Phase I Trial of Oral Vorinostat (Suberoylanilide Hydroxamic Acid, SAHA) in Combination with Bortezomib in Patients with Advanced Multiple Myeloma.

Background: Vorinostat is a histone deacetylase inhibitor that has demonstrated antiproliferative and proapoptotic activity alone and in combination with the proteasome inhibitor bortezomib in preclinical multiple myeloma (MM) models. In a Phase I study, vorinostat also demonstrated modest single agent activity in patients (pts) with relapsed or refractory MM.

Patients and Methods: We conducted a Phase I trial of oral vorinostat (200 mg bid or 400 mg daily × 14 days (d1–14) in combination with bortezomib 0.7 or 0.9 mg/m² i.v. on d 4, 8, 11 and 15 or 0.9, 1.1, or 1.3 mg/m² i.v. on d 1, 4, 8 and 11. Cycles were repeated every 21 d for a maximum of 8 cycles until progressive disease (PD) or intolerable toxicity. Pts with active relapsed or refractory MM who had not received bortezomib in the preceding 3 months and with adequate hematologic, hepatic, and renal function, and ECOG performance status of 0–2 were eligible. The primary objective was to determine the maximum tolerated dose (MTD). Activity (utilizing EBMT criteria) and safety of the combination regimen were also assessed.

Results: Twenty pts have been enrolled: median age, 61 years (range 52–76), median number prior systemic therapies, 3 (range 1–14), prior therapy with bortezomib (4 pts). Eighteen pts have received ≥ 1 dose and were evaluable for safety as of 7/1/07. One pt (cohort 3) experienced a dose-limiting toxicity (DLT, Table). The MTD has not been reached. The most common drug-related toxicities of any grade were nausea (56%), thrombocytopenia (50%), diarrhea (39%), vomiting (39%), fatigue (39%), and anemia (22%). Grade ≥ 3 drug-related adverse events were thrombocytopenia (33%, none associated with bleeding), peripheral neuropathy (11%), neutropenia (11%, none associated with fever), diarrhea (6%), diverticulitis (6%), fatigue (6%), increased AST (6%), memory changes (6%), nausea (6%), vomiting (6%), and upper respiratory infection (6%). Eight pts discontinued treatment, 3 due to PD and 5 due to adverse experiences [fatigue (2), nausea (2), diverticulitis (1)]. Of 17 evaluable pts for efficacy, all had measurable response or stable disease; 4 had a partial response, 2 had a minimal response, and 11 stable disease. Among 3 evaluable pts previously treated with bortezomib, 1 achieved a partial response and 1, minimal response. Pts at the highest dose level were not yet evaluable for response.

Conclusion: Although accrual continues to determine the MTD, the combination of vorinostat and bortezomib is well tolerated and effective in this group of heavily pretreated pts with refractory/relapsed MM.