FDA Issues Complete Response Letter for Cosibelimab in Cutaneous Squamous Cell Carcinoma

The FDA has issued a complete response letter for Checkpoint Therapeutics’ cosibelimab biologic license application. Cosibelimab was being reviewed by regulators to treat patients with metastatic or locally advanced cutaneous squamous cell carcinoma who are not candidates for curative surgery or radiation.

The FDA cited issues related to an inspection of Checkpoint’s third-party contract manufacturing organization. The letter did not state any concerns about the clinical data package, safety, or labeling for the approvability of cosibelimab.

Cutaneous squamous cell carcinoma is a common form of skin cancer. It is not usually life-threatening, but patients with advanced or metastatic disease have limited treatment options. The cancer affects about 1 million people each year, and about 40,000 cases will become advanced. Cosibelimab is an PD-L1–blocking antibody that is designed to inhibit the interaction between PD-L1 and its receptors PD-1 and B7.1. This enables anti-tumor CD8+ T-cells to target the cancer cells.

Data from a pivotal phase 1 trial were published in October in the Journal for ImmunoTherapy of Cancer. In the trial, objective response was observed in 37 of 78 patients with a mean follow-up of 15.4 months. Common treatment-emergent adverse events were fatigue, rash, and anemia. Eighteen participants (23.1%) experienced immune-related adverse events. No treatment-related deaths were reported.

In July 2023, the company reported longer-term data of cosibelimab. In patients with local advanced cutaneous squamous cell carcinoma, treatment with cosibelimab resulted in a 55% objective response rate and 23% of patients had complete response rate. In patients with metastatic cutaneous squamous cell carcinoma, 50% of those treated with cosibelimab had an objective response rate and 13% complete response rate.

Updated safety data across 247 patients treated with cosibelimab in all cohorts remain consistent with those previously reported, with only 2% of patients experiencing a severe immune-related adverse event and less than 1% of patients discontinuing treatment due to an immune-related adverse event of any severity.

“Unlike PD-1 inhibitors, cosibelimab does not interrupt the body’s PD-1/PD-L2 pathway, which we believe results in cosibelimab’s low rates of autoimmunity,” James Oliviero, president and CEO of Checkpoint said in a press release.