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Expanding its oncology pipeline, Merck completed its acquisition of Harpoon Therapeutics Inc.

As of March 11, Harpoon is a wholly owned subsidiary of Rahway-based Merck and its stock will no longer trade publicly or appear on the Nasdaq Stock Market. The transaction is being accounted for as an asset acquisition, with Merck recording a non-tax deductible charge to R&D expense of approximately $650 million. The deal was announced in January 2024.

“We continue to augment and diversify our oncology pipeline with innovative approaches to help people with cancer worldwide,” said Dr. Dean Y. Li, president, Merck Research Laboratories. “We are pleased to welcome our Harpoon colleagues to Merck and look forward to working together to advance a novel portfolio of T-cell engagers, including MK-6070.”

The acquisition is part of Merck’s focus on cancer and exploration of immuno-oncology. In fact, Merck said it has one of the industry’s largest development programs, spanning 30-plus tumor types. The biopharmaceutical giant added it continues to strengthen its portfolio through purchases, as with Harpoon.

Merck announced several deals in 2023, including the up to $610 million acquisition of biopharmaceutical company Caraway Therapeutics and its $10.8 billion purchase of Prometheus Bioscienes Inc.

T-cell tech

Harpoon’s lead candidate is MK-6070, formerly known as HPN328. When the deal was announced, Harpoon President and CEO Julie Eastland said it “well positioned” the treatment moving forward.

The target’s work involves developing a portfolio of novel T-cell engagers designed to harness the power of the body’s immune system to treat patients with cancer and other diseases. Initially, the program focuses on treating certain types of solid tumors and hematologic malignancies.

The T-cell engager is intended for use with small cell lung cancer and neuroendocrine tumors.

Using its proprietary Tri-specific T cell Activating Construct (TriTAC) platform, the engineered proteins tell a patient’s own T-cells to attack target cells that express specific proteins, or antigens, carried by the target cells. To that end, Harpoon’s ProTriTAC platform keeps the T-cell engager inactive until it reaches the tumor.

The U.S. Food and Drug Administration granted Orphan Drug Designation to HPM328 for the treatment of SCLC in March 2022. According to Merck, the treatment is also being evaluated for additional applications.

Additional pipeline candidates include HPN217 and HPN601.