SUMMARY: The FDA on September 20, 2024, approved Isatuximab-irfc (SARCLISA®) with Bortezomib, Lenalidomide, and Dexamethasone for adults with newly diagnosed multiple myeloma who are not eligible for Autologous Stem Cell Transplant (ASCT). Multiple Myeloma is a clonal disorder of plasma cells in the bone marrow and the American Cancer Society estimates that in the United States, 35,780 new cases will be diagnosed in 2024 and 12,540 patients are expected to die of the disease. Multiple Myeloma is a disease of the elderly, with a median age at diagnosis of 69 years and characterized by intrinsic clonal heterogeneity. Almost all patients eventually will relapse, and patients with a high-risk cytogenetic profile, extramedullary disease or refractory disease have the worst outcomes. The introduction of Proteasome Inhibitors, Immunomodulatory agents and CD38 targeted therapies has resulted in higher Response Rates, as well as longer Progression Free Survival (PFS) and Overall Survival (OS), with the median survival for patients with myeloma approaching 10 years or more. Nonetheless, multiple myeloma in 2024 remains an incurable disease.
Newly diagnosed multiple myeloma patients are often treated with Bortezomib, Lenalidomide, and Dexamethasone (VRd), after the SWOG S0777 trial established this regimen as a standard first-line treatment, regardless of their transplantation eligibility. With the introduction of CD38 targeted therapies, new treatment combinations are being explored to increase the depth of response and attain long-term disease control.
Isatuximab-irfc (SARCLISA®) is a CD38-targeting IgG1monoclonal antibody, similar to Daratumumab (DARZALEX®), but unlike Daratumumab, is not associated with complement activation, and can therefore be more readily given to patients with asthma or Chronic Obstructive Pulmonary Disease. Further, Isatuximab targets a specific epitope on the CD38 receptor, and this distinction from Daratumumab allows use of Isatuximab in cases when Daratumumab fails. Additionally, Isatuximab infusions are less cumbersome. The FDA in 2021, approved Isatuximab in combination with Carfilzomib (KYPROLIS®) and Dexamethasone, for the treatment of adult patients with Relapsed or Refractory multiple myeloma who have received one to three prior lines of therapy.
The IMROZ trial (NCT03319667) was an international, multicenter, open-label, Phase 3 randomized controlled trial, designed to evaluate the efficacy and safety of Isatuximab in combination with the established regimen of Bortezomib, Lenalidomide, and Dexamethasone (VRd) compared to VRd alone. This study aimed to address a critical gap in treatment options for patients with newly diagnosed multiple myeloma who are ineligible for ASCT, a situation often faced by older patients or those with significant comorbidities. A total of 446 patients, aged 18 to 80 years, with symptomatic, previously untreated multiple myeloma were randomly assigned in a 3:2 ratio to receive either the Isatuximab-VRd regimen (N=263) or the standard VRd regimen alone (N=181). The Induction phase of the treatment consisted of 4 cycles, with each cycle lasting 6 weeks. Patients in the Isatuximab-VRd Group received Isatuximab 10 mg/kg IV weekly during Cycle 1, then every 2 weeks for subsequent cycles. Patients received subcutaneous Bortezomib (1.3 mg/m²) on specified days, along with oral Lenalidomide (25 mg daily for 14 days) and Dexamethasone (20 mg on specified days). The VRd group received the same VRd regimen without Isatuximab. Following the induction phase, both groups continued treatment with a regimen consisting of Lenalidomide and Dexamethasone. For the Isatuximab-VRd group, Isatuximab was given every 2 weeks, transitioning to monthly administration starting at Cycle 18. The median patient age was 72 years and treatment groups were well balanced. The Primary endpoint of the trial was Progression-Free Survival (PFS), assessed by an Independent Review Committee in accordance with International Myeloma Working Group criteria. Secondary endpoints included Complete Response (CR) or better, Minimal Residual Disease (MRD) negativity in patients achieving a Complete Response, assessed at a sensitivity level of 10⁻⁵ using Next-Generation Sequencing, Overall Survival (OS) and Quality of Life measures.
The results from the interim analysis at a median follow-up of 59.7 months demonstrated a significant improvement in PFS for the Isatuximab-VRd group compared to the VRd group. The 60-month PFS was estimated at 63.2% in the Isatuximab-VRd group versus 45.2% in the VRd group (HR=0.60; P<0.001), indicating a 40% reduction in the risk of disease progression or death for the Isatuximab group. Approximately 75% of patients in the Isatuximab-VRd group achieved a Complete Response or better compared to 64.1% in the VRd group (P=0.01). Higher rates of MRD negativity (55.5% vs. 40.9%; P=0.003) were also observed in the Isatuximab group. The safety profile of the Isatuximab-VRd combination mirrored that of established regimens, with no new safety signals identified. Incidences of serious adverse events were comparable between the two groups, though a slight increase in infections and neutropenia was noted with the addition of Isatuximab.
In conclusion, the results from the IMROZ trial clearly indicate that the addition of Isatuximab to the VRd regimen provides significant benefits in terms of Progression-Free Survival and Response Rates in patients with newly diagnosed multiple myeloma who are ineligible for transplantation, addressing an important unmet need. Further follow-up and analyses will continue to elucidate the long-term benefits and safety of this promising therapeutic strategy.
Isatuximab, Bortezomib, Lenalidomide, and Dexamethasone for Multiple Myeloma. Thierry Facon, M.D., Meletios-Athanasios Dimopoulos, M.D., Xavier P. Leleu, et al. for the IMROZ Study Group. Published June 3, 2024. DOI: 10.1056/NEJMoa2400712.
