CNC(=O)CN1CC(C(=O)Nc2cncc3cccc(C(F)F)c23)c2cc(Cl)ccc2C1=O
CNC(=O)CN1CC(C(=O)Nc2cncc3cccc(Br)c23)c2cc(Cl)ccc2C1=O
CNC(=O)CN1Cc2ccc(Cl)cc2C(C(=O)Nc2cncc3cccc(C(F)F)c23)C1
CNC(=O)CN1Cc2ccc(Cl)cc2C(C(=O)Nc2cncc3cccc(Br)c23)C1
O=C(Cc1cccc(Cl)c1)Nc1cncc2cccc(C(F)F)c12
O=C(Cc1cccc(Cl)c1)Nc1cncc2cccc(Br)c12
Peri-chloro substituent increases activity a bit, peri-methyl increases activity a bit more, but presumably is a metabolic weak spot, peri-trifluoromethyl wasn't selected for synthesis, maybe something like this will work better