HPN328, a TriTAC^®, Exhibits the Potency, Tolerability, and Pharmacokinetics to Support Initiation of Clinical Development in 2020

SOUTH SAN FRANCISCO, Calif., Oct. 29, 2019 (GLOBE NEWSWIRE) -- Harpoon Therapeutics, Inc. (NASDAQ: HARP), a clinical-stage immunotherapy company developing a novel class of T cell engagers, today presented a poster showing preclinical data supporting HPN328 as a treatment for small cell lung cancer (SCLC) at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics meeting in Boston. The poster titled “HPN328: An anti-DLL3 T cell engager for treatment of small cell lung cancer” presents a wide range of preclinical data that shows HPN328, a Tri-specific T cell Activating Construct (TriTAC^®) binds to human and non-human primate DLL3, CD3ε, and albumin with similar affinities. When administered to mice bearing human SCLC xenografts and human T cells, HPN328 eradicated tumors supporting its evaluation in human cancer patients.

“These encouraging data demonstrate that HPN328 can simultaneously engage DLL3, on a small cell lung cancer cell, and CD3, on a T cell, resulting in T cell activation and eventual lysis of the tumor,” said Holger Wesche, Ph.D., Chief Scientific Officer of Harpoon Therapeutics. “It is important to note that while many patients with SCLC respond to the standard of care, relapse is common, with a 5 year overall survival rate of less than 5%. HPN328 mobilizes the patient’s own immune system to destroy the cancer and may become an important therapeutic option.”

Data presented in the poster showed that HPN328 directs T cells to kill DLL3 expressing cells in vitro and induces the elimination of tumors in models of small cell lung cancer. In cynomolgus monkeys, HPN328 has a terminal serum half-life of 68-79 hours and TriTACs, including HPN328, exhibit extended in vivo stability. Samples that were collected after more than one week in circulation maintained their full T cell engaging activity as demonstrated in ex-vivo assays support the potential for at least once weekly dosing. HPN328 was well tolerated in cynomolgus monkeys at 1 and 10 mg/kg. Initiation of a first in human Phase 1 clinical trial is planned for 2020.  

About HPN328

HPN328 is Harpoon’s fourth Tri-specific T cell Activating Construct (TriTAC^®) candidate in development. HPN328 targets DLL3, a protein highly expressed in a majority of SCLC tumors with limited expression in normal tissues. This selective expression makes DLL3 an attractive drug target for T cell engagers. Harpoon is currently conducting IND-enabling studies and expects to initiate a Phase 1 clinical trial of HPN328 in 2020.

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 T cell engagers, or TriTACs, initially focused on the treatment of solid tumors and hematologic malignancies. Harpoon’s first product, HPN424 targets PSMA and is in a Phase 1 trial for metastatic castration-resistant prostate cancer. Harpoon’s second product, HPN536 targets mesothelin and is in a Phase 1/2a trial for cancers expressing mesothelin, initially focused on ovarian and pancreatic cancers. For additional information about Harpoon Therapeutics, please visit www.harpoontx.com.

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 timing of IND submissions, 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, and the timing of development milestones for product candidates. 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, 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.

Contacts:

Harpoon Therapeutics, Inc.
Georgia Erbez
Chief Financial Officer
650-443-7400
media@harpoontx.com

Westwicke ICR
Robert H. Uhl
Managing Director
858-356-5932
robert.uhl@westwicke.com

Source: Harpoon Therapeutics