Daratumumab, Pomalidomide, and Dexamethasone (DPd) for the Treatment of Relapsed/Refractory Multiple Myeloma: A Single Institution Experience

Background: Daratumumab triplet regimens containing dexamethasone and lenalidomide or bortezomib are an effective treatment option for patients with relapsed/refractory multiple myeloma (RRMM). Daratumumab was recently FDA-approved in combination with the second-generation immunomodulatory drug, pomalidomide, and dexamethasone based (DPd) on results of the EQUULEUS study where overall response rates (ORR) of 60% were seen. The goal of this retrospective study was to analyze clinical outcomes of the DPd triplet regimen in either a daratumumab and pomalidomide naïve or refractory population of heavily pretreated RRMM patients at our institution.

Methods: Thirty-two patients with RRMM treated with DPd at the University of Kansas Health System between November 2015 and July 2018 were included in our analysis. DPd consisted of 28-day cycles of daratumumab 16 mg/kg intravenously (weekly for cycles 1 and 2, every 2 weeks for cycles 3-6, and every 4 weeks thereafter until disease progression); pomalidomide 4 mg orally (PO)on Days 1-21 and adjusted for cytopenia or toxicities; and dexamethasone 40 mg PO weekly adjusted based on tolerance. based on age. Responses were evaluated using IMWG criteria. Patient characteristics, disease course, and outcomes were summarized with descriptive statistics. Kaplan-Meier analyses were used to estimate progression-free (PFS) and overall survival (OS).

Results:The median age was 64 years (range 44-83). Twenty-three patients (72%) had IgG isotype, 11 patients (34 %) had ISS stage III disease at diagnosis, 13 patients (41%) had high risk cytogenetics, and 13 patients (41%) had extramedullary disease. Median number of previous lines of therapy was 4 (1-9). Twenty-two patients (69%) received ≥3 prior therapies. Twenty-three patients (72%) were proteasome inhibitor refractory, 28 patients (88%) were immunomodulator refractory, 9 patients (28%) were daratumumab refractory, and 3 patients (15%) were double refractory to daratumumab and pomalidomide. Twenty-eight patients (88%) had received autologous stem cell transplant (ASCT) prior to DPd; 12 patients (38%) had ≥2 prior transplants. Median number of DPd cycles received was 6 (2-30) and the median duration of treatment was 5 months (2-30). At a median follow-up of 8.4 months (range: 2-29), the overall response rate (ORR) for all patients was 72% which compares favorably to the ORR of 60% in the EQUULEUS study. However, about half of the responses were partial responses (PR) (47%). The ORR rate for those who were refractory to either pomalidomide or daratumumab was 65%. The PFS was 8.3 months, while the median OS was not reached.

Conclusion: DPd was recently approved for the treatment of RRMM. Our ORR compares favorably to the EQUULEUS study, however about half of responses were partial responses or better. Surprisingly, our analysis shows an impressive ORR in patients with previous exposure to proteasome inhibitor and immunomodulatory therapies in RRMM population, suggesting a benefit of DPd even in patients who received prior pomalidomide or daratumumab.

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