ASCO26: BMS Debuts Shining Multiple Myeloma Data

BMS's MeziKd Achieves 18-Month PFS in Relapsed Multiple Myeloma

Bristol Myers Squibb (BMS) presented positive Phase III data for its cereblon E3 ligase modulation drug, mezigdomide, in combination with carfilzomib and dexamethasone (MeziKd) at ASCO 2026. The SUCCESSOR-2 trial, involving patients with relapsed or refractory multiple myeloma (RRMM), demonstrated an 18-month progression-free survival (PFS) with MeziKd, significantly outperforming the 8.3 months achieved by carfilzomib and dexamethasone alone (Kd). This represents a 52% reduction in the risk of disease progression or death. MeziKd also showed superior overall response rates (80.2% vs 53.4%) and complete response or better (26.7% vs 8.9%), with a safety profile consistent with known regimens. BMS plans to discuss these results with regulatory authorities.

• The Phase III SUCCESSOR-2 trial showcased a significant improvement in progression-free survival (PFS) for MeziKd, achieving a median of 18 months compared to 8.3 months for the control arm (Kd). This translates to a substantial 52% reduction in the risk of disease progression or death for patients with relapsed or refractory multiple myeloma, highlighting the drug's potential to extend disease control in a challenging patient population.
• Beyond PFS, MeziKd demonstrated superior overall response rates (ORR) of 80.2% compared to 53.4% for Kd. Furthermore, the rate of complete response or better was notably higher with MeziKd at 26.7% versus 8.9% for Kd. These robust response metrics indicate a deeper and more frequent therapeutic effect, which is crucial for patients who have experienced prior relapses and are seeking more effective treatment options.
• The safety profile of MeziKd was found to be consistent with the known profiles of its components, with Grade 3-4 treatment-emergent adverse events (TEAEs) occurring in 83.7% of MeziKd patients versus 56.5% for Kd. Specific adverse events like neutropenia (61.1% vs 9.1%) and infections (34.0% vs 15.6%) were observed. BMS intends to present these promising results to regulatory authorities, signaling a potential path towards broader availability for patients needing additional treatment options.

Addressing the Unmet Needs in Relapsed/Refractory Multiple Myeloma

Multiple myeloma remains an incurable malignancy where drug resistance and disease relapse represent the primary obstacles to long-term disease control. Despite significant therapeutic advances including proteasome inhibitors, immunomodulatory drugs, and novel cellular therapies, patients with relapsed/refractory disease face increasingly complex treatment decisions and generally poorer clinical outcomes compared to newly diagnosed patients.

• Drug resistance development remains the most significant clinical challenge, with patients eventually becoming resistant to standard treatments despite high initial response rates with conventional therapies

• Treatment complexity has increased substantially due to numerous novel therapeutic options applied as combination regimens, requiring careful evaluation of multiple factors including prior treatments, associated toxicities, and patient-specific prognostic factors

• Sequential treatment resistance occurs even with newer BCMA-targeted therapies (CAR T-cell therapies and bispecific antibodies), where most patients ultimately experience relapse despite achieving deep and durable initial responses

• Multifactorial treatment selection challenges involve balancing prior response history, previously received drugs, adverse effects, patient comorbidities, biochemical markers for progression, disease dynamics, number of prior therapy lines, and underlying health status

• Limited understanding of resistance mechanisms at the molecular level, particularly regarding malfunctioning gene expression patterns and tumor microenvironment interactions that drive treatment failure

• Complex risk-benefit optimization requiring physicians to balance efficacy, toxicity, and cost considerations while pursuing shared decision-making with patients

• Prior therapy exposure complications where the majority of patients have received proteasome inhibitor and immunomodulatory agent combinations, potentially influencing the efficacy of subsequent novel treatments

• Inadequate patient assessment tools with traditional age and comorbidity evaluations proving insufficient compared to comprehensive geriatric assessments for treatment decision-making

• Palliative care integration challenges in determining appropriate timing for supportive care options in later-stage relapsed disease

MeziKd and Tecvayli Show Promising Data at ASCO 2026

Recent studies in relapsed or refractory multiple myeloma have demonstrated significant advances across multiple therapeutic approaches, including CAR-T cell therapies, bispecific antibodies, and combination regimens. These trials provide crucial insights into treatment efficacy, safety profiles, and optimal sequencing strategies for this challenging patient population.

Transforming RRMM Treatment: Earlier Use and Outpatient Administration

The treatment landscape for relapsed or refractory multiple myeloma has undergone significant transformation over the past five years, marked by the introduction of novel therapeutic classes and the establishment of new treatment standards. The approval of first-in-class agents including the nuclear export inhibitor selinexor and the BCMA antibody-drug conjugate belantamab mafodotin represented major advances for triple class refractory patients, though belantamab mafodotin's marketing license was subsequently withdrawn from US and European markets when the DREAMM-3 trial failed to demonstrate superiority over pomalidomide-dexamethasone despite showing a 41% response rate. Concurrently, BCMA-directed CAR-T therapies (idecabtagene vicleucel and ciltacabtagene autoleucel) have emerged as highly effective treatments, with recent data showing that free light chain suppression at day +28 post-CAR-T serves as an early biomarker for superior outcomes, correlating with markedly longer median progression-free survival (23.4 vs 4.1 months) and improved overall survival.

Anti-CD38 monoclonal antibodies have solidified their position as backbone therapies, with isatuximab receiving approval in combination with pomalidomide-dexamethasone and carfilzomib-dexamethasone based on robust phase 3 data. The IKEMA trial demonstrated that isatuximab plus carfilzomib-dexamethasone achieved a median progression-free survival that was not reached versus 19.15 months in the control group (hazard ratio 0.53). Meta-analyses of daratumumab-containing regimens across three phase 3 trials involving 1,497 patients confirmed consistent progression-free survival benefits regardless of baseline patient characteristics, previous therapy agents, or cytogenetic risk profiles, establishing these combinations as standard-of-care options for relapsed disease.

The emergence of bispecific antibodies represents the most recent paradigm shift, with elranatamab receiving first approval in the US in August 2023 for heavily pretreated patients. These T-cell engagers targeting BCMA, GPRC5D, and FcRH5 have demonstrated overall response rates of 60-70% in relapsed or refractory multiple myeloma with complete response rates of 30-40%. However, real-world outcomes data reveals sobering results for patients progressing on anti-CD38 therapy, with median progression-free survival of only 4.6 months and overall survival of 13.3 months from subsequent therapy initiation, highlighting the continued unmet medical need. The expanding therapeutic armamentarium now includes diverse combinations of proteasome inhibitors, immunomodulatory drugs, monoclonal antibodies, and novel agents, though this growth has introduced increasing complexity in treatment sequencing and selection, with real-world German registry data showing highly heterogeneous treatment patterns and the absence of clear standards of care in certain clinical scenarios.

Mezigdomide's Pivotal Data Reshapes Relapsed/Refractory Myeloma Outlook

The recent Phase III data for Bristol Myers Squibb's mezigdomide in relapsed or refractory multiple myeloma (RRMM) represents a pivotal moment for patients facing limited treatment options. In a disease where nearly all patients experience relapse and develop drug resistance, the need for novel, effective therapies is constant. Mezigdomide, a next-generation cereblon E3 ligase modulator (CELMoD), has demonstrated a significant leap forward, achieving an 18-month progression-free survival (PFS) when combined with carfilzomib and dexamethasone (MeziKd), compared to just 8.3 months for carfilzomib and dexamethasone alone. This 52% reduction in the risk of disease progression or death, alongside superior response rates, underscores its potential to redefine treatment expectations in this challenging setting.

This development is strategically important for several reasons. Mezigdomide's potent mechanism of action, distinct from traditional immunomodulatory drugs, positions it as a strong candidate for a new therapeutic backbone in RRMM. For Bristol Myers Squibb, it reinforces their leadership in multiple myeloma, offering a novel agent that can be integrated into existing treatment algorithms and potentially explored in earlier lines of therapy, a trend observed with other highly effective agents. The consistent safety profile reported is also a critical factor, as managing toxicities in heavily pretreated patients is paramount.

However, the path forward is not without its considerations. The multiple myeloma landscape is intensely competitive and rapidly evolving. New modalities like antibody-drug conjugates, bispecific T-cell engagers, and CAR-T cell therapies are continually emerging, each vying for a place in the treatment sequence. Mezigdomide will need to demonstrate sustained differentiation and long-term benefit to maintain its competitive edge. Furthermore, while initial safety data are promising, real-world use in a broader, more diverse patient population, often with significant comorbidities, may reveal a different safety profile or adherence challenges. Ultimately, despite these advancements, multiple myeloma remains incurable, and the eventual development of drug resistance is an ongoing challenge that will require continuous innovation beyond even this promising new agent.