On November 9, 2020 Checkpoint Therapeutics, Inc. ("Checkpoint") (NASDAQ: CKPT), a clinical-stage immunotherapy and targeted oncology company, reported updated interim results from the ongoing global, open-label, multicohort Phase 1 clinical trial of its anti-PD-L1 antibody, cosibelimab, in patients with advanced cancers, including a cohort of patients with previously untreated high PD-L1 expressing advanced non-small cell lung cancer ("NSCLC") (Press release, Checkpoint Therapeutics, NOV 9, 2020, View Source [SID1234570317]). The updated interim results are being presented in a poster presentation at the Society for Immunotherapy of Cancer (SITC) (Free SITC Whitepaper) 35th Anniversary Annual Meeting being held virtually from November 9-14, 2020.

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"The single-agent activity of cosibelimab in NSCLC is compelling, with the observed 44.0% objective response rate and 10.3-month median progression-free survival comparing favorably to the datasets generated in similar subjects from the PD-(L)1 therapies available today. Based on the strength of these results, we intend to initiate a Phase 3 registration-enabling trial evaluating cosibelimab in combination with chemotherapy in first-line, metastatic NSCLC patients," said James F. Oliviero, President and Chief Executive Officer of Checkpoint. "The annual market for PD-(L)1 therapies in NSCLC is approximately $10 billion and growing. If approved, we believe cosibelimab could capture meaningful market share as a lower-priced alternative to therapies currently available, and NSCLC is an ideal follow-on to our planned first indication of cutaneous squamous cell carcinoma, for which top-line results from an on-going registration-enabling trial are expected in the second half of 2021."

Summary of NSCLC Data Presented at SITC (Free SITC Whitepaper):
The ongoing trial is evaluating cosibelimab administered as a fixed dose of 800 mg every two weeks or 1200 mg every three weeks. The NSCLC cohort includes patients with Stage IV NSCLC with high (tumor proportion score ≥50%) PD-L1 tumor expression as determined by immunohistochemistry, with no prior systemic treatment for advanced/metastatic NSCLC and no epidermal growth factor receptor ("EGFR") activating mutation or anaplastic lymphoma kinase ("ALK") translocation.

As of the interim analysis, 25 patients with NSCLC were enrolled and evaluable for efficacy by investigator assessment with at least one post-baseline tumor assessment or discontinued treatment prior. Tumor response assessments are summarized in the table below.

Tumor Response by RECIST 1.1 NSCLC
(n=25)
Best overall response, n (%)
Complete response -
Partial response 11 (44.0)
Stable disease 8 (32.0)
Progressive disease 2 (8.0)
Not evaluated/done1 4 (16.0)
Objective response rate, % (95% CI) 44.0 (24.4, 65.1)
Response ongoing, n (%) 4 (36.4)
Median duration of response, months
(min, max) 15.3
(5.7, 20.5+)
Median progression-free survival, months
(95% confidence interval) 10.3
(7.0, 13.7)
Objective response rate = best overall response of complete response or partial response divided by the number of evaluable patients. 1Represents patients who discontinued study without a post-baseline tumor assessment.

At the time of analysis, 123 patients with advanced cancers had been treated with cosibelimab and were evaluable for safety. Cosibelimab appeared to be safe and well-tolerated with a potentially favorable safety profile as compared to anti-PD-1 therapies currently available. The most common treatment-related adverse events ("TRAEs") included fatigue (n=19, 15.4%) and rash (n=17, 13.8%), with only 2 patients (1.6%) discontinuing treatment due to a TRAE. Grade ≥3 TRAEs occurred in only 6 patients (4.9%), most commonly anemia and fatigue (each n=2, 1.6%, grade 3 only).

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 SITC (Free SITC Whitepaper) website, www.sitcancer.org.

About Lung Cancer
According to the American Cancer Society, it is estimated that more than 228,000 Americans will be diagnosed with lung cancer in 2020, and non-small cell lung cancer accounts for 80-85% of all lung cancers. It is estimated that approximately 85% of lung cancer diagnoses in the United States are made when the disease is in the advanced stages.

About Cosibelimab
Cosibelimab (formerly referred to as CK-301) is a potential best-in-class, 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. 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 through sustained >99% target tumor occupancy to reactivate an antitumor immune response 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.