Introduction. Efficacy and safety of daratumumab monotherapy (DARA mono) in relapsed/refractory multiple myeloma (rrMM) has been shown in the single-arm phase I/II trial GEN501 and the single-arm phase II trial SIRIUS (1, 2). Since then, several indirect treatment comparisons of DARA mono versus comparator therapies have been published showing consistent results with an overall survival benefit for DARA mono (3, 4, 5, 6). This analysis compares efficacy and for the first time also safety of DARA mono data versus an international historic control group, adjusting for differences in patient populations based on individual patient level data (IPD).
Methods. IPD from the SIRIUS trial and from the International Myeloma Foundation (IMF)-cohort (7), a retrospective, multicenter cohort, were compared using a multivariate Cox proportional hazards model, on the endpoints of efficacy (overall survival (OS)) and safety (discontinuation due to adverse events (DISCONAE)). The IMF-cohort included patients with rrMM who received at least three prior lines of therapy, were refractory to both an immunomodulator (IMiD) and a proteasome inhibitor (PI), and were exposed to an alkylating agent. An inclusion criterion for the historic control group in this analysis was treatment with EU approved regimens. Baseline covariates adjusted for in the regression model included age, gender, prior lines of therapy, albumin, beta-2 microglobulin, prior exposure to pomalidomide and carfilzomib, and PI/IMiD refractory status. Several sensitivity analyses were run, including multiple imputation of missing values.
Results. Data from 106 patients treated with DARA mono (16 mg/kg) were available from SIRIUS; 258 patients from the IMF chart review fulfilled the inclusion criteria; most frequent treatment regimens contained pomalidomide plus dexamethasone (PomDex) (n=172), bortezomib (n=31), carfilzomib (n=21), cyclophosphamide (n=14) and lenalidomide (n=9). The adjusted HR for OS was 0.41 [0.25, 0.69], p<0.001, and 0.23 [0.05, 1.00], p=0.050 for DISCONAE, in favor of daratumumab. Results were consistent across a range of sensitivity analyses and were similar when restricting the comparison to DARA vs. PomDex, with HR=0.35 [0.19, 0.64], p<0.001 for OS and 0.20 [0.03, 1.54], p=0.123 for DISCONAE.
Conclusions. This comparison using real-world data of rrMM patients suggests improved efficacy and safety for DARA mono compared to approved therapy regimens used in clinical practice, including PomDex.
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