Efficacy and Safety of Carfilzomib at 56mg/m² with Cyclophosphamide and Dexamethasone (K56Cd) in Newly Diagnosed Multiple Myeloma Patients Followed By ASCT or K56Cd Consolidation: Initial Results of the Phase 2 Cardamon Study

Introduction: Carfilzomib (20/36mg/m²) triplets with Lenalidomide-Dexamethasone (KRd), or Cyclophosphamide-Dexamethasone (KCd) are safe and effective in patients with newly diagnosed multiple myeloma(NDMM). The higher dose of 56mg/m² is effective as a doublet with Dexamethasone in the relapsed setting, but there is limited data on this dose in triplet combinations in the frontline setting.

Aim: The CARDAMON study evaluated KCd with bi-weekly carfilzomib (56mg/m²) as induction in NDMM patients, and the benefit of ASCT versus K56Cd consolidation followed by carfilzomib maintenance. Co-primary endpoints were major response (≥VGPR rate) to 4 induction cycles of K56Cd, and 2-year PFS for ASCT versus K56Cd consolidation. Here we report interim analysis of the first primary endpoint of ≥VGPR rate to K56Cd induction.

Methods: Transplant eligible ND patients received 4 x 28d cycles of K56Cd (carfilzomib:20/56mg/m², IV d1, 2, 8, 9, 15, 16, cyclophosphamide 500mg orally d1, 8, 15 and dexamethasone 20mg d1, 2, 8, 9, 15, 16). Responding patients with a successful stem cell harvest (PBSCH) were randomised to autologous stem cell transplant (ASCT) or 4 more cycles of K56Cd as consolidation, followed by 18 months carfilzomib maintenance (K56 days 1, 8, 15) for both arms. Trial recruitment completed in July 2019. Response was assessed by IMWG criteria; all patients had MRD testing by multi-parameter flow cytometry (10^-5) after PBSCH. Adverse risk genetics was any one of t(4;14), t(14;16), t(14,20) or del(17p).

Results: 281 pts were registered between 06/2015 and 07/2019; we report outcomes for 252 patients who either completed induction or came off study before end of induction. Median age was 58yrs(33-74), 91% ECOG 0-1, 45.2% ISS I, 24.7% adverse risk (48.5% when including 1p/1q+). Best response at end of induction or after PBSCH (n=250) was: ≥VGPR 59.2%, ORR 87.6%. ≥VGPR rate in adverse risk patients was 53.4% vs 61.9% in standard risk(SR), (p=0.25), ORR was similar: adverse risk, 87.9% vs standard risk, 88.1%. Post-PBSCH, 24.1% of patients were MRD-negative (patients who were withdrawn due to insufficient induction response or toxicity and those with an inconclusive result were grouped with the MRD-positive). Of 19 patients in sCR/CR, 9 were MRD-negative(47.4%) while 40/110 (36.4%) of VGPR patients were MRD-negative. MRD-negative rates in adverse and standard risk patients were 22.8% and 24.7% respectively. 10 patients progressed during or at end of induction, and 12 were withdrawn for toxicity.

There were 4 deaths during induction, one from myocardial infarction, the other 3 from cardiac arrest, associated with bronchopneumonia and sepsis. During induction, 114 serious adverse events (SAEs) were reported in 72/252 patients, notable ones were thrombotic microangiopathy (2), grade 3 cardiac ischaemia (4), infection (16.3%, mainly lung), renal impairment (6), G3 hypertension (3), thromboembolism(2). Specific guidance for hypertension management was incorporated. 25% of patients are currently reported to have received a dose modification during induction. Full details of adverse events and dose intensity will be presented at the meeting.

Conclusion: K56Cd is an effective induction regimen in NDMM patients, and has equivalent MRD negative rates in adverse and standard risk disease. The SAE profile is in keeping with published safety data with carfilzomib.