Aims: To evaluate the effect of the combination of carotegrast methyl with rifampicin, a potent inhibitor of organic anion transporter polypeptide, on the pharmacokinetics (PK), safety and tolerability. Methods: In this 2 x 2 crossover study in 20 healthy Japanese adults, 10 subjects received carotegrast methyl 960 mg and rifampicin 600 mg on day 1, and received carotegrast methyl 960 mg on day 8. The subjects in the other sequence received the same treatments but in the opposite order. When the 90% confidence interval (CI) of the geometric mean ratio of the AUC0-t and Cmax for carotegrast, the main active metabolite of carotegrast methyl, with/without rifampicin fell within the range of 0.80 – 1.25, it was deemed that no PK interaction occurred. Adverse events (AEs) were monitored. Results: The Cmax and AUC0-t for carotegrast with/without rifampicin was 11724.5 ± 6097.6 vs 2620.1 ± 1843.0 ng mL-1, and 55046.0 ± 23427.8 vs 9849.9 ± 4580.6 ng h mL-1, respectively. The ratios (90% CI) of the Cmax and AUC0-t with/without rifampicin were 4.78 (3.64 – 6.29) and 5.59 (4.60 – 6.79), respectively, indicating carotegrast has a PK interaction with rifampicin. The combination with rifampicin also increased the exposure of carotegrast and its metabolites. The incidence of any AEs with/without rifampicin was five (25.0%) and one (5.0%), respectively. Conclusion: Coadministration of carotegrast methyl with rifampicin significantly increased exposure of carotegrast compared with carotegrast methyl administration alone. However, no increase in the incidence of adverse drug reactions due to coadministration with rifampicin was observed.

Aims: To evaluate drug-drug interactions between carotegrast methyl, a CYP3A4 inhibitor, and other CYP3A4 substrates, midazolam, atorvastatin, and prednisolone. Methods: A total of 88 healthy volunteers orally received carotegrast methyl 960 mg three times daily for 14 days. A single oral (5 mg) or intravenous (0.017 mg kg-1) midazolam, oral (5 mg) prednisolone, or oral (10 mg) atorvastatin was administered before, with, and after carotegrast methyl treatment. When the 90% confidence interval (CI) for the geometric mean ratios of the pharmacokinetic (PK) parameters with coadministration with carotegrast methyl (day 14) to those before carotegrast methyl administration was between 0.80 and 1.25, no PK interaction were deemed. Results: The Cmax and AUC0-t of oral midazolam before administration of carotegrast methyl was 30.9 ± 9.8 ng mL-1 and 74.5 ± 21.9 ng h mL-1, respectively. The geometric mean ratio of the Cmax and AUC0-t of midazolam on day 14 to those on day -1 was 1.86 (90% CI, 1.64 – 2.11) and 3.07 (90% CI, 2.81 – 3.35), which did not fall within the range of 0.80 – 1.25, suggesting that carotegrast methyl had a PK interaction with midazolam. Similar PK interactions were found for intravenous midazolam and atorvastatin, but not for prednisolone. The inhibitory effect of carotegrast methyl on CYP3A4-mediated metabolism of midazolam and atorvastatin had almost disappeared by 14 days after the end of administration. Conclusion: Carotegrast methyl was classified as a moderate CYP3A4 inhibitor in humans. Carotegrast methyl might enhance the action of drugs that are metabolized by CYP3A4.