Bristol Myers Squibb ZENBEXUS Wins FDA Accelerated Approval for Multiple Myeloma

Bristol Myers Squibb ZENBEXUS has become the first cereblon E3 ligase modulator, or CELMoD, ever cleared by the U.S. Food and Drug Administration, after regulators granted accelerated approval on August 13, 2026, to the oral therapy iberdomide in combination with daratumumab and hyaluronidase-fihj and dexamethasone, known as the ZDd regimen, for adult patients with multiple myeloma who have received at least one prior line of therapy, including a proteasome inhibitor and an immunomodulatory agent. The clearance allows physicians to reach for the new class of protein degrader as early as a patient’s first relapse, a notable shift from later-line positioning that has defined prior myeloma drug launches.

The approval marks a milestone for Bristol Myers Squibb ZENBEXUS and for the company’s broader targeted protein degradation platform, a research effort the company has pursued for more than two decades. ZENBEXUS is designed to degrade the transcription factors Ikaros and Aiolos more potently than earlier-generation immunomodulatory drugs, producing both a direct anti-myeloma effect and an immune-stimulatory response. The FDA action was supported by Breakthrough Therapy designation and was reviewed under the agency’s Project Orbis initiative, which permits simultaneous evaluation by regulators in multiple countries.

Cristian Massacesi, chief medical officer and head of development at Bristol Myers Squibb, said the clearance “represents meaningful progress for patients living with multiple myeloma” and called it the arrival of an entirely new treatment class. Company leadership framed the approval as validation of a research bet that spans three distinct degrader modalities: cereblon E3 ligase modulators, ligand-directed degraders, and degrader antibody conjugates, all built on the same underlying protein-degradation science.

The regulatory decision rests on results from the Phase 3 EXCALIBER-RRMM trial, which compared Bristol Myers Squibb ZENBEXUS, daratumumab and hyaluronidase-fihj, and dexamethasone against daratumumab, bortezomib, and dexamethasone in patients with relapsed or refractory multiple myeloma. At a median follow-up of 16 months, the ZDd arm produced a minimal residual disease-negative complete response in 41% of patients, versus 21% in the comparator arm, a statistically significant difference that the company says represents the first myeloma approval built on MRD-negative complete response data.

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Bristol Myers Squibb ZENBEXUS Clinical Trial Data and Regulatory Pathway

EXCALIBER-RRMM enrolled 939 patients in total, with the primary efficacy population for the MRD endpoint drawn from the first 420 patients randomized, 207 to the Bristol Myers Squibb ZENBEXUS-containing arm and 213 to the comparator arm. Eligible participants had received one to two prior lines of anti-myeloma therapy and had progressive disease at enrollment. The study was designed around dual primary endpoints, MRD negativity and progression-free survival, with the PFS analysis still maturing; secondary endpoints include overall survival, overall response rate, and durability of MRD-negative status. Full trial results are expected later this year as the progression-free survival data mature.

Sagar Lonial, the trial’s lead investigator and chief medical officer of the Winship Cancer Institute at Emory University, described the result as the anticipated arrival of a new therapeutic class that could meaningfully change outcomes for patients. Heather Cooper Ortner, president and chief executive officer of the International Myeloma Foundation, said the expanded options matter most in the community setting, where the majority of myeloma care is actually delivered, and framed the approval as renewed hope for patients approaching their first relapse.

Discontinuations tied to adverse reactions on Bristol Myers Squibb ZENBEXUS occurred in 7.8% of patients on the ZDd regimen, a rate the company characterizes as consistent with expectations for the combination. Neutropenia occurred in 90.2% of treated patients and infections in 78.9%, though both led to relatively few treatment discontinuations. The most frequent adverse reactions affecting at least one-fifth of patients included upper respiratory tract infection, fatigue, musculoskeletal pain, pneumonia, diarrhea, motor dysfunction, rash, sleep disorder, hypogammaglobulinemia, COVID-19, and constipation.

Bristol Myers Squibb ZENBEXUS Safety Profile and Prescribing Requirements

Bristol Myers Squibb ZENBEXUS carries boxed warnings for embryo-fetal toxicity and for serious venous and arterial thromboembolism, and the drug is contraindicated in pregnancy. Because of the embryo-fetal risk, the therapy is only available through a restricted distribution program, ZENBEXUS REMS, requiring certified prescribers, enrolled patients, negative pregnancy tests before initiation, and ongoing contraception monitoring throughout treatment and for four weeks afterward. Anti-thrombotic prophylaxis is recommended given the elevated clotting risk observed in the trial population.

Serious adverse reactions occurred in 58.3% of Bristol Myers Squibb ZENBEXUS-treated patients, and fatal adverse reactions were reported in 10 patients, or 4.9% of the treated population, with sepsis the only fatal event to recur in more than one patient. Physicians are advised to monitor complete blood counts throughout treatment, to consider prophylactic anti-infective medication, and to adjust dosing in patients with reduced kidney function, reducing the ZENBEXUS dose for patients with an estimated glomerular filtration rate below 30 mL/min/1.73 m2 who are not on dialysis.

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Bristol Myers Squibb ZENBEXUS Pipeline and Protein Degradation Platform

The Bristol Myers Squibb ZENBEXUS clearance is not an isolated event inside the company’s oncology pipeline. Mezigdomide, a second investigational CELMoD, is already under FDA review in combination with carfilzomib and dexamethasone, with a Prescription Drug User Fee Act target action date of May 13, 2027. ZENBEXUS itself is also being studied further in the EXCALIBER Maintenance trial, extending the drug’s evaluation beyond the relapsed or refractory setting that supported this week’s clearance. Bristol Myers Squibb remains the only company to have successfully developed and commercialized protein degrader agents for multiple myeloma, a franchise that helped establish the current standard of care in a disease that still has no cure.

What the Bristol Myers Squibb ZENBEXUS Approval Means for Multiple Myeloma Patients

For patients facing a first relapse, the approval adds a novel-mechanism option to a treatment landscape historically built around proteasome inhibitors, immunomodulatory drugs, and CD38-directed antibodies used in various triplet combinations. Because ZDd pairs an oral CELMoD with daratumumab, a familiar and widely used anti-CD38 antibody, oncologists gain a new triplet built on a treatment backbone many practices already use in earlier lines. Bristol Myers Squibb said it offers patient support programs intended to help eligible patients access Bristol Myers Squibb ZENBEXUS once it becomes commercially available.

Because this is an accelerated approval, continued marketing authorization depends on the company verifying clinical benefit, specifically progression-free survival, in the confirmatory portion of the EXCALIBER-RRMM trial, which remains ongoing. Bristol Myers Squibb ZENBEXUS will need durable, mature survival data to convert this conditional clearance into full approval, a process the FDA and the company both describe as contingent on the trial’s continuing readout. Until then, the accelerated pathway gives patients with relapsed or refractory multiple myeloma earlier access to a therapy the company positions as the opening chapter of a broader degrader-based pipeline.

REGULATORY & APPROVAL SNAPSHOT

EXCALIBER-RRMM EFFICACY DATA (ZDd vs. DVd)