The US Food and Drug Administration (FDA) has issued a Complete Response Letter (CRL) for Checkpoint Therapeutics' PD-L1 inhibitor cosibelimab, delaying its potential approval for advanced skin cancer. The regulatory setback stems from issues with a third-party contract manufacturer rather than concerns about the drug's safety or efficacy profile.
The news triggered a significant market response, with Checkpoint's shares plummeting nearly 45%. The company's financial position adds complexity to the situation, having ended the third quarter with under $2 million in cash reserves, though a recent $10 million funding round in October provides some breathing room.
Clinical Efficacy and Therapeutic Potential
Cosibelimab has shown promising results in treating metastatic or locally advanced cutaneous squamous cell carcinoma (cSCC) patients who are not candidates for curative surgery or radiation. Clinical trials demonstrated an impressive 55% overall response rate in locally advanced cSCC, including 23% complete responses. Patients with metastatic disease showed similarly encouraging results, achieving a 50% overall response rate with 13% complete responses.
Innovative Mechanism of Action
The drug's effectiveness is attributed to its unique dual mechanism of action. Cosibelimab binds to PD-L1 with sustained high target tumor occupancy, stimulating T-cell responses while incorporating a functional Fc domain to activate natural killer (NK) immune cells. Unlike traditional PD-1 inhibitors, the drug preserves the PD-1/PD-L2 pathway, potentially resulting in lower autoimmunity rates.
Market Positioning and Competition
If approved, cosibelimab would enter a market currently dominated by established treatments including Merck's Keytruda (pembrolizumab) and Regeneron's Libtayo (cemiplimab). Checkpoint Therapeutics aims to position cosibelimab as a cost-effective alternative, supported by efficacy data suggesting comparable performance to existing options.
Path Forward
James Oliviero, President and CEO of Checkpoint Therapeutics, expressed confidence in addressing the FDA's concerns, stating, "As the only deficiencies relate to the FDA's inspection of our third-party contract manufacturing organization, we believe we can address the feedback in a resubmission to enable marketing approval in 2024."
The drug, originally licensed from the Dana-Farber Cancer Institute in 2015, represents an important potential addition to the treatment landscape for cSCC patients. Checkpoint Therapeutics has committed to working closely with both their manufacturer and the FDA to facilitate the resubmission process and bring cosibelimab to patients.
