A Phase 1/2 Study of Pomalidomide, Dexamethasone and Pegylated Liposomal Doxorubicin for Patients with Relapsed/Refractory Multiple Myeloma.

Abstract 2979 Background: Thalidomide and its immunomodulatory (IMiD) derivatives such as lenalidomide have shown great promise as a treatment option for multiple myeloma (MM) patients. Pomalidomide is a newer IMiD with high in vitro potency that has shown promise as an effective treatment option for relapsed/refractory (R/R) MM patients. Recent data has shown pomalidomide to be effective in combination with dexamethasone, even for patients who are refractory to bortezomib and lenalidomide. It has been demonstrated that the addition of pegylated liposomal doxorubicin (PLD) to lenalidomide and thalidomide is effective for both R/R and frontline MM patients. Our recent trial evaluating lenalidomide in combination with dexamethasone, PLD, and bortezomib (DVD-R) showed that both efficacy and tolerability may be improved by changing the dose and schedule of these drugs. These data imply that the combination of pomalidomide, dexamethasone, and PLD for R/R MM patients may be an effective regimen. We conducted a phase 1/2 trial investigating the safety and efficacy of pomalidomide in combination with IV dexamethasone and (PLD) using a modified dose and longer 28-day schedule for patients with R/R MM. The combination of PLD, dexamethasone and lenalidomide without bortezomib has not been previously evaluated. Methods: For enrollment into the phase 1 dose-escalation portion of the study, eligible pts had to have progressive MM at the time of enrollment that has relapsed following stabilization to at least one anti-myeloma regimen or is refractory defined as progressed while receiving anti-myeloma treatment. For enrollment into the planned phase 2 portion of the study, eligible pts have to be refractory to lenalidomide (singe-agent or in combination) demonstrated by progressive disease while receiving lenalidomide or relapse within 8 weeks of the last dose of lenalidomide. Patients who have received previous pomalidomide treatment were not eligible. Patients must not have received chemotherapy, corticosteroids, immunotherapy, antibody therapy, or treatment with thalidomide, lenalidomide, or bortezomib within 3 weeks of receiving study drug, nor extensive radiation therapy within 4 weeks of receiving study drug. During the phase 1 part of the trial, pomalidomide was administered orally at 2, 3, or 4 mg daily in 3 successive cohorts of 3 patients each on days 1–21 of each 28-day cycle. Dexamethasone was administered intravenously at 40 mg over 30 min on days 1, 4, 8, and 11 of each cycle. PLD was administered at 5 mg/m2 as an IV infusion over 30–90 min on days 1, 4, 8, and 11 of each cycle. Pomalidomide doses were escalated until maximum tolerated dose (MTD) was reached. Once MTD was reached, all subsequent patients will be enrolled at that dose. Results: Ten of 40 planned patients have been enrolled to date, all during the phase 1 portion of the trial. Pts received a median of 4 prior treatments (range, 1–8) with a median of 1 prior PLD regimens (range, 0–1). Pts have completed a median of 1 cycle (range: 0–12) with a median of 1.2 months of follow up (range: 0.2–3.6). To date, the trial has enrolled all three cohorts in phase 1 (1 patient in cohort 1 chose to withdraw during Cycle 1 and was replaced). MTD has not yet been reached with no dose limiting toxicities (DLTs) in the first 2 cohorts. The 3 patients in cohort 3 are currently in Cycle 1. Seven patients are currently evaluable for efficacy and the 3 patients in cohort 3 have not yet had response assessment. Best response for evaluable patients is as follows: 3 patients have shown partial response, 2 patients have shown minor response, 1 is exhibiting stable disease (SD) but shows a decreasing monoclonal protein, and 1 has progressed. The incidence of reported adverse events (AEs) so far is low. Only 1 grade 3 or 4 (G3, G4) AE has been observed. The most common AEs were lymphopenia, which occurred in 6 pts (G1: 3; G2: 2; G3: 1), elevated urea nitrogen occurred in 4 pts (all G1), neutropenia occurred in 4 pts (all G1), and leukopenia occurred in 4 pts (all G1). Conclusions: The combination of pomalidomide with dexamethasone and PLD on a 28-day cycle may be an effective treatment option with acceptable tolerability for relapsed/refractory MM patients. Disclosures: Berenson: Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau.