By Tristan Manalac

Pictured: AbbVie corporate office in California/iStock, vzphotos
AbbVie will not exercise its exclusive licensing option for Harpoon Therapeutics’ HPN217 program, being developed for the treatment of multiple myeloma, the immuno-oncology biotech announced Wednesday.
Harpoon will retain exclusive ownership over HPN217, for which it is running a Phase I clinical trial. The company will complete the study and plans to advance the candidate through its next phases of development.
Despite AbbVie’s decision, Harpoon CEO Julie Eastland said in a statement that the biotech remains “confident in HPN217’s potential” to offer multiple myeloma patients “a differentiated treated option.”
The company will share interim results from the candidate’s Phase I study at the upcoming International Myeloma Society (IMS) Annual Meeting, scheduled for Sept. 28, Eastland said.
Developed using Harpoon’s proprietary TriTAC technology, HPN217 targets the B-cell maturation antigen, a protein highly and specifically expressed on myeloma cells. TriTAC, which stands for tri-specific T cell-activating construct, is an emerging class of therapy comprised of three binding domains and is specifically designed to have improved stability, extended half-life while not needing high levels of its target antigen.
Like other T cell engagers, TriTACs work by targeting cells that express tumor antigens, in turn allowing the body’s natural T cell response to detect, bind to and destroy cancer cells. Unlike typical engagers which use antibodies, TriTACs are much smaller leading to better tissue and tumor penetration.
TriTACs are also being developed as off-the-shelf treatment modalities, making them easier to manufacture than other personalized therapies.
AbbVie bought into this technology in November 2019, paying $50 million upfront for the option to exclusively license HPN217 and for worldwide rights to develop TriTAC candidates using Harpoon’s platform. The deal also included up to $50 million more, dependent on milestones for HPN217.
Under the deal, each additional target nominated under the agreement meant a potential $310 payout for Harpoon, resulting in a total maximum deal value of $510 million plus royalties.
According to Harpoon’s news release on Wednesday, this agreement with AbbVie is set to formally end on Oct. 12, 2023.
Despite losing a powerhouse partner, Harpoon will continue to develop its other TriTAC candidate HPN328, a DDL3-targeting molecule being developed under a Tecentriq (atezolizumab) supply agreement with Roche for the treatment of small cell lung cancer. HPN328 is currently in Phase I.