wherein

Het is a monocyclic heterocyclyl, and the Het and C_1-6alkyl groups are independently optionally substituted with up to 3 groups selected from R⁴ and the C_1-6alkyl group optionally contains a double bond;

each X and X¹ is a linker independently selected from

—O-Z-, —O-Z-O-Z-, —C(O)O-Z-, —OC(O)-Z-, —S-Z-, —SO-Z-, —SO₂-Z-, —N(R⁶)-Z-, —N(R⁶)SO₂-Z-, —SO₂N(R⁶)-Z-, —CH═CH-Z-, —C≡C-Z-, —N(R⁶)CO-Z-, —CON(R⁶)-Z-, —C(O)N(R⁶)S(O)₂-Z-, —S(O)₂N(R⁶)C(O)-Z-, —C(O)-Z-, -Z-, —C(O)Z-O-Z-, —N(R⁶)—C(O)-Z-O-Z-, —O-Z-N(R⁶)-Z-, and —O—C(O)-Z-O-Z-;

each Z is independently selected from a direct bond, C_2-6alkenylene and a group of the formula

—(CH₂)_p—C(R^6a)₂—(CH₂)_q—;

each R⁴ is independently selected from halo, —CH_3-aF_a, CN, NH₂, C_1-6alkyl, —OC_1-6alkyl, —COOH, —C(O)OC_1-6alkyl, OH, phenyl optionally substituted with C_1-6alkyl or —C(O)OC_1-6alkyl, and R⁵—X¹—;

R⁵ is selected from hydrogen, C_1-6alkyl, —CH_3-aF_a, phenyl, naphthyl, heterocyclyl, and C_3-7cycloalkyl; wherein R⁵ is optionally substituted with one or more substituents independently selected from halo, C_1-6alkyl, —OC_1-6alkyl, —CH_3-aF_a, CN, OH, NH₂, COOH, and —C(O)OC_1-6alkyl;

each Z¹ is independently selected from a direct bond, C_2-6alkenylene and a group of the formula —(CH₂)_p—C(R^6a)₂—(CH₂)_q—;

R³ is heterocyclyl, wherein the atom at the two position of the heterocyclyl ring relative to the amide group, to which R³ is attached, is an sp² hybridised nitrogen; wherein R³ is optionally substituted with up to 2 R⁷ groups and wherein R³ is not pyridyl;

R⁶ is independently selected from hydrogen, C_1-6alkyl, and —C_2-4alkyl-O—C_1-4alkyl;

R^6a is independently selected from hydrogen, halo, C_1-6alkyl, and —C_2-4alkyl-O—C_1-4alkyl;

each R⁷ is independently selected from

C_1-6alkyl, C_2-6alkenyl, C_2-6alkynyl, (CH₂)_0-3aryl, (CH₂)_0-3heterocyclyl, (CH₂)_0-3C_3-7cycloalkyl, OH, C_1-6alkyl-OH, halo, C_1-6alkyl-halo, OC_1-6alkyl, (CH₂)_0-3S(O)_0-2R⁸, SH, SO₃H, thioxo, NH₂, CN, (CH₂)_0-3NHSO₂R⁸, (CH₂)_0-3COOH, (CH₂)_0-3—O—(CH₂)_0-3R⁸, (CH₂)_0-3C(O)(CH₂)_0-3R⁸, (CH₂)_0-3C(O)OR⁸, (CH₂)_0-3C(O)NH₂, (CH₂)_0-3C(O)NH(CH₂)_0-3R⁸, (CH₂)_0-3NH(CH₂)_0-3R⁸, (CH₂)_0-3NHC(O)(CH₂)_0-3R⁸; (CH₂)_0-3C(O)NHSO₂R⁸, and (CH₂)_0-3SO₂NHC(O)—R⁸; wherein any alkyl chain, cycloalkyl ring or heterocyclyl ring within R⁷ is optionally substituted with one of more substituents independently selected from C_1-4alkyl, OH, halo, CN, NH₂, N—C_1-4alkylamino, N,N-di-C_1-4alkylamino, and OC_1-4alkyl;

R⁸ is selected from hydrogen, C_1-6alkyl, aryl, heterocyclyl, C_3-7cycloalkyl, OH, C_1-6alkyl-OH, COOH, C(O)OC_1-6alkyl, N(R⁶)C_1-6alkyl, OC_1-6alkyl, C_0-6alkylOC(O)C_1-6alkyl, and C(OH)(C_1-6alkyl)C_1-6alkyl; wherein an alkyl chain or aryl, heterocyclyl or cycloalkyl ring within R⁸ is optionally substituted with one of more substituents independently selected from C_1-4alkyl, OH, halo, CN, NH₂, —NH—C_1-4alkyl, —N-di-(C_1-4alkyl) and OC_1-4alkyl;

each a is independently 1, 2, or 3;

p is independently 0, 1, 2, or 3;

q is independently 0, 1, 2, or 3;

and p+q<4;

provided that:

(i) an unbranched, unsubstituted alkyl chain cannot exceed C₆alkyl in length;

(ii) only one X group can be —NHC(O)—; and

(iii) when X is independently selected from —C(O)NH—, —NHC(O)—, —O—, —S(O₂)NH—, and a direct bond wherein one X group is —NHC(O)—, Het-Z¹ is selected from 4,5-dihydro-5-oxo-pyrazolyl, thienyl, or pyridyl and Het-Z¹ is optionally substituted with R⁴, then R³ cannot be unsubstituted thiazole, 4,5-dihydro-5-oxo-pyrazolyl substituted with trichlorophenyl, 4,5,6,7-tetrahydro-benzo[b]thiophene substituted with ethoxycarbonyl or pyridyl optionally independently mono or di-substituted with methyl, ethoxy, or propylcarbonylamino.