Elranatamab Phase 3 PFS Win Faces OS Proof and Payer Price Squeeze

Pfizer's ELREXFIO Achieves Primary Endpoint in Relapsed/Refractory Multiple Myeloma

Pfizer Inc. announced positive topline results from the Phase 3 MagnetisMM-32 study, demonstrating that ELREXFIO (elranatamab) monotherapy met its primary endpoint of progression-free survival (PFS) in adults with relapsed or refractory multiple myeloma (RRMM). These patients had previously received anti-CD38 therapy and lenalidomide. ELREXFIO showed a statistically significant and clinically meaningful reduction in the risk of disease progression or death compared to investigator’s choice of three standard-of-care regimens. At the interim analysis, median PFS was not yet reached, with an estimated 68% PFS at 18 months and over 75% of patients remaining progression-free. The safety profile was consistent with previous findings, with no new safety signals identified.

• ELREXFIO demonstrated robust efficacy, achieving a statistically significant and clinically meaningful reduction in the risk of disease progression or death. At the time of analysis, median progression-free survival (PFS) had not yet been reached, and an estimated 68% of patients were progression-free at 18 months, with more than 75% of patients not experiencing disease progression or death overall.
• The Phase 3 MagnetisMM-32 study rigorously evaluated ELREXFIO as monotherapy against a broad and clinically relevant benchmark. It compared ELREXFIO to investigator’s choice of three established standard-of-care regimens: elotuzumab, pomalidomide and dexamethasone (EloPd); pomalidomide, bortezomib and dexamethasone (PVd); or carfilzomib and dexamethasone (Kd) in a challenging patient population.
• The study enrolled 523 adults across 26 countries, focusing on patients with relapsed or refractory multiple myeloma whose disease had progressed after receiving anti-CD38 therapy and lenalidomide. The safety profile of ELREXFIO was consistent with its known profile, with infection prophylaxis measures helping to mitigate risk. Pfizer plans to submit these data to global health authorities and present detailed results at a future medical meeting.

Addressing the Unmet Need in Post-Anti-CD38, Lenalidomide RRMM

Recent literature underscores that despite therapeutic advances, relapsed/refractory multiple myeloma (RRMM) remains incurable with almost all patients eventually relapsing, and survival remains poor in heavily pretreated and biologically high-risk subgroups. Key unmet needs center on populations refractory to multiple drug classes, ultra-high-risk genetics, and extramedullary or leukemic disease where no uniform standard of care exists.

• Double-class and triple-class refractory disease, including lenalidomide- and anti-CD38 monoclonal antibody-refractory patients: Longitudinal retrospective data report median overall survival (OS) of 22.3 and 11.6 months for double-class refractory and triple-class refractory patients, respectively. Prospective registry and electronic health record analyses in patients previously treated with lenalidomide and an anti-CD38 monoclonal antibody report median progression-free survival (PFS) of 5.2 (95% CI 3.7-6.7), 4.4 (3.5-5.6) and 5.3 months (4.8-6.0) and median OS of 19.3 (15.8-26.1), 14.2 (11.0-16.9) and 23.1 months (19.0-28.6), with shorter PFS and OS in lenalidomide- and anti-CD38 monoclonal antibody-refractory versus not refractory to both, and in triple-class refractory versus non-triple-class refractory patients. Retreatment with previously used classes is part of standard of care, with bortezomib and lenalidomide having the highest retreatment rates, highlighting need for novel efficacious therapies with varying novel mechanisms of action.

• Ultra-high-risk cytogenetics and other high-risk biology: Patients with two or more high-risk cytogenetic abnormalities defined as del(17p), t(4;14), t(14;16), or 1q21 gain or amplification (1q+) have median PFS and OS of 22.9 months and 71.5 months with consolidation with autologous hematopoietic stem cell transplantation, and median PFS of 15.6 months and median OS of 28.0 months for three high-risk abnormalities. These patients may benefit from earlier use of newer treatment modalities, such as chimeric antigen receptor T cell therapy and bispecific antibodies.

• Extramedullary disease and plasma cell leukemia with high tumor burden: Patients triple-exposed to immunomodulatory drugs, proteasome inhibitors, and anti-CD38 monoclonal antibodies have poor prognosis with no established standard treatment, while extramedullary disease or secondary plasma cell leukemia often display high tumor cell proliferation. Plasma cell leukemia cohorts show high-risk cytogenetics in 87% and extramedullary disease in 47%, with OS for primary versus secondary disease of 13 vs. 3.5 months and 5-year survival of 11% for the whole cohort.

• Heavily pretreated, BCMA-exposed, and frail real-world populations requiring bridging and tolerable salvage: Real-world elranatamab cohorts were heavily pretreated (91% triple-class refractory, 49% penta-refractory), with 49% previously exposed to BCMA-targeted therapies and only 22% meeting eligibility for MagnetisMM-3 cohort A, achieving overall response rate of 65%, median PFS and OS of 4.3 and 14.6 months. Cytotoxic salvage such as cyclophosphamide, etoposide, and dexamethasone after median of four lines achieved overall response rate of 52% with median PFS and OS of 6.2 and 10.9 months, with 23% bridged to autologous stem cell transplantation or chimeric antigen receptor T cell therapy.

• Renal impairment and organ dysfunction excluded from pivotal trials: BCMA-directed chimeric antigen receptor T-cell therapy in patients with renal impairment defined as creatinine clearance of less than 45 mL/min showed comparable efficacy with higher rates of immune effector cell-associated neurotoxicity syndrome (60% vs. 19%) and infections (44% vs. 20%), addressing suitability in patients who do not meet trial inclusion criteria due to suboptimal organ function.

ELREXFIO's Superior PFS in MagnetisMM-32 Against Standard of Care

BCMA-directed CAR-T cell therapies have been compared to standard of care (SOC) regimens for MM in early relapse in the phase III trials KarMMa-3 and CARTITUDE-4, respectively. Idecabtagene vicleucel and ciltacabtagene autoleucel are BCMA-directed CAR-T cell therapies that have been compared to standard of care (SOC) regimens for MM in early relapse in those trials. Both studies demonstrated a significantly improved in response rates, depth of response, and progression-free survival compared to SOC.

BCMA-targeted bispecific antibodies are advancing into earlier lines with direct SOC comparisons. Teclistamab combined with daratumumab is approved in the United States for patients with ≥ 1 prior LOT based on results of the phase 3 MajesTEC-3 trial, in which teclistamab-daratumumab significantly improved progression-free and overall survival versus SOC in patients with 1 to 3 prior LOTs. In heavily pretreated relapsed/refractory multiple myeloma (RRMM), overall response rates of 63 and 61% were observed with teclistamab and elranatamab, respectively, while a real-world propensity score-matched study reported the median time to the next treatment did not differ significantly between elranatamab and teclistamab (11.0 vs 12.3 months; p = 0.394), and the 3-year overall survival rates were similar (58.8% vs 59.7%; p = 0.077).

Lenalidomide-sparing triplet regimens have also been compared in the absence of head-to-head trials. Results showed that treatment with KdD decreases the risk of progression or death versus DVd (HR 0.64; 95% confidence interval (CI): 0.46-0.90). In a large real-world propensity score-matched cohort, median TTNT was longer with DRd than with DVd (32.6 vs. 17.7 months; hazard ratio [HR] 0.71; 95% confidence interval [CI], 0.62-0.81; p < 0.0001) and five-year OS was higher with DRd than with DVd (58.4% vs. 52.3%; HR 0.71; 95% CI, 0.59-0.86; p = 0.0003).

ELREXFIO's Position in the BCMA-Directed RRMM Landscape

Elranatamab is a bispecific antibody that engages BCMA on MM and CD3 on T cells. Other BCMA × CD3 bispecific antibodies trialled for relapsed or refractory multiple myeloma include teclistamab and linvoseltamab, which redirect T cells to multiple myeloma cells.

ELREXFIO's Confirmatory Data Solidifies Role in Heavily Pretreated Myeloma

The recent positive topline results for ELREXFIO (elranatamab) monotherapy in relapsed or refractory multiple myeloma (RRMM) mark a pivotal moment for patients who have progressed after anti-CD38 therapy and lenalidomide. This patient population represents a significant challenge in clinical practice, often having exhausted multiple lines of treatment and facing limited options with conventional therapies. The demonstration of a statistically significant and clinically meaningful reduction in the risk of disease progression or death, with an impressive 18-month progression-free survival rate of 68%, underscores the profound impact of this B-cell maturation antigen (BCMA)-CD3 bispecific antibody.

ELREXFIO's mechanism, engaging BCMA on myeloma cells and CD3 on T cells, redirects the body's immune system to target and eliminate cancer cells. This confirmatory Phase 3 data is crucial for transitioning ELREXFIO from accelerated to full regulatory approval, which will be instrumental in expanding its availability and solidifying its position in the competitive RRMM landscape. While other BCMA-directed bispecific antibodies and CAR-T cell therapies exist, ELREXFIO's robust monotherapy efficacy in this specific, heavily pretreated cohort provides a strong argument for its use as a standalone option.

However, the path forward is not without considerations. The competitive environment is intense, with other BCMA-targeting agents like teclistamab and linvoseltamab also demonstrating efficacy, sometimes with numerically higher response rates or differential activity against BCMA mutations. Furthermore, the safety profile common to BCMA bispecifics, including cytokine release syndrome, neurotoxicity (ICANS), and elevated infection rates, necessitates careful patient selection and expert management, potentially impacting broader access. The evolving understanding of optimal treatment sequencing, particularly between CAR-T and bispecific antibodies, also presents a strategic challenge, as prior exposure to one class may influence the efficacy of the other. Future research exploring ELREXFIO in combination regimens, which have shown promising early results, will be key to further enhancing its utility and addressing the persistent unmet needs in multiple myeloma.