A Phase II Study of Modified Lenalidomide, Bortezomib, and Dexamethasone (RVD-lite) for Transplant-Ineligible Patients with Newly Diagnosed Multiple Myeloma

Background: Multiple myeloma (MM) is primarily a disease of older adults with median age at diagnosis of 66 years. Although melphalan and prednisone-based regimens were traditionally the most accepted treatment options, recent use of lenalidomide and dexamethasone in this older, transplant-ineligible population as presented in the FIRST trial is the new standard of care in these patients (pts) (NEJM 2014). Here, we sought a regimen that incorporates optimal novel agents in transplant-ineligible, older pts that balances efficacy with toxicity. Building on our promising prior experience with RVD in predominantly younger pts (Blood 2010), our study evaluated a 3-drug regimen of modified RVD in the transplant-ineligible population.

Methods: Modified RVD ("RVD-lite") was administered over a 35-day cycle. Lenalidomide 15 mg was given on days 1-21; bortezomib 1.3 mg/m² once weekly subcutaneously (SC) on days 1, 8, 15, and 22; and dexamethasone 20 mg on days 1, 2, 8, 9, 15, 16, 22 and 23 for pts ≤75 yrs and days 1, 8, 15, 22 for pts older than 75 yrs. Intravenous (IV) bortezomib was used in cycle 1 for the first 10 pts for pharmacokinetic (PK) analysis. Eligibility requirements included ECOG performance status ≤ 2 and acceptable hepatic, renal and hematologic function. The primary objective was to evaluate the objective response rate (ORR) of modified RVD in transplant-ineligible pts. Secondary objectives included evaluation of the safety profile, progression free survival (PFS), overall survival, response rate with respect to cytogenetics, and the PK profile of IV and SC bortezomib. Exploratory analysis will determine minimal residual disease (MRD) status by deep sequencing and correlate with outcomes in patients who achieve a VGPR or better.

Results: Fifty-three eligible pts have enrolled between 4/17/13 and 7/25/15, and of those, 50 received at least one dose of therapy. Median age at study entry was 72 years (range 65-91) with 29 women and 24 men. ECOG performance status of pts enrolled was 0 in 25 (47%), 1 in 20 (38%), and 2 in 8 (15 %) pts. The ISS stage was I in 21 (40%), II in 16 (30%), and III in 16 (30%) pts. Treatment-related toxicities were reported for 49 pts. Fatigue was the most commonly reported toxicity occurring in 31/49 (63%), and was mostly grade 1 or 2 and manageable (25/31). Peripheral neuropathy of any grade was reported in 21/49 (43%) pts including grade 1 (11, 22%), 2 (9, 18%), and 3 (1, 2%). Grade 3 or greater toxicities included hypophosphatemia in 15 (31%) and rash in 5 (10%) pts. PK data comparing IV and SC dosing showed no significant differences in plasma concentrations of bortezomib at 5 hours. In the SC route, high body mass index (BMI) patients tended to have low concentration at both the 5 and 30 minute measures but not at 5 hours. There was no correlation with BMI using the IV route. At the planned analysis after 4 cycles that now includes 40 pts, the investigator-reported ORR of PR or better was 90% (CR - 10, VGPR - 14, PR - 12, SD - 4). Five pts withdrew from the study after less than 4 cycles. Of those, one withdrew for worsening adrenal insufficiency, one for rash attributed to lenalidomide, one at the Investigator's discretion, and two for excessive travel distance. Five additional pts have been enrolled but have not completed 4 cycles. Of 48 evaluable patients, the median survival has not been reached. Median duration of follow-up is 17.2 months and the 1-year PFS is 95% (95% CI 0.888, 1) and 2-year PFS is 68% (95% CI 0.512, 0.908). Exploratory data on bone marrow samples on pts achieving VGPR or better have been collected and analysis for MRD is in process. Gene expression profiling was performed using MMprofiler (SkylineDx). High-risk signature will be correlated with pt outcomes.

Conclusions: ModifiedRVD is a well-tolerated and highly effective regimen in the transplant-ineligible population. The ORR rate after 4 cycles suggests that this combination at modified doses and on a weekly schedule is very active. The side effect profile proved manageable and was well tolerated in an older population despite the variance of performance status at study entry. There were no significant differences in plasma concentrations of bortezomib observed between IV and SC dosing. The study is fully accrued and this analysis suggests that alternative dosing and schedule of RVD may both improve tolerability and enhance clinical benefit in newly diagnosed, transplant-ineligible MM pts.