SARS-COV-2 MPRO inhibitors and uses thereof

Abstract

This application relates to novel compounds and their use as SARS-CoV-2 Main Protease (Mpro) inhibitors. Compounds described herein may be useful in the treatment of SARS-CoV-2 and related viruses and disorders associated with SARS-CoV-2: Mpro. The application is also directed to pharmaceutical compositions comprising these compounds and the manufacture and use of these compounds and compositions in the treatment of SARS-CoV-2 and related viruses and disorders associated with SARS-CoV-2: Mpro. The compounds and compositions may be useful in preventing death or complications arising due to chronic underlying conditions or comorbidities in patients infected with SARS-CoV-2 and related viruses.

Description

[0001] SARS-COV-2 MPRO INHIBITORS AND USES THEREOF

[0002] FIELD OF THE INVENTION

[0003] This application relates to novel compounds and their use as SARS-CoV-2 Main Protease (Mpro) inhibitors. Compounds described herein may be useful in the treatment of SARS-CoV-2 and related viruses and disorders associated with SARS-CoV-2: Mpro. The application is also directed to pharmaceutical compositions comprising these compounds and the manufacture and use of these compounds and compositions in the treatment of SARS-CoV-2 and related viruses and disorders associated with SARS-CoV-2: Mpro. The compounds and compositions may be useful in preventing death or complications arising due to chronic underlying conditions or comorbidities in patients infected with SARS- CoV-2 and related viruses.

[0004] BACKGROUND

[0005] Coronaviruses have long existed in nature and have made zoonotic transmission to humans, generally causing mild respiratory illnesses such as the common cold upon infection. However, in the last two decades outbreaks of novel human coronavirus infections that cause severe respiratory illness have presented a major global health concern. This includes the severe acute respiratory syndrome coronavirus (SARS-CoV) outbreak in 2002-2004, the Middle East respiratory syndrome coronavirus (MERS-CoV) outbreak in 2012-2015 and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the most recently emerged strain of coronavirus, that was identified in Wuhan, China, in 2019 and is the aetiological agent responsible for the 2019-2020 viral pneumonia outbreak of coronavirus disease 2019 (COVID-19). Despite the tragic and widespread effects of these sudden occurrences and the periodic emergence of novel human coronaviruses increasing the potential for future outbreaks, we do not yet have validated antiviral treatments targeting coronavirus infections. SARS-CoV-2 packages a large RNA genome of ~30kb, two-thirds of which encodes for the two polyproteins pp1a and pp1b (Hegyi et al. Journal of General Virology 83 (3): 595-99). These polyproteins are processed into 16 non-structural proteins (nsps) that are liberated from the long polypeptide chains by two viral cysteine proteases, the papain-like protease (nsp3) and the 3C-like protease (nsp5). The latter species, also referred to as the main protease (Mpro), cleaves the viral polyproteins at eleven sites to generate twelve non-structural proteins (nsp5-16). Included in these nsps are those involved in the replication and transcription machinery such as the RNA-dependent RNA polymerase (nsp12) and helicase (nsp13). The essential role Mpro plays in viral replication has been demonstrated in mutagenesis experiments (Kim et al. Virology 208 (1): 1-8; Stobart et al. Journal of Virology 86 (9): 4801-10), which makes it an attractive target for the design of inhibitors to treat coronavirus infection. Furthermore, there are no human proteases with similar cleavage specificity and therefore selective inhibitors of Mpro are highly likely to be non-toxic (Anand et al. 2003. Science 300 (5626): 1763-67).

[0006] The use of protease inhibitors for the treatment of viral diseases is well precedented (Bacon et al. The New England Journal of Medicine 364 (13): 1207- 17) and the similarity of the SARS-CoV-2 Mpro active site to other viral proteases has driven efforts to identify clinically approved drugs that could be repurposed for the treatment of COVID-19 (Riva et al. Nature, 586: 113-119). Screening of a selection of 18 viral protease inhibitors designed for the treatment of human immunodeficiency virus (HIV) and Hepatitis C virus (HCV) identified the anti-HCV drug boceprevir and the pre-clinical inhibitor against feline infectious peritonitis virus (FIPV) GC376 as inhibitors of SARS-CoV-2 Mpro (Fu et al. Nature Communications 11 (1): 4417). While GC376 showed a more potent inhibition efficacy of recombinant protease activity (IC50 = 0.15 pM) than boceprevir (IC50 = 8 pM), GC376 has shown side effects in trials performed in cats raising potential safety concerns (Pedersen et al. Journal of Feline Medicine and Surgery 20 (4): 378-92). Boceprevir was also identified as an inhibitor of SARS-CoV-2 Mpro alongside telaprevir in a different study, albeit both drugs inhibited SARS-CoV-2 Mpro with IC50 values of >1 pM (Anson et al. 2020. doi:10.21203 / rs.3.rs- 26344 / v1). In addition to SARS-CoV-2 Mpro, the inhibitory efficacy of boceprevir and telaprevir was also assessed at Mpro proteases from eight other coronaviruses including SARS, MERS, HKU1 , HKU4, HKU5, NL63, FIPV and lBV. Within this selection boceprevirwas able to inhibit all coronavirus proteases tested except NL63 and a similarly broad spectrum of activity was shown for telaprevir with inhibitory activity shown at SARS, HKU4, HKU5, NL63 and IBV. While the antiviral activity of these drugs at SARS-CoV-2 Mpro is not sufficient for clinical development, their ability to inhibit a broad range of proteases highlights the potential for the design of broad-spectrum antiviral drugs able to treat not only SARS-CoV-2 infection but also other human coronaviruses and potentially novel coronaviruses that could emerge in the future.

[0007] The sequence similarly between SARS-CoV and SARS-CoV-2 Mpro active sites was also exploited in the identification of the SARS-CoV-2 Mpro inhibitor PF- 07304814, a phosphate prodrug of PF-00835231 which was originally designed for the treatment of SARS-CoV (Boras et al. BioRxiv, 2020.09.12.293498). PF-00835231 inhibited SARS-CoV-2 Mpro with a Ki of 0.27 nM and displayed broad inhibitory activity against ten further coronavirus strains with Ki values of 0.03-4 nM. This translated into ~1 pM activity in cell-based live virus assays. The activity of PF-00835231 in combination with remdesivir, a nucleoside RNA- dependent RNA polymerase inhibitor, was also evaluated as antiviral agents that target different aspects of the viral replication process can yield synergistic effects in combination. Indeed, PF-00835231 and remdesivir displayed either synergistic or additive effects in a cell-based antiviral assay, which suggests that the combination of Mpro inhibitors with antivirals with other modes of actions could show clinical benefit.

[0008] In 2020 the crystal structure of SARS-CoV-2 Mpro in complex with N3 (a Michael acceptor inhibitor) was published (Jin et al. Nature 582 (7811): 289-93), thereby enabling virtual screening and structure-based drug design (SBDD) for inhibitors of SARS-CoV-2 Mpro. Such SBDD efforts included the design of peptidomimetic a-ketoamides as broad-spectrum inhibitors of coronaviruses and enteroviruses with the two most promising inhibitors showing 0.71-12.27 pM IC50 values in recombinant inhibition assays for proteases from enteroviruses EV-A71 and CVB3 as well as coronaviruses SARS-CoV and NL63 (Zhang et al. 2020. Journal of Medicinal Chemistry 63 (9): 4562-4578). The activity observed in the recombinant protease assays broadly matched antiviral activity in cell-based live virus assays with IC50 values within 10-fold in both systems, suggesting that good activity in the protease inhibition assay is a good indicator of antiviral activity.

[0009] Currently, there are no targeted therapeutic agents for the treatment of COVID- 19, and effective treatment options remain very limited. Despite much ongoing research activity and numerous clinical trials in progress, only remdesivir and favipiravir have been approved in selected countries for limited use to treat SARS- CoV-2 infection but show only modest effects (Zhou et al. ACS Pharmacology & Translational Science 3 (5): 813-834). There exists a need for targeted therapeutic agents for the treatment of SARS-CoV-2 infection and for the reasons outlined above SARS-CoV-2 Mpro represents an attractive drug target for SARS-CoV-2. The compounds disclosed herein are shown to be inhibitors of SARS-CoV-2 Mpro and therefore represent potential candidates for the treatment of coronavirus infection and associated disorders including but not limited to COVID-19.

[0010] SUMMARY OF INVENTION

[0011] The present invention provides compounds having activity as SARS-CoV-2: Mpro inhibitors. Therefore, in a first aspect of the invention, the compounds are of Formula (I) or a salt, solvate, hydrate, N-oxide or prodrug thereof, wherein: R1and R1aare independently H, or a group selected from C1-6 alkyl, C3-6 cycloalkyl, and benzyl, each of which is optionally substituted with one or more halo, preferable fluoro; or

[0012] R1and R1aare linked, together with the nitrogen to which they are attached, to form a 3- to 6-membered saturated heterocyclyl comprising 1 or 2 heteroatoms and optionally substituted with one or more halo, preferably fluoro.

[0013] R2is selected from the group consisting of each of which is optionally substituted with one or more halo;

[0014] R3is selected from the group consisting of

[0015] (i) C1-6 alkyl or C3-6 cycloalkyl;

[0016] (ii) a 3- to 6-membered saturated heterocyclyl wherein the heteroatom is oxygen or nitrogen; and

[0017] (iii) -CH2phenyl; -CH(CH3)phenyl; or -C(CH3)2phenyl; any of groups (i) to (iii) being optionally substituted with one or more groups selected from halo, hydroxy and methoxy.

[0018] R4is selected from the group consisting of C1-8 alkyl, C2-8 alkenyl, and C3-8 cycloalkyl, each of which is optionally substituted with one or more groups selected from halo, hydroxy, and methoxy.

[0019] R5is selected from the group consisting of -CF3, -CH3, -CH2F, -CHF2, R6is H, or a group selected from C1-6 alkyl and C3-4 cycloalkyl, which groups are optionally substituted with one or more groups selected from halo, hydroxy and methoxy.

[0020] R7, R8and R9are independently selected from H and C1-3 alkyl optionally substituted with one or more halo.

[0021] In a second aspect of the invention, there is provided a pharmaceutical composition comprising a compound of the invention, including a salt, solvate, hydrate, N-oxide or prodrug thereof, and a pharmaceutically acceptable excipient.

[0022] In a third aspect of the invention, there is provided a compound of the invention, or a pharmaceutical composition comprising said compound, for use in the treatment of SARS-CoV-2 or in the treatment of disorders associated with SARS- CoV-2.

[0023] In a fourth aspect of the invention, there is provided a use of a compound of the invention in the manufacture of a medicament for the treatment of SARS-CoV-2 or a disorder associated with SARS-CoV-2.

[0024] In a fifth aspect of the invention, there is provided a method of treating a disease or disorder susceptible to SARS-CoV-2 Mpro inhibition in a subject, said method comprising administering a pharmaceutically effective amount of a compound of the invention, or salt, solvate, hydrate, N-oxide or prodrug thereof. A feature of this aspect is that the disease or disorder is SARS-CoV-2 or a disorder associated with SARS-CoV-2.

[0025] BRIEF DESCRIPTION OF THE FIGURES

[0026] Figure 1 shows mean plasma concentration-time profiles of the compound of Example 1 following IV dose of 1 mg / kg, and PO dose of 10 mg / kg with and without 20 mg / kg ritonavir to SD rats. DETAILED DESCRIPTION

[0027] The invention relates to the use of compounds as inhibitors of SARS-CoV-2: Mpro. The invention further relates to the use of novel compounds in the manufacture of medicaments for use as SARS-CoV-2: Mpro inhibitors. The invention further relates to compounds, compositions and medicaments that may be useful in the treatment of SARS-CoV-2 and related viruses or conditions or symptoms related thereto.

[0028] The compounds are of Formula (I): or a pharmaceutically acceptable salt, solvate, hydrate, N-oxide and / or prodrug thereof, wherein:

[0029] R1and R1aare independently H, or a group selected from C1-6 alkyl, C3-6 cycloalkyl, and benzyl, each of which is optionally substituted with one or more halo, preferable fluoro; or

[0030] R1and R1aare linked, together with the nitrogen to which they are attached, to form a 3- to 6-membered saturated heterocyclyl comprising 1 or 2 heteroatoms and optionally substituted with one or more halo, preferably fluoro.

[0031] R2is selected from the group consisting of each of which is optionally substituted with one or more halo.

[0032] R3is selected from the group consisting of

[0033] (i) C1-6 alkyl or C3-6 cycloalkyl;

[0034] (ii) a 3- to 6-membered saturated heterocyclyl wherein the heteroatom is oxygen or nitrogen; and

[0035] (iii) -CH2phenyl; -CH(CH3)phenyl; or -C(CH3)2phenyl; any of groups (i) to (iii) being optionally substituted with one or more groups selected from halo, hydroxy and methoxy.

[0036] R4is selected from the group consisting of C1-8 alkyl, C2-8 alkenyl, and C3-8 cycloalkyl, each of which is optionally substituted with one or more groups selected from halo, hydroxy, and methoxy.

[0037] R5is selected from the group consisting of -CF3, -CH3, -CH2F, -CHF2,

[0038] R6is H, or a group selected from C1-6 alkyl and C3-4 cycloalkyl, which groups are optionally substituted with one or more groups selected from halo, hydroxy, and methoxy.

[0039] R7, R8and R9are independently selected from H and Ci-3alkyl optionally substituted with one or more halo.

[0040] The compounds of Formula (I) according to the present invention may be compounds according to Formula (li) below: or a pharmaceutically acceptable salts, solvates, hydrates, N-oxides and / or prodrugs thereof, wherein the stereochemistry is as shown above, and the substituents are as defined elsewhere herein.

[0041] As used herein, the term “Ci-Xalkyl” refers to a saturated carbon chain having 1-x carbon atoms and the appropriate number of hydrogen atoms. It may be linear or branched. For instance, the term “C1-6 alkyl” refers to a group consisting of 1 , 2, 3, 4, 5, or 6 carbon atoms and the appropriate number of hydrogen atoms. All subgroups thereof are contemplated, for instance C1-6, C1-5, C1-4, C1-3, C1-2, Ci , C2- 6, C2-5, C2-4, C2-3, C2, C3-6, C3-5, C3-4, C3, C4-5, C4, C5-6, C5, and Ce alkyl groups. Examples of alkyl groups include methyl, ethyl, propyl (including isopropyl), butyl (including n-butyl, sec-butyl isobutyl and tert-butyl) and pentyl.

[0042] As used herein, the term “C3-X cycloalkyl” refers to a saturated alkyl group having 3-x carbon atoms and the appropriate number of hydrogen atoms, said group comprising a cyclic alkyl ring portion. Such a cycloalkyl group may be bonded directly via a ring carbon, or else via a straight or branched alkylene chain, e.g. methylene or ethylene. Such a cycloalkyl group may be substituted with one or more alkyl side chains. For instance, the term “C3-6 cycloalkyl” refers to a group having 3, 4, 5, or 6 carbons, said group comprising at least one cycloalkyl portion, e.g. cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl. All subgroups thereof are contemplated, such as C3-6, C3-5, C3-4, C3, C4-6, C4-5, C4, C5-6, C5, Ce cycloalkyl. Examples of “C3-6 cycloalkyl” include cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl as well as the following:

[0043] “C3-6 cycloalkyl” may preferably be selected from cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.

[0044] As used herein, the term “halo” denotes a halogen atom, and is preferably, F, Cl, Br or I, more preferably F or Cl unless otherwise stated.

[0045] The terms “optional” or “optionally” denotes that the subsequently described event or circumstance may, but need not, occur, and that the description includes instances where the event or circumstance occurs and instances in which it does not.

[0046] The term “substituted” denotes that the group to which it refers has one or more hydrogen atoms substituted for a different group. For instance, a “substituted” alkyl group refers to a monovalent radical of an alkane group as defined above with one or more hydrogens attached to the hydrocarbon being replaced with another group.

[0047] In view of the above, the term “optionally substituted” means that the group to which it refers may or may not be substituted, for instance with one or more halo.

[0048] Where a moiety is substituted with “one or more” groups, this means that at least one, up to and including all, of the available hydrogen atoms on the moiety may be substituted with said groups. Where a moiety is optionally substituted with one or more groups, it may be substituted with one to six groups, preferably one to three groups (insofar as this is possible based on the number of available hydrogen atoms). For instance, where a moiety is said to be substituted with one or more groups, it may be substituted with one, two, or three of said groups, e.g. mono substituted.

[0049] As used herein, a “heteroatom” is N, O or S, preferably N, or O.

[0050] Unless otherwise specified, the term “3- to x- membered saturated heterocyclyl” (e.g. 3- to 6- membered saturated heterocyclyl) is similar to “Cs-x cycloalkyl”, except that one or more of the carbon atoms in the ring have been substituted for a heteroatom, e.g. N or O. For parts of the range “3- to 6- membered saturated heterocyclyl” all subgroups thereof are contemplated, such as 3-6, 3-5, 3-4, 3, 4- 6, 4-5, 4, 5-6, 5, and 6 membered heterocyclyl. Examples of heterocyclic rings include aziridine, azetidine, pyrrolidine, piperidine, tetrahydrofuran, tetrahydrothiophene, piperazine, tetrahydropyran, thiane, and morpholine.

[0051] In the compounds described herein, R1and R1aare independently H or a group selected from C1-6 alkyl, C3-6 cycloalkyl, and benzyl, each of which is optionally substituted with one or more halo, preferable fluoro.

[0052] Alternatively, R1and R1amay be linked, together with the nitrogen to which they are attached, to form a 3- to 6-membered saturated heterocyclyl comprising 1 or

[0053] 2 heteroatoms and optionally substituted with one or more halo, preferably fluoro. This means that R1and R1aare part of a saturated heterocyclic ring that contains

[0054] 3 to 6 ring atoms, i.e. 3, 4, 5 or 6 ring atoms. Non-limiting examples of such a heterocycle group include the mono-radical of the following groups. When R1and R1aare linked, it is preferred that they form an aziridine or azetidine, more preferably aziridine, which groups may optionally be substituted with one or more halo, preferably F.

[0055] It is preferable that:

[0056] (i) R1is H or a group selected from C1-4 alkyl, C3-5 cycloalkyl or benzyl each of which is optionally substituted with one or more halo, preferably fluoro; or

[0057] (ii) R1and R1aare linked, together with the nitrogen to which they are attached, to form an aziridinyl or azetidinyl ring optionally substituted with one or more halo, preferably F.

[0058] In further preferred embodiments, R1is selected from H, or a group selected from methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, sec-butyl, isobutyl, tert-butyl, cylclobutyl, and benzyl, which groups are each optionally substituted with one or more fluoro.

[0059] More preferably, R1is H or a group selected from methyl, ethyl, propyl, isopropyl, cyclopropyl, tert-butyl, cylclobutyl, , which groups are each optionally substituted with one or more fluoro.

[0060] Yet more preferably, R1is cyclopropyl optionally substituted with one or more fluoro.

[0061] R1ais preferably H or methyl, more preferably H. Most preferably R1is cyclopropyl, and R1ais H

[0062] R2is selected from the group consisting each of which is optionally substituted with one or more halo.

[0063] R9is selected from H and C1-3 alkyl optionally substituted with one or more halo, preferably fluoro.

[0064] Preferably R9is H or methyl optionally substituted with one or more fluoro.

[0065] Most preferably R9is H or methyl.

[0066] The term “3- 6-membered heterocyclyl” is similar to the term “3- 6-membered saturated heterocyclyl” above, except that the ring may be saturated or unsaturated. For instance the ring may contain one or more double bonds.

[0067] The term “oxo” is =0. optionally substituted with one or more halo, preferably wherein the halo is fluoro.

[0068] However, it is most preferable that R2is In this regard, R2may be In some preferred embodiments,

[0069] R3is selected from the group consisting of

[0070] (i) C1-6 alkyl or C3-6 cycloalkyl;

[0071] (ii) a 3- to 6-membered saturated heterocyclyl wherein the heteroatom is oxygen or nitrogen; and

[0072] (iii) -CH2phenyl; -CH(CH3)phenyl; or -C(CH3)2phenyl; any of groups (i) to (iii) being optionally substituted with one or more groups selected from halo, hydroxy and methoxy.

[0073] Preferred groups for R3include methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, sec-butyl, iso-butyl, and the following groups: each of which may be optionally substituted with one or more halo, preferably fluoro.

[0074] More preferred groups for R3are each of which are optionally substituted with one or more halo, preferably fluoro. Even more preferably R3is selected from the group consisting of each of which is optionally substituted with one or more fluoro, for instance one to three fluoro.

[0075] Still more preferably R3is cyclopropyl, iso-propyl, sec-butyl or tert-butyl, optionally substituted with one or more fluoro.

[0076] For instance, R3may be iso-propyl, sec-butyl or tert-butyl

[0077] Most preferably, R3is tert-butyl.

[0078] R4is selected from the group consisting of C1-8 alkyl, C2-8 alkenyl, and C3-8 cycloalkyl, each of which is optionally substituted with one or more groups selected from halo, hydroxy, and methoxy.

[0079] The term C2-X alkenyl, as used herein, is similar to the definition of Ci-Xalkyl above, except that the group contains at least one carbon-carbon double bond.

[0080] In preferred embodiments R4is -CH2-X, wherein X is C1-5 alkyl, C3-5 cycloalkyl, or C3-5 alkenyl, which groups may be optionally substituted with one or more groups selected from halo, hydroxy, and methoxy.

[0081] Preferably, X is selected from methyl, ethyl, propyl, iso-propyl, cyclopropyl, tertbutyl, sec-butyl, iso-butyl and cyclobutyl, which groups may be optionally substituted with one or more halo, preferably fluoro.

[0082] The group R4may be, for instance, one or more groups selected from halo, hydroxy, and methoxy. Preferably said groups are unsubstituted or substituted with one or more fluoro.

[0083] More preferably R4is selected from each of which groups may be optionally substituted with one or more fluoro.

[0084] Yet more preferably, R4is selected from which groups are optionally substituted with one or more fluoro.

[0085] Most preferably

[0086] R5is selected from the group consisting of -CF3, -CH3, -CH2F, -CHF2, preferable that R5is methyl or substituted methyl, e.g. -CF3, -CH3, -CH2F, or -CHF2. Most preferably R5is -CF3.

[0087] R6is H, or a group selected from C1-6 alkyl and C3-4 cycloalkyl, which groups are optionally substituted with one or more groups selected from halo, hydroxy and methoxy.

[0088] In preferred embodiments, R6is selected from H or Ci-3alkyl group, optionally substituted with one or more halo, preferably fluoro.

[0089] More preferably, R6is H, or R6is methyl or ethyl which are optionally substituted with one or more fluoro.

[0090] Most preferably R6is selected from H or methyl. R7and R8are independently selected from H, and C1-3 alkyl optionally substituted with one or more halo, preferably fluoro.

[0091] In preferred embodiments R7and R8are independently selected from H and methyl which may be optionally substituted with one or more fluoro. Most preferably R7and R8are each H.

[0092] R9is selected from H, and C1-3 alkyl optionally substituted with one or more halo, preferably fluoro.

[0093] R9may be H or methyl.

[0094] Thus, in a preferred embodiment, the compound of the present invention may be a compound according to Formula (IA) or a salt, solvate, hydrate, N-oxide or prodrug thereof, wherein R1, R1a, R2, R3, R4, R5and R6are each independently defined according to any of the definitions for R1, R1a, R2, R3, R4, R5and R6provided herein above.

[0095] In a preferred embodiment, the compound of the present invention may be a compound of Formula (I), (li), or (IA) wherein:

[0096] R1is H or a group selected from methyl, ethyl, propyl, isopropyl, cyclopropyl, tert- butyl, cylclobutyl, which groups are each optionally substituted with one or more fluoro, more preferably R1is cyclopropyl;

[0097] R1ais H or methyl, preferably H;

[0098] R2is selected from the group consisting of each of which is optionally substituted with one or more halo. optionally substituted with one or more halo, preferably wherein the halo is fluoro.

[0099] However, it is most preferable that R2is In this regard, R2may be

[0100] In some preferred embodiments,

[0101] R3is selected from the following groups each of which is optionally substituted with one or more fluoro, more preferably R3is tert-butyl;

[0102] R4is selected from the following groups ted with one or more halo, preferably fluoro, more preferably,

[0103] R5is selected from the group consisting of -CF3, -CH3, -CH2F, -CHF2, preferable that R5is methyl or substituted methyl, e.g. -CF3, -CH3, -CH2F, or -CHF2. Most preferably R5is -CF3.

[0104] R6is selected from H or Ci-3alkyl optionally substituted with one or more halo, preferably fluoro, more preferably R6is H or methyl; and

[0105] R7and R8are independently selected from H and methyl; preferably H.

[0106] Preferred compounds of the invention are selected from

[0107] (2S)-A / -(4-(cyclopropylamino)-3,4-dioxo-1-((S)-2-oxopyrrolidin-3-yl)butan-2- yl)-4,4-dimethyl-2-((S)-A / ,3,3-trimethyl-2-(2,2,2- trifluoroacetamido)butanamido)pentanamide; and • (2S)-A / -(4-(cyclopropylamino)-3,4-dioxo-1-((S)-2-oxopyrrolidin-3-yl)butan-2- yl)-2-((S)-3,3-dimethyl-2-(2,2,2-trifluoroacetamido)butanamido)-4,4- dimethylpentanamide or salt, solvate, hydrate, N-oxide or prodrug thereof.

[0108] The invention will now be illustrated, but not limited, by reference to the following examples shown in Table 1 .

[0109] Table 1 - Non-limiting compounds of the invention In this disclosure, where a discrepancy exists between a compound name and a compound structure, the compound structure will prevail.

[0110] The compounds of the invention may be used as such or, where appropriate, as salts, in particular pharmacologically acceptable salts (acid or base addition salts), thereof. The pharmacologically acceptable addition salts mentioned below are meant to comprise the therapeutically active non-toxic acid and base addition salt forms that the compounds are able to form. Compounds that have basic properties can be converted to their pharmaceutically acceptable acid addition salts by treating the base form with an appropriate acid. Exemplary acids include inorganic acids, such as hydrogen chloride, hydrogen bromide, hydrogen iodide, sulphuric acid, phosphoric acid; and organic acids such as formic acid, acetic acid, propanoic acid, hydroxyacetic acid, lactic acid, pyruvic acid, glycolic acid, maleic acid, malonic acid, oxalic acid, benzenesulphonic acid, toluenesulphonic acid, methanesulphonic acid, trifluoroacetic acid, fumaric acid, succinic acid, malic acid, tartaric acid, citric acid, salicylic acid, p-aminosalicylic acid, pamoic acid, benzoic acid, ascorbic acid and the like. Exemplary base addition salt forms are the sodium, potassium, calcium salts, and salts with pharmaceutically acceptable amines such as, for example, ammonia, alkylamines, benzathine, and amino acids, such as, e.g. arginine and lysine. The term addition salt as used herein also comprises solvates which the compounds and salts thereof are able to form, such as, for example, hydrates, alcoholates and the like.

[0111] Throughout the present disclosure, a given chemical formula or name shall also encompass all (pharmaceutically acceptable) salts, solvates, hydrates, N-oxides, and / or prodrug forms thereof. It is to be understood that the compounds of the invention include any and all hydrates and / or solvates of the compound formulae. It is appreciated that certain functional groups, such as the hydroxy, amino, and like groups form complexes and / or coordination compounds with water and / or various solvents, in the various physical forms of the compounds. Accordingly, the above formulas are to be understood to include and represent those various hydrates and / or solvates.

[0112] Compounds of the invention also include tautomeric forms. Tautomeric forms result from the swapping of a single bond with an adjacent double bond together with the concomitant migration of a proton. Tautomeric forms include prototropic tautomers which are isomeric protonation states having the same empirical formula and total charge. Example prototropic tautomers include ketone - enol pairs, amide - imidic acid pairs, lactam - lactim pairs, enamine - imine pairs, and annular forms where a proton can occupy two or more positions of a heterocyclic system, for example, 1 H- and 3H-imidazole, 1 H, 2H- and 4H- 1 ,2,4-triazole, 1 Eland 2H- isoindole, and 1 H- and 2H-pyrazole. Tautomeric forms can be in equilibrium or sterically locked into one form by appropriate substitution. The compounds described herein can be asymmetric (e.g. having one or more stereocenters). All stereoisomers, such as enantiomers and diastereoisomers, are intended unless otherwise indicated. The terms “diastereoisomer” and “diastereomer” are used herein interchangeably. Compounds of the present invention that contain asymmetrically substituted carbon atoms can be isolated in optically active or racemic forms. Methods on how to prepare optically active forms from optically active starting materials are known in the art, such as by resolution of racemic mixtures or by stereoselective synthesis. Many geometric isomers of olefins, C=N double bonds, and the like can also be present in the compounds described herein, and all such stable isomers are contemplated in the present invention. Cis- and trans-geometric isomers of the compounds of the present invention are described and may be isolated as a mixture of isomers or as separated isomeric forms.

[0113] In the case of the compounds which contain an asymmetric carbon atom, the invention relates to the D form, the L form, and D,L mixtures and also, where more than one asymmetric carbon atom is present, to the diastereoisomeric forms. Those compounds of the invention which contain asymmetric carbon atoms, and which as a rule accrue as racemates, can be separated into the optically active isomers in a known manner, for example using an optically active acid. However, it is also possible to use an optically active starting substance from the outset, with a corresponding optically active or diastereoisomeric compound then being obtained as the end product.

[0114] The compounds of the invention may comprise isotopic form of the atoms therein, e.g. they may be isotopically-labelled and / or isotopically-enriched forms of the compounds. The compounds of the invention herein may contain unnatural proportions of atomic isotopes at one or more of the atoms that constitute such compounds. Examples of isotopes that can be incorporated into the disclosed compounds include isotopes of hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur, chlorine, such as2H,3H,11C,13C,14C,13N,15O,170,32P,35S,18F,36CI.

[0115] The term “N-oxide” denotes a compound containing the N+-O' functional group, such as in the following example.

[0116] The term ’’prodrugs” refers to compounds that may be converted under physiological conditions or by solvolysis to a biologically active compound of the invention. A prodrug may be inactive when administered to a subject in need thereof, but is converted in vivo to an active compound of the invention. Prodrugs are typically rapidly transformed in vivo to yield the parent compound of the invention, e.g. by hydrolysis in the blood. The prodrug compound usually offers advantages of solubility, tissue compatibility or delayed release in a mammalian organism (see Silverman, R. B., The Organic Chemistry of Drug Design and Drug Action, 2nd Ed., Elsevier Academic Press (2004), page 498 to 549). Prodrugs of a compound of the invention may be prepared by modifying functional groups, such as a hydroxy, amino or mercapto groups, present in a compound of the invention in such a way that the modifications are cleaved, either in routine manipulation or in vivo, to the parent compound of the invention. Examples of prodrugs include, but are not limited to, acetate, formate and succinate derivatives of hydroxy functional groups or phenyl carbamate derivatives of amino functional groups.

[0117] For clinical use, the compounds disclosed herein are formulated into pharmaceutical compositions (or formulations) for various modes of administration. It will be appreciated that compounds of the invention may be administered together with a physiologically acceptable carrier, excipient, and / or diluent (i.e. one, two, or all three of these). The pharmaceutical compositions disclosed herein may be administered by any suitable route, preferably by oral, rectal, nasal, topical (including buccal and sublingual), sublingual, transdermal, intrathecal, transmucosal or parenteral (including subcutaneous, intramuscular, intravenous and intradermal) administration. Other formulations may conveniently be presented in unit dosage form, e.g., tablets and sustained release capsules, and in liposomes, and may be prepared by any methods well known in the art of pharmacy. Pharmaceutical formulations are usually prepared by mixing the active substance, or a pharmaceutically acceptable salt thereof, with conventional pharmaceutically acceptable carriers, diluents or excipients. Examples of excipients are water, gelatin, gum arabicum, lactose, microcrystalline cellulose, starch, sodium starch glycolate, calcium hydrogen phosphate, magnesium stearate, talcum, colloidal silicon dioxide, and the like. Such formulations may also contain other pharmacologically active agents, and conventional additives, such as stabilizers, wetting agents, emulsifiers, flavouring agents, buffers, and the like. Usually, the amount of active compounds is between 0.1-95% by weight of the preparation, preferably between 0.2-20% by weight in preparations for parenteral use and more preferably between 1-50% by weight in preparations for oral administration. The formulations can be further prepared by known methods such as granulation, compression, microencapsulation, spray coating, etc. The formulations may be prepared by conventional methods in the dosage form of tablets, capsules, granules, powders, syrups, suspensions, suppositories or injections. Liquid formulations may be prepared by dissolving or suspending the active substance in water or other suitable vehicles. Tablets and granules may be coated in a conventional manner. To maintain therapeutically effective plasma concentrations for extended periods of time, compounds disclosed herein may be incorporated into slow-release formulations.

[0118] In addition to the above, pharmaceutically acceptable excipients can be selected from, for example, carriers (e.g. a solid, liquid or semi-solid carrier), adjuvants, diluents (e.g. solid diluents such as fillers or bulking agents; and liquid diluents such as solvents and co-solvents), granulating agents, binders, flow aids, coating agents, release-controlling agents (e.g. release retarding or delaying polymers or waxes), binding agents, disintegrants, buffering agents, lubricants, preservatives, anti-fungal and antibacterial agents, antioxidants, buffering agents, tonicityadjusting agents, thickening agents, flavouring agents, sweeteners, pigments, plasticizers, taste masking agents, stabilisers or any other excipients conventionally used in pharmaceutical compositions. In view of the above, a second aspect of the invention provides a pharmaceutical composition comprising a compound of the invention, including a salt, solvate, hydrate, N-oxide or prodrug thereof, and a pharmaceutically acceptable excipient.

[0119] The dose level and frequency of dosage of the specific compound will vary depending on a variety of factors including the potency of the specific compound employed, the metabolic stability and length of action of that compound, the patient’s age, body weight, general health, sex, diet, mode and time of administration, rate of excretion, drug combination, the severity of the condition to be treated, and the patient undergoing therapy. The daily dosage may, for example, range from about 0.001 mg to about 100 mg per kilo of body weight, administered singly or multiply in doses, e.g. from about 0.01 mg to about 25 mg each. Normally, such a dosage is given orally but parenteral administration may also be chosen.

[0120] An object of the present invention relates to the compounds of the invention for use as a medicament. The term ‘medicament’ denotes a substance used for medical treatment or as a medicine. The compounds of the invention may be useful as inhibitors of SARS-CoV-2 Mpro. As such, they are useful in the treatment or prevention of medical conditions (disease or disorder) that are affected by SARS-CoV-2 Mpro.

[0121] In view of the above, a third aspect of the invention provides a compound of the invention, or a pharmaceutical composition comprising said compound, for use in the treatment of SARS-CoV-2 or in the treatment of disorders associated with SARS-CoV-2.

[0122] In a fourth aspect of the invention, there is provided a use of a compound of the invention in the manufacture of a medicament for the treatment of SARS-CoV-2 or a disorder associated with SARS-CoV-2.

[0123] In a fifth aspect of the invention, there is provided a method of treating a disease or disorder susceptible to SARS-CoV-2 Mpro inhibition in a subject in need thereof, said method comprising administering to said subject a pharmaceutically effective amount of a compound of the invention, or salt, solvate, hydrate, N-oxide or prodrug thereof. Afeature of this aspect is that the disease or disorder is SARS- CoV-2 or a disorder associated with SARS-CoV-2.

[0124] In view of the above, the compounds of the invention may be useful in preventing death or complications arising due to chronic underlying conditions or comorbidities in patients infected with SARS-CoV-2. Such chronic underlying conditions or comorbidities may include for example hypertension, obesity, chronic lung conditions (TB, asthma and cystic fibrosis), diabetes and cardiovascular conditions (coronary heart disease, congenital heart disease and heart failure).

[0125] The term “treatment” and “treating” as used herein may include prophylaxis of the named disease or disorder, or amelioration or elimination of the disease or disorder once it has been established.

[0126] As used herein, the terms “administration” or “administering” mean a route of administration for a compound disclosed herein. Exemplary routes of administration include, but are not limited to, oral, intravenous, intraperitoneal, intraarterial, and intramuscular. The preferred route of administration can vary depending on various factors, e.g. the components of the pharmaceutical composition comprising a compound disclosed herein, site of the potential or actual disease and severity of disease.

[0127] The terms “subject” and “patient” are used herein interchangeably. They refer to a human or another mammal (e.g., mouse, rat, rabbit, dog, cat, cattle, swine, sheep, horse or primate) that can be afflicted with or is susceptible to a disease or condition but may or may not have the disease or condition. It is preferred that the subject is human.

[0128] “A therapeutically effective amount” refers to an amount of a compound of the invention that confers a therapeutic effect on the treated subject. The therapeutic effect may be objective (i.e. measurable by some test or marker) or subjective (i.e. subject gives an indication of or feels an effect). Methods delineated herein include those wherein the subject is identified as in need of a particular stated treatment. Identifying a subject in need of such treatment can be in the judgment of a subject or a health care professional and can be subjective (e.g. opinion) or objective (e.g. measurable by a test or diagnostic method).

[0129] In other aspects, the methods herein include those further comprising monitoring subject response to the treatment administrations. Such monitoring may include periodic sampling of subject tissue, fluids, specimens, cells, proteins, chemical markers, genetic materials, etc. as markers or indicators of the treatment regimen. In other methods, the subject is pre-screened or identified as in need of such treatment by assessment for a relevant marker or indicator of suitability for such treatment.

[0130] Compounds of the invention may be for use as a single agent or in combination with one or more additional pharmaceutical agents. For examples, the compounds of the invention may be co-administered with HIV drugs which are known to block CYP450 mediated metabolism, such as ritonavir or a combination of lopinavir / ritonavir.

[0131] In some embodiments, the compounds of the present invention may be administered with a CYP450 inhibitor, such as a CYP3A4 inhibitor, such as ritonavir. Such administration may be sequential or simultaneous.

[0132] In some embodiments, the present invention provides a pharmaceutical composition comprising a compound of Formula (I) as described herein, such as the compound of Example 1 or 2, together with a CYP450 inhibitor, such as a CYP3A4 inhibitor, such as ritonavir.

[0133] PREPARATION OF COMPOUNDS OF THE INVENTION

[0134] The compounds of the invention may be prepared by, or in analogy with, conventional methods. The preparation of intermediates and compounds according to the examples of the present invention may in particular be illuminated by the following Schemes. Definitions of variables in the structures in schemes herein are commensurate with those of corresponding positions in the formulae delineated herein.

[0135] General procedures

[0136] Where no preparative routes are included, the relevant intermediate is commercially available. Commercial reagents were utilized without further purification. Room temperature (rt) refers to approximately 20-27°C. 1 H NMR spectra were recorded at 300 or 400 MHz on Bruker instruments. Chemical shift values are expressed in parts per million (ppm), i.e. (G)-values, relative to tetramethylsilane. The following abbreviations are used for the multiplicity of the NMR signals: s=singlet, br=broad, d=doublet, t=triplet, q=quartet, quin=quintet, h=heptet, dd=doublet of doublets, dt=double of triplets, m=multiplet. Coupling constants are listed as J values, measured in Hz. NMR and mass spectroscopy results were corrected to account for background peaks. TLC for monitoring reactions refers to TLC run using silica gel as a stationary phase.

[0137] LCMS experiments were carried out under the following conditions: Instrument: Agilent Technologies 1290 infinity II series with MSD;

[0138] Method A: Mobile phase: A :0.1% HCOOH in H2O: B: 100% ACN; Flow Rate: 1.5 mL / min; Column: XBridge C8 (50 x 4.6mm) 3.5 pm.

[0139] Method B: Mobile Phase: A: 0.1 % TFA in H2O; B: 100% ACN; Flow Rate: 1.5 mL / min; Column: XBridge C8 (50 x 4.6 mm), 3.5 pM.

[0140] Method C: Mobile Phase: A: 0.1 % HCOOH in H2O: ACN (95:5), B: ACN; Flow Rate: 1.5 mL / min; Column: ZORBAX XDB C-18 (50 x 4.6 mm) 3.5 pM.

[0141] Method D: Mobile Phase: A: 10mM Ammonium Bicarbonate in Water, B: ACN; Flow Rate: 1 .5 mL / min; Column : XBridge C8 (50 x 4.6mm) 3.5 pm.

[0142] Method E: Mobile phase :A : 5mM NH4HCO3 in H2O;B:ACN: B: 100% ACN; Flow Rate :1 .5 ml / min: Column : XBridge C8 (50 x 4.6mm) 3.5 pm. UPLC experiments were carried out under the following conditions:

[0143] Instrument: Waters Acquity I Class;

[0144] Method A: Mobile Phase: A: 0.1 %TFAin Water, : B: 100% Acetonitrile; Flow Rate: 0.8 mL / min; Column: Acquity BEH-C18(50X2.1mm)1.7pm

[0145] Prep HPLC experiments were carried out under the following conditions.

[0146] Method A: Instrument: Agilent Technologies 1260 Infinity II Series LC; Column: YMC Exrs C18, 5pm, 30x150mm; Gradient [time (min) / solvent B in A(%)]: 0.0 / 10, 20 / 95, 23 / 95, 24 / 10, 26 / 10 (Solvent A 0.1 % HCO2H in H2O, Solvent B=MeCN).

[0147] Method B: Instrument: Grace Reveleris; Column: 43 g C18 Redisep (CV 42.4 M- 40 mL / min) Mobile Phase: A: 0.1% TFA in H2O, B: ACN; Flow Rate: 15 mL / min;

[0148] Abbreviations

[0149] DCM = dichloromethane

[0150] DMF = A / ,A / -dimethylformamide

[0151] DMP = Dess-Martin Periodinane

[0152] DIPEA = A / ,A / -diisopropylethylamine

[0153] DMSO = dimethylsulfoxide

[0154] EtOAc = ethyl acetate h = hour(s)

[0155] HATU = 1-[bis(dimethylamino)methylene]-1 / - / -1 ,2,3-triazolo[4,5- b]pyridinium

[0156] 3-oxide hexafluorophosphate

[0157] HPLC = high performance liquid chromatography

[0158] L = litre

[0159] LC = liquid chromatography

[0160] □HMDS = lithium bis(trimethylsilyl)amide

[0161] MeCN = acetonitrile min = minute(s)

[0162] MS = mass spectrometry

[0163] NMR = nuclear magnetic resonance

[0164] Rt or RT = room temperature

[0165] SFC = supercritical fluid chromatography

[0166] T3P = propylphosphonic anhydride

[0167] THF = tetrahydrofuran

[0168] TLC = thin layer chromatography

[0169] UPLC = ultra performance liquid chromatography

[0170] Prefixes n-, s-, / -, t- and tert- have their usual meanings: normal, secondary, iso, and tertiary. SYNTHESIS OF INTERMEDIATES

[0171] Intermediate 1 : 3-amino-A / -cyclopropyl-2-hydroxy-4-((S)-2-oxopyrrolidin-3- yl)butanamide

[0172] Step 1 : To a suspension of dimethyl (tert-butoxycarbonyl)-L-glutamate (CAS No. 59279-60-6, 30 g, 109 mmol) in tetrahydrofuran (300 ml_), LiHMDS (240 ml_, 240 mmol) was added dropwise at-78 °C and the resulting reaction mixture was stirred at -78 °C for 1 h followed by the addition of bromoacetonitrile (21 .79 ml, 131 mmol) at the same temperature. The resulting reaction mixture was continued to stir another 3 h at -78 °C. After completion of reaction (monitored by TLC), the reaction mixture was quenched with saturated NH4CI solution (300 mL) and the aqueous layer was extracted with EtOAc (2 x 500 mL). The combined organic layers were dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The resulting crude compound was purified by flash column chromatography (silica gel: 100-200 mesh; eluent: 15-20% EtOAc in pet-ether) to afford dimethyl (2S,4R)-2-((tert-butoxycarbonyl)amino)-4-(cyanomethyl)pentanedioate (35 g, 108 mmol, 99% yield) as a pale yellow gum.

[0173] LCMS (Method A): m / z 215.3 [(M+H+)-100], at 2.05 min.

[0174] To a stirred solution of dimethyl (2S,4R)-2-((tert-butoxycarbonyl)amino)-4-

[0175] (cyanomethyl)pentanedioate (30 g, 95 mmol) in methanol (300 mL) at 0 °C, cobalt(ll) chloride hexahydrate (11.35 g, 47.7 mmol) was added. NaBH4(21.66 g,

[0176] 573 mmol) was added portionwise over 1 h and the resulting reaction mixture was stirred for 16 h at RT. After completion of the reaction (monitored by TLC), the reaction mixture was diluted with water (300 mL) and the aqueous layer was extracted with EtOAc (2 x 500 mL). The combined organic layers were dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The resulting crude compound was purified by flash column chromatography (silica gel: 100-200 mesh, eluent: 50-100% EtOAc in pet-ether) to afford methyl (S)-2- ((tert-butoxycarbonyl)amino)-3-((S)-2-oxopyrrolidin-3-yl)propanoate (13.6 g, 47.5 mmol, 50% yield) as a yellow gum.

[0177] LCMS (Method A): m / z 187.1 [(M+H+)-100], at 1.87 min.

[0178] 1H NMR: (300 MHz, DMSO-cfe) 6 7.64 (s, 1 H), 7.42 (d, J=7.8 Hz, 1 H), 4.06-4.02 (m, 1 H), 3.69 (s, 3H), 3.16-3.08 (m, 2H), 2.32-2.21 (m, 1 H), 2.16-2.11 (m, 1 H), 2.03-1.93 (m, 1 H), 1.69-1.66 (m, 2 H), 1.33 (s, 9H).

[0179] To a stirred solution of methyl (S)-2-((tert-butoxycarbonyl)amino)-3-((S)-2- oxopyrrolidin-3-yl)propanoate (15 g, 52.4 mmol) in tetrahydrofuran (120 mL) and methanol (40 mL) at 0 °C, NaBH4(4.36 g, 115 mmol) was added portionwise and the reaction mixture was allowed to stir for 5 h at RT. After completion of the reaction (monitored by TLC), the reaction mixture was diluted with water (200 mL), the aqueous layer was extracted with EtOAc (2 x 500 mL), the combined organic layers were dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to give a crude residue that was purified by flash column chromatography (silica gel: 100-200 mesh; eluent: 0-5% MeOH in DCM) to afford tert-butyl ((S)-1-hydroxy-3-((S)-2-oxopyrrolidin-3-yl)propan-2-yl)carbamate (11.0 g, 42.4 mmol, 81% yield) as a white solid.

[0180] LCMS (Method A): m / z 159.4 [(M+H+)-100], at 1.40 min.

[0181] 1H NMR: (400 MHz, DMSO-ct6) 6 7.53 (s, 1 H), 6.57-6.55 (d, J = 6.60 Hz, 1 H), 4.62-4.59 (m, 1 H), 3.45-3.31 (m, 2H), 3.26-3.22 (m, 1 H), 3.16-3.13 (m, 2H), 2.22- 2.15 (m, 2H), 1.72-1.66 (m, 2H), 1.37 (s, 9H). a stirred suspension of tert-butyl ((S)-1-hydroxy-3-((S)-2-oxopyrrolidin-

[0182] 3-yl)propan-2-yl)carbamate (10 g, 38.7 mmol) in dichloromethane (150 mL) at 0 °C, the Dess-Martin periodinane (19.70 g, 46.5 mmol) was added over 30 min and the resultant reaction mixture was stirred at RT for 1 h. After completion of the reaction (monitored by TLC), the reaction mixture was quenched with saturated NaHCOs solution (70 m L), the aqueous layer was extracted with DCM (2 x 200 m L) , the combined organic layers were dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure to give a crude residue that was purified by flash column chromatography (silica gel: 230-400 mesh, eluent: 0-15% MeOH in DCM) to afford tert-butyl ((S)-1-oxo-3-((S)-2-oxopyrrolidin-3-yl)propan-2- yl)carbamate (6.94 g, 27.1 mmol, 70% yield) as a white solid.

[0183] LCMS (Method A): m / z 157.3 [(M+H+)-100], at 1.45 min.

[0184] Step 5: To a stirred solution of tert-butyl ((S)-1-oxo-3-((S)-2-oxopyrrolidin-3- yl)propan-2-yl)carbamate (4.5 g, 17.56 mmol) in dichloromethane (50 mL), was added acetic acid (2.1 mL, 35.1 mmol) followed by isocyanocyclopropane (2.36 g, 35.1 mmol) and the reaction mixture was stirred for 16 h at RT. After completion of reaction (monitored by UPLC), the reaction mixture was diluted with water (200 mL), the aqueous layer was extracted with DCM (2 x 500 mL), the combined organic layers were dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to give a crude residue that was purified by flash column chromatography (silica gel: 230-400 mesh, eluent: 0-12% MeOH in DCM) to afford 3-((tert-butoxycarbonyl)amino)-1-(cyclopropylamino)-1-oxo-4-(2-oxopyrrolidin-3- yl)butan-2-yl acetate (3,84 g, 10.0 mmol, 57% yield) as a white solid.

[0185] LCMS (Method A): m / z 284.3 [(M+H+)-100], at 1.60 min.

[0186] Step 6: To a stirred solution of 3-((tert-butoxycarbonyl)amino)-1- (cyclopropylamino)-1-oxo-4-(2-oxopyrrolidin-3-yl)butan-2-yl acetate (8 g, 20.86 mmol) in tetrahydrofuran (120 mL), water (80 mL) and methanol (40 mL) was added lithium hydroxide monohydrate (2.63 g, 62.6 mmol) at 0 °C and the reaction mixture was stirred at RT for 2 h. After completion of the reaction (monitored by UPLC), the reaction mixture was quenched with aqueous citric acid (70 mL), the aqueous layer was extracted with DCM (3 x 500 mL), the combined organic layers were dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to give a crude residue that was purified by prep HPC (Method A) to afford tert-butyl (4-(cyclopropylamino)-3-hydroxy-4-oxo-1 -(2-oxopyrrolidin-3- yl)butan-2-yl)carbamate (4.47 g, 13.1 mmol, 63% yield) as a white solid. LCMS (Method A): m / z 342.2 [M+H+], at 1.47 min.

[0187] Step 7: To a stirred solution of tert-butyl (4-(cyclopropylamino)-3-hydroxy-4-oxo-1- (2-oxopyrrolidin-3-yl)butan-2-yl)carbamate (3.8 g, 11.13 mmol) in 1 ,4-dioxane (20 mL) at 0 °C, was added HCI (4M in dioxane, 38 mL, 152 mmol) dropwise and the reaction mixture was stirred at RT for 3 h. After completion of the reaction (monitored by UPLC), the reaction mixture was concentrated under vacuum to afford 3-amino-A / -cyclopropyl-2-hydroxy-4-((S)-2-oxopyrrolidin-3-yl)butanamide hydrochloride, Intermediate 1 (3.46 g, 11.1 mmol, assumed 100% yield) as a white solid.

[0188] LCMS (Method A): m / z 242.3 [M+H+], at 0.53 min.

[0189] Intermediate 2: (S)-4,4-dimethyl-2-((S)-A / ,3,3-trimethyl-2-(2,2,2- trifluoroacetamido)butanamido)pentanoic acid

[0190] Step 1 : To a stirred solution of (S)-2-((tert-butoxycarbonyl)amino)-4,4- dimethylpentanoic acid (5 g, 20.38 mmol) in THF (100 ml_) at 0 °C, was added sodium hydride (8.15 g, 204 mmol) over 2 h. lodomethane (6.34 mL, 102 mmol) in dry THF (50 mL) was added dropwise and the reaction mixture was stirred at RT for 16 h. After completion of the reaction (monitored by UPLC), the reaction mixture was quenched with cold water (50 mL) and washed with MTBE (100 mL). The aqueous layer was acidified with 10% citric acid to pH ~ 4-5, extracted with EtOAc (2 x 300 mL), the combined organic layers were dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to afford (S)-2-((tert- butoxycarbonyl)(methyl)amino)-4,4-dimethylpentanoic acid (3.25 g, 11.9 mmol, 58% yield) as a yellow liquid which was used directly in the next step.

[0191] LCMS (Method A): m / z 160.3 [(M+H+)-100], at 2.42 min.

[0192] To a stirred solution of (S)-2-((tert-butoxycarbonyl)(methyl)amino)-4,4- dimethylpentanoic acid (4 g, 15.42 mmol) in methanol (40 mL) at 0 °C, was added thionyl chloride (9.17 g, 77 mmol) drop wise and the reaction mixture was stirred at 75 °C for 6 h. After completion of the reaction (monitored by LCMS), the reaction mixture was concentrated under vacuum to give crude methyl (S)-4,4-dimethyl-2-

[0193] (methylamino)pentanoate hydrochloride (2.86 g, 13.6 mmol, 88% yield) as a white solid which was used directly in the next step.

[0194] LCMS (Method A): m / z 174.2 [M+H+], at 0.97 min.

[0195] To a stirred solution of (S)-2-((tert-butoxycarbonyl)amino)-3,3- dimethylbutanoic acid (4.5 g, 19.46 mmol) and methyl (S)-4,4-dimethyl-2-

[0196] (methylamino)pentanoate hydrochloride (4.08 g, 19.46 mmol)) in DMF (50 mL) at 0 °C, DI PEA (7.54 g, 58.4 mmol) and HATU (11.10 g, 29.2 mmol) were added and the reaction mixture was stirred at RT for 16 h. After completion of the reaction (monitored by TLC), the reaction mixture was concentrated and the obtained residue was diluted with water (200 mL), extracted with DCM (3 x 200 mL), the combined organic layers were washed with brine solution (10 mL), dried over anhydrous Na2SO4, filtered and concentrated under vacuum. The resulting crude residue was purified by flash column chromatography (silica-gel: 230-400 mesh size, eluent: Ethyl acetate-Pet ether 0-50%) to afford the title compound methyl (S)-2-((S)-2-((tert-butoxycarbonyl)amino)-A / ,3,3-trimethylbutanamido)-4,4- dimethylpentanoate (2.78 g, 7.2 mmol, 37% yield) as a yellow gum.

[0197] LCMS (Method A): m / z 287.4 [(M+H+)-100], at 2.80 min.

[0198] To a stirred solution of methyl (S)-2-((S)-2-((tert-butoxycarbonyl)amino)-

[0199] A / ,3,3-trimethylbutanamido)-4,4-dimethylpentanoate (12 g, 31.0 mmol) in THF (60 mL), MeOH (40 mL) and water (20 mL) at RT, was added LiOH. H2O (2.23 g, 93 mmol) and the resulting reaction mixture was stirred at RT for 2 h. After completion of the reaction (monitored by UPLC), the reaction mixture was concentrated under reduced pressure and the obtained residue was dissolved in H2O (50 ml_), acidified to pH~5 using citric acid and the aqueous layer extracted with 10% MeOH in DCM (2 x 100 ml_). The combined organic layers were separated, dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to afford the (S)-2-((S)-2-((tert-butoxycarbonyl)amino)-A / ,3,3-trimethylbutanamido)-4,4- dimethylpentanoic acid (9.50 g, 17.1 mmol, 55% yield) as an off-white solid.

[0200] LCMS (Method A): m / z 373.3 [M+H+], at 2.53 min.

[0201] Step 5: To a stirred solution of (S)-2-((S)-2-((tert-butoxycarbonyl)amino)-A / ,3,3- trimethylbutanamido)-4,4-dimethylpentanoic acid (3 g, 8.05 mmol) in 1 ,4-dioxane (25 mL) at 0 °C, was added HCI (4M in dioxane, 2.00 mL, 8.05 mmol) dropwise and the reaction mixture was stirred at RT for 3 h. After completion of reaction (monitored by UPLC), the reaction mixture was concentrated under vacuum to afford (S)-2-((S)-2-amino-A / ,3,3-trimethylbutanamido)-4,4-dimethylpentanoic acid hydrochloride (2.20 g, 8.05 mmol, assumed 100% yield) as a yellow sticky gum which was used directly in the next step.

[0202] LCMS (Method A): m / z 273.4 [M+H+], at 1 .35 min.

[0203] Step 6: To a stirred solution of (S)-2-((S)-2-amino-A / ,3,3-trimethylbutanamido)-4,4- dimethylpentanoic acid hydrochloride (4 g, 12.95 mmol) in methanol (50 mL) at 0 °C, was added triethylamine (5.46 mL, 38.9 mmol) and ethyl 2,2,2-trifluoroacetate 64 ml, 38.9 mmol) and the reaction mixture stirred at RT for 8 h. After completion of the reaction (monitored by UPLC), the reaction mixture was quenched with water (500 mL), the aqueous layer was extracted with DCM (3 x 500 mL), the combined organic layers were washed with brine (5 mL), dried over anhydrous Na2SO4, filtered and concentrated under vacuum to afford (S)-4,4-dimethyl-2-((S)- A / ,3,3-trimethyl-2-(2,2,2-trifluoroacetamido)butanamido)pentanoic acid,

[0204] Intermediate 2 (3.86 g, 10.49 mmol, 81 % yield) as a yellow gum which was used directly in the next step. LCMS (Method A): m / z 367.3 [M-H+], at 2.42 min.

[0205] Intermediate 3: (S)-2-((S)-2-((tert-butoxycarbonyl)amino)-3,3- dimethylbutanamido)-4,4-dimethylpentanoic acid

[0206] Intermediate 3

[0207] Step 1 : To a stirred solution of methyl (S)-2-amino-4,4-dimethylpentanoate hydrochloride (0.85 g, 4.34 mmol) and (S)-2-((tert-butoxycarbonyl)amino)-3,3- dimethylbutanoic acid (1.00 g, 4.34 mmol) in DCM (20 ml_) at 0 °C, was added DIPEA (2.66 mL, 15.20 mmol) followed by propylphosphonic anhydride solution (>50 wt. % in ethyl acetate, 2.07 g, 6.52 mmol) and the resultant reaction mixture was stirred at RT for 16 h. After completion of the reaction (monitored by TLC & LCMS), the reaction mixture was partitioned between DCM (100 mL) and 10% NaHCOs solution (50 mL). The organic layer was separated, dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to give a crude residue that was purified by flash column chromatography (silica gel: 230-400 mesh, eluent: 0-30% EtOAc in pet-ether) to afford methyl (S)-2-((S)-2-((tert- butoxycarbonyl)amino)-3,3-dimethylbutanamido)-4,4-dimethylpentanoate (0.90 g, 2.61 mmol, 60%) as a white solid.

[0208] LCMS (Method B): m / z 273.4 [(M+H+)-100], at 2.46 min.

[0209] Step 2: To a stirred solution of methyl (S)-2-((S)-2-((tert-butoxycarbonyl)amino)- 3,3-dimethylbutanamido)-4,4-dimethylpentanoate (1 .89 g, 5.07 mmol) in a mixture of THF (20 mL), MeOH (6.67 mL) and water (13.33 mL) at RT was added LiOH- H2O (0.639 g, 15.22 mmol) and the resultant reaction mixture was stirred at RT for 2 h. After completion of the reaction (monitored by TLC), the reaction mixture was concentrated under reduced pressure and the resulting crude residue was diluted with water (5 mL), acidified with 1 ,5N HCI to pH-2-3 to give a precipitated solid that was filtered and dried under vacuum to obtain (S)-2-((S)-2-((terf- butoxycarbonyl)amino)-3,3-dimethylbutanamido)-4,4-dimethylpentanoic acid,

[0210] Intermediate 3 (1.50 g, 3.93 mmol, 78%) as an off-white solid.

[0211] LCMS (Method C): m / z 259.1 [(M+H+)-100], at 2.64 min.

[0212] Intermediate 4: methyl (S)-2-amino-3-((S)-2-oxopyrrolidin-3-yl)propanoate hydrochloride

[0213] Step 1 : To a suspension of dimethyl (tert-butoxycarbonyl)-L-glutamate (250 g, 0.908 mol) in THF (2500 mL) at -78 °C, was added LiHMDS (1 M in THF, 1997 mL, 1.997 mol) dropwise using an addition funnel and the resultant reaction mixture was stirred at -78 °C for 1 h. Bromoacetonitrile (76.5 mL, 1.086 mol) was added at -78 °C and the resultant reaction mixture was continued to stir at -78 °C for a further 3 hr. After the complete disappearance of starting material (monitored by TLC), the reaction mixture was quenched by the addition of saturated aqueous ammonium chloride solution (2 L) at -78 °C. After warming to RT the reaction mixture was extracted with EtOAc (2 x 2000 mL), the combined organic layers were dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to give a crude residue that was purified by flash column chromatography (silica gel: 100-200 mesh, eluent: 0-20% EtOAc in pet-ether) to afford (2S,4R)-2- ((tert-butoxycarbonyl)amino)-4-(cyanomethyl)pentanedioate (207 g, 0.65 mol, 73%) as a pale yellow gum.

[0214] LCMS (Method D): m / z 337.1 [M+Na+], at 1.93 min.

[0215] Step 2: To a stirred suspension of (2S,4R)-2-((tert-butoxycarbonyl)amino)-4- (cyanomethyl)pentanedioate (207 g, 0.65 mol) in MeOH (2 L) at 0 °C was added COCI2.6H2O (78.1 g, 0.33 mol) followed by the portion wise addition of NaBH4(149.6 g, 3.96 mol) and the resultant reaction mixture was stirred at RT for 15 h. After completion of the reaction (monitored by TLC), the reaction mixture was concentrated under reduced pressure, the residue was suspended in 20% MeOH in DCM (3000 ml_) and H2O (2000 ml_) and stirred for 10 min. The resultant suspension was filtered through celite and the pad rinsed with 20% MeOH in DCM (2000 mL). The layers of the combined filtrate were separated using a separating funnel, the organic layer was washed with brine solution (2000 mL), dried over anhydrous Na2SO4 and concentrated under reduced pressure to get a crude residue that was purified by flash column chromatography (silica gel: 100-200 mesh, eluent: 0-100% EtOAc in pet-ether) to afford methyl (S)-2-((tert- butoxycarbonyl)amino)-3-((S)-2-oxopyrrolidin-3-yl)propanoate (92 g, 0.32 mol, 49%) as a pale yellow solid.

[0216] LCMS (Method D): m / z 187.2 [(M+H+)-100], at 1.34 min.

[0217] Step 3: To a stirred solution of methyl (S)-2-((te / Y-butoxycarbonyl)amino)-3-((S)-2- oxopyrrolidin-3-yl)propanoate (10 g, 34.0 mmol) in 1 ,4-dioxane (50 ml_) at 0 °C was added 4 N HCI in 1 ,4-dioxane (100 ml_) and the resultant reaction mixture was stirred at RT for 3 h. After completion of the reaction (monitored by TLC), the solvent was evaporated and the resultant gummy solid was dried under hi-vacuum for 16h to give methyl (S)-2-((tert-butoxycarbonyl)amino)-3-((S)-2-oxopyrrolidin-3- yl)propanoate, Intermediate 4 (92 g, 34.0 mmol, assumed 100%) as a yellow gum which was used directly without any further purification.

[0218] LCMS (Method E): m / z 187.3 [M+H+], at 0.83-1.13 min.

[0219] SYNTHESIS OF EXAMPLES

[0220] Example 1 : ((2S)-A / -(4-(cyclopropylamino)-3,4-dioxo-1-((S)-2-oxopyrrolidin- 3-yl)butan-2-yl)-4,4-dimethyl-2-((S)-A / ,3,3-trimethyl-2-(2,2,2- trifluoroacetamido)butanamido)pentanamide) Step 1 : To a stirred solution of (S)-4,4-dimethyl-2-((S)-A / ,3,3-trimethyl-2-(2,2,2- trifluoroacetamido)butanamido)pentanoic acid, Intermediate 2 (5 g, 13.57 mmol) and 3-amino-A / -cyclopropyl-2-hydroxy-4-((S)-2-oxopyrrolidin-3-yl)butanamide hydrochloride, Intermediate 1 (4.2 g, 15.12 mmol) in DMF (50 ml_) at 0 °C, was added HATU (7.74 g, 20.36 mmol) and the reaction mixture stirred at RT for 2 h. After completion of the reaction (monitored by UPLC), the reaction mixture was diluted with water (500 mL), the aqueous layer was extracted with DCM (3 x 500 ml_), the combined organic layers were dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to give a crude residue that was purified by prep HPLC (Method B). The desired fractions were combined, concentrated under vacuum and the obtained residue was washed with saturated aqueous sodium bicarbonate solution (100 mL). The aqueous layer was extracted with DCM (3 x 100 mL), the combined organic layers were dried over anhydrous Na2SO4, filtered, concentrated under reduced pressure and lyophilised to afford (2S)-A / -(4- (cyclopropylamino-3-hydroxy-4-oxo-1-((S)-2-oxopyrrolidin-3-yl)butan-2-yl)-4,4- dimethyl-2-((S)-A / ,3,3-trimethyl-2-(2,2,2- trifluoroacetamido)butanamido)pentanamide (4.28 g, 7.23 mmol, 53% yield) as an off white solid.

[0221] LCMS (Method A): m / z 592.4 [M+H+], at 2.05 min.

[0222] 1H NMR: (400 MHz, DMSO-cfe) 6 9.51-9.41 (m, 1 H), 7.76-7.78 (m, 1 H), 7.56-7.35 (m, 1 H), 7.12-7.06 (m, 1 H), 5.76-5.74 (m, 2H), 5.60-5.59 (m, 1 H), 5.24-5.22 (m, 1 H), 4.85-4.83 (m, 1 H),3.85-3.82(m, 1 H) , 3.21-3.19 (m, 2H), 3.15 (m, 1 H), 2.77- 2.75 (m, 1 H), 2.33-2.31 (m, 2H), 2.30-2.17 (m, 1 H), 1.94-1.81 (m, 1 H), 1.80-1.72 (m, 2H), 1.53-1.49 (m, 1 H), 1.02-0.99 (m, 10H), 0.99-0.86 (m, 9H), 0.58-0.45 (m, 4H).

[0223] Step 2: To a stirred suspension of ((2S)-A / -(4-(cyclopropylamino)-3-hydroxy-4-oxo- 1-((S)-2-oxopyrrolidin-3-yl)butan-2-yl)-4,4-dimethyl-2-((S)-A / ,3,3-trimethyl-2- (2,2,2-trifluoroacetamido)butanamido)pentanamide (2 g, 3.38 mmol) in DCM (35 mL) at 0 °C was added Dess-Martin periodinane (2.87 g, 6.76 mmol) portion wise and the resulting reaction mixture was stirred at RT for 1 h. After completion of the reaction (monitored by UPLC), the reaction mixture was quenched with saturated NaHCOs solution (200 ml_), the aqueous layer was extracted with DCM (3 x 350 m L) and the combined organic layers were washed with brine solution (200 mL), dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure. The resulting residue was purified by prep HPLC (Method A) and the desired fractions were combined, concentrated under reduced pressure and lyophilised to afford ((2S)-A / -(4-(cyclopropylamino)-3,4-dioxo-1-((S)-2-oxopyrrolidin-3-yl)butan- 2-yl)-4,4-dimethyl-2-((S)-A / ,3,3-trimethyl-2-(2,2,2- trifluoroacetamido)butanamido)pentanamide), Example 1 (0.718 g, 1.22 mmol, 36% yield) as an off white solid. LCMS (Method A): m / z 590.3 [M+H+], at 1 .94-2.19 min.

[0224] 1H NMR: (400 MHz, DMSO-cfe) 6 8.87-8.85 (m, 1 H), 8.38-8.34 (m, 2H), 7.42 (m, 1 H), 5.24-5.22 (m, 1 H), 4.85-4.83 (m, 1 H), 4.86 (m, 1 H), 3.21-3.19 (m, 2H), 3.15- 3.00 (m, 1 H), 2.77-2.75 (m, 1 H), 2.33-2.31 (m, 2H), 2.30-2.17 (m, 1 H), 1.94-1.81 (m, 1 H), 1.80-1.72 (m, 3H), 1.53-1.49 (m, 1 H), 1.03-1.02 (m, 10H), 1.00-0.98 (m, 9H), 0.68-0.62 (m, 4H).

[0225] Example 2: (2S)-A / -(4-(cyclopropylamino)-3,4-dioxo-1-((S)-2-oxopyrrolidin-3- yl)butan-2-yl)-2-((S)-3,3-dimethyl-2-(2,2,2-trifluoroacetamido)butanamido)- 4,4-dimethylpentanamide To a stirred solution of methyl (S)-2-amino-3-((S)-2-oxopyrrolidin-3- yl)propanoate hydrochloride, Intermediate 4 (1.3 g, 5.84 mmol) and (S)-2-((S)-2-

[0226] ((tert-butoxycarbonyl)amino)-3,3-dimethylbutanamido)-4,4-dimethylpentanoic acid, Intermediate 3 (1.5 g, 4.18 mmol) in DCM (20 ml_) at 0 °C, was added A / - ethyl-A / -isopropylpropan-2-amine (3.57 mL, 20.43 mmol) followed by the addition of propylphosphonic anhydride solution (>50 wt. % in ethyl acetate, 5.57 g, 8.76 mmol) and the resultant reaction mixture was stirred at RT for 16 h. After completion of the reaction (monitored by TLC & LCMS), the reaction mixture was partitioned between DCM (100 mL) and 10% aqueous NaHCOs solution (50 mL) to afford crude product. The obtained crude residue was purified by flash column chromatography (silica gel: 230-400 mesh, eluent: 0-6% DCM in in MeOH) to afford methyl (6S,9S)-6-(tert-butyl)-2,2-dimethyl-9-neopentyl-4,7, 10-trioxo-12- (((S)-2-oxopyrrolidin-3-yl)methyl)-3-oxa-5,8, 11 -tri azatri decan- 13-oate (0.70 g, 1.29 mmol, 29% yield) as an off-white solid.

[0227] LCMS (Method B): m / z 527.4 [M+H+], at 2.02 min.

[0228] To a stirred solution of methyl (6S,9S)-6-(tert-butyl)-2,2-dimethyl-9- neopentyl-4,7, 10-trioxo-12-(((S)-2-oxopyrrolidin-3-yl)methyl)-3-oxa-5,8, 11 - triazatridecan-13-oate (0.7 g, 1.33 mmol) in THF (15 mL) at 0 °C, was added MeOH (5 mL) and NaBH4(0.111 g, 2.92 mmol) portion-wise and the resultant reaction mixture was stirred at RT for 16 h. After completion of the reaction (monitored by TLC & LCMS), the reaction mixture was partitioned between 20% MeOH in DCM (100 mL) and H2O (50 mL). The organic layer was separated, dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to obtain a crude residue that was purified by flash column chromatography (silica gel: 230-400 mesh, eluent: 0-6% DCM in MeOH) to afford tert-butyl ((2S)-1-(((2S)- 1 -((1 -hydroxy-3-((S)-2-oxopyrrolidin-3-yl)propan-2-yl)amino)-4,4-dimethyl-1 - oxopentan-2 -yl)amino)-3,3-dimethyl-1-oxobutan-2-yl)carbamate (0.52 g, 1.02 mmol, 77% yield) as an off-white solid.

[0229] LCMS (Method B): m / z 499.5 [M+H+], at 1 .81 min. Step 3: To a stirred solution of tert-butyl ((2S)-1-(((2S)-1-((1-hydroxy-3-((S)-2- oxopyrrolidin-3-yl)propan-2-yl)amino)-4,4-dimethyl-1 -oxopentan-2 -yl)amino)-3, 3- dimethyl-1-oxobutan-2-yl)carbamate (0.51 g, 1.02 mmol) in DCM (10 ml_) at RT, was added Dess-Martin Periodinane (0.87 g, 2.03 mmol) portion-wise and the reaction mixture stirred at RT for 2 h. After completion of the reaction (monitored by TLC & LCMS), the reaction mixture was quenched with 10% aqueous NaHCOs solution (50 mL) and extracted with DCM (2 x 50 mL). The combined organic layers were dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to give a crude residue that was purified by flash column chromatography (silica gel: 230-400 mesh, eluent: 0-6% DCM in MeOH) to afford tert-butyl ((2S)-1 -(((2S)-4,4-dimethyl-1 -oxo-1 -((1 -oxo-3-((S)-2-oxopyrrolidin-3- yl)propan-2-yl)amino)pentan-2-yl)amino)-3,3-dimethyl-1-oxobutan-2- yl)carbamate (0.45 g, 0.62 mmol, 61% yield) as an off-white solid.

[0230] LCMS (Method B): m / z 497.4 [M+H+], at 1 .78 min.

[0231] Step 4: To a stirred solution of tert-butyl ((2S)-1 -(((2S)-4,4-dimethyl-1 -oxo-1 -((1- oxo-3-((S)-2-oxopyrrolidin-3-yl)propan-2-yl)amino)pentan-2-yl)amino)-3,3- dimethyl-1-oxobutan-2-yl)carbamate (0.45 g, 0.91 mmol) in DCM (5 mL) at RT, was added acetic acid (0.104 mL, 1.81 mmol) followed by isocyanocyclopropane (0.091 g, 1.36 mmol) portion-wise and the resultant reaction mixture was stirred at RT for 16 h. The reaction mixture was concentrated under reduced pressure, azeotropically dried with DCM (2 x 5 mL) to obtain a crude residue that was purified by flash column chromatography (silica gel: 230-400 mesh, eluent: 0-7% DCM in MeOH) to afford (6S,9S)-6-(tert-butyl)-14-(cyclopropylamino)-2,2- dimethyl-9-neopentyl-4,7, 10, 14-tetraoxo-12-(((S)-2-oxopyrrolidin-3-yl)methyl)-3- oxa-5,8,11-triazatetradecan-13-yl acetate (0.5 g, 0.66 mmol, 73% yield) as an off- white solid.

[0232] LCMS (Method B): m / z 624.5 [M+H+], at 1 .96 min.

[0233] Step 5: To a stirred solution of (6S,9S)-6-(tert-butyl)-14-(cyclopropylamino)-2,2- dimethyl-9-neopentyl-4,7, 10, 14-tetraoxo-12-(((S)-2-oxopyrrolidin-3-yl)methyl)-3- oxa-5,8,11-triazatetradecan-13-yl acetate (0.5 g, 0.80 mmol) in tetrahydrofuran (3 mL), MeOH (0.5 mL) and water (2.0 ml_) at RT, lithium hydroxide monohydrate (0.10 g, 2.41 mmol) was added at RT and the resulting reaction mixture was stirred at RT for 16 h. After completion of the reaction (monitored by TLC and LC-MS), the reaction mixture was concentrated under reduced pressure, the obtained residue was diluted with water (10 mL), the aqueous layer was acidified with 1 .5 N HCI to pH-2-3 and extracted with EtOAc (2 x 20 mL). The combined organic layers were dried over anhydrous Na2SO4, filtered and concentrated under vacuum to give a crude residue that was purified by flash column chromatography (silica gel: 230-400 mesh, eluent: 0-7% DCM in MeOH) to afford tert-butyl ((2S)- 1 -(((2S)-1 -((4-(cyclopropylamino)-3-hydroxy-4-oxo-1 -((S)-2-oxopyrrolidin-3- yl)butan-2-yl)amino)-4,4-dimethyl-1 -oxopentan-2 -yl)amino)-3, 3-dimethyl-1- oxobutan-2-yl)carbamate (0.43 g, 0.73 mmol, 92% yield) as an off white gum.

[0234] LCMS (Method B): m / z 582.4 [M+H+], at 1.86 min.

[0235] Step 6: To a stirred solution of tert-butyl ((2S)-1-(((2S)-1-((4-(cyclopropylamino)-3- hydroxy-4-oxo-1-((S)-2-oxopyrrolidin-3-yl)butan-2-yl)amino)-4,4-dimethyl-1- oxopentan-2-yl)amino)-3,3-dimethyl-1-oxobutan-2-yl)carbamate (0.35 g, 0.60 mmol) in 1 ,4-Dioxane (2 mL) at 0 °C, was added HCI (4 M in 1 ,4-Dioxane, 2 mL, 8.00 mmol) dropwise and the resulting reaction mixture was stirred at RT for 2 h. After completion of the reaction (monitored by TLC & LCMS), the solvent was concentrated under reduced pressure to afford (2S)-2-((S)-2-amino-3,3- dimethylbutanamido)-A / -(4-(cyclopropylamino)-3-hydroxy-4-oxo-1-((S)-2- oxopyrrolidin-3-yl)butan-2-yl)-4,4-dimethylpentanamide hydrochloride (0.27 g, 0.40 mmol, 68% yield) as a light brown solid.

[0236] LCMS (Method B): m / z 482.4 [M+H+], at 1 .15 min.

[0237] Step 7: To a mixture of (2S)-2-((S)-2-amino-3,3-dimethylbutanamido)-A / -(4- (cyclopropylamino)-3-hydroxy-4-oxo-1-((S)-2-oxopyrrolidin-3-yl)butan-2-yl)-4,4- dimethylpentanamide hydrochloride (0.21 g, 0.36 mmol) in DCM (5 mL) at 0 °C was added triethylamine (0.037 g, 0.36 mmol) and a solution of 2,2,2- trifluoroacetic anhydride (0.12 g, 0.55 mmol) in DCM (2 mL) drop wise and the reaction mixture was stirred at RT for 15 h. After completion of the reaction (monitored by LCMS), the reaction mixture was partitioned between water (10 ml_) and EtOAc (10 mL), the aqueous layer was extracted with EtOAc (2 x 20 mL), the combined organic layers were washed with brine solution (10 mL), dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure. The obtained brown gum residue was dissolved in THF (6 mL) and water (3 mL), 10% aqueous sodium bicarbonate solution (2 mL) was added and the mixture stirred at RT for 1 h. The aqueous layer was extracted with EtOAc (2 x 20 mL), the combined organic layer were dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to afford of (2S)-A / -(4-(cyclopropylamino)- 3-hydroxy-4-oxo-1-((S)-2-oxopyrrolidin-3-yl)butan-2-yl)-2-((S)-3,3-dimethyl-2- (2,2,2-trifluoroacetamido)butanamido)-4,4-dimethylpentanamide (109 mg, 0.19 mmol, 51 %) as an off-white solid which was used directly in the next step without further purification.

[0238] LCMS (Method B): m / z 578.5 [M+H+], at 1.78 min.

[0239] Step 8: To a stirred solution of (2S)-A / -(4-(cyclopropylamino)-3-hydroxy-4-oxo-1- ((S)-2-oxopyrrolidin-3-yl)butan-2-yl)-2-((S)-3,3-dimethyl-2-(2,2,2- trifluoroacetamido)butanamido)-4,4-dimethylpentanamide (180 mg, 0.31 mmol) in DCM (18 mL) at 0 °C, was added Dess-Martin Periodinane (264 mg, 0.62 mmol) and the resulting reaction mixture was stirred at RT for 1 h. After completion of the reaction (monitored by LCMS), the reaction mixture was quenched with 10% aqueous NaHCOs solution (15 mL), the aqueous layer was extracted with EtOAc (2 x 30 mL), the combined organic layers were dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to give a crude residue that was purified by prep HPLC (Method A). The desired fractions were combined, concentrated under reduced pressure and lyophilised to afford (2S)-A / -(4- (cyclopropylamino)-3,4-dioxo-1-((S)-2-oxopyrrolidin-3-yl)butan-2-yl)-2-((S)-3,3- dimethyl-2-(2,2,2-trifluoroacetamido)butanamido)-4,4-dimethylpentanamide, Example 2 (18 mg, 0.031 mmol, 9.8%) as a white solid.

[0240] LCMS (Method B): m / z 576.4 [M+H+], at 1 .75-1 .96 min.1H NMR: (400 MHz, DMSO-cfe) 6 9.17 (d, J = 9.60 Hz, 1 H), 8.77 (d, J = 5.20 Hz, 1 H), 8.50 (d, J = 7.60 Hz, 1 H), 8.32-8.28 (m, 1 H), 7.67 (s, 1 H), 5.05-4.99 (m, 1 H), 4.42-4.39 (m, 2H), 3.19-3.17 (m, 1 H), 3.11-3.07 (m, 1 H), 2.75-2.65 (m, 1 H), 2.42- 2.35 (m, 1 H), 2.19-2.11 (m, 2H), 1.90-1.81 (m, 1 H), 1.75-1.65 (m, 1 H), 1.61-1.51 (m, 1 H), 1.50-1.40 (m, 1 H), 0.97-0.86 (m, 18H), 0.66-0.64 (m, 2H), 0.59-0.56 (m, 2H).

[0241] BIOLOGICAL DATA

[0242] Construct design of SARS-CoV-2 Mpro

[0243] The SARS CoV-2-Mpro (Main Protease / 3C-like protease, UniProt ID: P0DTD1) protein sequence, up to and including its autocleavage boundaries, as well as the preceding N-terminal 5 amino acid residues, including the P1 glutamine residue, were codon optimised for E. coli expression and cloned into pET26b (Merck, #US169862-3) or pGEX6P1 (Fisher Scientific, #10350355) vectors using BamHI and Xho\ sites. The expression constructs thus featured a native viral N-terminal sequence, as well as a C-terminal modified 3C-protease cleavage site (LEVLFQGK), with an alternative lysine residue at the P2’ position, followed by a polyhistidine (His-8) tag.

[0244] Protein expression and protein purification

[0245] Chemically competent BL21(DE3)-RIL E. coli (Agilent, #230240) cells were transformed with the relevant coronavirus Mpro construct and grown overnight at 37 °C on LB agar plates supplemented with the appropriate antibiotics. All culture steps were performed at 37 °C unless otherwise stated. A scraping of colonies was grown in 15 mL of antibiotic supplemented LB media, for a period of approximately 2 hours, taking care not to exceed an optical density (OD) density of 2.0 as measured in a spectrophotometer at 600 nm. This preculture was used to inoculate a 500 mL expression culture: either LB media for IPTG induced expression or autoinduction superbroth media (Formedium, #AIMSB0210). In LB media, expression was induced at an OD of 0.7-1 .0 by the addition of IPTG to a final concentration of 0.5 mM. The culture was then grown at 18 °C overnight. In autoinduction expression, the temperature was dropped to 18 °C once an OD of 0.7-1.0 was observed then grown overnight. The cells were harvested by centrifugation and frozen until use.

[0246] Thawed cells were resuspended into resuspension buffer: 20 mM Tris-HCI pH 8.0, 150 mM NaCI, and DNase I (Merck #4716728001) and lysed by sonication. The lysate was clarified by centrifugation at 23,000 ref for 15 mins at 4 °C. The supernatant was loaded onto 5 mL of NiNTA resin (Cytiva, #17-5248-02) at a flowrate of 0.5 mL / min. The resin was washed with the same buffer as above containing 20 mM imidazole. Mpro protein was eluted using the same buffer containing 250 mM imidazole. The target protein was further purified using a Superdex S75 16 / 60 pg (GE, #GE28-9893-33) column in resuspension buffer. Protein purity was assessed by SDS-PAGE and identity confirmed by mass spectrometry. Purified protein was concentrated and frozen until later use.

[0247] SARS-CoV-2 Mpro enzyme assay

[0248] The activity of SARS-Cov-2 Mpro was determined in a Fluorescence Resonance Energy Transfer (FRET)-based enzymatic assay using FRET Substrate Dabcyl- KTSAVLQSGFRKM-E(Edans)~Amide. In brief, 100 nL of test compounds (concentrations ranging from 10 pM to 0.00051 pM) was preincubated with 5 pL of 5 nM (final concentration) Mpro enzyme for 20 min at room temperature in an assay buffer containing 20 mM Tris (pH 7.5), 100 mM NaCI and 1 mM EDTA. Reaction was initiated by addition of 5 pL of 25 pM (final concentration) of FRET substrate (Dabcyl-KTSAVLQSGFRKM-E (Edans)-Amide). The resulting fluorescent intensity at Ex=360 nm / Em=490 nm was measured every 90 s over the course of 60 min at room temperature using a PHERAstar plate reader (BMG Labtech). Using MARS software (BMG Labtech), the linear portion of the reaction was selected and the rate in RFU per minute calculated. Boceprevir was used a reference standard compound. pICso and pKi were determined using 4PL GraphPad Prism and data were represented as a mean n=2± SD. pKi values of compounds of the invention are shown in Table 2 below.

[0249] Table 2

[0250] Virus induced cytotoxicity assay

[0251] The compound of Example 1 was also tested in a virus induced cytotoxicity assay, in which VeroE6 / TMPRSS2 kidney epithelial cells from a non-human primate were grown as a monolayer. The cells were plated in 96-well plate at the density of 20,000 cells per well in a volume of 200 pL of complete growth medium. Different dosages (ranging from 0.12 to 60 pM) of the compound of Example 1 were added in a volume of 90 pL, or 45 pL mixed with 45 pL of PgP inhibitor (20 pM, 2x concentration) for 15 mins at 37 C. SARS-CoV-2 strain from virus production tittered, was add in the volume of 10 pL the equivalent of 0.01 multiplicity of infection. The cells in the presence of virus and example compound were grown for 48 hours at 37 C. They were then processed with an MTS assay, in which 20 pL of MTS / PMS solution was added directly according to manufacture protocol (CellTiter96). This provided a colorimetric method of determining the number of viable cells based on absorbance at 492 nm of formazan, directly proportional to the number of living cells in the well.

[0252] The Example compound was shown to provide excellent inhibition of virus infection in this study. Extremely high antiviral potency was also demonstrated when tested with P-gp inhibitor.

[0253] Ritonavir co-administration study

[0254] Compounds of the present invention were tested when co-administered with CYP3A4 inhibitor, ritonavir.

[0255] Three dosage groups, each of three Sprague Dawley rats, of approximately 250- 300g weight were administered the compound of Example 1 under fed conditions according to the dosages below.

[0256] Dosage group 1 - Example 1 compound (1 mg / kg), intravenous injection.

[0257] Dosage group 2 - Example 1 compound (10 mg / kg), oral administration.

[0258] Dosage group 3 - Example 1 compound (10 mg / kg) and ritonavir (20 mg / kg), oral administration.

[0259] The IV dosing solution was 0.5 mg / ml in 30:70 PEG400:water. The PO dosing solution for Example 1 compound in the absence of Ritonavir was 2 mg / ml in 5:60:35 DMSO:PEG400:water. The PO dosing solution for co-administration with ritonavir was 2mg / ml in the same vehicle, with ritonavir at 4 mg / ml.

[0260] Serial blood samples (-250 pL) from the jugular vein cannulation of individual animals were taken at specific time points and delivered into labelled polypropylene tubes containing anticoagulant (heparin) and held on wet ice for a maximum of 30 minutes. The blood samples were centrifuged for plasma (4C, 21100 g for 5 min) and the resulting plasma was transferred into labelled safe-lock Eppendorf 1 .5 mL clear tubes.

[0261] Plasma samples were taken at the following time points:

[0262] For IV administration: Pre-dose, 2, 5, 15, 30 min and 1 , 2, 4, 8 & 24 h.

[0263] For PO administration Pre-dose, 5, 15, 30 min and 1 , 2, 4, 8 & 24 h.

[0264] The mean plasma concentrations of the compound of Example 1 for each dosage group are shown in Fig. 1. Tmax, Cmax and AUC for the orally administered example compound with and without ritonavir are provided in Table 3 below. PK parameters were estimated by non-compartmental model using Excel.

[0265] Table 3

[0266] The maximum concentration (Cmax) and area under curve (AUC) were significantly higher (3.9 times and 5.3 times higher respectively), for the compound when orally administered with ritonavir, compared with oral administration alone. Thus, the compounds of the present invention may advantageously be administered together with a CYP3A4 inhibitor such as ritonavir.

[0267] The following are non-limiting numbered embodiments.

[0268] Embodiment 1. A compound of Formula (I) or a pharmaceutically acceptable salt, solvate, hydrate, N-oxide and / or prodrug thereof, wherein

[0269] R1and R1aare independently H, or a group selected from C1-6 alkyl, C3-6 cycloalkyl, and benzyl, each of which is optionally substituted with one or more halo, preferably fluoro; or R1and R1aare linked, together with the nitrogen to which they are attached, to form a 3- to 6-membered saturated heterocyclyl comprising 1 or 2 heteroatoms and optionally substituted with one or more halo, preferably fluoro;

[0270] R2is selected from the group consisting of a C1-4 alkyl, C3-6 cycloalkyl, 3- to 6-membered heterocyclyl, -(CH2)PC(O)NHR9, and -(CH2)PCO2R9, wherein each C1-4 alkyl, C3-6 cycloalkyl, and 3- to 6-membered saturated heterocyclyl, is optionally substituted with one or more groups selected from oxo, hydroxy and halo; p is 0, 1 , 2, or 3;

[0271] R3is selected from the group consisting of

[0272] (i) C1-6 alkyl or C3-6 cycloalkyl;

[0273] (ii) a 3- to 6-membered saturated heterocyclyl wherein the heteroatom is oxygen or nitrogen; and

[0274] (iii) -CH2phenyl; -CH(CH3)phenyl; or -C(CH3)2phenyl; any of groups (i) to (iii) being optionally substituted with one or more groups selected from halo, hydroxy and methoxy;

[0275] R4is selected from the group consisting of C1-8 alkyl, C2-8 alkenyl, and C3- 8 cycloalkyl, each of which is optionally substituted with one or more groups selected from halo, hydroxy, and methoxy;

[0276] R5is selected from the group consisting of C1-6 alkyl, C2-6 alkenyl, and C3- 6 cycloalkyl, each of which is optionally substituted with one or more groups selected from halo, hydroxy, and methoxy;

[0277] R6is H, or a group selected from C1-6 alkyl and C3-4 cycloalkyl, which groups are optionally substituted with one or more groups selected from halo, hydroxy and methoxy; and

[0278] R7, R8and R9are independently selected from H and C1-3 alkyl optionally substituted with one or more halo.

[0279] Embodiment 2. The compound according to Embodiment 1 , wherein the compound is of Formula (IA) or a salt, solvate, hydrate, N-oxide or prodrug thereof, wherein the substituents are as defined in Embodiment 1.

[0280] Embodiment 3. The compound according to any preceding Embodiment, wherein (i) R1is H, or a group selected from C1-4 alkyl, C3-5 cycloalkyl, or benzyl each of which is optionally substituted with one or more halo, preferably fluoro; and R1ais selected from H and C1-3 alkyl; or

[0281] (ii) wherein R1and R1aare linked, together with the nitrogen to which they are attached, to form an aziridinyl or azetidinyl ring optionally substituted with one or more halo, preferably fluoro.

[0282] Embodiment 4. The compound according to Embodiment 3, wherein R1is H, or a group selected from the group consisting of methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, sec-butyl, isobutyl, tert-butyl, cyclobutyl, benzyl which groups are each optionally substituted with one or more fluoro; and R1ais H or methyl, preferably H; or wherein R1and R1aare linked, together with the nitrogen to which they are attached, to form an aziridinyl or azetidinyl ring, which are optionally substituted with one or more fluoro.

[0283] Embodiment 5. The compound according to Embodiment 4, wherein R1is H or a group selected from methyl, ethyl, propyl, isopropyl, cyclopropyl, tert-butyl, cyclobutyl, preferably cyclopropyl which groups are each optionally substituted with one or more fluoro; and wherein R1ais H or methyl, preferably H.

[0284] Embodiment 6. The compound according to any preceding Embodiment, wherein R2is C3-6 cycloalkyl, or a 4- to 6- membered heterocyclic ring, optionally substituted with one or more groups selected from oxo, hydroxy and halo. Embodiment 7. The compound according to Embodiment 6, wherein R2is a saturated 5- or 6-membered heterocyclic ring comprising a nitrogen heteroatom, said ring being optionally substituted with one to three groups selected from oxo, hydroxy and halo.

[0285] Embodiment 8. The compound according to Embodiment 7, wherein R2is selected from the group consisting of each of which is optionally substituted with one or more halo, preferably fluoro; preferably wherein

[0286] Embodiment 9. The compound according to any preceding Embodiment, wherein R3is selected from the group consisting of each of which are optionally substituted with one or more halo, preferably fluoro.

[0287] Embodiment 10. The compound according to Embodiment 9, wherein R3is cyclopropyl, iso-propyl, sec-butyl or tert-butyl, preferably tert-butyl.

[0288] Embodiment 11. The compound according to any preceding Embodiment, wherein R5is selected from the group consisting of C1-4 alkyl, which groups are optionally substituted with one or more halo, preferably fluoro. Embodiment 12. The compound according to Embodiment 11 , wherein R5is selected from the group consisting of: -CF3, -CH3, -CH2F, -CHF2, 5^

[0289] Embodiment 13. The compound according to Embodiment 12, wherein R5is -CF3, preferably -CF3.

[0290] Embodiment 14. The compound according to any preceding Embodiment, wherein R4is -CH2-X, wherein X is C1-5 alkyl, C3-s cycloalkyl, or C3-s alkenyl, which groups may be optionally substituted with one or more groups selected from halo, hydroxy, and methoxy.

[0291] Embodiment 15. The compound according to any preceding Embodiment, wherein R4is selected from the group consisting of one or more one or more groups selected from halo, hydroxy and methoxy, preferably fluoro; preferably wherein R4is selected from which are optionally substituted with one or more fluoro; most preferably wherein

[0292] Embodiment 16. The compound according to any preceding Embodiment, wherein R6is selected from H or Ci-3alkyl optionally substituted with one or more halo; preferably wherein R6is selected from H or methyl. Embodiment 17. The compound of Embodiment 1 , wherein the compound is selected from the group consisting of

[0293] • (2S)-A / -(4-(cyclopropylamino)-3,4-dioxo-1-((S)-2-oxopyrrolidin-3-yl)butan-2- yl)-4,4-dimethyl-2-((S)-A / ,3,3-trimethyl-2-(2,2,2- trifluoroacetamido)butanamido)pentanamide

[0294] • (2S)-A / -(4-(cyclopropylamino)-3,4-dioxo-1-((S)-2-oxopyrrolidin-3-yl)butan-2- yl)-2-((S)-3,3-dimethyl-2-(2,2,2-trifluoroacetamido)butanamido)-4,4- dimethylpentanamide or salt, solvate, hydrate, N-oxide or prodrug thereof.

[0295] Embodiment 18. A pharmaceutical composition comprising a compound as defined in any preceding Embodiment, and a pharmaceutically acceptable excipient.

[0296] Embodiment 19. A compound as defined in any one of Embodiments 1 to 17, or a pharmaceutical composition as defined in Embodiment 18, for use as a medicament.

[0297] Embodiment 20. A compound as defined in any one of Embodiments 1 to 17, or a pharmaceutical composition as defined in Embodiment 18, for use in the treatment of SARS-CoV-2 or in the treatment of disorders associated with SARS-CoV-2.

[0298] Embodiment 21 . Use of a compound as defined in any one of Embodiments 1 to 17 in the manufacture of a medicament for the treatment of SARS-CoV-2 or a disorder associated with SARS-CoV-2.

[0299] Embodiment 22. A method of treating a disease or disorder susceptible to SARS- CoV-2 Mpro inhibition in a subject in need thereof, said method comprising administering to said subject a pharmaceutically effective amount of a compound as defined in any one of Embodiments 1 to 17, or a pharmaceutical composition according to Embodiment 18. Embodiment 23. A method of treating SARS-CoV-2, or a disorder associated with SARS-CoV-2, in a subject in need thereof, said method comprising administering to said subject a pharmaceutically effective amount of the compound as defined in any one of Embodiments 1 to 17, or a pharmaceutical composition according to Embodiment 18.

Claims

1. CLAIMSor a pharmaceutically acceptable salt, solvate, hydrate, N-oxide and / or prodrug thereof, whereinR1and R1aare independently H, or a group selected from C1-6 alkyl, C3-6 cycloalkyl, and benzyl, each of which is optionally substituted with one or more halo, preferably fluoro; or R1and R1aare linked, together with the nitrogen to which they are attached, to form a 3- to 6-membered saturated heterocyclyl comprising 1 or 2 heteroatoms and optionally substituted with one or more halo, preferably fluoro;R2is selected from the group consisting ofeach of which is optionally substituted with one or more halo;R3is selected from the group consisting of(i) C1-6 alkyl or C3-6 cycloalkyl;(ii) a 3- to 6-membered saturated heterocyclyl wherein the heteroatom is oxygen or nitrogen; and(iii) -CH2phenyl; -CH(CH3)phenyl; or -C(CH3)2phenyl; any of groups (i) to (iii) being optionally substituted with one or more groups selected from halo, hydroxy and methoxy;R4is selected from the group consisting of C1-8 alkyl, C2-8 alkenyl, and C3-8 cycloalkyl, each of which is optionally substituted with one or more groups selected from halo, hydroxy, and methoxy;R5is selected from the group consisting of -CF3, -CH3, -CH2F, -CHF2,R6is H, or a group selected from C1-6 alkyl and C3-4 cycloalkyl, which groups are optionally substituted with one or more groups selected from halo, hydroxy and methoxy; andR7, R8and R9are independently selected from H and Ci-3alkyl optionally substituted with one or more halo.

2. The compound according to claim 1 , wherein the compound is of Formula(IA)or a salt, solvate, hydrate, N-oxide or prodrug thereof, wherein the substituents are as defined in claim 1 .

3. The compound as claimed in claim 1 or claim 2, wherein(i) R1is H, or a group selected from C1-4 alkyl, C3-5 cycloalkyl, and benzyl each of which is optionally substituted with one or more halo, preferably fluoro; andR1ais selected from H and C1-3 alkyl; or(ii) R1and R1aare linked, together with the nitrogen to which they are attached, to form an aziridinyl or azetidinyl ring optionally substituted with one or more halo, preferably fluoro.

4. The compound according to claim 3, wherein(i) R1is H, or a group selected from methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, sec-butyl, isobutyl, tert-butyl, cyclobutyl,benzyl which groups are each optionally substituted with one or more fluoro; andR1ais H or methyl, preferably H; or(ii) R1and R1aare linked, together with the nitrogen to which they are attached, to form an aziridinyl or azetidinyl ring, which are optionally substituted with one or more fluoro.

5. The compound according to claim 4, wherein R1is H or a group selected from methyl, ethyl, propyl, isopropyl, cyclopropyl, tert-butyl, cyclobutyl, -cyclopropyl, which groups are each optionally substituted with one or more fluoro; and R1ais H or methyl, preferably H.

6. The compound as claimed in any preceding claim, wherein R2is selected from the group consisting ofeach of which is optionally substituted with one or more fluoro; preferably wherein7. The compound as claimed in any preceding claim, wherein R3is selected from the group consisting ofeach of which are optionally substituted with one or more halo, preferably fluoro.

8. The compound according to claim 7, wherein R3is cyclopropyl, isopropyl, sec-butyl or tert-butyl, preferably tert-butyl.

9. The compound as claimed in any preceding claim, wherein R5is -CF3,-CH3, -CH2F, -CHF2, ,1 or, preferably -CF3, A A or A ■’ , more preferably -CF3.

10. The compound as claimed in any preceding claim, wherein R4is -CH2-X, wherein X is C1-5 alkyl, C3-s cycloalkyl, or C3-s alkenyl, which groups may be optionally substituted with one or more groups selected from halo, hydroxy, and methoxy.11 . The compound as claimed in any preceding claim, wherein R4is selected from the group consisting ofor more one or more groups selected from halo, hydroxy and methoxy, preferably fluoro; preferably wherein R4iswhich are optionally substituted with one or more fluoro; most preferably wherein R4is12. The compound as claimed in any preceding claim, wherein R6is selected from H and C1-3 alkyl optionally substituted with one or more halo; preferably wherein R6is selected from H or methyl.

13. The compound as claimed in claim 1 , wherein the compound is selected from the group consisting of• (2S)- / -(4-(cyclopropylamino)-3,4-dioxo-1-((S)-2-oxopyrrolidin-3-yl)butan-2- yl)-4,4-dimethyl-2-((S)-A / ,3,3-trimethyl-2-(2,2,2- trifluoroacetamido)butanamido)pentanamide• (2S)-A / -(4-(cyclopropylamino)-3,4-dioxo-1-((S)-2-oxopyrrolidin-3-yl)butan-2- yl)-2-((S)-3,3-dimethyl-2-(2,2,2-trifluoroacetamido)butanamido)-4,4- dimethylpentanamide or salt, solvate, hydrate, N-oxide or prodrug thereof.

14. A pharmaceutical composition comprising a compound as defined in any preceding claim, and a pharmaceutically acceptable excipient.

15. A compound as defined in any one of claims 1 to 13, or a pharmaceutical composition as defined in claim 14, for use as a medicament.

16. A compound as defined in any one of claims 1 to 13, or a pharmaceutical composition as defined in claim 14, for use in the treatment of SARS-CoV-2 or in the treatment of disorders associated with SARS-CoV-2.

17. Use of a compound as defined in any one of claims 1 to 13 in the manufacture of a medicament for the treatment of SARS-CoV-2 or a disorder associated with SARS-CoV-2.

18. A method of treating a disease or disorder susceptible to SARS-CoV-2 Mpro inhibition in a subject in need thereof, said method comprising administering to said subject a pharmaceutically effective amount of a compound as defined in any one of claims 1 to 13, or a pharmaceutical composition according to claim 14.

19. A method of treating SARS-CoV-2, or a disorder associated with SARS- CoV-2, in a subject in need thereof, said method comprising administering to said subject a pharmaceutically effective amount of the compound as defined in any one of claims 1 to 13, or a pharmaceutical composition according to claim 14.

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