Phase 2b study of iobenguane I 131 shows promise for rare neuroendocrine tumors

The registrational phase 2b trial designed to evaluate iobenguane I 131 injection for the treatment of malignant and recurrent pheochromocytoma or paraganglioma met its primary endpoint, according to the drug’s manufacturer.

Iobenguane I 131 (Azdera, Progenics Pharmaceuticals) is a novel radiotherapeutic candidate in development to treat patients with malignant and recurrent pheochromocytoma or paraganglioma. Both rare neuroendocrine tumors for which there are currently no FDA–approved therapeutics, pheochromocytoma is located in the adrenal glands, whereas paraganglioma is located outside of the adrenal glands.

Researchers of the open-label, multicenter study — which was conducted under a special protocol assessment agreement with the FDA — evaluated the safety and efficacy of two therapeutic doses of iobenguane I 131 administered 3 months apart in 68 evaluable patients.

The primary endpoint included the proportion of patients who achieved a 50% or greater reduction of all antihypertensive medication for at least 6 months. Study protocol indicated the primary endpoint was met if the lower limit of the two-sided 95% CI was above 10%.

In total, 17 patients experienced a 50% or greater reduction of all antihypertensive medication for at least 6 months, with the lower limit of the 95% CI at 16.15% and the upper limit at 36.52%.

In addition, 92.2% of patients who received at least one iobenguane I 131 therapeutic dose achieved partial response (23.4%) or stable disease (68.8%).

The most common adverse events included nausea, thrombocytopenia, anemia, fatigue, leukopenia and neutropenia.

“The positive data from this trial are clinically meaningful and provide compelling evidence for the use of Azdera to treat malignant and/or recurrent pheochromocytoma and paraganglioma,” study researcher Daniel Pryma, MD, associate professor of radiology and radiation oncology and chief of the division of nuclear medicine and clinical molecular imaging at Perelman School of Medicine at University of Pennsylvania, said in a company-issued release. “Without any approved therapeutics in the United States for these rare and devastating life-threatening tumors, patients face a poor prognosis and few options. The tumor response data — in particular for the patients who received two doses — along with the adverse event profile from this trial, suggest that Azdera has the potential to be a true breakthrough in addressing these difficult-to-treat patients.”

The FDA has granted breakthrough therapy, orphan drug and fast track designations to iobenguane I 131.

“We intend to move quickly to complete our new drug application submission by mid-2017, as these topline results underscore the potential of Azdera in this ultra-orphan indication,” Mark Baker, CEO of Progenics, said in the release. “We are grateful to the patients and investigators who participated in this trial, and are committed to bringing a new treatment option to this rare cancer population.”