Cellectar Biosciences announced promising initial results from its CLOVER-2 Phase 1 clinical trial, showing that iopofosine I 131 doubled progression-free survival in pediatric patients with relapsed/refractory high-grade glioma compared to historical controls. The radioligand therapy achieved an average of 5.4 months progression-free survival in patients receiving a minimum of 55 mCi total dose, significantly exceeding the reported median of 2.25 months for this patient population.
Clinical Efficacy Demonstrates Meaningful Survival Benefit
The trial enrolled 14 pediatric patients diagnosed with aggressive brain tumors including diffuse midline gliomas, ependymomas, diffuse intrinsic pontine gliomas, diffuse hemispheric gliomas, and anaplastic ependymomas. All seven patients receiving the minimum 55 mCi dose experienced disease control and achieved an average overall survival of 8.6 months, ongoing, compared to the historical median of 5.6 months.
Particularly encouraging results emerged from three patients who received additional dosing cycles with a minimum of four total infusions. These patients demonstrated an average progression-free survival of 8.1 months and overall survival of 11.5 months, ranging from 4.9 to 14.9 months and ongoing. Two of these patients achieved an objective response according to Response Assessment in Pediatric Neuro-Oncology criteria.
"We are highly encouraged with these initial findings from the CLOVER-2 trial in pediatric patients with high-grade glioma. Iopofosine I 131 observed extended PFS and survival, indicating potential signs of clinical efficacy for the treatment of these deadly cancers," said Jarrod Longcor, chief operating officer of Cellectar Biosciences.
Favorable Safety Profile Supports Continued Development
Iopofosine I 131 demonstrated a well-tolerated safety profile consistent with the company's previously reported data. Notably, patients experienced no cardiovascular, renal, or liver toxicities, and no peripheral neuropathy or significant bleeding events. The safety profile reflected selective targeting of tumor sites with clinically negligible off-target effects outside the hematologic system.
The most frequently reported treatment-emergent adverse events were hematologic in nature, including thrombocytopenia, neutropenia, and anemia. These events were predictable and manageable, with all patients recovering from cytopenias.
Trial Design and Regulatory Status
The ongoing Phase 1b trial evaluates iopofosine I 131 in children, adolescents, and young adults with relapsed/refractory high-grade glioma at multiple sites across the United States and Canada. The study employs two dosing cohorts: one receiving 20 mCi/m² doses separated by 14 days for two cycles with an optional third cycle, and another receiving 10 mCi/m² doses for three cycles with an optional fourth cycle.
The trial aims to determine therapeutic activity defined as progression-free survival and overall survival, assess antitumor activity through tumor volume reduction, and identify the recommended Phase 2/3 dose. Iopofosine I 131 has received Rare Pediatric Drug and Orphan Drug Designations for pediatric high-grade glioma, positioning Cellectar to potentially receive a Pediatric Review Voucher upon FDA approval.
Phospholipid Drug Conjugate Platform Technology
Iopofosine I 131 represents Cellectar's proprietary Phospholipid Drug Conjugate delivery platform designed to provide targeted delivery of iodine-131 radioisotope. The FDA has granted the compound Breakthrough Therapy designation along with six Orphan Drug, four Rare Pediatric Drug, and two Fast Track Designations across various cancer indications, reflecting its potential to address significant unmet medical needs in oncology.
