PF591 EFFICACY AND SAFETY OF DARATUMUMAB, LENALIDOMIDE, AND DEXAMETHASONE (D‐RD) IN RELAPSED OR REFRACTORY MULTIPLE MYELOMA (RRMM): UPDATED SUBGROUP ANALYSIS OF POLLUX BASED ON CYTOGENETIC RISK

Background: High‐risk cytogenetic abnormalities confer poor outcomes in patients (pts) with MM. In POLLUX, D‐Rd demonstrated significant clinical benefit, including prolonged progression‐free survival (PFS) vs lenalidomide and dexamethasone (Rd), and tolerability in RRMM pts. Here, we present a subgroup analysis of POLLUX, based on cytogenetic risk. Aims: The purpose of this analysis was to determine the efficacy and safety of D‐Rd vs Rd in POLLUX, based on cytogenetic risk status. Methods: Eligible pts received ≥1 prior line of therapy. Cytogenetic risk was based on a combined analysis of fluorescence in situ hybridization (FISH)/karyotype testing and next‐generation sequencing (NGS). High‐risk pts had t(4;14), t(14;16), or del17p abnormalities; standard (std)‐risk pts did not meet the high‐risk criteria. Minimal residual disease (MRD; 10–5) was assessed via NGS using clonoSEQ® assay V2.0. Results: In POLLUX (D‐Rd, n = 286; Rd, n = 283), 17.1% of pts in the D‐Rd group and 20.1% of pts in the Rd group had high cytogenetic risk abnormalities. After 44.3 months (mo) of median follow up, D‐Rd prolonged PFS vs Rd in pts with high‐ (median 26.8 vs 8.8 mo; HR, 0.54 [95% CI, 0.32–0.91]; P = 0.0175) or std‐risk (median not reached [NR] vs 19.9 mo; HR, 0.41 [95% CI, 0.31–0.55]; P <0.0001) disease. Higher ORR was seen with D‐Rd vs Rd in patients with high risk (87.5% vs 69.1%; P = 0.0115) and std risk (93.6% vs 79.2%; P <0.0001) disease. Responses with D‐Rd were deep, including higher rates of ≥CR (high risk: 43.8% vs 9.1%; std risk: 59.3% vs 27.0%) and ≥VGPR (high risk: 70.8% vs 32.7%; P = 0.0003; std risk: 82.8% vs 55.1%; P <0.0001). Rates of MRD negativity (high risk: 28.6% vs 0%; P <0.0001; std risk: 32.9% vs 8.2%; P <0.0001) and sustained MRD negativity for ≥6 mo (high risk: 12.2% vs 0%; P = 0.0082; std risk: 17.9% vs 1.1%; P <0.0001) and ≥12 mo (high risk: 10.2% vs 0%; P = 0.0188; std risk: 14.0% vs 0.5%; P <0.0001) were higher with D‐Rd vs Rd. D‐Rd significantly prolonged PFS vs Rd in pts after first relapse (high risk: median 46.0 vs 7.3 mo; HR, 0.26 [95% CI, 0.11–0.59]; P = 0.0005; std risk: median NR vs 20.6 mo; HR, 0.43 [95% CI, 0.28–0.66]; P <0.0001; Figure). Additionally, D‐Rd significantly prolonged PFS2 vs Rd in high‐ (median 38.3 vs 22.1 mo; HR, 0.53 [95% CI, 0.30–0.93]; P = 0.0249) or std‐risk (median NR vs 33.8 mo; HR, 0.53 [95% CI, 0.39–0.72]; P <0.0001) pts. Additional data including safety analyses will be presented. Summary/Conclusion: D‐Rd demonstrates significant efficacy in both high‐risk and standard risk RRMM with a median PFS of 26.8 mo and median not reached, respectively. In addition, more patients achieved a sustained MRD response which translates into better patient outcomes regardless of cytogenetic risk. These data suggest D‐Rd is an effective regimen regardless of cytogenetic risk. NCT02076009 image

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