Harpoon’s IPO Spears $76M as Prostate Cancer Drug Continues Testing

Xconomy San Francisco — 

Cancer immunotherapy developer Harpoon Therapeutics is the latest biotech to enter the public markets, raising approximately $76 million in an initial public offering.

South San Francisco, CA-based Harpoon offered 5.4 million shares Thursday evening priced at $14 each, which was the midpoint of the range that the company had targeted. Harpoon shares are expected to begin trading on the Nasdaq Friday under the stock symbol “HARP.”

Harpoon develops immunotherapies that direct the T cells of a patient to target and kill cancer cells. In its prospectus, Harpoon calls its drugs “T cell engagers”— engineered proteins that target cells that have certain antigens, which are also proteins, on their surface. The company’s proprietary drug platform has yielded four drug candidates so far.

Lead Harpoon drug HPN424 is in a Phase 1 study enrolling patients who have advanced prostate cancer. Last month, the company released preliminary data from seven patients. Though the company reported no safety problems that would limit dosing of the drug, it said one patient had developed cytokine release syndrome, a potentially fatal immune response to treatment. That problem resolved within eight hours of dosing, Harpoon said. The company added that the patient experienced no additional reactions and continues to be part of the study, which is expected to enroll 40 patients.

A second Harpoon drug, HPN536, is being prepared to start clinical testing in the first half of this year for ovarian cancers and other solid tumors that express the protein mesothelin.

In 2018, Harpoon spent $17.6 million on research and development through the third quarter. Besides financing clinical testing of its two most advanced drug candidates, Harpoon says the IPO cash will support development of its pipeline. According to the prospectus, Harpoon has preclinical compounds for multiple myeloma and small-cell lung cancer.

Harpoon, which was founded in 2015, has raised more than $130 million in financing. The company’s most recent funding event was last November, when it closed a $70 million Series C round. Investors in that financing included OribMed, Cormorant, and Ridgeback Capital Investments.

Photo by Flickr user Wonderlane via a Creative Commons license