Understanding the Mechanism and Toxicity Profile of Iberdomide in Multiple Myeloma

Surbhi Sidana, MD, associate professor of medicine at Stanford University and chair of the American Society of Hematology (ASH) Committee on Communication, outlines the clinical pharmacology, operational logistics, and adverse event management strategies for clinicians implementing the iberdomide (Zenbexus), daratumumab (Darzalex), and dexamethasone (Iber-Dd) triplet in relapsed/refractory multiple myeloma. Iberdomide is a novel cereblon E3 ligase modulator (CELMoD), a next-generation drug class engineered to bind the cereblon target with significantly higher affinity and specificity than traditional immunomodulatory drugs (IMiDs) like lenalidomide (Revlimid) or pomalidomide (Pomalyst). This enhanced potency provides robust anti-myeloma activity while potentially reducing off-target toxicities. Sidana says that from a daily operational standpoint, iberdomide shares similar practical logistics with familiar oral IMiD therapies, making integration into community oncology workflows straightforward.

Although physicians have developed experience with the adverse events associated with daratumumab, combining it with iberdomide introduces specific hematologic and infectious considerations that necessitate vigilant monitoring during initial treatment cycles. Hematologic toxicity is the primary adverse event associated with the addition of iberdomide. Grade 3 or 4 neutropenia occurs at a significantly higher rate with Iber-Dd than with standard daratumumab, bortezomib (Velcade), and dexamethasone (DVd). According to Sidana, this neutropenic signal is heavily concentrated within the first 2 to 3 treatment cycles before stabilizing. Clinicians should maintain frequent laboratory monitoring during these early cycles, utilizing temporary dose holds and initiating granulocyte colony-stimulating factor (G-CSF) support, such as filgrastim or biosimilars, as indicated.

Infectious risks also require proactive clinical management, as clinical trial data demonstrated an increased incidence of grade 3 or 4 pneumonia in the Iber-Dd arm relative to the DVd control arm. Care teams must immediately hold treatment upon any early signal or clinical suspicion of infection, aggressively initiate targeted antimicrobial therapy, and resume the triplet regimen only after full clinical recovery.

Despite these hematologic and infectious considerations, Sidana points out that Iber-Dd provides a notable neurotoxicity advantage over historical standards. Replacing the proteasome inhibitor bortezomib with oral iberdomide results in a substantially lower incidence of treatment-emergent peripheral neuropathy. By avoiding chronic neuropathic pain while proactively managing early neutropenia and infection risks, clinicians can safely maximize the therapeutic benefit of this potent oral CELMoD regimen.