Sustained Minimal Residual Disease Negativity in Newly Diagnosed Multiple Myeloma (NDMM) Patients Treated with Carfilzomib (CFZ), Lenalidomide (LEN), and Dexamethasone (DEX) Followed By 2 Years of Lenalidomide Maintenance (CRd-R): Updated Results of a Phase 2 Study

Abstract Background: State of the art treatment for patients with NDMM involves induction with triplet regimens utilizing newer therapies including combinations of immunomodulatory (IMiD) drugs and proteasome inhibitors (PI) which improve progression-free survival (PFS) over doublet regimens. CFZ is a selective PI that inhibits the chymotrypsin-like activity of the 20S proteasome and has been approved in combination with LEN and DEX for the treatment of patients with relapsed or refractory MM who have received 1-3 lines of therapy. Furthermore, it has been associated with decreased neuropathy and increased clinical benefit over bortezomib-based combinations. This phase 2 study of 45 patients demonstrated that deep and durable responses with CRd-R can be achieved in the NDMM setting (Korde et al. JAMA Onc 2015). Here, we expand on our initial results in assessing minimal residual disease negativity (MRDneg) at complete response (CR) and after 1 and 2 years of LEN maintenance. We also characterize depth of response by age and cytogenetic risk profile. Methods: Treatment-na•ve patients with MM were treated for 8 cycles (28-day cycles) with CFZ 20/36 mg/m2 IV days 1, 2, 8, 9, 15, 16; LEN 25 mg PO days 1-21, and DEX 20/10 mg IV/PO days 1, 2, 8, 9, 15, 16, 22, 23. Transplant eligible patients underwent stem cell collection after ≥4 cycles of CRd and then continued CRd treatment (i.e. by-default-delayed high-dose melphalan with autologous stem cell transplant; HDM-ASCT). After 8 cycles of combination therapy, patients with SD or better received 2 years of LEN 10 mg PO maintenance. The primary objective of the study was to estimate the rate of ³ Grade 3 peripheral neuropathy with secondary objectives of response (ORR), MRDneg, PFS, and response duration (DoR) assessed after every cycle during induction and subsequently after every 90 days of maintenance therapy. Assessment of MRDneg by multi-color flow cytometry (bone marrow aspirate; 10-5 sensitivity) was performed after 8 cycles of induction, and 1 and 2 years of LEN maintenance. Results: Forty-five patients meeting eligibility criteria were enrolled (60% male; median age 60, range 40-89; race: 82% White, 13% Black, 4% Asian; isotypes: 51% IgG kappa, 16% IgG lambda, 13% IgA kappa, 9% IgA lambda, 9% free kappa, and 4% free lambda). The proportion of patients who obtained a complete response (CR) with MRDneg after 8 cycles of induction, 1 year of maintenance and 2 years of maintenance was 44%, 54% and 46%, respectively (Table 1). These deep responses of MRDneg CR were observed regardless of age group or cytogenetic-based risk profile (Table 2). ORR was 98% with a DoR at 48 months of 81%. PFS at 48 months was 82% and overall survival at 58 months was 86% with a median duration of follow-up of 31 months. Toxicities, in general, were manageable, with Grade 3-4 events occurring in >1 patient including lymphopenia (69%), neutropenia (27%), thrombocytopenia (20%) anemia (18%), hypophosphatemia (18%), leukopenia (16%), maculo-papular rash (13%), alanine aminotransferase elevation (11%), fatigue (9%), dyspnea (9%), hyponatremia 7%, thromboembolism (7%), lung infection (4%), hypoalbuminemia (4%). Serious adverse events included thromboembolism (13%), dyspnea (9%), anemia (7%), lung infection (4%), thrombocytopenia (4%), hyponatremia (4%), and pleural effusion (4%). Conclusions: Upfront treatment of NDMM with modern, highly efficacious CRd-R therapy with by-default-delayed HDM-ASCT led to high rates of sustained MRDneg CR (as defined by the updated 2016 IMWG response criteria) which is correlated with longer PFS and OS. Clinically important, these deep responses were observed regardless of the age of patients or cytogenetic risk. Our findings stress the importance of utilizing highly efficacious triplet-based regimens for the treatment of patients with NDMM regardless of age or cytogenetic risk. Updated results will be presented at the Annual Meeting. Disclosures Korde: Medscape: Honoraria. Bhutani:Prothena: Research Funding; Takeda Oncology: Research Funding, Speakers Bureau; Bristol-Myers Squibb: Speakers Bureau; Onyx, an Amgen subsidiary: Speakers Bureau. Landgren:Takeda: Honoraria; Amgen: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Medscape Myeloma Program: Honoraria; Merck: Honoraria; BMS: Honoraria.