Combined Autophagy and Proteasome Inhibition for Multiple Myeloma: Final Results of a Phase 1 Trial of Hydroxychloroquine and Standard Dose Bortezomib for Patients with Relapsed or Refractory Myeloma

The aggresome/autophagy pathway is the primary mechanism for disposal of ubiquitinated proteins for cells exposed to proteasome inhibition. Preclinical evidence shows that combining inhibition of the proteasome with bortezomib (Bz) and inhibition of autophagy with the anti-malarial drug hydroxychloroquine (HCQ) leads to enhanced cytotoxicity in myeloma cells.

Patients with relapsed or refractory myeloma enrolled on a standard 3+3 dose escalation design. Patients received 2-weeks of single-agent oral HCQ, followed by the addition of Bz on days 1, 4, 8, and 11 of 21-day cycles. HCQ and Bz doses were determined by dose level: (1) 200 mg qod / 1.0 mg/m², (2) 200 qod / 1.3, (3) 200 qd / 1.3, (4) 200 bid / 1.3, (5) 400 bid / 1.3, (6) 600 bid / 1.3. Dose-limiting toxicity (DLT) was defined as grade ≥3 toxicity probably related to study therapy and occurring during the first 5 weeks, with the exception of any anemia or lymphopenia, neutropenia responsive to growth factor, platelets >10,000/mm³ not associated with bleeding, or gastrointestinal complaints relieved by symptomatic therapy. We used electron microscopy to characterize changes in autophagic vesicles in serial samples of peripheral blood mononuclear cells and CD138-selected bone marrow plasma cells.

We enrolled 25 patients between 1/2008 and 2/2011, of which 21 patients completed at least 1 cycle of combined therapy and were evaluable for toxicity. The median duration of study participation was 14 weeks (range 1–77). Reasons for study discontinuation were side effects of therapy (6), lack of response (7), disease progression (11), and non-compliance (1). No protocol-defined dose limiting toxicities occurred, and the maximum tolerated dose was determined to be the top dose level of Bz 1.3 mg/m2 and HCQ 600 mg twice daily. Hematologic abnormalities were generally more attributable to disease progression than to treatment toxicity, but at the top dose level one patient had grade 3 thrombocytopenia and neutropenia after starting with a normal platelet count and ANC, without evidence of progression through therapy. At the top dose level, gastrointestinal toxicities predominated, including 5 out of 6 evaluable patients with some form of grade 3 GI toxicity. Treatment emergent neuropathy occurred in 7 patients but was restricted to grade 1 or 2 and was easily managed with dose reduction of the Velcade. Three patients came off study before receiving the combined regimen and were not evaluable for response. The best responses for the remaining 22 patients included 3 near complete responses (nCR), 3 minor responses (MR), 9 stable disease (SD), and 7 progression (PD). The 3 nCRs occurred in Bz-naïve patients receiving HCQ at 400 mg/d (1 pt) and 1200 mg/d (2 pts). Two patients who had previously progressed while receiving weekly maintenance Bz had MRs on study, including one who maintained a MR for over 7 months. Three additional Bz-refractory patients initially achieved stable disease during study treatment, with on study TTP of 8 weeks (at HCQ 1200 mg/d), 15 weeks (100 mg/d), and 17 weeks (200 mg/d). Preliminary analyses of vesicle counts at HCQ doses up to 800 mg/d identify individual patients with increases in autophagic vesicles in either peripheral blood or bone marrow plasma cells, but these are not consistent, nor is there any evident correlation with response.

Combined Bz and HCQ is tolerable, with a phase 2 dose of Bz 1.3 mg/m2 and HCQ 1200 mg/d and likely hematologic and gastrointestinal DLTs. There is a suggestion of improved efficacy over Bz alone, with minor responses and long periods of stable disease in Bz-refractory patients. Final analysis of autophagy inhibition in correlative specimens, including the top dose cohort, will be available for the meeting.

Vogl:Millennium Pharmaceuticals: Honoraria, Research Funding. Off Label Use: Hydroxychloroquine is FDA approved for treatment of malaria and rheumatoid arthritis. This paper discusses its use in treatment of myeloma. Carroll:Agios Pharmaceuticals: Research Funding; TetraLogic Pharmaceuticals: Research Funding; Sanofi Aventis Corporation: Research Funding; Glaxo Smith Kline, Inc.: Research Funding. Amaravadi:Millennium Pharmaceuticals: Honoraria, Research Funding.