• Collaboration complements Merck’s internal expertise and in-house ADC approach
• Companies focused on discovering novel STING-agonist ADCs for up to two targets leveraging Mersana’s proprietary Immunosynthen platform to conjugate proprietary antibodies from Merck
• Merck gains exclusive license; Mersana to receive $30 million upfront payment, up to $800 million in development, regulatory and commercial milestones, as well as royalties on net sales

Merck, a leading science and technology company, today announced a research collaboration and commercial license agreement with Mersana Therapeutics, Inc., Cambridge, Massachusetts, USA to discover novel antibody-drug conjugates (ADCs) leveraging Mersana’s proprietary Immunosynthen STING-agonist ADC platform, directed against up to two targets. The Immunosynthen platform is designed to generate systemically administered ADCs that locally activate STING signaling in both tumor-resident immune cells and in antigen-expressing tumor cells, unlocking the anti-tumor potential of innate immune stimulation.

“Building on our deep expertise and portfolio of two clinical and nine preclinical assets in the ADC space, we are focused on the discovery of next-generation state-of-the-art ADC drugs,” said Paul Lyne, Head of Research Unit, Oncology, Merck KGaA, Darmstadt, Germany. “An approach that can directly target the tumor microenvironment with an immunomodulatory ADC has the potential to bring the benefits of this immunotherapy to a broader group of patients. This collaboration with Mersana to design novel immunostimulatory ADCs that can harness the potential of the STING pathway is an ideal complement to our innovation in this area.”

The STING pathway is a fundamental means of generating innate immune response that can lead to anti-tumor activity and immunological memory. Mersana’s extensive preclinical data demonstrate Immunosynthen’s ability to enable highly targeted STING activation within both tumor cells and tumor resident myeloid cells while avoiding unwanted systemic effects.

“We are pleased to be partnering with Merck KGaA, Darmstadt, Germany to extend the reach of our Immunosynthen platform and bring novel new product candidates forward with the potential to benefit patients,” said Anna Protopapas, President and Chief Executive Officer of Mersana Therapeutics.

Under the terms of the agreement, Mersana will develop novel ADC product candidates against up to two targets utilizing its Immunosynthen platform to conjugate proprietary antibodies from Merck KGaA, Darmstadt, Germany. Pre-clinical activities will be split between the companies. Merck KGaA, Darmstadt, Germany will be solely responsible for all clinical development and potential commercialization activities relating to any resulting product candidates.

Mersana will receive an upfront payment of $30 million. Mersana is also eligible to receive reimbursement of certain costs, up to $800 million in potential regulatory, development and commercial milestone payments, and up to low double-digit percentage royalties on worldwide net sales of any approved ADCs developed under the agreement.