Hematogenix Flow Cytometry Assay Named in the Label Behind the Accelerated Approval of Zenbexus

What Table 4 says

Response in EXCALIBER-RRMM was assessed by an independent review committee using International Myeloma Working Group 2016 criteria, and the MRD footnote attached to the efficacy table names the assay and its threshold. Eighty-five of 207 patients on the iberdomide triplet reached MRD-negative complete response at any time, against 44 of 213 on daratumumab, bortezomib and dexamethasone. Among patients who reached complete response, 89% in the iberdomide arm and 83% in the control arm were MRD negative, which puts most of the gap between the arms in how many patients got to complete response at all.

The population the number came from

The 420 patients in the primary efficacy population had a median age of 68, with 22% carrying del(17p), t(4;14) or t(14;16) and 11% with extramedullary disease. Two-thirds had received one prior line. Patients refractory to a prior anti-CD38 antibody or to prior bortezomib were excluded, and only 4% had received an anti-CD38 antibody at all, which is why the label states plainly that data are limited in patients who have had or are refractory to that class. The drug carries a boxed warning for embryo-fetal toxicity and for serious venous and arterial thromboembolism, and reaches patients only through the ZENBEXUS REMS program.

One cell in 100,000, counted in marrow

A threshold of 10-5 means one myeloma cell detected among 100,000 nucleated marrow cells. The IMWG criteria the reviewers applied, published by Shaji Kumar of Mayo Clinic and more than 30 co-authors in Lancet Oncology in 2016, built MRD-negative response categories around residual tumor cells found in the bone marrow by flow cytometry or gene sequencing, on the reasoning that conventional serum and urine paraprotein measurement plus routine marrow assessment had become too insensitive for modern response rates. Running that read to a single standard across a global trial is central-laboratory work: identical antibody panels, identical cell acquisition targets and identical gating at every participating site.

Hematogenix president and CEO Hytham Al-Masri called the label citation "a meaningful validation of the precision and scientific rigor our laboratory brings to this new era of innovative therapies," and said myeloma treatment "is moving toward MRD negativity as a defining measure of treatment success." The company runs the same next-generation flow platform for acute myeloid leukemia and chronic lymphocytic leukemia MRD.

Twelve to zero at ODAC

An advisory committee cleared the path for this kind of application on April 12, 2024, when FDA's Oncologic Drugs Advisory Committee met to weigh MRD as an endpoint in myeloma trials, including the timing of assessment, which patients it applies to and how such trials should be designed. The committee voted 12 to 0 that the available evidence supports MRD as a basis for accelerated approval. Zenbexus, the first cereblon E3 ligase modulator approved in myeloma, is the drug that turned that vote into a marketing authorization, and its continued approval may depend on verification of clinical benefit in confirmatory trials.

Why This Matters to the APO|APE Reader

Hematogenix closed its own announcement with a disclaimer stating that the release "does not constitute an endorsement by Bristol Myers Squibb," and nothing in the approved indication requires an MRD test before a physician prescribes the drug. The commercial weight of a named assay sits upstream, with sponsors choosing which laboratory measures the endpoint that decides a registrational trial, and it will sit there again when the confirmatory data arrive. For hospital flow laboratories, the practical effect of the label is a reference standard: a threshold, a technology and a vendor now written into an approved product's efficacy table.