Harpoon Therapeutics stock exits Nasdaq after Merck takeover

Harpoon Therapeutics stock exited Nasdaq after Merck completed its acquisition of the clinical-stage immunotherapy company. The transaction was valued at USD 680 million and converted Harpoon from a standalone public company into a wholly owned Merck subsidiary.

As of September 24, 2026, HARP is therefore a historical Nasdaq ticker rather than an active listed security. The status matters because the transaction ended the public-market route for Harpoon shareholders and shifted the value of its drug programs to Merck.

Merck takes control of HPN328

The acquisition broadened Merck's oncology pipeline with Harpoon's T-cell engager technology, centered on HPN328, also known as MK-6070. The program targets delta-like ligand 3, or DLL3, and is designed to direct immune cells toward cancer cells.

According to Life Sciences PA, Harpoon's portfolio included HPN328 and the acquisition was completed with Harpoon becoming a wholly owned subsidiary of Merck. The same report states that Harpoon common stock would cease to be publicly traded or listed on Nasdaq.

USD 680 million sets the scale

The USD 680 million consideration provides the clearest quantified measure of Harpoon's strategic value at the time of the takeover. It also marks a sharp change in the company's investor profile: the relevant asset is now an internal Merck pipeline program, while HARP itself has left the exchange.

For investors reviewing old HARP records, the distinction between the historical ticker and the continuing drug program is essential. HPN328 remains tied to Harpoon's scientific platform, but the listed-company framework ended with the acquisition.

HARP leaves the public market

Harpoon Therapeutics was a biotechnology company focused on antibody-based cancer treatments. Its historical Nasdaq listing was HARP, while the post-acquisition ownership structure places the company's assets under Merck rather than in a separately traded security.