Cellectar Enrolls First Patient in CLR 125 Clinical Trial for Triple Negative Breast Cancer

The Phase 1b trial will evaluate the company's Auger-emitting radioconjugate for refractory TNBC patients.

Apr. 14, 2026 at 12:35pm

Got story updates? Submit your updates here. ›

A translucent, ghostly X-ray image reveals the intricate internal structure of a breast tumor, with a faint glow suggesting the targeted radiation therapy working to dissolve the cancer cells.A novel radioconjugate therapy aims to selectively target and damage triple negative breast cancer tumors from the inside.Florham Park Today

Cellectar Biosciences, Inc. has enrolled the first patient in a Phase 1b clinical trial of its proprietary Auger-emitting radioconjugate CLR 125 for the potential treatment of triple negative breast cancer (TNBC). The open-label, dose-escalation study will evaluate three dose levels and dosing regimens of CLR 125 in approximately 15 patients per treatment arm.

Why it matters

TNBC is an aggressive subtype of breast cancer with limited treatment options beyond chemotherapy. With a high recurrence rate and poor prognosis, there is a critical need for innovative, targeted therapies to improve outcomes for TNBC patients.

The details

CLR 125 is Cellectar's Auger-emitting radioconjugate that incorporates iodine-125 to achieve intracellular delivery and direct DNA-level damage in tumor cells. In preclinical studies, CLR 125 showed selective tumor uptake and statistically significant activity in TNBC models with no observed end-organ or hematologic toxicity.

  • The Phase 1b clinical trial is currently enrolling patients.
  • Additional study sites are being activated in Q2 2026.

The players

Cellectar Biosciences, Inc.

A late-stage clinical biopharmaceutical company focused on the discovery and development of drugs for the treatment of cancer.

James Caruso

President and chief executive officer of Cellectar.

Got photos? Submit your photos here. ›

What they’re saying

“Treating the first patient in this Phase 1b trial is a significant milestone for Cellectar and for those impacted by triple negative breast cancer, a condition still defined by a profound lack of targeted therapies.”

— James Caruso, President and chief executive officer

What’s next

The Phase 1b clinical trial will continue to enroll patients, and Cellectar plans to provide updates on dosimetry, safety, and efficacy throughout 2026.

The takeaway

Cellectar's CLR 125 represents a promising targeted therapy for the treatment of triple negative breast cancer, a difficult-to-treat cancer subtype with limited options beyond chemotherapy.