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Merck to Acquire Harpoon Therapeutics for $680M

NEW YORK – Merck announced on Monday that it will acquire Harpoon Therapeutics in a deal that will add the DLL3-targeting agent HPN328 to its oncology pipeline.

Under the terms of the acquisition, Merck will acquire Harpoon through a subsidiary for $23 per share in a deal with a total equity value of $680 million. The firms expect the deal to close during the first half of 2024.

South San Francisco, California-based Harpoon has been evaluating HPN328, a T-cell engager that targets DLL3, as a treatment for small cell lung cancer, neuroendocrine cancers, and other advanced cancers associated with DLL3 expression. To be eligible for the ongoing Phase I/II clinical trial, patients with high-grade neuroendocrine tumor types other than SCLC and neuroendocrine prostate cancer must have confirmed DLL3 expression in a tumor sample.

The firm designed HPN328, its lead candidate T-cell engager, using its tri-specific T-cell activating construct, or TriTAC, platform. The US Food and Drug Administration granted the drug orphan status in 2022. 

Beyond HPN328, Harpoon is also developing the multiple myeloma drug HPN217, which is designed to target the B-cell maturation antigen, and HPN601, an agent designed for patients with EpCAM-expressing cancers.

"This agreement reflects the creativity and commitment of scientists and clinical development teams at Harpoon," Merck Research Laboratories President Dean Li said in a statement. "We look forward to further evaluating HPN328 in innovative combinations with other pipeline candidates."

Evercore Group is Merck's financial adviser on the deal, and Covington & Burling is its legal adviser. Centerview Partners and Goodwin Procter are Harpoon's financial and legal advisers, respectively.