Merck to Acquire Harpoon Therapeutics in Deal Valued at $680 Million

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Through the acquisition of Harpoon Therapeutics, Merck will gain an investigational delta-like ligand 3-targeting T-cell engager under development for cancer treatment.

Merck, known as MSD outside of the United States and Canada, and Harpoon Therapeutics, a US-based clinical-stage immuno-oncology company, announced on Jan. 8, 2024 that they have entered into a definitive agreement for Merck to acquire Harpoon via a Merck subsidiary. Merck will acquire Harpoon for $23.00 per share in cash, or a total equity value of approximately $680 million. The transaction is expected to close in the first half of 2024.

Under the agreement, Merck will gain Harpoon’s lead candidate, HPN328, a T-cell engager targeting delta-like ligand 3 (DLL3). DLL3 is an inhibitory canonical Notch ligand that has been shown to be expressed at high levels in small cell lung cancer (SCLC) and neuroendocrine tumors. HPN328 is currently being studied in a Phase I/II clinical trial as a monotherapy in patients with advanced cancers associated with the expression of DLL3. It is also being studied in combination with atezolizumab in patients with SCLC. Harpoon announced positive interim tolerability and response data in certain patients with SCLC and neuroendocrine tumors last October 2023.

Harpoon has developed a portfolio of novel T-cell engagers using the company’s proprietary Tri-specific T cell Activating Construct (TriTAC) platform. The TriTAC platform is an engineered protein technology that has been designed to direct a patient’s own immune cells to kill tumor cells. In addition, the company’s ProTriTAC platform involves the application of a prodrug concept to the TriTAC platform to create a therapeutic T-cell engager that is designed to remain inactive until it reaches the tumor.

Additional candidates in the company’s pipeline include HPN217, which targets B-cell maturation antigen (BCMA). HPN217 is currently in Phase I clinical development for treating patients with relapsed/refractory multiple myeloma. The company also has several preclinical-stage candidates, including HPN601, which is a conditionally activated targeting epithelial cell adhesion molecule (EpCAM) for treating certain patients with EpCAM-expressing tumors.


“At Merck, we continue to enhance our oncology pipeline through strategic acquisitions that complement our current portfolio and advance breakthrough science to help address the needs of people with cancer worldwide,” said Dean Y. Li, president, Merck Research Laboratories, in a company press release. “This agreement reflects the creativity and commitment of scientists and clinical development teams at Harpoon. We look forward to further evaluating HPN328 in innovative combinations with other pipeline candidates.”

“At Harpoon, we have always been committed to advancing our cancer immunotherapy candidates to improve the lives of patients. With Merck’s recognized leadership in oncology clinical development and global commercial footprint, our lead candidate, HPN328, is well positioned moving forward,” said Julie Eastland, president and chief executive officer, Harpoon Therapeutics, in the press release.

Source: Merck