FDA Rejects Replimune Melanoma Treatment RP1

The Food and Drug Administration declined to grant approval to RP1, a genetically engineered virus intended to treat advanced melanoma, the company Replimune reported. One-third of the 140 patients in the company's clinical trial experienced tumor shrinkage or disappearance while receiving RP1 in combination with the immunotherapy Opdivo.

Doctors who participated in the trial described the decision as a setback for patients with limited options. "It was devastating news," said Trisha Wise-Draper, a dermatologist at the University of Cincinnati who had patients enrolled in the trial. Eric Whitman, medical director of the Atlantic Health System's oncology service, added that the treatment could have affected as many as 2,000 patients.

Melanoma is the fifth most commonly diagnosed cancer in the United States, with about 112,000 new cases each year. The American Cancer Society projects that about 8,500 people will die from melanoma this year. If the treatment performed as observed in the trial, Whitman said as many as 2,500 of those patients could potentially be saved.

The FDA had warned Replimune in July that the trial design risked denial of approval. The single-arm study lacked a control group receiving only an approved melanoma treatment for comparison. All patients in the trial had already stopped responding to Opdivo or similar immunotherapies before receiving the RP1 combination.

Replimune argued that assigning patients to a control arm with Opdivo alone would have been unethical given their prior lack of response. "Having a control arm would have been unethical," Wise-Draper said. Some of her patients responded extremely well to RP1 and no longer have evidence of melanoma.