Evaluation of Drug–Drug Interactions of Rucaparib and <scp>CYP</scp>1A2, <scp>CYP</scp>2C9, <scp>CYP</scp>2C19, <scp>CYP</scp>3A, and P‐gp Substrates in Patients With an Advanced Solid Tumor

This phase I study (CO-338-044; NCT02740712), conducted in patients with advanced solid tumors, evaluated the effect of the poly(ADP-ribose) polymerase (PARP) inhibitor rucaparib on the pharmacokinetics (PK) of caffeine 200 mg, warfarin 10 mg, omeprazole 40 mg, and midazolam 2 mg (cytochrome P450 (CYP) 1A2, CYP2C9, CYP2C19, and CYP3A substrates; dosed as a cocktail) and digoxin 0.25 mg (P-glycoprotein (P-gp) substrate; dosed separately) without rucaparib and following oral rucaparib 600 mg b.i.d. Geometric mean (GM) ratios (90% confidence interval (CI)) of area under the concentration-time curve (AUC) from time zero to last quantifiable measurement with and without rucaparib were: caffeine, 2.26 (1.93-2.65); S-warfarin, 1.49 (1.40-1.58); omeprazole, 1.55 (1.32-1.83); midazolam, 1.39 (1.14-1.68); and digoxin, 1.20 (1.12-1.29). There was limited effect on peak concentration of the substrates (GM ratios, 0.99-1.13). At steady state, rucaparib 600 mg b.i.d. moderately inhibited CYP1A2, weakly inhibited CYP2C9, CYP2C19, and CYP3A, and marginally increased digoxin exposure.