Phase II study of sodium valproate in combination with oral etoposide in platinum-resistant ovarian cancer

Abstract Background: Patients with platinum-resistant ovarian cancer (PROC) have limited therapeutic options and poor survival. There is a need for the development of newer therapies. Sodium valproic acid (VPA) is a short-chain fatty acid histone deacetylase (HDAC) inhibitor with antitumor activity in preclinical models of PROC. Synergism with conventional cytotoxic agents like etoposide has been demonstrated. Methodology: In this prospective, single-arm, open-label, phase 2 study, we included patients ≥18 years with histologically or cytologically confirmed PROC and Eastern Cooperative Oncology Group performance status (ECOG-PS) 0-3. Patients received oral VPA 60 mg/kg/day in three divided doses for three days (D1-D3), followed by oral etoposide 50 mg once daily for two consecutive weeks (D4-D17). Serum samples were collected to assess peak VPA drug levels. The primary endpoint was the overall response rate (ORR). The secondary endpoints were progression-free survival (PFS), overall survival (OS), and toxicity. We sought to show an improvement in response rate from 25% (historically with oral etoposide) to 40% with the addition of VPA. Results: 27 patients were enrolled in the study, and 18 [median age: 52 (45-59) years; serous histology:17(94%); ECOG-PS 2 or 3: 14 (78%)] were evaluable for the response after four months. Nine patients were lost from follow-up before achieving the primary endpoint (mainly due to Covid-related lockdown issues). The median number of prior lines of treatment was 2 (1-3). ORR was 0% according to GCIG criteria. The disease was stable in two patients [clinical benefit rate (CBR) of 11%]. The median OS and PFS were seven months and two months, respectively. Grade ≥3 adverse events were reported in 6 (33%) patients. Conclusion: The addition of valproic acid to oral etoposide in patients with PROC and poor general condition was not helpful and failed to improve responses compared to those historically achieved with single-agent etoposide.