Regeneron to Acquire Checkmate Pharmaceuticals and its Investigational Immune Activator for Potential use in Multiple Tumor Types

• Proposed ~$250 million all-cash acquisition strengthens Regeneron's portfolio of diverse and combinable immuno-oncology candidates
• Lead investigational asset vidutolimod is a potential best-in-class TLR9 agonist, with demonstrated clinical responses observed in PD-1 refractory melanoma as monotherapy
• Vidutolimod is currently being studied in combination with other agents for melanoma, non-melanoma skin cancers, and head and neck cancer

TARRYTOWN, N.Y. and CAMBRIDGE, Mass., April 19, 2022 /PRNewswire/ -- Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN) and Checkmate Pharmaceuticals, Inc. (NASDAQ: CMPI), a clinical stage biopharmaceutical company focused on proprietary technology to harness the power of the immune system to combat cancer, today announced a definitive agreement for the acquisition of Checkmate by Regeneron at an all-cash price of $10.50 per share of Checkmate common stock. The proposed acquisition values Checkmate at a total equity value of approximately $250 million.

Checkmate's lead investigational candidate is vidutolimod, an advanced generation CpG-A oligodeoxynucleotide Toll-like receptor 9 (TLR9) agonist delivered in a virus-like particle.

"As we continue to advance and expand our research efforts in immuno-oncology, the acquisition of Checkmate will add a promising new modality to Regeneron's toolkit of potential approaches for difficult-to-treat cancers," said Leonard S. Schleifer, M.D., Ph.D., President and Chief Executive Officer of Regeneron. "The unique combination of a differentiated Toll-like receptor 9 with other antibody-based oncology agents may result in increased clinical benefit and provide new treatment options for patients in need. We look forward to welcoming the Checkmate team and their complementary scientific acumen to the Regeneron family."

"We are thrilled that Checkmate will become part of Regeneron, a biotechnology leader that shares our deep appreciation for science, hunger for ground-breaking discoveries and commitment to helping patients defeat cancer," said Alan Bash, President and Chief Executive Officer of Checkmate.

"We believe that the data we have generated with vidutolimod positions Checkmate at the forefront of the innate immune activator field. It is our hope that Regeneron's resources and expertise will help accelerate the development of vidutolimod and realization of the full potential of our virus-like particle (VLP) platform for immunotherapy," said Art Krieg, M.D., Checkmate's Founder and Chief Scientific Officer.

Vidutolimod is administered into the tumor and is believed to induce and expand anti-tumor T cells and induce tumor regression as a monotherapy in patients whose tumors previously progressed on PD-1 checkpoint inhibition. In the Phase 1b program, documented abscopal responses were seen in distant, un-injected lesions. Vidutolimod is an investigational therapy and has not been approved by U.S. Food and Drug Administration or any other regulatory agency. 

The merger agreement provides for Regeneron, through a subsidiary, to initiate a tender offer to acquire all outstanding shares of Checkmate at an all-cash price of $10.50 per share of Checkmate common stock. The closing of the tender offer will be subject to certain conditions, including the tender of at least a majority of the outstanding shares of Checkmate common stock, the expiration of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act and other customary closing conditions. Upon the successful completion of the tender offer, Regeneron will acquire all shares not acquired in the tender through a second-step merger. The transaction is expected to close in mid-2022.

Regeneron's legal advisor for the transaction is Wachtell, Lipton, Rosen & Katz. Centerview Partners is serving as Checkmate's financial advisor and Goodwin Procter LLP is serving as its legal advisor.

About Vidutolimod
Vidutolimod works by two complementary mechanisms that together have a unique ability to drive a strong systemic anti-tumor T cell response. First, the virus-like particle (VLP) activates an immune response to the VLP, leading to the production of antibodies that deliver the VLP into plasmacytoid dendritic cells (pDC) and other immune cells via specialized receptors called FcRs. This provides an initial stimulatory signal to pDC and brings the CpG-A to TLR9 (the receptor for CpG DNA) inside the pDC. Second, CpG-A stimulates TLR9 in a manner that induces pDC to release significantly higher levels of IFN-α and other type I interferons than other innate immune activators, resulting in a stronger anti-tumor T cell response.

Animal models and in vitro experiments suggest that, when activated by vidutolimod by this combination of signals, pDC recruit and coordinate a variety of other immune cells, culminating in the generation of a strong anti-tumor T cell response.

About Regeneron
Regeneron (NASDAQ: REGN) is a leading biotechnology company that invents life-transforming medicines for people with serious diseases. Founded and led for nearly 35 years by physician-scientists, our unique ability to repeatedly and consistently translate science into medicine has led to nine FDA-approved treatments and numerous product candidates in development, almost all of which were homegrown in our laboratories. Our medicines and pipeline are designed to help patients with eye diseases, allergic and inflammatory diseases, cancer, cardiovascular and metabolic diseases, pain, hematologic conditions, infectious diseases and rare diseases.

Regeneron is accelerating and improving the traditional drug development process through our proprietary VelociSuite^® technologies, such as VelocImmune^®, which uses unique genetically humanized mice to produce optimized fully human antibodies and bispecific antibodies, and through ambitious research initiatives such as the Regeneron Genetics Center, which is conducting one of the largest genetics sequencing efforts in the world.

For additional information about the company, please visit www.regeneron.com or follow @Regeneron on Twitter.

About Checkmate Pharmaceuticals 
Checkmate Pharmaceuticals is a clinical stage biotechnology company focused on developing its proprietary technology to harness the power of the immune system to combat cancer. Checkmate Pharmaceuticals' product candidate, vidutolimod (CMP-001), is an advanced generation Toll-like receptor 9 (TLR9) agonist, delivered as a biologic virus-like particle utilizing a CpG-A oligodeoxynucleotide as a key component, designed to trigger the body's innate immune system to attack tumors in combination with other therapies. Information regarding Checkmate Pharmaceuticals is available at www.checkmatepharma.com.