On September 30, 2019 Checkpoint Therapeutics, Inc. ("Checkpoint") (NASDAQ: CKPT), a clinical-stage immuno-oncology biopharmaceutical company focused on the acquisition, development and commercialization of novel treatments for patients with solid tumor cancers, reported that positive interim results for cosibelimab, a potentially differentiated high affinity anti-PD-L1 antibody with functional Fc domain, were presented on Saturday, September 28th, at the European Society for Medical Oncology (ESMO) (Free ESMO Whitepaper) Congress 2019 in Barcelona, Spain (Press release, Checkpoint Therapeutics, SEP 30, 2019, View Source [SID1234539910]). The poster presentation provided updated interim efficacy and safety results from Checkpoint’s ongoing multicenter Phase 1 clinical trial, including expansion cohorts in cutaneous squamous cell carcinoma ("CSCC") and non-small cell lung cancer ("NSCLC"). Checkpoint continues to enroll CSCC patients to support an initial Biologics License Application ("BLA") submission for cosibelimab based on this ongoing clinical trial.

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"The compelling data presented at the ESMO (Free ESMO Whitepaper) Congress demonstrate strong and durable efficacy in CSCC and NSCLC and a potentially favorable safety profile as compared to the class of anti-PD-1 antibodies currently available," said James F. Oliviero, President and Chief Executive Officer of Checkpoint Therapeutics. "As the second deadliest skin cancer after melanoma, it is estimated that CSCC is responsible for approximately 7,000 deaths each year in the United States. We are confident that cosibelimab could soon provide CSCC patients with a highly effective and better tolerated treatment option as compared to the single anti-PD-1 therapy on the market today. With 25 CSCC patients enrolled to date, we intend to fully enroll the CSCC cohort in 2020 to potentially support an initial BLA filing, with the goal of positioning cosibelimab as a differentiated and lower-cost alternative to the approved therapy available today."

Summary of Interim Clinical Results

The Phase 1, open-label, multicenter trial (NCT03212404) is evaluating the safety, efficacy and pharmacokinetics of cosibelimab in checkpoint therapy-naïve patients with selected recurrent or metastatic cancers. Following dose escalation, the trial initiated multiple disease-specific expansion cohorts, including in CSCC and NSCLC, evaluating a fixed dose of 800 mg cosibelimab dosed intravenously every two weeks. As of August 5, 2019, 81 patients with diverse tumor types have been treated with cosibelimab.

Sixty-eight patients were evaluable for efficacy at the time of data cutoff, having at least two tumor assessments or discontinued treatment prior. Key efficacy results were as follows:

50% objective response rate ("ORR") in CSCC patients per RECIST v1.1. One patient achieved a complete response and six patients achieved partial responses. All seven responses (100%) are confirmed and ongoing with the longest duration at 11.4 months at the time of analysis.

40% ORR in first-line NSCLC patients with high (≥50%) expression of PD-L1 per RECIST v1.1. Ten patients achieved partial responses (eight confirmed and two pending confirmation). Nine of 10 responses (90%) are ongoing with the longest duration at 11 months at the time of analysis.
The best overall tumor response is shown below for all tumor types and the subgroup cohorts of CSCC and NSCLC.

Best Overall Tumor Response
by RECIST v1.1 All Tumor Types (n=68) CSCC
(n=14) NSCLC
(n=25)
Complete response, n (%) 1 (1.5) 1 (7.1) 0 (0.0)
Partial response, n (%) 18 (26.4) 6 (42.9) 10 (40.0)
Stable disease, n (%) 20 (29.4) 2 (14.3) 9 (36.0)
Progressive disease, n (%) 14 (20.6) 2 (14.3) 2 (8.0)
Not evaluated/done, n (%) 15 (22.1) 3 (21.4) 4 (16.0)
Overall response rate, % (95% CI) 27.9 (17.7, 40.1) 50.0 (23.0, 77.0) 40.0 (21.1, 61.3)
Response ongoing, n (%) 17/19 (89.5) 7/7 (100.0) 9/10 (90.0)
Median duration of response, months (min, max) Not reached
(0.1, 11.4) Not reached
(2.5, 11.4) Not reached
(0.1, 11.0)
Disease control rate, % 57.3 64.2 76.0
Objective response rate = best overall response of complete response or partial response divided by the number of evaluable patients; disease control rate = best overall response of complete response, partial response, or stable disease divided by the number of evaluable patients.

Cosibelimab appeared to be safe and well-tolerated with a potentially favorable safety profile as compared to the currently available anti-PD-1 therapies. Treatment‐related adverse events ("AEs") occurred in 48/81 (59%) patients, most commonly rash (n=11, 13.6%), fatigue (n=8, 9.9%), hypothyroidism (n=7, 8.6%), anemia (n=6, 7.4%), alanine aminotransferase increase, diarrhea, and infusion-related reaction (n=5, 6.2% each). Treatment‐related grade ≥3 AEs occurred in 5/81 (6%) patients, with only two patients (2.5%) discontinuing treatment due to a treatment-related AE.

A copy of the poster presentation is available on the Publications page of the Pipeline section of Checkpoint’s website, www.checkpointtx.com.

Additional information on the meeting can be found on the ESMO (Free ESMO Whitepaper) website, www.esmo.org.

About Cutaneous Squamous Cell Carcinoma
Cutaneous squamous cell carcinoma ("CSCC") is the second most common human cancer in the United States, with an estimated annual incidence of 700,000 cases. While most cases are localized tumors amenable to curative resection, approximately 8% of patients will experience a local recurrence, 5% of patients will develop nodal metastases, and an estimated 2% of patients will die from their disease. Ten-year survival rates are less than 20% for patients with regional lymph-node involvement. For those patients who develop distant metastases, the median survival time is estimated to be less than two years. In addition to being a life-threatening disease, CSCC causes significant functional morbidities and cosmetic deformities based on tumors commonly arising in the head and neck region and invading blood vessels, nerves and vital organs such as the eye or ear.

About Cosibelimab
Cosibelimab (formerly referred to as CK-301) is a high affinity, fully-human monoclonal antibody of IgG1 subtype that directly binds to programmed death ligand-1 (PD-L1) and blocks the PD-L1 interaction with the programmed death receptor-1 (PD-1) and B7.1 receptors. PD-L1 is an immune-inhibitory checkpoint molecule expressed on epithelial and vascular endothelial cells, as well as by a number of immune cells, and is utilized by tumor cells as an immune escape mechanism. Cosibelimab’s primary mechanism of action is based on the inhibition of the interaction between PD-L1 and its receptors PD-1 and B7.1, which removes the suppressive effects of PD-L1 on anti-tumor CD8+ T-cells to restore the cytotoxic T cell response. Cosibelimab is potentially differentiated from the currently marketed PD-1 and PD-L1 antibodies with a half-life that supports sustained >99% target tumor occupancy and the additional benefit of a functional Fc domain capable of inducing antibody-dependent cell-mediated cytotoxicity ("ADCC") for potential enhanced efficacy in certain tumor types.