Objective: To determine the activity and pharmacodynamics (PD) of bortezomib in platinum-sensitive epithelial ovarian or primary peritoneal cancer (EOC/PPC).
Patients and methods: Eligible women with recurrent EOC/PPC progressing between 6 and 12 months after initial chemotherapy were treated with bortezomib on days 1, 4, 8, and 11 [1.5 (cohort I) and 1.3 (cohort II) mg/m(2)/dose]. Patients must have had initial chemotherapy only. Response Evaluation Criteria in Solid Tumors (RECIST) was assessed by computed tomography (CT) scan every 2 cycles. 20S proteasome activity was quantified in three pre-treatment and a 1-hour post-treatment (cycle one, day 1) whole blood lysates.
Results: Initially, 26 evaluable patients were treated at the 1.5 mg/m(2)/dose level. Objective response rate was 3.8% (1/26), a partial response. An additional 10 patients (38.5%) had stable disease. Given concerns that treatment discontinuations due to toxicity limited drug exposure/activity a second cohort of 29 evaluable patients was accrued at 1.3 mg/m(2)/dose. The 1.3 mg/m(2)/dose regimen is currently approved as an indication for multiple myeloma and mantle cell lymphoma. Treatment was more tolerable, although objective responses remained low at 6.9% (2/29, partial responses). Second stage accrual was not warranted at either dose. Bortezomib effectively inhibited 20S proteasome activity in whole blood lysates between 37 and 92% in 24/25 (96%) patients in cohort I, and 14-84% in 27/28 (96%) patients in cohort II who provided satisfactory pre- and post-treatment specimens for testing.
Conclusion: Bortezomib has minimal activity as a single-agent in the treatment of recurrent platinum-sensitive EOC/PPC. Treatment with bortezomib at 1.5 mg/m(2)/dose was not feasible in this patient population due to excess toxicity. Bortezomib was well tolerated at 1.3 mg/m(2)/dose.