Checkpoint Therapeutics Presents Extended Cosibelimab Results at ESMO 2024 for Advanced Cutaneous Squamous Cell Carcinoma

Checkpoint Therapeutics, Inc., a clinical-stage immunotherapy and targeted oncology company, recently presented extended data from its pivotal trial on cosibelimab. This anti-PD-L1 antibody targets advanced cutaneous squamous cell carcinoma (cSCC). The findings were shared during the European Society for Medical Oncology (ESMO) Congress 2024 in Barcelona, Spain.

The latest results from the trial highlight the deepening response rates over time. With an additional 16 months of follow-up data since the initial analysis, the objective response rates (ORRs) and complete response rates for cosibelimab have improved among 109 patients with advanced cSCC. Specifically, the ORR reached 54.8% for locally advanced cSCC and 50.0% for metastatic cSCC, with median follow-up durations of 24.1 and 29.3 months, respectively. The complete response rates were 25.8% and 12.8% for locally advanced and metastatic cSCC, respectively. Notably, the median durations of response (DOR) were not yet reached in either group, indicating sustained efficacy.

Regarding safety, cosibelimab demonstrated a manageable profile among 192 patients with advanced cSCC. The study recorded low rates of treatment-emergent adverse events (TEAEs) and severe immune-related adverse events (irAEs). Only 3.6% of patients experienced a grade 3 irAE, with no cases of grade 4 or higher irAEs. Moreover, there were no grade 3 or higher events of pneumonitis, colitis, hepatitis, nephritis, or endocrinopathies. Treatment discontinuations due to TEAEs occurred in 6.3% of the patients, with the primary reason being COVID-19 or COVID-19 pneumonia.

In December 2023, the U.S. FDA issued a complete response letter (CRL) for the cosibelimab Biologics License Application (BLA), citing issues identified during an inspection of Checkpoint’s third-party contract manufacturing organization (CMO). Checkpoint resubmitted the BLA in July 2024, addressing the CRL issues. The FDA accepted the resubmission and set a Prescription Drug User Fee Act (PDUFA) goal date of December 28, 2024.

Cutaneous squamous cell carcinoma (cSCC) is the second most common type of skin cancer in the U.S., with an estimated annual incidence of 1.8 million cases. Chronic ultraviolet exposure and immunosuppressive conditions are significant risk factors. While most cases are treatable with surgery, about 40,000 cases advance, and approximately 15,000 deaths occur annually. Advanced cSCC can cause severe functional and cosmetic issues, particularly when it affects the head and neck regions.

Cosibelimab stands out as a differentiated, high-affinity, fully-human monoclonal antibody of the IgG1 subtype. It directly binds to PD-L1, blocking its interaction with PD-1 and B7.1 receptors. This action removes the suppressive effects of PD-L1 on anti-tumor CD8+ T-cells, thereby restoring the cytotoxic T cell response. Additionally, cosibelimab’s functional Fc domain may enhance its efficacy through antibody-dependent cellular cytotoxicity (ADCC).

Checkpoint Therapeutics is dedicated to developing and commercializing novel treatments for solid tumor cancers. Beyond cosibelimab, the company is also advancing olafertinib, a third-generation EGFR inhibitor for non-small cell lung cancer with EGFR mutations. Founded by Fortress Biotech, Inc., Checkpoint Therapeutics is headquartered in Waltham, MA.