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Treatment of Newly Diagnosed Myeloma (excluding t-cell redirection therapy)

Daratumumab-Based Maintenance in Patients with Relapsed Multiple Myeloma after Salvage Autologous Hematopoietic Stem Cell Transplantation

P-321: Daratumumab-Based Maintenance in Patients with Relapsed Multiple Myeloma after Salvage Autologous Hematopoietic Stem Cell Transplantation

Thursday, September 26, 2024

YA

Yosra Aljawai, MD

Assistant Professor
The University of Texas MD Anderson Cancer Center, United States

Introduction: In this phase II clinical trial, relapsed MM patients who underwent salvage auto-HCT received maintenance with daratumumab (dara), with the addition of pomalidomide (pom) in a later amendment. The primary end point was PFS. Patients with prior exposure to dara or pom were included, those refractory to either drug were excluded. Patients received dara SQ weekly for weeks 1–8, every 2 weeks for weeks 9–24, and monthly from week 25 until progression. Pom was given at 2 mg PO from day 1–21 every 28 days.

Results: The trial was terminated due to poor accrual after 13/56 patients were enrolled between May 2019 and August 2022. Median age at salvage auto-HCT was 64 (range: 43–76) years. Median prior lines of treatment was 2 (range: 2–4). Six patients (46%) had a prior auto-HCT. Median time from diagnosis to salvage auto-HCT was 58.3 (range 7.6-132) months. Five patients (38%) had high-risk cytogenetic abnormalities (1q+ in all 5). Eight (61%) patients received melphalan alone, 4 (31%) received busulfan/melphalan, and 1 (8%) received gemcitabine/busulfan/melphalan/panobinostat as their conditioning regimen. Three patients (23%) started maintenance with dara alone, while the remaining 10 (77%) patients received dara + pom. At study entry, 6 patients (46%) had a complete response (CR), 4 (31%) had a very good partial response (VGPR), 2 (15%) had partial response (PR), and 1 (8%) had stable disease (SD). At day 100 post maintenance, 9 (69%) were in CR, while 1 (8%) each had VGPR, PR, SD and progressive disease (PD), respectively. For the 12 patients that did not progress at day 100, best response to dara +/- pom maintenance was CR in 10 (83%), and VGPR and SD in 1 (8%) each. With a median follow up of 32.4 months (range: 20.1–43.5) from the start of maintenance, five patients progressed one of whom died. Median PFS from the date of auto-HCT, and from start of maintenance were not reached. Two- year PFS rate from start of maintenance was 82% (95%CI: 59%-100%). Most common adverse events were neutropenia (n=11, 84%; n=5, 38% grade >3), grade 1-2 fatigue (n=6, 36%), grade ≤3 viral infection (n=6, 46%), and grade ≤3 bacterial infection, grade 1-2 diarrhea and grade 1 thrombocytopenia (n=5, 38% each).

Conclusions: Maintenance therapy with dara, +/- pom, is safe and feasible after a salvage auto-HCT, with 83% achieving a CR. After a median follow up exceeding 2 years, median PFS from the date of auto-HCT and from the start of maintenance was not reached.