Iopofosine I-131 With EBRT Appears Safe in Head and Neck Cancer


Preliminary research suggests that lopofosine I-131 in combination with external beam radiation is safe and tolerable in patients with relapsed or refractory head and neck cancer.

Preliminary research suggests that lopofosine I-131 in combination with external beam radiation (EBRT) is safe and tolerable in patients with relapsed or refractory head and neck cancer, according to a press release by Cellectar Biosciences.1

Iopofosine is a small molecule PDC that is mean to deliver iodine-131, a radioisotope, to cancer cells. It is meant to improve efficacy and safety. Patients with head and neck cancer who received EBRT typically receive 60-70 Grays of EBRT given as 2-3 Gy daily doses over 6 weeks. Long-term adverse events (AEs) are common. A reduction in dose may help to alleviate some of these AEs. In addition to head and neck cancer, the agent is being investigated in relapsed or refractory Waldenstrom’s macroglobenemia.

“Iopofosine offers a novel investigational approach for patients with difficult to treat tumors such as head and neck cancer. The ability to potentially reduce the total external beam radiation doses is meaningful and we look forward to continue exploring iopofosine’s potential as a combination treatment in this indication,” said Justine Yang Bruce, MD, a medical oncologist with the Wisconsin Head and Neck Cancer, in a press release.

The results come from a phase 1 study of the agent with an estimated enrollment of 24 participants and an estimated completion date of January 2022 (NCT04105543). The primary end point is AEs up to 18 weeks. Secondary end points include median radiation time, median number of dose delays due to toxicity, overall response rate, change in swallow function, quality of life, and change in stimulated salivary flow.2

During the study, all patients will receive iopofosine in combination with EBRT at varying dose levels. Dose escalation will proceed as long as there are no limiting toxicities at each level. After maximum tolerated dose is found, a dose expansion phase will proceed.

The safety analysis comes from the part A safety portion of the trial. This included the first 4 participants who received 2 doses of the agent intravenously on the first dose on day 1 followed by a second dose on day 8. 

“These preliminary study results support the potential promise of iopofosine. We are pleased that the early phase of the University of Wisconsin study has demonstrated good tumor uptake of iopofosine at the planned doses as well as safety of this unique treatment approach in Head & Neck cancer patients,” said John Friend, chief medical officer of Cellectar,, in a press release. “We remain cautiously optimistic that iopofosine in combination with external beam radiation may offer improved outcomes for patients in this highly challenging to treat disease.”

In order to participate in the study, patients must have confirmed head and neck cancer, have undergone previous curative intent therapy, at least one evaluable lesion, an ECOG score of 0 or 1, a life expectancy of at least 6 months, adequate renal function, and agree to use appropriate birth control measures. Patients who have a recurrent tumor recommended for surgical resection, thyroid cancer, known hypersensitivity to iodine, chemotherapy or major surgery within 4 weeks of first dose, have an ongoing infection, or poorly controlled chronic obstructive pulmonary disease are not eligible to participate. 

The study is currently recruiting in Wisconsin.

1.Preliminary data with iopofosine I-131 in combination with external beam radiation suggests safety and tolerability in relapsed or refractory head and neck cancer. News release. Cellectar Biosciences. September 22, 2021. Accessed September 22, 2021.
2.CLR 131 combined with radiation for head and neck cancer. Accessed September 22, 2021.
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