A compound of Formula Ia: ** Formula ** or a pharmaceutically acceptable salt thereof, wherein: R10 is represented by formula 2: - (alkylene of 0 to 3 carbon atoms) -BX- (CR11aR12a) m- ( CR11bR12b) n- (CR11cR12c) pC (O) OR13, wherein the alkylene groups are optionally substituted by one or more Z groups； B is ariIo optionally substituted by one or more Z groups； X is selected from a link, -NR15 (SO2) -, - (SO2) NR15-, - (SO2) -, -NR15C (O) -, -C (O) NR15-, -NR15C (O) NR17 -, - NR15C (O) O-, -NR15 -, C (O) O, OC (O), C (O), O and S； R11a, R11b, R11c, R12a, R12b and R12c are each independently selected from H and alkyl of 1 to 6 carbon atoms； or R11a and R12a together with the carbon atom to which they are attached, form a 3- to 8-membered cycloalkyl group； or R11b and R12b together with the carbon atom to which they are attached, form a 3- to 8-membered cycloalkyl group； or R11c and R12c together with the carbon atom to which they are attached, form a 3- to 8-membered cycloalkyl group； R13 is selected from (alkyl of 1 to 3 carbon atoms) -C (O) NR22R23； and (alkyl of 1 to 3 carbon atoms) -C (O) OR23； and (alkyl of 1 to 3 carbon atoms) -NR23C (O) R22 R15 and R17 are each independently selected from H and alkyl of 1 to 6 carbon atoms； Z is independently selected from -OH, aryl, -O-aryl, aralkyl of 7 to 14 carbon atoms, -O aralkyl of 7 to 14 carbon atoms, alkyl of 1 to 6 carbon atoms, alkoxy of 1 to 6 carbon atoms, - NR19 (SO2) R21, - (SO2) NR19R21, - (SO2) R20, -NR19C (O) R20, -C (O) NR19R20, -NR19C (O) NR20R18, -NR19C (O) OR20, - NR19R21, C (O) OR19, -C (O) R19, SR19, -OR19, oxo, CN, NO2, and halogen, wherein the alkyl, alkoxy, aralkyl and aryl groups are each optionally substituted by one or more substituents selected from OH, halogen, haloalkyl of 1 to 4 carbon atoms and alkoxy of 1 to 4 carbon atoms； R18, R20 and R22 are each independently selected from H and alkyl of 1 to 6 carbon atoms； R19, R21 and R23 are each independently selected from H； alkyl of 1 to 8 carbo
