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 a median age at diagnosis of 66 years. Despite significant improvements in patient outcomes, there is a lag in survival in older transplant-ineligible patients compared to their younger counterparts. Traditionally, melphalan and prednisone-based regimens were the most widely accepted treatment options in this older, transplant-ineligible population. More recently, the FIRST trial has explored the use of lenalidomide and dexamethasone in these patients. Here, we sought to incorporate optimal novel agent-containing regimens in transplant-ineligible, older patients that balance efficacy with toxicity. Building on our prior experience with RVD in predominantly younger patients, 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 was given as a single daily oral dose of 15 mg days 1-21; bortezomib 1.3 mg/m² once weekly subcutaneously on days 1, 8, 15, and 22; and dexamethasone 20 mg on days 1, 2, 8, 9, 15, 16, 22 and 23 for patients ≤75 yrs and days 1, 8, 15, 22 for patients older than 75 yrs. Intravenous bortezomib was used only in cycle 1 for the first 10 patients for pharmacokinetic 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 patients. Secondary objectives included evaluation of the safety profile of modified RVD, progression free survival, overall survival, time to response, response duration, the response rate with respect to cytogenetics, and the pharmacokinetic profile of intravenous and subcutaneous bortezomib. Exploratory analysis will determine minimal residual disease (MRD) status by genotyping and correlate with outcomes in patients who achieve a VGPR or better.

Results: Forty-one eligible patients have enrolled between 4/17/13 and 7/18/14, and of those 38 received at least one dose of therapy. Median age at study entry was 73 years (range 65-91) with 22 women and 16 men. ECOG performance status of patients enrolled was 0 in 19 (46.3%), 1 in 15 (36.6%), and 2 in 6 (14.6%) patients. The ISS stage was I in 15 (36.6%), II in 9 (22.0%), and III in 10 (24.4%) patients. Treatment-related toxicities were reported for 34 subjects. Fatigue was the most commonly reported toxicity occurring in 17/34 (50.0%), and of those 16/17 were grade 1 or 2 and manageable. Peripheral neuropathy of any grade was reported in 14/34 (41.2%) of patients including Grade 1 -7 (20.6%), 2 – 6 (17.6%), and 3 – 1 (2.9%). 12/34 (35.3%) reported edema of which 11/12 (91.7%) were grade 1. Grade 3 or greater toxicities included hypophosphatemia - 11 (32.3%), Rash - 4 (11.8%), and mood changes - 2 (5.9%). Pharmacokinetic data comparing intravenous and subcutaneous dosing of bortezomib has been completed and analysis is in process. At a planned interim analysis after 4 cycles that included 33 patients, the investigator-reported ORR of PR or better was 81.8% (CR -5, VGPR – 11, PR - 11, SD 3). Three patients withdrew from the study after less than 1 cycle. Of those, one withdrew for worsening adrenal insufficiency, one for rash attributed to lenalidomide, and one for an unrelated toxicity prompting withdrawal at the Investigator’s discretion. Five additional patients have enrolled but have not completed 4 cycles. Of those, responses thus far include 1 CR, 2 PRs, 1 SD, and 1 patient who has not completed one cycle at the time of this analysis. Exploratory data on bone marrow samples on patients achieving VGPR or better have been collected and analysis for MRD is in process.

Conclusions: ModifiedRVD appears to be a well-tolerated and highly effective regimen in the transplant-ineligible population. The ORR rate after up to 4 cycles suggests that this combination at the modified doses and on a weekly schedule is very active. The side effect profile proved manageable and well-tolerated in an older population despite the variance of performance statuses at study entrance. Interim analysis of 38 patients suggests that alternative dosing and schedule of RVD may both improve tolerability and enhance clinical benefit in newly diagnosed, transplant-ineligible MM patients.