Carfilzomib, lenalidomide, dexamethasone, and cyclophosphamide (KRdc) as induction therapy for transplant-eligible, newly diagnosed multiple myeloma patients (Myeloma XI plus ): Interim analysis of an open-label randomised controlled trial

Background Carfilzomib is a second-generation irreversible proteasome inhibitor that is efficacious in the treatment of myeloma and carries less risk of peripheral neuropathy than first-generation proteasome inhibitors, making it more amenable to combination therapy. Methods and findings The Myeloma XI+ trial recruited patients from 88 sites across the UK between 5 December 2013 and 20 April 2016. Patients with newly diagnosed multiple myeloma eligible for transplantation were randomly assigned to receive the combination carfilzomib, lenalidomide, dexamethasone, and cyclophosphamide (KRdc) or a triplet of lenalidomide, dexamethasone, and cyclophosphamide (Rdc) or thalidomide, dexamethasone, and cyclophosphamide (Tdc). All patients were planned to receive an autologous stem cell transplantation (ASCT) prior to a randomisation between lenalidomide maintenance and observation. Eligible patients were aged over 18 years and had symptomatic myeloma. The co-primary endpoints for the study were progression-free survival (PFS) and overall survival (OS) for KRdc versus the Tdc/Rdc control group by intention to treat. PFS, response, and safety outcomes are reported following a planned interim analysis. The trial is registered (ISRCTN49407852) and has completed recruitment. In total, 1,056 patients (median age 61 years, range 33 to 75, 39.1% female) underwent induction randomisation to KRdc (n = 526) or control (Tdc/Rdc, n = 530). After a median follow-up of 34.5 months, KRdc was associated with a significantly longer PFS than the triplet control group (hazard ratio 0.63, 95% CI 0.51-0.76). The median PFS for patients receiving KRdc is not yet estimable, versus 36.2 months for the triplet control group (p < 0.001). Improved PFS was consistent across subgroups of patients including those with genetically high-risk disease. At the end of induction, the percentage of patients achieving at least a very good partial response was 82.3% in the KRdc group versus 58.9% in the control group (odds ratio 4.35, 95% CI 3.19-5.94, p < 0.001). Minimal residual disease negativity (cutoff 4 x 10(-5) bone marrow leucocytes) was achieved in 55% of patients tested in the KRdc group at the end of induction, increasing to 75% of those tested after ASCT. The most common adverse events were haematological, with a low incidence of cardiac events. The trial continues to follow up patients to the co-primary endpoint of OS and for planned long-term follow-up analysis. Limitations of the study include a lack of blinding to treatment regimen and that the triplet control regimen did not include a proteasome inhibitor for all patients, which would be considered a current standard of care in many parts of the world. Conclusions The KRdc combination was well tolerated and was associated with both an increased percentage of patients achieving at least a very good partial response and a significant PFS benefit compared to immunomodulatory-agent-based triplet therapy. Author summary Why was this study done? Although outcomes for myeloma patients have improved over recent decades, many patients will eventually relapse, and finding new treatment regimens that keep patients in first remission for longer is imperative. Treatment combinations aim to target myeloma using different mechanisms of action. This aims to prevent resistant cells remaining and leading to relapse. Carfilzomib has been shown to be effective in the treatment of relapsed myeloma when given in combination with lenalidomide. We performed this study to compare the outcomes of newly diagnosed myeloma patients treated with the combination carfilzomib, lenalidomide, dexamethasone, and cyclophosphamide (KRdc) to those of patients treated with immunomodulatory-agent-based triplet control combinations. What did the researchers do and find? A total of 1,056 patients with newly diagnosed myeloma were randomised between KRdc and control. Patients receiving the quadruplet KRdc combination were more likely to achieve at least a very good partial response and had longer progression-free survival than patients receiving control treatments. Side effects were not significantly increased with the quadruplet combination compared to control. What do the findings mean? The results suggest that KRdc can elicit deep responses and long periods of progression-free survival with tolerable side effects in newly diagnosed myeloma patients. Further studies are needed to compare KRdc to combinations of other new agents for the treatment of newly diagnosed myeloma patients.