Harpoon Therapeutics Announces Data from Poster Presentations at the AACR Annual Meeting 2021

South San Francisco, California, UNITED STATES

SOUTH SAN FRANCISCO, Calif., April 10, 2021 (GLOBE NEWSWIRE) -- Harpoon Therapeutics, Inc. (NASDAQ: HARP), a clinical-stage immunotherapy company developing a novel class of T cell engagers, today announced the availability of three poster presentations at the American Association for Cancer Research (AACR) Annual Meeting. The presentations will be available beginning today at 8:30 a.m. ET through the virtual meeting website at www.aacr.org and on the Harpoon corporate website at www.harpoontx.com.

Key findings of each of the posters are described below.

FLT3-targeting TriTACs® are T cell engagers for treatment of acute myeloid leukemia    
Presenter: Richard J. Austin, Ph.D., Abstract #: 2643

FLT3 RNA is found in over 95% of AML samples and FLT3 mutations are oncogenic and found in approximately 30% of AML. This provides the rationale that a FLT3-targeting T cell engager could be a valid therapeutic approach for AML. Data show that FLT3 TriTACs® bind human and non-human primate FLT3, and can redirect T cells to kill FLT3 expressing cells in vitro. In addition, FLT3 TriTACs® eliminate FLT3 expressing cells in a non-human primate study and are well tolerated after a single dose.

ProTriTAC™ is a modular and robust T cell engager prodrug platform with therapeutic index expansion observed across multiple tumor targets
Presenter: S. Jack Lin, Ph.D., Abstract #: 933

ProTriTAC™ is a conditionally active T cell engager platform that is designed to be preferentially active in the tumor. This enables the targeting of more broadly expressed solid tumor targets and allows T cell engagers to address more tumor types. Data presented today illustrate the consistency and the robustness of the ProTriTAC™ platform in vitro and in vivo as demonstrated by cell-based assays, pharmacokinetic studies in non-human primates, and therapeutic index assessments in tumor-bearing animals across multiple tumor targets. IND-enabling studies are currently underway for Harpoon’s first ProTriTAC™ program (HPN601).   

Combinatorial antitumor effects of CD3-based trispecific T cell activating constructs (TriTACs®) and checkpoint inhibitors in preclinical models
Presenter: Mary Ellen Molloy, Ph.D. Abstract #: 1573

TriTAC® molecules induce PD1/PD-L1 expression on T cells which may lead to suppression of the cytolytic functions of TriTAC® activated T cells. PD1 can be readily detected on T cells subsequent to the engagement of the TCR by the TriTAC® molecule. Data presented today show that the combination of HPN536 with a PD-L1 inhibitor led to more potent antitumor activity in an MSLN expressing ovarian cancer xenograft model. Similar enhanced anti-tumor effects were shown in an MSLN expressing lung cancer model for HPN536 in combination with anti-PD1 or an anti-PD1 antibody. These data demonstrate the potential utility of PD1/PD-L1 blockade to enhance the potency of TriTAC® mediated tumor cell killing.

“These data from Harpoon’s poster presentations at AACR underscore the potential for further investigations of additional tumor targets, combination approaches with TriTACs®, and conditionally active T cell engager prodrugs, or ProTriTACs™, which may lead to greater tumor specificity, enhanced efficacy, and improved tolerability for patients,” said Holger Wesche, Ph.D., chief scientific officer of Harpoon Therapeutics. “I am encouraged by these findings and look forward to future validation in the clinic.”

About Harpoon Therapeutics

Harpoon Therapeutics is a clinical-stage immunotherapy company developing a novel class of T cell engagers that harness the power of the body’s immune system to treat patients suffering from cancer and other diseases. T cell engagers are engineered proteins that direct a patient’s own T cells to kill target cells that express specific proteins, or antigens, carried by the target cells. Using its proprietary Tri-specific T cell Activating Construct (TriTAC®) platform, Harpoon is developing a pipeline of novel TriTACs® initially focused on the treatment of solid tumors and hematologic malignancies. HPN424 targets PSMA and is in a Phase 1/2a trial for metastatic castration-resistant prostate cancer. HPN536 targets mesothelin and is in a Phase 1/2a trial for cancers expressing mesothelin, initially focused on ovarian and pancreatic cancers. HPN217 targets BCMA and is in a Phase 1/2 trial for relapsed, refractory multiple myeloma. HPN328 targets DLL3 and is in a Phase 1/2 trial for small cell lung cancer and other DLL3-associated tumors. Harpoon has also developed a proprietary ProTriTAC™ platform, which applies a prodrug concept to its TriTAC® platform to create a therapeutic T cell engager that remains inactive until it reaches the tumor. For additional information about Harpoon Therapeutics, please visit www.harpoontx.com.

Cautionary Note on Forward-looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Words such as “may,” “will,” “expect,” “plan,” “anticipate,” “target,” “estimate,” “intend” and similar expressions (as well as other words or expressions referencing future events, conditions or circumstances) are intended to identify forward-looking statements. These forward-looking statements are based on Harpoon Therapeutics’ expectations and assumptions as of the date of this press release. Each of these forward-looking statements involves risks and uncertainties that could cause Harpoon Therapeutics’ clinical development programs, future results or performance to differ significantly from those expressed or implied by the forward-looking statements. Forward-looking statements contained in this press release include, but are not limited to, statements about the progress, timing, scope and anticipated results of clinical trials, the timing of the presentation of data, the association of data with potential treatment outcomes, the development and advancement of product candidates, the timing of development milestones for product candidates, and the anticipated potential impacts to Harpoon Therapeutics’ business from the ongoing COVID-19 pandemic. Many factors may cause differences between current expectations and actual results, including unexpected safety or efficacy data observed during clinical studies, clinical trial site activation or enrollment rates that are lower than expected, unanticipated or greater than anticipated impacts or delays due to COVID-19, changes in expected or existing competition, changes in the regulatory environment, the uncertainties and timing of the regulatory approval process, and unexpected litigation or other disputes. Other factors that may cause Harpoon Therapeutics’ actual results to differ from those expressed or implied in the forward-looking statements in this press release are discussed in Harpoon Therapeutics’ filings with the U.S. Securities and Exchange Commission, including the “Risk Factors” sections contained therein. Except as required by law, Harpoon Therapeutics assumes no obligation to update any forward-looking statements contained herein to reflect any change in expectations, even as new information becomes available.


Harpoon Therapeutics, Inc.
Georgia Erbez
Chief Financial Officer

Westwicke ICR
Robert H. Uhl
Managing Director