Daratumumab Maintenance after Autologous Hematopoietic Stem Cell Transplantation for Newly Diagnosed Multiple Myeloma

Background: Maintenance therapy after autologous hematopoietic stem cell transplantation (ASCT) is a standard of care in newly diagnosed multiple myeloma (NDMM). Lenalidomide maintenance after transplantation is the most frequently recommended regimen. Daratumumab has been increasingly used as a maintenance drug in NDMM. However, there is no enough clinical information about daratumumab as maintenance strategy after ASCT. This study is aim to evaluate the efficacy and safety of daratumumab as maintenance after ASCT for NDMM.

Patients and Methods: Clinical data, hematological and renal response, and safety of 15 post-transplant patients with NDMM who had received daratumumab maintenance between 1 May 2022 and 30 June 2023 were retrospectively analyzed. Daratumumab-naive patients received weekly dosing (16mg/kg) for the first 8 weeks.

Results: Fifteen patients (11 males and 4 females) with median age of 58 years (41～72 years) , were included. Thirteen patients were daratumumab native, 6 patients had renal impairment, and 2 patients with high-risk cytogenetics. The median infusion times of daratumumab were 12 (6～17) times. Efficacy was evaluable in all 15 patients，and daratumumab maintenance therapy increase the rate of stringent complete response (from 6 [40%] to 9 [60%] ) by 20%，improved the renal response rate and median eGFR in patients with renal injury. During maintenance therapy with daratumumab, the most common hematological grade 3 adverse events(AE) were lymphopenia (4 [26.67%] of 15 patients), non-hematologic adverse events were infusion-related reactions (7 [46.67%] of 15 patients) and grade 3 pneumonia (5 [33.33%] of 15 patients). These 5 pneumonia patients were daratumumab naive ( 5 [38.46%] of 13 patients) , with median 8 (6～10)infusions. Among them, 3 patients chest CT showed interstitial infiltrates, and combination of methylprednisolone was effective. With a median follow-up of 12 months, one patient had died (not related to daratumumab treatment), 1-year OS rate was 93.33%.

Conclusions: Daratumumab was safe and effective as a maintenance agent for post-ASCT patients with NDMM, and adverse events were controllable. The most common AE is grade 3 pneumonia, maybe a less dose-intense maintenance regimen for the first 8 weeks can reduce the incidence of pneumonia.