Long-Term Data Show Improved CR Rates for Cosibelimab in Advanced CSCC

James Oliviero

Long-term data demonstrated that treatment with cosibelimab (formerly CK-301) improved complete response (CR) rates over time in patients with locally advanced or metastatic cutaneous squamous cell carcinoma (CSCC) in a phase 1 trial (NCT03212404).¹

At the January 2023 data cutoff, patients with locally advanced CSCC (n = 31) experienced an overall response rate (ORR) of 55% (95% CI, 36%-73%) with a CR rate of 23%. At the March 2022 data cutoff, the ORR and CR rate for this population were 55% (95% CI, 36%-73%) and 10%, respectively. Updated data showed response was ongoing in 82% of patients, and the median duration of response (DOR) was not reached (NR).

In those with metastatic CSCC (n = 78), updated data at the January 2023 data cutoff demonstrated the ORR was 50% (95% CI, 39%-62%) with a CR rate of 13%. At the November 2021 data cutoff, the ORR and CR rate for this population were 47% (95% CI, 36%-59%) and 8%, respectively. Updated findings showed response was ongoing in 69% of patients, and the median DOR was NR.

Detailed findings are expected to be presented at an upcoming medical conference.

“We are excited to see the substantial increases in the rate of patients experiencing a CR of their CSCC tumors with further cosibelimab treatment in both our locally advanced and metastatic pivotal trials,” James Oliviero, president and chief executive officer of Checkpoint Therapeutics, stated in a news release.

In March 2023, the FDA accepted a biologics license application seeking the approval of cosibelimab for the treatment of patients with metastatic or locally advanced CSCC, based on prior results from the phase 1 trial. The Prescription Drug User Fee Act goal date is January 3, 2024.²

The study enrolled patients at least 18 years of age with histologically confirmed unresectable metastatic CSCC that was not amenable to surgery.³ Patients were required to have an ECOG performance status of 0 or 1 and a life expectancy of at least 3 months.

Key exclusion criteria included prior treatment with an immune checkpoint inhibitor; active, suspected, or documented history of autoimmune disease; and concurrent immunosuppressive doses of steroids.

Intravenous cosibelimab was given at 800 mg every 2 weeks⁴ until confirmed CR, disease progression, intolerable toxicity, or clinical deterioration followed by post-treatment follow-up.

ORR per independent review committee assessment according to RECIST v1.1 criteria was the primary end point. Secondary end points included DOR and safety.

Regarding safety, updated data for enrolled patients treated with cosibelimab across all cohorts of the ongoing study (n = 247) were consistent with previous findings. Two percent of patients experienced severe immune-related adverse effects (irAEs), and less than 1% of patients discontinued treatment due to an irAE.¹

“We believe cosibelimab’s strong efficacy and response durability are driven by its unique two-fold mechanism of action in which cosibelimab binds to PD-L1 with sustained high target tumor occupancy to reactivate the body’s T-cell anti-tumor response, with the addition of a functional Fc domain to activate the body’s natural killer immune cells to induce antibody-dependent cell-mediated cytotoxicity of tumor cells, resulting in a powerful one-two punch to eradicate tumors,” Oliviero added. “We expect this dual mechanism of action to benefit not just immunocompetent patients, but also the large number of difficult-to-treat patients with immunosuppressive conditions or taking immunosuppressive medications who continue to suffer poor outcomes with currently available treatments.”

References

1. Checkpoint Therapeutics announces cosibelimab longer-term results demonstrating substantial increases in complete response rates in advanced cutaneous squamous cell carcinoma. News release. Checkpoint Therapeutics. July 27, 2023. Accessed July 28, 2023. https://ir.checkpointtx.com/news-events/press-releases/detail/102/checkpoint-therapeutics-announces-cosibelimab-longer-term
2. Checkpoint Therapeutics announces FDA filing acceptance of biologics license application for cosibelimab in metastatic or locally advanced cutaneous squamous cell carcinoma. News release. Checkpoint Therapeutics, Inc. March 2, 2023. Accessed July 28, 2023. https://ir.checkpointtx.com/news-events/press-releases/detail/96/checkpoint-therapeutics-announces-fda-filing-acceptance-of
3. Phase 1 study of CK-301 (cosibelimab) as a single agent in subjects with advanced cancers. ClinicalTrials.gov. Updated March 4, 2022. Accessed July 28, 2023. https://classic.clinicaltrials.gov/ct2/show/NCT03212404
4. Clingan PR, Brungs D, Arnold S, et al. Efficacy and safety of cosibelimab, an anti-PD-L1 antibody, in patients with metastatic cutaneous squamous cell carcinoma. J Clin Oncol. 2022;40(suppl 16):9537. doi:10.1200/JCO.2022.40.16_suppl.9537