Cellectar Biosciences

Overview

Cellectar develops phospholipid ether–based drug conjugates (PDCs) for targeted cancer therapy, with an emphasis on radioconjugates. The platform is designed to selectively target cancer cells and cancer stem cells by exploiting lipid raft–rich membrane regions to enable intracellular delivery while limiting exposure to healthy tissues. The company pursues both radiotherapeutic and non-radiotherapeutic payloads through internal programs and collaborations.

Core platform

• Phospholipid Ether Drug Conjugate (PDC) delivery platform (PLE-based).
• Targets lipid rafts to enter cancer cells, traffic to peri-nuclear organelles, and bypass lysosomal degradation.
• Payload versatility includes radioconjugates (I-131, I-125, Ac-225, At-211) and non-radiative payloads (small molecules, peptides, oligonucleotides).

Lead programs

1. CLR 125 (iodine-125, Auger emitter)

• Modality: Radioconjugate using iodine-125 (Auger emitter). Some sources reference CLR 131 as an alternative designation.
• Preclinical: Well tolerated in animal studies; activity observed in multiple solid tumor models, with emphasis on triple-negative breast cancer.
• Clinical status: Phase 1b dose-finding study planned.
• Rationale: Auger electrons deliver very short-range DNA damage within tumor cells.

2. CLR 225 (actinium-225)

• Modality: Alpha-emitting radioconjugate.
• Preclinical: Activity seen in pancreatic, colorectal, and breast cancer models; favorable biodistribution and tumor uptake; well tolerated in animal models.
• Clinical status: Prepared to initiate a Phase 1 imaging and dose-escalation safety study, pending additional financing.

3. iopofosine I-131 (iodine-131)

• Modality: Beta-emitting radioconjugate.
• Regulatory highlights: FDA Breakthrough Therapy Designation for relapsed/refractory Waldenström’s macroglobulinemia (WM) as of June 4, 2025; Fast Track and Orphan Drug designations in multiple jurisdictions; EMA PRIME designation for WM and MM; EMA SAWP advised a CMA filing could be acceptable for post-BTKi WM patients.
• Clinical data (CLOVER program):
  • CLOVER-WaM (pivotal WM study): 55 patients enrolled; major response rate (MRR) 58.2% (95% CI 44.5–75.8%; p < 0.0001); overall response rate (ORR) 83.6%; disease control 98.2%; median duration of response not reached at 11.4 months; 76% progression-free at ~8 months follow-up.
  • Safety: Treatment-related adverse events (TRAEs) led to discontinuation in 4.6% of the safety population. Common Grade ≥3 hematologic events included thrombocytopenia (81.5%), neutropenia (66.2%), anemia (47.7%), and leukopenia (27.7%). No treatment-related deaths reported.
  • Other CLOVER data: CLOVER-1 (Phase 2) in relapsed/refractory B-cell malignancies showed safety and signals of efficacy; ongoing studies include Phase 1/2 programs in multiple myeloma, CNS lymphoma, and non-Hodgkin’s lymphoma, as well as pediatric evaluations.

Clinical pipeline & development pathways

• CLOVER program structure: CLOVER-1 (Phase 2, selected B-cell malignancies); CLOVER-2 (Phase 1a pediatric); CLOVER-2b (Phase 1b pediatric high-grade glioma); CLOVER-WaM completed enrollment and reported topline data in January 2024.
• Regulatory strategy for iopofosine I-131 in WM: FDA End-of-Phase-2 (EOP2) meeting in March 2025 outlined a path toward accelerated and full approval, including a Phase 3 confirmatory, comparator-controlled trial with progression-free survival as the primary endpoint. Progression to a confirmatory trial requires ongoing enrollment and funding.
• Additional oncology indications pursued through internal programs and collaborations, including non-radiotherapeutic PDCs and exploration of other alpha- and beta-emitting isotopes (e.g., astatine-211, lead-212 in preclinical studies).

Collaborations and manufacturing

• Orano Med: Collaboration initiated in 2018 to evaluate Lead-212 PDCs; work pivoted toward other alpha emitters due to Lead-212 logistics.
• LegoChem Bio: Collaboration (July 2021) to combine LegoChem’s linker-toxin platform with the PDC delivery vehicle.
• IntoCell: Collaboration to identify potent cytotoxic payloads for PDCs.
• Manufacturing and supply:
  • Finished PRC suppliers include AtomVie and SpectronRx.
  • Isotope sourcing partners include NorthStar Medical Radioisotopes (Ac-225) and Ionetix Corporation (Ac-225 and At-211).
  • iopofosine drug product is manufactured under cGMP, with stability and expiry dating extended to support distribution; AtomVie is a primary supplier.
  • The company uses a collaborative outsourcing model for isotope sourcing and manufacturing.

Technology and imaging

• Mechanism: PLE vehicle binds lipid rafts, enters cancer cells, and delivers payloads to peri-nuclear regions while avoiding lysosomal degradation.
• Imaging: CLR 124 and CLR 1502 have demonstrated tumor uptake in imaging studies. Co-administration strategies (e.g., CLR 124 with iopofosine) support combined imaging/therapy approaches in preclinical models.

Market and indications

• Target indications include Waldenström’s macroglobulinemia (WM), multiple myeloma (MM), subtypes of non-Hodgkin’s lymphoma (NHL), and pediatric cancers such as neuroblastoma, gliomas, Ewing’s sarcoma, and osteosarcoma, as well as head and neck cancers and various sarcomas.
• The company emphasizes rare and orphan indications with high unmet medical need.

Regulatory status and initiatives

• iopofosine I-131 holds FDA Breakthrough Therapy designation (WM), Fast Track designation (MM, DLBCL, LPL/WM), EMA PRIME designation (WM/MM), and Orphan Drug designations in the EU and U.S. The EMA’s SAWP provided guidance on a potential CMA filing for post-BTKi WM.
• Regulatory planning includes pathways for accelerated approval and requirements for confirmatory trials and post-approval commitments.

Financial highlights

• Research and development expenses:
  • 2025: $11,499,000
  • 2024: $26,136,000
• The company has communicated the need for additional financing or strategic partnerships to support late-stage development, including a potential Phase 3 trial for iopofosine I-131 in WM.

Key takeaway

Cellectar’s PDC platform is built to deliver multiple payload types selectively to cancer cells. The pipeline centers on three lead PDCs (CLR 125, CLR 225, and iopofosine I-131), with iopofosine advanced in clinical development and regulatory discussions for WM. The company advances radiotherapeutic programs while partnering to expand non-radiative payload options and to secure isotope and manufacturing supply.