Checkmate Pharmaceuticals Presents Updated Clinical Data with CMP-001 at The Society for Immunotherapy of Cancer (SITC) 35th Anniversary Annual Meeting

CMP-001 in combination with pembrolizumab continues to demonstrate durable responses in anti-PD-1 refractory melanoma in ongoing trial

Encouraging new data on pathological responses and 1-year RFS with neoadjuvant CMP-001 and nivolumab in resectable Stage IIIB/C/D melanoma

CAMBRIDGE, Mass., Nov. 09, 2020 (GLOBE NEWSWIRE) — Checkmate Pharmaceuticals, Inc. (NASDAQ: CMPI) (“Checkmate”), a clinical stage biopharmaceutical company focused on developing its proprietary technology to harness the power of the immune system to combat cancer, today announced the presentation of new data from two ongoing clinical trials evaluating CMP-001, Checkmate’s Toll-like receptor 9 (TLR9) agonist, in combination with the anti-PD-1 antibodies pembrolizumab (KEYTRUDA®) or nivolumab (OPDIVO®), in patients with melanoma.

“CMP-001 continues to demonstrate clinical benefit, in combination with anti-PD-1 antibodies, with an ORR of 23.5% and median duration of response of 19.9 months in patients with anti-PD-1 refractory melanoma,” said Barry Labinger, President and Chief Executive Officer of Checkmate. “We are also encouraged by the maturing data in the anti-PD-1 naïve neoadjuvant study, which has demonstrated a 70% pathological response rate and 1-year relapse free survival of 90% in patients with a pathologic response.”

Intratumoral injection of CMP-001, a Toll-like receptor 9 (TLR9) agonist, in combination with pembrolizumab reversed programmed death receptor 1 (PD-1) blockade resistance in advanced melanoma (Abstract #: 579; NCT02680184)

In the SITC 2020 Virtual Press Conference, November 9, between 7:45am-9:00am ET, and in the Virtual Poster Hall, November 11-14, 2020 between 9:00am-5:00pm ET, Dr. Mohammed Milhem, Chief, Section of Oncology, and Clinical Professor of Internal Medicine, University of Iowa Healthcare, presents updated data from an ongoing Checkmate-sponsored clinical trial of CMP-001 in combination with pembrolizumab or as a monotherapy.

Key highlights from these clinical data as of the data cut-off of September 30, 2020 include:

CMP-001 in combination with pembrolizumab

• In patients treated with CMP-001 PS20 0.01% in combination with pembrolizumab, the best ORR by RECIST v1.1 was 23.5% (23/98), including 7 complete responses and 16 partial responses, and 27.6% (27/98) including patients with responses after initial progressive disease.
• The Kaplan Meier estimate for median duration of response across all patients was 19.9 months for both RECIST v1.1 responders and RECIST v1.1 responders plus post-progressive disease responders.
• The mean regression in injected and non-injected target lesions was similar in responding patients.
• Most treatment related adverse events (TRAEs) were Grade 1 or 2 and included flu-like symptoms, including chills, fever, fatigue, nausea, vomiting, and headache, and injection site pain. The most common treatment-related Grade 3 or 4 adverse events were hypotension (6.3%) and hypertension (5.0%). No Grade 5 treatment-related adverse events were reported.

CMP-001 monotherapy

• Of the 40 patients treated with CMP-001 monotherapy, 7 patients (17.5%) achieved a partial response by RECIST v1.1, and the median duration of response was 5.6 months.
• Most treatment-related adverse events were Grade 1 or 2 and included flu-like symptoms including chills, fever, nausea, fatigue, and headache. The only treatment-related Grade 3 adverse event in more than 1 patient was hypotension (n=2, 5.0%). No Grade 4 or 5 treatment-related adverse events were reported.

“The response rate, duration of response, and adverse event profile are encouraging given that 93% of the patients had progressive disease as the last response to anti-PD-1 antibodies at study entry,” said Dr. Milhem. “We need new treatment approaches for patients who progress after anti-PD-1 antibodies, and I’m excited to move this regimen forward into a potentially registrational study in patients with confirmed disease progression on PD-1 blockade.”

Phase II Trial of Neoadjuvant Nivolumab (Nivo) and Intra-Tumoral (IT) CMP-001 in High-Risk Resectable Melanoma (Neo-C-Nivo) (Abstract #: 612; NCT03618641)

In a Virtual Oral Presentation on Wednesday, November 11, 2020 at 5:30pm ET, Dr. Diwakar Davar, Assistant Professor of Medicine at the University of Pittsburgh School of Medicine, presents data from an investigator-sponsored trial evaluating neoadjuvant treatment with CMP-001 in combination with nivolumab in patients with Stage IIIB/C/D Melanoma.

Key highlights from these clinical data included:

• 30 patients were evaluable for efficacy per protocol.
  • Pathological responses were observed in 70% of patients, and the primary outcome measure of major pathological response rate was 60%. The response breakdown was as follows:
    • Pathological Complete Response (pCR = 15/30; 50%)
    • Pathological Major Response (pMR = 3/30; 10%)
    • Pathological Partial Response (pPR = 3/30; 10%)
• The median RFS has not been reached.
  • 1-year RFS was 89% in patients with major pathological response (pCR and pMR) and 90% in patients with any pathological response (pCR, pMR, and pPR).
• 31 patients were evaluable for safety per protocol.
  • CMP-001 in combination with nivolumab was generally well-tolerated with an acute toxicity profile consisting predominantly of Grade 1/2 TRAEs. The only treatment-related Grade 3 adverse event in more than 1 patient was hypertension (n=3, 9.7%). No Grade 4/5 TRAEs were reported.
  • There were no dose limiting toxicities or delays in surgery related to neoadjuvant treatment.
• Response was associated with evidence of intratumoral and peripheral immune activation.

“The pathological response rate in this study is among the highest reported for treatment that includes a PD-1 blocking antibody in neoadjuvant treatment of Stage III melanoma, and compares favorably with the reported data for neoadjuvant PD-1/CTLA-4 Opacin-Neo,” said Dr. Davar. “We are encouraged by the relapse free survival, and I’m particularly excited by our data demonstrating the activation of pDCs and infiltration of T cells in many of the responding tumors, which provides further support for the mechanism of action of CMP-001.”

Intravenous CMP-001, a CpG-A Toll-like receptor 9 (TLR9) agonist delivered via a virus-like particle, causes tumor regression in syngeneic Hepa1-6 mouse models of hepatocellular carcinoma (Abstract #: 418)

In the Virtual Poster Hall, November 11-14, 2020 between 9:00am-5:00pm ET, Dr. Arthur M. Krieg, Founder and Chief Scientific Officer of Checkmate Pharmaceuticals, presents data from a preclinical study of CMP-001 plus PD-1 blocking antibody in mouse models of hepatocellular carcinoma.

In orthotopic mouse models of HCC, the antitumor activity of intravenous CMP-001 was greater than PD-1 blockade and comparable to sorafenib. CMP-001 intravenous was more active than CMP-001 subcutaneous in this model, consistent with increased liver exposure with intravenous infusion. CMP-001 intravenous may be a promising treatment option to explore in future clinical research for patients with primary or metastatic liver cancers.

About CMP-001
CMP-001 comprises a virus-like particle utilizing a CpG-A oligonucleotide. It is designed to trigger the body’s innate immune system via TLR9 and infiltrate the tumor microenvironment by the subsequent induction of both innate and adaptive anti-tumor immune responses. Checkmate believes CMP-001 is the only compound utilizing a CpG-A class TLR9 agonist in clinical development. For information on CMP-001 trials that are currently recruiting patients, please visit www.clinicaltrials.gov.

About Checkmate Pharmaceuticals
Checkmate Pharmaceuticals is a clinical stage biotechnology company focused on developing proprietary technology to harness the power of the immune system to combat cancer. Checkmate’s product candidate, CMP-001, is a differentiated TLR9 agonist delivered as a biologic virus-like particle designed to trigger the body’s innate immune system to attack tumors in combination with other therapies. Checkmate’s goal is to leverage its proprietary technology to discover, develop and commercialize transformative treatments to fight cancer. Information regarding Checkmate is available at www.checkmatepharma.com.

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Forward Looking Statements
Various statements in this release are “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including. Words such as, but not limited to, “anticipate,” “believe,” “can,” “could,” “expect,” “estimate,” “design,” “goal,” “intend,” “may,” “might,” “objective,” “plan,” “predict,” “project,” “target,” “likely,” “should,” “will,” and “would,” or the negative of these terms and similar expressions or words, identify forward-looking statements. Forward-looking statements are based upon current expectations that involve risks, changes in circumstances, assumptions and uncertainties. These statements include those regarding our product candidate, including its development and therapeutic potential and the advancement of our clinical and preclinical pipeline; expectations regarding the results and analysis of data.  Forward-looking statements should not be read as a guarantee of future performance or results and may not be accurate indications of when such performance or results will be achieved. These forward-looking statements are subject to risks and uncertainties, including those related to the development of our product candidate, including any delays in our ongoing or planned preclinical or clinical trials; the risk that positive results from a clinical study may not necessarily be predictive of the results of future or ongoing clinical studies; the risk that data updates and interim results may not be predictive of future results; the impact of the ongoing COVID-19 pandemic on our business, operations, clinical trials, clinical supply and plans; the risks inherent in the drug development process; the risks regarding the accuracy of our estimates of expenses and timing of development, our capital requirements and the need for additional financing; and obtaining, maintaining and protecting our intellectual property. These and additional risks are discussed in the sections titled “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in our quarterly report on Form 10-Q for the quarter ended June 30, 2020, as filed with the U.S. Securities and Exchange Commission (SEC), as well as subsequent filings and reports filed with the SEC, which are available on the SEC’s website at www.sec.gov.

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CONTACT: Investor Contact
Kleem Chaudhary 
Chief Business Officer 
kleem@checkmatepharma.com

Media Contact
Karen Sharma 
MacDougall 
781-235-3060 
ksharma@macbiocom.com