High-Dose Carfilzomib and Dexamethasone As First-Line Treatment in Symptomatic Multiple Myeloma

Abstract Background: Carfilzomib (Cfz) is approved for use in relapsed and refractory multiple myeloma (RRMM) at a dose of 27mg/m2 after escalation from 20mg/m2. The response rate for Cfz and dexamethasone (dex) as first-line therapy in multiple myeloma (MM) is unknown. Higher doses of Cfz have been shown to enhance overall response in RRMM (Lendvai 2014); the presence of a dose-response relationship of Cfz for first-line therapy in untreated MM has not been evaluated. A protocol of Cfz-Dex induction at two dosing levels, followed by BiRd (Clarithromycin 500mg PO BID, Lenalidomide (Len) 25mg for 21/28 days, Dex 40mg weekly) consolidation, and thereafter Len (10mg 12/28 days) maintenance, evaluated response and safety by Cfz dose level in patients (pts) with newly diagnosed symptomatic MM. The ORR and safety data for Cfz-Dex induction stratified by Cfz dose is reported. Methods: 70 patients with untreated MM were enrolled in a phase 2 study of Cfz-dex. Cfz-dex is: Cfz IV on D1, 2, 8, 9, 15, 16 of a 28-day cycle at a dose of 20mg/m2 on days 1, 2 of cycle 1 and 45mg/m2 thereafter and Dex 40mg on D1, 8, 15, 22. After the first 26 pts were enrolled, the protocol was amended to increase the Cfz from 45 to 56mg/m2. Screening echocardiogram and pulmonary function testing were performed. Brain natriuretic peptide (BNP) was measured with each cycle. Cfz-dex was continued until plateau in disease response (unchanged M-protein for 2 cycles). Elective stem cell collection was then performed in transplant eligible pts. This was followed by BiRd until 2nd response plateau, and then by LEN maintenance. Disease response evaluation was performed monthly with serum and urine protein electrophoresis, immunofixation, and free light chain analysis; bone marrow biopsy with skeletal imaging was used to confirm MM progression or complete response (CR). Cytogenetic testing was performed on CD138-selected cells. Results: 25 pts received Cfz-Dex at 45 mg/m2 and 44 (out of 45 enrolled) pts at 56 mg/m2 for at least 1 cycle and were evaluable for response. 56% of pts were ISS II/III and 64% had high-risk cytogenetics as per IMWG definition. Pts received a median of 5 cycles of Cfz-dex in both the 45 mg/m2 (range 1-10) and 56 mg/m2 groups (range 1-14). Maximum response to Cfz-dex is shown in Table 1. There was no difference in response between the 45 and 56mg/m2 groups (P = 0.20). Median time to PR and maximum response for the 45 and 56 mg/m2 cohorts were both 2 and 3 cycles, respectively. 42 pts had stem cell harvest. All collected stem cells to support at least two transplants (> 5 x 10^6 CD34/kg) in one mobilization attempt using G-CSF, with mean yield of 13.74x10^6 CD34/kg (range 5.94-32.14). 79% collected in 1 apheresis session. Adverse events (AEs) were notable for renal failure in 3 pts (2 Grade 2, 1 grade 3) and congestive heart failure in 1 pt (grade 3). Two of the 3 cases of renal failure occurred in the 56 mg/m2 cohort, all other AEs occurred in the 45mg/m2 cohort. All AEs resolved after stopping Cfz. There was no correlation with TTE, PFTs or serial BNPs and development of cardiac or pulmonary toxicity. Discussion: This is the first prospective study evaluating induction responses to Cfz-dex in MM. Cfz-dex is safe and active in induction at both 45 and 56 mg/m2, with an ORR of 93% and rate of >= VGPR of 68% despite a primarily high risk population. Specific dose did not correlate with response. Higher dose of Cfz did not lead to more toxicity. Cfz-dex induction led to successful stem cell collection in all attempts. Cfz-dex is a highly active and well-tolerated induction regimen. Transitioning to IMiD-based therapy after maximum response led to deeper responses with a remarkable 97% rate of VGPR or better. Table 1 . Maximum Response with Cfz-Dex, followed by BiRD consolidation and lenalidomide maintenance: Response Category Cfz-Dex 45 mg/m2 Cfz-Dex 56 mg/m2 Overall Cfz-Dex phase BiRD phase Lenalidomide maintenance phase N = 25 (%) N = 44 (%) N = 69 (%) N = 44 (%) N = 33 (%) >= PR 22 (88) 42 (95) 65 (93) 44 (100) 33 (100) >= VGPR 16 (72) 31 (70) 45 (68) 42 (95) 32 (97) >= CR 3 (12) 2 (5) 5 (7) 12 (27) 15 (45) SCR 3 (12) 2 (5) 5 (7) 9 (20) 13 (39) CR 0 (0) 0 (0) 0 (0) 3 (7) 2 (6) VGPR 13 (52) 29 (66) 42 (61) 30 (68) 17 (52) PR 6 (24) 11 (25) 17 (25) 2 (5) 1 (3) SD 3 (12) 2 (5) 5 (7) 0 0 Disclosures Mark: Calgene: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Off Label Use: Carfilzomib as first line therapy in myeloma.. Rossi: Amgen: Speakers Bureau; Takeda: Speakers Bureau; Celgene: Speakers Bureau. Pearse: Celegen: Consultancy. Perry: Takeda: Speakers Bureau; Celgene: Speakers Bureau. Pekle: Celgene: Speakers Bureau; Takeda: Speakers Bureau. Huang: Celgene: Research Funding. Coleman: Celgene: Speakers Bureau; Takeda: Speakers Bureau. Chen-Kiang: Celgene: Consultancy. Niesvizky: Celgene: Consultancy, Speakers Bureau.