Ewings Sarcoma Treatment, CLR 131, Receives Additional Orphan Drug Designation

July 9, 2018
Krista Rossi

CLR 131 was granted an orphan drug designation by the US Food and Drug Administration (FDA) for the treatment of Ewing’s sarcoma, a rare pediatric cancer.

CLR 131, a phospholipid drug conjugate (PDC) product candidate, was granted an additional orphan drug designation by the US Food and Drug Administration (FDA) for the treatment of Ewing’s sarcoma, a rare pediatric cancer.

“Ewing’s sarcoma is the second most common bone malignancy among children and adolescents and there are limited treatment options for patients who relapse or become refractive to therapy,” said John Friend, MD, chief medical officer of Cellectar, in a recent statement. “The ODD for Ewing’s sarcoma represents another important milestone for our CLR 131 pediatric program as we work to bring new options to patients suffering from rare cancers.”

Previously, CLR 131 was granted orphan drug designations for rhabdomyosarcoma and neuroblastoma as well as rare pediatric disease designations.

CLR 131 is characterized by its function to deliver cytotoxic radiation directly and selectively to cancer cells. Clinical trials evaluating the drug’s use for opportunities in hematology, pediatric tumors, and head and neck cancers are being carried out in phase 1 and phase 2 trials.

Specifically, a phase 1, open-label, dose escalation clinical study is currently underway to evaluate CLR 131 for the potential treatment of pediatric patients with Ewing’s sarcoma, rhabdomyosarcoma, osteosarcoma, neuroblastoma, high grade glioma, lymphomas, selected solid tumors, and malignant brain tumors.

Cellectar Biosciences, the company behind CLR 131, received FDA clearance to initiate an accelerated phase 1 trial, designed to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of CLR 131 in pediatric patients with these cancer types.

The trial will include an estimated enrollment of 30 participants between the ages of 2 and 21 who have a Karnofsky score higher or equal to 60%. The Karnofsky score classifies patients’ level of functional impairment by grading scores from 100 to 0, with lower Karnofsky scores correlating with a worse survival rate for most serious illnesses. The indication allows physicians to assess a patient's ability to survive chemotherapy for cancer.

The estimated primary completion date is September 2020.

As the second most common bone malignancy among children and adolescents, Ewing’s sarcoma occurs in about 3 cases per 1 million per year in children younger than age 20. Due to its high rates of relapsed and refractor disease behavior, the need for new treatment options is only further highlighted, emphasizing the significance of the potential CLR 131 treatment.


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