Retifanlimab Immunotherapy Receives FDA Approval for Merkel Cell Carcinoma

For adults with metastatic (stage 4) or recurrent locally advanced Merkel cell carcinoma (MCC), the medicine retifanlimab-dlwr (Zynyz, Incyte Corporation), an immunotherapy, received accelerated FDA (US Food and Drug Administration) approval on 22 March 2023.

Retifanlimab-dlwr (Zynyz) is an antibody developed for Merkel cell carcinoma that blocks programmed death receptor-1 (PD-1). This is the first FDA approval for retifanlimab.

Retifanlimab is immunotherapy number 3 to receive FDA approval for Merkel cell carcinoma. Avelumab was approved in 2017 and pembrolizumab in 2018 for patients in the same situation.

Merkel Cell Carcinoma: A Brief Overview

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer arising from nerve cells in the skin. It develops when Merkel cells in the epidermis, the skin’s upper layer, grow and multiply uncontrollably. These cells detect mechanical stimuli such as touch and pressure. MCC usually develops on sun-exposed skin and can grow rapidly.

MCC symptoms include:

• A rapidly growing, firm, shiny, red or purple skin nodule, usually painless.
• Swelling in the nearby or affected lymph nodes.

Treatment for Merkel cell carcinoma depends on cancer stage, overall health and other factors. Options include surgery, radiotherapy, chemotherapy and immunotherapy. Early diagnosis and treatment matter for life expectancy and quality of life.

Merkel cell carcinoma (MCC) is a very rare skin cancer, with around 0.7 cases per 100,000 people each year. Its incidence increases with age, and it is more common after age 50 and in people with fair skin. Statistics indicate that its five-year recurrence rate ranges from approximately 30% to 60%. Regular checks and follow-up after treatment are therefore important.

FDA Approval Based on the PODIUM-201 Study

Retifanlimab’s safety and efficacy were assessed in PODIUM-201, an open-label, multiregional, single-arm trial of 65 people with metastatic or recurrent locally advanced MCC who had not received systemic treatment for advanced disease.

The main efficacy outcomes were objective response rate and duration of response, assessed by an independent central review committee using RECIST v1.1.

• The objective response rate was 52% (95% CI: 40, 65), and the complete response rate was 18%.
• Twenty-six patients (76%) had responses lasting ≥ 6 months, and 21 patients (62%) had responses lasting ≥ 12 months.

The most common adverse effects, affecting 10% or more, were fatigue, musculoskeletal pain, itching, diarrhoea, rash, fever and nausea. Serious adverse effects occurred in 22% of those receiving retifanlimab-dlwr.

The recommended retifanlimab-dlwr dose is 500 mg every 4 weeks by intravenous infusion over 30 minutes, until progression, unacceptable toxicity or a maximum of 24 months.

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Retifanlimab’s developer, Incyte Corporation, is a US-based biopharmaceutical company founded in 1991. It focuses on innovative medicines for serious, life-threatening diseases such as cancer and autoimmune disorders. Its work spans biological target discovery, drug development and clinical research.

Incyte is particularly known for JAK inhibitors developed for cancer treatment. Jakafi (ruxolitinib) is used for blood disorders such as myelofibrosis and polycythaemia vera. The company also researches immunotherapeutic agents and other targeted molecules.