On November 12, 2021 Checkmate Pharmaceuticals, Inc. (NASDAQ: CMPI) ("Checkmate"), a clinical stage biotechnology company focused on developing proprietary technology to harness the power of the immune system to combat cancer, reported the presentation of final clinical data from the Phase 1b study, CMP-001-001 (NCT02680184), of vidutolimod, an advanced generation Toll-like receptor 9 (TLR9) agonist, in combination with pembrolizumab or as a monotherapy at The Society for Immunotherapy of Cancer (SITC) (Free SITC Whitepaper) 36th Annual Meeting taking place on November 10-14, 2021 (Press release, Checkmate Pharmaceuticals, NOV 12, 2021, View Source [SID1234595445]).

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"Our ongoing investigation of vidutolimod indicates promising clinical activity for patients with PD-1 blockade-refractory melanoma," said Alan Fuhrman, interim President and Chief Executive Officer of Checkmate. Mr. Fuhrman added, "The RECIST response rates of 20% with vidutolimod monotherapy and 23.5% in combination with pembrolizumab are compelling, and the longer duration of response of 25.2 months in combination with PD-1 blockade provides a strong rationale for our ongoing development program."

Final analysis: phase 1b study investigating intratumoral injection of Toll-like receptor 9 agonist vidutolimod ± pembrolizumab in patients with PD-1 blockade–refractory melanoma (Abstract #16269; poster #950; NCT02680184)

On Friday, November 12, 2021, during the Virtual Poster Hall Exhibit from 7:00am – 8:30pm ET, John M. Kirkwood, M.D., Director of the Melanoma and Skin Center at UPMC Hillman Cancer Center and Usher Professor of Medicine in the Division of Dermatology and Translational Science at the University of Pittsburgh School of Medicine, is presenting late-breaking final clinical data from the Checkmate-sponsored clinical trial of vidutolimod, either in combination with pembrolizumab or as monotherapy.

Final clinical data from the trial demonstrated that the combination of vidutolimod and pembrolizumab was well tolerated and resulted in an ORR of 23.5% according to Response Evaluation Criteria in Solid Tumors (RECIST) v1.1. The study treatment induced deep and durable systemic antitumor responses in patients with melanoma who previously progressed on anti-PD-1 treatments.

"PD-1 blockade therapy has significantly improved clinical outcomes for many patients with cancer, although most patients still experience disease progression on anti−PD-1-therapy. Therapeutic alternatives for these patients are a large gap in the field, and critically needed," said Dr. Kirkwood. "With clinically meaningful tumor regression we have observed both in injected and noninjected lesions, vidutolimod’s systemic effects hold the potential to enhance responsiveness and overcome resistance to immune checkpoint inhibitors. In addition, the substantially improved duration of response with the combination of vidutolimod and anti-PD-1 therapy provides strong rationale for further development of vidutolimod in combination with PD-1 blockade."

Data were presented on 159 patients receiving combination therapy with vidutolimod and pembrolizumab. Two formulations of vidutolimod were evaluated, either polysorbate 20 at 0.01% (PS20, n=98) or x PS20 at 0.00167% (n=61). Based on the results, vidutolimod PS20 A 10 mg (schedule A) was selected as the Recommended Phase 2 Dose (RP2D) and schedule. Data were also presented on 40 patients who received vidutolimod monotherapy.

Key highlights from these clinical data as of the data cut-off of August 17, 2021 include:

Vidutolimod in combination with pembrolizumab

The best ORR by RECIST v1.1 in patients who received vidutolimod PS20 A+ pembrolizumab was 23.5% (95% CI 15.5-33.1), including 7.1% (7/98) of patients with a complete response.
Four additional patients who continued study therapy beyond initial disease progression achieved a partial response.
Vidutolimod PS20 A 10 mg (schedule A) was selected as the RP2D.
The Kaplan-Meier estimate for median duration of response was 25.2 months (95% CI8.7- not estimable [NE] in the 23 RECIST v1.1 responders).
Among responding patients, non-injected target lesions regressed by a similar magnitude to injected target lesions.
The most common treatment-related adverse events were chills, pyrexia, fatigue, nausea, vomiting and injection site pain.
Vidutolimod as a monotherapy

In the 40 patients who received vidutolimod monotherapy, the best ORR by RECIST v1.1 was 20.0% (95% CI, 9.1-35.6).
The median duration of response was 5.6 months (95% CI, 3.1-NE).
The most common treatment-related adverse events were chills, pyrexia, nausea, fatigue, headache, hypotension, and pruritus.