On this week’s episode of The CheckRare Brief, we discuss FDA’s approval of Zenbexus (iberdomide) to treat patients with multiple myeloma, the complete response letter issued to ITM-11 to treat patients with neuroendocrine tumors, and safety concerns about VYKAT XR for Prader-Willi syndrome (PWS).
The US Food and Drug Administration (FDA) granted accelerated approval to Bristol Myers Squibb’s iberdomide to treat patients with relapsed or refractory multiple myeloma on August 13, 2026. This treatment is a cereblon E3 ligase modulator (CELMoD), a new therapeutic class of drug. The approval is largely based on results from the EXCALIBER-RRMM clinical trial (NCT04975997), a two-stage, randomized, multicenter, open-label trial in adults with relapsed or refractory MM who had previously received one or two prior lines of therapy. Additionally, another new trend is the outcome measure of minimal residual disease, a departure from more traditional measures such as overall survival or progression free survival.
In other regulatory news, the FDA gave ITM a complete response letter (CRL) for ITM-11, a radioisotope (177-lutetium) attached to a peptide (edotreotide) that emits beta radiation towards targeted tumors, for neuroendocrine tumors. A phase 3 clinical trial showed the treatment to be significantly better than the control group, with a progression free survival of 24 months in the ITM-11 group versus 14 months in the control group. It appears that the FDA’s concern wasn’t the drug efficacy but about the manufacturing process. While it is a setback, it does not necessarily mean the drug has been rejected permanently. The company can address the FDA’s concerns and resubmit the application.
Finally, the Foundation for Prader-Willi Research are voicing concerns about VYKAT XR (diazoxide choline), a treatment approved in 2025 for children with Prader-Willi syndrome to address dysphagia. The main concern has to do with excessive fluid retention occurring in some patients that can lead to other serious adverse events, including cardiac and breathing concerns. The drug was approved last year to treat children with Prader-Willi syndrome to better control their hunger. These concerns highlight the importance of making physicians aware of the drug’s safety and efficacy in a real-world setting following drug approval.
Sources
FDA Grants Accelerated Approval For Multiple Myeloma Drug
ITM Receives Complete Response Letter for ¹⁷⁷Lu-edotreotide (ITM-11)
Prader-Willi Researchers Raise Concerns About the Safety of Approved Drug