An Open-Label Phase I Study of Metformin and Nelfinavir in Combination With Bortezomib in Patients With Relapsed and Refractory Multiple Myeloma

A therapeutic combination of metformin, nelfinavir, and bortezomib is feasible for multiple myeloma patients with relapsed and/or refractory disease. While no dose-limiting toxicities were observed, no objective responses were observed either in the dose levels evaluated in this study. Background: In preclinical models, combining a GLUT4 inhibitor with an oxidative phosphorylation inhibitor shows synergistic therapeutic potential against multiple myeloma (MM). Thus, this study evaluated the safety and tolerability of repurposing metformin, a complex I inhibitor, and nelfinavir, a GLUT4 inhibitor, in combination with bortezomib for the treatment of relapsed/refractory MM that had progressed on all standard of care therapies. Materials and Methods: This trial utilized a 3 + 3 dose escalation design with 3 dose levels planned for up to a maximum of 6 (21-day) cycles. Metformin and nelfinavir were administered for 14 of 21 days, and subQ bortezomib was administered to a portion of patients on days 1, 8, and 15. The primary objective was to determine the maximal tolerated dose, and the secondary objective was to evaluate the safety and overall response rate (ORR) of this combination. Results: Nine patients were accrued with a median age of 65 (range: 42-81) and received a median of 7 prior lines of therapy (Range: 5-12). The first 3 patients received only metformin (500 mg BID) and nelfinavir (1250 mg BID) at the first dose level, with 1 patient experiencing an unconfirmed minimal response (MR) in the first cycle, 1 experiencing progressive disease after 1 cycle of treatment and 1 patient going off treatment prior to assessing response but with signs of progressive disease. Given the limited therapeutic activity, the upfront addition of bortezomib (1.3 mg/m2 ) was utilized for the subsequent 6 patients accrued. Three of these 6 patients went off study due to progressive disease, 1 patient achieved an unconfirmed partial response after 1 cycle of treatment but reported progressive disease in the subsequent cycle, 1 patient went off study to enter hospice, and the remaining patient experienced stable disease (SD) after receiving 6 cycles of clinical trial treatment. The study was closed before accrual to the next dose level was started. Conclusion: This is the first study to evaluate the safety and efficacy of this repurposed drug combination in this very difficult-to-treat population of relapsed and refractory MM. This was an overall negative study with no ORR observed. Fortunately, 1 patient experienced an SD response, allowing this combination to stabilize their disease until another novel therapy on a clinical trial was available.