Harpoon Therapeutics Presents Interim Phase 1 Data from an Ongoing Dose Escalation Trial for the PSMA-targeting TriTAC HPN424 at the ASCO20 Virtual Scientific Program

• The on-going dose escalation Phase 1 study has enrolled 44 patients with progressive, metastatic castration-resistant prostate cancer in 11 cohorts.
   
• Initial safety data showed that HPN424 is generally well-tolerated, and cytokine-related adverse events have been transient and manageable.
   
• Pharmacokinetic data supports weekly dosing and pharmacodynamic data supports T cell activation and target engagement consistent with the expected mechanism of action.
   
• Signals of clinical activity include multiple patients remaining on study for more than 24 weeks, and serum PSA declines.
   
• Management to host webcast and conference call to review the interim Phase 1 data and provide a pipeline update today at 4 p.m. ET /1 p.m. PT  

SOUTH SAN FRANCISCO, Calif., May 29, 2020 (GLOBE NEWSWIRE) -- Harpoon Therapeutics, Inc. (NASDAQ: HARP), a clinical-stage immunotherapy company developing a novel class of T cell engagers, today presented interim data from the ongoing dose-escalation portion of a Phase 1 trial for HPN424 in patients with metastatic castration-resistant prostate cancer (mCRPC) at the American Society of Clinical Oncology (ASCO) 2020 Virtual Scientific Program. HPN424 targets prostate-specific membrane antigen (PSMA) and is based on Harpoon’s proprietary Tri-specific T cell Activating Construct (TriTAC) platform designed to recruit a patient’s own immune cells to kill tumor cells.

The presentation highlights interim results in 44 patients across 11 dosing cohorts treated with HPN424 from the ongoing dose escalation portion of a Phase 1 clinical trial. As of the May 11, 2020 cut-off date, initial data demonstrate:

• HPN424 is generally well-tolerated and support long-term treatment, and cytokine-related adverse events have been transient and manageable.
• Pharmacokinetic data support weekly dosing and pharmacodynamic data support T cell activation as measured by reduction in circulating tumor cells, increased serum cytokine levels and T cell margination after HPN424 administration.
• Early signals of clinical activity include eight patients who remained on study treatment for greater than 24 weeks. In addition, eight patients exhibited decreases in PSA levels compared to baseline, including two who showed PSA (prostate-specific antigen) reductions of at least 50%.

“We are particularly encouraged by data supporting the predicted mechanism of action of HPN424, and the early signs of clinical activity in this heavily pretreated population,” stated Gerald McMahon, Ph.D., President and CEO, Harpoon Therapeutics. “These initial data from our lead program represent the first of four product candidates in our TriTAC clinical portfolio that can provide multiple opportunities to accelerate our pipeline into more advanced clinical studies.”