On June 28, 2023, Cellectar Biosciences, Inc. announced data from its ongoing study of iopofosine I 131 in multiple myeloma as presented at the Society of Nuclear Medicine and Molecular Imaging (SNMMI) Annual Meeting. The data included that from 72 patients, of which 64 were evaluable, with relapsed or refractory multiple myeloma (MM), in which iopofosine I 131 demonstrated an overall response rate (ORR) of 23%, a clinical benefit rate (CBR) of 70% and a disease control rate (DCR) of 92%. The data highlighted the outcomes from two dose levels (<60 mCi vs.

>60 mCi total administered dose) across these highly refractory patients. The focus of the Company’s presentation at SNMMI was on 28 patients that received the optimal dose of >60 mCi total administered dose (TAD). These patients were predominately either post-BCMA immunotherapy, triple-class refractory (defined as refractory to immunomodulatory agents, proteasome inhibitors and CD 38 targeted monoclonal antibodies) or quad-class refractory (defined as triple-class plus refractory to either nuclear export inhibitors or BCMA targeted therapies).

Key data in the patients receiving >60 mCi TAD included: Overall response rate (ORR) of 32%, Clinical benefit rate (CBR) of 75%, Disease control rate (DCR) of 85.7%. Key data in patient subsets that were highly refractory and received >60 mCi TAD included: 46% ORR in triple-class refractory patients, median PFS of 3.4 months (n=18); 50% ORR in quad-class refractory patients, PFS evaluation ongoing (n=6); 50% ORR in post BCMA relapsed or refractory patients, median PFS of 3.3 months (n=6). The most commonly observed treatment emergent adverse events were consistent with those previously reported: cytopenias including Grade 3 or 4 thrombocytopenia (62.5%), anemia (62.5%), neutropenia (62.5%), and decreased white blood cell count (50%).

Importantly, patients did not experience off-target treatment emergent adverse events of neuropathy, arrythmia, cardiovascular events, bleeding, ocular toxicities, changes in renal function, alterations in liver enzymes, or infusion-site reactions. Patients in the trial received up to four (4), approximately 15-minute IV infusions of iopofosine over three (3) months, with doses given 14 days apart in each cycle with a maximum of two (2) cycles. Low-dose dexamethasone 40 mg weekly (20mg in patients = 75), was provided for up to 12 weeks.