Purpose: Recent data indicate that there is a significant cross-talk between the PI3K/Akt/mTOR and androgen receptor signaling pathways. We evaluated safety and tolerability as well as potential drug-drug interaction of ridaforolimus, a mammalian target of rapamycin (mTOR) inhibitor, when combined with the androgen receptor inhibitor bicalutamide in patients with asymptomatic, metastatic castration-resistant prostate cancer. Patients and methods: Patients were treated with the combination of ridaforolimus 30 mg/day for 5 consecutive days each week and bicalutamide 50 mg/day. Ridaforolimus pharmacokinetics was assessed with and without bicalutamide. Results: Twelve patients were enrolled including 1 screen failure. Dose reductions were required in 7 patients. Three of the 11 patients experienced a dose-limited toxicity, 1 with Grade 3 hyperglycemia and 2 with Grade 2 stomatitis leading to <75 % of planned ridaforolimus dose during the first 35 days of study treatment. The pharmacokinetic results showed no differences in exposures to ridaforolimus with and without concomitant bicalutamide administration. Conclusions: Although there was no evidence of a clinically relevant pharmacological drug-drug interaction, the occurrence of dose-limiting toxicities in 3 of 11 evaluable patients at a reduced dose of ridaforolimus of 30 mg/day suggests that this combination may not be well suited for asymptomatic or minimally symptomatic prostate cancer patients.

Androgen receptor inhibitor, Bicalutamide, Castration-resistant prostate cancer, mTOR inhibitor, Pharmacokinetics, Ridaforolimus
dx.doi.org/10.1007/s00280-013-2250-6, hdl.handle.net/1765/65072
Cancer Chemotherapy and Pharmacology
Department of Medical Oncology

Meulenbeld, H.J, de Bono, J.S, Tagawa, S.T, Whang, Y-J, Li, X, Heath, K.H, … de Wit, R. (2013). Tolerability, safety and pharmacokinetics of ridaforolimus in combination with bicalutamide in patients with asymptomatic, metastatic castration-resistant prostate cancer (CRPC). Cancer Chemotherapy and Pharmacology, 72(4), 909–916. doi:10.1007/s00280-013-2250-6