The isoforms hCA I, II, IV, IX, XII were effectively and sometimes selectively inhibited by such derivatives, with efficacies in the nanomolar range, whereas the pain-relieving properties of several hybrids were also assessed in an animal model of rheumatoid arthritis (RA), by using the paw-pressure and incapacitance tests, which demonstrated an efficacy similar or slightly better than that of the clinically used drug ibuprofen, belonging to the cyclooxygenase (COX) inhibitors.48 Here, CYP24A1 is linked to rheumatoid arthritis.