FDA Grants Accelerated Approval to Retifanlimab for Locally Advanced Merkel Cell Carcinoma

The FDA has granted retifanlimab-dlwr (Zynyz) accelerated approval for the treatment of patients with metastatic or recurrent, locally advanced merkel cell carcinoma (MCC). The prescribing label comes with warnings for immune-mediated adverse events (AEs), infusion-related reactions, allogeneic hematopoietic stem cell transplant complications, and embryo-fetal toxicity. Continued approval will be contingent upon confirmatory trials.^1,2

Data from the POD1UM-201 trial (NCT03599713) supported the FDA’s decision. In this open-label, multiregional, single-arm study, patients with metastatic or recurrent, locally advanced MCC who had not undergone previous systemic therapy for advanced disease (n = 65), achieved an overall response rate of 52% (95% CI, 40%-65%), as determined by independent central review using RECIST 1.1.¹

In addition, complete responses were observed in 12 patients (18%) and partial responses were seen in 22 patients (34%). Among those who responded to treatment, 75% achieved a duration of response (DOR) lasting at least 6 months, and 62% experienced a 12-month DOR or longer.

In this trial, serious AEs included fatigue, arrythmia, and pneumonitis. AEs necessitated treatment discontinuation in 11% of patients. The most common AEs in patients receiving retifanlimab included fatigue, musculoskeletal pain, pruritus, diarrhea, rash, pyrexia and nausea.

“More than [one]-third of patients with MCC present with regional or distant metastases, which are associated with high rates of mortality,” Shailender Bhatia, MD, of University of Washington and Fred Hutchinson Cancer Center, stated in a news release. “The approval of Zynyz offers health care providers another first-line treatment option against MCC that can result in durable responses in patients with metastatic disease, and I look forward to having Zynyz in our treatment portfolio for these difficult-to-treat patients.”

Retifanlimab is a PD-1 inhibitor which is administered intravenously over 30 minutes every 4 weeks. The injection is 500 mg/20 mL and comes in a single-dose vial. The agent should be diluted with either 0.9% sodium chloride injection, USP or 5% dextrose injection, USP to a final concentration between 1.4 mg/mL to 10 mg/mL; it should be administered via polyvinylchloride (PVC) and di-2-ethylhexyl phthalate (DEHP), polyolefin copolymer, polyolefin with polyamide, or ethylene vinyl acetate infusion bags. It should not be administered via an intravenous push nor should it be administered as a bolus injection.²

No dose reduction is recommended for retifanlimab; however, it should be withheld for grade 3 immune-mediated AEs, and permanently discontinued for grade 4 immune-mediated AEs, or grade 3 immune-mediated AEs which are not reduced through corticosteroids.

Patients about to receive retifanlimab need to be taught about immune-related AEs, infusion-related reactions, and the risk of embryo-fetal toxicity.

Incyte, the manufacturers of retifanlimab, have stated that eligible patients in the US who are prescribed retifanlimab may be able to obtain personalized support and financial assistance through their IncyteCARES program. Those seeking those services are advice to visit www.incytecares.com or call 1-855-452-5234 ¹

References

1. Incyte announces FDA approval of Zynyz (retifanlimab-dlwr) for the treatment of metastatic or recurrent locally advanced merkel cell Carcinoma (MCC). News release. March 22, 2023. Accessed March 22, 2023. https://bwnews.pr/40rKNKF
2. Zynyz. Prescribing information. Incyte Corporation; 2023. Accessed March 22, 2023.https://www.zynyz.com/pdf/prescribing-information.pdf