.g. B cell receptor); and B cell activation.

[0055] With reference toanti-FGFR2antibodies, the terms "blocksbindingof" or "inhibitsbindingof" a ligand refer to the ability to inhibit an interaction betweenFGFR2andanFGFR2 ligand, such as human fibroblast growth factor 1 (FGF1) or FGF2. Such inhibition may occur through any mechanism, including direct interference with ligand binding, e.g., because of overlapping binding sites on FGFR2, and / or conformational changes in FGFR2 induced by an antibody that alter ligand affinity, or, e.g., in the case of an FGFR2 ECD or FGFR2 ECD fusion molecule, by competing for binding to FGFR2 ligands.

[0056] The term "isolated" as used herein refers to a molecule that has been separated from at least some of the components with which it is typically found in nature. For example, a polypeptide is referred to as "isolated" when it is separated fromat least some of the components of the cell in which it was produced.Where a polypeptide is secreted by a cell after expression, physically separating the supernatant containing the polypeptide from the cell that produced it is considered to be "isolating" the polypeptide. Similarly, a polynucleotide is referred to as "isolated" when it is not part of the larger polynucleotide (such as, for example, genomic DNA or mitochondrial DNA, in the case of a DNA polynucleotide) in which it is typically found in nature, or is separated from at least some of the components of the cell in which it was produced, e.g., in the caseof anRNApolynucleotide. Thus, aDNApolynucleotide that is contained in avector insideahost cell may be referred to as "isolated" so long as that polynucleotide is not found in that vector in nature.

[0057] The term "elevated level" means a higher level of a protein in a particular tissue of a subject relative to the same tissue in a control, such as an individual or individuals who are not suffering from cancer or other condition described herein. The elevated level may be the result of any mechanism, such as increased expression, increased stability, decreased degradation, increased secretion, decreased clearance, etc., of the protein.

[0058] The terms "reduce" or "reduces" or "increase" or "increases" with respect to a protein or cell type means to change the level of that protein or cell type in a particular tissue of a subject, such as in a tumor, by at least 10%. In some embodiments, an agent, such as an anti-FGFR2 antibody, increases or reduces the level of a protein or a cell type in a particular tissueofasubject, suchasa tumor, byat least 15%,at least 20%,at least 25%,at least 30%,at least 35%,at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, or at least 90% relative to the level prior to contact with the antibody.

[0059] The terms "subject" and "patient" are used interchangeably herein to refer to a human. In some embodiments, methods of treating other mammals, including, but not limited to, rodents, simians, felines, canines, equines, bovines, porcines, ovines, caprines, mammalian laboratory animals, mammalian farm animals, mammalian sport animals, and mammalian pets, are also provided.

[0060] The term "sample," asusedherein, refers toacomposition that is obtainedorderived fromasubject that contains a cellular and / or other molecular entity that is to be characterized, quantitated, and / or identified, for example based on physical, biochemical, chemical and / or physiological characteristics. An exemplary sample is a tissue sample.

[0061] The term "cancer" refers to a malignant proliferative disorder associated with uncontrolled cell proliferation, unrestrained cell growth, and decreased cell death via apoptosis. The term "gastrointestinal cancer" or "GI cancer" refers to a cancer of the gastrointestinal tract such as gastric cancer, colorectal cancer, or pancreatic adenocarcinoma. In some embodiments, the gastrointestinal cancer is "gastric cancer" or "GC," which, as used herein, includes gastro- esophageal cancer.

[0062] In some embodiments, a cancer comprises an FGFR2 gene amplification, whereas in some embodiments the cancer does not comprise an FGFR2 amplification. In some embodiments, where an amplification occurs, the FGFR2 amplification comprises an FGFR2:CEN10 (chromosome 10 centromere) ratio of >3. In some embodiments, FGFR2 9 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 amplification comprises an FGFR2:CEN10 ratio of ≥ 2. In other embodiments, however, the FGFR2 level comprises an FGFR2:CEN10 ratio of between 1 and 2, indicating that FGFR2 is not amplified. In some embodiments, mutations or translocations may cause an FGFR2 gene amplification.

[0063] FGFR2 gene amplification may be determined using a fluorescence in situ hybridization assay (FISH), for example. FGFR2 gene amplification may also be detected by a blood-based assay, or "liquid biopsy." In some embodi- ments of a blood-based assay, FGFR2geneamplificationmaybedetected inDNA fromcirculating tumor cells, or "CTCs." Methods for detection and molecular characterization of CTCs are described, e.g., in Alix-Panabieres (2013) Clinical Chemistry 59:1110‑118. In some embodiments of a blood based assay, FGFR2 gene amplification is detected in ctDNA. The term "ctDNA" refers to "circulating tumor DNA," which is tumor-derived fragmented DNA in the bloodstream that is not associatedwith cells. Methods for detection andmolecular characterization of ctDNA are described, e.g., in Han et al. (2017) Genomics, Proteomics & Bioinformatics 15:2 59‑72, and include PCR-based methods and next-generation sequencing (NGS).

[0064] In someembodiments, thecanceroverexpressesFGFR2-IIIb. In someembodiments, the canceroverexpresses FGFR2-IIIb to a greater extent thanFGFR2-IIIc. In someembodiments, the cancer expresses FGFR2-IIIb at a normalized level that ismore than 2-fold, 3-fold, 5-fold, or 10-fold greater than the normalized level of FGFR2-IIIc expression. In some embodiments, a cancer overexpresses FGFR2-IIIb but does not comprise a FGFR2 gene amplification, while in other embodiments, the cancer comprises an FGFR2 gene amplification and also overexpresses FGFR2-IIIb. Expression of FGFR2-IIIbmay be determined at the protein level by immunohistochemistry (IHC), for example, of tumor samples froma patient with comparison to normal tissue. The terms "FGFR2-IIIb protein overexpression" and "FGFR2-IIIb overexpres- sion" and the likemeanelevated levels ofFGFR2-IIIb protein, regardless of the causeof suchelevated levels (i.e.,whether the elevated levels are a result of increased translation and / or decreased degradation of protein, other mechanism, or a combination of mechanisms). In some embodiments, FGFR2-IIIb overexpression may be detected at the mRNA level using, for example, techniques such as reverse-transcriptase polymerase chain reaction (RT-PCR) analysis compared to noncancerous tissue.

[0065] The level of FGFR2or FGFR2-IIIb expression by IHCmay be determined by giving a tumor sample an IHC score ona scale of 0‑3.Herein, a score of "0" is given if no reactivity is observed or if there ismembranous reactivity only in <10% of tumor cells; a score of "1+" is given if there is faint or barely perceptible membranous reactivity in at least 10% of tumor cells or if the cells are reactive only in a part of their membranes; a score of "2+" is given if there is weak to moderate complete, basolateral or lateral membranous reactivity in at least 10%of tumor cells; and a score of "3+" is given if there is strong complete basolateral or lateralmembranous reactivity in at least 10%of tumor cells. In someembodiments, 1+, 2+, or3+stainingof tumorcells by IHC indicatesFGFR2-IIIboverexpression. In someembodiments, 2+or3+stainingof tumor cells by IHC indicates FGFR2-IIIb overexpression. In some embodiments, 3+ staining of tumor cells by IHC indicates FGFR2-IIIb overexpression.

[0066] A "modified FOLFOX6" or "mFOLFOX6" chemotherapy regimen refers to a regimen in which a combination of oxaliplatin (e.g. Eloxatin®), leucovorin (e.g. leucovorin calcium or folinic acid), and 5-fluorouracil (5-FU) are each administered to a human patient by IV infusion or IV bolus over the course of about 2‑8 hours and in which a further infusion of 5-FU is then administered by IV infusion over an about 2 day period, as provided in various embodiments described herein.

[0067] "Treatment," as used herein, refers to therapeutic treatment, for example, wherein the object is to reduce in severity or slowprogressionof the targetedpathologic conditionor disorder aswell as, for example,wherein theobject is to inhibit recurrence of the condition or disorder. In certain embodiments, the term "treatment" covers any administration or application of a therapeutic for disease in a patient, and includes inhibiting or slowing the disease or progression of the disease; partially or fully relieving the disease, for example, by causing regression, or restoring or repairing a lost,missing, or defective function; stimulating an inefficient process; or causing the disease plateau to have reduced severity. The term "treatment" also includes reducing the severity of any phenotypic characteristic and / or reducing the incidence, degree, or likelihoodof that characteristic. Those inneedof treatment include thosealreadywith thedisorder aswell as thoseat risk of recurrence of the disorder or those in whom a recurrence of the disorder is to be prevented or slowed down.

[0068] The term "effective amount" or "therapeutically effective amount" refers to an amount of a drug effective to treat a disease or disorder in a subject. In certain embodiments, an effective amount refers to an amount effective, at dosages and for periods of time necessary, to achieve the desired therapeutic or prophylactic result. A therapeutically effective amount of an anti-FGFR2 antibody and chemotherapy regimen of the invention may vary according to factors such as the disease state, age, sex, and weight of the individual, and the ability of the antibody or antibodies to elicit a desired response in the individual. A therapeutically effective amount encompasses an amount in which any toxic or detrimental effects of the antibody or antibodies are outweighed by the therapeutically beneficial effects. In some embodiments, theexpression "effectiveamount" refers toanamount of theantibody that is effective for treating thecancer.

[0069] Administration "in combinationwith" oneormore further therapeutic agents, suchasa chemotherapy regimen, includes simultaneous (concurrent) and consecutive (sequential) administration in any order.

[0070] A "pharmaceutically acceptable carrier" refers to a non-toxic solid, semisolid, or liquid filler, diluent, en- 10 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 capsulating material, formulation auxiliary, or carrier conventional in the art for use with a therapeutic agent that together comprise a "pharmaceutical composition" for administration to a subject. A pharmaceutically acceptable carrier is non- toxic to recipients at the dosagesandconcentrations employedand is compatiblewith other ingredients of the formulation. Thepharmaceutically acceptable carrier is appropriate for the formulationemployed. For example, if the therapeutic agent is to beadministeredorally, the carriermay beagel capsule. If the therapeutic agent is to beadministered subcutaneously, the carrier ideally is not irritable to the skin and does not cause injection site reaction.

[0071] Additional definitions may be provided in the sections that follow. Exemplary Anti-FGFR2 Antibodies

[0072] Exemplary anti-FGFR2 antibodies include antibodies that specifically bind FGFR2-IIIb, i.e., anti-FGFR2-IIIb antibodies. In some embodiments, the anti-FGFR2-IIIb antibodies bind FGFR2-IIIc with lower affinity than they bind to FGFR2-IIIb. In some embodiments, the anti-FGFR2-IIIb antibodies do not detectably bind to FGFR2-IIIc.

[0073] An exemplary anti-FGFR2-IIIb antibody for use in the embodiments herein is the HuGAL-FR21 antibody described in U.S. Patent No. 8,101,723 B2, issued January 24, 2012, which is specifically incorporated herein by reference.

[0074] Figures 13 and 14 of U.S. Patent No. 8,101,723 B2 show the amino acid sequences of the variable regions and full-length mature antibody chains of HuGAL-FR21, and are incorporated by reference herein. The heavy chain variable region sequences of antibody HuGAL-FR21, are underlined in Figure 13 of U.S. Patent No. 8,101,723 B2, and are specifically incorporated by reference herein. In someembodiments, the antibody is afucosylated. In someembodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297. Additional antibodies that may be used in the embodiments herein include those described in US Patent Publication No. 2015‑0050273-A1, which describes certain afucosylated anti-FGFR2-IIIb antibodies, and which is incorporated by reference herein.

[0075] In some embodiments, the anti-FGFR2-IIIb antibody comprises at least one, two, three, four, five, or six hypervariable regions (HVRs; e.g., CDRs) selected from (a) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 6; (b) HVR-H2 comprising the amino acid sequence of SEQ ID NO: 7; (c) HVR-H3 comprising the amino acid sequence of SEQ IDNO: 8; (d) HVR-L1 comprising the amino acid sequence of SEQ IDNO: 9; (e) HVR-L2 comprising the amino acid sequence of SEQ IDNO: 10; and (f) HVR-L3 comprising the amino acid sequence of SEQ IDNO: 11. In some embodiments, the antibody is afucosylated. In some embodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0076] In some embodiments, the anti-FGFR2-IIIb antibody comprises a heavy chain variable region and a light chain variable region. In some embodiments, the anti-FGFR2-IIIb antibody comprises at least one heavy chain comprising a heavychainvariable regionandat least aportionof aheavychain constant region, andat least one light chain comprisinga light chain variable regionandat least a portionof a light chain constant region. In someembodiments, theanti-FGFR2-IIIb antibody comprises two heavy chains, wherein each heavy chain comprises a heavy chain variable region and at least a portion of a heavy chain constant region, and two light chains, wherein each light chain comprises a light chain variable region and at least a portion of a light chain constant region. In some embodiments, the anti-FGFR2-IIIb antibody comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 4 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 5. In some embodiments, the anti-FGFR2-IIIb antibody comprisesaheavy chain comprising theaminoacid sequenceofSEQ IDNO:2anda light chain comprising theaminoacid sequence of SEQ IDNO: 3. In someembodiments, the antibody is afucosylated. In someembodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0077] In someembodiments, theanti-FGFR2-IIIbantibodycomprisessixHVRscomprising (a)HVR-H1comprising the amino acid sequence of SEQ ID NO: 6; (b) HVR-H2 comprising the amino acid sequence of SEQ ID NO: 7; (c) HVR-H3 comprising the amino acid sequence of SEQ IDNO: 8; (d) HVR-L1 comprising the amino acid sequence of SEQ IDNO: 9; (e)HVR-L2comprising theaminoacidsequenceofSEQIDNO:10;and (f)HVR-L3comprising theaminoacidsequenceof SEQ ID NO: 11. In some embodiments, the anti-FGFR2-IIIb antibody comprises the six HVRs as described above and binds to FGFR2-IIIb. In some embodiments, the anti-FGFR-IIIb antibody does not bind to FGFR2-IIIc. In some embodi- ments, the antibody is afucosylated. In some embodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0078] In one aspect, the anti-FGFR2-IIIb antibody competes with an anti-FGFR2-IIIb antibody comprising six HVRs comprising (a) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 6; (b) HVR-H2 comprising the amino acid sequence of SEQ IDNO: 7; (c) HVR-H3 comprising the amino acid sequence of SEQ IDNO: 8; (d)HVR-L1 comprising the aminoacid sequenceofSEQ IDNO:9; (e)HVR-L2comprising theaminoacid sequenceofSEQ IDNO:10; and (f)HVR-L3 comprising the amino acid sequence of SEQ ID NO: 11. In some embodiments, the antibody is afucosylated. In some embodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0079] In some embodiments, the anti-FGFR2-IIIb antibody comprises at least one, at least two, or all three VH HVR sequences selected from (a) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 6; (b) HVR-H2 comprising the 11 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 amino acid sequence of SEQ ID NO: 7; and (c) HVR-H3 comprising the amino acid sequence of SEQ ID NO: 8. In some embodiments, the antibody is afucosylated. In some embodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0080] In some embodiments, the anti-FGFR2-IIIb antibody comprising at least one, at least two, or all three VL HVR sequences selected from (a) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 9; (b) HVR-L2 comprising the amino acid sequence of SEQ IDNO: 10; and (c) HVR-L3 comprising the amino acid sequence of SEQ IDNO: 11. In some embodiments, the antibody is afucosylated. In some embodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0081] In someembodiments, the anti-FGFR2-IIIb antibody comprises (a) aVHdomain comprising at least one, at least two, or all three VH HVR sequences selected from (i) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 6, (ii) HVR-H2 comprising the amino acid sequence of SEQ ID NO: 7, and (iii) HVR-H3 comprising an amino acid sequence selected from SEQ ID NO: 8; and (b) a VL domain comprising at least one, at least two, or all three VL HVR sequences selected from (i) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 9, (ii) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 10, and (c) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 11. In some embodiments, the antibody is afucosylated. In some embodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0082] In some embodiments, the anti-FGFR2-IIIb antibody comprises a heavy chain variable domain (VH) sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the amino acid sequence of SEQ ID NO: 4. In certain embodiments, a VH sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%,97%,98%,or 99% identity contains substitutions (e.g., conservative substitutions), insertions, or deletions relative to the reference sequence, but an anti-FGFR2-IIIb antibody comprising that sequence retains the ability to bind to FGFR2- IIIb. In certain embodiments, such an anti-FGFR2-IIIb antibody retains the ability to selectively bind to FGFR2-IIIb without detectably binding to FGFR2-IIIc. In certain embodiments, a total of 1 to 10 amino acids have been substituted, inserted and / or deleted inSEQ IDNO: 4. In certain embodiments, substitutions, insertions, or deletionsoccur in regions outside the HVRs (i.e., in the FRs). Optionally, the anti-FGFR2-IIIb antibody comprises the VH sequence in SEQ ID NO: 5, including post-translational modifications of that sequence. In a particular embodiment, the VH comprises one, two or three HVRs selected from: (a) HVR-H1 comprising the amino acid sequence of SEQ IDNO: 6; (b) HVR-H2 comprising the amino acid sequenceofSEQ IDNO:7; and (c)HVR-H3comprising theaminoacid sequenceofSEQ IDNO:8. In someembodiments, the antibody is afucosylated. In someembodiments, the antibody is an IgG1or IgG3antibody that lacks fucose at Asn297.

[0083] In someembodiments, the anti-FGFR2-IIIb antibody comprises a light chain variable domain (VL) havingat least 90%,91%,92%,93%,94%,95%,96%,97%,98%,99%,or 100%sequence identity to theaminoacid sequenceofSEQ ID NO: 5. In certain embodiments, a VL sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identity contains substitutions (e.g., conservative substitutions), insertions, or deletions relative to the reference se- quence, but an anti-FGFR2-IIIb antibody comprising that sequence retains the ability to bind to FGFR2-IIIb. In certain embodiments, the anti-FGFR2-IIIb antibody retains the ability to selectively bind to FGFR2-IIIbwithout binding to FGFR2- IIIc. In certain embodiments, a total of 1 to 10 amino acids have been substituted, inserted and / or deleted inSEQ IDNO: 5. In certain embodiments, the substitutions, insertions, or deletions occur in regions outside the HVRs (i.e., in the FRs). Optionally, the anti-FGFR2-IIIb antibody comprises the VL sequence in SEQ ID NO: 4, including post-translational modifications of that sequence. In a particular embodiment, the VL comprises one, two or three HVRs selected from (a) HVR-L1comprising theaminoacidsequenceofSEQIDNO:9; (b)HVR-L2comprising theaminoacidsequenceofSEQID NO: 10; and (c) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 11. In some embodiments, the antibody is afucosylated. In some embodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0084] In some embodiments, the anti-FGFR2-IIIb antibody comprises a heavy chain variable domain (VH) sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the amino acid sequence of SEQ IDNO: 4 and a light chain variable domain (VL) having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the amino acid sequence of SEQ ID NO: 5. In certain embodiments, a VH sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identity contains substitutions (e.g., conservative substitutions), insertions, or deletions relative to the reference sequence, and aVL sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identity contains substitutions (e.g., conservative substitu- tions), insertions, or deletions relative to the reference sequence, but an anti-FGFR2-IIIb antibody comprising that sequence retains the ability to bind to FGFR2-IIIb. In certain embodiments, such an anti-FGFR2-IIIb antibody retains the ability to selectivelybind toFGFR2-IIIbwithoutbinding toFGFR2-IIIc. In certainembodiments, a total of 1 to10aminoacids havebeensubstituted, insertedand / ordeleted inSEQIDNO:4. In certainembodiments, a total of 1 to10aminoacidshave been substituted, inserted and / or deleted in SEQ IDNO: 5. In certain embodiments, substitutions, insertions, or deletions occur in regions outside the HVRs (i.e., in the FRs). Optionally, the anti-FGFR2-IIIb antibody comprises the VH sequence inSEQ IDNO:4and theVLsequenceofSEQ IDNO:5, includingpost-translationalmodificationsof oneor both sequence. In a particular embodiment, the VH comprises one, two or three HVRs selected from: (a) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 6; (b) HVR-H2 comprising the amino acid sequence of SEQ ID NO: 7; and (c) HVR-H3 12 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 comprising the amino acid sequence of SEQ ID NO: 8; and the VL comprises one, two or three HVRs selected from (a) HVR-L1comprising theaminoacidsequenceofSEQIDNO:9; (b)HVR-L2comprising theaminoacidsequenceofSEQID NO: 10; and (c) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 11. In some embodiments, the antibody is afucosylated. In some embodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0085] In some embodiments, the anti-FGFR2-IIIb antibody a VH as in any of the embodiments provided above, and a VLas inanyof theembodimentsprovidedabove. Inoneembodiment, theantibodycomprises theVHandVLsequences in SEQ ID NO: 4 and SEQ ID NO: 5, respectively, including post-translational modifications of those sequences. In some embodiments, the antibody is afucosylated. In some embodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0086] In some embodiments, the anti-FGFR2-IIIb antibody comprises a heavy chain sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%sequence identity to the amino acid sequence of SEQ IDNO: 2. In certain embodiments, a heavy chain sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identity contains substitutions (e.g., conservative substitutions), insertions, or deletions relative to the reference sequence, but an anti-FGFR2-IIIb antibody comprising that sequence retains the ability to bind to FGFR2-IIIb. In certain embodiments, such an anti-FGFR2-IIIb antibody retains the ability to selectively bind to FGFR2-IIIb without detectably binding to FGFR2-IIIc. In certain embodiments, a total of 1 to 10 amino acids have been substituted, inserted and / or deleted inSEQ IDNO: 2. In certain embodiments, substitutions, insertions, or deletions occur in regions outside theHVRs (i.e., in the FRs). Optionally, the anti-FGFR2-IIIb antibody heavy chain comprises the VH sequence in SEQ ID NO: 2, including post-translational modifications of that sequence. In a particular embodiment, the heavy chain comprises one, two or three HVRs selected from: (a) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 6; (b) HVR-H2 comprising the amino acid sequence of SEQ ID NO: 7; and (c) HVR-H3 comprising the amino acid sequence of SEQ ID NO: 8. In some embodiments, the antibody is afucosylated. In some embodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0087] In some embodiments the anti-FGFR2-IIIb antibody comprises a light chain having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%sequence identity to the aminoacid sequenceofSEQ IDNO: 3. In certain embodiments, a light chain sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identity contains substitutions (e.g., conservative substitutions), insertions, or deletions relative to the reference sequence, but an anti-FGFR2-IIIb antibody comprising that sequence retains theability to bind toFGFR2-IIIb. In certain embodiments, such an anti-FGFR2-IIIb antibody retains the ability to selectively bind to FGFR2-IIIb without detectably binding to FGFR2-IIIc. In certain embodiments, a total of 1 to 10 amino acids have been substituted, inserted and / or deleted in SEQ ID NO: 3. In certain embodiments, the substitutions, insertions, or deletions occur in regions outside the HVRs (i.e., in the FRs). Optionally, the anti-FGFR2-IIIb antibody light chain comprises the VL sequence in SEQ ID NO: 3, including post- translational modifications of that sequence. In a particular embodiment, the light chain comprises one, two or three HVRs selected from (a) HVR-L1 comprising the amino acid sequence of SEQ IDNO: 9; (b) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 10; and (c) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 11. In some embodiments, the antibody is afucosylated. In some embodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0088] In some embodiments, the anti-FGFR2-IIIb antibody comprises a heavy chain sequence having at least 90%, 91%,92%,93%,94%,95%,96%,97%,98%,99%,or100%sequence identity to theaminoacidsequenceofSEQIDNO:2 and a light chain sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the amino acid sequence of SEQ ID NO: 3. In certain embodiments, a heavy chain sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identity contains substitutions (e.g., conservative substitu- tions), insertions, or deletions relative to the reference sequence, but an anti-FGFR2-IIIb antibody comprising that sequence retains the ability to bind to FGFR2-IIIb. In certain embodiments, such an anti-FGFR2-IIIb antibody retains the ability to selectively bind to FGFR2-IIIb without detectably binding to FGFR2-IIIc. In certain embodiments, a light chain sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identity contains substitutions (e.g., conservative substitutions), insertions, or deletions relative to the reference sequence, but an anti-FGFR2-IIIb antibody comprising that sequence retains the ability to bind to FGFR2-IIIb. In certain embodiments, such an FGFR2-IIIb antibody retains the ability to selectively bind to FGFR2-IIIb without detectably binding to FGFR2-IIIc. In certain embodiments, a total of 1 to 10aminoacidshavebeensubstituted, inserted and / or deleted inSEQ IDNO:2. In certain embodiments, a total of 1 to 10 amino acids have been substituted, inserted and / or deleted in SEQ ID NO: 3. In certain embodiments, substitutions, insertions, or deletions occur in regions outside the HVRs (i.e., in the FRs). Optionally, the anti-FGFR2-IIIb antibody heavy chain comprises the VH sequence in SEQ ID NO: 2, including post-translational modifications of that sequence and the anti-FGFR2-IIIb antibody light chain comprises the VL sequence in SEQ ID NO: 3, including post- translational modifications of that sequence. In a particular embodiment, the heavy chain comprises one, two or three HVRsselected from: (a)HVR-H1comprising theaminoacid sequenceofSEQ IDNO:6; (b)HVR-H2comprising theamino acid sequenceofSEQ IDNO:7; and (c)HVR-H3 comprising theaminoacid sequenceofSEQ IDNO: 8; and the light chain comprises one, two or three HVRs selected from (a) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 9; (b) 13 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 HVR-L2 comprising the amino acid sequence of SEQ ID NO: 10; and (c) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 11. In some embodiments, the antibody is afucosylated. In some embodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0089] Additional exemplary anti-FGFR2 antibodies are the GAL-FR22 and GAL-FR23 antibodies described in U.S. Patent No., 8,101,723 B2, incorporated by reference herein. The light and heavy chain variable regions of GAL-FR22, for example, are provided asSEQ IDNOs: 7 and8 inPatentNo., 8,101,723B2,while theKabatCDRsand the light andheavy chain variable regions are also provided in Figure 16 of that patent, which are incorporated by reference herein. TheGAL- FR21, GAL-FR22 and GAL-FR23 producing hybridomas are deposited at the American Type Culture Collection, PO Box 1549,ManassasVA,USA,20108, asATCCNumbers9586, 9587, and9408, onNovember 6,November6, andAugust 12, 2008, respectively. Thus, in someembodiments, the FGFR2antibody is an antibody comprising the amino acid sequence of an antibody obtained from one of those three hybridoma strains.

[0090] The heavy and light chain variable regions of GAL-FR22 are also presented herein as SEQ ID NOs: 39 and 43, while the Kabat CDRs are presented herein as SEQ ID NOs: 40‑42 and 44‑46. Thus, in some embodiments the anti- FGFR2-IIIb antibodyheavychain variable regioncomprises: (i)CDR1comprising theaminoacid sequenceofSEQ IDNO: 40; (ii) CDR2 comprising the amino acid sequence of SEQ IDNO: 41; and (iii) CDR3 comprising the amino acid sequence ofSEQ IDNO:42; and the light chain variable region comprises: (iv)CDR1comprising theaminoacid sequenceofSEQ ID NO: 44; (v) CDR2 comprising the amino acid sequence of SEQ ID NO: 45; and (vi) CDR3 comprising the amino acid sequence of SEQ ID NO: 46.

[0091] In some embodiments, the anti-FGFR2 antibody comprises an anti-FGFR2-IIIb antibody in which the heavy chain variable domain that is at least 95%, such as at least 97%, at least 98%, or at least 99% identical to the amino acid sequenceofSEQ IDNO:39, or that comprises theaminoacid sequenceofSEQ IDNO:39. In someembodiments, theanti- FGFR2antibodycomprisesananti-FGFR2-IIIbantibody inwhich the light chain variabledomain is at least 95%,suchasat least 97%,at least98%,orat least 99% identical to theaminoacidsequenceofSEQIDNO:43,or that comprises theamino acid sequence of SEQ IDNO: 43. In someembodiments, the heavy chain variable domain is at least 95%, such as at least 97%, at least 98%, or at least 99% identical to the aminoacid sequenceofSEQ IDNO:39, or that comprises theaminoacid sequence of SEQ ID NO: 39 and the light chain variable domain is at least 95%, such as at least 97%, at least 98%, or at least 99% identical to the amino acid sequence of SEQ ID NO:43, or that comprises the amino acid sequence of SEQ ID NO: 43. In some embodiments, the antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0092] In any of the methods described herein, the anti-FGFR2 antibody may be a humanized antibody, chimeric antibody, or human antibody. In any of the compositions or methods described herein, the anti-FGFR2 antibody may be selected fromaFab, anFv, anscFv, aFab’, anda (Fab’)2. Inanyof the compositionsormethodsdescribedherein, theanti- FGFR2antibodymaybeselected froman IgA,an IgG,andan IgD. Inanyof thecompositionsormethodsdescribedherein, the anti-FGFR2 antibody may be an IgG. In any of the methods described herein, the antibody may be an IgG1 or IgG3. Exemplary Properties of Antibodies

[0093] In some embodiments, the anti-FGFR2-IIIb antibody binds to FGFR2-IIIb with higher affinity than to FGFR2-IIIc or does not detectably bind to FGFR2-IIIc; inhibits binding of FGF2 to human FGFR2; and / or inhibits binding of FGF7 to human FGFR2. Binding of antibody to FGFR2 and inhibition of binding between FGFR2 and FGFs can be assessed, for example, byELISAassays, as described inUSPat. No. 8,101,723, or, for example, by a chip-based assay as described in Example 2 ofWO2015 / ‑17600. In someembodiments, the antibody induces anADCCactivity, and in someembodiments possesses enhanced ADCC activity, for example, as described in WO 2015 / ‑17600. ADCC activity, for example, may be determined as described in Example 3 of WO 2015 / ‑17600. In some embodiments, the antibody may inhibit growth of a human tumor in a mouse model, for example, as shown in Example 1 of International Application No. PCT / US2016 / 063332. In some embodiments, the anti-FGFR2-IIIb antibody is capable of increasing the number of oneormoreofPD-L1positive cells,NKcells,CD3+Tcells,CD4+Tcells,CD8+Tcells, andmacrophages in tumor tissue in a mouse tumor model compared to a control, for example, as described in Example 2 of International Application No. PCT / US2016 / 063332. Afucosylated Anti-FGFR2 Antibodies

[0094] In some embodiments, anti-FGFR2 antibodies, for example the anti-FGFR2-IIIb antibodies as described above, have a carbohydrate structure that lacks fucose attached (directly or indirectly) to an Fc region (i.e., afucosylated antibodies), i.e,, the antibodies are afucosylated. In some embodiments, the afucosylated antibody is an IgG1 or IgG3 antibody that lacks fucose at Asn297.

[0095] Herein, antibodies are considered to be afucosylatedwhen a plurality of such antibodies comprises at least 95% afucosylated antibodies. The amount of fucosemay bedetermined by calculating the average amount of fucosewithin the sugar chain at Asn297 relative to the sum of all glycostructures attached to Asn 297 (e.g., complex, hybrid and high 14 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 mannose structures). Nonlimiting exemplary methods of detecting fucose in an antibody include MALDI-TOF mass spectrometry (see, e.g.,WO2008 / 077546),HPLCmeasurement of released fluorescently labeledoligosaccharides (see, e.g., Schneider et al., "N-Glycan analysis of monoclonal antibodies and other glycoproteins using UHPLC with fluores- cence detection," Agilent Technologies, Inc. (2012); Lines, J. Pharm. Biomed. Analysis, 14: 601‑608 (1996); Takahasi, J. Chrom., 720: 217‑225 (1996)), capillary electrophoresismeasurement of released fluorescently labeled oligosaccharides (see, e.g., Ma et al., Anal. Chem., 71: 5185‑5192 (1999)), and HPLC with pulsed amperometric detection to measure monosaccharide composition (see, e.g., Hardy, et al., Analytical Biochem., 170: 54‑62 (1988)).

[0096] Asn297 refers to theasparagine residue locatedataboutposition297 in theFc region (EUnumberingofFc region residues); however, in a given antibody sequence, Asn297 may also be located about ± 3 amino acids upstream or downstream of position 297, i.e., between positions 294 and 300, due to minor sequence variations in antibodies. In an anti-FGFR2-IIIbantibodydescribedherein,Asn297 is found in thesequenceQYNST(positions292‑296ofSEQIDNO:2), and is in bold and underlined in the Table of Sequences shown below, SEQ ID NO: 2.

[0097] Fucosylation variants may have improved ADCC function. See, e.g., US Patent Publication Nos. US 2003 / 0157108 (Presta, L.); US 2004 / 0093621 (Kyowa Hakko Kogyo Co., Ltd). Examples of publications related to "afucosylated" or "fucose-deficient" antibodies include: US 2003 / 0157108; WO 2000 / 61739; WO 2001 / 29246; US 2003 / 0115614; US 2002 / 0164328; US 2004 / 0093621; US 2004 / 0132140; US 2004 / 0110704; US 2004 / 0110282; US 2004 / 0109865; WO 2003 / 085119; WO 2003 / 084570; WO 2005 / 035586; WO 2005 / 035778; WO2005 / 053742; WO2002 / 031140; Okazaki et al. J. Mol. Biol. 336:1239‑1249 (2004); Yamane-Ohnuki et al. Biotech. Bioeng. 87: 614 (2004). Examples of cell lines capable of producing afucosylated antibodies include Lec13 CHO cells deficient in protein fucosylation (Ripka et al. Arch. Biochem. Biophys. 249:533‑545 (1986); USPatent Application No. US 2003 / 0157108 A1, Presta, L; and WO 2004 / 056312 A1, Adams et al., especially at Example 11), and knockout cell lines, such as cell lines lacking a functional alpha‑1,6-fucosyltransferase gene, FUT8, e.g., knockout CHO cells (see, e.g.,Yamane-Ohnuki et al. Biotech. Bioeng. 87: 614 (2004); Kanda, Y. et al., Biotechnol. Bioeng., 94(4):680‑688 (2006); and WO2003 / 085107).

[0098] Anti-FGFR2 antibodies herein may also have bisected oligosaccharides, e.g., in which a biantennary oligo- saccharide attached to the Fc region of the antibody is bisected by GlcNAc. Such antibodies may have reduced fucosylation and / or improved ADCC function. Examples of such antibodies are described, e.g., in WO 2003 / 011878 (Jean-Mairet et al.); US Patent No. 6,602,684 (Umana et al.); and US 2005 / 0123546 (Umana et al.). In some embodi- ments, anti-FGFR2 antibodies have at least one galactose residue in the oligosaccharide attached to the Fc region. Such antibodies may have improved CDC function. Such antibodies are described, e.g., in WO 1997 / 30087 (Patel et al.); WO 1998 / 58964 (Raju, S.); and WO 1999 / 22764 (Raju, S.).

[0099] In someembodiments of the invention, anafucosylated anti-FGFR2antibodymediatesADCC in the presence of human effector cells more effectively than an antibody with the same amino acid sequence that comprises fucose. Generally, ADCC activity may be determined using the in vitro ADCC assay disclosed in U.S. Patent Publication No. 2015‑0050273 A1, but other assays or methods for determining ADCC activity, e.g. in an animal model etc., are contemplated.

[0100] In someembodiments, theanti-FGFR2antibody comprises theheavyand light chain sequencesofSEQ IDNOs: 2 and 3. In some embodiments, the antibody comprising the heavy and light chain sequences of SEQ ID NOs: 2 and 3 is afucosylated. Exemplary Antibody Constant Regions

[0101] In some embodiments, an anti-FGFR2 described herein comprises one or more human constant regions. In some embodiments, the human heavy chain constant region is of an isotype selected from IgA, IgG, and IgD. In some embodiments, the human light chain constant region is of an isotype selected from κ and λ.

[0102] In some embodiments, an antibody described herein comprises a human IgG constant region. In some embodiments, when effector function is desirable, an antibody comprising a human IgG1 heavy chain constant region or a human IgG3heavy chain constant region is selected. In someembodiments, an antibody described herein comprises a human IgG1 constant region. In some embodiments, an antibody described herein comprises a human IgG1 constant region, wherein N297 is not fucosylated. In some embodiments, an antibody described herein comprises a human IgG1 constant region and a human κ light chain.

[0103] Throughout the present specification and claims unless explicitly stated or known to one skilled in the art, the numbering of the residues in an immunoglobulin heavy chain is that of the EU index as in Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991), expressly incorporatedherein by reference. The "EU indexas inKabat" refers to the residuenumberingof the human IgG1 EU antibody.

[0104] In certain embodiments, an antibody of the invention comprises a variant Fc region has at least one amino acid substitution compared to the Fc region of a wild-type IgG or a wild-type antibody. In certain embodiments, the variant Fc region has two or more amino acid substitutions in the Fc region of the wild-type antibody. In certain embodiments, the 15 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 variant Fc region has three or more amino acid substitutions in the Fc region of the wild-type antibody. In certain embodiments, the variant Fc region has at least one, two or three or more Fc region amino acid substitutions described herein. In certain embodiments, the variant Fc region herein will possess at least about 80% homology with a native sequenceFc region and / or with an Fc region of a parent antibody. In certain embodiments, the variant Fc region hereinwill possess at least about 90% homology with a native sequence Fc region and / or with an Fc region of a parent antibody. In certain embodiments, the variant Fc region herein will possess at least about 95% homology with a native sequence Fc region and / or with an Fc region of a parent antibody.

[0105] In certain embodiments, an antibody provided herein is altered to increase or decrease the extent to which the antibody is glycosylated. Addition or deletion of glycosylation sites to an antibody may be conveniently accomplished by altering the amino acid sequence such that one or more glycosylation sites is created or removed.

[0106] Where theantibodycomprisesanFc region, thecarbohydrateattached theretomaybealtered.Nativeantibodies producedbymammalian cells typically comprise abranched, biantennary oligosaccharide that is generally attachedbyan N-linkage to Asn297 of the CH2 domain of the Fc region. See, e.g., Wright et al. TIBTECH 15:26‑32 (1997). The oligosaccharidemay includevariouscarbohydrates,e.g.,mannose,N-acetyl glucosamine (GlcNAc), galactose, andsialic acid, as well as a fucose attached to a GlcNAc in the "stem" of the biantennary oligosaccharide structure. In some embodiments, modifications of the oligosaccharide in an antibody of the invention may be made in order to create antibodies with certain improved properties.

[0107] Antibodies may also have amino-terminal leader extensions. For example, one or more amino acid residues of the amino-terminal leader sequence are present at the amino-terminus of any one or more heavy or light chains of an antibody. An exemplary amino-terminal leader extension comprises or consists of three amino acid residues, VHS, present on one or both light chains of an antibody.

[0108] The in vivoor serumhalf-life of humanFcRnhighaffinity bindingpolypeptides canbeassayed,e.g., in transgenic mice, in humans, or in non-human primates to which the polypeptideswith a variant Fc region are administered.See also, e.g., Petkova et al. International Immunology 18(12):1759‑1769 (2006). Exemplary chimeric antibodies

[0109] In certain embodiments, an anti-FGFR2 antibody provided herein is a chimeric antibody. Certain chimeric antibodies are described, e.g., in U.S. Patent No. 4,816,567; and Morrison et al., (1984) Proc. Natl. Acad. Sci. USA, 81: 6851‑6855 (1984)). In one example, a chimeric antibody comprises a non-human variable region (e.g., a variable region derived from amouse, rat, hamster, rabbit, or non-human primate, such as a monkey) and a human constant region. In a further example, a chimeric antibody is a "class switched" antibody in which the class or subclass has been changed from that of the parent antibody. Chimeric antibodies include antigen-binding fragments thereof.

[0110] Nonlimiting exemplary chimeric antibodies include chimeric antibodies against FGFR2 comprising heavy chain HVR1, HVR2, and HVR3, and / or light chain HVR1, HVR2, and HVR3 sequences described herein.

[0111] In some embodiments, a chimeric antibody described herein comprises one ormore human constant regions. In some embodiments, the human heavy chain constant region is of an isotype selected from IgA, IgG, and IgD. In some embodiments, the human light chain constant region is of an isotype selected from κ and λ. In some embodiments, a chimeric antibody described herein comprises a human IgG constant region. In some embodiments, a chimeric antibody described herein comprises a human IgG4 heavy chain constant region. In some embodiments, a chimeric antibody described herein comprises a human IgG4 constant region and a human κ light chain.

[0112] As noted above, whether or not effector function is desirable may depend on the particular method of treatment intended for an antibody. Thus, in someembodiments, when effector function is desirable, a chimeric antibody comprising a human IgG1 heavy chain constant region or a human IgG3 heavy chain constant region is selected. In some embodiments, when effector function is not desirable, a chimeric antibody comprising a human IgG4 or IgG2 heavy chain constant region is selected. In some embodiments, a chimeric antibody described herein comprises a human IgG1 constant region wherein N297 is not fucosylated. In some embodiments, a chimeric antibody described herein comprises a human IgG1 constant region and a human κ light chain. Exemplary humanized antibodies

[0113] In some embodiments, humanized antibodies that bind FGFR2 are used. Humanized antibodies are useful as therapeutic molecules because humanized antibodies reduce or eliminate the human immune response to non-human antibodies (such as the human anti-mouse antibody (HAMA) response), which can result in an immune response to an antibody therapeutic, and decreased effectiveness of the therapeutic.

[0114] In certain embodiments, a chimeric antibody is a humanized antibody. Typically, a non-human antibody is humanized to reduce immunogenicity to humans, while retaining the specificity and affinity of the parental non-human antibody.Generally, a humanized antibody comprises one ormore variable domains in whichHVRs orCDRs, (or portions 16 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 thereof) are derived from a non-human antibody, and FRs (or portions thereof) are derived from human antibody sequences. A humanized antibody optionally will also comprise at least a portion of a human constant region. In some embodiments, someFR residues in ahumanizedantibodyare substitutedwith corresponding residues fromanon-human antibody (e.g., the antibody from which the HVR residues are derived), e.g., to restore or improve antibody specificity or affinity.

[0115] Humanized antibodies andmethods of making them are reviewed, e.g., in Almagro and Fransson, (2008) Front. Biosci. 13: 1619‑1633, and are further described, e.g., in Riechmann et al., (1988) Nature 332:323‑329; Queen et al., (1989) Proc. Natl Acad. Sci. USA 86: 10029‑10033; US Patent Nos. 5, 821,337, 7,527,791, 6,982,321, and 7,087,409; Kashmiri et al., (2005) Methods 36:25‑34 (describing SDR (a-CDR) grafting); Padlan, (1991) Mol. Immunol. 28:489‑498 (describing "resurfacing"); Dall’Acqua et al., (2005) Methods 36:43‑60 (describing "FR shuffling"); and Osbourn et al., (2005)Methods 36:61‑68 and Klimka et al., (2000) Br. J. Cancer, 83:252‑260 (describing the "guided selection" approach to FR shuffling).

[0116] Human framework regions that may be used for humanization include but are not limited to: framework regions selected using the "best-fit" method (see, e.g.,Sims et al. (1993) J. Immunol. 151: 2296); framework regions derived from the consensus sequence of human antibodies of a particular subgroup of light or heavy chain variable regions (see, e.g., Carter et al. (1992) Proc. Natl. Acad. Sci. USA, 89:4285; and Presta et al. (1993) J. Immunol, 151:2623); human mature (somaticallymutated) framework regions or humangermline framework regions (see,e.g.,AlmagroandFransson, (2008) Front. Biosci. 13:1619‑1633); and framework regions derived from screening FR libraries (see, e.g.,Baca et al., (1997) J. Biol. Chem. 272: 10678‑10684 and Rosok et al., (1996) J. Biol. Chem. 271: 22611‑22618).

[0117] In some embodiments, humanized antibodies comprise one or more human constant regions. In some embodiments, the human heavy chain constant region is of an isotype selected from IgA, IgG, and IgD. In some embodiments, the human light chain constant region is of an isotype selected from κ and λ.

[0118] In someembodiments, ahumanizedantibodydescribedherein comprisesahuman IgGconstant region. In some embodiments, when effector function is desirable, the antibody comprises a human IgG1heavy chain constant region or a human IgG3 heavy chain constant region. In some embodiments, a humanized antibody described herein comprises a human IgG1 constant region. In some embodiments, a humanized antibody described herein comprises a human IgG1 constant region wherein N297 is not fucosylated. In some embodiments, a humanized antibody described herein comprises a human IgG1 constant region and a human κ light chain. Human Antibodies

[0119] Human anti-FGFR2 antibodies can be made by any suitable method. Nonlimiting exemplary methods include making human antibodies in transgenicmice that comprise human immunoglobulin loci. See, e.g., Jakobovits et al., Proc. Natl. Acad. Sci. USA 90: 2551‑55 (1993); Jakobovits et al., Nature 362: 255‑8 (1993); Lonberg et al., Nature 368: 856‑9 (1994); and U.S. Patent Nos. 5,545,807; 6,713,610; 6,673,986; 6,162,963; 5,545,807; 6,300,129; 6,255,458; 5,877,397; 5,874,299; and 5,545,806.

[0120] Nonlimiting exemplary methods also include making human antibodies using phage display libraries. See, e.g., Hoogenboomet al., J. Mol. Biol. 227: 381‑8 (1992);Marks et al., J.Mol. Biol. 222: 581‑97 (1991); andPCTPublicationNo. WO 99 / 10494.

[0121] In some embodiments, a human antibody comprises one or more human constant regions. In some embodi- ments, the humanheavy chain constant region is of an isotype selected from IgA, IgG, and IgD. In someembodiments, the human light chain constant region is of an isotype selected from κ and λ. In some embodiments, a human antibody described herein comprises a human IgG constant region. In some embodiments, a human antibody described herein comprises a human IgG4 heavy chain constant region. In some such embodiments, a human antibody described herein comprises an S241P mutation in the human IgG4 constant region. In some embodiments, a human antibody described herein comprises a human IgG4 constant region and a human κ light chain.

[0122] In some embodiments, when effector function is desirable, a human antibody comprising a human IgG1 heavy chain constant region or a human IgG3 heavy chain constant region is selected. In some embodiments, when effector function is not desirable, a human antibody comprising a human IgG4 or IgG2 heavy chain constant region is selected. In some embodiments, a humanized antibody described herein comprises a human IgG1 constant region wherein N297 is not fucosylated. In someembodiments, a humanizedantibody described herein comprises ahuman IgG1constant region and a human κ light chain. Exemplary Antibody Conjugates

[0123] In someembodiments, an anti-FGFR2antibody is conjugated to a label and / or a cytotoxic agent. As usedherein, a label is a moiety that facilitates detection of the antibody and / or facilitates detection of a molecule to which the antibody binds. Nonlimiting exemplary labels include, but are not limited to, radioisotopes, fluorescent groups, enzymatic groups, 17 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 chemiluminescent groups, biotin, epitope tags, metal-binding tags, etc. One skilled in the art can select a suitable label according to the intended application.

[0124] Asusedherein, a cytotoxic agent is amoiety that reduces theproliferative capacity of oneormore cells. A cell has reduced proliferative capacity when the cell becomes less able to proliferate, for example, because the cell undergoes apoptosis or otherwise dies, the cell fails to proceed through the cell cycle and / or fails to divide, the cell differentiates, etc. Nonlimiting exemplary cytotoxic agents include, but are not limited to, radioisotopes, toxins, and chemotherapeutic agents. One skilled in the art can select a suitable cytotoxic according to the intended application.

[0125] In some embodiments, a label and / or a cytotoxic agent is conjugated to an antibody using chemical methods in vitro.Nonlimiting exemplary chemical methods of conjugation are known in the art, and include services, methods and / or reagents commercially available from, e.g., Thermo Scientific Life Science Research Produces (formerly Pierce; Rock- ford, IL), Prozyme (Hayward, CA), SACRI Antibody Services (Calgary, Canada), AbDSerotec (Raleigh, NC), etc. In some embodiments,whena label and / or cytotoxic agent is apolypeptide, the label and / or cytotoxic agent canbeexpressed from the sameexpression vectorwith at least oneantibody chain to produceapolypeptide comprising the label and / or cytotoxic agent fused to anantibody chain.Oneskilled in theart can select a suitablemethod for conjugating a label and / or cytotoxic agent to an antibody according to the intended application. Nucleic Acid Molecules Encoding Antibodies

[0126] Nucleic acidmolecules comprising polynucleotides that encode one ormore chains of an antibody are provided. In some embodiments, a nucleic acid molecule comprises a polynucleotide that encodes a heavy chain or a light chain of an antibody. In some embodiments, a nucleic acid molecule comprises both a polynucleotide that encodes a heavy chain and a polynucleotide that encodes a light chain, of an antibody. In some embodiments, a first nucleic acid molecule comprises a first polynucleotide that encodes a heavy chain and a second nucleic acid molecule comprises a second polynucleotide that encodes a light chain.

[0127] In somesuchembodiments, theheavychain and the light chainareexpressed fromonenucleic acidmolecule, or from twoseparatenucleicacidmolecules, as twoseparatepolypeptides. In someembodiments, suchaswhenanantibody is an scFv, a single polynucleotide encodes a single polypeptide comprising both a heavy chain and a light chain linked together.

[0128] In some embodiments, a polynucleotide encoding a heavy chain or light chain of an antibody comprises a nucleotide sequence that encodes a leader sequence, which, when translated, is located at the N terminus of the heavy chain or light chain. As discussed above, the leader sequencemay be the native heavy or light chain leader sequence, or may be another heterologous leader sequence.

[0129] Nucleic acid moleculesmay be constructed using recombinant DNA techniques conventional in the art. In some embodiments, a nucleic acid molecule is an expression vector that is suitable for expression in a selected host cell. Antibody Expression and Production Vectors

[0130] Vectors comprising polynucleotides that encodeantibody heavy chains and / or light chains are provided. Vectors comprising polynucleotides that encode antibody heavy chains and / or light chains are also provided. Such vectors include, but are not limited to, DNA vectors, phage vectors, viral vectors, retroviral vectors, etc. In some embodiments, a vector comprises a first polynucleotide sequence encoding a heavy chain and a second polynucleotide sequence encoding a light chain. In some embodiments, the heavy chain and light chain are expressed from the vector as two separate polypeptides. In some embodiments, the heavy chain and light chain are expressed as part of a single polypeptide, such as, for example, when the antibody is an scFv.

[0131] In someembodiments, a first vector comprises apolynucleotide that encodes a heavy chain anda second vector comprises a polynucleotide that encodes a light chain. In some embodiments, the first vector and second vector are transfected into host cells in similar amounts (such as similar molar amounts or similar mass amounts). In some embodiments, a mole‑ or mass-ratio of between 5:1 and 1:5 of the first vector and the second vector is transfected into host cells. In some embodiments, a mass ratio of between 1:1 and 1:5 for the vector encoding the heavy chain and the vector encoding the light chain is used. In some embodiments, amass ratio of 1:2 for the vector encoding the heavy chain and the vector encoding the light chain is used.

[0132] In some embodiments, a vector is selected that is optimized for expression of polypeptides in CHO or CHO- derived cells, or in NSO cells. Exemplary such vectors are described, e.g., in Running Deer et al., Biotechnol. Prog. 20:880‑889 (2004).

[0133] In some embodiments, a vector is chosen for in vivo expression of antibody heavy chains and / or antibody light chains in animals, including humans. In some such embodiments, expression of the polypeptide is under the control of a 18 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 promoter that functions in a tissue-specific manner. For example, liver-specific promoters are described, e.g., in PCT Publication No. WO 2006 / 076288. Host Cells

[0134] In various embodiments, antibody heavy chains and / or light chains may be expressed in prokaryotic cells, such as bacterial cells; or in eukaryotic cells, such as fungal cells (such as yeast), plant cells, insect cells, andmammalian cells. Such expression may be carried out, for example, according to procedures known in the art. Exemplary eukaryotic cells that may be used to express polypeptides include, but are not limited to, COS cells, including COS 7 cells; 293 cells, including 293‑6E cells; CHO cells, including CHO-S and DG44 cells; PER.C6® cells (Crucell); and NSO cells. In some embodiments, antibody heavy chains and / or light chains may be expressed in yeast. See, e.g., U.S. Publication No. US 2006 / 0270045 A1. In some embodiments, a particular eukaryotic host cell is selected based on its ability to make desired post-translational modifications to the antibody heavy chains and / or light chains. For example, in some embodiments, CHO cells produce polypeptides that have a higher level of sialylation than the same polypeptide produced in 293 cells.

[0135] Introduction of one or more nucleic acids into a desired host cell may be accomplished by anymethod, including but not limited to, calcium phosphate transfection, DEAE-dextranmediated transfection, cationic lipid-mediated transfec- tion, electroporation, transduction, infection, etc. Nonlimiting exemplary methods are described, e.g., in Sambrook et al., Molecular Cloning, A Laboratory Manual, 3rd ed. Cold Spring Harbor Laboratory Press (2001). Nucleic acids may be transiently or stably transfected in the desired host cells, according to any suitable method.

[0136] In someembodiments, oneormorepolypeptidesmaybeproduced in vivo in ananimal that hasbeenengineered or transfected with one or more nucleic acid molecules encoding the polypeptides, according to any suitable method. Purification of Antibodies

[0137] Antibodiesmaybepurifiedbyanysuitablemethod.Suchmethods include, but arenot limited to, theuseof affinity matrices or hydrophobic interaction chromatography. Suitable affinity ligands include the antigen and ligands that bind antibody constant regions. For example, aProtein A, ProteinG, ProteinA / G, or an antibody affinity columnmay beused to bind the constant region and to purify an antibody.Hydrophobic interactive chromatography, for example, a butyl or phenyl column, may also suitable for purifying some polypeptides. Many methods of purifying polypeptides are known in the art. Cell-free Production of Antibodies

[0138] In some embodiments, an antibody is produced in a cell-free system. Nonlimiting exemplary cell-free systems are described, e.g., in Sitaraman et al., Methods Mol. Biol. 498: 229‑44 (2009); Spirin, Trends Biotechnol. 22: 538‑45

[0139] (2004); Endo et al., Biotechnol. Adv. 21: 695‑713 (2003). Modified FOLFOX6

[0140] The chemotherapy regimen modified FOLFOX6 (mFOLFOX6) comprises a regimen in which a combination of oxaliplatin (e.g. Eloxatin®), leucovorin (e.g. leucovorin calcium or folinic acid), and 5-fluorouracil (5-FU) are each administered intravenously in succession over about a 2-day total period. Modified FOLFOX6 has been used as a first line treatment for advanced gastric cancer. A randomized Phase 3 trial comparing mFOLFOX6 with 5-FU / LV / cisplatin (FLP) in the treatment of 220 patients with gastric cancer reported a statistically insignificant improved time-to-progres- sion; however, mFOLFOX6 was associated with meaningful reductions in Grade 3 / 4 adverse events, including neu- tropenia, anemia, and peripheral neuropathy. (Al-Batran et al., J. Clin. Oncol. 26: 1435‑42 (2008).) Subsequent studies have confirmed the safety and efficacy ofmFOLFOX6 in advanced gastric cancer. (B. Keam,BMCCancer, 8: 148 (2008).)

[0141] In some embodiments, a combination of oxaliplatin (e.g. Eloxatin®), leucovorin (e.g. leucovorin calcium or folinic acid), and 5-fluorouracil (5-FU) are each administered by IV infusion or IV bolus over the course of about 2‑8 hours and a further infusion of 5-FU is then administered by IV infusion over an about 44‑48-hour period. In some embodiments, the mFOLFOX6 regimen comprises: oxaliplatin administered on day 1 at 50‑100mg / m2 by IV, for example, over 2 hours, then leucovorin administered on day 1 at 100‑400mg / m2 by IV, for example, over 2 hours, then 5-FU administered at 100‑400 mg / m2 by IV bolus or IV infusion, all on day 1, and followed by further 5-FU IV infusion of 2000‑2500 mg / m2 over 44‑48 hours, such as 46 hours. In someembodiments, themFOLFOX6 regimen comprises: oxaliplatin administered on day 1 at 75‑100 mg / m2 by IV, for example, over 2 hours, then leucovorin administered on day 1 at 200‑400 mg / m2 by IV, for example, over 2 hours, then 5-FU administered at 200‑400mg / m2 by IV bolus or IV infusion, all on day 1, and followed by further 5-FU IV infusion of 2200‑2400mg / m2 over 44‑48 hours, such as 46 hours. In someembodiments, themFOLFOX6 regimen comprises: oxaliplatin administered on day 1 at 75‑90 mg / m2 by IV, for example, over 2 hours, then leucovorin administered on day 1at 300‑400mg / m2 by IV, for example, over 2 hours, then 5-FUadministered at 300‑400mg / m2 by IV 19 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 bolusor IV infusion, all onday1, and followedby further 5-FU IV infusionof 2200‑2400mg / m2over44‑48hours, suchas46 hours.

[0142] In someembodiments, themFOLFOX6 regimen comprises: oxaliplatin administered on day 1at 85mg / m2 by IV, for example, over 2 hours, then leucovorin administered on day 1 at 400mg / m2 by IV, for example, over 2 hours, then 5-FU administered at 400mg / m2 by IV bolus or IV infusion, all on day 1, and followed by further 5-FU IV infusion of 2400mg / m2 over 44‑48hours, suchas46hours. For example, a starting dose formFOLFOX6as first line gastric cancer treatmentmay include 85 mg / m2 of oxaliplatin, 350 mg of calcium folinate (folinic acid), a 400-mg / m2 dose of fluorouracil, followed by a 2400-mg / m2 dose of fluorouracil infused over 46 hours.

[0143] In some embodiments, the mFOLFOX6 regimen may be administered once every 10 to 21 days, such as once every 10‑15 days, once every 10 days, once every 11 days, once every 12 days, once every 13 days, once every 14 days, onceevery15days,onceevery16days,onceevery17days,onceevery18days,onceevery19days,onceevery20days, or once every 21 days.

[0144] In someembodiments, themFOLFOX6maybeadministeredonceevery "2weeks,"which, asused in thecontext of a general dosage regime herein, means once every 14 days plus or minus 3 days, or once every 11‑17 days. Therapeutic Compositions and Methods Methods of Treating Cancer

[0145] In some embodiments, methods for treating cancer are provided, comprising administering an effective amount of an anti-FGFR2 antibody, such as an anti-FGFR2-IIIb antibody as described herein, in combination with a modified FOLFOX6chemotherapy regimen (mFOLFOX6). In someembodiments, the cancer is a gastrointestinal (GI) cancer such as gastric cancer, colorectal cancer, and pancreatic adenocarcinoma. In some embodiments, the cancer is unresectable, locally advanced, or metastatic gastric cancer.

[0146] In some embodiments of the methods, the anti-FGFR2-IIIb antibody is administered at a dose of 6‑15 mg / kg, 10‑15mg / kg,6mg / kg,7mg / kg,8mg / kg,9mg / kg,10mg / kg,11mg / kg,12mg / kg,13mg / kg,14mg / kg,or 15mg / kg. In some embodiments, theanti-FGFR2-IIIb antibody is administeredonceevery 7‑21days, onceevery 7‑15days, onceevery 7‑10 days, once every 10‑14 days, once every 11‑17 days, once every 12‑16 days, once every 13‑15 days, once every 7 days, once every 8 days, once every 9 days, once every 10 days, once every 11 days, once every 12 days, once every 13 days, onceevery14days,onceevery15days,onceevery16days,onceevery17days,onceevery18days,onceevery19days, once every 20 days, or once every 21 days. In some embodiments, the anti-FGFR2-IIIb antibody may be administered once every 2 weeks, meaning once every 14 days plus or minus 3 days, or once every 11‑17 days.

[0147] In some embodiments, the anti-FGFR2-IIIb antibody is administered in a dosage regime of 6‑15 mg / kg every 2 weeks. In someembodiments, theanti-FGFR2-IIIbantibody isadministered inadosage regimeof 6‑15mg / kgevery13‑15 days. In some embodiments, the anti-FGFR2-IIIb antibody is administered in a dosage regime of 6‑15 mg / kg every 14 days. In someembodiments, theanti-FGFR2-IIIbantibody is administered in adosage regimeof 6, 10, or 15mg / kgevery2 weeks. In someembodiments, theanti-FGFR2-IIIbantibody isadministered inadosage regimeof 6, 10, or 15mg / kgevery 13‑15 days. In some embodiments, the anti-FGFR2-IIIb antibody is administered in a dosage regime of 6, 10, or 15mg / kg every 14 days.

[0148] In some embodiments, a dosage regime is used in which two doses are administered 2 weeks apart, and an intervening booster dose is administered at a time in between those two doses, wherein the intervening booster dose is lower than the two doses. Dosing in such a regime may help to maintain the antibody in circulation at a reasonable or relatively steady concentration over time. For example, if the concentration of antibody in circulation following a dose falls to a trough about a week after administration, then giving a lower booster dose at or near that trough point followed by another regular dose about a week after the booster dose can help to steady the overall concentration of antibody in circulation over time and prevent the concentration from falling too low in between doses.

[0149] Accordingly, in some embodiments, the anti-FGFR2-IIIb antibody is administered in a dosage regime of 6‑15 mg / kg every 2weeks, and an intervening booster dose,which is at a lower dose than the 6‑15mg / kg dose, is administered 1week (meaning7plusorminus2daysor5‑9days)after thefirst of two6‑15mg / kgdosesand1week (i.e. 5‑9days)before the second of the two 6‑15 mg / kg doses. In some such embodiments, the booster dose is 3‑8 mg / kg. In some embodiments, the booster dose is half the dose of the immediately preceding and following doses. In someembodiments, the anti-FGFR2-IIIb antibody is administered in a dosage regime of 6‑15mg / kg every 2 weeks and an intervening booster doseof 3‑8mg / kg isadministered6‑8daysafter thefirst of two6‑15mg / kgdosesand6‑8daysbefore the secondof the two 6‑15mg / kgdoses. Insomeembodiments, theanti-FGFR2-IIIbantibody isadministered inadosage regimeof10‑15mg / kg every 2 weeks and an intervening booster dose of 5‑8 mg / kg is administered 6‑8 days after the first of two 10‑15 mg / kg doses and6‑8 days before the secondof the two10‑15mg / kg doses. In someembodiments, the anti-FGFR2-IIIb antibody is administered in a dosage regime of 15 mg / kg every 2 weeks and an intervening booster dose of 7‑8 mg / kg is administered 6‑8 days after the first of two 15 mg / kg doses and 6‑8 days before the second of the two 15 mg / kg doses. 20 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 In someembodiments, theanti-FGFR2-IIIb antibody is administered inadosage regimeof 15mg / kgevery13‑15daysand an intervening booster doseof 7‑8mg / kg is administered6‑8days after the first of two15mg / kg dosesand6‑8days before the second of the two 15 mg / kg doses. In some embodiments, the anti-FGFR2-IIIb antibody is administered in a dosage regime of 15 mg / kg every 14 days and an intervening booster dose of 7‑8mg / kg is administered 6‑8 days after the first of two 15 mg / kg doses and 6‑8 days before the second of the two 15mg / kg doses. In some embodiments, the anti-FGFR2- IIIb antibody is administered in adosage regimeof 15mg / kgevery 14daysandan interveningbooster doseof 7‑8mg / kg is administered 7 days after the first of two15mg / kg doses and 7 days before the secondof the two 15mg / kg doses. In some of the above embodiments, the booster dose is given only once, e.g. only between the first and second dose admin- istrations of the antibody to the patient. In other embodiments, it is given only twice, e.g. between the first and second and the second and third dose administrations of the antibody.

[0150] In some embodiments, the anti-FGFR2-IIIb antibody is administered in a dosage regime of 15 mg / kg every 14 days and an intervening booster dose of 7.5mg / kg is administered 7 days after the first of two 15mg / kg doses and 7 days before the second of the two 15 mg / kg doses. In some embodiments, the anti-FGFR2-IIIb antibody is administered at a dose of 15mg / kg once every 14 days, starting on day 1, and 7 days following the first administration of the anti-FGFR2-IIIb antibody (i.e. on day 8), the anti-FGFR2-IIIb antibody is administered at a booster dose of 7.5 mg / kg. In some such embodiments, the booster dose of 7.5 mg / kg is given only once, e.g. between the first and second 15 mg / kg antibody administrations only.

[0151] The anti-FGFR2-IIIb antibody and themFOLFOX6may be administered concurrently, such as on the same day, for example with the antibody being infused by IV prior to the start of the mFOLFOX6 regimen, or they may be dosed sequentially, such as on different days. In some embodiments, the mFOLFOX6 is administered at least once or at least twice prior to beginning treatment with the anti-FGFR2-IIIb antibody. In some embodiments, both the antibody and the mFOLFOX6areadministeredonceevery 7‑21days, onceevery 7‑15days, onceevery 7‑10days, onceevery 10‑14days, once every 11‑17 days, once every 12‑16 days, once every 13‑15 days, once every 7 days, once every 8 days, once every 9 days, once every 10 days, once every 11 days, once every 12 days, once every 13 days, once every 14 days, once every 15 days, once every 16 days, once every 17 days, once every 18 days, once every 19 days, once every 20 days, or once every 21days. In someembodiments, the anti-FGFR2-IIIb and themFOLFOX6maybeadministeredonceevery 2weeks, meaning once every 14 days plus or minus 3 days, or once every 11‑17 days.

[0152] In some embodiments, the anti-FGFR2-IIIb antibody comprises heavy chain and light chain variable regions, wherein the heavy chain variable region comprises: (i) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 6; (ii) HVR-H2 comprising the amino acid sequence of SEQ ID NO: 7; and (iii) HVR-H3 comprising the amino acid sequence of SEQ ID NO: 8; and the light chain variable region comprises: (iv) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 9; (v) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 10; and (vi) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 11; and the anti-FGFR2-IIIb antibody is administered intravenously at a dose of 10‑15mg / kg followed by administration of the mFOLFOX6 comprising administration of 85 mg / m2 oxaliplatin, 400 mg / m2 leucovorin, and 400 mg / m2 5-fluorouracil (5- FU) by IV infusion or IV bolus followed by administration of 2400mg / m2 5-FUby IV infusion over 44‑48 hours; and the anti- FGFR2-IIIb and mFOLFOX6 are administered every 2 weeks,

[0153] In some embodiments, the subject has gastric cancer comprising an FGFR2 gene amplification, whereas in some embodiments the cancer does not comprise an FGFR2 amplification. In some embodiments, fluorescence in situ hybridization (FISH) is used to assess gene amplification, such as with probes to the FGFR2 gene locus and the chromosome 10 centromere. In some embodiments, where an amplification occurs, the FGFR2 amplification comprises an FGFR2:CEN10 (chromosome 10 centromere) ratio of >3. In some embodiments, FGFR2 amplification comprises an FGFR2:CEN10 ratio of ≥ 2. In other embodiments, however, the FGFR2 level comprises an FGFR2:CEN10 ratio of between 1 and 2, indicating that FGFR2 is not amplified.

[0154] In someembodiments, the subject has gastric cancer overexpressing FGFR2, or overexpressing FGFR2-IIIb. In some embodiments, the cancer overexpresses FGFR2-IIIb to a greater extent than FGFR2-IIIc. In some embodiments, the cancer does not comprise a gene amplification, yet FGFR2-IIIb is overexpressed, while in other embodiments the cancer comprises both an FGFR2gene amplification and overexpression of FGFR2-IIIb. In someembodiments, a cancer comprising FGFR2 amplification expresses FGFR2-IIIb at a normalized level that ismore than 2-fold, 3-fold, 5-fold, or 10- fold greater than the normalized level of FGFR2-IIIc expression. In some embodiments, the expression levels are normalized to GUSB. In some embodiments, overexpression is mRNA overexpression. In some embodiments, over- expression is protein overexpression. In some embodiments, a point mutation or translocation may cause an over- expression of FGFR2. 21 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55

[0155] In some embodiments, FGFR2 or FGFR2-IIIb overexpression is determined by immunohistochemistry (IHC). Forexample, theoverexpressionmaybedeterminedbyan IHCsignal of 1+, 2+, or3+ inat least 10%of tumorcells, suchas in at least 20%, 30%, 40%, or 50% of tumor cells. For example, in some such embodiments, patients to be treated may have, for instance, an IHC signal for FGFR2-IIIb of 2+ or 3+ in at least 10%of tumor cells (e.g. in cell membranes). In some embodiments, a patient may have 3+ signal in at least 10% of tumor cells. In some embodiments, a patient may have at least 1+ signal in at least 10% of tumor cells.

[0156] In someembodiments, theFGFR2or FGFR2-IIIb overexpressionmaybe reported asan "Hscore." Todetermine anHscore, firstmembrane staining intensitymaybedetermined for cells in a fixed field, suchas via IHC to obtain scores of 0, 1+, 2+, or 3+ and theHscore canbecalculatedusing the formula as follows: 1x(%of cells visualizedwith IHC intensity of 1+)+2x(%of cells visualizedwith IHC intensityof 2+)+3x(%of cells visualizedwith IHC intensity of 3+). Theoretically, anH score may range from 0 to 300 and equals 300 if all of the cells in the visual field have IHC staining of 3+. In some embodiments, the patient to be treatedhasastartingHscore for FGFR2, suchasFGFR2-IIIb, of > 20, suchas>30, > 40, > 50, or >100, or a rangeof 20‑300, 20‑100, 20‑50, 20‑40, or 20‑30. In someembodiments, thepatient hasanHscoreof >10 or iswithina rangeof 10‑20or15‑20. Inother embodiments, thepatient hasanHscoreof 0‑10,whichmay indicatea lackof overexpression.

[0157] In some embodiments, the cancer, e.g. gastric cancer, has already been determined to overexpress FGFR2-IIIb and / or to carry an FGFR2 gene amplification. In other embodiments, the methods herein assess either or both of the FGFR2IIIb expression andFGFR2gene amplification status before treatment is given, for example, to determinewhether treatment with an anti-FGFR2-IIIb antibody is warranted. In some embodiments, the methods herein are used to treat gastric cancer which has been determined (a) to overexpress FGFR2-IIIb as indicated by an IHC signal of 2+ or 3+ in at least 10%of tumor cells and / or (b) tohaveFGFR2geneamplification in ctDNA. In someembodiments, themethodsherein are used to treat gastric cancerwhich has beendetermined (a) to overexpressFGFR2-IIIb as indicated by an IHCsignal of 3+ in at least 10% of tumor cells and / or (b) to have FGFR2 gene amplification in ctDNA. Routes of Administration, Carriers, and Additional Pharmaceutical Compositions

[0158] In various embodiments, antibodies may be administered in vivo by various routes, including, but not limited to, oral, intra-arterial, parenteral, intranasal, intravenous, intramuscular, intracardiac, intraventricular, intratracheal, buccal, rectal, intraperitoneal, intradermal, topical, transdermal, and intrathecal, or otherwise by implantation or inhalation. The subject antibodies may be formulated into preparations in solid, semi-solid, liquid, or gaseous forms; including, but not limited to, tablets, capsules, powders, granules, ointments, solutions, suppositories, enemas, injections, inhalants, and aerosols. A nucleic acid molecule encoding an antibody may be coated onto gold microparticles and delivered intradermally by a particle bombardment device, or "gene gun," as described in the literature (see, e.g., Tang et al., Nature 356:152‑154 (1992)). The appropriate formulation and route of administration may be selected according to the intended application.

[0159] In various embodiments, compositions comprising antibodies are provided in formulations with a wide variety of pharmaceutically acceptable carriers (see, e.g., Gennaro, Remington: The Science and Practice of Pharmacy with Facts and Comparisons: Drugfacts Plus, 20th ed. (2003); Ansel et al., Pharmaceutical Dosage Forms and Drug Delivery Systems, 7th ed., Lippencott Williams andWilkins (2004); Kibbe et al., Handbook of Pharmaceutical Excipients, 3rd ed., Pharmaceutical Press (2000)). Various pharmaceutically acceptable carriers, which include vehicles, adjuvants, and diluents, are available. Moreover, various pharmaceutically acceptable auxiliary substances, such as pH adjusting and buffering agents, tonicity adjusting agents, stabilizers, wetting agents and the like, are also available. Non-limiting exemplary carriers include saline, buffered saline, dextrose, water, glycerol, ethanol, and combinations thereof.

[0160] Compositions comprising an anti-FGFR2 antibody as described herein and one or more of the chemotherapy agents of mFOLFOX 6, oxaliplatin, leucovorin, and 5-FU, as described herein, are also provided herein. In some embodiments, the FGFR2 inhibitor and the chemotherapy agents are each comprised within separate containers or within separate compartments of a single container, for example, such that they are not mixed together. In some embodiments, the compositions comprise instructions for use, such as instructions for use in cancer treatment. EXAMPLES

[0161] The examples discussed below are intended to be purely exemplary of the invention and should not be considered to limit the invention in any way. The examples are not intended to represent that the experiments below are all or the only experiments performed. Example 1: A Phase 3, Randomized, Double-Blind, Placebo-Controlled Study of an anti-FGFR2-IIIb Antibody in Combination with Modified FOLFOX6 in Patients with Previously Untreated Advanced Gastric or Gastroe- sophageal Cancer, Preceded by a Phase 1 Dose-Finding, Safety Run-in Phase 22 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Protocol Synopsis

[0162] The following protocol will be run at up to 250 different study centers globally. The study will be conducted tin two parts, part 1: the Phase 1 dose-finding, safety run-in phase, and part 2: the Phase 3 study.

[0163] TheprimaryobjectivesofPart 1are: (a) todetermine the recommendeddose (RD)ofanti-FGFR2-IIIbwhengiven in combination with a fixed dose of infusional 5-fluorouracil, leucovorin, and oxaliplatin (mFOLFOX6) in patients with advanced gastrointestinal (GI) tumors, and (b) to evaluate the safety profile of escalating doses of anti-FGFR2-IIIb when given incombinationwithmFOLFOX6 inpatientswithGI tumors.ThesecondaryobjectivesofPart 1are: (a) toevaluate the safety and tolerability of longer term exposure to anti-FGFR2-IIIb when given in combination with mFOLFOX6 in patients with GI tumors, (b) to characterize the pharmacokinetic (PK) profile of anti-FGFR2-IIIb when given in combination with mFOLFOX6 in patients with GI tumors, and (c) to characterize the immunogenicity of anti-FGFR2-IIIb. Part 1 will also characterize the pharmacodynamic (PD) profile of anti-FGFR2-IIIb, when given in combination withmFOLFOX6, through evaluation of exploratory biomarkers in blood and hair follicle samples from patients with GI tumors.

[0164] The primary end-point for part I will be: incidence of Grade 2 or higher adverse events (AEs) assessed as related to anti-FGFR2-IIIb by the Investigator and clinical laboratory abnormalities defined as dose-limiting toxicities (DLTs). The secondary end-points for part 1will be: (a) incidence of AEs, clinical laboratory abnormalities, corneal and retinal findings, and electrocardiogram (ECG) abnormalities, (b) PK parameters of anti-FGFR2-IIIb, such as area under serum concen- tration-time curve (AUC), maximum serum concentration (Cmax), trough serum concentration (Ctrough), clearance (CL), terminal half-life (t12), volume of distribution, and accumulation ratio, will be derived from the serum concentration-time profiles when appropriate and applicable, and (c) immune response against anti-FGFR2-IIIb as determined by immu- nogenicity testing. This part may also explore biomarkers in blood and hair follicle samples.

[0165] In Part 2, the primary objective is to evaluate the clinical benefit of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6, through analysis of progression-free survival (PFS) in patients with FGFR2b-selected gastric or gastroesophageal cancer (hereafter referred to as gastric cancer orGC). The secondary objectives are (a) to evaluate the clinical benefit of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6, through analysis of overall survival (OS) in patients with FGFR2b-selected GC, (b) to evaluate the safety and tolerability of anti-FGFR2-IIIbwhen given in combinationwithmFOLFOX6 compared to placeboandmFOLFOX6 in patientswith FGFR2b-selectedGC, (c) to characterize thePKprofile of anti-FGFR2-IIIbwhen given in combination withmFOLFOX6 in patients with FGFR2b-selectedGC, (d) characterize the immunogenicity of anti- FGFR2-IIIb, and (e) to characterize the PD profile of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6, through analysis of the immune cell infiltrate and other exploratory biomarkers in pre-treatment and on-treatment tumor biopsies. The study may also (a) evaluate the clinical benefit of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6, through analysis of PFS based on Blinded Independent Review Committee (BIRC) assessment of progression, (b) evaluate the clinical benefit of anti- FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6, through analysis of objective response rate (ORR) in patients with FGFR2b selected GC, (c) evaluate the clinical benefit of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6, through analysis of ORR based on BIRC assessment of progression, (d) evaluate the clinical benefit of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6, through analysis of one year OS in patients with FGFR2b-selected GC, (e) evaluate the clinical benefit of anti-FGFR2-IIIb, when given in combinationwithmFOLFOX6 compared to placebo and mFOLFOX6, through analysis of duration of response (DOR) in patients with FGFR2b-selected GC, (f) explore the association between FGFR2 status (in tumor tissue and / or blood-based biopsy [ctDNA] assay) with clinical outcome, (g) explore the concordance between FGFR2 status in tumor tissue and FGFR2 amplification using a blood-based biopsy (ctDNA) assay, (h) characterize the PD profile of anti-FGFR2-IIIb, when given in combination withmFOLFOX6 compared to placebo and mFOLFOX6, through evaluation of exploratory biomarkers in blood samples from patients with FGFR2b- selected GC, and (i) assess patient reported outcomes (PROs) and quality of life (QOL) outcomes in patients with FGFR2b-selected GC receiving anti-FGFR2-IIIb when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6.

[0166] The endpoints for Part 2 include the primary end-point PFS, defined as time from randomization until the date of radiologically progressive disease based on Investigator assessment (per RECIST v. 1. 1) or death from any cause, whichever comes first, and various secondary endpoints. Secondary endpoints include: (a) OS, defined as time from randomization date until death fromany cause, (b) objective response based on Investigator assessment of tumor lesions per RECIST v1.1, (c) incidence of AEs, clinical laboratory abnormalities, corneal and retinal findings, and ECG abnormalities, (d) PK parameters of anti-FGFR2-IIIb at the RD when administered in combination with mFOLFOX6, such as AUC, Cmax, Ctrough, CL, t1 / 2, volume of distribution, and accumulation ratio, will be derived from the serum concentration-time profiles when appropriate and applicable, (e) immune response as determined by immunogenicity testing, and (f) levels of immune cell infiltrate and other exploratory biomarkers in pre-treatment and on-treatment tumor biopsy samples. The study may also evaluate: (a) one year OS, defined as the proportion of patients who receive at least 23 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 one dose of anti-FGFR2-IIIb and are alive one year later, (b) DOR limited to patients with a response as determined by the Investigator per RECIST v1.1 and defined as the time of first response as determined by the Investigator per RECIST v1.1 to progression or death, whichever comes first, (c) correlation between identified FGFR2 status in tumor tissue and / or blood-based biopsy (ctDNA) assay and objective response per RECIST v1.1, (d) correlation between identified FGFR2 status in tumor tissue and FGFR2 amplification in blood-based biopsy (ctDNA) assay, (e) exploratory blood-based biomarkers, and (f) change from baseline in QoL as measured by EQ‑5D‑5L and the EORTC QLQ-C30.

[0167] The study design is as follows. The study is a 2-part, multicenter study to evaluate the safety, tolerability, PK, PD, and efficacy of anti-FGFR2-IIIb when given in combination with mFOLFOX6. The study will include an open-label, Part 1 dose escalation and a randomized, double-blind, placebo-controlled, Part 2 study in patients with FGFR2b+ gastric cancer. Part 1 consists of a minimum of 2 planned dosing cohorts of anti-FGFR2-IIIb in combination with mFOLFOX6 in eligible patients with advanced GI tumors to determine the RD of anti-FGFR2-IIIb to be administered in combination with mFOLFOX6.Part 2consistsof twoexpansionarms (1:1 randomization)with theaimofevaluating thesafetyandefficacyof anti-FGFR2-IIIb at the RD in combination with mFOLFOX6 compared to placebo and mFOLFOX6 in patients with FGFR2b-selected advanced GC (as determined by prospective immunohistochemistry (IHC) analysis of FGFR2b expression and / or a blood-based assay demonstrating FGFR2 amplification). Patients will be enrolled into either Part 1 or Part 2 of the study, but not both. After an initial screening period of up to 14 days (2weeks), patientswill be treatedwith mFOLFOX6 (with or without anti-FGFR2-IIIb) every 2 weeks in 14-day cycles. Patients may have initiated or received mFOLFOX6chemotherapyprior toenrollment intoPart 1, buteligibility requires that thepatient beacandidate to receiveat least 2 additional cycles ofmFOLFOX6chemotherapy (there is noupper limit on the number of FOLFOXcycles patients in Part 1mayhave received, or theymaynot have receivedany).Eachpatient enrolled intoPart 1will beobserved for 28days for safety assessments and occurrence of dose-limiting toxicities (DLT Period). Upon completion of the DLT Period, patients may continue receiving anti-FGFR2-IIIb in combination with mFOLFOX6 at the Investigator’s discretion. Additional treatments may be administered every 2 weeks in 14-day cycles until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or until the patient meets any of the other protocol-specified withdrawal criteria. There is nomaximumnumber of doses of anti-FGFR2-IIIb. Ongoing administration of themFOLFOX6 regimenbeyond theDLTPeriodwill beaccording to regional standardof care. InPart 2, patientswhose tumor is positive for FGFR2b by IHC (score of 2+ or 3+) or blood, have completed 2 cycles of mFOLFOX6 chemotherapy as standard first line therapy foradvancedstagegastric cancer, andhavesigned the informedconsent,will be randomized1:1 tobe treatedwith anti-FGFR2-IIIb in combination with mFOLFOX6 or placebo and mFOLFOX6 every 2 weeks in 14-day cycles at an RD selected after assessment of data obtained in Part 1. Enrolled patients may continue treatment every 2 weeks in 14-day cycles until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or until the patient meets any of the other protocol-specifiedwithdrawal criteria. All treatment decisionswill bemadeby the Investigator using local assessments. After discontinuation of study treatment for reasons other than progression or withdrawal of consent, tumor assessmentswill continue until the patient initiates additional anti-cancer therapy. In addition, patients in bothPart 1 and Part 2 will undergo long-term follow-up for survival by clinic visit or by telephone approximately every 3 months± 28 days after the EOT visit until up to 24months after the last patient is enrolled into the study, or until death, loss to follow-up, withdrawal of consent or study termination by the Sponsor (whichever occurs first).

[0168] Part 1 is anopen-label dose-escalation study of anti-FGFR2-IIIb given in combinationwithmFOLFOX6.Patients eligible for Part 1 have unselected GI cancer (with or without FGFR2b overexpressing tumors) with unresectable, locally advanced, or metastatic disease, and are candidates to receive both anti-FGFR2-IIIb and mFOLFOX6 chemotherapy. FGFR2 status will be determined retrospectively by IHC and blood-based biopsy (ctDNA) assay. Patients enrolled into Part 1 will be treated with escalating doses of anti-FGFR2-IIIb in combination with a fixed-dose backbone chemotherapy regimen of mFOLFOX6 every 2 weeks in 14-day cycles, as follows:

[0169] Anti-FGFR2-IIIbAdministration:anti-FGFR2-IIIb IV is administeredevery 2weeksonDay1of each cycle prior to administration of mFOLFOX6 chemotherapy. Anti-FGFR2-IIIb will be administered as an approximately 30 minute IV infusion via a peripheral vein or central venous catheter with in-line filter.

[0170] Backbone Chemotherapy Regimen: Administration of mFOLFOX6 chemotherapy will commence on Day 1 of each treatment cycle and after administration of anti-FGFR2-IIIb (following a 30-minute rest). ThemFOLFOX6 regimen is administered every 2 weeks as follows: oxaliplatin 85 mg / m2 IV infusion over 120 minutes, leucovorin 400 mg / m2 IV infusion over 120 minutes, followed by fluorouracil (5 FU) 400 mg / m2 IV bolus, followed by 5-FU 2400 mg / m2 as a continuous IV infusion over 46 hours. The administration of oxaliplatin does not require pre-hydration. Premedicationwith anti-emetics, such as serotonin antagonists with or without dexamethasone,may be usedwhere clinically indicated at the discretion of the Investigator per local standard of care.Dose Levels (Part 1) InPart 1, twodose cohorts of anti-FGFR2-IIIb are anticipated in a standard 3+3 dose escalation design, with a minimum of 3 patients enrolled into each cohort. The anticipateddose levels are:Dose level 1: 10mg / kg anti-FGFR2-IIIb,Dose level 2: 15mg / kg anti-FGFR2-IIIbDose level ‑1: 6 mg / kg anti-FGFR2-IIIb (only if dose reduction is required from Dose Level 1).

[0171] All dose escalation decisions will be based on an assessment of DLTs, overall safety, and tolerability, and will be madeafter the lastpatientenrolled ineachcohort hascompleted the28-dayDLTPeriod (completionof2 treatment cycles). 24 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Dose escalation decisions will be agreed upon by the Cohort Review Committee (CRC), consisting of the Sponsor and Investigators. Review of safety and PK parameters may inform decisions to add cohorts with alternative dose levels in order to reachanoptimal target exposure.DoseLevel ‑1will onlybeenrolled if≥2DLTsareobservedatDoseLevel 1.DLTs are defined below.

[0172] Doseescalation decisionswill bebasedon the followingalgorithm: if noneof the 3patients in a cohort haveDLTs, thenext cohortmaybeopened; if 1 / 3 patients in acohort showsDLTs, enroll 3morepatients in the samecohort; if 2 / 3 or 3 / 3 patients in a cohort show DLTs, stop enrollment and enter 3 more patients in cohort below (i.e. at the lower dose level) of only 3hadbeen in theprevious cohort, if 1 / 6 patients in a cohort showDLTs, open thenext cohort, and if 2 / 6 or greater show DLTs, stop enrollment and enter 3 more patients at the dose level below if only 3 patients had ben entered n that cohort.

[0173] The RD of anti-FGFR2-IIIb for Part 2 will be identified by the CRC based on an evaluation of the overall safety, tolerability, and PK. The RD, therefore, may or may not be the same as the identifiedmaximum tolerated dose (MTD). For example, if theMTD is not reached, or if data from subsequent cycles of treatment fromPart 1 provide additional insight on the safety profile, then the RD may be a different, though not higher, dose than the MTD. The MTD is defined as the maximumdoseatwhich<33%of patients experienceaDLTduring theDLTPeriod. If aDLT is observed in 1of 3 patients at a given dose level, then 3 additional patients will be enrolled at that same dose level. Dose escalationmay continue until 2 of 3 to6patients treatedat adose level experienceaDLT (dose level not toexceed15mg / kg). Thenext lowerdosewill then beconsidered theMTD.Once theMTDorRDhasbeen reached, up to6additional patientswill beadded, to further explore the safety and PK at this dose level. The total enrollment for Part 1 will, therefore, be approximately 9 to 12 patients. Any patient who does not receive 2 doses of anti-FGFR2-IIIb in combination with mFOLFOX6 during the DLT Period will be considered unevaluable and the patient will be replaced. The replaced patientmay continue on study after discussionwith theSponsor.Nomore than2dosesofanti-FGFR2-IIIbor2cyclesofmFOLFOX6shouldbeadministeredduring the28-day DLT Period. On completion of the DLT Period, patients may continue receiving anti-FGFR2-IIIb in combination with mFOLFOX6, administered every 2 weeks in 14-day cycles until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or until the patient meets any of the other protocol-specified withdrawal criteria. Dose modification criteria for anti-FGFR2-IIIb and mFOLFOX6 are described below. In the case of discontinuation of mFOL- FOX6 chemotherapy administration for any reason prior to disease progression (e.g., cumulative toxicity or completion of mFOLFOX6 chemotherapy per regional practice), anti-FGFR2-IIIb may be continued as monotherapy and administered every 2 weeks until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or until the patientmeets any of the other protocol-specifiedwithdrawal criteria. In the event a cycle ofmFOLFOX6 is delayed beyond 14 days due to chemotherapy-related toxicity, anti-FGFR2-IIIb administration should not be delayed andmay continue to be administered every 2 weeks. Initiation of a new cycle of mFOLFOX6 following a dosing delay should be synchronized with administration of an anti-FGFR2-IIIb infusion where possible (but is not a study requirement).

[0174] In the case of discontinuation of anti-FGFR2-IIIb for any reason prior to disease progression (e.g., cumulative toxicity), mFOLFOX6 chemotherapy may continue to be administered in accordance with local regional practice, or until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or the patient meets any of the other protocol-specified withdrawal criteria

[0175] Patients will be enrolled into Part 2 with the objective of characterizing the safety and efficacy of anti-FGFR2-IIIb combined with mFOLFOX6 compared to placebo and mFOLFOX6 in an FGFR2b-selected gastric cancer patient population. Enrollment into Part 2 will begin only once an RD for anti-FGFR2-IIIb, which will not exceed 15 mg / kg, has been identified by the CRC in Part 1. Part 2 is double-blind and will consist of a total of up to approximately 360 FGFR2b-selected gastric cancer patients randomized 1:1 to receive oneof two treatment arms: Arm1: anti-FGFR2-IIIb at the RD and mFOLFOX6 administered every 2 weeks, or Arm 2: Placebo and mFOLFOX6 administered every 2 weeks. Opening of Part 2 for enrollment will be at the discretion of the Sponsor. Patients with gastric cancer with unresectable, locally advanced, or metastatic disease who are eligible for first-line mFOLFOX6 chemotherapy and have received 2 cycles of mFOLFOX6 will be enrolled into Part 2 of the study. Patients will be selected for enrollment based on FGFR2b overexpression and / or FGFR2 amplification, as determined by a validated IHC or blood-based biopsy (ctDNA) assay, respectively. Patients who do not demonstrate either FGFR2b overexpression using IHC or amplification using a blood- based biopsy (ctDNA) assay will not be eligible for enrollment; however, positivity based on one or both of the assays is adequate to meet eligibility requirements (e.g., positive by blood-based biopsy [ctDNA] assay, but negative by IHC). Enrolled patients may continue treatment every 2 weeks in 14-day cycles until Investigator-assessed radiographic or clinical diseaseprogression, unacceptable toxicity, or until thepatientmeets anyof theother protocol-specifiedwithdrawal criteria. All treatment decisions will be made by the Investigator using local.

[0176] The inclusion criteria areas follows.Patientsenrolling intoeitherPart 1orPart 2 of the studymust be≥18years of age; have disease that is unresectable, locally advanced, or metastatic; Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1;must provide tumor tissue for determination of FGFR2 status; provide informed consent; and satisfy all other eligibility criteria described below. Patients enrolling into Part 1 (Dose-Escalation Safety Run-in) of the studymust also meet the following inclusion criteria: Histologically or cytologically confirmed gastrointestinal malignancy for which mFOLFOX6 is considered an appropriate treatment (e.g., gastric cancer, colorectal carcinoma, pancreatic 25 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 adenocarcinoma). No more than 2 prior chemotherapy regimens for metastatic disease (not including prior adjuvant chemotherapy with 5-FU and / or oxaliplatin). Patient must be a candidate for at least 2 cycles of mFOLFOX6 chemother- apy.

[0177] Patients enrolling into Part 2 (Dose-Expansion) of the study must also meet the following inclusion criteria: Histologically documented gastric or gastroesophageal junction adenocarcinoma. FGFR2b overexpression as deter- mined by IHC and / or FGFR2 amplification as determined by blood-based biopsy (ctDNA) assay. No prior chemotherapy formetastaticorunresectabledisease (except asnoted in InclusionCriteria#20 formFOLFOX6) .Noprior platinum-based chemotherapy (except as noted in Inclusion Criteria #20 for mFOLFOX6). If prior adjuvant or neo-adjuvant therapy (chemotherapy and / or chemoradiation) has been received, more than 6 months must have elapsed between the end of adjuvant therapy and enrollment.

[0178] A patient must be a candidate for mFOLFOX6 chemotherapy and have received 2 cycles of mFOLFOX6 chemotherapy prior to study enrollment (but not to exceed 2 cycles). Patients enrolling into either Part 1 or Part 2 will be excluded if they have untreated or symptomatic central nervous system (CNS) metastases; impaired cardiac function or clinically significant cardiac disease; elevated QTcF; peripheral sensory neuropathy ≥ Common Terminology Criteria for Adverse Events (CTCAE) grade 2; positive HER2 status; or other condition that may increase the risk associated with study participation. No waivers of these inclusion or exclusion criteria will be granted.

[0179] In Part 1, anti-FGFR2-IIIb will be supplied in a sterile vial for dilution into an intravenous bag for administration by the study site over approximately 30minutes every 14days (+ / ‑3days) until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or other cause for protocol-specified study withdrawal.

[0180] In Part 2, blinded IP (anti-FGFR2-IIIb / placebo) will be supplied and administered in a similar fashion to open- label anti-FGFR2-IIIb in Part 1.

[0181] Oxaliplatin, 5-FU, and leucovorin will be supplied to each site as per routine institutional practice. The mFOLFOX6 regimen will be administered every 14 days (+ / ‑ 3 days) until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or other cause for protocol-specified study withdrawal. Refer to the most current regional package insert for preparation and complete prescribing information.

[0182] Blood samples will be collected to evaluate PK parameters of anti-FGFR2-IIIb, such as AUC, Cmax, Ctrough, CL, t1 / 2, volume of distribution, and accumulation ratio. In Part 1, blood samples will be collected at the time points outlined below tomeasure serum levels of anti-FGFR2-IIIb in all enrolled patients. In Part 2, blood samples will be collected for the first 60 patients randomized into Part 2 at the time points outlined below. For Part 1 andPart 2, blood samples for anti-anti- FGFR2-IIIb antibodies will be collected at the timepoints specified.

[0183] Tumor response assessment will be performed both by the Investigator and by blinded central radiology review per RECIST v.1.1 guidelines. Full details around independent review by a BIRC will be listed in an Independent Imaging Review Charter.

[0184] Efficacy measures will include tumor assessments consisting of clinical examination and appropriate imaging techniques, preferably computed tomography (CT) scans of the chest, abdomen, and pelvis with appropriate slice thickness per RECIST guidelines; other assessments (magnetic resonance imaging [MRI], X ray, positron emission tomography [PET], and ultrasound) may be performed, if required. Tumor assessments will be performed at Screening (within 2 weeks of Cycle 1 Day 1 in Part 1 and Part 2), then every 6 weeks from the first dose, for 24 weeks, and then approximately every 12 weeks thereafter. Once an initial complete response (CR) or partial response (PR) is noted, confirmatory scans must be performed 4 to 6 weeks later.

[0185] Safety measures will include AEs, hematology, clinical chemistry, urinalysis, vital signs, body weight, conco- mitant medications / procedures, ECOG performance status, targeted physical examinations, ECGs, and ophthalmology examinations. An independent Data Monitoring Committee (DMC) will evaluate safety study data (AE and SAEs) on a regular basis throughout the entire treatment phase in Part 2.

[0186] In Part 1: Tumor tissue submitted for evaluation of FGFR2 status will be retrospectively analyzed for FGFR2b overexpression using IHC.

[0187] Samples for blood-based biopsy (ctDNA) assaywill be collected prior to the first dose of study drug (Cycle 1 Day 1) and analyzed retrospectively for FGFR2 amplification. Blood samples for exploratory biomarker analysis will be collected prior to dosing onDay 1 of Cycles 1 and 2, at 48 hours following theCycle 1 Day 1 andCycle 2 Day 1 doses (Day 3), prior todosingonCycle3Day1 for patientswhocontinue treatment beyond the28-dayDLTPeriod, andat theEOTvisit. Hair follicle sampleswill becollectedprior todosingonCycle1Day1,Cycle3Day1, andCycle5Day1, andat theEOTvisit from all patients for whom sampling is possible.

[0188] In Part 2: Tumor tissue will be submitted for evaluation of FGFR2 status and will be prospectively analyzed for FGFR2b overexpression using IHC. Blood samples for ctDNA assessment will be analyzed prospectively for FGFR2 amplification. In addition, blood-based biopsy (ctDNA) assays will be collected longitudinally every 6 weeks from the first dose for 24 weeks, and then approximately every 12 weeks thereafter, and analyzed retrospectively for FGFR2 amplification. A sample will also be collected at the EOT visit for all Part 2 patients. A sample will also be collected at the EOT visit for all Part 2 patients. Blood samples for exploratory biomarker analysis will be collected prior to dosing on 26 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Day1ofCycles 1 and2, at 48 hours following theCycle 1Day1andCycle 2Day1doses (Day3), prior to dosingonCycle 3 Day 1, and at the EOT visit.

[0189] Fresh tumor biopsies, mandatory as feasible, will be performed before treatment and on-treatment within 7 days prior to Cycle 3Day 1 (and at least 24 hours prior to dosing) for up to 30 patients randomized into Part 2. Feasibility at each time point will be assessed by the Investigator and should include a consideration of patient safety. If the Investigator assesses that abiopsy is not feasible, then this determinationmust be recorded in the sourcedocuments. For patientswho have had a biopsy acquired within 12 weeks prior to enrollment, that sample may fulfill the requirement for a fresh pre- treatment biopsy provided adequate sample is available for PD analysis (a single paraffin-embedded block or approxi- mately 10 slides). Patients in Part 2 may also have an optional on-treatment biopsy upon documented tumor response and / or optional post-treatment biopsy upon documented tumor progression after discussion with the Sponsor.

[0190] The total enrollment planned for this study is up to approximately 372 patients. Up to approximately 12 patients evaluable for any dose limiting toxicity, per standard 3+3 design, will be enrolled into Part 1. For Part 2, efficacy and tolerability will be examined by enrollment of up to approximately 360 patients with FGFR2b-selected gastric cancer, randomized 1:1 to receive anti-FGFR2-IIIb in combinationwithmFOLFOX6 or placebo andmFOLFOX6. Eligible patients will be stratified according to geographic region (US and EU vs Asia vs Rest of World), prior treatment status (de novo vs adjuvant / neo-adjuvant), and measurable disease status (measurable vs non-measurable).

[0191] In Part 1, all analyses will be descriptive and will be presented by dose group and overall as appropriate. Descriptive statistics will include number of observations, mean, standard deviation, median, range, and inter-quartile range for continuous variables, and the number and percent for categorical variables; 95% confidence intervals will be presentedwhere appropriate. InPart 2, the primary efficacy analysis is the comparison ofPFS in patients treatedwith anti- FGFR2-IIIb in combination with mFOLFOX6 or placebo and mFOLFOX6. The primary endpoint, PFS, is defined as time from randomization until the date of radiologically progressive disease based on Investigator assessment (per RECIST v.1.1) or death from any cause, whichever comes first. The secondary efficacy endpoints includeOS andORR. There will be an interim analysis and primary analysis for PFS and both are event-based analyses. Only futility test of PFS will be conductedat the interimanalysis after 48events (50%of target 96PFSevents for primaryanalysis ofPFS)observed in the enrolled patients to exclude HR>0.806 for the combination of anti-FGFR2-IIIb and mFOLFOX6 compared with placebo andmFOLFOX6. It is estimated that the interim analysis will occur approximately 20months from the 1st patient enrolled. The primary analysis of PFS will be conducted when at least 96 PFS events have been observed in the first 156 enrolled patients, and will be performed using the intent-to-treat (ITT) population. The primary analysis will include only radio- graphic progression events as determined by the Investigator per RECIST v.1.1 and deaths. The primary analysis of PFS will be conductedusingastratified log-rank2-sided testwitha0.05 level of significance.Thestratification factorswill be the same used to stratify the randomization schedule as documented in the interactive voice and Web response system (IXRS). If the p-value for the stratified log-rank test is statistically significant (< 0.05 two-sided) and the HR is < 1, the null hypothesis of no difference in PFS will be rejected and it will be inferred that PFS is statistically prolonged in the group receiving anti-FGFR2-IIIb in combination with mFOLFOX6 compared with the group receiving placebo andmFOLFOX6. The median PFS and the associated 95% confidence interval for each treatment arm will be estimated using the Kaplan- Meier method. The hazard ratio (HR= λanti-FGFR2-IIIb+ mFOLFOX6 / λmFOLFOX6) will be estimated using a Cox regression modelwith treatment groupas theonlymaineffectandstratifyingby thesamestratification factorsaswereused for the log- rank test. An unstratified HR will also be presented.

[0192] Analyses of secondary endpoints including OS and ORR will be conducted when the primary endpoint, PFS, is statistically significant, and formal hypotheses ofOSandORRwill be tested hierarchically at a level of 0.05. TheOSwill be tested first and if it is significant, the ORR will be tested next. The type I error rate of testing primary and secondary endpoints will be in a control by employing this fixed-sequence testing procedure at a level of 0.05. Therewill be an interim andfinal analysis forOSplanned if the test forPFS is statistically significant. The interimanalysis ofOSwill beconductedat the timeof primary analysis ofPFS.ShouldOSbeanalyzed, analysis ofOSat the interim (i.e.,whenat least 96PFSevents have been observed), and at the end (i.e., when 249 deaths have been observed)will be performed on the ITT population. The hypothesis testing of OSwill be conducted using a stratified log-rank 2-sided test with a 0.05 level of significance. The group sequentialmethodwill be used to allocate type I error rate based onO’Brien-Fleming boundary and type II error rate based on the Gamma family with parameter ‑4 at the interim and final analysis of OS. The stratification factors will be the same used to stratify the randomization schedule as documented in the IXRS. The median OS and the associated 95% confidence interval for each treatment arm will be estimated using the Kaplan-Meier method. The HR will be estimated using aCox regressionmodel with treatment group as the onlymain effect and stratifying by the same stratification factors as were used for the log-rank test. An unstratified HR will also be presented. The ORR is defined as the proportion of patients with partial or complete response as defined by the Investigator per RECIST v.1.1. The primary analysis of ORR will be performed among the patientswith baselinemeasurable disease. In the analysis ofORR, patients who do not have anypost-baselineadequate tumorassessmentswill be countedasnon-responders.Formal hypothesis testingofORRwill be performed using the stratifiedCochran-Mantel-Haenszel test. The stratification factors will be the same used to stratify the randomization schedule as documented in the IXRS. 27 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55

[0193] PowerandSampleSize:This study isdesigned toprovideadequatepower for primaryanalysis ofPFS.Basedon a median PFS (mPFS) for patients receiving placebo and mFOLFOX6 of 6 months, approximately 156 patients (randomized 1:1) with a target of 96 PFS events are required to demonstrate a hazard ratio (HR) of 0.5 for mPFS with a power of 90% (2-sided α =0.05) for the combination of anti-FGFR2-IIIb and mFOLFOX6 compared with placebo and mFOLFOX6 after 24 months of accrual and 6 months of follow up. Assuming an exponential distribution of PFS, this corresponds to an increase inmPFS from6months to 12months. In the current design, theminimumobserved effect that would result in statistical significance for PFS is a 50% improvement (HR = 0.67) from 6 to 9 months. This study is also powered for primary analysis of OS. Based on a median OS (mOS) for patients receiving placebo and mFOLFOX6 of 10 months, enrollment of the study will continue to up to approximately 360 patients with a target of 249 death events to demonstrate an HR of 0.7 for mOSwith a power of 80% at the overall type I error level of 0.05 for the combination of anti- FGFR2-IIIb andmFOLFOX6compared to placeboandmFOLFOX6after 36months of accrual and10months of follow-up after enrollment of the last patient. Assuming an exponential distribution of OS, this corresponds to an increase of 43% in median OS from 10 months to 14.3 months. In the current design, the minimum observed effect that would result in statistical significance for OS at the final analysis is a 28% improvement (HR = 0.78) from 10 to 12.8 months.

[0194] Safety Analysis: The analyses of safety will include all patients who receive any study drug (anti-FGFR2-IIIb and mFOLFOX6 or placebo and mFOLFOX6) throughout the study duration and provide any post-treatment safety informa- tion. All AEs will be coded using the Medical Dictionary for Regulatory Activities (MedDRA). The Investigator will classify the severity of AEs using the CTCAE v 4.03. A treatment emergent adverse event (TEAE) is defined as any event with an onset date on or after date of first dose of study drug, or any event present before treatment that worsens after treatment. Only TEAEs with an onset date prior to date of last dose + 30 days will be tabulated in summary tables. The number and percentage of patients who experience AEs will be summarized by system organ class, preferred term, relationship to studydrug, andseverity for each treatment group.Aby-patient listingwill beprovided for thosepatientswhoexperiencean SAE, including death, or experience an AE associated with early withdrawal from the study or discontinuation from study drug.Clinical laboratorydatawill besummarizedby the typeof laboratory test.Thenumberandpercentageofpatientswho experience abnormal (ie, outside of reference ranges) and / or clinically significant abnormalities after study drug admin- istrationwill bepresented for eachclinical laboratorymeasurement. For eachclinical laboratorymeasurement, descriptive statistics will be provided for baseline and all subsequent post-treatment scheduled visits. Changes from baseline to the posttreatment visits will also be provided. Descriptive statistics of vital signs will also be provided in a similar manner. In addition, shift from baseline in CTCAE grade (where applicable) and by high / low flags (where CTCAE grades are not defined) will be presented by treatment group. No formal comparisons of safety endpoints are planned.

[0195] PKAnalysis: PKparameterswill be estimated using non-compartmental analysis, though compartment analysis may be employed if appropriate. Detailed Protocol 1. Introduction Anti-FGFR2-IIIb Background

[0196] The role of the fibroblast growth factor (FGF) receptor (FGFR) pathway in cancer is well known. FGFs can stimulate the transformationandproliferationof tumor cells andstimulateangiogenesis. Thereare22knownhumanFGFs with theexpressionof individual FGFsgenerally restricted to specific tissues, cell types, and / or developmental stage. FGF signaling is mediated by a family of transmembrane tyrosine kinase receptors encoded by four distinct genes producing FGF receptor subtypes termed FGFR1‑4 (Turner and Grose 2010).

[0197] FGFR2 has two splicing variants, b and c. In general, FGFR2b is expressed in tissues of epithelial origin (e.g., stomach, skin) (Miki 1992). The major ligands signaling through FGFR2b are FGF7, FGF10 and FGF22. Alteration in signaling in the FGF / FGFR2 pathway (e.g., overexpression of FGFR2b protein or amplification ofFGFR2 gene) has been associatedwithgastric, breast, andother cancers, andappears toportendaworseprognosis (Wu2013, Turner andGrose 2010). In fact, asearly as1990, subsetsof patientswithgastric cancer (~3 to9%)andbreast cancer (1 to2%)werenoted to haveamplificationof theFGFR2gene,which residesonchromosome10q26. Ingastric cancer,FGFR2amplification leads to high-level expression of the FGR2b receptor on the surface of the cells. An FGFR2b-specific Antibody

[0198] Anti-FGFR2-IIIb is a humanized monoclonal antibody (IgG1 isotype) specific to the human FGFR2b receptor (NCBI reference sequence ID NP_001138385.1) that blocks FGF ligand binding to the receptor. Anti-FGFR2-IIIb is directed against the third Ig region of the FGFR2b receptor isoform, the region that is alternatively spliced and regulates ligand specificity. This antibody is glycosylated, but is produced in a Chinese hamster ovary (CHO) cell line that lacks the 28 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 FUT8gene (α1,6-Fucosyltransferase) and therefore lacks a core fucose in thepolysaccharide portion of the antibody. The absence of the core fucose results in higher affinity for the Fc receptor FcγRIIIa compared to the fucosylatedmolecule and potentially enhances immune cell-mediated tumor cell killing (Shinkawa 2003). The antibody has thus been glycoengi- neered for enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) (Gemo 2014). Anti-FGFR2-IIIb inhibits FGF ligand-stimulated FGFR2b phosphorylation and cell proliferation in cell culture in FGFR2b overexpressing gastric and breast cancer cell lines. Anti-FGFR2-IIIb also inhibits tumor growth in FGFR2b overexpressing gastric and breast xenograft models. The 3 potential mechanisms of action of anti-FGFR2-IIIb thus include blocking ligand binding and downstream signaling, decreasing expression of the FGFR2b driver protein, and enhancing ADCC.

[0199] Anti-FGFR2-IIIb can produce complete and durable tumor growth inhibition in FGFR2b-overexpressing and FGFR2 gene-amplified gastric cancer xenografts in immune-compromisedmice where FGFR2b is considered a driver of tumor growth (Gemo 2014). In addition, anti-FGFR2-IIIb demonstrates recruitment of NK cells and concomitant tumor growth inhibition in the 4T1 syngeneic tumor model with modest expression of FGFR2b. These data suggest that ADCC may be efficacious in patients withoutFGFR2 gene amplificationwithmoderate FGFR2b overexpression, and that ADCC activity may be a major contributor to the mechanism of action in these patients.

[0200] Additionally, since anti-FGFR2-IIIb is specific for the FGFR2b receptor, it does not interfere with signaling of the other FGFs / FGFRs, including FGFR2c. In contrast to the FGFR tyrosine kinase inhibitors (TKIs), anti-FGFR2-IIIb does not inhibit FGF23 signaling. FGF23 is a ligand involved in calcium / phosphate metabolism. Thus, treatment with anti- FGFR2-IIIb is not expected to cause significant dose-limiting hyperphosphatemia associated with the FGFRTKIs (Andre 2013, Brown 2005, Dienstmann 2014, Sequist 2014). mFOLFOX6

[0201] Infusional 5-fluorouracil, leucovorin, and oxaliplatin (mFOLFOX6) is an approved chemotherapy agent and is a standard of care for first-line treatment ofmetastatic gastric cancer. 5-FU is themain chemotherapeutic agent used for the treatment of gastric cancer around the world and is frequently combined with other therapies after research showed improved clinical outcomes resulting from 5-FU combination chemotherapies (Keam 2008). The standard treatment, Adrucil® also known as 5-fluorouracil (5-FU), is a commonly used chemotherapeutic agent that is currently indicated to treat colorectal cancers, breast cancer, gastric cancer, and pancreatic cancer. Anti-FGFR2-IIIb and mFOLFOX6 Starting Dose Justification

[0202] A starting dose of 10 mg / kg anti-FGFR2-IIIb administered as an IV infusion every 2 weeks in 28-day cycles is planned for Part 1 of this dose escalation safety run-in study.

[0203] In the prior Phase I clinical study, dose escalation was performed in patients with solid tumors (n=19) and gastric cancer patients (n=8). During the dose escalation, there were no dose limiting toxicities (DLTs) at any dose level and therefore no maximum tolerated dose (MTD) of anti-FGFR2-IIIb was identified. The 15 mg / kg was chosen as the expansion dose based on preclinical modeling of target drug concentrations and observed tolerability aswell as evidence of observed efficacy. At 15mg / kg every 2 weeks dosing, it is expected to achieve anti-FGFR2-IIIb trough concentration at steady state (Ctrough ss) of 60 µg / mL in majority of patients, which was derived from the mouse efficacy study using the OCUM2 FGFR2-amplified gastric cancer xenograft model.

[0204] Based on published data from population PK analyses, no clinically significant differences were observed in the PK by race for antibody therapeutics including bevacizumab (Genentech Inc.), trastuzumab (Genentech Inc.), pertuzu- mab (Genentech Inc. 2016), and ramucirumab (Eli Lilly andCompany). Importantly, the clinical data from the ongoinganti- FGFR2-IIIb study supports that a 10mg / kgdose is tolerable in humans.Anti-FGFR2-IIIb hasalso showna tolerable safety profile in the first-in-human study, with 53 patients treated at doses up to 15 mg / kg.

[0205] Thestartingdose formFOLFOX6 includes85mg / m2ofoxaliplatin, 350mgof calcium folinate (folinicacid), a400- mg / m2 dose of fluorouracil, and a 2400-mg / m2 dose of fluorouracil. Oxaliplatin and calcium folinate are administered concomitantly via IV infusion using a 3-way tap / Y-site connector. The smaller dose of fluorouracil is administered via IV bolus, and the larger dose of fluorouracil is administered via IV infusion over the course of 46 hours. mFOLFOX6 is administered every 14 days. Rationale for Part 2 Pre-screening

[0206] Anti-FGFR2-IIIb is an antibody designed to recognize the FGFR2b receptor when expressed on gastric tumors. The current hypothesis is that the presence of FGFR2b will be an important predictor of how patients with FGFR2b- selected gastric or gastroesophageal cancer (in Part 2) will respond. This is based on the preclinical observation that only tumors that overexpressedFGFR2b responded to anti-FGFR2-IIIb treatment in xenograft studies), aswell as early results from the ongoing first-in-human study indicating a higher degree of anti-FGFR2-IIIb activity in FGFR2b-positive patients. 29 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55

[0207] Patients in Part 2 will be selected for enrollment based on FGFR2b overexpression and / orFGFR2 amplification, as determined by a validated IHC (score of 2+ or 3+) or blood-based biopsy assay, respectively. Patients who do not demonstrate either FGFR2b overexpression using IHC or amplification using a blood-based biopsy assay will not be eligible for enrollment; however, positivity based on one or both of the assays is adequate to meet eligibility requirements (e.g., positive by blood-based biopsy assay, but negative by IHC).

[0208] Patients in Part 2 will be naive to prior chemotherapy for metastatic or unresectable disease; if prior adjuvant or neo-adjuvant therapy (chemotherapy and / or chemoradiation) has been received,more than 6monthsmust have elapsed between the end of adjuvant therapy and enrollment. These patients will have disease that is unresectable, locally advanced, or metastatic, and therefore are expected to begin treatment (mFOLFOX6) shortly after their diagnosis.

[0209] As the IHC results may require up to several weeks to complete, patients who are negative by the blood-based assay would face a delay in beginning their chemotherapy treatment while waiting for their eligibility to be confirmed by IHC. For this reason, all patients entering the study will be required to have received 2 cycles of mFOLFOX6 at the time of enrollment. Patients cannot have received more than 2 cycles or less than 2 cycles, as this could lead to an imbalance in treatment among study participants and potentially confound interpretation of the study results. It is anticipated that IHC results can be obtained during the time it will take to administer the first 2 cycles of mFOLFOX6. During this time, patients are not yet enrolled in the study, and thusmFOLFOX6will be administered according to local practice, and adverse events are not to be recorded as part of the study. Patients will provide pre-screening informed consent for the blood and IHC assays. If the IHC results are positive, the patient would complete the second course of mFOLFOX6, enter the screening period, and if all other eligibility criteria aresatisfied includingproviding informedconsent,would thenenroll into thestudy. If the IHC results are negative, and the blood-based biopsy was also negative, the patient is ineligible to participate in the study. Rationale for Tumor Biopsy and Blood Assessments

[0210] Patients in Part 2 of this trial are required to have both a tissue result and a blood result; therefore, a patient is not eligible if they cannot provide both tissue and blood plasma. Patients who do not demonstrate either FGFR2b over- expression using IHC or amplification using a blood-based biopsy assay will not be eligible for enrollment; however, positivity based on one or both of the assays is adequate to meet eligibility requirements (e.g., positive by blood-based biopsy assay, but negative by IHC). The blood test will reveal DNAamplification ofFGFR2,while the IHC test will show the extent of protein expression. Five Prime has developed an anti-FGFR2b antibody for nonclinical use, whose sensitivity and specificity to detect FGFR2b by IHC has been optimized.

[0211] In studies evaluating gastric cancer samples, FGFR2 amplification has been uniformly associated with sig- nificant FGFR2b surface expression, as detected by IHC (Gemo 2014). The antitumor effect of anti-FGFR2-IIIb that was observed in preclinical testingwas predicated upon the overexpression of FGFR2b in the tumor cell lines. Patientswithout overexpression of FGFR2b are unlikely to see a significant benefit from treatment with anti-FGFR2-IIIb andmFOLFOX6. The selection of patients with FGFR2b-positive tumors for treatment with anti-FGFR2-IIIb is supported by data from the ongoing Phase 1, first-in-human study of anti-FGFR2-IIIb. Study Objectives and Endpoints Part 1: Primary Objectives

[0212] To determine the recommended dose (RD) of anti-FGFR2-IIIb when given in combination with a fixed dose of infusional 5-fluorouracil, leucovorin, and oxaliplatin (mFOLFOX6) in patients with advanced gastrointestinal (GI) tumors.

[0213] Toevaluate the safety profile of escalating dosesof anti-FGFR2-IIIbwhen given in combinationwithmFOLFOX6 in patients with GI tumors. Part 1: Secondary Objectives

[0214] Toevaluate the safety and tolerability of longer termexposure to anti-FGFR2-IIIbwhen given in combinationwith mFOLFOX6 in patients with GI tumors.

[0215] To characterize the pharmacokinetic (PK) profile of anti-FGFR2-IIIbwhen given in combinationwithmFOLFOX6 in patients with GI tumors.

[0216] To characterize the immunogenicity of anti-FGFR2-IIIb. Part 1: Exploratory Objectives

[0217] To characterize the pharmacodynamic (PD) profile of anti-FGFR2-IIIb, when given in combination with mFOL- FOX6, through evaluation of exploratory biomarkers in blood and hair follicle samples from patients with GI tumors. 30 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Part 2: Primary Objectives

[0218] To evaluate the clinical benefit of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placeboandmFOLFOX6, throughanalysis of progression-free survival (PFS) in patientswithFGFR2b-selectedgastric or gastroesophageal cancer (hereafter referred to as gastric cancer or GC). Part 2: Secondary Objectives

[0219] To evaluate the clinical benefit of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6, through analysis of overall survival (OS) in patients with FGFR2b-selected GC .

[0220] To evaluate the safety and tolerability of anti-FGFR2-IIIb when given in combination withmFOLFOX6 compared to placebo and mFOLFOX6 in patients with FGFR2b-selected GC.

[0221] To characterize the PK profile of anti-FGFR2-IIIb when given in combination with mFOLFOX6 in patients with FGFR2b-selected GC.

[0222] To characterize the immunogenicity of anti-FGFR2-IIIb.

[0223] To characterize the PD profile of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placebo andmFOLFOX6, through analysis of the immune cell infiltrate and other exploratory biomarkers in pre-treatment and on-treatment tumor biopsies. Part 2: Exploratory Objectives

[0224] To evaluate the clinical benefit of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placeboandmFOLFOX6, throughanalysis ofPFSbasedonBlinded IndependentReviewCommittee (BIRC)assessment of progression.

[0225] To evaluate the clinical benefit of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6, through analysis of objective response rate (ORR) in patients with FGFR2b-selected GC.

[0226] To evaluate the clinical benefit of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6, through analysis of ORR based on BIRC assessment of progression.

[0227] To evaluate the clinical benefit of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6, through analysis of one year OS in patients with FGFR2b-selected GC.

[0228] To evaluate the clinical benefit of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6, through analysis of duration of response (DOR) in patients with FGFR2b-selected GC.

[0229] To explore the association between FGFR2 status (in tumor tissue and / or blood-based biopsy) with clinical outcome.

[0230] To explore the concordance between FGFR2 status in tumor tissue and FGFR2 amplification using a blood- based biopsy.

[0231] To characterize the PD profile of anti-FGFR2-IIIb, when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6, through evaluation of exploratory biomarkers in blood samples from patients with FGFR2b- selected GC.

[0232] To assess patient reported outcomes (PROs) and quality of life (QOL) outcomes in patients with FGFR2b- selected GC receiving anti-FGFR2-IIIb when given in combination with mFOLFOX6 compared to placebo and mFOL- FOX6. Part 1: Primary Study Endpoints

[0233] The incidence of Grade 2 or higher adverse events (AEs) assessed as related to anti-FGFR2-IIIb by the Investigator and clinical laboratory abnormalities defined as dose-limiting toxicities (DLTs). Part 1: Secondary Endpoints

[0234] The incidence of AEs, clinical laboratory abnormalities, corneal and retinal findings, and electrocardiogram (ECG) abnormalities.

[0235] PKparameters of anti-FGFR2-IIIb, such as area under serumconcentration-time curve (AUC),maximumserum concentration (Cmax), trough serum concentration (Ctrough), clearance (CL), terminal half-life (t1 / 2), volume of dis- tribution, and accumulation ratio, will be derived from the serum concentration-time profiles when appropriate and applicable.

[0236] To evaluate immune response as determined by immunogenicity testing. 31 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Part 1: Exploratory Endpoints

[0237] Exploratory biomarkers in blood and hair follicle samples. Part 2: Primary Endpoints

[0238] PFS, defined as time from randomization until the date of radiologically progressive disease based on Investigator assessment (per RECIST v.1.1 ) or death from any cause, whichever comes first. Part 2: Secondary Endpoints

[0239] OS, defined as time from randomization date until death from any cause.

[0240] Objective response rate (ORR) based on Investigator assessment of tumor lesions per RECIST v1.1.

[0241] Incidence of AEs, clinical laboratory abnormalities, corneal and retinal findings, and electrocardiogram (ECG) abnormalities.

[0242] PK parameters of anti-FGFR2-IIIb at the RDwhen administered in combination with mFOLFOX6, such as AUC, Cmax,Ctrough,CL, t1 / 2, volumeof distribution, and accumulation ratio, will be derived from the serumconcentration-time profiles when appropriate and applicable.

[0243] Immune response as determined by immunogenicity testing.

[0244] Levels of immune cell infiltrate and other exploratory biomarkers in pre-treatment andon-treatment tumor biopsy samples. Part 2: Exploratory Endpoints

[0245] OneyearOS, definedas theproportion of patientswho receive at least onedoseof anti-FGFR2-IIIb and are alive one year later.

[0246] DOR limited to patients with a response as determined by the Investigator per RECIST v1.1 and defined as the time of first response as determined by the Investigator per RECIST v1.1 to progression or death, whichever comes first.

[0247] The correlation between identified FGFR2 status in tumor tissue and / or blood-based biopsy and objective response per RECIST v1.1.

[0248] Thecorrelationbetween identifiedFGFR2status in tumor tissueandFGFR2amplification inblood-basedbiopsy.

[0249] Exploratory biomarkers in blood samples.

[0250] Change from baseline in QoL as measured by EQ‑5D‑5L and the EORTC QLQ-C30. Overall Design and Plan of the Study Overview

[0251] This is a2-part,multicenter study to evaluate the safety, tolerability, PK,PD,andefficacyof anti-FGFR2-IIIbwhen given in combination with mFOLFOX6. The study will include an open-label, Part 1 dose escalation safety run-in and a randomized, double-blind, placebo-controlled, Part 2 dose expansion.

[0252] Part 1 consists of a minimum of 2 planned dosing cohorts of anti-FGFR2-IIIb in combination with mFOLFOX6 in eligible patients with advanced GI tumors to determine the RD of anti-FGFR2-IIIb to be administered in combination with mFOLFOX6. Part 2 consists of 2 expansion arms (1:1 randomization) with the aim of evaluating the safety and efficacy of anti-FGFR2-IIIb at the RD in combination with mFOLFOX6 compared to placebo and mFOLFOX6 in patients with FGFR2b-selected advanced GC (as determined by prospective IHC analysis of FGFR2b expression and / or a blood- based assay demonstrating FGFR2 amplification). Patients will be enrolled into either Part 1 or Part 2 of the study, but not both.

[0253] After an initial screening period of up to 14 days (2 weeks), patients will be treated with mFOLFOX6 (with or without anti-FGFR2-IIIb) every 2 weeks in 14-day cycles. Patients may have initiated or received mFOLFOX6 che- motherapy prior to enrollment into Part 1, but eligibility requires that the patient be a candidate to receive at least 2 additional cycles ofmFOLFOX6 chemotherapy (there is no upper limit on the number of FOLFOX cycles patients in Part 1 may have received, or they may not have received any).

[0254] Each patient enrolled into Part 1 will be observed for 28 days for safety assessments and occurrence of dose- limiting toxicities (DLT Period). Upon completion of the DLT Period, patients may continue to receive treatments at the Investigator’sdiscretion.Additional treatmentsmaybeadministeredevery2weeks in14-daycycles thereafter asclinically indicated.

[0255] In Part 2, patients whose tumor is positive for FGFR2b by IHC or blood, who have completed 2 cycles of 32 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 mFOLFOX chemotherapy as standard first line therapy for advanced stage gastric cancer, and who have signed the informed consent, will be randomized 1:1 to be treatedwith anti-FGFR2-IIIb in combinationwithmFOLFOX6or placebo in combinationwithmFOLFOX6every 2weeks in 14-day cycles at anRDselected after assessment of data obtained in Part 1. Initial Screening Period Part 1

[0256] The screening period begins when patients sign the informed consent form (ICF). All patients will undergo screening assessments within 14 days (2 weeks) prior to the first dose of anti-FGFR2-IIIb. Any AEs unrelated to study procedures thatoccurafter signingof the informedconsent formandbeforeadministrationof thefirst anti-FGFR2-IIIbdose will not be collected during this period. Patients may have initiated or received mFOLFOX6 chemotherapy prior to enrollment into Part 1, but eligibility requires that the patient be a candidate to receive at least 2 additional cycles of mFOLFOX6chemotherapy (there is no upper limit on the number of FOLFOXcycles patients in Part 1mayhave received, or they may not have received any). Part 2

[0257] In Part 2, patients will be enrolled whose tumor is positive for FGFR2b by IHC or blood, who have completed 2 cycles ofmFOLFOX chemotherapy as standard first line therapy for advanced stage gastric cancer, andwho have signed the informed consent and met other eligibility criteria.

[0258] Eligibility for Part 2 will be evaluated in 2 steps: a Pre-Screening Period involving only testing for FGFR2b positivity by IHC and blood; and a Screening Period in which all remaining eligibility criteria are confirmed. Randomization Part 1

[0259] Part 1 is an open-label study. Patients who are determined to be eligible will be enrolled sequentially. Part 2

[0260] During thePre-screeningPeriod, patientswill be tested forFGFR2bpositivity.Patientswho testpositivebyoneor bothmethods (IHCand / or blood)will then enter theScreeningPeriod. (Note: if the blood test is positive, there is no need to wait for IHC results, as the patient is eligible at that point, and should begin the Screening Period).

[0261] Patients who meet eligibility will be randomized 1:1 to placebo in combination with mFOLFOX6 or anti-FGFR2- IIIb in combination with mFOLFOX6. Part 1 (Dose Escalation Safety Run-in)

[0262] Part 1 is an open-label dose-escalation study of anti-FGFR2-IIIb when given in combination with mFOLFOX6. Patients eligible for Part 1 have unselectedGI cancer (with orwithout FGFR2boverexpressing tumors)with unresectable, locally advanced, ormetastatic disease, and are candidates to receive both anti-FGFR2-IIIb andmFOLFOX6 chemother- apy. FGFR2 status will be determined retrospectively by IHC and blood-based biopsy.

[0263] Patients enrolled into Part 1 will be treated with escalating doses of anti-FGFR2-IIIb in combination with a fixed- dose backbone chemotherapy regimen of mFOLFOX6 every 2 weeks in 14-day cycles, as follows: Anti-FGFR2-IIIb Administration:

[0264] Anti-FGFR2-IIIb IV is administered every 2 weeks on Day 1 of each cycle prior to administration of mFOLFOX6 chemotherapy. Anti-FGFR2-IIIb will be administered as an approximately 30-minute IV infusion via a peripheral vein or central venous catheter with in-line filter. Backbone Chemotherapy Regimen:

[0265] Administration of mFOLFOX6 chemotherapy will commence on Day 1 of each treatment cycle and after administration of anti-FGFR2-IIIb (following a 30-minute rest). The mFOLFOX6 regimen is administered every 2 weeks 33 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 as follows:

[0266] Oxaliplatin 85mg / m2 IV infusion over 120minutes, leucovorin 400mg / m2 IV infusion over 120minutes, followed by fluorouracil (5-FU) 400 mg / m2 IV bolus, followed by 5-FU 2400 mg / m2 as a continuous IV infusion over 46 hours.

[0267] The administration of oxaliplatin does not require pre-hydration. Premedication with anti-emetics, such as serotonin antagonists with or without dexamethasone, may be used where clinically indicated at the discretion of the Investigator per local standard of care. Dose Levels (Part 1)

[0268] In Part 1, two dose cohorts of anti-FGFR2-IIIb are anticipated in a standard 3+3 dose escalation design, with a minimum of 3 patients enrolled into each cohort. The anticipated dose levels are: Dose Level 1 10 mg / kg anti-FGFR2-IIIb Dose Level 2 15 mg / kg anti-FGFR2-IIIb Dose Level ‑1 6 mg / kg anti-FGFR2-IIIb (if dose reduction is required from starting Dose Level 1)

[0269] All dose escalation decisions will be based on an assessment of DLTs, overall safety, and tolerability, and will be madeafter the lastpatientenrolled ineachcohort hascompleted the28-dayDLTPeriod (completionof2 treatment cycles). Dose escalation decisions will be agreed upon by the Cohort Review Committee (CRC), consisting of the Sponsor and Investigators. Review of safety and PK parameters may inform decisions to add cohorts with alternative dose levels in order to reach an optimal target exposure. Dose Level ‑1 will only be enrolled if ≥ 2 DLTs are observed at Dose Level 1.

[0270] The algorithm shown in Table 2 will be used for Part 1 dose escalation decisions: Table 2. Dose Escalation Number of Patients with DLTs Action 0 / 3 Open next cohort 1 / 3 Enroll 3 more patients in same cohort ≥ 2 / 3 Stop enrollment. Enter 3 more patients at dose level below, if only 3 were pre- viously entered 1 / 6 Open next cohort ≥ 2 / 6 Stop enrollment. Enter 3 more patients at dose level below, if only 3 were pre- viously entered to demonstrate that ≤ 1 of 6 patients experience DLT

[0271] The RD of anti-FGFR2-IIIb for Part 2 will be identified by the CRC based on an evaluation of the overall safety, tolerability, and PK. The RD, therefore, may or may not be the same as the identifiedmaximum tolerated dose (MTD). For example, if theMTD is not reached, or if data from subsequent cycles of treatment fromPart 1 provide additional insight on the safety profile, then the RD may be a different, though not higher, dose than the MTD.

[0272] TheMTD isdefinedas themaximumdoseatwhich<33%ofpatients experienceaDLTduring theDLTPeriod. If a DLT is observed in 1 of 3 patients at a given dose level, then 3 additional patients will be enrolled at that same dose level. Doseescalationmaycontinueuntil 2 of 3 to 6patients treatedat a dose level experienceaDLT (dose level not toexceed15 mg / kg). The next lower dose will then be considered the MTD.

[0273] Once theMTDorRDhasbeen reached, 3additional patientswill beadded, to further explore the safetyandPKat this dose level. The total enrollment for Part 1 will, therefore, be approximately 9 to 12 patients.

[0274] Any patient who does not receive exactly 2 doses of anti-FGFR2-IIIb in combination withmFOLFOX6 during the DLT Period will be considered unevaluable and the patient will be replaced. The replaced patient may continue on study after discussion with the Sponsor. No more than 2 doses of anti-FGFR2-IIIb or 2 cycles of mFOLFOX6 should be administered during the 28-day DLT Period.

[0275] On completion of the DLT Period, patients may continue receiving anti-FGFR2-IIIb in combination with mFOLFOX6, administered every 2 weeks in 14-day cycles until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or until the patient meets any of the other protocol-specified withdrawal criteria. There is nomaximum number of doses of anti-FGFR2-IIIb. Ongoing administration of themFOLFOX6 regimen beyond the DLT Period will be according to regional standard of care.

[0276] In the case of discontinuation of mFOLFOX6 chemotherapy administration for any reason prior to disease 34 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 progression (e.g., cumulative toxicity or completion of mFOLFOX6 chemotherapy per regional practice), anti-FGFR2-IIIb may be continued as monotherapy and administered every 2 weeks until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or until the patient meets any of the other protocol-specified withdrawal criteria. In the event a cycle of mFOLFOX6 is delayed beyond 14 days due to chemotherapy-related toxicity, anti-FGFR2- IIIb administration should not be delayed and may continue to be administered every 2 weeks. Initiation of a new cycle of mFOLFOX6 following a dosing delay should be synchronized with administration of an anti-FGFR2-IIIb infusion where possible (but is not a study requirement).

[0277] In the case of discontinuation of anti-FGFR2-IIIb for any reason prior to disease progression (e.g., cumulative toxicity), mFOLFOX6 chemotherapy may continue to be administered in accordance with local regional practice, or until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or the patient meets any of the other protocol-specified withdrawal criteria. Part 2: Randomized, Double-Blind Dose Expansion

[0278] Patients will be enrolled into Part 2 with the objective of characterizing the safety and efficacy of anti-FGFR2-IIIb combined with mFOLFOX6 compared to placebo and mFOLFOX6 in an FGFR2b-selected gastric cancer patient population. Enrollment into Part 2 will begin only once an RD for anti-FGFR2-IIIb, which will not exceed 15 mg / kg, has been identified by the CRC in Part 1.

[0279] Part 2 is double-blind and will consist of a total of up to approximately 360 FGFR2b-selected gastric cancer patients randomized 1:1 to receive one of two treatment arms: Arm 1: anti-FGFR2-IIIb at the RD and mFOLFOX6 administered every 2 weeks; or Arm 2: Placebo and mFOLFOX6 administered every 2 weeks Opening of Part 2 for enrollment will be at the discretion of the Sponsor.

[0280] Patients with gastric cancer with unresectable, locally advanced, or metastatic disease who are eligible for first- linemFOLFOX6chemotherapyandhave received2 cycles ofmFOLFOX6will be enrolled intoPart 2 of the study.Patients will be selected for enrollment based on FGFR2b overexpression and / or FGFR2 amplification, as determined by a validated IHC or blood-based biopsy assay, respectively.

[0281] Enrolled patients may continue treatment every 2 weeks in 14-day cycles until Investigator-assessed radio- graphic or clinical disease progression, unacceptable toxicity, or until the patientmeets any of the other protocol-specified withdrawal criteria. All treatment decisionswill bemade by the Investigator using local assessments. After discontinuation of study treatment for reasons other than progression or withdrawal of consent, tumor assessments will continue until the patient initiates additional anti-cancer therapy. In addition, patients in both Part 1 and Part 2 will undergo long-term follow- up for survival by clinic visit or by telephone approximately every 3 months ± 28 days after the EOT visit until up to 24 months after the last patient is enrolled into the study, or until death, loss to follow-up, withdrawal of consent or study termination by the Sponsor (whichever occurs first).

[0282] In the case of discontinuation of mFOLFOX6 chemotherapy administration for any reason prior to disease progression (e.g., cumulative toxicity or completion of mFOLFOX6 chemotherapy per regional practice), IP may be continued as monotherapy and administered every 2 weeks until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or until the patient meets any of the other protocol-specified withdrawal criteria. In the event a cycle ofmFOLFOX6 is delayed beyond14days due to chemotherapy-related toxicity, IP administration should not be delayed andmay continue to be administered every 2weeks. Initiation of a newcycle ofmFOLFOX6 following a dosing delay should be synchronized with administration of an IP infusion where possible (but is not a study requirement).

[0283] In the case of discontinuation of IP for any reason prior to disease progression (e.g., cumulative toxicity), mFOLFOX6 chemotherapy may continue to be administered in accordance with local regional practice, or until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or the patient meets any of the other protocol-specified withdrawal criteria. Study Schema

[0284] The study schema is shown in Fig. 1 (Part 1) and Fig. 2 (Part 2). Rationale for the Study Design

[0285] This is a2-part,multicenter study to evaluate the safety, tolerability, PK,PD,andefficacyof anti-FGFR2-IIIbwhen given in combination with mFOLFOX6. The study will include an open-label, Part 1 dose escalation safety run-in and a randomized, double-blind, placebo-controlled, Part 2 dose expansion. 35 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55

[0286] Part 1 is a dose-escalation safety run-in study of anti-FGFR2-IIIb when given in combination withmFOLFOX6. A standard 3+3 design will be used. Patients enrolled into Part 1 will be treated with escalating doses of anti-FGFR2-IIIb in combination with a fixed-dose backbone chemotherapy regimen of mFOLFOX6 every 2 weeks in 14-day cycles. Each patient enrolled into Part 1 will be observed for 28 days for safety assessments and occurrence of dose-limiting toxicities (DLT Period) and an RD will be selected for Part 2 after assessing the data.

[0287] Patients eligible for Part 1 have unselected GI cancer (with or without FGFR2b overexpressing tumors) with unresectable, locally advanced, or metastatic disease, and are candidates to receive both anti-FGFR2-IIIb and mFOL- FOX6 chemotherapy. FGFR2 status will be determined retrospectively by IHC and blood-based biopsy.

[0288] In Part 2, selected patientswill be randomized 1:1 to be treatedwith anti-FGFR2-IIIb andmFOLFOX6or placebo andmFOLFOX6 every 2 weeks in 14-day cycles. Patients in Part 2 must have completed exactly 2 cycles of mFOLFOX6 (no more and no less).

[0289] Measuring the PFS,ORR, andOS in patients with FGFR2b-selected gastric cancer in randomized patientsmay highlight the clinical benefit of anti-FGFR2-IIIb when given in combination with mFOLFOX6 compared to placebo and mFOLFOX6. Study Eligibility and Withdrawal Criteria Planned Number of Patients and Study Centers

[0290] In Part 1, 2 dose cohorts of anti-FGFR2-IIIb are anticipated in a standard 3+3 dose escalation design, with a minimum of 3 patients enrolled into each cohort. Once the MTD or RD has been reached, 3 additional patients will be added, to further explore the safety and PK at this dose level. The total enrollment for Part 1 will, therefore, be approximately 9 to 12 patients.

[0291] In Part 2, up to approximately 360 FGFR2b-selected gastric cancer patients will be randomized 1:1 to be treated with anti-FGFR2-IIIb in combinationwithmFOLFOX6or placebo in combinationwithmFOLFOX6every 2weeks in 14-day cycles at an RD selected after assessment of data obtained in Part 1. Opening of Part 2 for enrollment will be at the discretion of the Sponsor.

[0292] The total enrollment planned for this study is approximately 372 patients.

[0293] The study will be conducted at up to 250 global study centers. Inclusion Criteria for All Cohorts

[0294] Patients enrolling into either Part 1 or Part 2 of the study must meet all of the following inclusion criteria: 1) Disease that is unresectable, locally advanced, or metastatic 2)Understandand sign an InstitutionalReviewBoard (IRB) / Independent EthicsCommittee (IEC)‑approved informed consent form (ICF) prior to any study-specific evaluation 3) Life expectancy of at least 3 months 4) Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1 5) Age ≥18 years at the time the ICF is signed 6)Negative serum β-human chorionic gonadotropin (β-hCG) pregnancy test ≤ 72 hours prior to enrollment (women of childbearing potential only) 7) In sexually active patients (women of child bearing potential and males), willingness to use 2 effective methods of contraception, ofwhich 1must beaphysical barriermethod (condom, diaphragm, or cervical / vault cap) until 6months after the last dose of anti-FGFR2-IIIb. Other effective forms of contraception include: • Permanent sterilization (hysterectomy and / or bilateral oophorectomy, or bilateral tubal ligation with surgery, or vasectomy) at least 6 months prior to Screening • Women of childbearing potential that are on stable oral contraceptive therapy or intrauterine or implant device for at least 90 days prior to the study, or abstain from sexual intercourse as a way of living 36 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 8) Adequate hematological and biological function, confirmed by the following laboratory values: • Bone Marrow Function • Absolute neutrophil count (ANC) ≥ 1.5 × 109 / L • Platelets > 100 × 109 / L • Hemoglobin ≥ 9 g / dL • Hepatic Function • Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 3× upper limit of normal (ULN); if liver metastases, then ≤ 5 × ULN • Bilirubin ≤ 1.5 × ULN • Renal Function • Calculated creatinine clearance ≥ 50 mL / min 9) Patients on full-dose anticoagulants must be on a stable dose of warfarin and have an in-range international normalized ratio (INR) within the therapeutic range for the patient’s condition or be on a stable dose of lowmolecular weight heparin 10)Measurable or non-measurable disease 11) Tumor tissue for determination of FGFR2 status Patients enrolling into Part 1 (Dose-Escalation Safety Run-in) of the study must also meet the following inclusion criteria:

[0295] Histologically or cytologically confirmed gastrointestinal malignancy for which mFOLFOX6 is considered an appropriate treatment (e.g., gastric cancer, colorectal carcinoma, pancreatic adenocarcinoma)

[0296] Nomore than 2 prior chemotherapy regimens formetastatic disease (not including prior adjuvant chemotherapy with 5-FU and / or oxaliplatin).

[0297] Patient must be a candidate for at least 2 cycles of mFOLFOX6 chemotherapy. Patients enrolling into Part 2 (Dose-Expansion) of the study must also meet the following inclusion criteria:

[0298] 1) Histologically documented gastric or gastroesophageal junction adenocarcinoma 2) FGFR2b overexpression as determined by IHC and / or FGFR2 amplification as determined by blood-based biopsy 3) No prior chemotherapy for metastatic or unresectable disease (except as noted in Inclusion Criteria #20 for mFOLFOX6) 4) No prior platinum-based chemotherapy (except as noted in Inclusion Criteria #20 for mFOLFOX6) 5) If prior adjuvant or neo-adjuvant therapy (chemotherapy and / or chemoradiation) has been received, more than 6 months must have elapsed between the end of adjuvant therapy and enrolment 6) Patient must be a candidate for mFOLFOX6 chemotherapy and have received 2 cycles of mFOLFOX6 che- motherapy prior to study enrollment (but not more than 2 cycles) 37 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Exclusion Criteria for All Cohorts

[0299] Patients enrolling into either Part 1 or Part 2 will be excluded if any of the following criteria apply: Untreated or symptomatic central nervous system (CNS) metastases. Patients with asymptomatic CNS metastases are eligible provided they have been clinically stable for at least 4 weeks and do not require intervention such as surgery, radiation, or any corticosteroid therapy for management of symptoms related to CNS disease

[0300] Impaired cardiac function or clinically significant cardiac disease, including any of the following: • Unstable angina pectoris ≤6 months prior to enrollment • Acute myocardial infarction ≤6 months prior to enrollment • New York Heart Association class II-IV congestive heart failure • Uncontrolled hypertension (as defined as > 160 / 90 despite optimal medical management) • Cardiac arrhythmia requiring anti-arrhythmic therapy other than beta blockers or digoxin • Active coronary artery disease 7) QTcF > 450 msec for males or > 470 msec for women 8) Peripheral sensory neuropathy ≥ Common Terminology Criteria for Adverse Events (CTCAE) grade 2 9) Active infection requiring systemic treatment or any uncontrolled infection ≤ 14 days prior to enrollment 10)Known human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS)‑related illness, or history of chronic hepatitis B or C 11) History of interstitial lung disease (e.g., pneumonitis or pulmonary fibrosis) 12) Evidence or history of bleeding diathesis or coagulopathy 13) Any investigational agent or therapy ≤28 days prior to enrollment 14)Radiotherapy ≤ 28 days of enrollment. Patients must be recovered from all radiotherapy-related toxicities. No radiopharmaceuticals (strontium, samarium) within 8 weeks of enrollment 15) Prior treatment with any selective inhibitor (e.g., AZD4547, BGJ398, JNJ‑42756493, BAY1179470) of the FGF- FGFR pathway 16) Ongoing adverse effects from prior treatment > NCI CTCAE Grade 1 (with the exception of Grade 2 alopecia) 17) Participation in another therapeutic clinical study within 28 days of enrollment or during this clinical study 18) Corneal defects, corneal ulcerations, keratitis, keratoconus, history of corneal transplant, or other known abnormalities of the cornea that may, in the opinion of an ophthalmologist, pose a risk with anti-FGFR2-IIIb treatment 19)PositiveHER2status (asdefinedbyapositive IHC test of 3+or IHCof2+withpositiveFISH).HER2status isbased on scoring guidelines for gastric cancer (HercepTest). 20) Major surgical procedures are not allowed ≤28 days prior to enrollment. Surgery requiring local / epidural anesthesia must be completed at least 72 hours before enrollment. In all cases the patient must be sufficiently recovered and stable before treatment administration 21) Women who are pregnant or breastfeeding (unless the patient is willing to interrupt breastfeeding during study drug administration and then resume6months after study discontinuation); women of childbearing potential must not consider getting pregnant during the study 38 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 22) Presence of any serious or unstable concomitant systemic disorder incompatible with the clinical study (e.g., substance abuse, psychiatric disturbance, or uncontrolled intercurrent illness including active infection, arterial thrombosis, and symptomatic pulmonary embolism) 23) Presence of any other condition that may increase the risk associated with study participation (e.g., dihydropyr- imidine deficiency or pleural effusion) ormay interferewith the interpretation of study results, and, in the opinion of the Investigator, would make the patient inappropriate for entry into the study 24) Known allergy or hypersensitivity to components of the anti-FGFR2-IIIb formulation including polysorbate or to platinum-containing medications, fluorouracil, or leucovorin 25) History of prior malignancy except another malignancy that in the Investigator’s opinion would not affect the determination of study treatment effect

[0301] No waivers of these inclusion or exclusion criteria will be granted. Patient Withdrawal and Replacement

[0302] A patient must be discontinued from protocol-prescribed therapy if any of the following apply: • Consent withdrawal at the request of the patient or their legally authorized representative • Progression of patient’s disease as assessed by the Investigator. • Any event that would pose an unacceptable safety risk to the patient • A concurrent illness that would affect assessments of the clinical status to a significant degree • A positive pregnancy test at any time during the study • At the specific request of the Sponsor or its authorized representative (e.g., if the study is terminated for reasons of patient safety) Patient Identification and Enrollment

[0303] Patientsmust beable toprovidewritten informedconsentandmeetall inclusioncriteria andnoneof theexclusion criteria. Nowaivers of inclusion or exclusion criteria will be granted by the Investigator and Sponsor or its designee for any patient enrolled in the study.Before enrolling a patient, all eligibility criteriamust be satisfied.Patientswhoqualify forPart 1 of the study will be enrolled into the first available cohort. A patient may be enrolled into either Part 1 or Part 2 of the study, but not both.

[0304] In Part 2, patients first undergo Pre-screening in which both a blood-based biopsy assay and a tissue test are required. Patients who are determined to be FGFR2 positive may immediately enter the Screening Period (i.e., patients withpositiveblood test resultsneednotwait for IHCresults (seeTable3).Patients inPart 2mustalsohavecompleted2,but not more than 2, cycles of mFOLFOX6. Table 3: Eligibility Based on FGFR2b Results FGFR2 Amplificationa (using a blood-based biopsy [ctDNA] assay)b IHC FGFR2B Overexpression (using a tissue based IHC Assay)a (tissue test for FGFR2b protein)c Eligibil- ity Blood (+) Positive Eligible Blood (‑) Positive Eligible Blood (+) Negative Eligible Blood (‑) Negative Ineligible a: Both tests will be carried out at central laboratories. b: Requires 2 x 10 mL c: IHC: Minimum of 5 slides required. A score of 2+ or 3+ will be considered positive.

[0305] In both Parts 1 and 2, the Investigator may repeat qualifying laboratory tests and vital signs / ECGs prior to enrollment if a non-qualifying finding is considered an error or an acute finding is likely to meet eligibility criteria on repeat testing. Hematology and blood chemistry test results must be obtained within 72 hours of dosing to confirm eligibility. 39 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Study Drug Identity

[0306] In Part 1, anti-FGFR2-IIIb will be supplied in a sterile vial for dilution into an intravenous bag for administration by the study site over approximately 30minutes every 14days (+ / ‑3days) until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or other cause for protocol-specified study withdrawal.

[0307] In Part 2, placebo will be supplied by an unblinded site pharmacist. Participants will be randomly assigned in a [1:1] ratio to receiveblinded IP (anti-FGFR2-IIIb / placebo). Investigatorswill remain blinded toeachparticipant’s assigned study treatment throughout the course of the study. In order to maintain this blind, the unblinded pharmacist will be responsible for the reconstitution and dispensation of all study treatment. In the event of a Quality Assurance audit, the auditor(s)will beallowedaccess to unblindedstudy treatment recordsat the site(s) to verify that randomization / dispensing has been done accurately.

[0308] Oxaliplatin, 5-FU, and leucovorin will be supplied to each site as per routine institutional practice. The mFOLFOX6 regimen will be administered every 14 days (+ / ‑ 3 days) until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or other cause for protocol-specified study withdrawal. Refer to the most current regional package insert for preparation and complete prescribing information. Administration 1. mFOLFOX6

[0309] Oxaliplatin, 5-FU, and leucovorin will be supplied to each site as per routine institutional practice. The mFOLFOX6 regimen will be administered every 14 days (+ / ‑ 3 days) until disease progression, unacceptable toxicity, or other cause for protocol-specified study withdrawal.

[0310] Thestarting dose formFOLFOX6 includes 85mg / m2of oxaliplatin, 350mgof calcium folinate (folinic acid), a 400 mg / m2 dose of fluorouracil, and a 2400 mg / m2 dose of fluorouracil. Oxaliplatin and calcium folinate are administered concomitantly via IV infusion using a 3-way tap / Y-site connector. The smaller dose of fluorouracil is administered via IV bolus, and the larger dose of fluorouracil is administered via IV infusion over the course of 46 hours. mFOLFOX6may be administered every 14 days.

[0311] Refer to the most current package insert for preparation and complete prescribing information. 2. Open-label anti-FGFR2-IIIb (Part 1) and Blinded IP (Part 2)

[0312] Anti-FGFR2-IIIb will be administered only to patients in this study using procedures described in this protocol. The dose of anti-FGFR2-IIIb is based on body weight at Cycle 1 Day 1 and adjusted if the patient’s weight changes > 10% from Cycle 1 Day 1.

[0313] A pharmacist (or other responsible person) will prepare the solution for administration. After calculating the number of vials, based on the patient’s weight, the study drug product will be diluted in a 0.9% sodium chloride solution. Prepared anti-FGFR2-IIIb should be administered ≤8 hours after preparation (ambient temperature). Anti-FGFR2-IIIb will be administeredundermedical supervision over approximately 30-minute IV infusionwith in-line filter via a peripheral vein or central venous catheter. For Part 2, the pharmacist, whowill be unblinded to treatment assignment, will supply placebo.

[0314] Infusion of anti-FGFR2-IIIb must be stopped, reduced, interrupted, or discontinued earlier. If a patient experi- ences an infusion reaction, the patient’s vital signs (temperature, blood pressure, pulse, and respiration rate) should be monitored during the infusion aswell as every 30minutes after the infusion for aminimumof 2 hours and until resolution of the infusion reaction.

[0315] Patientswill receive 2doses of anti-FGFR2-IIIb, 2weeks apart for the duration of study participation. In Part 1, on completion of the DLT period if treatment is tolerated without disease progression, patients may continue receiving anti- FGFR2-IIIb in combination with mFOLFOX6, administered every 2 weeks in 14-day cycles until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or until the patient meets any of the other protocol- specified withdrawal criteria. Starting Dose and Dose Modifications 3. Part 1: Dose-Escalation Safety Run-in

[0316] Patients enrolled into Part 1 will be treated with escalating doses of anti-FGFR2-IIIb in combination with a fixed- dose backbone chemotherapy regimen of mFOLFOX6 every 2 weeks in 14-day cycles, as described above. 40 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Dose Modification Criteria 4. Open-label anti-FGFR2-IIIb (Part 1) and Blinded IP (Part 2)

[0317] Part1andPart2:Dose reductions foranti-FGFR2-IIIbmaybepermitted forpatientson treatmentbeyond theDLT Period in Part 1 or any patient in Part 2 per the guidelines outlined in Table 4. If dose reductions or interruptions that do not fall within these guidelines are being considered by the Investigator, thesewill require discussionwith and approval by the Sponsor or designee. Table 4: Dose Modification Guidelines for anti-FGFR2-IIIb Toxicity Grade Anti-FGFR2-IIIb Dose Dose Schedule 1 or 2 Continue 100% of dose No delay or missed dose re- quired 3 or 4 (first occurrence) Continue 100% of starting dose following recovery to Baseline or Grade 1 Delay or miss dose 3 or 4 (second occurrence) Continue at one dose level lower than previous dose following recovery to Baseline or Grade 1 Delay or miss dose 3 or 4 (third occurrence) Permanently discontinue dosing of anti-FGFR2-IIIb N / A

[0318] Patientsmay resume thestudydrug if theevent returns toBaselineor≤Grade1 inaccordancewith theguidelines outlined in Table 4.

[0319] There is a± 3-daywindow for the scheduled dosing visits. Patients should not have 2 consecutive doses of anti- FGFR2-IIIb within 7 days. The first dose of each cycle is considered Day 1 of each cycle. Cycles will repeat every 14 days unless there is a treatment delay.

[0320] Intra-patient dose escalation above the starting dose for each patient will not be permitted. If a patient’s dose is decreased for a reason that is no longer relevant, dose escalation to the originally assigned dose may occur after discussion and approval by the Sponsor. 5. mFOLFOX6

[0321] Part 1 and Part 2: Patients should be closely monitored for mFOLFOX6 toxicity. Dose adjustments for 5-FU and oxaliplatin may be permitted for patients on treatment, but patients who require dose adjustments or delay of any component of mFOLFOX during the DLT period will not be considered evaluable unless the dose adjustment or delay is due to an AE deemed related to anti-FGFR2-IIIb, in which case the AE will be considered a DLT (see below for DLT definition). Beyond theDLTPeriod inPart 1 or anypatient inPart 2, doseadjustments for any component ofmFOLFOXare permitted per the guidelines outlined in the protocol.

[0322] In the event that oxaliplatin administration is discontinued for any reason prior to disease progression, 5- FU / leucovorin therapy may continue on an every‑2-week schedule until disease progression, unacceptable toxicity, or other cause for study withdrawal.

[0323] Dose adjustments for mFOLFOX6 toxicity are shown in Table 5. 41 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Dose-Limiting Toxicity

[0324] DLTs are defined as any of the following events that occur during the first 28 days of treatment and are assessed by the Investigator as related to anti-FGFR2-IIIb. As applicable, events will be classified according to the NCI CTCAE (Version 4.03). • ANC<0.5 x 109 / L >5days duration or febrile neutropenia (i.e., ANC<1.0 x 109 / Lwith a single temperature of >38.3°C, or fever ≥38 °C for more than 1 hour). Use of G-CSF is permitted per institutional standards • Platelets <25 x 109 / L or platelets <50 x 109 / L with bleeding requiring medical intervention 42 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 • Prolonged (>7 days) Grade 3 thrombocytopenia • Grade 4 anemia (i.e., life-threatening consequences; urgent intervention indicated) • Any Grade 2 or greater ophthalmologic AE that does not resolve within 7 days • AST / ALT >3 x ULN and concurrent total bilirubin >2 x ULN not related to liver involvement with cancer • Any non-hematological AE Grade 3 or greater (except nausea, vomiting, and diarrhea if well controlled by systemic medication). Grade 3 or 4 lab values that are not of clinical significance per Investigator and Sponsor agreement will not be considered DLTs. • Any anti-FGFR2-IIIb related adverse event which results in a dose reduction or delay by at least 4 days of any component of mFOLFOX6 Recommended Dose (RD) and Maximum Tolerated Dose (MTD) Toxicity at Lowest Dose Level

[0325] If theMTD is unexpectedly exceededat the first dose level of anti-FGFR2-IIIb (10mg / kgQ2W), thendecisionson how to proceed will be based on safety, tolerability, and PK data; and will be agreed on between the Investigators and Sponsor.

[0326] Dose Level ‑1 (anti-FGFR2-IIIb 6 mg / kg Q2W; 3 to 6 subjects) will only be enrolled if ≥ 2 DLTs are observed at Dose Level 1. Dose Escalation within a Cohort

[0327] In Part 1, intra-patient dose escalation will not be permitted.

[0328] In Part 2, patients will be treated at the RD as determined from Part 1, and dose escalation will not be allowed. Dose Interruptions During Study Drug Infusion

[0329] Infusion of anti-FGFR2-IIIb must be stopped if any AE ≥Grade 3 occurs during the infusion. If bronchospasm or dyspnea occurs in a patient during infusion, the infusion should be stopped. Symptoms of infusion reactionsmay include: fever, chills, rigors, urticaria, hypotension and hypertension with headache, wheeze, breathlessness, hypoxia, and pulmonary infiltrates.

[0330] Inaddition, at the Investigator’sdiscretion, the infusion ratemaybe reducedor stopped if a less severeAE (Grade 1 or 2) occurs during the infusion. If a Grade 3 or less severe AE resolves within 4 hours, the infusion may be restarted at half the previous rate. If the same AE appears again with the same severity at any time during the restarted infusion, the infusion should be discontinued, and no further dosing of study drug will occur without consultation with the Sponsor or Sponsor’s designee.

[0331] If a patient experiences an infusion reaction prior to completion of the infusion, the infusionmust be stopped, and the patient should be promptly managed andmonitored according to signs and symptoms, and local clinical protocol until there is a complete resolution of the event. For patients whose infusion-associated events were either Grade 1 or 2, and completely resolved on the day of the infusion, the infusionmaybe resumedat the discretion of the Investigator at a slower rate with premedication. All subsequent infusions for that patient should then be administered at the reduced rate of infusion with pre-medications. Pre-medications may include medications such as corticosteroids, diphenhydramine, acetaminophen and / or bronchodilators as indicated. Anti-FGFR2-IIIb will be permanently discontinued for patients who have experienced Grade 3 or above infusion-associated adverse events, and for patients who have recurrent infusion- associated reactions after restarting the infusion despite pre-medications and slower infusion.

[0332] If a patient experiences an infusion reaction, the patient’s vital signs (temperature, blood pressure, pulse, and respiration rate) should bemonitored during the infusion, as well as every 30minutes after the infusion for aminimum of 2 hours and until resolution of the infusion reaction.

[0333] Dose interruptions and delays resulting frommFOLFOX6 toxicity are described in Table 5 (see product labels for leucovorin, 5-FU, and oxaliplatin). Parameters and Methods of Assessment 43 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Safety Parameters

[0334] Safety measures will include AEs, hematology, clinical chemistry, urinalysis, vital signs, body weight, conco- mitant medications / procedures, ECOG performance status, targeted physical examinations, ECGs, and ophthalmology examinations. 1.1 Tumor Analysis for Patient Selection 1.1.1 Part 1

[0335] Patients eligible for Part 1 have unselected GI cancer (with or without FGFR2b overexpressing tumors) with unresectable, locally advanced, or metastatic disease, and are candidates to receive both anti-FGFR2-IIIb and mFOL- FOX6 chemotherapy. FGFR2 status will be determined retrospectively by IHC and blood-based biopsy. 1. 1.2 Part 2

[0336] Patients in Part 2 of this studymust consent to tumor tissue analysis and blood sample analysis. Patients will be selected for enrollment based onFGFR2b overexpression and / orFGFR2 amplification, as determined by a validated IHC or blood-based biopsy assay, respectively. Patients who do not demonstrate either FGFR2b overexpression using IHC or amplification using a blood-based biopsy assaywill not be eligible for enrollment; however, positivity based on one or both of theassays isadequate tomeeteligibility requirements (e.g., positivebyblood-basedbiopsyassay, but negativeby IHC). It is the responsibility of each Investigator to obtain an adequate tumor specimen for analysis of FGFR2b overexpression for enrollment. Tumor slide or tumor block specimenprocessing, labeling, and shipping instructions are detailed in the Lab Manual that will be distributed with the specimen collection kit.

[0337] Third-party laboratorieswill perform theFGFR2bexpressionandFGFR2amplificationanalysis usinga validated IHC and blood-based assay, respectively.

[0338] For Part 2, once tumor and blood specimens are received, analysis will be performed as efficiently as possible, and results will be communicated back to the Investigator or designee. 1.2 Fresh Tumor Biopsies for Pharmacodynamic Analysis 1.2.1 Part 2 Only

[0339] Tumor biopsy samples are also being collected to evaluate the pharmacodynamic effect of anti-FGFR2-IIIb on the tumor microenvironment. These biopsy samples will be obtained before treatment and on-treatment to examine immune infiltrates andexpression of selected tumormarkers. Anoptional biopsymayalso beobtainedof tumors that have responded and / or progressed on or after treatment to understandmechanisms of resistance. Tumor biopsy samplesmay beassessed for theexpressionof immuneordisease-relatedgenesand / or proteins, aswell as for thepresenceof immune cell populations using a variety of methodologies including but not limited to IHC, qRT-PCR, genetic mutation detection, and fluorescent in situ hybridization (FISH). These samplesmay also undergoRNA sequencing to determine the effect of anti-FGFR2-IIIb on gene expression pathways aswell as identified gene expression signatures associatedwith response or resistance to response. These analyses may help predict future response to treatment. Other methods of tumor biomarker expression are also being evaluated.

[0340] A fresh biopsy at a primary tumor or metastatic tumor site is mandatory, as feasible, for up to 30 patients randomized intoPart 2 at Screening (at least 24 hours prior to dosing) and on treatmentwithin 7 days prior toCycle 3Day 1 (andat least 24hoursprior to dosing). For patientswhohavehadabiopsyacquiredwithin the 12weeksprior to enrollment, this sample may fulfill the requirement for a fresh pre-treatment biopsy provided adequate sample is available for PD analysis (a single paraffin-embedded block or approximately 10 slides).

[0341] Patients in Part 2 may also have an optional on-treatment biopsy upon documented tumor response, within 28 (±7)dayspost tumorassessment.Patients inPart 2mayalsohaveanoptional post-treatment biopsyat theEOTvisit upon documented tumor progression. In each case, consultation with the Sponsor should take place before the biopsy occurs. Both biopsies are optional.

[0342] The feasibilityof acquiringa fresh tumorsampleateach timepointwill beassessedby the Investigatorandshould include a consideration of patient safety. If the Investigator assesses that a biopsy is not feasible, then this determination must be recorded in the source documents.

[0343] Biopsied lesions may become inflamed, bleed, or change dimensions, which could result in inaccurate tumor measurements. Therefore, it is strongly recommendednot to use thebiopsied lesionasa target lesionwhenassessing the response by RECIST v 1.1 criteria. These biopsy samples should be excisional, incisional or core needle. Fine needle 44 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 aspirates or other cytology specimens are insufficient for downstreambiomarker analyses. Tumor tissue specimens in the form of a paraffin embedded block or unstained slides will be submitted for central IHC assessment. 1.3 Tumor Assessments

[0344] Tumor assessments should consist of clinical examination and appropriate imaging techniques (preferably CT scanswith appropriate slice thickness perRECISTv1.1); other assessments (MRI, radiograph, PET, and ultrasound)may be performed if required. The samemethods used to detect lesions at baseline are to be used to follow the same lesions throughout the clinical study. Screening tumor scan must be within 2 weeks of the start of treatment on Cycle 1 Day 1.

[0345] Tumor response assessment will be performed both by the Investigator and by blinded central radiology review per RECIST 1.1 guidelines.

[0346] Tumor scans will be performed at Screening (within 2 weeks of Cycle 1 Day 1 in Part 1 and Part 2) and within 7 days prior to the start of Cycle 4 Day 1, Cycle 7 Day 1, Cycle 10 Day 1, Cycle 13 Day 1, and then approximately every 12 weeks. If initial CR or PR is noted, confirmatory scans must be performed 4 to 6 weeks later.

[0347] After discontinuation of study treatment for reasons other than progression or withdrawal of consent, tumor assessments will continue until the patient initiates additional anti-cancer therapy or progresses. 1.3.1 Blood-based Biopsy (ctDNA)

[0348] In Part 1, samples for blood-based biopsy (ctDNA) assay will be collected prior to the first dose of study drug (Cycle 1 Day 1) and analyzed retrospectively for FGFR2 amplification.

[0349] In Part 2, a pre-screening blood-based biopsy (ctDNA) assay will be done. This sample will be analyzed prospectively for FGFR2 amplification. In addition, blood-based biopsy (ctDNA) assays will be collected longitudinally every 6 weeks from the first dose for 24 weeks, and then approximately every 12 weeks thereafter, and analyzed retrospectively for FGFR2 amplification. A sample will also be collected at the EOT visit for all Part 2 patients. 1.4 Pharmacodynamic Biomarker Analysis Using Hair Follicles

[0350] In Part 1 only, hair follicles (approximately 10, if available) from either eyebrows or scalp will be collected from all patients forwhomsampling ispossible.Hair folliclesare known toexpress theFGFR2b receptor andalterations in levels of FGFR2b and downstream signaling may be used to correlate the dose of anti-FGFR2-IIIb required to effectively block FGFR2b receptors and downstream signaling and may help provide guidance in choosing the RD for Part 2 of the study. 1.5 Pharmacodynamic Biomarker Analysis Using Blood

[0351] Serum samples for exploratory biomarker analysis of the FGFR pathway (for example: FGF7, FGF10) will be collected from all patients prior to dosing at the timepoints specified in Appendix 3. 1.6 Blood Sample for ctDNA 1.7 Pharmacodynamic Biomarker Analysis Using Tumor Biopsies

[0352] Levels of immune cell infiltrate and other exploratory biomarkers will be analyzed in pre-treatment and on- treatment tumor biopsy samples from all patients. 1.8 FCGR Polymorphisms

[0353] Blood samples are also collected for polymorphisms that frequently occur in Fc-gamma receptors, such as FCGR2A and FCGR3A. These genes express Fc gamma receptors on white blood cells that are an integral part of the ADCC pathway, which is an anticipated mechanism of action of anti-FGFR2-IIIb. The data will be collected for a retrospective analysis at the completion of the study to correlate patient response to anti-FGFR2-IIIb. These biomarker tests are considered exploratory. 1.9 Quality of Life Scales

[0354] The EQ‑5D‑5L quality of life (QoL) questionnaire and the EORTC QLQ-C30 will be administered on multiple occasions prior to dosing (see Appendix 1 for time points).

[0355] TheEQ‑5D‑5L questionnairewas developed by theEuroQolGroup, which is a standardizedmeasure to provide 45 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 utilities for clinical andeconomic appraisal. It usesadescriptive systemandavisual analoguescale (VAS).Thedescriptive system has 5 dimensions: mobility, self-care, usual activities, pain / discomfort and anxiety / depression, and each dimen- sion has 5 levels: no problems, slight problems, moderate problems, severe problems, and extreme problems.

[0356] Respondents are asked to indicate their health state bymarking the box against themost appropriate statement in each of the 5 dimensions. The digits for the 5 dimensions can be combined in a 5-digit number describing the respondent’s health state. Health states defined by the EQ‑5D‑5L descriptive system are converted into a single index value to calculate utilities. The VAS portrays the respondent’s self-rated health on a 20-cm vertical VAS, with endpoints labeled "the best health you can imagine" and "the worst health you can imagine".

[0357] The EuropeanOrganisation for Research and Treatment of Cancer (EORTC) quality of life questionnaire (QLQ) isan integratedsystem forassessing thehealth-relatedquality of life of cancerpatientsparticipating in international clinical trials. TheEORTCusesamodular approach toQoLassessment, consistingofa corequestionnaire (EORTCQLQ-C30) to be administered, if necessary with a module specific to tumor site, treatment modality or a QoL dimension (e.g., gastric cancer-specific module is QLQ-STO22).

[0358] The patient provides answers for five functional scales (physical, role, emotional, social, and cognitive), three symptom scales (fatigue, nausea and vomiting, and pain) and a global health status / QOL scale and six single items (dyspnea, insomnia, appetite loss, constipation, diarrhea, and financial difficulties). 1.10 ECOG Performance Status

[0359] ECOG performance status will be assessed in all patients at the time points outlined in Appendix 1. The ECOG performance status is a scale used to assess how a patient’s disease is progressing, assess how the disease affects the daily living abilities of the patient, and determine appropriate treatment and prognosis. The ECOG scale is shown in Appendix 4. 1.11 Pharmacokinetic Parameters

[0360] Blood samples to determine serum anti-FGFR2-IIIb concentration will be acquired from each patient as outlined in the Study Flowchart for Pharmacokinetic, Immunogenicity, and Pharmacodynamic Blood Sample Collections (Ap- pendix 3). 2. Study Conduct 2.1 Overview of Patient Assessments

[0361] The schedule of detailed patient assessments is shown in Appendix 1. The list of safety laboratory assessments is shown inAppendix 2. Instructions for the samplingandprocessingofPK,PD, and immunogenicity data areprovided in a flowchart in Appendix 3. 2.2 Study Assessments and Procedures by Visit 2.2.1 Pre-screening Period (Part 2 Only - Pre-study)

[0362] Written, signed informed consent (Pre-screening ICF) must be collected prior to any study-specific procedures. • Prospective IHC analysis of FGFR2b expression and a blood-based assay demonstrating FGFR2 amplification (see above). 2.2.2 Screening Period (Day ‑14 to Day 0)

[0363] Written, signed informed consent must be collected prior to any study-specific procedures. Patients who have fully consented to participation in the study will undergo screening assessments within 14 days (2 weeks) prior to administration of the first infusion of anti-FGFR2-IIIb. The following procedures will be performed: • Review / confirm eligibility criteria • Medical and disease history, including medication history • Tumor tissue collection from archive or newly obtained material (required for enrollment into Part 1 and Part 2) 46 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 • Demographic and baseline characteristics • Complete physical examination, including weight and height • ECOG performance status evaluation • Vital signs (blood pressure, pulse, respiration, and body temperature [°C]) • 12-lead ECG after 5 minutes of rest prior to recording • Comprehensive ophthalmologic examination • Safety blood tests (see Appendix 2.) • Serum pregnancy test (beta-human chorionic gonadotropin [β-HCG]), ≤ 72 hours prior, for women of childbearing potential • Urinalysis (includes dipstick for protein, glucose, blood, pH, and ketones) • Tumor assessments performed within 14 days prior to start of treatment and including clinical examination and appropriate imaging techniques, with other assessments (MRI, radiograph, PET, and ultrasound) performed if required • Randomization for Part 2 patients only • For up to 30 patients randomized into Part 2: Fresh tissue biopsy at primary or metastatic tumor site at least 24 hours prior to dosing. For patientswhohavehadabiopsyacquiredwithin the12weeksprior to enrollment, this sample may fulfill the requirement for a fresh pre-treatment biopsy provided adequate sample is available for PD analysis (a single paraffin-embedded block or approximately 10 slides). • Blood-based biopsy (ctDNA) sample collection as outlined in Appendix 3. • FOLFOXadministration (ForPart 1, patientsmay have initiatedmFOLFOX6chemotherapy prior to study enrollment, and must be a candidate for at least 2 cycles of mFOLFOX6 chemotherapy to be eligible. For Part 2, patients are required to have completed 2 cycles of mFOLFOX6 chemotherapy prior to randomization). • AE reporting, if applicable 2.2.3 Treatment Period 2.2.3.1 Cycle 1, Day 1

[0364] The following procedures will be performed: • Review / confirm eligibility criteria • Update medical, disease and medication history to capture any changes from screening • Limited physical examination including weight and oral exam • Patient reported outcomes (EQ‑5D‑5L and EORTC QLQ-C30) • Vital signs (blood pressure, pulse, respiration, and body temperature [°C]) pre-dose and at 0.5, 1, 2, and 4 hours from the start of anti-FGFR2-IIIb infusion • Safety blood tests, with results obtained within 72 hours prior to study drug administration to confirm eligibility (see Appendix 2.) 47 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 • Serum pregnancy test (β-HCG), ≤ 72 hours prior to dosing, for women of childbearing potential • Urinalysis (includes dipstick for protein, glucose, blood, pH, and ketones) • Blood sampling for PK, immunogenicity testing, FCGR, ctDNA, and exploratory biomarker analysis as outlined in Appendix 3. • Blood-basedbiopsy (ctDNA) sample collection: InPart 1,ablood-basedbiopsy (ctDNA) samplewill be collectedprior to dosing on Cycle 1 Day 1 for retrospective analysis. No sample is needed from Part 2 patients at this timepoint. • InPart 1 only, scalp or eyebrowhair follicle samples (approximately 10, if available) will be collected prior to dosing on Cycle 1 Day 1 from all patients for whom sampling is possible. • AE reporting • Review of concomitant medications

[0365] Study drug administration: • Anti-FGFR2-IIIb administered by IV infusion over 30 minutes • mFOLFOX6 chemotherapy administered after 30 minutes of rest 2.2.3.2 Cycle 1, Day 2

[0366] The following procedures will be performed: • Vital signs (blood pressure, pulse, respiration, and body temperature [°C]) measured pre-dose and at 0.5, 1, and 2 hours from the start of anti-FGFR2-IIIb infusion • Blood samples for PK and exploratory biomarker analysis will be collected as outlined in Appendix 3. • mFOLFOX6 administration continues • AE reporting • Review of concomitant medications 2.2.3.3 Cycle 1, Day 3

[0367] The following procedures will be performed: • Vital signs (blood pressure, pulse, respiration, and body temperature [°C]) measured pre-dose and at 0.5,1, and 2 hours from the start of anti-FGFR2-IIIb infusion • Blood sampling for PK analysis as outlined in Appendix 3. • mFOLFOX6 administration continues • AE reporting • Review of concomitant medications 2.2.3.4 Cycle 1, Day 8

[0368] The following procedures will be performed: • Limited physical examination including weight and oral exam 48 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 • Vital signs (blood pressure, pulse, respiration, and body temperature [°C]) measured pre-dose and at 0.5,1, and 2 hours from the start of anti-FGFR2-IIIb infusion • Safety blood tests, with results obtained within 72 hours prior to study drug administration (see Appendix 2.) • Blood sampling for PK analysis as outlined in Appendix 3. • AE reporting • Review of concomitant medications 2.2.3.5 Cycle 2 Day 1

[0369] The following procedures will be performed: • Limited physical examination including weight and oral exam • Vital signs (blood pressure, pulse, respiration, and body temperature [°C]) measured pre-dose and at 0.5,1, and 2 hours from the start of anti-FGFR2-IIIb infusion • Safety blood tests, with results obtained within 72 hours prior to study drug administration (see Appendix 2) • Blood sample for PK, immunogenicity testing, and exploratory biomarker analysis as outlined in Appendix 3 • AE reporting • Review of concomitant medications

[0370] Study drug administration: • Anti-FGFR2-IIIb administered by IV infusion over 30 minutes • mFOLFOX6 chemotherapy administered after 30 minutes of rest 2.2.3.6 Cycle 3 Day 1 and Day 1 of Subsequent Odd Cycles

[0371] On completion of the DLT Period, patients may continue receiving anti-FGFR2-IIIb in combination with mFOLFOX6, administered every 2 weeks in 14-day cycles until Investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or until the patient meets any of the other protocol-specified withdrawal criteria. There is nomaximum number of doses of anti-FGFR2-IIIb. Ongoing administration of themFOLFOX6 regimen beyond the DLT Period will be according to regional standard of care.

[0372] The following procedures will be performed: • Limited physical examination including weight and oral exam • ECOG performance status evaluation • Patient reported outcomes (EQ‑5D‑5L and EORTC QLQ-C30) • Vital signs (blood pressure, pulse, respiration, and body temperature [°C]) performed pre-dose and at 0.5,1, and 2 hours from the start of anti-FGFR2-IIIb infusion • Comprehensive ophthalmologic examination • Slit lampexaminationswithoutOCT for patients inPart 1and for patients inPart2 randomized to receiveanti-FGFR2- IIIbandFOLFOX6;every6weeksafterCycle2Day1 (prior toCycle3Day15,Cycle5Day1, andCycle6Day15), and then every 12weeks after Cycle 6Day15.Continue every 6‑8weeks if the patient has any persistent corneal findings. 49 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 • Safety blood tests, with results obtained within 72 hours prior to study drug administration (see Appendix 2) • Urine pregnancy test, ≤ 72 hours prior to dosing, for women of childbearing potential • Urinalysis (includes dipstick for protein, glucose, blood, pH, and ketones) • Tumor assessments performed within 7 days of Cycle 3 Day 1 and including clinical examination and appropriate imaging techniques, with other assessments (MRI, radiograph, PET, and ultrasound) performed if required • A freshbiopsyat a primary tumorormetastatic tumor site ismandatory, as feasible,within 7daysprior toCycle 3Day1 (and at least 24 hours prior to dosing) for only up to 30 patients randomized into Part 2. • Blood sampling for PK, immunogenicity testing, blood-based biopsy (ctDNA), and exploratory biomarker analysis as outlined in Appendix 3. • For Part 2 only, a blood-based biopsy (ctDNA) sample will be collected prior to treatment • Scalp or eyebrow hair follicle samples (~10, if available) • AE reporting • Review of concomitant medications

[0373] Study drug administration: • Anti-FGFR2-IIIb administered by IV infusion over 30 minutes on Day 1 of each cycle • mFOLFOX6 chemotherapy administered after dosingwith anti-FGFR2-IIIb onDay 1 of each cycle after 30minutes of rest. 2.2.3.7 Cycle 4 Day 1 and Day 1 of Subsequent Even Cycles

[0374] The following procedures will be performed: • Limited physical examination including weight and oral exam • Patient reported outcomes (EQ‑5D‑5L and EORTC QLQ-C30) • Vital signs (blood pressure, pulse, respiration, and body temperature [°C]) measured pre-dose and at 0.5,1, and 2 hours from the start of anti-FGFR2-IIIb infusion • Slit lampexaminationswithoutOCT for patients inPart 1and for patients inPart 2 randomized to receiveanti-FGFR2- IIIbandFOLFOX6;every6weeksafterCycle2Day1 (prior toCycle3Day15,Cycle5Day1, andCycle6Day15), and then every 12weeks after Cycle 6Day15.Continue every 6‑8weeks if the patient has any persistent corneal findings. • Safety blood tests, with results obtained within 72 hours prior to study drug administration (see Appendix 2) • Tumor assessments performed within 7 days prior to start of Cycle 4 Day 1 and including clinical examination and appropriate imaging techniques, with other assessments (MRI, radiograph, PET, and ultrasound) performed if required • For Part 2 only, a blood-based biopsy (ctDNA) sample will be collected prior to treatment • For Part 1, blood sample for PK ≤ 4 hours prior to dosing of anti-FGFR2-IIIb and at 15minutes (± 10minutes) after the end of the anti-FGFR2-IIIb infusion for subsequent cycles. For Part 2, PK samples to be collected (only for patients randomized to the anti-FGFR2-IIIb andmFOLFOX6 arm) ≤ 4 hours prior to dosing of anti-FGFR2-IIIb and 15minutes (± 10 minutes) after the end of the anti-FGFR2-IIIb infusion AE reporting 50 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 • AE reporting • Review of concomitant medications

[0375] Study drug administration: • Anti-FGFR2-IIIb administered by IV infusion over 30 minutes on Day 1 of each cycle • mFOLFOX6 chemotherapy administered after dosingwith anti-FGFR2-IIIb onDay 1 of each cycle after 30minutes of rest 2.2.4 End-of-Treatment Visit or Early Termination

[0376] Patients will return to the study center approximately 28 (± 3) days after the last study treatment administration, or in the event a patient discontinues prematurely from the study. The following assessmentswill be performed at theEnd- of-Study visit: • Limited physical examination including oral examination • ECOG performance status evaluation • Vital signs (sitting pulse, blood pressure, respiration, and body temperature [°C] after 5 minutes of rest) • 12-lead ECG after 5 minutes of rest • Comprehensive ophthalmologic examinations • Safety blood tests (see Appendix 2) • Urine pregnancy test, for women of childbearing potential • Urinalysis (includes dipstick for protein, glucose, blood, pH, and ketones) • Tumor scan, which can be omitted if the last scan was performed < 6 weeks prior to EOT visit or if tumor progression was previously determined • Blood sample for immunogenicity testing • For Part 2 only, a blood-based biopsy (ctDNA) sample will be collected • Scalp or eyebrow hair follicle samples (~10, if available) • Blood sample for PK for all patients in Part 1 and all patients receiving anti-FGFR2-IIIb in Part 2 • Blood sample for biomarker assessment • AE reporting • Review of concomitant medications

[0377] Note:After discontinuationof study treatment for reasonsother thanprogressionorwithdrawal of consent, tumor assessments will continue until the patient initiates additional anti-cancer therapy or progresses. 2.2.5 Long-term Follow-Up

[0378] • Patients in both Part 1 and Part 2 will undergo long-term follow-up for survival by clinic visit or by telephone 51 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 approximately every 3months± 28 days after the EOT visit until up to 24months after the last patient is enrolled into the study, or until death, loss to follow-up, withdrawal of consent or study termination by the Sponsor (whichever occurs first). • During the Follow-up Period, if the patient undergoes anti-cancer therapy, this should be documented. • During the first 6 months of the Follow-up Period, any pregnancy that occurs should be reported to the Sponsor. • Patients should be followed until death, loss to follow-up, withdrawal of consent, or study termination by the Sponsor. • Serious AEs occurring after the EOT visit should be reported to the Sponsor by the Investigator if the Investigator considers there is a causal relationship with the study drug. 3. Statistical Methods

[0379] Before database lock, a separate statistical analysis plan (SAP) will be finalized, providing detailed methods for the analysesoutlinedbelow.Anydeviations from theplannedanalyseswill be describedand justified in the final integrated study report. 3.1 Study Patients 3.1.1 Disposition of Patients

[0380] The number and percentage of patients entering and completing each phase (e.g., Screening, Cycle 1, and subsequent cycles if given) of the study will be presented. Reasons for withdrawal will also be summarized. 3.1.2 Protocol Deviations

[0381] A summary of the number and percentage of patients with major protocol deviations by type of deviation will be provided. Deviations will be defined in the SAP prior to database lock. 3.1.3 Analysis Populations

[0382] The following analysis populations are defined for the study: • Safety Population-all patients who have received any portion of at least one dose of anti-FGFR2-IIIb. • DLT-Evaluable Population-all patients enrolled into Part 1 of the study who received at least 2 doses of anti-FGFR2- IIIb and completed Cycle 1 of treatment, or who experienced a DLT in Cycle 1. • PK-EvaluablePopulation-all patientswhohave received at least one doseof anti-FGFR2-IIIb andhavehadadequate PKassessments drawn for determination of thePKprofile. Adequacywill be determined on a case-by-case basis and will be assessed prior to analysis of the blood samples. • Intent-to-Treat (ITT) Population - All enrolled patients • Efficacy-Evaluable Population-all patients whomet eligibility criteria, received at least 1 dose of anti-FGFR2-IIIb, and have at least 1 post-baseline disease assessment 3.2 General Considerations

[0383] The total enrollment planned for this study is up to approximately 372 patients. Up to approximately 12 patients evaluable for any DLT, per standard 3+3 design, will be enrolled into Part 1.

[0384] For Part 2, efficacy and tolerability will be examined by enrollment of up to approximately 360 patients with FGFR2b-selected gastric cancer, randomized 1:1 to receive anti-FGFR2-IIIb in combination with mFOLFOX6 or placebo in combination with mFOLFOX6. Eligible patients will be stratified according to geographic region (US and EU vs Asia vs Rest ofWorld), prior treatment status (denovo vs adjuvant / neo-adjuvant), andmeasurable disease status (measurable vs non-measurable). 52 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Power and Sample Size

[0385] This study is designed to provide adequate power for primary analysis of PFS.

[0386] Based on a mPFS for patients receiving placebo and mFOLFOX6 of 6 months, approximately 156 patients (randomized 1:1) with a target of 96 PFS events are required to demonstrate a hazard ratio (HR) of 0.5 for mPFS with a power of 90% (2-sided α =0.05) for the combination of anti-FGFR2-IIIb and mFOLFOX6 compared with placebo and mFOLFOX6 after 24 months of accrual and 6 months of follow up.

[0387] Assumingan exponential distribution of PFS, this corresponds to an increase inmedianPFS from6months to 12 months. In the current design, the minimum observed effect that would result in statistical significance for PFS is a 50% improvement (HR = 0.67) from 6 to 9 months.

[0388] This study is also powered for primary analysis of OS.

[0389] Based on a mOS for patients receiving placebo and mFOLFOX6 of 10 months, enrollment of the study will continue to up to approximately 360 patients with a target of 249 death events to demonstrate anHRof 0.7 for mOSwith a power of 80% at the overall type I error level of 0.05 for the combination of anti-FGFR2-IIIb andmFOLFOX6 compared to placebo and mFOLFOX6 after 36 months of accrual and 10 months of follow-up after enrollment of the last patient. The group sequentialmethodwill be used to allocate type I error rate based onO’Brien-Fleming boundary and type II error rate based on the Gamma family with parameter ‑4 at the interim and final analysis of OS.

[0390] Assuming an exponential distribution of OS, this corresponds to an increase of 43% in median OS from 10 months to 14.3 months. In the current design, the minimum observed effect that would result in statistical significance for OS at the final analysis is a 28% improvement (HR = 0.78) from 10 to 12.8 months.

[0391] Power and sample size estimates were estimated using EAST®(V6.4). 3.3 Demographics, Baseline Characteristics, and Concomitant Medications

[0392] Demographic data, medical history, concomitant disease, and concomitant medication will be summarized by cohort and overall. To determine whether the criteria for study conduct are met, corresponding tables and listings will be provided. These will include a description of patients who did not meet the eligibility criteria, an assessment of protocol violations, study drug accountability, and other data that may impact the general conduct of the study.

[0393] Baseline characteristics will be summarized for the safety population. Patients who died or withdrew before treatment started or do not complete the required safety observations will be described and evaluated separately. 3.4 Treatment Compliance

[0394] Treatment administration will be summarized by cohort including dose administration, dose modifications or delays, cumulative dose, average dose, number of infusions, and the duration of therapy. 3.5 Efficacy Analyses

[0395] In Part 1, all analyses will be descriptive and will be presented by dose group and overall as appropriate. Descriptive statistics will include number of observations, mean, standard deviation, median, range, and inter-quartile range for continuous variables, and the number and percent for categorical variables; 95% confidence intervals will be presented where appropriate. 3.5.1 Primary Efficacy Analysis

[0396] In Part 2, the primary efficacy analysis is the comparison of PFS in patients treated with anti-FGFR2-IIIb in combination with mFOLFOX6 or placebo and mFOLFOX6.

[0397] The primary endpoint, PFS, is defined as time from randomization until the date of radiologically confirmed progressive disease based on Investigator assessment (per RECIST v.1.1) or death from any cause, whichever comes first. The secondary efficacy endpoints include OS and ORR.

[0398] There will be an interim analysis and primary analysis for PFS and both are event-based analyses. Only futility test of PFS will be conducted at the interim analysis after 48 events (50% of target 96 PFS events for primary analysis of PFS) observed in the enrolled patients to exclude HR>0.806 for the combination of anti-FGFR2-IIIb and mFOLFOX6 compared with placebo andmFOLFOX6. It is estimated that the interim analysis will occur approximately 20months from the first patient enrolled.

[0399] The primary analysis of PFS will be conducted when at least 96 PFS events have been observed in the first 156 enrolled patients, and will be performed using the intent-to-treat (ITT) population.

[0400] Theprimary analysiswill include radiographic progression events as determinedby the Investigator perRECIST 53 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 v.1.1 and deaths.

[0401] The primary analysis of PFS will be conducted using a stratified log-rank 2-sided test with a 0.05 level of significance. The stratification factors will be the same used to stratify the randomization schedule as documented in the interactive voice and Web response system (IXRS).

[0402] If the p-value for the stratified log-rank test is statistically significant (< 0.05 two-sided) and the HR is < 1, the null hypothesis of no difference in PFS will be rejected and it will be inferred that PFS is statistically prolonged in the group receiving anti-FGFR2-IIIb in combination with mFOLFOX6 compared with the group receiving placebo andmFOLFOX6.

[0403] Themedian PFS and the associated 95% confidence interval for each treatment armwill be estimated using the Kaplan-Meier method. The hazard ratio (HR= λanti-FGFR2-IIIb+ mFOLFOX6 / λmFOLFOX6) will be estimated using a Cox regressionmodelwith treatment groupas theonlymain effect and stratifyingby the samestratification factors aswere used for the log-rank test. An unstratifiedHRwill also be presented. Analyses of secondary endpointOSwill be conducted when the primary endpoint, PFS, is statistically significant, and formal hypothesisOSwill be tested hierarchically at a level of 0.05. The type I error rate of testing primary and secondary endpoints will be in strong control by employing this fixed- sequence testing procedure at a level of 0.05. 3.5.2 Secondary Efficacy Analysis

[0404] Analyses of secondary endpoints including OS and ORR will be conducted when the primary endpoint, PFS, is statistically significant, and formal hypotheses ofOSandORRwill be tested hierarchically at a level of 0.05. TheOSwill be tested first and if it is significant, the ORR will be tested next. The type I error rate of testing primary and secondary endpoints will be in a control by employing this fixed-sequence testing procedure at a level of 0.05.

[0405] There will be an interim and final analysis for OS planned if the test for PFS is statistically significant. The interim analysis of OS will be conducted at the time of primary analysis of PFS. Should OS be analyzed, analysis of OS at the interim (i.e.,whenat least 96PFSeventshavebeenobserved), andat theend (i.e.,when249deathshavebeenobserved) will be performed on the ITT population.

[0406] The hypothesis testing of OS will be conducted using a stratified log-rank 2-sided test with a 0.05 level of significance. The group sequential method will be used to allocate type I error rate based on O’Brien-Fleming boundary and type II error rate basedon theGamma familywith parameter ‑4at the interimand final analysis ofOS. Thestratification factors will be the same used to stratify the randomization schedule as documented in the IXRS.

[0407] The median OS and the associated 95% confidence interval for each treatment arm will be estimated using the Kaplan-Meiermethod.TheHRwill beestimatedusingaCox regressionmodelwith treatment groupas theonlymaineffect and stratifying by the same stratification factors as were used for the log-rank test. An unstratified HR will also be presented.

[0408] TheORR is defined as the proportion of patients with partial or complete response as defined by the Investigator per RECIST v.1.1. The primary analysis of ORRwill be performed among the patients with baselinemeasurable disease. In the analysis of ORR, patients who don’t have any post-baseline adequate tumor assessments will be counted as non- responders. Formal hypothesis testing of ORRwill be performed using the stratified Cochran-Mantel-Haenszel test. The stratification factors will be the same used to stratify the randomization schedule as documented in the IXRS. 3.5.3 Exploratory Efficacy Analysis

[0409] The exploratory efficacy endpoints include duration of response in responding patients, 1-year OS rate, and change from baseline in QoL as measured by EQ‑5D‑5L and the EORTC QLQ-C30 for all enrolled patients.

[0410] Duration of response is defined, for patients with an objective response, as the time from first radiographic documentationof objective response todiseaseprogressionbyRECIST1.1or death due toanycause.Mediandurationof response and its associated 95% CI will be estimated, by treatment group, using Kaplan-Meier methods. The difference between treatment groups will be analyzed using a stratified log-rank test, using the same stratification that was used for randomization.

[0411] The1-yearOSrate, definedasproportionofpatientsaliveat1year,will beestimatedduring theanalysisofoverall survival using the Kaplan-Meier method. The variance of proportions will be estimated using Greenwood’s formula. The overall comparison for the difference in 1-year survival between the two treatment groups, will be calculated using the z- statistic where t =1 year.

[0412] For change from baseline in QoL as measured by EQ‑5D‑5L and the EORTCQLQ-C30, summary statistics for change from baseline will be presented at each post baseline assessment and at the End of Treatment. Differences between treatment groups will be analyzed using repeated measures analysis methods if applicable. 54 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Blinded Independent Review Committee (BIRC)

[0413] A BIRC will be established to assess the concordance between investigator’s assessment and BIRC’s assessment. A pre-specified audit plan will be included in an imagine charter, whereas the percentage of patients, identification of imaging subsets, criteria in auditing all images, and comparison between locally-reviewing and auditing PFS results will be described in detail. 3.6 Safety Analyses

[0414] The analyses of safety will include all patients who receive any study drug (anti-FGFR2-IIIb in combination with mFOLFOX6,orplaceboandmFOLFOX6) throughout thestudyandprovideanypost-treatment safety information.AllAEs will be coded using theMedical Dictionary for Regulatory Activities (MedDRA). The Investigator will classify the severity of AEs using the CTCAE v 4.03.

[0415] A treatment emergent adverse event (TEAE) is defined as any event with an onset date on or after date of first dose of study drug, or any event present before treatment that worsens after treatment. Only TEAEs with an onset date prior to date of last dose + 30 days will be tabulated in summary tables. The number and percentage of patients who experienceAEswill besummarizedbysystemorganclass,preferred term, relationship tostudydrug,andseverity for each treatment group. A by-patient listing will be provided for those patients who experience an SAE, including death, or experience an AE associated with early withdrawal from the study or discontinuation from study drug. Clinical laboratory data will be summarized by the type of laboratory test. The number and percentage of patients who experience abnormal (ie, outside of reference ranges) and / or clinically significant abnormalities after study drugadministrationwill be presented for each clinical laboratorymeasurement. For each clinical laboratorymeasurement, descriptive statisticswill be provided for baseline and all subsequent post-treatment scheduled visits. Changes from baseline to the posttreatment visits will alsobeprovided.Descriptive statistics of vital signswill also beprovided inasimilarmanner. Inaddition, shift frombaseline in CTCAE grade (where applicable) and by high / low flags (where CTCAE grades are not defined) will be presented by treatment group. No formal comparisons of safety endpoints are planned. 3.7 Pharmacokinetic Analyses

[0416] PK parameters will be estimated using non-compartmental analysis, though compartment analysis may be employed if appropriate. Individual andmean (±SD) serumanti-FGFR2-IIIb concentration-timedatawill be tabulated and plottedbydose level.Anti-FGFR2-IIIbPKparameterswill beestimated from theserumstudydrugconcentration-timedata using a non-compartmental analysis (NCA) method with intravenous infusion input. Alternative methods may be considered. Estimated individual and mean (±SD) PK parameters will be tabulated and summarized by dose level. Other descriptive statistics might be reported for serum anti-FGFR2-IIIb concentration-time data and estimated PK parameters. Dose proportionality, study drugaccumulation, and attainment of steady statewill be evaluated asdata allow.

[0417] The impact of immunogenicity on anti-FGFR2-IIIb exposure will be assessed. 3.8 Interim Analyses

[0418] Therewill bean interimanalysis forPFS,atwhichonlya futility test ofPFSwill beconducted, after 48events (50% of target 96 PFS events for primary analysis of PFS) observed in the first 156 enrolled patients, to exclude HR>0.806 in PFS for the combination of anti-FGFR2-IIIb and mFOLFOX6 compared with placebo and mFOLFOX6. In addition, there will be an interim analysis for OS planned if the test for PFS is statistically significant. The interim analysis of OS will be conductedat the timeofprimaryanalysis ofPFS.ShouldOSbeanalyzed, analysisofOSat the interimwill beperformedon the ITT population, and the type I error rate at the interim analysis is determined by implementing a Lan-DeMets O’Brien- Fleming alpha spending function depending on the fraction of information (death events) at the time of analysis.

[0419] In addition, safety data will be reviewed on a routine basis by the Sponsor and CROs’ Medical Monitors. During the dose escalation stage, the Medical Monitors and Investigator(s) will review safety data from each dose cohort prior to dose escalation or de-escalation. AE data from all cycles will be presented to the Medical Monitors when available. 3.9 Changes in the Planned Analyses

[0420] If discrepancies exist between the text of the statistical analysis as planned in the protocol and the final SAP, a protocol amendment will not be issued and the SAP will prevail. 55 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 References

[0421] Andre F, Ranson M, Dean E, Varga A, Van der Noll R, Stockman P, et al. Results of a phase I study of AZD4547, an inhibitor of fibroblast growth factor receptor (FGFR), in patients with advanced solid tumors. Proc AACR abstract, 2013:LB‑145. Brown A, Courtney C, King L, GroomS, GrazianoM. Cartilage dysplasia and tissuemineralization in the rat following administration of a FGF receptor tyrosine kinase inhibitor. Toxicol Pathol, 2005;33:449‑455. CunninghamD, Starling N, RaoS, et al. Capecitabine and oxaliplatin for advanced esophagogastric cancer. N Engl J Med. 2008 (358): 36‑46. Dienstmann R, Bahleda R, Adamo B et al. First-in-human study of JNJ‑42756493, a potent pan fibroblast growth factor receptor (FGFR) inhibitor in patients with advanced solid tumors. Proc AACR 2014: 5446 (abstract). Fuchs C, Tomasek J, Yong C, et al. 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Cancer Chemotherapy and Pharmacology. 2016 Aug 1;78(2):341‑51. Hecht J, Bang Y, Qin S, et al. Lapatinib in combination with capecitabine plus oxaliplatin in human epidermal growth factor receptor 2-positive advanced or metastatic gastric, esophageal, or gastroesophageal adenocarcinoma: TRIO‑013 / LOGiC - a randomized phase III trial. J Clin Oncol 2015; 34 (5):443‑451. Inoue M, Tsugane. Epidemiology of gastric cancer in Japan. Postgrad Med J. 2005; 81(957): 419‑424. Li J, Qin S, Xu J, et al. 2016. Randomized, double-blind, placebo-controlled phase III trial of Apatinib in patients with chemotherapy-refractory advanced or metastatic adenocarcinoma of the stomach or gastroesophageal junction. J Clin Oncol 2016; 34 (14):1448‑1454. Miki, T, Bottaro, DP, Fleming, TP et al. Determination of ligand-binding specificity by alternative splicing: Two distinct growth factor receptors encoded by a single gene. Proc. Natl. Acad. Sci. USA, 1992;89: 246‑250. National Cancer Institute. SEER Stat Fact Sheets: Esophageal Cancer 2015. Available from http seer (dot) cancer (dog) gov (slash) statfacts (slash) html (slash) esoph (dot) html. Accessed February 25, 2016. NaylorGM,GotodaT,DixonM,et al.WhydoesJapanhaveahigh incidenceofgastric cancer?Comparisonof gastritis between UK and Japanese patients. Gut. 2006; 55(11): 1545‑1552. Neugat AI, Hayek H, Howe G. Epidemiology of gastric cancer. Semin Oncol 1996;23:281‑91. Sequist LV, Cassier P, Varga A, et al. Phase I study of BGJ398, a selective pan FGFR inhibitor in genetically preselected advanced solid tumors. Proc AACR 2014: CT326 (abstract). Shinkawa T, Nakamura k, Yamane N, Shoji-Hosaka E, Kanda Yet al. The absence of fucose but not the presence of 56 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 galactose or bisecting N-acetylglucosamine of human IgG1 complex-type oligosaccharides shows the critical role of enhancing antibody-dependent cellular cytotoxicity. JBC, 2003; 278:3466‑3473. 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List of Abbreviations and Definitions Abbreviation Definition ADCC antibody-dependent cell-mediated cytotoxicity AE adverse event AIDS acquired immunodeficiency syndrome ALT alanine aminotransferase ANC absolute neutrophil count AST aspartate aminotransferase AUC area under serum concentration-time curve AUCτ AUC at time τ β-hCG β-human chorionic gonadotropin CHO Chinese hamster ovary CI confidence interval CL clearance Cmax maximum serum concentration CNS central nervous system CRC Cohort Review Committee CRO contract research organization CT computed tomography CTCAE Common Terminology Criteria for Adverse Events ctDNA circulating tumor DNA Ctrough trough serum concentration Ctrough ss trough concentration at steady state DLT dose-limiting toxicities DMC Data Monitoring Committee DOR duration of response DPD dipyrimidine dehydrogenase EAP etoposide / doxorubicin / cisplatin ECF epirubicin / cisplatin / 5-FU ECG electrocardiogram ECOG Eastern Cooperative Oncology Group 57 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 (continued) Abbreviation Definition eCRF electronic case report forms ELF etoposide / leucovorin / 5-FU ELISA enzyme linked immunosorbent assay EORTC European Organisation for Research and Treatment of Cancer EOT end of treatment eSAE electronic SAE reporting 5-FU 5-fluorouracil FAM 5-FU, 3 doxorubicin, and mitomycin C FAMTX 5-FU / doxorubicin [Adriamycin] / methotrexate) FGF fibroblast growth factor FGFR fibroblast growth factor receptor FISH fluorescent in situ hybridization FP 5-FU / cisplatin FRS2 FGF receptor substrate‑2 GC gastric cancer GCP Good Clinical Practices G-CSF granulocyte-colony stimulating factor GEJ gastroesophageal junction GI gastrointestinal GLP GLP Good Laboratory Practices HFc-G1 human IgG1 HIV human immunodeficiency virus HNSTD highest, non-severely toxic dose HR hazard ratio IB Investigator’s Brochure ICF informed consent form ICH International Conference on Harmonization ID identification IEC Independent Ethics Committee IHC immunohistochemistry IND investigational new drug INR international normalised ratio IP investigational product IRB Institutional Review Board IRC Independent Review Committee ITT intent-to-treat IV intravenous IXRS interactive voice and Web response system LLOQ lower limit of quantitation LV (remove) mFOLFOX6 modified FOLFOX (infusional 5-fluorouracil, leucovorin, and oxaliplatin) mOS Median OS MRI magnetic resonance imaging MTD maximum tolerated dose MTX (remove) NCA non-compartmental analysis NCI National Cancer Institute OCT ocular coherence tomography ORR objective response rate OS overall survival 58 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 (continued) Abbreviation Definition PD pharmacodynamic PET positron emission tomography PFS progression-free survival PK pharmacokinetic PRO patient reported outcomes Q2W twice weekly QLQ quality of life questionnaire QOL quality of life RD recommended dose RECIST Response Evaluation Criteria In Solid Tumors RPE retinal pigment epithelium SAE serious adverse event SAP statistical analysis plan SD standard deviation t1 / 2 terminal half-life TEAE treatment emergent adverse event TKI tyrosine kinase inhibitor TS thymidylate synthase ULN upper limit of normal VAS visual analogue scale 59 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Ta bl e 6: A nt i-F G FR 2- III b an tib od y Ph ar m ac ok in et ic Pa ra m et er Es tim at es (m ea n ± SD )U si ng N on -C om pa rt m en ta lA na ly si s fo rP at ie nt s En ro lle d in an ti- FG FR 2- III b an tib od y‑ 00 1 Pa rt 1 af te rF irs tD os e St ud y Pa rt D os e (m g / k g) # of Pa tie nt s in st ud y C m ax 1 (µ g / m L) C m ax 1 / D os e (µ g / m L / m g) C tr ou gh 1 (µ g / m L) A U C la st (d ay *u g / m L) A U C la st / D os e (d ay *µ g / m L) / m g) t½ (d ay ) 1A 0. 3 3 7. 96 ± 1. 15 0. 27 8± 0. 05 11 N C 28 .4 ± 9. 36 0. 97 6± 0. 26 5 2. 97 ± 0. 51 0 1 4 22 .2 ± 6. 13 0. 24 8± 0. 08 76 3. 57 ± 1. 07 a 11 5± 36 .2 1. 29 ± 0. 51 5 6. 01 ± 0. 64 6 3 3 71 .5 ± 18 .2 0. 31 2± 0. 06 54 12 .8 ± 2. 96 35 5± 82 .5 1. 55 ± 0. 29 0 8. 36 ± 0. 81 6 6 3 13 6± 17 .2 0. 28 7± 0. 02 79 19 .2 ± 3. 36 67 2± 83 .5 1. 43 ± 0. 23 7 6. 70 ± 0. 83 1 10 3 28 7± 7. 23 0. 41 0± 0. 03 21 43 .5 ± 23 .4 13 16 ± 34 0 1. 86 ± 0. 41 2 7. 80 ± 2. 44 15 3 39 3± 18 5 0. 38 5± 0. 14 9 56 .4 ± 31 .6 17 11 ± 31 0 1. 70 ± 0. 14 6 6. 08 b 1B 3 1 52 .5 0. 49 9. 22 N D N D N D 6 1 77 0. 23 2 21 .6 52 9 1. 59 11 .7 10 6c 16 3± 43 .5 0. 29 9± 0. 06 69 35 .3 ± 14 .5 88 5± 19 1 1. 65 ± 0. 40 6 6. 97 ± 3. 01 d N ot e: C m ax 1= m ax im um ob se rv ed se ru m co nc en tra tio n po st fir st do se ;C m ax 1 / D os e= C m ax 1 no rm al iz ed by do se ad m in is te re d; C tro ug h 1= O bs er ve d se ru m co nc en tra tio n at th e en d of th e fir st do se in te rv al ;A U C la st =a re a un de rt he ob se rv ed co nc en tra tin g- tim e cu rv e fro m th e tim e of do si ng to th e la st qu an tifi ab le co nc en tra tio n po st fir st do se ;A U C la st / D os e= AU C la st no rm al iz ed by do se ad m in is te re d; an d t 1 / 2 =t er m in al ha lf- lif e. N C = A su m m ar y st at is tic th at co ul d no tb e re po rte d as 2 ou to f3 pa tie nt s w ith C tro ug h 1 be lo w LL O Q ;N D =A PK pa ra m et er th at co ul d no tb e ac cu ra te ly de te rm in ed .a n= 3. D at a fro m 1 pa tie nt co ul d no tb e re po rte d be ca us e th e pa tie nt w as te rm in at ed w ith ou td at a on C 1D 15 fro m th e st ud y b n =2 .T er m in al ph as e w as ch ar ac te riz ed fo rl es s th an on e ha lf- lif e fo r1 of 3 pa tie nt s. Th er ef or e, th e da ta fo rt hi s pa tie nt w as ex - cl ud ed fro m su m m ar y st at is tic s fo rh al f-l ife as st ip ul at ed in th e da ta an al ys is pl an ;c O ne of 6 pa tie nt s in th e st ud y re ce iv ed a pa rti al do se an d pa ra m et er s w er e om itt ed fro m su m m ar y st at is tic s; an d d n =3 .T er m in al ph as e w as ch ar ac te riz ed fo rl es s th an on e ha lf- lif e fo r2 of 5 pa tie nt s. Th er ef or e, th es e pa tie nt s w er e ex cl ud ed fro m su m - m ar y st at is tic s fo rh al f-l ife as st ip ul at ed in th e da ta an al ys is pl an . 60 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Appendix 1: Schedule of Assessments - Dose-Escalation Safety Run-in (Part 1) and Dose Expansion (Part 2) 61 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 [0 42 2] Pr oc ed ur ea Pr e- Sc re en in g (P ar t2 O nl y) St ud y Tr ea tm en t: St ud y Tr ea tm en t: Fo llo w -u p Sc re en in g C yc le s 1 an d 2 C yc le 3, C yc le 4 an d Su bs eq ue nt C yc le s N ot A pp lic ab le D ay ‑1 4 to D ay 0 C yc le 1 D ay 1 C yc le 1 D ay 2 C yc le 1 D ay 3 C yc le 1 D ay 8 C yc le 2 D ay 1 C yc le 3b D ay 1 C yc le 4c D ay 1 O th er EO Td Su rv iv al e W ee k 0 W ee k 1 W ee k 1 W ee k 1 W ee k 2 W ee k 3 ≥W ee k 4 Pr e- sc re en in g in fo rm ed co n- se nt f X IH C an al ys is of FG FR 2b ex - pr es si on X Sa m pl e fo rb lo od -b as ed bi op sy (c tD N A) as sa y Xg Xh Xh Xh Xh Xh In fo rm ed C on se nt i X R ev ie w / C on fir m El ig ib ilit y C ri- te ria X X M ed ic al / O nc ol og y an d M ed ic a- tio n H is to ry X X Tu m or Ti ss ue C ol le ct io ni X D em og ra ph y / B as el in e C ha ra c- te ris tic s X Ph ys ic al Ex am in at io nk ,l X X X X X X X EC O G Pe rfo rm an ce St at us X Xm X Pa tie nt R ep or te d O ut co m es (E Q ‑5 D ‑5 L an d th e EO R TC Q LQ -C 30 )n X Xk Xk Vi ta lS ig ns o X X X X X X X X X 12 -le ad EC G p X Xq X 62 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 (c on tin ue d) Pr oc ed ur ea Pr e- Sc re en in g (P ar t2 O nl y) St ud y Tr ea tm en t: St ud y Tr ea tm en t: Fo llo w -u p Sc re en in g C yc le s 1 an d 2 C yc le 3, C yc le 4 an d Su bs eq ue nt C yc le s N ot A pp lic ab le D ay ‑1 4 to D ay 0 C yc le 1 D ay 1 C yc le 1 D ay 2 C yc le 1 D ay 3 C yc le 1 D ay 8 C yc le 2 D ay 1 C yc le 3b D ay 1 C yc le 4c D ay 1 O th er EO Td Su rv iv al e W ee k 0 W ee k 1 W ee k 1 W ee k 1 W ee k 2 W ee k 3 ≥W ee k 4 C om pr eh en si ve O ph th al m ol o- gi c Ex am r X Xo Xq X Sl it La m p Ex am in at io ns Xs Xs X C lin ic al Sa fe ty La bo ra to ry Sa m - pl in gt X X X X X X X X Pr eg na nc y Te st u X X X X U rin al ys is v X X X Xq X R ad io lo gi ca l / T um or Sc an sw X Xx Xx Xx Xy R an do m iz at io nz X Su rv iv al As se ss m en t X Fr es h Ti ss ue Bi op sy aa X Xa a Xa a Im m un og en ic ity Sa m pl in gb b X Xb b Xb b X C ol le ct io n fo rF C G R Po ly m or - ph is m cc X H ai rF ol lic le Sa m pl es dd X Xb b X PK Sa m pl es Xe e Xe e Xe e Xe e Xe e Xe e Xe e Xe e Bi om ar ke rA ss es sm en tS am - pl in g Xff Xff Xff Xff Xff O pe n- la be la nt i-F G FR 2- III b an tib od y Ad m in is tra tio n Xg g Xg g Xg g Xg g FO LF O X Ad m in is tra tio n Xh h Xi i Xi i Xi i X X X 63 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 (c on tin ue d) Pr oc ed ur ea Pr e- Sc re en in g (P ar t2 O nl y) St ud y Tr ea tm en t: St ud y Tr ea tm en t: Fo llo w -u p Sc re en in g C yc le s 1 an d 2 C yc le 3, C yc le 4 an d Su bs eq ue nt C yc le s N ot A pp lic ab le D ay ‑1 4 to D ay 0 C yc le 1 D ay 1 C yc le 1 D ay 2 C yc le 1 D ay 3 C yc le 1 D ay 8 C yc le 2 D ay 1 C yc le 3b D ay 1 C yc le 4c D ay 1 O th er EO Td Su rv iv al e W ee k 0 W ee k 1 W ee k 1 W ee k 1 W ee k 2 W ee k 3 ≥W ee k 4 Bl in de d an ti- FG FR 2- III b an ti- bo dy / P la ce bo Ad m in is tra tio n Xi i Xi i Xi i Xi i Ad ve rs e Ev en ts kk X X -X C on co m ita nt M ed ic at io ns X X 64 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 a Unless specified, procedure is to be completed within ± 72 hours of scheduled time point and to be synchro- nized with the study treatment administration day. b And subsequent odd cycles from Cycle 3, unless otherwise noted. c And subsequent even cycles from Cycle 4, unless otherwise noted. d End of Treatment (EOT) assessments should be performed 28 (±3) days following the last study treatment administration e Patients in both Part 1 and Part 2 will undergo long-term follow-up for survival by clinic visit or by telephone approximately every 3 months ± 28 days after the EOT visit until up to 24 months after the last patient is en- rolled into the study, or until death, loss to follow-up, withdrawal of consent or study termination by the Spon- sor (whichever occurs first). f Pre-screening ICF g Sample for blood-based biopsy (ctDNA) assay at Pre-screening for Part 2 only. Additional blood-based biopsy (ctDNA) samples are described in footnote h. h Samples for blood-based biopsy (ctDNA) assay: PART 1: Samples for blood-based biopsy (ctDNA) assay will be collected prior to the first dose of study drug (Cycle 1 Day 1) and analyzed retrospectively for FGFR2 amplification. PART 2: Blood samples for ctDNA assessment will be analyzed prospectively for FGFR2 am- plification. In addition, blood-based biopsy (ctDNA) assays will be collected longitudinally every 6 weeks from the first dose for 24 weeks, and then approximately every 12 weeks thereafter, and analyzed retrospectively for FGFR2 amplification. A sample will also be collected at the EOT visit for all Part 2 patients. i Written, signed informed consent must be collected prior to any study-specific procedures. The most recent IRB / EC approved ICF must be signed. j Tumor tissue from archival or newly obtained material (if available / feasible) is required in Part 1 and Part 2. Refer to the Laboratory Manual for sample handling instructions. k Complete physical examination and height will be measured at Screening only. Limited physical examina- tions should be conducted, including examination of the oropharynx, thereafter. l After Cycle 1, the IP dose will be recalculated at each infusion visit only if weight has changed >10% from Cycle 1, Day 1. m ECOG Performance Status will be assessed at Cycle 3 Day 1 and Day 1 of every other subsequent cycle (odd cycles) until the EOT visit. n The EQ‑5D‑5L and the EORTC QLQ-C30 will be administered prior to dosing on Cycle 1 Day 1, Cycle 4 Day 1, Cycle 7 Day 1, Cycle 10 Day 1, Cycle 13 Day 1, and then every 12 weeks. o Vital signs (blood pressure, pulse, respiration, and temperature) are to be measured on Cycle 1 Day 1 at the following time points: pre-dose, and 0.5, 1, 2, and 4 hours from the start of the anti-FGFR2-IIIb antibody infu- sion in Part 1 or the blinded IP infusion in Part 2. On subsequent dosing days, pre-dose and at 0.5, 1, and 2 hours from the start of anti-FGFR2-IIIb antibody infusion in Part 1 or the blinded IP infusion in Part 2. p With patient resting for 5 minutes prior to recording. q If clinically indicated at any time. r Comprehensive ophthalmologic examinations (conducted at Screening, prior to Cycle 3 Day 1, and at the EOT visit only) include fundoscopic and slit lamp exam, ocular coherence tomography (OCT), visual acuity, completion of fluorescein staining score form, determination of intraocular pressure, and review of ocular / vi- sual symptoms. The comprehensive ophthalmologic examination will be repeated at any point if changes in visual acuity or visual symptoms are reported by patients. s Slit lamp examinations without OCT for patients in Part 1 and for patients in Part 2 randomized to receive anti-FGFR2-IIIb antibody and FOLFOX 6; every 6 weeks after Cycle 2 Day 1 (prior to Cycle 3 Day 15, Cycle 5 Day 1, and Cycle 6 Day 15), and then every 12 weeks after Cycle 6 Day 15. Continue every 6‑8 weeks if the patient has any persistent corneal findings. t Blood tests (evaluated by local laboratories) are listed in Appendix 2. Hematology and blood chemistry test results must be obtained within 72 hours of study drug administration on C1D1 to confirm eligibility. On dos- ing days, hematology and blood chemistry results must be available within 72 hours prior to dosing. Coagu- lation samples need to be obtained at baseline, at Cycles 1 through 4, and at any time clinically indicated (e.g., patients on anticoagulant therapy requiring close monitoring). u Serum β-hCG (evaluated by local laboratories) will be performed only on women of childbearing potential □ 72 hours prior to Cycle 1 Day 1 and at EOT. On dosing days of odd cycles (every other cycle), urine preg- nancy results must be available within 72 hours prior to dosing. 65 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 (continued) v Includes dipstick for protein, glucose, blood, pH, and ketones. If dipstick findings are abnormal, then a micro- scopic evaluation will be performed to assess the abnormal findings. w Tumor assessments should consist of clinical examination and appropriate imaging techniques (preferably CT scans with appropriate slice thickness per RECIST); other assessments (MRI, radiograph, PET, and ul- trasound) may be performed if required. The same methods used to detect lesions at baseline are to be used to follow the same lesions throughout the clinical study. Screening tumor scan must be within 2 weeks of the start of treatment on Day 1. x Tumor scans to be performed at Screening (within 2 weeks of Cycle 1 Day 1 in Part 1 and Part 2) and within 7 days prior to the start of Cycle 4 Day 1, Cycle 7 Day 1, Cycle 10 Day 1, Cycle 13 Day 1, and then approxi- mately every 12 weeks. If initial CR or PR is noted, confirmatory scans must be performed 4‑6 weeks later. After discontinuation of study treatment for reasons other than progression or withdrawal of consent, tumor assessments will continue until the patient initiates additional anti-cancer therapy or progresses. y This scan can be omitted if the last scan was performed < 6 weeks prior to EOT visit or if tumor progression was previously determined. z For Part 2 only aa A fresh biopsy at a primary tumor or metastatic tumor site is mandatory, as feasible, at Screening [at least 24 hours prior to dosing] and on-treatment within 7 days prior to Cycle 3 Day 1 [and at least 24 hours prior to dosing] for only up to 30 patients randomized into Part 2. (For patients who have had a biopsy acquired with- in the 12 weeks prior to enrollment, this sample may fulfill the requirement for a fresh pre-treatment biopsy provided adequate sample is available for PD analysis (a single paraffin-embedded block or approximately 10 slides). After consultation with the Sponsor, patients who have documented response may receive an- other biopsy within 28 (±7) days post tumor assessment and / or patients who have progression may receive another biopsy at the EOT visit. The post-response and post-progression biopsies are optional. bb Blood samples for anti-anti-FGFR2-IIIb antibody antibodies. Refer to Appendix 3 for collection times. cc FCGR polymorphism testing sample. Refer to Appendix 3 for collection times. dd In Part 1 only, scalp or eyebrow hair follicle samples (approximately 10, if available) will be collected prior to dosing on Cycle 1 Day 1, Cycle 3 Day 1, and Cycle 5 Day 1, and at the EOT visit from all patients for whom sampling is possible. ee Blood samples for PK analysis. Refer to Appendix 3 for collection times. ff Blood samples for exploratory biomarker analysis (Parts 1 and 2). Refer to Appendix 3 for collection times. gg Open-label anti-FGFR2-IIIb antibody will be administered only to patients enrolled into Part 1. hh For Part 1, patients may have initiated mFOLFOX6 chemotherapy prior to study enrollment, and must be a candidate for at least 2 cycles of mFOLFOX6 chemotherapy to be eligible. For Part 2, patients are required to have completed 2 cycles of mFOLFOX6 chemotherapy prior to randomization. ii FOLFOX is administered as a 46-hour continuous infusion. jj Blinded IP (anti-FGFR2-IIIb antibody / placebo) will be administered only to patients randomized into Part 2. kk AE collection begins following signing of the ICF for Screening. Events reported prior to the first on-study in- fusion will be considered pretreatment events and reported on the Medical History page of the eCRF, unless they directly correlate to a study-related procedure. Adverse event reporting will continue until completion of the EOT visit or until 28 days after the last dose of study drug. Appendix 2: Laboratory Evaluations

[0423] The following laboratory parameters will be determined in accordance with the Schedule of Assessments: Hematology: Complete blood cell (CBC) with dif- ferential: white blood cells (WBC) platelets ANC hemoglobin neutrophils (%) hematocrit eosinophils (%) red blood cells (RBC) basophils (%) RBC indices: 66 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 (continued) Hematology: lymphocytes (%) mean corpuscular volume (MCV) monocytes (%) mean corpuscular hemoglobin (MCH) mean corpuscular hemoglobin concentration (MCHC) Urinalysis: Dipstick (appearance, color, pH, specific gravity, ketones, protein, glucose, bilirubin, nitrite, urobilinogen, and occult blood) If dipstick is positive (2+ or greater) for blood or protein, perform a microscopic examination. Clinical chemistry: Albumin globulin alkaline phosphatase glucose ALT (SGPT) lactate dehydrogenase (LDH) AST (SGOT) phosphate blood urea nitrogen (BUN) potassium calcium sodium chloride total bilirubin carbon dioxide (CO2 [bicarbonate]) total cholesterol creatinine total protein direct bilirubin uric acid Appendix 3: Study Flowchart for Pharmacokinetic, Immunogenicity, and Pharmacodynamic Blood Sample Collections for Part 2

[0424] Study Cycle Study Day Time Point Type of Sample Cycle 1 Day 1 (First Dose) ≤ 4 hours Prior to infusion anti-FGFR2-IIIb antibody PK (serum) ADA (serum) Hair Follicle (if available) Blood-based Biomarker (optional; whole blood) FCGR Polymorphism (optional; whole blood) Blood-based biopsy (ctDNA) 5 minutes after end of in- fusion anti-FGFR2-IIIb antibody PK (serum) 1 hour after end of infusion (± 5 minutes) anti-FGFR2-IIIb antibody PK (serum) 4 hours after end of infu- sion (±5 minutes) anti-FGFR2-IIIb antibody PK (serum) Day 8 168 hours after infusion (±2 days) anti-FGFR2-IIIb antibody PK (serum) Day 15 (Second Dose) ≤ 4 hours Prior to infusion anti-FGFR2-IIIb antibody PK (serum) 5 minutes after end of in- fusion anti-FGFR2-IIIb antibody PK (serum) 67 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 (continued) Study Cycle Study Day Time Point Type of Sample Cycle 2 through Cy- cle 5 Day 1 (First Dose) ≤ 4 hours Prior to infusion anti-FGFR2-IIIb antibody PK (serum) ADA (serum) Hair Follicle at Cycle 2 and 3 only (if avail- able) Blood-based Biomarker at Cycle 4 only (op- tional; whole blood) 5 minutes after end of in- fusion anti-FGFR2-IIIb antibody PK (serum) Day 15 (Second Dose) ≤ 4 hours Prior to infusion Blood-based Biomarker at Cycle 2 and 5 only (optional; whole blood) Cycle 7 and Subsequent Cycles Day 1 (First Dose) ≤ 4 hours Prior to infusion anti-FGFR2-IIIb antibody PK at odd cycles only (serum) ADA at odd cycles only (serum) Blood-based Biomarker at Cycle 7 and then every 12 weeks thereafter (optional; whole blood) 5 minutes after end of in- fusion anti-FGFR2-IIIb antibody PK at odd cycles only (serum) End of Treatment Follow-up Visit Date During Visit anti-FGFR2-IIIb antibody PK (serum) ADA (serum) Hair Follicle (if available) Blood-based Biomarker (optional; whole blood) Appendix 4: ECOG Performance Status

[0425] Grade Performance Status Criteria 0 Fully active, able to carry on all pre-disease activities without restriction. 1 Restricted in physically strenuous activity but ambulatory and able to carry out work of a light sedentary nature (light housework, office work). 2 Ambulatory and capable of all self-care but unable to carry out any work activities. Up and about more than 50% of waking hours. 3 Capable of only limited self-care, confined to bed or chair more than 50% of waking hours. 4 Completely disabled. Cannot carry on any self-care. Totally confined to bed or chair. Example 2: A Phase 1 / 3 Study of an Anti-FGFR2-IIIb Antibody Combined with Modified FOLFOX6 versus Mod- ified FOLFOX6 in Patients with Previously Untreated Advanced Gastric and Gastroesophageal Cancer Protocol Synopsis

[0426] This study is a variation of the study described in Example 1 herein, and is a multicenter study to evaluate the safety, tolerability, efficacy, PK, and PD of an anti-FGFR2-IIIb antibody in combination with mFOLFOX6. The study will include an open-label, Phase 1 safety run-in in patients with GI tumors (not FGFR2 selected) followed by a randomized, open-label Phase 3, in patients with FGFR2-selected GC (as determined by prospective IHC analysis of FGFR2b overexpression and / or a ctDNA blood assay demonstrating FGFR2 gene amplification). After an initial screening period, 68 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 patients will be treated with mFOLFOX6 in combination with anti-FGFR2-IIIb antibody or mFOLFOX6 alone in 2 week cycles. Phase 1: Dose-Escalation Safety Run-in

[0427] Phase 1 is an open-label dose-escalation of anti-FGFR2-IIIb antibody in combination with mFOLFOX6. Eligible patientswill haveunresectable locally advancedormetastaticGI cancer of any typeandbecandidates to receiveat least 2 doses of mFOLFOX6 chemotherapy. FGFR2 status is not a requirement for enrollment. FGFR2 status will be tested retrospectively by IHC (if tissue is available) and a sample will be obtained for ctDNA blood assay.

[0428] Phase 1 consists of aminimum of 2 dosing cohorts of anti-FGFR2-IIIb antibody in combination withmFOLFOX6 to determine theRD of anti-FGFR2-IIIb antibody to be administered in combination withmFOLFOX6 in Phase 3. Patients may or may not have initiated or received prior mFOLFOX6 chemotherapy. There is no upper limit on the number of previous mFOLFOX6 doses that patients may have received.

[0429] Eachpatient enrolledwill be observed for 28 days (DLTPeriod) starting on the first day (Cycle 1Day1 [StudyDay 1]) of treatment with anti-FGFR2-IIIb antibody, for safety assessments, PK and occurrence of dose-limiting toxicities. Cohortsof patientswill be treatedwithescalatingdosesof anti-FGFR2-IIIbantibody in combinationwithastandarddoseof a chemotherapy regimen of mFOLFOX6 in 2 week cycles. Anti-FGFR2-IIIb Antibody Administration

[0430] Anti-FGFR2-IIIb antibody IV is administeredevery2weeksonDay1of eachcycle (2weeks=1cycle) andprior to mFOLFOX6 chemotherapy. Patients treated in Cohort 2 only will receive one additional dose of anti-FGFR2-IIIb antibody Day 8 of Cycle 1 (mFOLFOX6 will not be administered on this day). Anti-FGFR2-IIIb antibody will be administered as an approximately 30 minute IV infusion via a peripheral vein or central venous catheter. The IV administration set for anti- FGFR2-IIIb antibody infusion must contain a 0.22-µm in-line filter or a 0.22-µm syringe filter. mFOLFOX6 Administration

[0431] Administration of mFOLFOX6 chemotherapy will also commence on Cycle 1 Day 1 (Study Day 1) of each treatment cycle 30 minutes after the end of the infusion of anti-FGFR2-IIIb antibody. mFOLFOX6 will be administered every 2 weeks as follows: - Day 1: Oxaliplatin 85 mg / m2 IV infusion over 120 minutes, - Day 1: Leucovorin 400mg / m2 IV infusion over 120minutes, can be administered concurrently with oxaliplatin if using a Y connector, if not using a Y connector administer sequentially, - Day 1: Immediately after oxaliplatin and leucovorin, 5 FU 400 mg / m2 bolus over approximately 5 minutes, - Day 1: Immediately after the 5-FU bolus, 5-FU 2400 mg / m2 as a continuous IV infusion over 46 hours.

[0432] After the 28 day DLT period, patients may have doses held or receive reduced doses of mFOLFOX6 or anti- FGFR2-IIIb antibody based on toxicity analysis. Premedication may be used at the discretion of the investigator per local standard of care. Phase 1 Cohorts

[0433] InPhase1, thefirst dosecohort of anti-FGFR2-IIIbantibody tobe tested isat 6mg / kg.Theanticipateddose levels are: - Cohort 1: 6 mg / kg anti-FGFR2-IIIb antibody every 2 weeks; - Cohort 2: 15 mg / kg anti-FGFR2-IIIb antibody every 2 weeks; 1 dose of 7.5 mg / kg on Day 8 (Cycle 1 only); - Cohort 3 (if needed): 15 mg / kg anti-FGFR2-IIIb antibody every 2 weeks; - Cohort 4 (if needed): Dose level lower thanCohort 3 but higher thanCohort 1 to achieve tolerability with optimal target exposure.

[0434] If the first cohort at 6mg / kg clears the 28-dayDLTperiod, the seconddose cohort at 15mg / kg every 2weekswith a dose of 7.5 mg / kg on Day 8 (Cycle 1 only) will be tested in a rolling‑6 design and enroll 6 patients. Dose escalation decisions will be based on an assessment of DLTs, overall safety and tolerability. Dose escalation decisions will be made after the last patient enrolled in eachcohort has completed the28-dayDLTPeriod (completionof 2 treatment cyclesof anti- FGFR2-IIIb antibody and mFOLFOX6). Dose escalation decisions will be agreed upon by the Cohort Review Committee 69 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 (CRC), consisting of the Sponsor and investigators. If ≥ 2 DLTs are observed in Cohort 2, a dose level between Cohorts 1 and 2 may be evaluated (Cohort 3) in a rolling 6 (15 mg / kg every 2 weeks) design. If ≥ 2 DLTs are observed in Cohort 3 a dose level lower thanCohort 3 but higher thanCohort 1may be evaluated (Cohort 4) in a rolling 6 design. DLTs are defined as any of the following deemed by investigator as related to anti-FGFR2-IIIb antibody. • ANC<0.5 x109 / L>5days’ durationor febrile neutropenia (ie,ANC<1.0 x109 / Lwitha single temperatureof >38.3°C, or fever ≥ 38 °C for more than 1 hour). Use of G-CSF is permitted per institutional standards • Platelets < 25 x 109 / L or platelets < 50 x 109 / L with bleeding requiring medical intervention • Prolonged (> 3 days) < 50 x 109 / L platelets • Grade 4 anemia (ie, life-threatening consequences; urgent intervention indicated) • Any Grade 2‑3 ophthalmologic AE that does not resolve within 7 days • Grade 4 ophthalmologic AE • AST / ALT ≥ 3x ULN and concurrent total bilirubin ≥ 2x ULN not related to liver involvement with cancer • Any non-hematological AE Grade 3 or greater (except nausea, vomiting, and diarrhea). • Grade 3 nausea, vomiting or diarrhea that does not resolve with supportive care in 72 hours • Grade 3 laboratory values that are not of clinical significance per investigator and

[0435] Sponsor agreement if they do not resolve within 72 hours. • Grade 4 nausea, vomiting or diarrhea • Any Grade 4 laboratory value

[0436] The following algorithm in Table 7 below will be used for dose dose escalation decisions: Table 7: Algorithm for Dose Escalation Number of Patients with DLTs Action 0 / 3 Open next cohort 1 / 3 Enroll 3 more patients in same cohort ≥ 2 / 3 Stop enrollment. If Cohort 1, then the study will be stopped. 1 / 6 Open next cohort ≥ 2 / 6 Stop enrolment at that level. If at Cohort 1, the study will end. If at Cohort 2 or 3, then Cohort 3 or 4 will open respectively and 6 patients will be enrolled.

[0437] TheRDofanti-FGFR2-IIIbantibody forPhase3will be identifiedby theCRCbasedonanevaluationof theoverall safety, tolerability, andPKandwill not exceed15mg / kgadministered IVevery2weekswith 1doseof 7.5mg / kgonDay8of Cycle 1 only. In determining the RD, the CRC will consider toxicities observed during the DLT evaluation period, any toxicities observed beyond the DLTevaluation period, as well as dose reductions and discontinuations of mFOLFOX6 or anti-FGFR2-IIIb antibody due to toxicities that donotmeet theDLTcriteria. Basedon the totality of the data, the chosenRD ofanti-FGFR2-IIIbantibodywill beadose that is not anticipated to lead toadecrease in thedose intensity ofmFOLFOX6 to be administered. The RD, therefore, may or may not be the same as the identified maximum tolerated dose (MTD). For example, if theMTD is not reached, or if data from subsequent cycles of treatment fromPhase 1 provide additional insight on the safety profile, then the RD may be a different, though not higher, dose than the MTD.

[0438] The MTD is defined as the maximum dose at which < 33% of patients experience a DLT (dose limiting toxicity) during the DLT Period. If a DLT is observed in 1 of 3 patients in Cohort 1, then 3 additional patients will be enrolled at that dose level.Doseescalationmaycontinueuntil 2 of 3 to6patients treatedatadose level experienceaDLT (dose level not to exceed the highest dose level tolerated in Phase 1). The next lower dose will then be considered the MTD. Study Design

[0439] Upon initiation of enrollment into Cohort 2 (15 mg / kg cohort every 2 weeks with 1 dose of 7.5 mg / kg on Day 8 [Cycle 1 only]), 6 patients will be enrolled to explore the safety and efficacy. The total enrollment for Phase 1 will be approximately 9 to 21 patients.

[0440] Anypatient whodoes not receive the full number of doses of anti-FGFR2-IIIb antibody as definedby cohort and 2 full doses of mFOLFOX6 during the DLT Period due to a reason that is not a DLT or an AE related to anti-FGFR2-IIIb antibody, will be considered unevaluable and the patient will be replaced. The replaced patient may continue on study at 70 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 the investigator’s discretion and after discussion with the Sponsor. No additional doses of anti-FGFR2-IIIb antibody or more than 2 doses of mFOLFOX6 should be administered during the 28-day DLT Period. The doses of anti-FGFR2-IIIb antibody andmFOLFOX6onDay 1 ofCycle 2 do not need to be synchronized. For example, if mFOLFOX6 is delayed due to anAE that is deemed related only tomFOLFOX6 and not to anti-FGFR2-IIIb antibody, anti-FGFR2-IIIb antibody should be administered as scheduled for Cycles 1 and 2 regardless of delays in the mFOLFOX6 dosing schedule.

[0441] Upon completion of the DLT Period, patients may continue receiving anti-FGFR2-IIIb antibody in combination with mFOLFOX6 at the investigator’s discretion. Additional treatments may be administered every 2 weeks (1 cycle) until investigator-assessed radiographic or clinical disease progression, unacceptable toxicity, or until the patientmeets any of the other protocol-specified withdrawal criteria.

[0442] In the event a cycle of mFOLFOX6 is delayed beyond 2 weeks due to chemotherapy-related toxicity during the first 3cyclesof treatment (42days), anti-FGFR2-IIIbantibodyshouldbeadministeredonschedule (±3days).After thefirst 3 cycles, anti-FGFR2-IIIb antibody may be delayed up to ± 7 days to be synchronized with administered mFOLFOX6. There is nomandatedmaximum number of doses of anti-FGFR2-IIIb antibody or mFOLFOX6. Ongoing administration of the mFOLFOX6 regimen beyond the DLT Period will be according to the following schedule: • Starting dose for mFOLFOX6 includes 85 mg / m2 of oxaliplatin, 400 mg / m2 of calcium folinate (folinic acid), a 400 mg / m2 bolus dose of 5-FU, and a 2400 mg / m2 continuous infusion dose of 5-FU over 46 hours • mFOLFOX6 regimenwill be administered every 2weeks (±3days) until investigator -assessed radiographic disease progression (Phase 3 only), clinical disease progression (Phase 1 only), unacceptable toxicity, or the patient meets any of the other protocol-specified withdrawal criteria • Day 1: Oxaliplatin 85 mg / m2 IV infusion over 120 minutes • Day1:Leucovorin400mg / m2 IV infusionover120minutes, canbeadministeredconcurrentlywithoxaliplatin if usinga Y connector; if not using a Y connector administer sequentially • Day 1: Immediately after oxaliplatin and leucovorin, 5 FU 400 mg / m2 bolus over approximately 5 minutes • Day 1: Immediately after the 5-FU bolus, 5-FU 2400 mg / m2 as a continuous IV infusion over 46 hours.

[0443] Any modifications to the ongoing administration of mFOLFOX6 may occur under the following guidelines: • If there is a change in body weight of at least 10%, doses should be recalculated. • Counsel patients to avoid exposure to cold weather during and for approximately 72 hours after each infusion. • Correct hypokalemia and hypomagnesemia prior to initiating oxaliplatin. • Severe diarrhea, mucositis, and myelosuppression after 5-FU should prompt evaluation for dihydropyrimidine dehydrogenase deficiency. • Leucovorin dose is given for d,l-racemic mixture. Use half the dose for LEVO-leucovorin (l-leucovorin) • In the event that oxaliplatin administration is discontinued for any reason prior to disease progression, 5-FU / leu- covorin therapymay continue on an every‑2week schedule until disease progression, unacceptable toxicity, or other cause for studywithdrawal. In thecase5-FU / leucovorin therapy isdiscontinued thenoxaliplatinmustbediscontinued.

[0444] Certain dose adjustments for mFOLFOX6 toxicity are shown in Table 8 below. 71 EP 4 650 004 A2 5 10 15 20 25 30 35 40 45 50 55 Table 8: Dose Reductions and Delays for mFOLFOX6 Chemotherapy Toxicity Grade Oxaliplatin 5-FU / Leucovorin Neurotoxicity Persistent (≥ 1 cycle) Grade 2 Neurotoxicity Decrease from 85 mg / m2 to 65 mg / m2* No change Transient (> 7 days and ≤14 days) Grade 3 Neurotoxicity Decrease from 85 mg / m2 to 65 mg / m2* No change Persistent (> 1 cycle) ≥ Grade 3 Neurotoxicity or any Grade 4 Neurotoxicity Discontinue No change Gastrointestinal ≥ Grade 3 (after prophylaxis) Hold until toxicity is ≤ Grade 1, decrease from 85 mg / m2 to 65 Hold until toxicity is ≤ Grade 1, decrease by 20%* mg / m2 * Hematologic ≥ Grade 3 platelets Hold until platelets are ≥ 75,000 then decrease from 85 mg / m2 to 65 mg / m2* Reduce by 20%* ≥ Grade 3 neutropenia Hold until ANC is ≥ 1500, then decrease from 85 mg / m2 to 65 mg / m2* Reduce by 20%* Skin ≥ Grade 3 Hand / foot syndrome Hold until 5-FU resumes, then no change Hold until ≤ Grade 1, then decrease by 20%* Other ≥ Grade 3 Hold until ≤ Grade 1, then de- crease from 85 mg / m2 to 65 mg / m2* Hold until ≤ Grade 1, then reduce by 20%* Pharyngolaryngeal dysesthesia Any Stop infusion, then consider in- crease duration of infusion up to 6 hours No change Pneumonitis Any Hold, investigate; discontinue permanently if confirm...

Claims

1. An afucosylated anti-fibroblast growth factor receptor 2 IIIb (anti-FGFR2-IIIb) antibody for use in a method of treating gastric cancer in a subject, the method comprising administering to the subject (i) the anti-FGFR2-IIIb antibody, and (ii) modified FOLFOX6 (mFOLFOX6) chemotherapy, wherein the antibody comprises a heavy chain amino acid sequence of SEQ ID NO: 2 and a light chain amino acid sequence of SEQ ID NO: 3, and wherein the anti-FGFR2-IIIb antibody is administered at a dose of 15 mg / kg once every 14 days, and wherein 7 days following the first administration of the anti-FGFR2-IIIb antibody, the anti-FGFR2-IIIb antibody is administered at a dose of 7.5 mg / kg.

2. The anti-FGFR2-IIIb antibody for the use of claim 1, wherein the anti-FGFR2-IIIb antibody lacks a fucose at position Asn297.

3. The anti-FGFR2-IIIb antibody for the use of claim 1 or claim 2, wherein the gastric cancer is locally advanced, unresectable or metastatic.

4. The anti-FGFR2-IIIb antibody for the use of any one of claims 1-3, wherein the anti-FGFR2-IIIb antibody is administered concurrently or sequentially with the modified FOLFOX6 chemotherapy.

5. The anti-FGFR2-IIIb antibody for the use of any one of claims 1-4, wherein the mFOLFOX6 comprises administration of 50-100 mg / m2 oxaliplatin, 100-400 mg / m2 leucovorin, and 100-400 mg / m2 5-fluorouracil (5-FU) by intravenous (IV) infusion or IV bolus followed by administration of 2000-2500 mg / m2 5-FU by IV infusion or IV bolus over 44-48 hours.

6. The anti-FGFR2-IIIb antibody for the use of claim 5, wherein the mFOLFOX6 comprises administration of 85 mg / m2 oxaliplatin, 400 mg / m2 leucovorin, and 400 mg / m2 5-FU by IV infusion or IV bolus over 44-48 hours.

7. The anti-FGFR2-IIIb antibody for the use of claim 6, wherein the mFOLFOX6 comprises administration of 85 mg / m2 oxaliplatin, 400 mg / m2 leucovorin, and 400 mg / m2 5-FU by IV infusion or IV bolus followed by administration of 2400 mg / m2 5-FU by IV infusion over 44-48 hours.

8. The anti-FGFR2-IIIb antibody for the use of any one of claims 1-7, wherein the mFOLFOX6 is administered once every 10-21 days.

9. The anti-FGFR2-IIIb antibody for the use of claim 8, wherein the mFOLFOX6 is administered once every 14 days.

10. The anti-FGFR2-IIIb antibody for the use of any one of claims 1-9, wherein mFOLFOX6 is administered prior to administering the anti-FGFR2-IIIb antibody.

11. The anti-FGFR2-IIIb antibody for the use of claim 10, wherein two administrations of the mFOLFOX6 are given prior to administering the anti-FGFR2-IIIb antibody.

12. The anti-FGFR2-IIIb antibody for the use of any one of claims 1-9, wherein the anti-FGFR2-IIIb antibody is administered on the same day as the mFOLFOX6 and prior to mFOLFOX6 administration.

13. The anti-FGFR2-IIIb antibody for the use of any one of claims 1-12, wherein the gastric cancer has previously been determined to overexpress FGFR2-IIIb and / or the gastric cancer has previously been determined to have an FGFR2 gene amplification.

14. The anti-FGFR2-IIIb antibody for the use of claim 13, wherein FGFR2-IIIb overexpression is determined by immunohistochemistry (IHC).

15. The anti-FGFR2-IIIb antibody for the use of claim 14, wherein the FGFR2-IIIb overexpression is characterized by an IHC signal of +2 or 3+ in at least 10% of tumor cells.

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