S175: ATLAS: A PHASE 3 RANDOMIZED TRIAL OF CARFILZOMIB, LENALIDOMIDE, AND DEXAMETHASONE VERSUS LENALIDOMIDE ALONE AFTER STEM-CELL TRANSPLANT FOR MULTIPLE MYELOMA

Abstract

Background: Treatment following autologous stem cell transplantation (ASCT) for multiple myeloma (MM) remains an area of active investigation. We have shown that extended post-ASCT treatment with carfilzomib, lenalidomide, and dexamethasone (KRd) after KRd induction improved the depth and duration of response (Jasielec et al, Blood 2020), suggesting a benefit of post-ASCT KRd therapy. Aims: We report the results of ATLAS, a multicenter, international, open-label randomized phase 3 study to determine the efficacy and safety of post-ASCT KRD vs standard lenalidomide (R) maintenance (NCT02659293). Methods: Newly-diagnosed MM patients (pts) who received any induction therapy for up to 12 months (mo) followed by single ASCT and achieved at least stable disease within 100 days afterward were randomized to receive either KRd or R, stratified by post-transplant response (≥VGPR vs <VGPR) and cytogenetic risk [standard risk (SR) vs high [HR: presence of t(4;14), t(14;16), or del(17p)]. Pts randomized to KRd received carfilzomib 36 mg/m2 on days (D) 1,2,8,9,15,16 for 4 cycles (C) then D1,2,15,16 starting C5; R 25 mg D1-21, and dexamethasone 20 mg D1,8,15,22 in 28-day cycles. KRd pts with SR who reached IMWG-defined MRD-negativity after C6 de-escalated therapy to R alone after C8 (KRd->R); the rest continued KRd through C36 followed by R alone until progression. Pts randomized to R received lenalidomide 10 mg C1-3 and then 15 mg daily. The primary endpoint was progression free survival (PFS) rate: based on historical PFS rates, a sample size of 180 Pts was calculated to provide 85% power with 2-sided alpha 0.05. Secondary endpoints included minimum residual disease (MRD) negativity response rates and treatment-related adverse events. Results: 180 pts were enrolled (R n=87; KRd n=93) through 10/21/20; data cutoff was 12/31/21. Pt characteristics in the KRd and R arms were balanced for median age (58 vs 59 yrs), ≥VGPR (88% vs 92%), and HR (23% vs 21%). After 6 cycles, 47% pts in the KRd arm and 29% in the R arm achieved MRD-negativity (p=0.017). 34 KRd pts eligible for de-escalation converted to R alone after C8 and were analyzed on the KRd arm per intention-to-treat. At median follow-up of 33.8 mo, 23 pts (25%) on the KRd arm and 38 pts (44%) on the R arm progressed; estimated median PFS was 59.0 mo for KRd vs 41.4 mo for R (Hazard Ratio 0.56, logrank p=0.026). At cutoff, 90% of KRd and 87% of R pts were alive; no deaths were treatment-related. All-grade toxicities were generally comparable between arms. The most common grade 3+ AEs and those of special interest were neutropenia (KRd 47%; R 59%), thrombocytopenia (KRd 13%; R 7%), infections (KRd 15%; R 6%), cardiovascular toxicities (KRd 4%, R 5%), and secondary malignancies (KRd 2, R 2). Image:Summary/Conclusion: This is the first randomized phase 3 trial demonstrating superior PFS with extended post-transplant KRd therapy compared to R maintenance. Therefore, MRD/risk-adapted post-ASCT extended KRd treatment may represent a new standard of care.