Treatment of hemophilia with fitusiran

Abstract

The present disclosure provides methods aimed at maintaining a favorable benefit-risk balance for patients with hemophilia A or B, with or without inhibitors, treated with fitusiran.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority from U.S. Patent Application Nos. 63 / 121,973, filed December 6, 2020, 63 / 272,629, filed October 27, 2021, and 63 / 275,344, filed November 3, 2021. The contents of the priority applications are incorporated herein by reference in their entirety.

[0002] Sequence Listing Reference This application contains a Sequence Listing that has been submitted electronically in ASCII format and is incorporated herein by reference in its entirety. The ASCII copy, generated on December 2, 2021, is named 022548_WO086_SL.txt and is 4,656 bytes in size. [Background technology]

[0003] Maintenance of normal hemostasis relies on a controlled series of simultaneous procoagulant and anticoagulant processes, in which thrombin plays a central role. Hemophilia A and B are inherited bleeding disorders caused by deficiencies of factor VIII and factor IX, respectively. Bleeding in hemophilia A and B occurs due to insufficient thrombin generation (Non-Patent Document 1). Without effective treatment, patients with hemophilia experience recurrent bleeding episodes, which can lead to severe disability and significant pain due to chronic hemoarthropathy and can become life-threatening (Non-Patent Document 2).

[0004] Despite advances in treatment, significant unmet need and management challenges remain for all hemophilia populations. While prophylaxis based on replacement therapy with factor VIII or factor IX is considered essential for hemophilia management, it has significant limitations. For example, prophylactic factor replacement injections are burdensome and impractical, often requiring multiple weekly intravenous infusions (Non-Patent Document 1; Non-Patent Document 3; Non-Patent Document 4; Non-Patent Document 5; Non-Patent Document 6). Factor replacement is also limited by the difficulty of venous access and the risk of infection (Non-Patent Document 7; Non-Patent Document 8). Limitations in the delivery of factor replacement also result in a high proportion of the hemophilia population worldwide without access to prophylactic treatment in the first place (Non-Patent Document 9).

[0005] In addition, treatment with factor replacement products can result in the development of inhibitory alloantibodies, rendering factor treatment ineffective (Non-Patent Document 10). These inhibitors typically develop in early childhood, limiting treatment options and dramatically worsening the prognosis of hemophilia. Furthermore, individuals with persistent inhibitors typically experience lower quality of life, more joint disease, greater surgical risk, and higher mortality rates, including a higher risk of death from hemophilia-related bleeding complications, compared with patients without inhibitors (Non-Patent Document 10; Non-Patent Document 11). Current treatment tactics for individuals with persistent inhibitors include immune tolerance induction (ITI) and prophylaxis with bypassing agents (BPAs), such as activated prothrombin complex concentrates (aPCC) and recombinant activated factor VII (rFVIIa) (Non-Patent Document 12; Non-Patent Document 13; Non-Patent Document 14; Non-Patent Document 15; Non-Patent Document 16). [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Peyvandi et al., Lancet (2016) 388(10040):187-97 [Non-patent document 2] Pipeら, Haemophilia (2007) Volume 13, Supplement 4:1~16 [Non-licensed Document 3] Ljung Andersson, Br J Haematol. (2015) Volume 169 (No. 6): Pages 777~86 [Non-licensed Document 4] Srivastava, Haemophilia (2013) Volume 19 (No. 1): Pages e1~47 [Non-licensed Document 5] Bauer, Am J Manag Care (2015), Volume 21 (Supplement 6): Pages 112-22 [Non-licensed Document 6] MannucciおよびFranchini, Blood Transfus. (2013) Volume 11 (Supplement 4): s77~81 [Non-licensed Document 7] Balkaransingh and Young, Ther Adv Hematol. (2018) Vol. 9 (No. 2): 49-61 [Non-licensed Document 8] Valentino, Blood Rev. (2011), Volume 25 (Issue 1): Pages 11-5 [Non-licensed Document 9] Hemophilia, WFO Treatment Safety and Supply. 2020 [Non-licensed Document 10] Morfini, Haemophilia (2007) Volume 13 (No. 5): Pages 606~12 [Non-licensed Document 11] Oladapo, Orphanet J Rare Dis. (2018) Volume 13 (No. 1): 198 pages [Non-licensed Document 12] Benson, Eur J Haematol. (2012) Vol. 88 (No. 5): 371-79 [Non-licensed Document 13] Collins, Br J Haematol. (2013) Volume 160 (No. 2): 153-70 [Non-licensed Document 14] Kempton et al., Blood (2014) 124(23):3365-72 [Non-Patent Document 15] Astermark et al., Haemophilia (2007) 13(1):38-45 [Non-Patent Document 16] Eichinger et al., Eur J Clin Invest. (2009) 39(8):707-13 Summary of the Invention [Problem to be solved by the invention]

[0007] Thus, there remains a need for alternative treatments for subjects with bleeding disorders, such as hemophilia. [Means for solving the problem]

[0008] The present disclosure provides methods of prophylactically treating hemophilia A and hemophilia B with fitusiran to prevent or reduce the frequency of bleeding episodes in patients, optionally in patients aged 12 years or older, and provides fitusiran for use in these methods. In one aspect, the present disclosure provides methods of prophylactic treatment of patients with hemophilia A or B, with or without inhibitors, or methods of reducing the risk of thrombosis in patients receiving fitusiran for prophylactic treatment of hemophilia A or B, with or without inhibitors, and provides fitusiran for use in such methods.

[0009] In some embodiments, the method comprises: a) administering 50 mg of fitusiran subcutaneously every two months or every eight weeks to a patient in need thereof; b) obtaining a measurement of antithrombin (AT) levels in the patient; and c) if the AT level is >X% (where X=25 or 35), administering 80 mg of fitusiran subcutaneously every two months or every eight weeks, or 50 mg of fitusiran subcutaneously every month or every four weeks to the patient.

[0010] In some embodiments, the method further includes: d) continuing step a) when the AT level is between Y and X% (where Y = 10 or 15), and / or e) stopping the fexeran treatment when the AT level is < Y% (where Y = 10 or 15). In further embodiments, step b) is performed at least twice, step c) is performed only when both measured AT levels are > X%, or step e) is performed only when both measured AT levels are < Y%. In some embodiments, X is 35 and Y is 15.

[0011] In some embodiments, after performing step c), the method further includes: i) obtaining a measurement of the AT level in the patient; and ii) subcutaneously administering 80 mg of fexeran to the patient monthly or every four weeks when the AT level in step i) is > 25% or > 35%, or iii) otherwise continuing step c). In further embodiments, step i) is performed at least twice, and step ii) is performed only when both measured AT levels in step i) are > 25% or > 35%.

[0012] In some embodiments, the method further comprises, after performing step c), which comprises subcutaneously administering 80 mg of fitusiran to the patient every two months or every eight weeks: i) obtaining a measured AT level in the patient; and ii) if the AT level in step i) is >25% or >35%, subcutaneously administering 50 mg of fitusiran to the patient monthly or every four weeks, or iii) otherwise continuing with step c). In further embodiments, step i) is performed at least twice, and step ii) is performed only if both measured AT levels in step ii) are >25% or >35%. In certain embodiments, the method further comprises, after performing step ii), A) obtaining a measured AT level in the patient; and B) if the AT level in step A) is >25% or >35%, subcutaneously administering 80 mg of fitusiran to the patient monthly or every four weeks, or C) otherwise continuing with step ii). In a further embodiment, step A) is performed at least twice and step B) is performed only if the measured AT levels are both >25% or >35%.

[0013] In some embodiments of the present disclosure, X is 35% and Y is 15%. In other embodiments, X is 35% and Y is 10%. In other embodiments, X is 25% and Y is 15%. In other embodiments, X is 25% and Y is 10%.

[0014] In one aspect, the disclosure provides methods for the prophylactic treatment of patients with hemophilia A or B, with or without inhibitors, or for reducing the risk of thrombosis in patients receiving fitusiran for the prophylactic treatment of hemophilia A or B, with or without inhibitors, optionally wherein the patient is 12 years of age or older, and fitusiran for use in such methods, the methods comprising: a) administering to a patient in need thereof fitusiran at a starting dose (e.g., selected from 10 mg to 50 mg) at a selected dosing frequency (e.g., every two months (Q2M) or every eight weeks (Q8W)). (b) obtaining a measurement of antithrombin (AT) levels in the patient; and (c) performing one of the following steps: (i) repeating step (a) if the AT level is between 15 and 35%, (ii) administering to the patient subcutaneously fitusiran at a higher dose and at a selected dosing frequency, or at a higher dosing frequency (e.g., monthly (QM) or every four weeks (Q4W)) at the starting dose, if the AT level is >35%, or (iii) discontinuing or pausing fitusiran treatment if the AT level is <15%.

[0015] In some embodiments, the starting dose is 20 mg and the selected dosing frequency is Q2M or Q8W.

[0016] In some embodiments, the starting dose is 50 mg, the selected dosing frequency is Q2M or Q8W, and optionally, step (c)(ii) is performed if two measurements of AT level are >35%, or step (c)(iii) is performed if two or more, optionally two, measurements of AT level are <15%. In further embodiments, step (c)(ii) comprises subcutaneously administering 50 mg QM of fitusiran to the patient. In certain embodiments, the method comprises subcutaneously administering 80 mg QM of fitusiran to the patient after step (c)(ii) if the AT level in the patient after step (c)(ii), optionally by two measurements, is >35%.

[0017] In some embodiments, the method further comprises, after step (c)(iii): (A) administering fitusiran subcutaneously to the patient at 20 mg Q2M; (B)(1) discontinuing fitusiran treatment if the patient's AT level after step (A) is <15%, optionally by more than one measurement; (2) repeating step (A) if the AT level after step (A) is 15-35%; or (3) administering fitusiran subcutaneously to the patient at 20 mg QM if the AT level after step (A) is >35%, optionally by two measurements.

[0018] In some embodiments, the method includes subcutaneously administering fitusiran to a patient at a dosage and dosing frequency sufficient to maintain the patient's AT levels between 15-35%, optionally with a dosing regimen selected from 10 mg QM or Q4W, 20 mg QM or Q4W, 20 mg Q2M or Q8W, 50 mg QM or Q4W, 50 mg Q2M or Q8W, or 80 mg QM or Q4W.

[0019] In some embodiments, the AT level measurements are obtained during a steady state of AT activity, for example, after the patient has received at least two doses of fitusiran in the previous step. In some embodiments, each AT level measurement is obtained after the patient has received at least two doses of fitusiran at a predetermined dosage. In some embodiments, the method includes obtaining measurements of the AT level in the patient every 4 weeks, every 8 weeks, every month, every 2 months, every 4 months, every 6 months, or every 12 months.

[0020] In one aspect, the disclosure provides methods for the prophylactic treatment of patients with hemophilia A or B, with or without inhibitors, and fitusiran for use in such methods, optionally wherein the patient is 12 years of age or older, the method comprising subcutaneously administering fitusiran 50 or 80 mg Q2M or Q8W (e.g., 50 mg Q2M or Q8W, or 80 mg Q2M or Q8W) to a patient in need thereof.

[0021] In another embodiment, the present disclosure provides methods for the prophylactic treatment of patients with hemophilia A or B, with or without inhibitors, and fitusiran for use in such methods, optionally wherein the patient is 12 years of age or older, the method comprising administering fitusiran 20 mg subcutaneously QM or Q4W, or Q2M or Q8W to a patient in need thereof.

[0022] In another embodiment, the present disclosure provides a method for the prophylactic treatment of a patient with hemophilia A or B, with or without inhibitors, and fitusiran for use in such a method, optionally wherein the patient is 12 years of age or older, the method comprising administering 10 mg of fitusiran subcutaneously QM or Q4W to a patient in need thereof.

[0023] In some embodiments, fitusiran is a sodium salt and can be provided in a pharmaceutically acceptable aqueous solution, for example, 50-200 mg / mL, optionally 100 mg / mL, in phosphate buffered saline (PBS), optionally having a pH of 7. As used herein, fitusiran weight refers to the weight of fitusiran in its free acid form.

[0024] In one aspect, the disclosure provides an article of manufacture (e.g., a kit, optionally including instructions for use) for use in the treatment method. In some embodiments, the article of manufacture is a container containing one or more doses of fitusiran, each dose being 80 mg, 50 mg, 20 mg, or 10 mg, optionally 80 mg of fitusiran in 0.8 mL of phosphate-buffered saline (PBS), 50 mg of fitusiran in 0.5 mL of PBS, 20 mg of fitusiran in 0.2 mL of PBS, or 10 mg of fitusiran in 0.1 mL of PBS, optionally with a pH of 7. The container may be, for example, a disposable, single-dose pre-filled syringe.

[0025] In another aspect, the present disclosure provides fitusiran for the manufacture of a medicament for treating hemophilia A or B with or without inhibitors in the methods of treatment herein.

[0026] Other features, objects, and advantages of the present invention will become apparent in the following detailed description. It should be understood, however, that the detailed description, while indicating embodiments and aspects of the present invention, is given by way of illustration only and not limitation. Various changes and modifications within the scope of the present invention will become apparent to those skilled in the art from this detailed description. [Brief explanation of the drawings]

[0027] [Figure 1-1] 1 shows an expanded structural formula, chemical formula and molecular mass of phytusirane, which discloses SEQ ID NOs: 1 and 2, respectively, in order of appearance. [Figure 1-2] Continued from Figure 1-1. [Figure 2] Graph showing AT activity of five patients with thrombotic events overlaid on AT activity of patients in Phase 3. The black circles in the background are AT activity data from the Phase 3 trial only. Each line represents an individual patient. [Figure 3] Graph showing the distribution of coefficients of variation (%CV) for intra-individual variability in steady-state AT activity. [Figure 4] Graph showing mean AT thresholds at which there is a 95% probability that the next AT value will be >10%. [Figure 5] 1 is a jitterbox plot of thrombin generation peak height in a Phase I study. [Figure 6] 1 is a bar graph depicting ABR estimates by quartiles of AT in a phase I study. [Figure 7] 1 is a flow chart showing the Fitusiran titration scheme. "Q2M": Every 2 months. "QM": Every month. [Figure 8] 1 is a flow chart depicting an alternative Fitusiran titration scheme. [Figure 9]1 is a flow chart depicting an alternative Fitusiran titration scheme. [Figure 10] Schematic diagram showing the pharmacokinetic / pharmacodynamic (PK / PD) model used to simulate the kinetics of plasma AT activity for patients treated with fitusiran. KA: absorption rate; F: bioavailability with dose effect on bioavailability; V2: hepatic central compartment volume; V3 hepatic peripheral compartment volume; CL: clearance from the hepatic central compartment; CL2: hepatic inter-compartment clearance; Q: clearance into the RISC compartment; RV: RISC volume; CLR: clearance out of the RISC compartment; Kin: AT production rate; Kout: AT excretion rate; Imax: maximal inhibition of AT production; IC50: RISC concentration at 50% of maximal inhibition of AT production. [Figure 11] Flowchart showing risk mitigation strategies for vascular thrombotic events. "AT": antithrombin activity; "QM": monthly; "Q2M": every 2 months; "ss": steady state. After discontinuation of fitusiran due to AT levels <15% at a dose of 50 mg Q2M, patients are eligible to resume treatment with fitusiran 20 mg Q2M if their AT levels are ≥22%. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present disclosure provides a method aimed at maintaining a favorable benefit-risk balance for patients with hemophilia A or B, with or without inhibitors, treated with fitusiran. Fitusiran is intended for routine prophylaxis to prevent or reduce the frequency of bleeding episodes in patients with hemophilia A or B, e.g., adult and adolescent patients (≥12 years of age), including those with inhibitory antibodies (inhibitors). The treatment method carefully adjusts therapy based on the patient's AT levels to minimize the risk of vascular thrombotic events that may result from inappropriately low AT levels (e.g., AT levels <10%).

[0029] A hemophilia A or B patient with inhibitors refers to a patient who has developed alloantibodies to a factor he / she previously received (e.g., factor VIII for hemophilia A patients, or factor IX for hemophilia B patients). Hemophilia A or B patients with inhibitors may be refractory to clotting factor replacement therapy. A patient without inhibitors refers to a patient who does not have such alloantibodies. The present treatment methods may be beneficial for hemophilia A patients with or without inhibitors, as well as hemophilia B patients with or without inhibitors. As used herein, "hemophilia A or B with or without inhibitors" refers to hemophilia A with or without inhibitors, or hemophilia B with or without inhibitors. As used herein, patient refers to a human patient, optionally an adolescent or adult human patient aged 12 years or older.

[0030] I. Fitusiran Pharmaceutical Composition Hemophilia results in a significant defect in thrombin generation, and furthermore, the severity of hemophilia correlates with the inability to generate thrombin. Without being bound by theory, it is believed that in patients with hemophilia, fitusiran-mediated reduction in antithrombin (AT) levels increases thrombin generation and therefore improves hemostasis.

[0031] The structure of fitusiran is provided herein. Fitusiran is a synthetic, chemically modified, double-stranded, small interfering RNA (siRNA) oligonucleotide that covalently binds a triantennary N-acetyl-galactosamine (GalNAc) ligand that targets AT3 mRNA in the liver, thereby inhibiting antithrombin synthesis. See, e.g., Pasi, supra. Antithrombin is encoded by the SERPINC1 gene. The nucleosides in each chain of fitusiran are linked through either 3'-5' phosphodiester or phosphorothioate linkages, thus forming the sugar-phosphate backbone of the oligonucleotide.

[0032] The fitusiran dosage weights described herein refer to the weight of fitusiran free acid (active moiety), while administration of fitusiran to a patient herein refers to administration of fitusiran sodium (drug substance) prepared in a pharmaceutically appropriate aqueous solution (e.g., phosphate buffered saline at physiological pH).

[0033] The sense and antisense strands of Phytusilan contain 21 and 23 nucleotides, respectively. The 3' end of the sense strand is conjugated to a GalNAc-containing moiety (designated L96) via a phosphodiester bond. The sense strand contains two consecutive phosphorothioate bonds at its 5' end. The antisense strand has four phosphorothioate bonds, two at the 3' end and two at the 5' end. The 21 nucleotides of the sense strand hybridize with the complementary 21 nucleotides of the antisense strand, thus forming 21 nucleotide base pairs and a two-base overhang at the 3' end of the antisense strand. See also U.S. Patent No. 9,127,274, US20170159053 and WO2019 / 014187.

[0034] The two nucleotide chains of phytusiran are shown below: Sense strand: 5'Gf-ps-Gm-ps-Uf-Um-Af-Am-Cf-Am-Cf-Cf-Af-Um-Uf-Um-Af-Cm-Uf-Um-Cf-Am-Af-L96 3' (SEQ ID NO: 1), and Antisense strand: 5' Um-ps-Uf-ps-Gm-Af-Am-Gf-Um-Af-Am-Af-Um-Gm-Gm-Uf-Gm-Uf-Um-Af-Am-Cf-Cm-ps-Am-ps-Gm 3' (SEQ ID NO: 2) (In the formula, Af = 2'-fluoroadenosine (i.e., 2'-deoxy-2'-fluoroadenosine) Cf = 2'-fluorocytidine (i.e., 2'-deoxy-2'-fluorocytidine) Gf = 2'-fluoroguanosine (i.e., 2'-deoxy-2'-fluoroguanosine) Uf = 2'-fluorouridine (i.e., 2'-deoxy-2'-fluorouridine) Am = 2'-O-methyladenosine Cm = 2'-O-methylcytidine Gm = 2'-O-methylguanosine Um = 2'-O-methyluridine "-" (hyphen) = 3'-5' phosphodiester bond sodium salt "-ps-" = 3'-5' phosphorothioate bond sodium salt and L96 is represented by the following formula: [ka] (having).

[0035] The expanded structural formula, molecular formula and molecular weight of phytusirane are shown in Figure 1.

[0036] The structure of phytosilane is shown in the diagram below. [ka] (wherein X is O) It can also be explained using

[0037] For use in the present treatment methods, dsRNA compound can be prepared in a pharmaceutical composition comprising dsRNA compound and a pharmaceutically acceptable excipient. In certain embodiments, the dsRNA compound is in the form of a sodium salt.

[0038] In some embodiments, fitusiran is provided in an aqueous solution at a concentration of 50-200 mg / mL (e.g., 50-150 mg / mL, 80-110 mg / mL, or 90-110 mg / mL). As used herein, recited ranges and values ​​intermediate thereto are intended to be part of this disclosure. Additionally, ranges of values ​​using any combination of the recited values ​​as upper and / or lower limits are intended to be included. In further embodiments, the pharmaceutical composition comprises fitusiran at a concentration of 50, 75, 100, 125, 150, or 200 mg / mL.

[0039] Unless otherwise specified, the weight of fitusiran listed in this disclosure is the weight of fitusiran free acid (active moiety), even if the patient is injected subcutaneously in its sodium form (in aqueous solution). For example, 100 mg / mL of fitusiran is 100 mg of fitusiran free acid per mL (equivalent to 106 mg of fitusiran sodium, the active drug substance).

[0040] In some embodiments, the pharmaceutical composition contains fitusiran in phosphate-buffered saline. The phosphate concentration in the solution can be 1 to 10 mM (e.g., 2, 3, 4, 5, 6, 7, 8, or 9 mM) at a pH of 6.0 to 8.0. The pharmaceutical compositions herein can contain a preservative, such as EDTA. Alternatively, the pharmaceutical composition does not contain a preservative. In certain embodiments, the fitusiran pharmaceutical composition does not contain a preservative and comprises, consists of, or consists essentially of 100 mg of fitusiran per mL of 5 mM phosphate-buffered saline (PBS) solution. The PBS solution is composed of sodium chloride, disodium phosphate (heptahydrate), and monosodium phosphate (monohydrate). Sodium hydroxide solution and diluted phosphoric acid can be used to adjust the pH of the composition to 7.0.

[0041] The pharmaceutical composition can be provided in a container (e.g., a vial or syringe). The container can contain a single or multiple doses. In some embodiments, the container is a disposable container (e.g., a disposable ampoule or a disposable syringe, e.g., a disposable pre-filled syringe), each containing 10-100 mg (e.g., 10 mg, 20 mg, 25 mg, 40 mg, 50 mg, or 80 mg) of fishiran. Fishiran may be provided in solid form in the container and reconstituted in an aqueous solution (e.g., PBS) before use, with the reconstituted solution containing 50-150 mg / mL (e.g., 100 mg / mL) of fishiran. In some embodiments, fishiran is provided in sodium salt form in a disposable glass vial or a disposable pre-filled syringe (e.g., one with a safety system). In a further embodiment, each vial or syringe contains 80 mg of fitusiran in 0.8 mL of 5 mM phosphate buffered saline solution (pH 7.0) (or 50 mg of fitusiran in 0.5 mL, 20 mg of fitusiran in 0.2 mL, or 10 mg of fitusiran in 0.1 mL); the solution is administered to a patient via subcutaneous injection. The solution can be stored at 2-30°C (e.g., 2-8°C).

[0042] In certain embodiments, the subcutaneous injection composition contains fitusiran in 5 mM phosphate buffered saline at pH 7.0 with 0.64 mM NaH2PO4, 4.36 mM Na2HPO4, and 84 mM NaCl. In certain embodiments, the composition of the subcutaneous injection solution of fitusiran is shown in Table 1 below.

[0043] [Table 1]

[0044] II. Therapeutic Uses of Fitusiran Fitusiran can inhibit hepatic production of antithrombin (AT). AT, in its role as an anticoagulant, regulates hemostasis by either directly targeting thrombin production or by inactivating uncomplexed FXa, which then reduces thrombin production (Quinsey et al., Int J Biochem Cell Biol. (2004) 36(3):386-9). Fitusiran can be used to treat those with impaired hemostasis. For example, fitusiran can be used to treat patients with hemophilia A or B, with or without inhibitors, for routine prophylaxis to prevent or reduce the frequency of bleeding episodes. In certain embodiments, fitusiran is used to treat patients with hemophilia A or B (congenital factor VIII or factor IX deficiency), with or without inhibitors, such as adults and adolescents (≥12 years of age).

[0045] The method involves administering a therapeutically effective amount of fitusiran to a hemophilia patient (e.g., a patient with hemophilia A or B) in need thereof. A "therapeutically effective amount" refers to the amount of fitusiran that helps the patient achieve a desired clinical endpoint. The desired clinical endpoint may be, for example, a reduction in the annualized bleeding rate (ABR) to 3 or less, 2 or less, 1 or less, or zero. A desired clinical endpoint may also be, for example, a reduction in the annualized spontaneous bleeding rate (AsBR) to 1 or less, and preferably to zero.

[0046] This improved treatment method is based, in part, on the discovery that the risk of vascular thrombotic events in patients exposed to fitusiran may increase with lower AT levels. AT measurement can be performed by well-established methods, including both kinetic and chromogenic assays. One commonly used method is the INNOVANCE™ Antithrombin Assay (Siemens Healthineers, Malvern, PA; USFDA 510(k)#K081769). INNOVANCE™ is a chromogenic assay that quantifies functionally active AT in human citrated plasma based on the inhibition of excess factor Xa by AT. The assay may be performed using an automated coagulation instrument (e.g., Siemens BCS® XP, Sysmex® CA-600 and CS systems, or Atellica® COAG 360 system) and may be calibrated using Siemens Standard Human Plasma (SHP), which has a defined AT activity calibrated against the World Health Organization (WHO) reference plasma. An equivalent assay is the Dade Behring Berichrom™ Antithrombin III Assay (Dade Behring Marburg GmbH, Marburg, Germany; USFDA 510(k)#K933125). Each measurement is controlled by two independent controls (low and normal values) also calibrated to WHO standards. AT activity (%) in plasma samples is calculated relative to WHO reference plasma. 100% AT level is defined as 1 unit of antithrombin activity in 1 mL of reference plasma sample. The detection limit of the INNOVANCE™ assay is 6.0%, based on the summary results of the USFDA 510(k) review of the assay. AT levels range from approximately 80% to approximately 120% in the population.

[0047] It has been observed that the risk of arterial thrombotic events may increase among patients receiving fitusiran with AT levels <10%. To mitigate the risk of vascular thrombotic events while maintaining a favorable benefit-risk balance for patients receiving fitusiran, patients, e.g., adult patients (≥18 years old) or adolescent patients (12-17 years old, inclusive), can begin fitusiran therapy with a 50 mg subcutaneous injection of fitusiran every two months (or every eight weeks). The patient's AT levels are monitored periodically (e.g., every 1, 2, 3, 4, 5, 6, 7, or 8 weeks, or every 1, 2, 3, 4, 5, or 6 months). If the patient has two AT measurements of <15% (e.g., <10%), the patient discontinues fitusiran treatment. In some embodiments, if the initial AT level is <15%, the patient has another AT activity level sample taken within one month (e.g., within one to two weeks). If this result is <15%, this is considered a second AT <15%. Patients receiving fitusiran at a dose of 50 mg Q2M who have more than one (e.g., two) AT activity levels <15% will discontinue fitusiran.

[0048] However, if a patient on 50 mg / Q2M (or Q8W) has two AT measurements >25% (e.g., >35%), the patient's dosing regimen is titrated as illustrated in Figures 7-9. In the approach of Figure 7, the patient can receive fitusiran at 50 mg monthly (or every 4 weeks); if the patient on the 50 mg / QM (Q4W) regimen has two AT measurements >25% (e.g., >35%), the patient can receive fitusiran at 80 mg monthly (or every 4 weeks). In the approach of Figure 8, a patient on 50mg / Q2M (or Q8W) can receive fitusiran at 80mg every 2 months (or every 8 weeks); if a patient has two AT measurements of >25% (e.g., 35%) under the 80mg / Q2M (or Q8W) regimen, the patient can receive fitusiran at 50mg monthly (or every 4 weeks); if he has two AT measurements of >25% (e.g., 35%) under the 50mg / QM (or Q4W) regimen, he can receive fitusiran at 80mg monthly (or every 4 weeks). In the approach of Figure 9, patients on 50mg / Q2M (or Q8W) can receive fitusiran at 80mg every 2 months (or every 8 weeks); if a patient has two AT measurements of >25% (e.g., >35%) on the 80mg / Q2M (or Q8W) regimen, the patient can receive fitusiran at 80mg monthly (or every 4 weeks).

[0049] Patients who discontinue fitusiran after having more than one (e.g., two) AT activity levels <15% while receiving fitusiran at a dose of 50 mg Q2M can receive fitusiran at a dose of 20 mg Q2M once their AT levels return to ≥22% (Figure 11). Patients receiving fitusiran at a dose of 20 mg Q2M who have more than one (e.g., two) AT activity levels <15% will discontinue fitusiran treatment. If a patient receiving fitusiran at a dose of 20 mg Q2M (or Q8W) has two AT measurements >25% (e.g., >35%), the patient can receive fitusiran at 20 mg QM or Q4W.

[0050] In the above-described titration regimen, AT measurements for dosing are obtained during steady-state (SS) of AT activity, i.e., after the patient's AT levels have stabilized (in the low AT activity range) following fitusiran treatment. SS is typically achieved after two or three doses of fitusiran. AT measurements for dosing are obtained at appropriate intervals (e.g., every four or eight weeks).

[0051] In the above-mentioned dose setting regimen, a starting dose of 50 mg of fitusiran Q2M is taken as an illustrative example. For example, the starting dose of fitusiran may be 50 mg Q2M, 20 mg Q2M, 20 mg QM, or 10 mg QM. Then, the dose can be gradually increased or decreased from each starting dose as appropriate. For example, the starting dose of 20 mg Q2M fitusiran can be gradually increased to 20 mg QM, 50 mg Q2M, 50 mg QM, or 80 mg QM, optionally in this order, or can be gradually decreased to 10 mg QM.

[0052] An AT level of 10-35% (e.g., 10-25%, 15-35%, or 15-25%) is targeted to mitigate the risk of vascular thrombotic events while maintaining a favorable benefit-risk balance for patients receiving fitusiran. Thus, as long as a patient achieves this targeted AT level, the patient does not need to receive a higher or more frequent dose of fitusiran. In other words, the patient remains on their current treatment regimen (i.e., maintenance regimen). For example, once the desired AT level is achieved, the patient is treated with subcutaneous doses of fitusiran (e.g., 40-90 mg per dose), for example, every 1, 2, 3, 4, 5, 6, 7, or 8 weeks, or every 1, 2, 3, 4, 5, or 6 months. In some embodiments, if a patient has two AT measurements of 35% or less while receiving 50 mg Q2M, the patient remains on this dosing regimen, with no further escalation of the dosage or dosing frequency required. As another example, if a patient has two AT measurements of 35% or less while receiving 80 mg Q2M or 50 mg QM, they remain on this dosing regimen and do not need to further titrate either the dosage or the dosing frequency (e.g., to 80 mg QM). However, if a patient has two or more (e.g., two) AT measurements of <15% (e.g., <10%) as a risk mitigation measure for vascular thrombotic events, fitusiran treatment should be discontinued. Alternatively, patients can resume treatment with a lower dose of fitusiran after their AT levels return to above 15%, e.g., ≥22%.

[0053] In some embodiments of the maintenance regimen, patients with hemophilia A or B, with or without inhibitors, are treated every two months (or every eight weeks) with a subcutaneous dose of 50 mg of fitusiran per dose. In other embodiments, patients with hemophilia A or B, with or without inhibitors, are treated every month (or every four weeks) with a subcutaneous dose of 50 mg of fitusiran. In yet other embodiments, patients with hemophilia A or B, with or without inhibitors, are treated every two months (or every eight weeks) with a subcutaneous dose of 80 mg of fitusiran. In yet other embodiments, patients with hemophilia A or B, with or without inhibitors, are treated every month (or every four weeks) with a subcutaneous dose of 80 mg of fitusiran. In yet other embodiments, patients with hemophilia A or B, with or without inhibitors, are treated every two months (or every eight weeks) with a subcutaneous dose of 20 mg of fitusiran. In yet another embodiment, patients with hemophilia A or B, with or without inhibitors, are treated monthly (or every four weeks) with a 20 mg subcutaneous dose of fitusiran. In yet another embodiment, patients with hemophilia A or B, with or without inhibitors, are treated monthly (or every four weeks) with a 10 mg subcutaneous dose of fitusiran.

[0054] In some embodiments, after changing the fitusiran dosing regimen, the patient may undergo regular (e.g., monthly or every four weeks) AT monitoring for 12 months.

[0055] In some embodiments, when a patient remains on a maintenance regimen (e.g., 10 mg QM or Q4W, 20 mg Q2M or Q8W, 20 mg QM or Q4W, 50 mg Q2M or Q8W, 50 mg QM or Q4W, 80 mg QM or Q4W, or 80 mg Q2M or Q8W), the patient can undergo less frequent AT monitoring. For example, their AT levels can be monitored monthly, every two months, every three months, every four months, every six months, every year, or every two years.

[0056] III. Patient Management Patients receiving fitusiran should be monitored for hemostatic parameters, such as coagulation parameters (D-dimer, prothrombin fragments 1+2, and fibrinogen), as well as for signs and symptoms of vascular thrombotic events. These include, but are not limited to, severe or persistent headache, headache accompanied by nausea and vomiting, chest pain and / or tightness, hemoptysis, dyspnea, abdominal pain, syncope or loss of consciousness, swelling or pain in the arms or legs, impaired vision, weakness and / or loss of sensation, and changes in speech. Evaluation of signs and symptoms that may be consistent with intravascular thrombosis should include appropriate imaging studies, if applicable. Magnetic resonance venography (MRV) or computed tomography venography (CTV) is recommended for the diagnosis of cerebral venous sinus thrombosis.

[0057] If a patient develops thrombosis while receiving fitusiran, AT reversal may be administered in combination with replacement factors or BPA and appropriate anticoagulation therapy. AT reversal should follow the product's labeling recommendations for the prevention of perioperative thrombosis in patients with AT deficiency, and the patient's dose should be individualized to target 80-120% AT activity. The use of plasma-derived AT may be preferable to recombinant AT, given its long half-life.

[0058] Bleeding events in patients receiving fitusiran can be managed with on-demand administration of replacement factors (recombinant or plasma-derived factor VIII or IX) or BPA (e.g., fresh frozen plasma (FFP); rFVIIa, and aPCC). The amount of factor or BPA must be reduced in patients receiving fitusiran to prevent intravascular thrombosis. See, e.g., WO2019 / 014187.

[0059] IV. Illustrative Embodiments Further non-limiting exemplary embodiments of the present disclosure are set forth below. 1. A method for prophylactic treatment of patients with hemophilia A or B, regardless of the presence or absence of inhibitors, comprising: a) subcutaneously administering 50 mg of fitusiran to a patient who needs it every two months or every eight weeks; b) obtaining a measured value of the antithrombin (AT) level in the patient; and c) when the AT level is >X% (where X = 25 or 35), subcutaneously administering 80 mg of fitusiran to the patient every two months or every eight weeks, or subcutaneously administering 50 mg of fitusiran to the patient every month or every four weeks A method comprising the above steps. 2. A method for reducing the thrombosis risk in a patient receiving fitusiran for prophylactic treatment of hemophilia A or B, regardless of the presence or absence of inhibitors, comprising: a) subcutaneously administering 50 mg of fitusiran to a patient who needs it every two months or every eight weeks; b) obtaining a measured value of the antithrombin (AT) level in the patient; and c) when the AT level is >X% (where X = 25 or 35), subcutaneously administering 80 mg of fitusiran to the patient every two months or every eight weeks, or subcutaneously administering 50 mg of fitusiran to the patient every month or every four weeks A method comprising the above steps. 3. The method according to embodiment 1 or 2, further comprising: d) continuing step a) when the AT level is Y-X% (where Y = 10 or 15). 4. The method according to any one of embodiments 1 to 3, further comprising: e) stopping the fitusiran treatment when the AT level is <Y% (where Y = 10 or 15). 5. The method according to any one of embodiments 1 to 4, wherein step b) is performed at least twice, step c) is performed only when both measured AT levels are >X%, or step e) is performed only when both measured AT levels are <Y%. 6. After performing step c): i) obtaining a measured value of the AT level in the patient; and ii) administering 80 mg of fitusiran subcutaneously to the patient monthly or every four weeks if the AT level in step i) is >25% or >35%; or iii) Otherwise, continue with step c). 6. The method of any one of embodiments 1 to 5, further comprising: 7. The method of embodiment 6, wherein step i) is performed at least twice, and step ii) is performed only if the measured AT levels in step i) are both >25% or >35%. 8. After step c) comprising administering to the patient 80 mg of fitusiran subcutaneously every 2 months or every 8 weeks: i) obtaining AT level measurements in the patient; and ii) administering 50 mg of fitusiran subcutaneously to the patient monthly or every four weeks if the AT level in step i) is >25% or >35%; or iii) Otherwise, continue with step c). 6. The method of any one of embodiments 1 to 5, further comprising: 9. The method of embodiment 8, wherein step i) is performed at least twice, and step ii) is performed only if the measured AT levels in step ii) are both >25% or >35%. 10. After performing step ii): A) obtaining an AT level measurement in a patient; and B) if the AT level in step A) is >25% or >35%, administering 80 mg of fitusiran subcutaneously to the patient monthly or every 4 weeks; or C) Otherwise, continue with step ii). 10. The method of embodiment 8 or 9, further comprising: 11. The method of embodiment 10, wherein step A) is performed at least twice and step B) is performed only if the measured AT levels are both >25% or >35%. 12. A method for the prophylactic treatment of patients with hemophilia A or B, with or without inhibitors, in which the patient is 12 years of age or older and comprises: (a) administering fitusiran subcutaneously to a patient in need thereof at a starting dose and at a selected dosing frequency; (b) obtaining a measurement of antithrombin (AT) levels in the patient; and (c) the steps of: (i) repeating step (a) if the AT level is between 15 and 35%; (ii) if the AT level is >35%, administering to the patient subcutaneously fitusiran at a higher dose and at a selected dosing frequency, or at a starting dose and at a higher dosing frequency; or (iii) discontinuing or pausing fitusiran treatment if AT levels are <15%. A process of performing one of the following: A method comprising: 13. A method for reducing the risk of thrombosis in patients receiving fitusiran for prophylaxis of hemophilia A or B with or without inhibitors, wherein the patient is 12 years of age or older and comprises: (a) administering fitusiran subcutaneously to a patient in need thereof at a starting dose and at a selected dosing frequency; (b) obtaining a measurement of antithrombin (AT) levels in the patient; and (c) the steps of: (i) repeating step (a) if the AT level is between 15 and 35%; (ii) if the AT level is >35%, administering to the patient subcutaneously fitusiran at a higher dose and at a selected dosing frequency, or at a starting dose and at a higher dosing frequency; or (iii) discontinuing or pausing fitusiran treatment if AT levels are <15%. A process of performing one of the following: A method comprising: 14. The method of embodiment 12 or 13, wherein the starting dose of fitusiran is selected from 10 mg to 50 mg. 15. The method of any one of embodiments 12-14, wherein the selected dosing frequency is every 2 months (Q2M) or every 8 weeks (Q8W), and optionally, the higher dosing frequency is monthly (QM) or every 4 weeks (Q4W). 16. The method of embodiment 15, wherein the starting dose is 20 mg and the selected dosing frequency is Q2M or Q8W. 17. The starting dose is 50 mg and the selected dosing frequency is Q2M or Q8W, if applicable. step (c)(ii) is performed if the two measurements of AT level are >35%, or 16. The method of embodiment 15, wherein step (c)(iii) is performed if two or more, optionally two, measurements of the AT level are <15%. 18. The method of embodiment 17, wherein step (c)(ii) comprises subcutaneously administering fitusiran to the patient at 50 mg QM. 19. The method of embodiment 18, comprising the step of administering 80 mg QM of fitusiran subcutaneously to the patient after step (c)(ii) if the AT level in the patient after step (c)(ii) is >35%, optionally by two measurements. 20. After step (c)(iii): (A) administering fitusiran 20 mg Q2M subcutaneously to a patient; (B) The patient's AT level after step (A) If the measured value is <15%, discontinue the treatment with Fitusiran or If it is between 15 and 35%, repeat step (A), or optionally, if both measurements are >35%, administering fitusiran 20 mg QM subcutaneously to the patient. 20. The method of any one of embodiments 17-19, comprising: 21. The method further comprising subcutaneously administering fitusiran to the patient at a dosage and dosing frequency sufficient to maintain AT levels in the patient at 15-35%, optionally comprising administering fitusiran to the patient by: 10mg QM or Q4W, 20mg QM or Q4W, 20mg Q2M or Q8W 50mg QM or Q4W, 50 mg Q2M or Q8W, or 80mg QM or Q4W and administering the compound subcutaneously. 10. The method of any one of the preceding embodiments, comprising: 22. The method of any one of embodiments 1-21, wherein the AT level measurement is obtained after the patient has received at least two doses of fitusiran in the previous step. 23. A method for the prophylactic treatment of patients with hemophilia A or B, with or without inhibitors, comprising administering 50 or 80 mg of fitusiran subcutaneously every two months or every eight weeks to a patient in need thereof, optionally wherein the patient is 12 years of age or older. 24. A method for the prophylactic treatment of patients with hemophilia A or B, with or without inhibitors, the patient being 12 years of age or older, comprising administering 20 mg of fitusiran subcutaneously to a patient in need thereof monthly or every 4 weeks, or every 2 months or every 8 weeks. 25. A method for the prophylactic treatment of patients with hemophilia A or B, with or without inhibitors, the patient being 12 years of age or older, comprising administering 10 mg of fitusiran subcutaneously monthly or every four weeks to a patient in need thereof. 26. The method of any one of embodiments 1-25, comprising obtaining measurements of AT levels in the patient every 4 weeks, every 8 weeks, every month, every 2 months, every 6 months, or every 12 months. 27. The method of any one of embodiments 1-26, wherein the fitusiran is provided at 50-200 mg / mL, optionally 100 mg / mL, in phosphate buffered saline (PBS), optionally wherein the PBS has a pH of 7. 28. Phytusiran for use in the method of any one of embodiments 1 to 27. 29. An article of manufacture for use in the method of any one of embodiments 1-27, optionally a kit. 30. An article of manufacture for use according to embodiment 29, comprising a container containing one or more doses of fitusiran, each dose being 80 mg, 50 mg, 20 mg or 10 mg, and optionally 80 mg of Fitusiran is in 0.8 mL of phosphate buffered saline (PBS) or Fitusiran 50mg in 0.5mL of PBS 20 mg of Fitusiran is in 0.2 mL of PBS, or 10 mg of fitusiran is in 0.1 mL of PBS. Optionally, the PBS has a pH of 7. 31. The article of manufacture for use of embodiment 30, wherein the container is a disposable, single-dose pre-filled syringe. 32. Use of fitusiran for the manufacture of a medicament for treating hemophilia in the method of any one of embodiments 1 to 27.

[0060] Unless otherwise defined herein, scientific and technical terms used in connection with this disclosure shall have the meanings commonly understood by those skilled in the art. Exemplary methods and materials are described below, although methods and materials similar or equivalent to those described herein can also be used to practice or test the present disclosure. In the event of a conflict, the present specification, including definitions, will control. Generally, the nomenclature used in connection with and in the arts of hematology, medicine, pharmaceutical and medicinal chemistry, and cell biology described herein is that which is well known and commonly used in the art. Furthermore, unless otherwise required by context, singular terms shall include pluralities, and plural terms shall include the singular. Throughout this specification and scope of embodiments, the words "have," "comprise," or variations such as "has," "having," "comprises," or "comprising" shall be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers. All publications and other references mentioned herein are incorporated by reference in their entirety. Although several documents are cited herein, this citation does not acknowledge that any of these documents form part of the common general knowledge in the art.As used herein, the term "approximately" or "about", when applied to one or more target values, refers to a value similar to the stated reference value.In certain embodiments, unless otherwise indicated or otherwise clear from the context, the term refers to a range of values ​​that applies in either direction (greater or less) within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1% or less.

[0061] In order that this invention may be better understood, the following examples are set forth. These examples are for illustrative purposes only and are not to be construed as limiting the scope of this invention in any way. [Example]

[0062] Evaluation of vascular thrombotic events during fitusiran treatment Hemostasis is a highly complex biological process. To improve the safety of fitusiran treatment in patients with hemophilia A and B, the incidence and risk of vascular thrombotic events in patients were carefully monitored in clinical trials.

[0063] A Phase I clinical trial of fitusiran has been completed. In one group ("Part B"), 12 male patients with hemophilia A or B without inhibitors were treated with a weekly regimen of fitusiran ranging from 0.015 mg / kg to 0.075 mg / kg for three weeks. In another group ("Part C"), 18 male patients without inhibitors (including the five patients who received fitusiran in the previous group) received a monthly regimen of fitusiran ranging from 0.225 mg / kg to 1.8 mg / kg or a fixed dose of 80 mg for three months. In yet another group ("Part D"), 17 male patients with inhibitors received a fixed dose of fitusiran of 50 mg or 80 mg for one month. All doses were administered subcutaneously. Serum samples were collected after fitusiran administration to monitor AT protein levels, AT activity, and the duration of AT protein silencing. AT protein levels were monitored using ELISA, and AT activity levels were monitored using a chromogenic assay for quantification of functionally active AT. Thrombin generation (TG) was measured by generating a thrombin generation curve using a calibrated automated thrombinoscope (tissue factor = 1 pM). The fold change in peak thrombin was calculated relative to the mean peak thrombin value for each subject relative to the two pre-dose values.

[0064] No vascular thrombotic events were reported in the Phase I study. Any bleeding events were successfully managed with standard replacement factor or bypassing agent administration. Furthermore, there were no cases of anti-drug antibody (ADA) formation. AT knockdown in patients is described in International Publication WO2017 / 100236.

[0065] Further studies have been initiated to evaluate the safety and efficacy of fitusiran in male adult and adolescent patients (≥12 years of age) with hemophilia A or B, with or without moderate or severe inhibitors. Vascular (arterial) thrombotic events have been reported. [Example]

[0066] Analysis of the association of AT levels with thrombotic events Based on the mechanism of action of fitusiran and the observation that multiple AT measurements were less than 10% in patients with reported thrombotic events, we considered AT levels to be a possible contributor and evaluated this as a potential modifiable target for risk mitigation. Specific analyses were performed, including AT levels in both the fitusiran population and patients with vascular thrombotic events, the incidence of vascular thrombotic events by AT level, intrapatient variability in AT measurements, annualized bleeding rate (ABR) by AT level, and simulations to predict AT measurements using various fitusiran dosing regimens.

[0067] AT levels in A. fitusirans populations The AT activity for the five patients who experienced vascular thrombotic events was graphically compared with the AT activity levels of all patients treated with fitusiran in the phase 3 trial. Figure 2 shows the comparison of AT activity profiles between the phase 3 patients and the five patients with vascular thrombotic events over real-time, weekly intervals. Only patients who initiated fitusiran were included in this graphical analysis. Figure 2 shows that the AT activity of the five patients with vascular thrombotic events was generally within the range of the AT levels of other patients in the phase 3 trial. However, the AT levels for the three patients with arterial thrombotic events (patients 1, 4, and 5) were generally lower than those of the two patients with venous thrombosis who used factors or bypassing agents beyond the revised bleeding management guidelines (patients 2 and 3).

[0068] B. Incidence of vascular thrombotic events according to AT levels The incidence rate (IR) of vascular thrombotic events by AT level was determined. For all patients exposed to at least one dose of fitusiran, total patient-years were calculated for each of three AT classifications: <10%, 10-20%, and >20%. Some patients had two consecutive AT measurements separated by a long period of time. For these patients, their AT levels were assumed to be stable for 90 days following the previous measurement and missing until the next AT measurement. The five patients with vascular thrombotic events were then included in the AT classification representing their levels for the greatest amount of time between fitusiran exposures, and an IR per 100 patient-years was derived (Table 2: TE: thrombotic events).

[0069] [Table 2]

[0070] The IRs for vascular thrombotic events in the AT classifications <10%, 10-20%, and >20% were 5.91, 1.49, and 0 per 100 patient-years, respectively. Note that patients with vascular thrombotic events included in the AT classification <10% represent those with arterial (or suspected arterial) thrombosis (cerebral infarction, cerebrovascular accident, and vertebral vasculopathy), whereas those included in the AT classification 10-20% represent those with venous events (cerebral venous sinus thrombosis and atrial thrombosis) that occurred in the setting of the use of factors or bypassing agents beyond the revised guidelines for bleeding management.

[0071] The etiology of vascular thrombotic events in the Fitsiran cohort was likely multifactorial. However, these data suggest that the risk of vascular thrombotic events may increase with lower AT levels; specifically, the risk of arterial thrombotic events may be greater at AT levels <10%. A reduction in AT reduction is a potential risk mitigation measure for vascular thrombotic events and can be achieved with changes in medication regimens (dose and / or frequency).

[0072] C.AT levels and intra-individual variability Intra-individual variability was assessed to determine appropriate AT targets to minimize levels <10%. Intra-individual variability in AT activity was assessed during steady state. This was done after patients' AT levels stabilized (in the low AT activity range) after fitusiran treatment, allowing for the assessment of intra-patient variability in AT activity. To estimate intra-individual variability, AT activity assessments from days 56 to 196 were used from patients receiving fitusiran treatment. Day 56 was selected as the starting time because, with an 80 mg monthly regimen, patients would be expected to reach a stable AT activity by day 56. Among all phase 3 patients with AT activity measured between days 56 and 196, patients with an AT activity assessment of less than 4 were excluded. Patients who experienced significant dose interruptions between days 56 and 196 were also excluded from the intra-individual variability assessment. Additionally, five patients who experienced thrombotic events were included in the steady-state intra-individual variability assessment, even if any of these patients had an AT observation of <4.

[0073] Overall, AT activity measurements from 139 patients out of a total of 259 patients enrolled met the required criteria described above and were used to assess intra-individual variability. For each of the 139 patients, the mean, standard deviation (SD), and coefficient of variation (%CV) of intra-patient AT activity were calculated; %CV was calculated as the mean SD. * Calculated as 100 / mean value. The distribution of %CV for eligible patients is shown in Figure 3. The median, 90th percentile, and 95th percentile for %CV were 13.4%, 20.3%, and 22.4%, respectively; represented by the vertical red line, vertical blue line, and vertical green line, respectively.

[0074] The 95th percentile for the %CV of 22.4% results in lower bounds of 90% confidence intervals of 9.5% and 10.1% when applied to 15% and 16% AT activity, respectively, indicating that an AT activity level of 15% is a reasonable threshold for minimizing the occurrence of AT activity levels <10%.

[0075] In addition to the above analysis, the lowest threshold of mean AT to achieve a new AT > 10% was calculated based on the 80 mg monthly dosing regimen in the selected studies. Inter- and intra-subject standard deviations were obtained (3.8% and 3.26%, respectively). Next, N steady-state AT observations were assumed (N = 1, 2, 3, ...). The new steady-state posterior distribution was derived based on the steady-state AT values ​​to obtain the lower threshold of mean AT to achieve a 95% probability of a new AT > 10%.

[0076] Following 10–15 AT observations, if the average AT level is approximately 15%, there is a 95% probability that the next AT level will be >10% (Figure 4). This analysis further supports the selection of a 15% AT threshold to minimize the occurrence of AT activity levels <10%.

[0077] D. Antithrombin Levels and Efficacy 1. Antithrombin The coagulation system is a balanced process with the need to maintain hemostasis and prevent thrombosis. This balance is achieved through a well-described, interrelated cascade consisting of both procoagulant factors (e.g., FVIII, FIX) and anticoagulant factors (e.g., AT and protein C). Antithrombin (formerly known as ATIII) is an anticoagulant expressed in the liver that is the primary endogenous inhibitor of thrombin and other serine proteases, such as factor Xa and factor IXa. Based on the therapeutic hypothesis of fitusiran, increased thrombin generation is predicted when AT is reduced. Fitusiran's efficacy has been shown to be associated with a reduction in AT levels to approximately 75% of normal. Therefore, an upper threshold for AT levels is analyzed to maintain efficacy while minimizing safety risks.

[0078] 2. Reduction of AT improves thrombin generation in hemophilia plasma This relationship between AT and thrombin generation (TG) was explored in a phase I study. In this analysis, all available peak thrombin values ​​were grouped according to their paired AT levels. The available peak thrombin values ​​for patients in Parts B and C, grouped by quartiles of AT reduction, are presented in Figure 5. Peak thrombin values ​​for healthy volunteers participating in Part A are also presented. These data show that thrombin generation increases with increasing AT reduction. Note that the median peak thrombin values ​​in the highest quartile of AT reduction (AT reduction >75%) approached the lower end of the range seen in healthy volunteers.

[0079] 3. Relationship between AT level and bleeding An initial post-hoc analysis to determine the relationship of bleeding to AT levels was performed using data from a phase 1 study investigating the safety, tolerability, and pharmacokinetics of fitusiran. For the 16 patients with AT reductions >75% and >1100 cumulative days, bleeding events were grouped by AT quartile (Figure 5). Based on this early data, bleeding events were clearly reduced in patients with AT reductions >75% compared with patients with less AT reduction, with only 11 bleeding events in 1128 cumulative days, resulting in a median ABR of 1 (Figure 6). In summary, when AT reductions were >75% of normal, TG levels approached the lower end of the normal range for healthy volunteers (Figure 5), and the median ABR was observed to be 1 (Figure 6). Therefore, the optimal therapeutic range for fitusiran was determined to be when AT levels were >75% of normal or when AT levels remained in the remaining 25% of normal.

[0080] To further expand our understanding of the relationship between bleeding episodes and AT levels, we conducted an ad hoc analysis of bleeding data from available blinded clinical trials in relation to AT levels. The goal of this analysis was to understand the distribution of ABRs by AT levels above or below 20%. Patients in the selected trials were divided into AT levels <10%, 10-15%, 15-20%, and >20%. In 74 patients with AT levels <10%, the median ABR was 0.0; in 116 patients with AT levels between 10% and 15%, the median ABR was 1.09; in 14 patients with AT levels between 15% and 20%, the median ABR observed was 0.17; and in 29 patients with AT levels >20%, the median ABR was 1.35 (Table 3).

[0081] [Table 3]

[0082] This analysis reinforced previous data that AT levels <25% had improved efficacy, with all subgroups below 20% having an ABR of 1 or less, similar to currently marketed treatments.

[0083] Here, significant data exist that provide clarity on the relationship of bleeding to lower threshold AT levels, but the upper bound of this relationship beyond AT levels <25% remains a challenge and will require further modeling.

[0084] 4. Upper threshold of AT activity Based on the relationship between ABR and AT activity reduction in the phase I study and the number of PK / PD replicates for event modeling, a >75% AT reduction was determined to be optimal for efficacy, which translates to an AT activity of approximately <25% being optimal for efficacy. Furthermore, extrapolating from the analysis to determine the lower AT activity threshold, assuming an intraindividual variability %CV estimate of 22.4%, the upper bounds of the 90% and 95% confidence intervals are 34.2% and 35.9%, respectively, making the planned upper threshold of 35% AT a reasonable target for patients to be expected to maintain efficacy while accounting for intraindividual variability in AT activity.

[0085] E. Simulation of medication regimens A pharmacokinetic / pharmacodynamic (PK / PD) model describing the kinetics of plasma AT activity for patients treated with fitusiran was developed and updated based on AT activity data from 45 subjects in a phase 1 study (ALN-AT3SC-001) and a phase 2 study (LTE14762). The model's parameter estimates are shown in Table 4. The PK / PD model was further validated using phase 3 AT activity data, and validation showed that the model could reasonably capture the central tendency and variability in the phase 3 AT activity data. Using the PK / PD model with estimated parameters as shown in Table 4, steady-state AT activity for different dosing scenarios in 1,000 hypothetical patients was simulated. Each hypothetical patient was simulated using a unique combination of PK / PD parameters, taking into account intraindividual variability. The goal of the simulation was to identify dosing regimens that could help a large number of patients maintain AT activity between the lower threshold (15%) and upper threshold (35%).

[0086] [Table 4]

[0087] The simulation results are shown in Table 5, where Q2M and QM refer to fitusiran dosing every 8 weeks and every 4 weeks, respectively; TroughAT and PeakAT are trough and peak AT activities at steady state; 5th, Median, and 95th refer to the 5th percentile, median, and 95th percentile, respectively.

[0088] [Table 5]

[0089] Simulation results show that with the 80 mg QM regimen, AT activity is generally lower than with the 50 mg QM and 50 mg Q2M regimens. Regarding the similarity in peak and trough AT activity, there is significant overlap between the AT activity ranges of the 80 mg QM (9.11-23.55) and 50 mg QM (11.36-31.15). For the 50 mg Q2M regimen, the variability between trough and peak AT activity is higher due to the longer dosing interval. Based on the simulation results, modifying the Fitusiran dosing regimen to 50 mg Q2M is predicted to achieve AT activity greater than 10% for all patients.

[0090] Based on the results of these simulations, taking into account intra-individual variability, steady-state peak AT activity in patients receiving the 50 mg Q2M regimen ranges between 17.9% at the 5th percentile and 56.4% at the 95th percentile (Table 5). Thus, approximately 50% of patients have a steady-state peak AT activity greater than 25% when administered with a 50 mg Q2M dose. To maintain efficacy in these patients with higher AT activity, dose escalation from 50 mg Q2M to 50 mg QM should be considered. Specifically, patients with two peak AT assessments of >35% at steady state after starting with an initial dose of 50 mg Q2 would be considered for dose escalation to 50 mg QM. As noted above, a threshold of 35% peak AT activity at steady state is selected to provide some buffering beyond the effective range (<25% AT activity) while taking into account intra-individual variability in AT activity before considering dose escalation. Peak AT activity is predicted to occur immediately before the next dose is administered, i.e., 2 months or 8 weeks after the previous 50 mg Q2M dose. Patients receiving the 50 mg QM regimen who may have peak AT activity at steady state >35% for two consecutive assessments may need to have their dose titrated to the 80 mg QM regimen.

[0091] F. Summary In summary, the data suggest that lower AT levels may increase the risk of vascular thrombotic events in patients exposed to fitusiran; specifically, AT levels <10% may be associated with a greater risk of arterial thrombotic events. Based on intra-individual variability, a lower AT threshold of 15% was selected to minimize the occurrence of AT levels <10%.

[0092] The efficacy of fitusiran, with a median ABR of 1, observed when AT levels were below 25%, was experimentally determined in a Phase 1 clinical trial and confirmed in a Phase 3 clinical trial. Given intra-individual variability, this could mean AT levels of 35% or less. Therefore, patients are predicted to have reasonable efficacy up to 35% AT.

[0093] Using a PK / PD model describing AT activity in response to fitusiran treatment, a starting dose of 50 mg Q2M is selected to ensure that a large number of patients meet the goal of >10% AT activity. As depicted in Figure 7, if a patient has >35% peak AT activity at two steady states, a dose escalation from 50 mg Q2M to 50 mg QM, followed by 50 mg QM to 80 mg QM, would be recommended. Alternatively, as depicted in Figure 8, if a patient has >35% peak AT activity at two steady states, a dose escalation from 50 mg Q2M to 80 mg Q2M, followed by 80 mg Q2M to 50 mg QM, followed by 50 mg QM to 80 mg QM, would be recommended. Alternatively, as depicted in Figure 9, if a patient has >35% peak AT activity at two steady states, a dose escalation from 50 mg Q2M to 80 mg Q2M, followed by 80 mg Q2M to 80 mg QM, would be recommended. [Example]

[0094] Further revision of dosing guidance based on updated PK / PD models In a phase 3 open-label extension study of the long-term safety, PK, PD, and exploratory clinical activity of fitusiran, 50 of 203 patients (24.6%) who received fitusiran at a dose of 50 mg Q2M experienced two AT activity levels <15% and discontinued fitusiran per the study protocol. The PK / PD model was subsequently updated. All PK / PD modeling was performed with the goal of finding a dosing regimen that could maintain AT activity between 15% and 35%. The revised model presented in this example is an updated version of the model presented in Example 2.

[0095] A. Pharmacokinetic / Pharmacodynamic (PK / PD) Modeling Update The PK / PD model (Figure 10) was updated with AT activity data from 274 subjects from Phase 1, Phase 2, and Phase 3 studies, with the Phase 3 data including patients treated with fitusiran at doses of 80 mg QM and 50 mg Q2M.

[0096] The parameter estimates for the updated model are presented in Table 6, which updates the parameter estimates presented in Table 4.

[0097] [Table 6]

[0098] B. Medication Regimen Simulation The updated PK / PD model with estimated parameters was used to simulate steady-state AT activity for different dosing scenarios in a hypothetical population of 1,000 patients. The simulated dosing regimens were 80 mg QM, 50 mg QM, 50 mg Q2M, 20 mg QM, 20 mg Q2M, and 10 mg QM, with the goal of maintaining patient AT activity in the range of 15%≦AT≦35%. The results of the simulation are shown in Table 7, which updates the simulated AT activity presented in Table 5.

[0099] [Table 7]

[0100] Based on the simulation results from Table 7, under the 50 mg Q2M dosing regimen, approximately 45.7% of the hypothetical subjects are predicted to have an AT activity of <15% and therefore may require dose tapering.

[0101] Simulations of the lower dosing regimens, i.e., 20 mg Q2M and 20 mg QM, in 1,000 new virtual subjects predict that 3.8% and 23.4% of subjects will have AT activity levels of <15%. Therefore, based on the simulations, 20 mg Q2M is considered an appropriate tapering regimen for the 45.7% of subjects who will have AT activity levels of <15% at 50 mg Q2M. When tapered to 20 mg Q2M, approximately 8% of tapered subjects will have AT activity levels of <15% and approximately 7% of tapered subjects will have AT activity levels of >35%, while the remaining 84% to 85% of tapered subjects are predicted to have AT activity levels within the target AT window of 15% to 35%.

[0102] Additionally, current data and modeling considering these data suggest that some subjects are highly sensitive to fitusiran and have low AT activity levels (<15%) even at the 50 mg Q2M dosing regimen. For these specific subjects, an additional, lower-dosing cohort was implemented with the goal of maintaining the potential benefits of fitusiran treatment while adequately mitigating risk.

[0103] Subjects who start at 50 mg Q2M and have an AT activity level >35% have the option to escalate their dose to 50 mg QM. If 50 mg QM also results in an AT activity level >35%, subjects can be escalated to 80 mg QM. Clinical criteria for dose escalation were also included, with the goal of achieving adequate efficacy while maintaining AT levels above 15%.

[0104] C. Summary To mitigate the risk of vascular thrombotic events in patients receiving fitusiran, clinical trials were revised by modifying the fitusiran dose and regimen to reduce AT level decline. Specifically, to provide an option for patients receiving the 50 mg Q2M fitusiran dose with AT levels <15%, the Phase 3 clinical trial protocol was amended to include a lower-dose cohort with a reduced dose of 20 mg Q2M and the possibility of titration to 20 mg Q2M (Figure 11). At the 20 mg Q2M dose, patients with two or more AT levels <15% within 12 months are required to discontinue fitusiran. Patients with two steady-state AT levels >35% can be titrated to the 20 mg Q2M dose.

[0105] The newly proposed dosing scheme introduces a reduced dose of fitusiran based on an updated PK / PD model. Overall, the dosing strategy is still designed to aim to achieve an AT activity level between 15% and 35%, thus maintaining a favorable benefit-risk balance for patients receiving fitusiran.

Claims

1. 1. A pharmaceutical composition comprising fitusiran for use in a method for the prophylactic treatment of patients with hemophilia A or B with or without inhibitors, the method comprising: (a) administering a starting dose of fitusiran subcutaneously at a selected dosing frequency to a patient in need thereof; (b) obtaining a measurement of antithrombin (AT) levels in the patient; and (c) the steps of: (i) repeating step (a) if the AT level is between 15-35%; (ii) if the AT level is >35%, administering to the patient subcutaneously fitusiran at a higher dose and at a selected dosing frequency, or at a higher dosing frequency at the starting dose; or (iii) if AT levels are <15%, discontinuing or pausing fitusiran treatment and, optionally, resuming subcutaneous administration of fitusiran to the patient at a lower dose and at the selected dosing frequency, or at the starting dose and at a lower dosing frequency. A process of performing one of the steps 13. A pharmaceutical composition comprising:

2. 1. A pharmaceutical composition comprising fitusiran for use in a method for reducing the risk of thrombosis in a patient receiving fitusiran for the prophylactic treatment of hemophilia A or B with or without an inhibitor, the method comprising: (a) administering a starting dose of fitusiran subcutaneously at a selected dosing frequency to a patient in need thereof; (b) obtaining a measurement of antithrombin (AT) levels in the patient; and (c) the steps of: (i) repeating step (a) if the AT level is between 15-35%; (ii) if the AT level is >35%, administering to the patient subcutaneously fitusiran at a higher dose and at a selected dosing frequency, or at a higher dosing frequency at the starting dose; or (iii) If AT levels are <15%, discontinue or halt Fitusiran treatment and, optionally, re-administer Fitusiran at a lower dose and at the selected dosing frequency. resuming subcutaneous administration at the same dose or at a lower dosing frequency at the starting dose. A process of performing one of the steps 13. A pharmaceutical composition comprising:

3. The pharmaceutical composition according to claim 1 or 2, wherein the initial dose of fitusiran is selected from 10 mg to 50 mg.

4. 4. The pharmaceutical composition of any one of claims 1 to 3, wherein the selected dosing frequency is every two months (Q2M) or every eight weeks (Q8W), and optionally the higher dosing frequency is every month (QM) or every four weeks (Q4W).

5. The pharmaceutical composition of claim 4, wherein the starting dose is 20 mg.

6. The starting dose is 50 mg, and optionally step (c)(ii) is performed if the two measurements of AT level are >35%, or 5. The method of claim 4, wherein step (c)(iii) is performed when two or more, optionally two, measurements of the AT level are <15%.

7. 7. The pharmaceutical composition of claim 6, wherein step (c)(ii) comprises administering 50 mg QM of fitusiran subcutaneously to the patient.

8. 8. The pharmaceutical composition of claim 7, wherein the method comprises administering 80 mg QM of fitusiran subcutaneously to the patient after step (c)(ii) if the AT level in the patient after step (c)(ii) is >35%, optionally by two measurements.

9. The method further comprises, after step (c)(iii), optionally after the patient's AT level has returned to ≧15%, optionally ≧22%, administering: (A) resuming administration of fitusiran 20 mg subcutaneously to the patient; (B) the patient's AT level after step (A) is: Optionally, if two or more measurements are <15%, discontinue Fitusiran treatment or If it is between 15 and 35%, repeat step (A); or The pharmaceutical composition of any one of claims 6 to 8, optionally comprising administering to the patient 20 mg QM of fitusiran subcutaneously if both measurements are >35%.

10. The method further comprises administering fitusiran subcutaneously to the patient at a dosage and dosing frequency sufficient to maintain AT levels in the patient at 15-35%, and optionally ... frequency sufficient to maintain AT levels in the patient at 15-35%, 10 mg QM or Q4W, 20 mg QM or Q4W, 20 mg Q2M or Q8W, 50 mg QM or Q4W, 50 mg Q2M or Q8W, or 80mg QM or Q4W The pharmaceutical composition according to any one of claims 1 to 9, comprising administering the composition subcutaneously at 100 mg / kg / day.

11. The pharmaceutical composition of any one of claims 1 to 10, wherein each AT level measurement is obtained after the patient has received at least two doses of fitusiran at a given dosage.

12. A pharmaceutical composition comprising fitusiran for use in a method for the prophylactic treatment of patients with hemophilia A or B with or without inhibitors, the method comprising the subcutaneous administration of 50 or 80 mg of fitusiran every two months or every eight weeks to a patient in need thereof.

13. A pharmaceutical composition comprising fitusiran for use in a method for the prophylactic treatment of patients with hemophilia A or B with or without inhibitors, the method comprising the step of subcutaneously administering 20 mg of fitusiran every month or every four weeks, or every two months or every eight weeks to a patient in need thereof.

14. A pharmaceutical composition comprising fitusiran for use in a method for the prophylactic treatment of patients with hemophilia A or B with or without inhibitors, the method comprising the step of subcutaneously administering 10 mg of fitusiran monthly or every four weeks to a patient in need thereof.

15. 15. The pharmaceutical composition of any one of claims 1 to 14, wherein the method comprises obtaining measurements of AT levels in the patient every 4 weeks, every 8 weeks, every month, every 2 months, every 4 months, every 6 months, or every 12 months.

16. The pharmaceutical composition according to any one of claims 1 to 15, wherein the patient is 12 years of age or older.

17. 17. The pharmaceutical composition of any one of claims 1 to 16, wherein fitusiran is provided in phosphate buffered saline (PBS) at 50-200 mg / mL, optionally 100 mg / mL, optionally the PBS having a pH of 7.

18. 18. The pharmaceutical composition of any one of claims 1 to 17, wherein the method comprises monitoring the patient's AT levels periodically after subcutaneous administration of fitusiran, optionally every 1, 2, 3, 4, 5, 6, 7, or 8 weeks, or every 1, 2, 3, 4, 5, or 6 months.

19. The pharmaceutical composition according to any one of claims 1 to 18, wherein obtaining a measurement of antithrombin (AT) levels in the patient comprises the use of a kinetic or chromogenic assay.

20. The pharmaceutical composition of claim 19, wherein the step of obtaining a measurement of antithrombin (AT) levels in the patient comprises the use of a chromogenic assay that quantifies functionally active AT in human citrated plasma based on the inhibition of excess factor Xa by AT.

21. 20. The pharmaceutical composition of claim 19, wherein the step of obtaining a measurement of antithrombin (AT) levels in the patient comprises the use of the INNOVANCE™ Antithrombin Assay.

22. A method for monitoring the treatment of a patient receiving fitusiran, the method comprising measuring antithrombin (AT) levels in the patient, the levels of AT being measured by a chromogenic assay that quantifies functionally active AT in human citrated plasma based on the inhibition of excess factor Xa by AT.

23. 23. The method of claim 22, wherein the level of AT is measured by the INNOVANCE™ Antithrombin Assay.

24. 24. An article of manufacture for use in the method of any one of claims 1 to 23, optionally a kit.

25. 25. A product for use according to claim 24, comprising a container containing one or more doses of fitusiran, each dose being 80 mg, 50 mg, 20 mg or 10 mg; In some cases, 80 mg of Fitusiran is in 0.8 mL of phosphate buffered saline (PBS), Fitusiran 50mg in 0.5mL PBS 20 mg of Fitusiran in 0.2 mL of PBS, or 10 mg of Fitziran was in 0.1 mL of PBS. Optionally, the PBS has a pH of 7.

26. 26. The product for use according to claim 25, wherein the container is a disposable, single-dose pre-filled syringe.

27. Use of fitusiran for the preparation of a medicament for the treatment of hemophilia A or B with or without inhibitors in a method according to any one of claims 1 to 23.

Images