A phase I study of vorinostat in combination with bortezomib in patients with advanced malignancies

Background A phase I study to assess the maximum-tolerated dose (MTD), dose-limiting toxicity (DLT), pharmacokinetics (PK) and antitumor activity of vorinostat in combination with bortezomib in patients with advanced solid tumors. Methods Patients received vorinostat orally once daily on days 1–14 and bortezomib intravenously on days 1, 4, 8 and 11 of a 21-day cycle. Starting dose (level 1) was vorinostat (400 mg) and bortezomib (0.7 mg/m²). Bortezomib dosing was increased using a standard phase I dose-escalation schema. PKs were evaluated during cycle 1. Results Twenty-three patients received 57 cycles of treatment on four dose levels ranging from bortezomib 0.7 mg/m² to 1.5 mg/m². The MTD was established at vorinostat 400 mg daily and bortezomib 1.3 mg/m². DLTs consisted of grade 3 fatigue in three patients (1 mg/m²,1.3 mg/m² and 1.5 mg/m²) and grade 3 hyponatremia in one patient (1.5 mg/m²). The most common grade 1/2 toxicities included nausea (60.9 %), fatigue (34.8 %), diaphoresis (34.8 %), anorexia (30.4 %) and constipation (26.1 %). Objective partial responses were observed in one patient with NSCLC and in one patient with treatment-refractory soft tissue sarcoma. Bortezomib did not affect the PKs of vorinostat; however, the Cmax and AUC of the acid metabolite were significantly increased on day 2 compared with day 1. Conclusions This combination was generally well-tolerated at doses that achieved clinical benefit. The MTD was established at vorinostat 400 mg daily × 14 days and bortezomib 1.3 mg/m² on days 1, 4, 8 and 11 of a 21-day cycle.