Merck, known as MSD outside of the United States and Canada, and Harpoon Therapeutics today announced that the companies have entered into a definitive agreement under which Merck, through a subsidiary, will acquire Harpoon for $23 per share in cash for an approximate total equity value of $680 million.
Harpoon has developed a portfolio of novel T-cell engagers that employ the company’s proprietary Tri-specific T cell Activating Construct (TriTAC) platform, an engineered protein technology designed to direct a patient’s own immune cells to kill tumor cells, and ProTriTAC platform, applying a prodrug concept to its TriTAC platform to create a therapeutic T-cell engager that is designed to remain inactive until it reaches the tumor.
Harpoon’s lead candidate, HPN328, is a T-cell engager targeting delta-like ligand 3 (DLL3), an inhibitory canonical Notch ligand that is expressed at high levels in small cell lung cancer (SCLC) and neuroendocrine tumors. HPN328 is currently being evaluated in a Phase 1/2 clinical trial evaluating the safety, tolerability and pharmacokinetics of HPN328 monotherapy in patients with advanced cancers associated with expression of DLL3. The study is also evaluating HPN328 in combination with atezolizumab in patients with SCLC. In October 2023, Harpoon announced the presentation of positive interim tolerability and response data for HPN328 in certain patients with SCLC and neuroendocrine tumors.
Additional pipeline candidates include HPN217 targeting B-cell maturation antigen (BCMA), currently in Phase 1 clinical development for the treatment of patients with relapsed/refractory multiple myeloma, and several preclinical stage candidates, including HPN601, a conditionally activated targeting epithelial cell adhesion molecule (EpCAM) for the treatment of certain patients with EpCAM expressing tumors.
The Board of Directors of Harpoon has unanimously approved the transaction. Closing of the acquisition is subject to certain conditions, including approval of the merger by Harpoon’s stockholders, the expiration of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act, and other customary conditions. The transaction is expected to close in the first half of 2024 and will be accounted for as an asset acquisition. Merck expects to record a charge (non-tax deductible) of approximately $650 million, or approximately $0.26 per share, that will be included in non-GAAP results in the quarter that the transaction closes.