HDAC6 protacs and their use in the treatment of cancer, neurodegenerative diseases, inflammation and metabolic disorders

Abstract

A compound of Formula (I), or a pharmaceutically acceptable salt, solvate, ester or prodrug thereof, for use in a method of prevention, treatment or amelioration of an HDAC6-mediated disease, wherein: A represents a cycloalkyl ring or a single bond and wherein A is optionally substituted; X1 and X2 each independently represent a group selected from O, S, NR2 and CR2R2, X3 represents N or CR2, Y represents (CR2R2)m, R1 represents an E3 ligase ligand; each R2 independently represents a group selected from 10 H and C1 to C12 hydrocarbon group that is optionally substituted; L represents a linker group; m represents an integer from 1 to 6; and n represents an integer from 0 to 3.

Description

[0001] 1

[0002] HDAC6 PROTACS Field of the Invention 5The present invention relates to compounds, and compositions thereof, that exhibit surprisinglyselective and high activity against HDAC6. The compounds find applications as medicaments, for example for use in the prevention, treatment or amelioration of HDAC6-mediated diseases. Background of the Invention 10 Histone deacetylases (HDACs) is a family of enzymes that modulate their substrates by removing the acetyl group from lysine residues. HDAC inhibitors (HDACis) have emerged as a powerfulclass of small-molecule therapeutics acting through the regulation of the acetylation states of histone proteins (a form of epigenetic modulation) and other non-histone protein targets. A15 number of structurally distinct HDACis have been approved including SAHA (SuberoylanilideHydroxamic Acid, a.k.a. vorinostat), romidepsin (FK228), belinostat, panobinostat, and Chidamide. Many HDACis have serious limitations, for example, lack of specificity, ineffectively low concentrations in solid tumours, and / or cardiac toxicity. 20 Histone deacetylase 6 (HDAC6) is primarily located in the cytoplasm and is responsible for deacetylating non-histone substrates such as α-tubulin, cortactin, and HSP90. The X-raystructure of the catalytic domains of the zebrafish ortholog of HDAC6 has been solved. HDAC6 possesses a unique structure with two catalytic domains (CD), each containing a catalytic zinc ion, and a zinc finger ubiquitin-binding domain. 25 The development of HDAC6 inhibitors has been proposed lead to new drugs with fewer adverse effects. HDAC6 inhibitors have been found to have applications in the treatment of cancer [Pulya, S., et al., Pharmacol. Res., 163, 105274 (2021)], neurodegenerative diseases / disorders [Rodrigues, D. A., et al., Med. Res. Rev., 40, 2177-2211 (2020)], [Yan et al., Front. Aging 30 Neurosci. 12:78], Alzheimer disease and tauopathies [Onishi, T., et al., Sci. Rep., 11, 15423 (2021)]; inflammation [Zhang et al., Biomedicine & Pharmacotherapy (2019) 117, 109166; Liu et al., Toxicology and Applied Pharmacology (2019), 370, 178-183; Sakloth et al., Psychopharmacology (2020), 237, pages 2139–2149; Horndahl et al., PLoS One. 2022; 17(10): e0266310], and metabolic disorders, such as obesity [Cakir, I., et al., Nat. Metab., 4, 44-59 35 (2022)]. 2

[0003] BAS-2 has been reported as a highly selective HDAC6 inhibitor. It was found that HDAC6inhibition reduced glycolytic metabolism in tumour cells [Dowling, C. M., et al., Sci. Adv., 7,eabc4897 (2021); WO 2022 / 129256 A1]. In HDAC inhibitory assays BAS-2 inhibited HDAC6(HDAC 1-9 assessed) with an IC50 of 760 nM. BAS-2 has the following structure: 5 The present invention has been devised with the foregoing in mind. Summary of the Invention 10 According to a first aspect of the invention there is provided a compound of Formula I, or a pharmaceutically acceptable salt, solvate, ester or prodrug thereof: Formula I, 15 wherein: Arepresents a cycloalkyl ring or a single bond and wherein A is optionally substituted;X1and X2each independently represent a group selected from O, S, NR2and CR2R2, X3 represents N or CR2,Y represents (CR2R2)m,20 R1represents an E3 ligase ligand; each R2independently represents a group selected from H and C1 to C12 hydrocarbon group that is optionally substituted; L represents a linker group; mrepresents an integer from 1 to 6; and 3 n represents an integer from 0 to 3. Compounds of Formula I have been found to exhibit surprisingly high activity against HDAC6. 5 The IC50values of compounds of Formula I have been found to be more than 15 times higher than BAS-2. Compounds of Formula I have also been found to be selective for HDAC6 degradation, compared to HDAC1 or HDAC 8 degradation. 10 Furthermore, global proteomic analysis has shown that, surprisingly, compounds of Formula I are selective for HDAC6 degradation compared to the vast majority of 6000+ proteins that were analysed. This provides further evidence that the BAS-2 scaffold, including PROTACs thereof,is highly selective at binding to HDAC6.15 The increased activity of compounds of Formula I and the increased selectivity of compounds of Formula I are likely to lead to significantly fewer side-effects compared to conventional HDAC6 inhibitors. 20 Compounds of Formula I successfully act as Proteolysis Targeting Chimeras (PROTACs). PROTACs hijack the natural ubiquitin-proteasome system (UPS) to degrade targeted proteins.PROTACs are heterobifunctional compounds designed through the combination of a ligand that can target a protein with a subunit that recruits an E3 ligase. 25 Ternary complex formation is essential for the mechanism of action of PROTACs, to enable the successful transfer of the ubiquitin chain from E2 to the exposed lysine residue of the target protein. Compounds of Formula I have been found to be dependent upon the ubiquitin- proteasome system, thereby successfully achieving this complex.30 It has surprisingly been found that compounds of the invention reduce glycolysis in carcinoma cell lines, whilst not reducing glycolysis in immune cells. Therefore, compounds of the invention provide the benefits of reducing metabolic activity in carcinoma cell lines without impairing immune cell function. 35 According to a second aspect the claimed invention provides a compound of Formula I, or a pharmaceutically acceptable salt, solvate, ester or prodrug thereof, for use as a medicament. 4

[0004] According to a third aspect the claimed invention provides a compound of Formula I, or a pharmaceutically acceptable salt, solvate, ester or prodrug thereof, for use in a method of prevention, treatment or amelioration of an HDAC6-mediated disease. 5 HDAC6-mediated diseases include cancer, neurodegenerative diseases / disorders, inflammation, and metabolic disorders (e.g. obesity). According to a fourth aspect the claimed invention provides a pharmaceutical composition comprising a compound of Formula I, or a pharmaceutically acceptable salt, solvate, ester or10 prodrug thereof and a pharmaceutically acceptable carrier. Preferably L comprises a 1,2,3-triazole group and / or a polyether (e.g. PEG) group.Preferably the E3 ligase ligand can be pomalidomide, such as: 15 . Detailed Description of the Invention The term “CX-CY” where X and Y are integers refers to the number of carbon atoms in a given 20 group. For example, a C1-C6 alkyl group contains from 1 to 6 carbon atoms, and a C3-C6 alkyl group contains from 3 to 6 carbon atoms. Alkyl groups are partially or fully saturated hydrocarbon groups, and may be linear, branched and / or cyclic (“cycloalkyl”). Alkyl groups may therefore include one or more alkenyl, alkynyl 25 and / or aryl groups. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl or hexyl and the like. The term “cycloalkyl” refers to cyclic hydrocarbon groups. Examples of such groups include cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl and the like. 5

[0005] Alkenyl groups are hydrocarbon groups that comprise one or more carbon-carbon double bond, and may be linear, cyclic and / or branched. Alkenyl groups may therefore include one or more alkyl, alkynyl and / or aryl groups. Examples of alkenyl groups include vinyl, allyl, prenyl, isoprenyl and the like. 5 Alkynyl groups are hydrocarbon groups that comprise one or more carbon-carbon triple bond, and may be linear, cyclic and / or branched. Alkynyl groups may therefore include one or more alkenyl, alkyl and / or aryl groups. 10 Aryl groups are hydrocarbon groups that include one or more aromatic rings. Aryl groups may therefore include one or more alkyl, alkenyl and / or alkynyl groups. Examples of aryl groups include carbocyclic aromatic groups such as phenyl, naphthyl, anthracenyl, pyrenyl, chrysenyl, benz[a]anthracenyl, fluoranthene, indenyl, and tetrahydronaphthyl groups. 15 Substituted hydrocarbon groups include one or more heteroatoms (e.g. N, O, S, P, and / or halide (e.g. F, Cl and / or Br)). Preferably substituted hydrocarbon groups include one or more heteroatoms selected from the list consisting of N, O and halide (e.g. F and Cl). Substituted hydrocarbon groups include heterocyclic (e.g. heteroaromatic / heteroaryl), heteroalkyl, heteroalkenyl, and / or heteroalkynyl groups. Substituted hydrocarbon groups may include 20 heteroatoms in the hydrocarbon chain (i.e. internal substituents, such as an ether) and / or attached to the hydrocarbon chain (i.e. external substituents, such as a halide). Examples of substituents include those selected from the list consisting of: amine (primary, secondary and / or tertiary amine), amide, alcohol, ester, ether, thiol, thioether, sulfoxide, sulfone, 25 sulfonamide, or halide (e.g. fluorine, chlorine, bromine and / or iodine), dialkyl peroxide, disulfide, sulfonate ester, thioketone, thioester, phosphine, phosphonate ester, phosphate ester, boronic ester, borinic ester, borane, aldehyde, ketone, carbamate, carbonate, carboxylic acid, carboxylic acid anhydride, urea, ketal, acetal, orthoester, orthocarbonate, nitrile, imine (e.g. an oxime and / or a Schiff base, such as a secondary ketamine and / or a secondary aldimine), imide, 30 diimide, hydrazine, 1,2,3-triazole, hydrazone, nitro, acylhydrazone, semicarbazone, carbazate hydrazone, and hydrazone carboximidamide. Preferred substituents include those selected from the list consisting of: amine, amide, alcohol, ester, ether, thioether, sulfone, sulfonamide, or halide (e.g. fluorine, chlorine and / or bromine), thioketone, phosphonate ester, phosphate ester, boronic ester, aldehyde, ketone, carbamate, carbonate, carboxylic acid, urea, ketal, acetal, nitrile, 35 imine, imide, 1,2,3-triazole and nitro. More preferred substituents include those selected from the list consisting of hydroxide, ethers (e.g. alkyl ethers, such as methoxyether), nitro, nitrile and halide (especially Cl). 6

[0006] Substituted hydrocarbon groups may contain from 1 to 10 heteroatoms, such as from 1 to 8, or from 1 to 6 heteroatoms. Substituted hydrocarbon groups may contain from 1 to 4 heteroatoms, such as 3, 2 or 1 heteroatoms. 5 Heterocyclic groups may be monocyclic or polycyclic (e.g. bicyclic) and / or may contain, 4 to 18 ring members, more usually 5 to 10 ring members, for example 5 or 6 ring members. A monocyclic group may include 3, 4, 5, 6, 7 or 8 ring members, more usually 4 to 7, and preferably5, 6 or 7, more preferably 5 or 6 ring members. Examples of polycyclic (e.g. bicyclic) groups 10 are those containing 6 to 18 ring members, more usually 8, 9 or 10 ring members. Heterocyclic groups may be selected from the list consisting of aziridine, azetidine, pyrrolidine, piperidine, piperazine, azepane, imidazolidine, tetrahydrofuran, oxirane, oxetane, oxane, oxepane, oxocane, 1,3-dioxolane, tetrahydrothiophene, pyrrolizidine, quinuclidine, 1-azaadamantane, 2- azaadamantane, 1-oxaspiro[4.5]decane, 1,4-dioxa-7-azaspiro[4.4.]nonane, 15 decahydroisoquinoline and decahydroquinoline. Heterocyclic groups include heteroaryl groups, such as polycyclic (e.g. bicyclic) ring systems wherein one or more rings are non-aromatic, provided that at least one ring is aromatic. Examples of such polycyclic systems include 1,4,5,6- tetrahydrocyclopenta[b]pyrrole, indoline, tetrahydroquinoline, tetrahydroisoquinoline, 1,2- dihydroquinoline, 1,2-dihydroisoquinoline, 2H-benzo[e][1,3]oxazine, 2H-benzo[b][1,4]-20 oxazine, 2H-benzo[e][1,2]oxazine, 1H-isochromene and 2H-chromene. Heteroaryl groups maybe five membered or six membered monocyclic ring or a bicyclic structure formed from fused five and six membered rings or two fused six membered rings. Heteroaryl groups may contain one or two or more ring nitrogen atoms. Examples of heteroaryl groups include pyrrole, furan, thiophene, imidazole, furazan, oxazole, oxadiazole, oxatriazole, isoxazole, thiazole, thiadiazole, 25 isothiazole, pyrazole, triazole, tetrazole, pyridine, pyrazine, pyridazine, pyrimidine, triazine, indole, 2H-isoindole, benzimidazole, 4-azaindole, 5-azaindole, 6-azaindole, 7-azaindole,benzofuran, isobenzofuran, benzo[c]thiophene, benzo[b]thiophene, benzo[d]isoxazole, benzo[d]thiazole, quinolone, isoquinoline, quinoxaline, phthalazine, quinazoline, cinnoline and 1,8-naphthyridine. 30 A Arepresents a cycloalkyl ring or a single bond. Each of these groups are optionally substituted.A includes the bond shown in the five-membered ring of Formula I, and attaches to an X1and an N group of Formula I. 35 7

[0007] A may represent a C5-C16 cycloalkyl group that contains a ring, for example a C5-C12, or C5-C10, or C5-C8, or C5-C6 cycloalkyl group. Preferably A represents a C6 cycloalkyl ring (cyclohexane). 5Preferably A represents a C5-C16 cycloalkyl group (e.g. a C5-C12, or C5-C10, or C5-C8, or C5-C6 cycloalkyl group) or a single bond that is optionally substituted. Preferably A includes two or fewer substituents, such as 1 or 0 substituents. More preferably A is unsubstituted. 10 Where A represents a hydrocarbon ring, the stereochemistry of the ring junction may be fused in the cis or trans position. Preferably the stereochemistry is trans as similar compounds haveshown enhanced binding to HDAC6 compared to the corresponding cis isomers: 15 cis isomer trans isomerWhere A represents a single bond, Formula I is represented by the following structure: 20 X1and X2X1and X2each independently represent a group selected from O, S, NR2and CR2R2. Preferably each of X1and X2independently represent a group selected from O, S and NR2. 25 X1preferably represents NR2. Preferably X1preferably represents NR2wherein R2is H or a C1- 6 hydrocarbon group, such as H or a C1-2 hydrocarbon group, most preferably H. 8

[0008] X2preferably represents O or S; most preferably S. X3X3represents N or CR2. 5 Preferably X3represents N. Y and m Y represents (CR2R2)m. m represents an integer from 1 to 6. 10 Each R2group for Y is independently selected from H and C1 to C12 hydrocarbon group that is optionally substituted. Preferably each R2group for Y is independently selected from H and a C1-C6 hydrocarbon group that is optionally substituted, such as H and a C1-C2 hydrocarbon group that is optionally substituted. Preferably the R2groups of Y are unsubstituted. Preferably 15 one or both (most preferably both) of the R2groups of Y represent H. Preferably m represents an integer from 1 to 4, such as from 1 to 3, or 1 or 2. Preferably m represents 1. 20 R1R1represents an E3 ligase ligand. Several E3 ligase ligands are known, and may be used in conjunction with the claimed invention. Bricelj A, et al., 2021, Front. Chem. 9:707317 describes E3 ligase ligands in PROTACS, 25 including syntheses and liner attachment points. Preferably the E3 ligase ligand is a cereblon (CRBN) ligand, such as a thalidomide-based ligand(e.g. comprising a thalidomide, pomalidomide and / or lenalidomide group). Preferably the E3 ligase ligand is thalidomide-based, for example comprising a pomalidomide, 4-30 hydroxythalidomide, alkyl thalidomide, or lenalidomide group.CRBN ligands typically comprise a glutarimide group. Thus, the E3 ligase ligand may comprise: The E3 ligase ligand may comprise a 2-aminoglutarimide group, for example: 9 R1may comprise a lenalidomide group, such as: 5 . Preferably R1 comprises a thalidomide group, such as: . 10 More preferably R1 represents a pomalidomide group, such as: Figure 3 of Han and Sun (MedComm. 2023;4:e290; doi: 10.1002 / mco2.290) identifies a series5 of CRBN ligands and proposed tethering points. R1 may represent a CRBN ligand identified asan E3 ligase ligand by Han and Sun (MedComm. 2023;4:e290; doi: 10.1002 / mco2.290 (e.g. Figure 3 thereof)), for example an E3 ligase ligand selected from the list consisting of: ,for example ,

[0009] 12 Table 1 of Han and Sun (MedComm. 2023;4:e290; doi: 10.1002 / mco2.290) describes the5 chemical structures of various PROTAC degraders that are CRBN ligands. These include thefollowing E3 ligase ligand moieties. Thus, the E3 ligase ligand may additionally or alternatively be selected wherein X represents halogen (especially F), wherein X represents halogen (especially F), , 14 5 . 15 Preferably the E3 ligase ligand is a von Hippel-Lindau (VHL) ligand, such as an oxazole-based(especially isoxazole-based) or thiazole-based ligand (e.g. comprising an oxazole (e.g. isoxazole) group and / or a thiazole group). 5The VHL ligand may comprise a thiazole group, for example a 4-methyl thiazole group: The VHL ligand may comprise an isoxazole group, for example a 3-methyl isoxazole group: . 10 Figure 2 of Han and Sun (MedComm. 2023;4:e290; doi: 10.1002 / mco2.290) identifies a series of VHL ligands and proposed tethering points. Table 1 of Han and Sun (MedComm.2023;4:e290; doi: 10.1002 / mco2.290) describes the chemical structures of various PROTAC degraders that are VHL ligands. These also include the following E3 ligase ligand moieties. R1may represent 15 a VHL ligand identified as an E3 ligase ligand by Han and Sun (MedComm. 2023;4:e290; doi: 10.1002 / mco2.290 (e.g. Figure 2 thereof)), for example an VHL ligand selected from the list consisting of:

[0010] 17 5 , for example 18 or Me, each R4independently represents -C(O)Me, , or5 ,and each R5 independently represents H or . Preferably R1 19 , wherein each R3independently represents H or Me. 5 R2Each R2independently represents a group selected from H and C1 to C12 hydrocarbon that is optionally substituted. Preferably each R2independently represents H or a C1-C8 hydrocarbon group that is optionally 10 substituted, for example H or a C1-C6 hydrocarbon group that is optionally substituted, preferably H or a C1-C4 hydrocarbon group that is optionally substituted, for example H or a C1, C2 or C3 hydrocarbon group that is optionally substituted. Preferably each R2is independently unsubstituted. 15 The hydrocarbon group of each R2may independently be an alkyl, alkenyl, aryl and / or alkynyl group that is optionally substituted. Preferably the hydrocarbon group of each R2is independently an alkyl and / or alkenyl group (e.g. a C1-6 alkyl and / or alkenyl group), most preferably an alkyl group, that is optionally substituted. More preferably the hydrocarbon group of each R2is independently an unsubstituted alkyl group, for example an unsubstituted C1-6 20 alkyl group. Most preferably each R2independently represents H. L L represents a linker group. 20 L may include 2 or more carbon atoms, preferably 3 or more, such as 4 or more carbon atoms, or 6 or more, such as 8 or more carbon atoms. L may include 30 or fewer carbon atoms, such as 24 or fewer, preferably 18 or fewer, or 14 or fewer, such as 12 or fewer, or 10 or fewer carbon atoms. L may be a C2-30 group that is optionally substituted, such as a C2-18, C2-14, or C4-10 5 group that is optionally substituted. Lmay be substituted by one or more groups selected from the list consisting of: amide, ester,amine, ether (e.g. polyether), thioether, peroxide, disulfide, sulfoxide, sulfone, sulfonamide,sulfonate ester, thioketone, thioester, phosphine, phosphonate ester, phosphate ester, boronic 10 ester, borinic ester, borane, ketone, carbamate, carbonate, carboxylic acid anhydride, urea, ketal, acetal, orthoester, orthocarbonate, imide, diimide, hydrazine, hydroxylamine, 1,2,3-triazole, alkyl (e.g. C1-C8, or C2-C6), alkenyl (e.g. C2-C8 or C3-C6), alkynyl (e.g. C2-C8 or C3-C6) andaryl (e.g. C5-C10 or C6-C8).15 Preferably L comprises or represents one or more groups selected from the list consisting of: amide, 1,2,3-triazole, ether (e.g. polyether), carboxyl, amine, aryl and alkyl. L may comprise or represent a group selected from the list consisting of aryl, ether, carboxyl and alkyl. Preferably L comprises the group represented by the formula20 , wherein o represents an integer from 1 to 16, more preferably wherein o represents an integer from 6 to 16, such as from 8 to 16, or from 1 to 14, such as from 1 to 12, or from 1 to 10, for example from 6 to 14, or from 8 to 10. Preferably L comprises a polyether group, such as a polyethylene glycol (PEG) group. Linkers 25 that include a polyether group (e.g. PEG group) have been found to have higher activity, perhaps because of their increased length and / or flexibility. Linkers including alkyl chains have alsobeen found to be effective. In one preferred embodiment, L comprises groups selected from the list consisting of: aryl (e.g. C5-C10, such as phenyl), amide, 1,2,3-triazole, and alkyl (e.g. C2-C8) and amine.30 21 L may be represented by the formula: wherein n represents an integer from 0 to 20, such as from 0 to 10, or from 0 to 8, preferably from 0 to 6, such as from 1 to 10, or from 1 to 6, such as from 1 to 5; and X4represents a group 5 selected from O, S, NR2and CR2R2. Preferably X4represents O, S, or NR2. More preferably X4represents O or NR2. In one preferred embodiment, L comprises groups selected from the list consisting of: aryl (e.g. C5-C10, such as phenyl), polyether (e.g. PEG) and amine. 10 The polyether group of L may be represented by the formula: wherein a represents an integer of 1 or more. a may represent an integer of from 1 to 20, such as from 1 to 14, or from 1 to 10, such as from 1 to 8, or from 1 to 6, such as from 1 to 5, or from 1 15 to 4. a may represent an integer of 2 or more, such as 3 or more, or 4 or more. a may represent an integer of from 2 to 20, such as from 2 to 14, or from 2 to 6. L may be represented by the formula: 20 wherein X4represents a group selected from O, S, NR2and CR2R2. Preferably X4represents O, S, or NR2. More preferably X4represents O or NR2. It is particularly preferred that the linker comprises a polyether (e.g. PEG) and / or alkyl chain. 25 n nrepresents an integer from 0 to 3. Preferably n is an integer from 0 to 2, such as 0 or 1. Morepreferably n is 1. 22 Preferred Embodiments In the compound of Formula (I), it may be that: ^A represents a C5-C16 cycloalkyl ring that contains a ring or a single bond that is optionally5 substituted; ^X1 and X2 each independently represent a group selected from O, S, NR2 and CR2R2,^ X3 represents N or CR2,^ Y represents (CR2R2)m where each R2independently represents a group selected from H and a C1-C6 hydrocarbon group,10 ^ R1 represents a cereblon or VHL ligand;^ each R2 independently represents a group selected from H and C1-C8 hydrocarbon group that isoptionally substituted; ^L represents a C2-30 linker group that is optionally substituted;^ m represents an integer from 1 to 6; and15 ^ n represents an integer from 0 to 3.In the compound of Formula (I), it may be that: ^A represents a C5-C16 cycloalkyl ring or a single bond that is optionally substituted;^ X1 and X2 each independently represent a group selected from O, S, NR2 and CR2R2,20 ^ X3 represents N or CR2,^ Y represents (CR2R2)m where each R2 independently represents a group selected from H and aC1-C6 hydrocarbon group, ^R1 represents an oxazole-based (especially isoxazole-based) or thiazole-based ligand, or athalidomide-based E3 ligase ligand;25 ^ each R2 independently represents a group selected from H and C1-C6 hydrocarbon group that isoptionally substituted; ^L represents a C2-18 linker group that is optionally substituted;^ m represents an integer from 1 to 6; and^ n represents an integer from 0 to 3.30 In the compound of Formula (I), it may be that: ^A represents a cycloalkyl group or a single bond that is optionally substituted with 2 or fewersubstituents; ^X1 and X2 each independently represent a group selected from O, S and NR2 where R2 representsH or a C1-6 hydrocarbon group;35 ^ X3 represents N or CR2, 23 ^Y represents (CR2R2)m where each R2 independently represents a group selected from H and aC1-C2 hydrocarbon group, ^R1 represents an E3 ligase ligand comprising a pomalidomide, 4-hydroxythalidomide, alkylthalidomide, or lenalidomide group; 5^ each R2 independently represents a group selected from H and a C1-C6 alkyl and / or alkenylgroup that is optionally substituted; ^L represents a C2-18 linker group that is substituted by one or more groups selected from the listconsisting of: amide, ester, amine, ether (e.g. polyether), thioether, peroxide, disulfide, sulfoxide, sulfone, sulfonamide, sulfonate ester, thioketone, thioester, phosphine, phosphonate ester,10 phosphate ester, boronic ester, borinic ester, borane, ketone, carbamate, carbonate, carboxylicacid anhydride, urea, ketal, acetal, orthoester, orthocarbonate, imide, diimide, hydrazine, hydroxylamine, 1,2,3-triazole, alkyl (e.g. C1-C8, or C2-C6), alkenyl (e.g. C2-C8 or C3-C6), alkynyl (e.g. C2-C8 or C3-C6) and aryl (e.g. C5-C10 or C6-C8); ^m represents an integer from 1 to 4; and15 ^ n represents an integer from 0 to 3.In the compound of Formula (I), it may be that: ^A represents a cycloalkyl group or a single bond that is optionally substituted with 2 or fewersubstituents; ^X1 and X2 each independently represent a group selected from O, S and NR2 where R2 represents20 H or a C1-6 hydrocarbon group; ^X3 represents N or CR2,^ Y represents (CR2R2)m where each R2 independently represents a group selected from H and aC1-C2 hydrocarbon group, ^R1 represents an E3 ligase ligand comprising an oxazole, isoxazole, thiazole, pomalidomide, 4-25 hydroxythalidomide, alkyl thalidomide, or lenalidomide group; ^each R2 independently represents a group selected from H and a C1-C6 alkyl and / or alkenylgroup that is optionally substituted;^ L represents a C2-18 linker group that is substituted by one or more groups selected from the listconsisting of: amide, ester, amine, ether (e.g. polyether), thioether, peroxide, disulfide, sulfoxide, 30 sulfone, sulfonamide, sulfonate ester, thioketone, thioester, phosphine, phosphonate ester, phosphate ester, boronic ester, borinic ester, borane, ketone, carbamate, carbonate, carboxylic acid anhydride, urea, ketal, acetal, orthoester, orthocarbonate, imide, diimide, hydrazine, hydroxylamine, 1,2,3-triazole, alkyl (e.g. C1-C8, or C2-C6), alkenyl (e.g. C2-C8 or C3-C6),alkynyl (e.g. C2-C8 or C3-C6) and aryl (e.g. C5-C10 or C6-C8);35 ^ m represents an integer from 1 to 4; and^ n represents an integer from 0 to 3.In the compound of Formula (I), it may be that: 24 ^A represents a C5-C16 cycloalkyl group or a single bond that is optionally substituted with 2 orfewer substituents; ^X1 and X2 each independently represent a group selected from O, S and NR2 where R2 representsH or a C1-C2 hydrocarbon group, 5^ X3 represents N or CR2,^ Y represents (CR2R2)m where each R2independently represents a group selected from H and a C1-C6 hydrocarbon group, ^R1 represents an E3 ligase ligand comprising a pomalidomide, 4-hydroxythalidomide, alkylthalidomide, or lenalidomide group;10 ^ each R2 independently represents a group selected from H and C1-4 alkyl and / or alkenyl group;^ L represents a C2-18 linker group and comprises or represents one or more groups selected fromthe list consisting of: amide, 1,2,3-triazole, ether (e.g. polyether), amine, aryl and alkyl; ^m represents an integer from 1 to 4; and^ n is from 0 to 2.15 In the compound of Formula (I), it may be that: ^A represents a C5-C16 cycloalkyl group or a single bond that is optionally substituted with 2 orfewer substituents; ^X1 and X2 each independently represent a group selected from O, S and NR2 where R2 representsH or a C1-C2 hydrocarbon group,20 ^ X3 represents N or CR2,^ Y represents (CR2R2)m where each R2 independently represents a group selected from H and aC1-C6 hydrocarbon group, ^R1 represents an E3 ligase ligand comprising an oxazole, isoxazole, thiazole, pomalidomide, 4-hydroxythalidomide, alkyl thalidomide, or lenalidomide group;25 ^ each R2 independently represents a group selected from H and C1-4 alkyl and / or alkenyl group;^ L represents a C2-18 linker group and comprises or represents one or more groups selected fromthe list consisting of: amide, 1,2,3-triazole, ether (e.g. polyether), amine, aryl and alkyl; ^m represents an integer from 1 to 4; and^ n is from 0 to 2.30 In the compound of Formula (I), it may be that: ^A represents a trans-fused C5-8 cycloalkyl group or a single bond;^ X1 represents NR2 where R2 represents H or a C1-6 hydrocarbon group^ X2 represents O or S,35 ^ X3 represents N,^ Y represents (CH2)m, 25 ^R1 comprises an oxazole, isoxazole or thiazole, or represents a lenalidomide or thalidomidegroup; ^each R2 independently represents a group selected from H and C1-2 alkyl and / or alkenyl group;^ L represents a C2-18 linker group and comprises or represents one or more groups selected from5 the list consisting of: amide, 1,2,3-triazole, ether (e.g. polyether), amine, aryl and alkyl; ^m represents an integer from 1 to 3; and^ n represents 0 or 1.In the compound of Formula (I), it may be that:10 ^ A represents a trans-fused C5-8 cycloalkyl group or a single bond;^ X1 represents NR2 where R2 represents H or a C1-6 hydrocarbon group^ X2 represents O or S,^ X3 represents N,^ Y represents (CH2)m,15 ^ R1 represents a lenalidomide or thalidomide group;^ each R2 independently represents a group selected from H and C1-2 alkyl and / or alkenyl group;^ L represents a C2-18 linker group and comprises or represents one or more groups selected fromthe list consisting of: amide, 1,2,3-triazole, ether (e.g. polyether), amine, aryl and alkyl; ^m represents an integer from 1 to 3; and20 ^ n represents 0 or 1.In the compound of Formula (I), it may be that: ^A represents a trans-fused C6 cycloalkyl group or a single bond;^ X1 represents NR2 where R2 represents H or a C1-2 hydrocarbon group25 ^ X2 represents S,^ X3 represents N,^ Y represents (CH2)m,^ R1 represents a group selected from: 26 ; ^each R2 independently represents H;5 ^ R3 represents H or Me;^ L represents a linker group represented by one of the following formulae: wherein n represents an integer from 0 to 20, and X4represents a group selected from O, S, NR2and CR2R2, or 10 wherein a represents an integer of 1 or more, or 27 , wherein o represents an integer of from 1 to 16; ^m represents an integer from 1 to 3; and^ n is 1.5 The compound of Formula (I) is preferably represented by the structure: wherein n is 1, 2, 3, 4 or 5 – corresponding to TTCP-01 to TTCP-05 respectively.The compound of Formula (I) is preferably represented by the structure: 10 wherein n is 1, 2, 3 or 4 – corresponding to TTCP-06, TTCP-08, TTCP-10 and TTCP-12respectively. 28 The compound of Formula (I) is preferably represented by the structure: wherein n is 1, 2, 3 or 4 – corresponding to TTCP-07, TTCP-09, TTCP-11 and TTCP-13respectively. The compound of Formula (I) is preferably represented by the structure of5 Compound 1, as shown below. Pharmaceutical Compositions Pharmaceutical compositions according to the invention may comprise a pharmaceutically 10 acceptable salt or other form thereof. Pharmaceutical compositions according to the invention may comprise one or more pharmaceutically acceptable excipients, such as carriers, diluents, fillers, disintegrants, lubricating agents, binders, colorants, pigments, stabilizers, preservatives, antioxidants, and / or solubility enhancers. Pharmaceutical compositions according to theinvention may comprise a pharmaceutically acceptable salt and optionally one or more 15 pharmaceutically acceptable excipients. The pharmaceutical compositions can be formulated by techniques known in the art. The pharmaceutical compositions can be formulated as dosage forms for oral, parenteral, such as topical, transdermal, intramuscular, intravenous, subcutaneous, intradermal, intraarterial, 20 intracardial, nasal, inhalation or aerosol administration (e.g. nasal or oral inhalation). The pharmaceutical composition may be formulated as a dosage form for oral administration. In the present context, the term “pharmaceutically acceptable salt” is intended to indicate saltswhich are not harmful to a patient. Such salts include pharmaceutically acceptable acid addition 25 salts, pharmaceutically acceptable metal salts, ammonium and alkylated ammonium salts. Acid addition salts include salts of inorganic acids as well as organic acids. Representative examples of suitable inorganic acids include hydrochloric, hydrobromic, hydroiodic, phosphoric, sulfuric, 29 nitric acids and the like. Representative examples of suitable organic acids include formic, acetic, trichloroacetic, trifluoroacetic, propionic, benzoic, cinnamic, citric, fumaric, glycolic, lactic, maleic, malic, malonic, mandelic, oxalic, picric, pyruvic, salicylic, succinic, methanesulfonic, ethanesulfonic, tartaric, ascorbic, pamoic, bismethylene salicylic, 5 ethanedisulfgionic, gluconic, citraconic, aspartic, stearic, palmitic, EDTA, glycolic, p- aminobenzoic, glutamic, benzenesulfonic, p-toluenesulfonic acids and the like. Further examples of pharmaceutically acceptable inorganic or organic acid addition salts include the pharmaceutically acceptable salts listed in J. Pharm. Sci. 1977, volume 66, issue 2. Examples of metal salts include lithium, sodium, potassium, magnesium salts and the like. Examples of 10 ammonium and alkylated ammonium salts include ammonium, methylammonium, dimethylammonium, trimethylammonium, ethylammonium, hydroxyethylammonium, diethylammonium, butylammonium, tetramethylammonium salts and the like. The pharmaceutical compositions according to the invention may be formulated with 15 pharmaceutically acceptable carriers or diluents as well as any other known adjuvants and excipients in accordance with conventional techniques such as those disclosed in Remington: The Science and Practice of Pharmacy, 19thEdition, Gennaro, Ed., Mack Publishing Co., Easton, PA, 1995. 20 Suitable pharmaceutical carriers include inert solid diluents or fillers, sterile aqueous solutions and various organic solvents. Examples of solid carriers are lactose, terra alba, sucrose, cyclodextrin, talc, gelatine, agar, pectin, acacia, magnesium stearate, stearic acid and lower alkyl ethers of cellulose. Examples of liquid carriers are syrup, peanut oil, olive oil, phospholipids, fatty acids, fatty acid amines, polyoxyethylene and water. In addition, the compounds of the 25 invention may form solvates with water or common organic solvents. Such solvates are also encompassed within the scope of the present invention. The pharmaceutical composition may be sterile. The composition may further comprise a buffer system, preservative(s), tonicity agent(s), 30 chelating agent(s), stabilizers and surfactants, which is well known to the skilled person. For convenience reference is made to Remington: The Science and Practice of Pharmacy, 20thedition, 2000. The composition may also further comprise one or more therapeutic agents active against the same disease state. 35 Methods to produce controlled release systems useful for compositions of the current invention include, but are not limited to, crystallization, condensation, co-crystallization, precipitation, co-precipitation, emulsification, dispersion, high pressure homogenisation, encapsulation, spray 30 drying, microencapsulating, coacervation, phase separation, solvent evaporation to produce microspheres, extrusion and supercritical fluid processes. General reference is made to Handbook of Pharmaceutical Controlled Release (Wise, D. L., ed. Marcel Dekker, New York, 2000) and Drug and the Pharmaceutical Sciences vol. 99: Protein Composition and Delivery 5 (MacNally, E.J., ed. Marcel Dekker, New York, 2000). It will be appreciated that the preferred route of administration may depend on factors such as the nature of the condition to be treated and the general condition and age of the subject to be treated. The polysaccharide of the invention may be administered by oral, rectal, nasal, 10 inhalation (e.g. nasal inhalation or oral inhalation), pulmonary, topical (including buccal and sublingual), transdermal, intracisternal, intraperitoneal, vaginal and parenteral (including subcutaneous, intramuscular, intrathecal, intravenous and intradermal) route. Preferably the polysaccharide is administered orally. 15 For topical use, sprays, creams, ointments, jellies, gels, inhalants, dermal patches, implants, solutions of suspensions, etc., containing the compounds of the present invention are contemplated. For the purpose of this application, topical applications shall include mouth washes and gargles. Compounds of the invention may be used in wafer technology, such as the biodegradable Gliadel polymer wafer, which is useful for brain cancer chemotherapy. 20 Pharmaceutical compositions for oral administration include solid dosage forms such as hard or soft capsules, tablets, troches, dragees, pills, lozenges, powders and granules and liquid dosage forms for oral administration include solutions, emulsions, aqueous or oily suspensions, syrups and elixirs, each containing a predetermined amount of the active ingredient, and which may25 include a suitable excipient. Compositions for oral use may be prepared according to any known method, and such compositions may contain one or more agents selected from the group consisting of sweetening agents, flavouring agents, colouring agents, and preserving agents in order to provide30 pharmaceutically elegant and palatable preparations. Tablets may contain the active ingredient in admixture with non-toxic pharmaceutically acceptable excipients which are suitable for the manufacture of tablets. These excipients may be for example, inert diluents, such as calcium carbonate, sodium carbonate, lactose, calcium 35 phosphate or sodium phosphate; granulating and disintegrating agents, for example corn starch or alginic acid; binding agents, for example, starch, gelatine or acacia; and lubricating agents, for example magnesium stearate, stearic acid or talc. 31 Tablets may be uncoated or they may be coated by known techniques to delay disintegration and absorption in the gastrointestinal tract and thereby provide a sustained action over a longer period. For example, a time delay material such as glyceryl monostearate or glyceryl distearate 5 may be employed. They may also be coated by the techniques described in U.S. Patent Nos. 4,356, 108; 4, 166,452; and 4,265,874 to form osmotic therapeutic tablets for controlled release. Formulations for oral use may also be presented as hard gelatine capsules where the active ingredient is mixed with an inert solid diluent, for example, calcium carbonate, calcium 10 phosphate or kaolin, or as soft gelatine capsules wherein the active ingredient is mixed with water or an oil, for example peanut oil, liquid paraffin, or olive oil. Aqueous suspensions may contain the active compounds in admixture with excipients suitable for the manufacture of aqueous suspensions. Such excipients are suspending agents, for example 15 sodium carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose, sodium alginate, polyvinylpyrrolidone, gum tragacanth and gum acacia; dispersing or wetting agents may be a naturally-occurring phosphatide such as lecithin, or condensation products of an alkylene oxide with fatty acids, for example polyoxyethylene stearate, or condensation products of ethylene oxide with long chain aliphatic alcohols, for example, heptadecaethyl-eneoxycetanol, 20 or condensation products of ethylene oxide with partial esters derived from fatty acids and a hexitol such as polyoxyethylene sorbitol monooleate, or condensation products of ethylene oxide with partial esters derived from fatty acids and hexitol anhydrides, for example polyethylene sorbitan monooleate. The aqueous suspensions may also contain one or more colouring agents, one or more flavouring agents, and one or more sweetening agents, such as sucrose or saccharin. 25 Oily suspensions may be formulated by suspending the active ingredient in a vegetable oil, for example arachis oil, olive oil, sesame oil or coconut oil, or in a mineral oil such as a liquid paraffin. The oily suspensions may contain a thickening agent, for example beeswax, hard paraffin or cetyl alcohol. Sweetening agents such as those set forth above, and flavouring agents 30 may be added to provide a palatable oral preparation. These compositions may be preserved by the addition of an antioxidant such as ascorbic acid. Dispersible powders and granules suitable for preparation of an aqueous suspension by the addition of water provide the active compound in admixture with a dispersing or wetting agent, 35 suspending agent and one or more preservatives. Suitable dispersing or wetting agents and suspending agents are exemplified by those already mentioned above. Additional excipients, for example, sweetening, flavouring, and colouring agents may also be present. 32 The pharmaceutical compositions of the present invention may also be in the form of oil-in- water emulsions. The oily phase may be a vegetable oil, for example, olive oil or arachis oil, or amineral oil, for example a liquid paraffin, or a mixture thereof. Suitable emulsifying agents5 may be naturally occurring gums, for example gum acacia or gum tragacanth, naturally occurring phosphatides, for example soy bean, lecithin, and esters or partial esters derived from fatty acids and hexitol anhydrides, for example sorbitan monooleate, and condensation products of said partial esters with ethylene oxide, for example polyoxyethylene sorbitan monooleate. The emulsions may also contain sweetening and flavouring agents. 10 Syrups and elixirs may be formulated with sweetening agents, for example glycerol, propylene glycol, sorbitol or sucrose. Such formulations may also contain a demulcent, a preservative, a flavouring agent and a colouring agent. The pharmaceutical composition may be in the form of a sterile injectable aqueous or oleaginous suspension. This suspension may be formulated 15 according to known methods using suitable dispersing or wetting agents and suspending agents described above. The sterile injectable preparation may also be a sterile injectable solution or suspension in a non-toxic parenterally acceptable diluent or solvent, for example as a solution in 1,3-butanediol. Among the acceptable vehicles and solvents that may be employed are water, Ringer’s solution, and isotonic sodium chloride solution. In addition, sterile, fixed oils are 20 conveniently employed as a solvent or suspending medium. For this purpose, any bland fixed oil may be employed using synthetic mono- or diglycerides. In addition, fatty acids such as oleicacid find use in the preparation of injectables. Parenteral administration may be performed by subcutaneous, intramuscular, intraperitoneal or 25 intravenous injection by means of a syringe, optionally a pen-like syringe. Alternatively, parenteral administration can be performed by means of an infusion pump. A further option is a composition which may be a solution or suspension for the administration of the prolactin receptor antagonist in the form of a nasal or pulmonal spray. As a still further option, the pharmaceutical compositions containing the compound of the invention can also be adapted to 30 transdermal administration, e.g. by needle-free injection or from a patch, optionally an iontophoretic patch, or transmucosal, e.g. buccal, administration. Pharmaceutical compositions for parenteral administration include sterile aqueous and non- aqueous injectable solutions, dispersions, suspensions or emulsions as well as sterile powders to35 be reconstituted in sterile injectable solutions or dispersions prior to use. 33 A medicament may be a composition (e.g. a pharmaceutical composition or an edible composition). A medicament may be a prescription drug, a non-prescription drug, an over the counter medicine, a dietary supplement, a dietary food, a clinical food, an edible product, atablet, a capsule, a pill, and food products such as beverages or any other suitable food product. 5 The medicament may be an injectable substance or an inhalable substance, such as a nasal spray. A pharmaceutical composition may include a compound of Formula (I) in an amount of 0.0001 wt% or more, such as 0.01 wt% or more. 10 It may be convenient or desirable to prepare, purify, and / or handle a corresponding pharmaceutically acceptable salt of the compound. Examples of pharmaceutically acceptable salts are discussed in Berge et al, 1977, "Pharmaceutically Acceptable Salts," J. Pharm. ScL Vol. 66, pp. 1-19. In one embodiment, the compound of Formula (I) is provided in the form of a saltof an organic or mineral acid. In a particular embodiment the compound of Formula I is provided15 in the form of a salt of a strong acid, such as HCl, HBr, HI or a sulfonic acid. Preferably thecompound of Formula I is provided as a HCl salt. If the compound is cationic, or has a functional group which may be cationic (e.g., -NH2 may be –NH3+), then a salt may be formed with a suitable anion. Examples of suitable inorganic anions 20 include, but are not limited to, those derived from the following inorganic acids: hydrochloric, hydrobromic, hydroiodic, sulfuric, sulphurous, nitric, nitrous, phosphoric, and phosphorous. Examples of suitable organic anions include, but are not limited to, those derived from the following organic acids: 2-acetyoxybenzoic, acetic, ascorbic, aspartic, benzoic, 25 camphorsulfonic, cinnamic, citric, edetic, ethanedisulfonic, ethanesulfonic, fumaric, glucheptonic, gluconic, glutamic, glycolic, hydroxymaleic, hydroxynaphthalene carboxylic, isethionic, lactic, lactobionic, lauric, maleic, malic, methanesulfonic, mucic, oleic, oxalic, palmitic, pamoic, pantothenic, phenylacetic, phenylsulfonic, propionic, pyruvic, salicylic,stearic, succinic, sulfanilic, tartaric, toluenesulphonic, and valeric. Examples of suitable 30 polymeric organic anions include, but are not limited to, those derived from the following polymeric acids: tannic acid, carboxymethyl cellulose. Alternatively, if the compound is anionic, or has a functional group which may be anionic, then a salt may be formed with a suitable cation. Examples of suitable inorganic cations include, but 35 are not limited to, alkali metal ions such as Na+and K+, alkaline earth cations such as Ca2+and Mg2+, and other cations such as Al3+. Examples of suitable organic cations include, but are not limited to, ammonium ion (i.e., NH4+) and substituted ammonium ions (e.g., NH3R+, NH2R2+, 34 NHR3+, NR4+). Examples of some suitable substituted ammonium ions are those derived from: ethylamine, diethylamine, dicyclohexylamine, triethylamine, butylamine, ethylenediamine, ethanolamine, diethanolamine, piperazine, benzylamine, phenylbenzylamine, choline, meglumine, and tromethamine, as well as amino acids, such as lysine and arginine. An example 5 of a common quaternary ammonium ion is N(CH3)4+. Unless otherwise specified, a reference to a particular compound also includes salt forms thereof. It may be convenient or desirable to prepare, purify, and / or handle a corresponding 10 pharmaceutically acceptable hydrate or solvate of the compound. The term "solvate" is used herein in the conventional sense to refer to a complex of solute (e.g., compound, salt of compound) and solvent. If the solvent is water, the solvate may beconveniently referred to as a hydrate, for example, a mono-hydrate, a di-hydrate or a tri-hydrate. 15 Unless otherwise specified, a reference to a particular compound also includes hydrate and solvate forms thereof. It may be convenient or desirable to prepare, purify, and / or handle the compound in a chemically 20 protected form. The term "chemically protected form" is used herein in the conventional chemical sense and pertains to a compound in which one or more reactive functional groups are protected from undesirable chemical reactions under specified conditions (e.g., pH, temperature, radiation, solvent, and the like). In practice, well known chemical methods are employed to reversibly render unreactive a functional group, which otherwise would be reactive, under 25 specified conditions. In a chemically protected form, one or more reactive functional groups are in the form of a protected or protecting group (also known as a masked or masking group, or a blocked or blocking group). By protecting a reactive functional group, reactions involving other unprotected reactive functional groups can be performed, without affecting the protected group; the protecting group may be removed, usually in a subsequent step, without substantially 30 affecting the remainder of the molecule. See, for example, Protective Groups in Organic Synthesis (T. Green and P. Wuts; 4thEdition; John Wiley and Sons, 2006). A wide variety of such "protecting," "blocking," or "masking" methods are widely used and well known in organic synthesis. For example, a compound which has two non-equivalent reactive 35 functional groups, both of which would be reactive under specified conditions, may be derivatized to render one of the functional groups "protected," and therefore unreactive, under the specified conditions; so protected, the compound may be used as a reactant which has 35 effectively only one reactive functional group. After the desired reaction (involving the other functional group) is complete, the protected group may be "deprotected" to return it to its original functionality. 5 A hydroxy group may be protected as an ether (-OR) or an ester (-OC(=O)R), for example, as a t-butyl ether; a benzyl, benzhydryl (diphenylmethyl), or trityl (triphenylmethyl) ether; a trimethylsilyl or t-butyldimethylsilyl ether; or an acetyl ester (-OC(=O)CH3, -OAc). An amine group may be protected, for example, as an amide (-NRCO-R) or a urethane (-NRCO-10 OR), for example, as a methyl amide (-NHCO-CH3); a benzyloxy amide (-NHCO-OCH2C6H5, - NH-Cbz); as a t-butoxy amide (-NHCO-OC(CH3)3, -NH-Boc); a 2-biphenyl-2-propoxy amide (- NHCO-OC(CH3)2C6H4C6H5, -NH-Bpoc), as a 9- fluorenylmethoxy amide (-NH-Fmoc), as a 6-nitroveratryloxy amide (-NH-Nvoc), as a 2-trimethylsilylethyloxy amide (-NH-Teoc), as a 2,2,2- trichloroethyloxy amide (-NH-Troc), as an allyloxy amide (-NH-Alloc), or as a 2(- 15 phenylsulfonyl)ethyloxy amide (-NH-Psec). A prodrug is a form of the compound that, after administration, is metabolized (i.e., converted within the body) into the active pharmaceutical. 20 Medical applications The compounds of the invention may be employed in the treatment of a disease or condition selected from the list consisting of: cancer, neurodegenerative diseases / disorders, inflammation, and metabolic disorders (e.g. obesity).25 Cancer is a generic term for a large group of diseases that can affect any part of the body. Other terms used are malignant tumours and neoplasms. One defining feature of cancer is the rapidcreation of abnormal cells that grow beyond their usual boundaries, and which can then invade adjoining parts of the body and spread to other organs, the latter process is referred to as 30 metastasizing. Metastases are a major cause of death from cancer. The cancer may be lung cancer, brain cancer, breast cancer, colorectal cancer, prostate cancer, skin cancer, stomach cancer or liver cancer. The cancer may be selected from the groupconsisting of: melanoma including ocular, uveal and skin melanoma, head and neck, renal, non-35 small cell lung cancer (NSCLC), microsatellite-instable carcinoma including lynch syndrome including gastroesophageal and colorectal, urothelial carcinoma including bladder, Merkel cellcarcinoma, Hodgkin lymphoma, gastric, oesophageal, non-Hodgkin lymphoma, small cell lung 36 cancer (SCLC), sarcoma, mesothelioma, glioblastoma, microsatellite stable including gastroesophageal and colorectal, pancreas, hepatocellular carcinoma (HCC), prostate, basal cell carcinoma, cutaneous T-cell lymphoma (CTCL), and squamous cell carcinoma. 5 The cancer may be breast cancer, including estrogen receptor (ER), progesterone receptor (PR) and Her-2 negative breast cancer. In particular, the cancer may be triple negative breast cancer (TNBC), such as metastatic triple negative breast cancer. The cancer may be a leukaemia, such as a lymphocytic leukaemia or a myelogenous leukaemia.10 The Leukaemia may be acute myeloid leukaemia (AML), acute lymphoblastic leukaemia (ALL), chronic myeloid leukaemia (CML), chronic lymphocytic leukaemia (CLL), hairy cell leukaemia(HCL), a myelodysplastic syndrome, or a myeloproliferative disorder. The cancer may be multiple myeloma, also known as myeloma, a type of bone marrow cancer. 15 Bone marrow is the spongy tissue at the centre of some bones that produces the body's blood cells. Multiple myeloma often affects several areas of the body, such as the spine, skull, pelvis and ribs. The cancer may be lung cancer: non-small-cell lung cancer or small-cell lung cancer. The cancer can be skin cancer, such as basal cell carcinoma (BCC), squamous cell carcinoma(SCC), melanoma and Merkel cell carcinoma (MCC). 20 In one embodiment the cancer may be selected from breast cancer (e.g. TNBC), multiple myeloma, and lung cancer (e.g. non-small cell lung cancer). It has been demonstrated that BAS- 2 has benefits in relation to these types of cancer. The cancer may be a solid tumour. 25 Use of the compound in the treatment of cancer may comprise use in combination with another cancer treatment such as chemotherapy, radiation therapy or immunotherapy. The chemotherapy may comprise paclitaxel or carboplatin. Use of the compound in the treatment of cancer may comprise use in combination with a metabolic inhibitor. 30 Use of the compound in the treatment of cancer may comprise identifying the need to regulate glycolytic metabolism. Neurodegenerative diseases are a heterogeneous group of disorders that are characterized by the progressive degeneration of the structure and function of the central nervous system or peripheral35 nervous system. Neurodegenerative diseases include Alzheimer's disease, Parkinson's disease,tauopathies (Pick disease, progressive supranuclear palsy, corticobasal degeneration, argyrophilic grain disease, globular glial tauopathies, primary age-related tauopathy (e.g. 37 neurofibrillary tangle dementia) chronic traumatic encephalopathy, and aging-related tau astrogliopathy), Huntington’s disease, amyotrophic lateral sclerosis (ALS) and epilepsy. In one embodiment the neurodegenerative disease is Alzheimer’s disease, a tauopathy, 5 Huntington’s disease, amyotrophic lateral sclerosis (ALS) or epilepsy. In particular, a compound of Formula (I) may be employed to treat ALS and / or epilepsy.The compound of Formula (I) may be used to modify the metabolism or function of immune cells. 10 Inflammation-related diseases and disorders include rheumatoid arthritis, neuroinflammation and airway inflammation (e.g. bronchitis, chronic obstructive pulmonary disease (COPD)). The disclosure of the present application comprises the subject-matter of the following clauses: 15 1.A compound of Formula I, or a pharmaceutically acceptable salt, solvate, ester or prodrug thereof, for use in a method of prevention, treatment or amelioration of an HDAC6-mediated disease: Formula I, wherein: A represents a cycloalkyl ring or a single bond and wherein A is optionally substituted; X1 and X2 each independently represent20 a group selected from O, S, NR2and CR2R2, X3represents N or CR2, Y represents (CR2R2)m, R1represents an E3 ligase ligand; each R2independently represents a group selected from H and C1 to C12 hydrocarbon group that is optionally substituted; L represents a linker group; m represents an integer from 1 to 6; and n represents an integer from 0 to 3. 2. The compound for use of clause 1, wherein R1represents a cereblon ligand. 25 3. The compound for use of clause 2, wherein R1comprises a pomalidomide, 4-hydroxythalidomide, alkyl thalidomide, or lenalidomide group. 4. The compound for use of clause 3, wherein R1represents: 38 . 5. The compound for use of any preceding clause, wherein A represents a C5-C16 cycloalkyl group or a single bond that is optionally substituted with 2 or fewer substituents. 6. The compound for use of any preceding clause, wherein L comprises a 1,2,3-triazole group 5 and / or a polyether group. 7. The compound for use of any preceding clause, wherein X1 represents NR2.8. The compound for use of any preceding clause, wherein X2represents S. 9. The compound for use of any preceding clause, wherein m represents an integer from 1 to 410. The compound for use of clause 9, wherein m represents 1.10 11. The compound for use of any preceding clause, wherein n is from 0 to 2. 12. The compound for use of clause 11, wherein n represents 1.13. The compound for use of clause 11, wherein A represents a C5-C16 cycloalkyl group or a single bond that is optionally substituted with 2 or fewer substituents; X1and X2each independently represent a group selected from O, S and NR2where R2represents H or a C1-C2 15 hydrocarbon group, X3represents N or CR2, Y represents (CR2R2)mwhere each R2independently represents a group selected from H and a C1-C6 hydrocarbon group, R1represents an E3 ligase ligand comprising a pomalidomide, 4-hydroxythalidomide, alkyl thalidomide, or lenalidomide group; each R2independently represents a group selected from H and C1-4 alkyl and / or alkenyl group; L represents a C2-18 linker group and comprises or represents one or more groups 20 selected from the list consisting of: amide, 1,2,3-triazole, ether (e.g. polyether), amine, aryl and alkyl; m represents an integer from 1 to 4; and n is from 0 to 2. 14. The compound for use of clause 13, wherein: A represents a trans-fused C6 cycloalkyl groupor a single bond; X1represents NR2where R2represents H or a C1-2 hydrocarbon group; X2represents S; X3represents N; Y represents (CH2)m; R1represents a group selected from: 39 represents a linker group represented by one of the following formulae: 5 represents a group selected from O, S, NR2and CR2R2, or , wherein a represents an integer of 1 or more; m represents an integer from 1 to 3; and n is 1.

[0011] 40 15. The compound for use of clause 14, wherein the compound is represented by one of the, wherein n is 1, 2, 3, 4 or 5. 5 16. The compound for use of any preceding clause, wherein the HDAC-6 mediated disease is selected from the list consisting of: cancer, neurodegenerative diseases / disorders, inflammation, and metabolic disorders. 17. The compound for use of clause 16, wherein the HDAC-6 mediated disease is selected fromthe list consisting of: skin cancer, lung cancer, breast cancer, Alzheimer's disease, Parkinson's10 disease, a tauopathy, Huntington’s disease, amyotrophic lateral sclerosis, epilepsy, rheumatoidarthritis, neuroinflammation, bronchitis, and chronic obstructive pulmonary disease. 18. A compound of Formula I, or a pharmaceutically acceptable salt, solvate, ester or prodrug thereof, for use as a medicament. 19. A compound of Formula I, or a pharmaceutically acceptable salt, solvate, ester or prodrug15 thereof. 20. A pharmaceutical composition comprising a compound of Formula I, or a pharmaceutically acceptable salt, solvate, ester or prodrug thereof and a pharmaceutically acceptable carrier. 41 Examples General Information 5 The synthesis of each compound was confirmed by1H NMR,13C NMR and mass spectrometry (MS).1H-NMR spectra were determined in deuterated dimethyl sulfoxide or deuterated chloroform using a Bruker AVANCE 400 at 400 MHz.13C-NMR spectra were resolved using the same spectrometers at 100 MHz and exploited the same solvents. All spectra were analysed using MestReNova software and the residual undeuterated solvent signals were used as internal 10 references. The progress of all of the reactions was monitored through thin-layer chromatography performed on 2.0 × 6.0-cm2 aluminium sheets precoated with silica gel 60 (HF-254, Merck) to athickness of 0.25 mm. The developed chromatograms were viewed under ultraviolet light (254−365 nm) and treated with iodine vapor. Flash column chromatography was carried out using silica gel, particle size 0.04-0.063 mm. The reagents and solvents were purchased from 15 commercial suppliers and used as received. Low resolution mass spectrometry (MS) experiments were performed on an Advion Expression Compact mass spectrometer, where 10 μL of the samples was injected into 300 μL of 80:10:10:1 (v / v) methanol / isopropyl alcohol / water / formic acid. The MS data were acquired in positive-ion mode and the spectra analysed using the AdvionMass Express software program. High resolution electrospray ionization (ESI) mass20 spectrometry (HRMS) was carried out in positive mode on a Bruker CompactTM massspectrometer. The samples were prepared using 1 mL of a mixture of acetonitrile and water (1:1). The spectra were analysed in Bruker Compass DataAnalysis 4.1. The high performance liquid chromatography was performed with a Shimazdu SIL-20AHT HPLC instrument equipped with a Shimazdu SPD-20AV prominence UV / Vis detector using Kromasil 100–5 C18 column (4.625 mm×250 mm). The mobile phase used was acetonitrile and ammonium acetate buffer (10 mM)(pH = 7.4) in a mixture 1:1. The isocratic HPLC mode was used, and the flow rate was 1.0 mL / min. The purity of the compounds was higher than 95 %. It was injected 50 µL of the sample that was prepared using a mixture of acetonitrile and water (1:1). 30 Synthesis The scheme below shows the synthesis of the PROTACs based on the structure of BAS-2 using the 1,2,3-triazole as linker. 42 General procedure for the synthesis of halides 1.0 g (3.6 mmol) of tert-butyl 4-(4-aminophenyl)piperazine-1-carboxylate and 995 mg (7.2 mmol) potassium carbonate were added in a mixture of THF (75 mL) and water (20 mL). The 5 mixture was stirred at 0 °C for 10 min. After that, a solution of 7.2 mmol of the acid chloride in 10 mL of THF was added in a dropwise manner. After the complete addition of the solution, the reaction stirred for more 30 minutes under 0 °C. The reaction was monitored by TLC. After thecompletion, the THF was concentrated under reduced pressure. Finally, 50 mL of cold water was added and it was observed the precipitation of a solid, which was collected by filtration. The10 solid was used in the next step without further purification. Synthesis of tert-butyl 4-(4-(2-chloroacetamido)phenyl)piperazine-1-carboxylate: 43 Synthesis of tert-butyl 4-(4-(3-chloropropanamido)phenyl)piperazine-1-carboxylate: Synthesis of tert-butyl 4-(4-(4-chlorobutanamido)phenyl)piperazine-1-carboxylate: 5 Synthesis of tert-butyl 4-(4-(5-bromopentanamido)phenyl)piperazine-1-carboxylate: 10 Synthesis of tert-butyl 4-(4-(6-bromohexanamido)phenyl)piperazine-1-carboxylate: General procedure for the synthesis of the azides 2.5 mmol of the respective halide was added in 5 mL of DMF. After that, 813 mg (12.5 mmol) 15 of sodium azide was added to the solution. The mixture stirred at 80 °C overnight. After that, the reaction was poured in 50 mL of cold water and it was observed the precipitation of a solid, which was collected by filtration. The solid was used in the next step without further purification. Synthesis of tert-butyl 4-(4-(2-azidoacetamido)phenyl)piperazine-1-carboxylate: 20 44 Synthesis of tert-butyl 4-(4-(3-azidopropanamido)phenyl)piperazine-1-carboxylate: 5 Synthesis of tert-butyl 4-(4-(4-azidobutanamido)phenyl)piperazine-1-carboxylate: Synthesis of tert-butyl 4-(4-(5-azidopentanamido)phenyl)piperazine-1-carboxylate: 10 Synthesis of tert-butyl 4-(4-(6-azidohexanamido)phenyl)piperazine-1-carboxylate: General procedure for the synthesis of the 1,2,3-triazole derivatives 15 First, 21 mg (0.0833 mmol) of copper sulfate pentahydrate was added to 3 mL of water and dissolved. Then, 0.833 mmol of the respective azide and 285 mg (0.9163 mmol) of 2-(2,6- dioxopiperidin-3-yl)-4-(prop-2-yn-1-ylamino)isoindoline-1,3-dione synthesised according tothe literature procedure in J. Med. Chem. 2019, 62, 15, 7042–7057) were added in 9 mL of THF and 9 mL of t-butanol. The solution was stirred at room temperature for 10 minutes. Finally, 50 20 mg (0.25 mmol) of sodium ascorbate was added to the solution with the copper sulfate pentahydrate and this suspension was added to the mixture containing the azide and alkyne. Themixture stirred for 18h at 50 °C. Then, the reaction was cooled and 50 mL of AcOEt was added and the mixture transferred to an extraction funnel. 50 mL of brine was added and extracted. The organic layer was washed with water, dried with sodium sulfate. The solvent was removed under 45 reduced pressure and the crude was purified using column chromatography. The crude was solubilised with dichloromethane and the eluent employed in the column was 2% of MeOH in DCM to remove remaining alkyne and finally, 4% of MeOH in DCM to recover the product. It was obtained yellow solid after the column. 5 Synthesis of tert-butyl 4-(4-(2-(4-(((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)amino)methyl)-1H-1,2,3-triazol-1-yl)acetamido)phenyl)piperazine-1-carboxylate: 10 Synthesis of tert-butyl 4-(4-(3-(4-(((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)amino)methyl)-1H-1,2,3-triazol-1-yl)propanamido)phenyl)piperazine-1-carboxylate: Synthesis of tert-butyl 4-(4-(4-(4-(((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4-15 yl)amino)methyl)-1H-1,2,3-triazol-1-yl)butanamido)phenyl)piperazine-1-carboxylate: 46 Synthesis of tert-butyl 4-(4-(5-(4-(((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)amino)methyl)-1H-1,2,3-triazol-1-yl)pentanamido)phenyl)piperazine-1-carboxylate: 5 Synthesis of tert-butyl 4-(4-(6-(4-(((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)amino)methyl)-1H-1,2,3-triazol-1-yl)hexanamido)phenyl)piperazine-1-carboxylate: General procedure for the synthesis of the PROTACs TTCP-01 to TTCP-05 10 0.41 mmol of the Boc-protected amine (1,2,3-triazole derivative) was solubilised with 15 mL of DCM. After that, 1 mL (4.1 mmol) of HCl in 1,4-dioxane was added to the solution. It was observed the precipitation of a yellow solid. The reaction stirred at room temperature overnight. The solvent was removed under reduced pressure and the crude was used in the next step withoutany further purification. The crude (HCl salt) was dissolved using 15 mL of water. Then, 0.142 15 g (1.025 mmol) of potassium carbonate was added. It was observed the precipitation of a yellow solid (free base). Then, 75 mL of THF was added in the mixture. The obtained solution was stirred under 0 °C for 10 minutes. After that, a solution of 50 µL (0.616 mmol) of chloroacetyl chloride was added in a dropwise manner. After the complete addition of the acid chloride, the reaction stirred under 0 °C for more 30 minutes. The reaction was monitored by TLC. Then, 10020 mL of AcOEt was added to the reaction and the organic layer was washed with brine (3x30 mL). The organic layer was dried with sodium sulfate and the solvent removed under reduced pressure. The crude was used in the next step without further purification. The crude was dissolved using 30 mL of acetonitrile and 0.32 g (2.05 mmol) of (±)-trans-octahydro-2H-benzo[d]imidazole-2- thione was added to the solution. The mixture was filtrated using 0.45 µm hydrophobic PTFE 47 syringe filters and stirred at room temperature over 72h. It was observed the precipitation of ayellow solid, which was collected by filtration and washed with acetonitrile. The PROTACs were obtained as HCl salts. 5 Synthesis of (±)-trans-2-((2-(4-(4-(2-(4-(((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)amino)methyl)-1H-1,2,3-triazol-1-yl)acetamido)phenyl)piperazin-1-yl)-2-oxoethyl)thio)- 3a,4,5,6,7,7a-hexahydro-1H-benzo[d]imidazol-3-ium chloride (TTCP-01) 10 Synthesis of (±)-trans-2-((2-(4-(4-(3-(4-(((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)amino)methyl)-1H-1,2,3-triazol-1-yl)propanamido)phenyl)piperazin-1-yl)-2-oxoethyl)thio)- 3a,4,5,6,7,7a-hexahydro-1H-benzo[d]imidazol-3-ium chloride (TTCP-02) 48 Synthesis of (±)-trans-2-((2-(4-(4-(4-(4-(((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)amino)methyl)-1H-1,2,3-triazol-1-yl)butanamido)phenyl)piperazin-1-yl)-2-oxoethyl)thio)- 3a,4,5,6,7,7a-hexahydro-1H-benzo[d]imidazol-3-ium chloride (TTCP-03) 5 Synthesis of (±)-trans-2-((2-(4-(4-(5-(4-(((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)amino)methyl)-1H-1,2,3-triazol-1-yl)pentanamido)phenyl)piperazin-1-yl)-2-oxoethyl)thio)- 3a,4,5,6,7,7a-hexahydro-1H-benzo[d]imidazol-3-ium chloride (TTCP-04) 10 49 Synthesis of (±)-trans-2-((2-(4-(4-(6-(4-(((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)amino)methyl)-1H-1,2,3-triazol-1-yl)hexanamido)phenyl)piperazin-1-yl)-2-oxoethyl)thio)- 3a,4,5,6,7,7a-hexahydro-1H-benzo[d]imidazol-3-ium chloride (TTCP-05) 5 Synthesis of PEG-based PROTACs The scheme below shows the synthesis of the PROTACs based on the structure of BAS-2 using the polyethylene glycol NH as linker.

[0012] 50 General procedure for the synthesis of the Boc-piperazine-PEG- Phthalimide5 1.2 g (4.31 mmol) of tert-butyl 4-(4-hydroxyphenyl)piperazine-1-carboxylate, 8.62 mmol of bis- PEG-OTs and 8.62 mmol of potassium carbonate were added in 200 mL of acetonitrile. The reaction stirred under 80 °C for 18h. The solvent was removed under reduced pressure and 100 mL of water was added. The mixture was extracted with dichloromethane. The organic layer was dried over with sodium sulfate and the solvent was removed under reduced pressure. The crude 10 was purified using column chromatography. The crude was solubilised with dichloromethane and the eluent employed in the column was 1% of MeOH in DCM. 51 Synthesis of tert-butyl 4-(4-(2-(2-(tosyloxy)ethoxy)ethoxy)phenyl)piperazine-1-carboxylate: Boc Boc Synthesis of tert-butyl 4-(4-(2-(2-(2-(tosyloxy)ethoxy)ethoxy)ethoxy)phenyl) piperazine-1-5 carboxylate: Boc Boc Synthesis of tert-butyl 4-(4-(2-(2-(2-(2-(tosyloxy)ethoxy)ethoxy)ethoxy)ethoxy) phenyl)piperazine-1-carboxylate: 10 Synthesis of tert-butyl 4-(4-((14-(tosyloxy)-3,6,9,12-tetraoxatetradecyl)oxy) phenyl)piperazine-1-carboxylate: Boc Boc 52 General procedure for the synthesis of the Boc-piperazine-PEG- Phthalimide2 mmol of Boc-piperazine-PEG-OTs and 0.74 g (4 mmol) of potassium phthalimide were added into 10 mL of DMF. The reaction stirred under 80 °C for 18h. The mixture was poured into 50 5 mL of water and extracted with AcOEt. After that, the organic layer was washed with brine and with NaHCO3. The organic layer was dried over with sodium sulfate and the solvent was removed under reduced pressure. The crude was used without further purification. Synthesis of tert-butyl 4-(4-(2-(2-(1,3-dioxoisoindolin-2-yl)ethoxy)ethoxy)phenyl) piperazine-10 1-carboxylate: Synthesis of tert-butyl 4-(4-(2-(2-(2-(1,3-dioxoisoindolin-2-yl)ethoxy)ethoxy)ethoxy) phenyl)piperazine-1-carboxylate: 15

[0013] 53 Synthesis of tert-butyl 4-(4-(2-(2-(2-(2-(1,3-dioxoisoindolin-2-yl)ethoxy)ethoxy) ethoxy)ethoxy)phenyl)piperazine-1-carboxylate: 5 Synthesis of tert-butyl 4-(4-((14-(1,3-dioxoisoindolin-2-yl)-3,6,9,12- tetraoxatetradecyl)oxy)phenyl)piperazine-1-carboxylate: General procedure for the synthesis of the Boc-piperazine-PEG-amine 10 1.21 mmol of Boc-piperazine-PEG-Phthalimide was added into 25 mL of ethanol. Then 0.65 mL of hydrazine hydrate was added. The mixture stirred under reflux for 18h. It was observed the precipitation of a white solid. The reaction was cooled using ice bath. The white solid was filtrated and the filtrated solution was concentrated under reduced pressure. The crude was suspended with a solution of NaOH 1M. Then, this solution was extracted with AcOEt. The 15 organic layer was dried over with sodium sulfate and the solvent was removed under reduced pressure. The crude was used without further purification. 54 Synthesis of tert-butyl 4-(4-(2-(2-aminoethoxy)ethoxy)phenyl)piperazine-1-carboxylate: 5 Boc Boc Synthesis of tert-butyl 4-(4-(2-(2-(2-(2-aminoethoxy)ethoxy)ethoxy)ethoxy)phenyl) piperazine-1-carboxylate: 10 55 Synthesis of tert-butyl 4-(4-((14-amino-3,6,9,12-tetraoxatetradecyl)oxy)phenyl) piperazine-1-carboxylate: Boc Boc 5 General procedure for the synthesis of the Boc piperazine functionalised with the 4- aminothalidomide 0.416 g (0.918 mmol) of Boc piperazine PEG amine and 0.276 g (1 mmol) of 2-(2,6- dioxopiperidin-3-yl)-4-fluoroisoindoline-1,3-dione or 0.290 g (1 mmol) of 4-fluoro-2-(1-methyl-2,6-dioxopiperidin-3-yl)isoindoline-1,3-dione were added in 5 mL of N,N-10 dimethylacetamide (DMA). Then, 0.317 mL of N,N-diisopropylethylamine (DIPEA) was added to the mixture. The reaction stirred under 90 °C for 18h. The mixture was poured into 50 mL of water and extracted with AcOEt. After that, the organic layer was washed with brine. The organic layer was dried over with sodium sulfate and the solvent was removed under reduced pressure. The crude was purified using column chromatography. The crude was solubilised with 15 dichloromethane and the the eluent employed in the column was 2% of MeOH in DCM. Synthesis of tert-butyl 4-(4-(2-(2-((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)amino)ethoxy)ethoxy)phenyl)piperazine-1-carboxylate: Boc 20 56 Synthesis of tert-butyl 4-(4-(2-(2-(2-((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)amino)ethoxy)ethoxy)ethoxy)phenyl)piperazine-1-carboxylate: Boc Boc 5 Synthesis of tert-butyl 4-(4-(2-(2-(2-(2-((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)amino)ethoxy)ethoxy)ethoxy)ethoxy)phenyl)piperazine-1-carboxylate: Synthesis of tert-butyl 4-(4-(2-(2-(2-(2-((2-(1-methyl-2,6-dioxopiperidin-3-yl)-1,3-10 dioxoisoindolin-4-yl)amino)ethoxy)ethoxy)ethoxy)ethoxy)phenyl)piperazine-1-carboxylate Boc Boc 57 Synthesis of tert-butyl 4-(4-((14-((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4-yl)amino)- 3,6,9,12-tetraoxatetradecyl)oxy)phenyl)piperazine-1-carboxylate: Boc 5 First general method for the synthesis of the PROTACs 0.56 mmol of the Boc-protected piperazine was solubilised with 50 mL of DCM. After that, 1.4 mL (5.6 mmol) of HCl in 1,4-dioxane was added to the solution. The reaction stirred at room temperature overnight. The solvent was removed under reduced pressure and the crude was used in the next step without any further purification. The crude (HCl salt) was dissolved using 15 10 mL of water. Then, 0.193 g (1.4 mmol) of potassium carbonate was added. It was observed the precipitation of a yellow solid (free base). Then, 75 mL of THF was added in the mixture. The obtained solution was stirred under 0 °C for 10 minutes. After that, a solution of 67 µL (0.84 mmol) of chloroacetyl chloride was added in a dropwise manner. After the complete addition of the acid chloride, the reaction stirred under 0 °C for more 30 minutes. The reaction was15 monitored by TLC. Then, 100 mL of AcOEt was added to the reaction and the organic layer waswashed with brine (3x30 mL). The organic layer was dried with sodium sulfate and the solvent removed under reduced pressure. The crude was used in the next step without further purification. The crude was dissolved using 5 mL of DMF and 0.218 g (1.4 mmol) of (±)-trans- octahydro-2H-benzo[d]imidazole-2-thione was added to the solution. The mixture stirred at 20 room temperature over 72h. After that, 10 mL of a 1M HCl solution was added. The solution was extracted with AcOEt. The aqueous phase was basified with potassium carbonate (pH 12) and extracted with DCM (5x20 mL). The solvent was removed under reduced pressure and the crude was purified using column chromatography. The crude was solubilised with dichloromethane and the eluent employed in the column was 6% of MeOH in DCM. It was25 obtained yellow solid after the suspend the residue with DCM and precipitate with diethyl ether. 58 Synthesis of (±)-trans-2-(2,6-dioxopiperidin-3-yl)-4-((2-(2-(4-(4-(2-((3a,4,5,6,7,7a-hexahydro- 1H-benzo[d]imidazol-2-yl)thio)acetyl)piperazin-1-yl)phenoxy)ethoxy)ethyl) amino)isoindoline-1,3-dione (TTCP-06) r.t., 7 17% 5 Synthesis of (±)-trans-2-(2,6-dioxopiperidin-3-yl)-4-((2-(2-(2-(4-(4-(2-((3a,4,5,6,7,7a- hexahydro-1H-benzo[d]imidazol-2-yl)thio)acetyl)piperazin-1- yl)phenoxy)ethoxy)ethoxy)ethyl)amino)isoindoline-1,3-dione (TTCP-08) r.t., 72 h 21% 10 59 Synthesis of (±)-trans-2-(2,6-dioxopiperidin-3-yl)-4-((2-(2-(2-(2-(4-(4-(2-((3a,4,5,6,7,7a- hexahydro-1H-benzo[d]imidazol-2-yl)thio)acetyl)piperazin-1- yl)phenoxy)ethoxy)ethoxy)ethoxy)ethyl)amino)isoindoline-1,3-dione (TTCP-10) 5 Synthesis of (±)-trans-2-(2,6-dioxopiperidin-3-yl)-4-((14-(4-(4-(2-((3a,4,5,6,7,7a-hexahydro- 1H-benzo[d]imidazol-2-yl)thio)acetyl)piperazin-1-yl)phenoxy)-3,6,9,12- r.t., 72 h 10 20%

[0014] 60 Synthesis of 4-((2-(2-(2-(2-(4-(4-(2-((1H-benzo[d]imidazol-2-yl)thio)acetyl)piperazin-1- yl)phenoxy)ethoxy)ethoxy)ethoxy)ethyl)amino)-2-(2,6-dioxopiperidin-3-yl)isoindoline-1,3- dione (TTCP-14, control). 52% 5 0.56 mmol of the Boc-protected piperazine was solubilised with 50 mL of DCM. After that, 1.4 mL (5.6 mmol) of HCl in 1,4-dioxane was added to the solution. The reaction stirred at room temperature overnight. The solvent was removed under reduced pressure and the crude was used in the next step without any further purification. The crude (HCl salt) was dissolved using 15 mL of water. Then, 0.193 g (1.4 mmol) of potassium carbonate was added. It was observed the 10 precipitation of a yellow solid (free base). Then, 75 mL of THF was added in the mixture. The obtained solution was stirred under 0 °C for 10 minutes. After that, a solution of 67 µL (0.84 mmol) of chloroacetyl chloride was added in a dropwise manner. After the complete addition of the acid chloride, the reaction stirred under 0 °C for more 30 minutes. The reaction was monitored by TLC. Then, 100 mL of AcOEt was added to the reaction and the organic layer was 15 washed with brine (3x30 mL). The organic layer was dried with sodium sulfate and the solvent removed under reduced pressure. The crude was used in the next step without further purification. The crude was dissolved using 5 mL of DMF and 0.21 g (1.4 mmol) of 1H- benzo[d]imidazole-2-thiol and 0.116 g (0.84 mmol) of potassium carbonate were added to the solution. The mixture stirred at room temperature over 72h. After that, 10 mL of a water was 20 added. The solution was extracted with DCM (5x20 mL). The solvent was removed under reduced pressure and the crude was purified using column chromatography. The crude was solubilised with dichloromethane and the eluent employed in the column was 4-6% of MeOH in DCM. It was obtained yellow solid after suspend the residue with DCM and precipitate with diethyl ether. 25 61 Synthesis of (±)-4-((2-(2-(2-(2-(4-(4-(2-(((trans)-3a,4,5,6,7,7a-hexahydro-1H-benzo[d]imidazol-2-yl)thio)acetyl)piperazin-1-yl)phenoxy)ethoxy)ethoxy)ethoxy)ethyl)amino)- 2-(1-methyl-2,6-dioxopiperidin-3-yl)isoindoline-1,3-dione (TTCP-15, control). r.t., 72 h 13% 5 The scheme below shows the synthesis of the PROTACs based on the structure of BAS-2 using the polyethylene glycol O as linker. 62 General procedure for the synthesis of the Boc-piperazine-PEG-O-Thalidomide 0.576 mmol of Boc-piperazine-PEG-OTs, 189.54 mg of 2-(2,6-dioxopiperidin-3-yl)-4- hydroxyisoindoline-1,3-dione (0.69 mmol) and 53 mg (0.633 mmol) of sodium bicarbonate were added into 5 mL of DMF. The reaction stirred under 60 °C for 18h. The mixture was poured into 550 mL of cold water. There was a precipitation of a white solid, which was collected by filtration.The crude was used without further purification. Synthesis of tert-butyl 4-(4-(2-(2-((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)oxy)ethoxy)ethoxy)phenyl)piperazine-1-carboxylate 10 Synthesis of tert-butyl 4-(4-(2-(2-(2-((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)oxy)ethoxy)ethoxy)ethoxy)phenyl)piperazine-1-carboxylate 15 Synthesis of tert-butyl 4-(4-(2-(2-(2-(2-((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4- yl)oxy)ethoxy)ethoxy)ethoxy)ethoxy)phenyl)piperazine-1-carboxylate 63 Synthesis of tert-butyl 4-(4-((14-((2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4-yl)oxy)- 3,6,9,12-tetraoxatetradecyl)oxy)phenyl)piperazine-1-carboxylate 5 Second general method for the synthesis of the PROTACs 0.32 mmol of the Boc-protected piperazine was solubilised with 50 mL of DCM. After that, 1.0 mL (4 mmol) of HCl in 1,4-dioxane was added to the solution. The reaction stirred at room temperature overnight. The solvent was removed under reduced pressure and the crude was used10 in the next step without any further purification. The crude (HCl salt) was dissolved using 15 mL of water. Then, 0.110 g (0.8 mmol) of potassium carbonate was added. It was observed the precipitation of a yellow solid (free base). Then, 75 mL of THF was added in the mixture. The obtained solution was stirred under 0 °C for 10 minutes. After that, a solution of 38 µL (0.48 mmol) of chloroacetyl chloride was added in a dropwise manner. After the complete addition of 15 the acid chloride, the reaction stirred under 0 °C for more 30 minutes. The reaction was monitored by TLC. Then, 100 mL of AcOEt was added to the reaction and the organic layer waswashed with brine (3x30 mL). The organic layer was dried with sodium sulfate and the solvent removed under reduced pressure. The crude was used in the next step without further purification. The crude was dissolved using 5 mL of DMF and 0.125 g (0.84 mmol) of (±)-trans- 20 octahydro-2H-benzo[d]imidazole-2-thione was added to the solution. The mixture stirred at room temperature over 72h. After that, 10 mL of a 1M HCl solution was added. The solution was extracted with AcOEt. The aqueous phase was basified with potassium carbonate (pH 12) and extracted with DCM (5x20 mL). The solvent was removed under reduced pressure and the crude was purified using column chromatography. The crude was solubilised with 25 dichloromethane and the eluent employed in the column was 6% of MeOH in DCM. It was obtained yellow solid after the suspend the residue with DCM and precipitate with diethyl ether 64 Synthesis of (±)-trans-2-(2,6-dioxopiperidin-3-yl)-4-(2-(2-(4-(4-(2-((3a,4,5,6,7,7a-hexahydro- 1H-benzo[d]imidazol-2-yl)thio)acetyl)piperazin-1-yl)phenoxy)ethoxy)ethoxy)isoindoline-1,3- r.t., 7 15% 5 Synthesis of (±)-trans-2-(2,6-dioxopiperidin-3-yl)-4-(2-(2-(2-(4-(4-(2-((3a,4,5,6,7,7a- hexahydro-1H-benzo[d]imidazol-2-yl)thio)acetyl)piperazin-1- yl)phenoxy)ethoxy)ethoxy)ethoxy)isoindoline-1,3-dione (TTCP-09) r.t., 72 h 10 18%

[0015] 65 Synthesis of (±)-trans-2-(2,6-dioxopiperidin-3-yl)-4-(2-(2-(2-(2-(4-(4-(2-((3a,4,5,6,7,7a- hexahydro-1H-benzo[d]imidazol-2-yl)thio)acetyl)piperazin-1- yl)phenoxy)ethoxy)ethoxy)ethoxy)ethoxy)isoindoline-1,3-dione (TTCP-11) r.t., 72 h 27% 5 Synthesis of (±)-trans-2-(2,6-dioxopiperidin-3-yl)-4-((14-(4-(4-(2-((3a,4,5,6,7,7a-hexahydro- 1H-benzo[d]imidazol-2-yl)thio)acetyl)piperazin-1-yl)phenoxy)-3,6,9,12- tetraoxatetradecyl)oxy)isoindoline-1,3-dione (TTCP-13) r.t., 72 h 18% 10 66 Synthesis of tert-butyl 4-(4-((10-methoxy-10-oxodecyl)oxy)phenyl)piperazine-1- carboxylate 500 mg of tert-butyl 4-(4-hydroxyphenyl)piperazine-1-carboxylate and 451.16 mg of 5 methyl 9-bromononanoate and 380 mg of sodium carbonate were added to 5 mL of DMF. The reaction was kept stirring under room temperature for 18h. The reaction mixture was poured in 50 mL of water and extracted with ethyl acetate. The organic layer was washed with brine and the solvent removed under reduced pressure. The crude was purified through column chromatography. It was obtained 540 mg of an oil (tert-butyl 4-(4-((10-10 methoxy-10-oxodecyl)oxy)phenyl)piperazine-1-carboxylate) (65% of yield). Synthesis of 10-(4-(4-(tert-butoxycarbonyl)piperazin-1-yl)phenoxy)decanoic acid 500 mg of tert-butyl 4-(4-((10-methoxy-10-oxodecyl)oxy)phenyl)piperazine-1- 15 carboxylate was added in a mixture of 10 mL of THF:MeOH:water (4:4:2). After that 40 mg of lithium hydroxide was added to the solution. The reaction was kept stirring under room temperature for 18h. The solvent removed under reduced pressure. The crude was purified through column chromatography. It was obtained 400mg of 10-(4-(4-(tert- butoxycarbonyl)piperazin-1-yl)phenoxy)decanoic acid (82% of yield). 67 Synthesis of tert-butyl 4-(4-((10-(((R)-1-((2S,4R)-4-hydroxy-2-(((S)-1-(4-(4- methylthiazol-5-yl)phenyl)ethyl)carbamoyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan- 2-yl)amino)-10-oxodecyl)oxy)phenyl)piperazine-1-carboxylate 5 0.439 g of (2S,4R)-1-((R)-2-amino-3,3-dimethylbutanoyl)-4-hydroxy-N-((S)-1-(4-(4- methylthiazol-5-yl)phenyl)ethyl)pyrrolidine-2-carboxamide, 0.443 g of 10-(4-(4-(tert- butoxycarbonyl)piperazin-1-yl)phenoxy)decanoic acid, 0.3 g of EDC.HCl and 0.3 mL of triethylamine were added in 10 mL of DMF. The reaction was kept stirring under room temperature for 18h. The reaction mixture was poured in 50 mL of water and extracted 10 with ethyl acetate. The organic layer was washed with brine and the solvent removed under reduced pressure. The crude was purified through column chromatography. It was obtained 540 mg of the title product, tert-butyl 4-(4-((10-(((R)-1-((2S,4R)-4-hydroxy-2- (((S)-1-(4-(4-methylthiazol-5-yl)phenyl)ethyl)carbamoyl)pyrrolidin-1-yl)-3,3-dimethyl- 1-oxobutan-2-yl)amino)-10-oxodecyl)oxy)phenyl)piperazine-1-carboxylate (45% of15 yield). Synthesis of (2S,4R)-1-((R)-2-(10-(4-(4-(2-(((3aR,7aR)-3a,4,5,6,7,7a-hexahydro-1H- benzo[d]imidazol-2-yl)thio)acetyl)piperazin-1-yl)phenoxy)decanamido)-3,3-

[0016] 68 dimethylbutanoyl)-4-hydroxy-N-((S)-1-(4-(4-methylthiazol-5- yl)phenyl)ethyl)pyrrolidine-2-carboxamide (Compound 1) 0.228 mmol of the Boc-protected piperazine was solubilised with 50 mL of DCM. After 5 that, 1 mL of HCl in 1,4-dioxane was added to the solution. The reaction stirred at room temperature overnight. The solvent was removed under reduced pressure and the crude was used in the next step without any further purification. The crude (HCl salt) was dissolved using 15 mL of water. Then, 0.95 g of potassium carbonate was added. It was observed the precipitation of a yellow solid (free base). Then, 75 mL of THF was added 10 in the mixture. The obtained solution was stirred under 0 °C for 10 minutes. After that, a solution of 37 µL (0.84 mmol) of chloroacetyl chloride was added in a dropwise manner. After the complete addition of the acid chloride, the reaction stirred under 0 °C for more 30 minutes. The reaction was monitored by TLC. Then, 100 mL of AcOEt was added tothe reaction and the organic layer was washed with brine (3x30 mL). The organic layer 15 was dried with sodium sulfate and the solvent removed under reduced pressure. The crude was used in the next step without further purification. The crude was dissolved using 5 mL of DMF and 0.3 g of 1H-benzo[d]imidazole-2-thiol and 0.116 g (0.84 mmol) of potassium carbonate were added to the solution. The mixture stirred at room temperature over 72h. After that, 10 mL of a water was added. The solution was extracted with DCM 20 (5x20 mL). The solvent was removed under reduced pressure and the crude was purified using column chromatography. The crude was solubilised with dichloromethane and the 69 eluent employed in the column was 4-6% of MeOH in DCM. It was obtained yellow solid after suspend the residue with DCM and precipitate with diethyl ether. It was obtained 95 mg of the title compound as a white solid (42% yield). 5 Biological Analysis HDAC6 inhibition - non-PROTAC HDAC6 InhibitorsThe inhibition of HDAC6 by the compounds listed in the table below, which are non-PROTAC10 versions of the compounds of the invention, was determined using a kinetic assay to measurefluorogenic peptide from p53 residues 379-382 (RHKK(Ac)AMC) substrate processing, as reported previously (J. E. Bradner et al., Nature chemical biology 6, 238 (2010)). The results ofthis investigation are reported in the table below. 70 71 The results showed that A groups that are alkyl rings or single bonds are well tolerated compared to A groups that are aromatic rings or double bonds. The amide functional group is important, and there is a good degree of tolerance to substitution from the amide group.5 HDAC6 inhibition - PROTAC HDAC6 InhibitorsTTCP-01 was tested against HDAC6, exhibiting an IC50 of 48 nM.Figure 2 of the accompanying drawings shows Western blot of the JJN3 cell lines treated with10 TTCP-01. Western blot analysis showed that the BAS-2-based PROTACs degraded HDAC6. Aconcentration of more than 10 µM, such as 30 µM, was required to observe any degree ofdegradation after twenty-four hours. Furthermore, levels of α-acetyl tubulin increased at 30 µM due to the inactivity of HDAC6. 15 It is believed that PROTAC-versions of these HDAC6 inhibitors will show a similar structure activity relationship. This shows that TTCP-01 was active against HDAC6. 20 Bortezomib (BTZ) is a proteosome inhibitor. Co-treatment with BTZ was used to examine whether the activity of a compound requires the proteasome system. As shown by Figure 2, BTZ reversed the degradation induced by TTCP-01, showing thedependence of the activity of TTCP-01 on the ubiquitin-proteasome system. 25 Ternary complex modelling was used to examine the conformation of TTCP-01 in the bindingsite of HDAC6 in a complex with cereblon (CRBN). It the only solutions contained the phenylring of the N-phenylpiperazine in axial position of the piperazine, a high-energy conformation.Thus, more flexible linkers could improve the efficiency of degradation. 30 Figure 3 of the accompanying drawings shows the results of Western blot analysis of JJN3 celllines treated with TTCP-10 at 10 µM. TTCP-10 induced a time-dependent degradation of HDAC6 at lower concentrations (10 µM) than35 TTCP-01, starting at 8 hr post treatment. 72 BTZ was found to reverse the degradation induced by TTCP-10, showing the dependence of the activity of TTCP-10 on the ubiquitin-proteasome system. Western blot analysis was performed to determine the inhibition of HDAC6, acetylated α- 5tubulin, HDAC1 and HDAC8 levels in JJN3 cells treated with TTCP-10 (with (+) or without 1nM BTZ), or pomalidomide, or (±)-trans-BAS-2 at 10 µM. Western blots shown arerepresentative of n=3 biological replicates. Figure 4 of the accompanying drawings shows a representative Western blot. Figure 5A of the10 accompanying drawings shows densitometry analysis performed for HDAC6 levels (normalised to beta-actin), where values represent relative units (RU). Figure 5B of the accompanyingdrawings shows densitometry analysis performed for acetyl tubulin levels (normalised to beta- actin), where values represent RU. 15 The levels of HDAC6 were about zero in the presence of TTCP-10, whereas there was only a modest reduction in the amount of HDAC6 in the presence of either pomalidomide or BAS-2. The levels of acetyl tubulin were increased by about six times in the presence of TTCP-10, whereas there was an insignificant change in the levels of acetyl tubulin in the presence of20 pomalidomide or BAS-2. The results show that TTCP-10 is significantly more active against HDAC6 than either pomalidomide or (±)-trans-BAS-2. This shows that the activity of TTCP-10 is more than simplydue to the combination of pomalidomide with (±)-trans-BAS-2. 25 The covalent linking of these two species provides a significant increase in effect compared to what would be expected for either of these compounds alone or for a mixture of these two compounds.30 The results show that TTCP-10 is selective for HDAC6 degradation compared to HDAC1 orHDAC 8 degradation. BTZ was again found to reverse the degradation induced by TTCP-10, showing the dependence of the activity of TTCP-10 on the ubiquitin-proteasome system. 35 73 These data show that TTCP-10 decreases the amount of HDAC6 protein, and thereby increases the amount of acetyl tubulin. The reduction in effect of TTCP-10 in the presence of BTZ shows that the mechanism of action is mediated through HDAC6 degradation, as expected. 5 Western blot analysis was performed to determine the inhibition of HDAC6, acetylated α- tubulin, HDAC1 and HDAC8 levels in JJN3 cells treated with (and without, control) Compound 1 at concentrations of 1, 10, 30 and 100 µM. Western blots shown are representative of n=3 biological replicates. Figure 6 of the accompanying drawings shows a representative Western blot. 10 The Western blot shows a significant dose-dependent decrease in the levels of HDAC6 with increasing concentration of Compound 1. Only a trace of HDAC6 was observed at 30 µM, and no HDAC6 was observed at 100 µM. This shows that Compound 1, which includes a VHL-type E3 ligase ligand, is also effective at degrading HDAC6 in a similar way to TTCP-10. 15 HDAC6 inhibition – comparative examplesTTCP-14 (below) has a benzimidazole functional group, whereby the A group is an aromatic ring. Therefore, TTCP-14 is not according to the invention. TTCP-14 was found to not be active against HDAC-6. 20 TTCP-14 TTCP-15 (below) includes a methyl group on the E3 ligase ligand, which blocks the normal25 activity of the E3 ligase ligand. Therefore, TTCP-15 is not according to the invention. TTCP-15 was found to not be active against HDAC-6. 74 TTCP-15 Treatment of cell lines - PROTAC HDAC6 Inhibitors5 JJN3 (human plasma cell leukaemia) cells were treated with concentrations of TTCP-10 of from about 0.1µM to about 15 µM. The cell viability of the cells was determined after 24 or 48 hoursof exposure. Figure 7 of the accompanying drawings shows the viability of JJN3 cells in the presence of10 different concentrations of TTCP-10 after 12 or 24 hours. Concentrations of TTCP-10 above about 1.5 µM degraded the cell viability of JJN3 cells, which was degraded down to about 5%after 48 hours at about 15 µM or 20% after 24 hours at about 15 µM. THP-1 (human leukaemia monocytic) cells lack the E3 ligase cereblon, which is a vital 15 component of the ubiquitin-proteasome system. Therefore, low activity against THP-1 may indicate that a compound operates through the ubiquitin-proteasome system. THP-1 cells were treated with concentrations of TTCP-10 of from about 0.1µM to about 60µM. The cell viability of the cells was determined after 24 or 48 hours of exposure.20 Figure 8 of the accompanying drawings shows the viability of THP-1 cells in the presence ofdifferent concentrations of TTCP-10 after 12 or 24 hours. Concentrations of TTCP-10 above about 10 µM degraded the cell viability of JJN3 cells, which was degraded down to about 40% after 24 or 48 hours at about 60 µM.25 The relatively low activity against THP-1 cells compared to JJN3 cells indicates that TTCP-10operates through the ubiquitin-proteasome system. 75 Cell glycolysis – PROTAC HDAC6 InhibitorsReduction of glycolysis has been associated with antiproliferative effects in carcinoma cell lines, and can be caused by inhibition of HDAC6 or knockdown (Dowling et al., Sci. Adv. 2021; 7 : eabc4897). 5 The effect of compound TTCP-10 on glycolysis in JJN3 multiple myeloma cell line was assessed. TTCP-10 was assessed at concentrations of 3µM and 10µM, and compared against DMSO(control). 10 Figure 9 of the accompanying drawings shows the results of this investigation. It can be seen that glycolysis was significantly reduced in the presence of TTCP-10 compared to the control. This indicates that compounds of the invention, such as TTCP-10, inhibit HDAC6 and reduce metabolism in JJN3 multiple myleoma cells. The level of glycolysis was lower at 10 µM than at3 µM, indicating a dose-dependent response.15 Figures 10A and 10B of the accompanying drawings shows the change in extracellular acidification rate (ECAR) for glycolysis and for glycolytic capacity respectively. It can be seen that there is a significant decrease in ECAR for both investigations. In each case, the ECAR for the samples of the invention was approximately half that of the control sample. This indicates 20 that compounds of the invention, such as TTCP-10, inhibit HDAC6 and reduce metabolism in JJN3 multiple myeloma cells. The level of glycolytic capacity was lower at 10 µM than at 3 µM,indicating a dose-dependent response. The effect of compound TTCP-10 on glycolysis in THP-1 (as a macrophage-like cell line) was 25 also assessed to determine whether TTCP-10 would reduce immune cell function by inhibiting glycolysis. No reduction in glycolysis was observed in the THP-1 cells, indicating that compounds of the invention such as TTCP-10 would not reduce immune cell function through the inhibition of glycolysis.30 The effect of pre-treatment of JJN3 cells with 1, 3, or 10 µM of HDAC6 inhibitor BAS-2 (orcontrol: DMSO) followed by treatment with M1-like macrophages (THP-1) was studied. Figure11A of the accompanying drawings shows a schematic representation of the study, illustrating the M1-like macrophages (THP-1), BAS-2 and CTV-JJN3 cells used. 35 Figure 11B of the accompanying drawings shows the results of the study, showing the fold change of phagocytosis ratio for each dosage tested. It was observed that the HDAC6 inhibitor caused increased engulfment of the JJN3 cells by the THP-1 cells, so leading to enhanced 76 immune engulfment. The response was dose-dependent, increasing significantly for the 3 µmand 10 µM doses. This shows that, despite the inhibition of HDAC6 in the JJN3 cells, pre-treatment by the HDAC6 5 inhibitor did not reduce the functional activity of the M1-like macrophage THP-1 cells. Owing to the similarities in activity between the HDAC6 inhibitors BAS-2 and TTCP-10, this shows that HDAC6 inhibitors of the invention are likely to provide an effective preventative treatment of HDAC6 mediated diseases.10 Global Proteomic Analysis To determine in an unbiased manner the effect of TTCP-10 on the proteome, global proteomics was assessed by data-independent acquisition using mass spectrometry (MS). 15 To determine the selective targets that were degraded, the JJN3 cells were treated with either DMSO, TTCP-10 30 µM, TTCP-10 30 µM and 1 nM Bortezomib, TTCP-15 (which includes a methyl group on the E3 ligase ligand, which blocks the normal activity of the E3 ligase ligand) 10 µM, TTCP-14 (which includes a benzimidazole functional group that blocks HDAC6 activity)10 µM, pompalidomide 10 µM, or BAS-2 10 µM alone for 16 hr, and global proteomics was20 assessed and compared. Figure 12a of the accompanying drawings shows a volcano plot of differentially abundantproteins based on LFQ intensities between DMSO and treatment with TTCP-10. The plots wereconstructed using t-test with an FDR of 0.01%. This shows that TTCP-10 induced degradation25 of a series of proteins including HDAC6 and IKZF3. Interestingly, the degradation of 9 proteins were selectively rescued by proteasome pre-treatment, including HDAC6. Differential expression analysis was performed on TTCP-10 versus DMSO and controlled for by TTCP-10 + bortezomib, TTCP-14, TTCP-15, BAS-2 and 30 pomalidomide, to identify potential off-target proteins of this scaffold. This analysis produced a list of proteins which are degraded either uniquely by TTCP-10 or as aconsequence of the degradation of HDAC6. The following list of 4 proteins were identified asbeing degraded uniquely by TTCP-10:35 - ILK, as shown by Figure 12b of the accompanying drawings,- SBF1, as shown by Figure 12c of the accompanying drawings,- HAUS5, as shown by Figure 12d of the accompanying drawings, and- HDAC6, as shown by Figure 12e of the accompanying drawings. 77 Surprisingly, TCCP-10 only degraded a very small minority of the 6000+ proteins that were analysed by MS. This provides further evidence that the BAS-2 scaffold, including PROTACsthereof, is highly selective at binding to HDAC6.5 Global proteomics of control compounds is not commonly utilized in the targeted protein degradation field; this data demonstrates its promising use for studying potential on and off-targets of the molecule core scaffold.

Claims

78 CLAIMS 1. A compound of Formula I, or a pharmaceutically acceptable salt, solvate, esteror prodrug thereof, for use in a method of prevention, treatment or amelioration of anFormula I, wherein: A represents a cycloalkyl ring or a single bond and wherein A is optionally substituted; X1and X2each independently represent a group selected from O, S, NR2and CR2R2, X3represents N or CR2, Y represents (CR2R2)m, R1represents an E3 ligase ligand; each R2independently represents a group selected from H and C1 to C12 hydrocarbon group that is optionally substituted; L represents a linker group; m represents an integer from 1 to 6; and n represents an integer from 0 to 3.

2. The compound for use of claim 1, wherein R1 represents a cereblon ligand or avon Hippel-Lindau ligand.79 3. The compound for use of claim 2, wherein R1 comprises a group selected fromthe list consisting of:, , .5 4. The compound for use of claim 2, wherein R1 comprises an oxazole, isoxazole,thiazole, pomalidomide, 4-hydroxythalidomide, alkyl thalidomide, or lenalidomide group.

5. The compound for use of claim 2, wherein R1 comprises a group selected from1083-each X independently represents halo,- each R3 independently represents H or Me,84 -each R4 independently represents -,and 5 ,.

7. The compound for use of any preceding claim, wherein A represents a C5-C1610 cycloalkyl group or a single bond that is optionally substituted with 2 or fewer substituents.85 8. The compound for use of any preceding claim, wherein L comprises a 1,2,3-triazole group and / or a polyether group.

9. The compound for use of any preceding claim, wherein X1 represents NR2.5 10. The compound for use of any preceding claim, wherein X2 represents S.

11. The compound for use of any preceding claim, wherein m represents an integerfrom 1 to 4 10 12. The compound for use of claim 11, wherein m represents 1.

13. The compound for use of any preceding claim, wherein n is from 0 to 2.15 14. The compound for use of claim 13, wherein n represents 1.

15. The compound for use of claim 13, wherein^ A represents a C5-C16 cycloalkyl group or a single bond that is optionally substitutedwith 2 or fewer substituents;20 ^ X1 and X2 each independently represent a group selected from O, S and NR2 where R2represents H or a C1-C2 hydrocarbon group, ^X3 represents N or CR2,^ Y represents (CR2R2)m where each R2 independently represents a group selected from Hand a C1-C6 hydrocarbon group,25 ^ R1 represents an E3 ligase ligand comprising a pomalidomide, 4-hydroxythalidomide,alkyl thalidomide, or lenalidomide group; ^each R2 independently represents a group selected from H and C1-4 alkyl and / oralkenyl group; ^L represents a C2-18 linker group and comprises or represents one or more groups30 selected from the list consisting of: amide, 1,2,3-triazole, ether (e.g. polyether), amine, aryl and alkyl; ^m represents an integer from 1 to 4; and^ n is from 0 to 2.86 16. The compound for use of claim 15, wherein:^ A represents a trans-fused C6 cycloalkyl group or a single bond;^ X1 represents NR2 where R2 represents H or a C1-2 hydrocarbon group;^ X2 represents S;5 ^ X3 represents N;^ Y represents (CH2)m;^ R1 represents a group selected from:10^each R2 independently represents H;^ R3 represents H or Me;^ L represents a linker group represented by one of the following formulae:87, wherein n represents an integer from 0 to 20, and X4represents a group selected from O, S, NR2and CR2R2,, wherein a represents an integer of 1 or more, or, wherein o represents an integer of from 1 to 16;^ m represents an integer from 1 to 3; and^ n is 1.88 17. The compound for use of claim 16, wherein the compound is represented by oneof the following structures:5 wherein n is 1, 2, 3, 4 or 5.

18. The compound for use of any preceding claim, wherein the HDAC-6 mediateddisease is selected from the list consisting of: cancer, neurodegenerative diseases / disorders, inflammation, and metabolic disorders. 1089 19. The compound for use of claim 16, wherein the HDAC-6 mediated disease isselected from the list consisting of: skin cancer, lung cancer, breast cancer, Alzheimer'sdisease, Parkinson's disease, a tauopathy, Huntington’s disease, amyotrophic lateralsclerosis, epilepsy, rheumatoid arthritis, neuroinflammation, bronchitis, and chronic 5 obstructive pulmonary disease.

20. A compound of Formula I, or a pharmaceutically acceptable salt, solvate, esteror prodrug thereof, for use as a medicament.10 21. A compound of Formula I, or a pharmaceutically acceptable salt, solvate, esteror prodrug thereof.

22. A pharmaceutical composition comprising a compound of Formula I, or apharmaceutically acceptable salt, solvate, ester or prodrug thereof and a15 pharmaceutically acceptable carrier.

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