A Phase II Study of Elotuzumab in Combination with Pomalidomide, Bortezomib, and Dexamethasone in Relapsed and Refractory Multiple Myeloma

Background

Elotuzumab is an approved monoclonal antibody targeting SLAMF7 on plasma and NK cells that enhances the activity of lenalidomide, pomalidomide, and bortezomib in multiple myeloma (MM). A recent study showed improved outcomes with the combination of pomalidomide, bortezomib, and dexamethasone vs. bortezomib and dexamethasone in relapsed or refractory MM (Richardson PG et al., Lancet Oncol 2019). We therefore studied elotuzumab with pomalidomide, bortezomib, and dexamethasone (elo-PVD) in relapsed and refractory MM.

Methods

The primary objective was to determine the overall response rate (ORR). Patients with relapsed and refractory disease and ≥1 prior lines of treatment (including lenalidomide and a proteasome inhibitor) were eligible to participate. Prior treatment with pomalidomide was permitted. Elotuzumab was weekly for the first 2 cycles and then every other week. Pomalidomide was given on days 1-21; bortezomib was on days 1, 8, 15; and dexamethasone was weekly. Each cycle was 28 days.

Results

The trial has completed accrual in September 2018 with 48 patients receiving treatment. The median age was 64 (range 40-80), and median number of prior regimens was 3 (range 1-9); 25% had high risk FISH. All patients had prior lenalidomide and proteasome inhibitor (bortezomib 96%, 29% carfilzomib) and were refractory to their last line of therapy. Other prior therapies included: autologous stem cell transplant (48%), pomalidomide (33%), daratumumab (25%), and isatuximab (4%). 46 patients were assessable for response (2 patients did not complete cycle 1 and were not evaluable for response: 1 due to rapid disease progression; 1 stroke. The median length of follow up was 18.8 months (range 0.5-23.4): 16 patients continue on study; 27 patients discontinued for progressive disease; 3 patients discontinued for adverse events (AEs) (sepsis, pneumonia, stroke); 1 patient underwent auto SCT; and 1 patient was lost to follow up. Best ORR was 61% (PR = 16, VGPR = 10, CR = 2). ORR for patients with prior anti-CD38 antibody, 46%; carfilzomib, 46%; pomalidomide, 43%. Median PFS was 9.8 months (95% CI 6.8-Inf). In patients with 1 prior line of therapy, ORR was 74% and median PFS was not reached (95% CI 12-Inf); 18 month PFS was 68%. Grade ≥ 3 hematologic AEs included anemia (10%), neutropenia (29%), and thrombocytopenia (15%). Additional common grade ≥ 3 AEs included lung infection (27%) and hypophosphatemia (15%). Common non-hematologic AEs all grades included fatigue (grade 1-2 only, 70%), upper respiratory infection (grade 1-2, 56%; grade 3, 2%), diarrhea (grade 1-2 only, 42%), constipation (grade 1-2 only, 35%), hyperglycemia (grade 1-2, 46%; grade 3, 4%), and sensory neuropathy (grade 1-2 only, 31%), with 2 possibly related deaths (sepsis, pneumonia).

Conclusions

Elo-PVD is one of the first trials of a quadruplet regimen in relapsed and refractory MM incorporating a monoclonal antibody. In patients with refractory disease, elo-PVD shows encouraging responses. With the limitations of cross trial comparisons and small patient numbers, for patients with 1 prior line of treatment and refractory disease, a PFS at 18 months of 68% with elo-PVD compares favorably with a median PFS of 17.8 months in a similar subgroup of PVD in the OPTIMISMM trial (Dimopoulos MA et al., ASH 2018). Patients who received prior pomalidomide, carfilzomib, and/or anti-CD38 monoclonal antibody also benefited. Treatment was well-tolerated with manageable toxicity and with attention to infectious AEs.