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Harpoon Therapeutics Presents Preclinical Data Supporting Development of HPN217, a New BCMA-Targeting TriTAC, at the 2018 American Society of Hematology (ASH) Annual Meeting

Harpoon Therapeutics, Inc. ("Harpoon"), 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 with cancer and other diseases, today presented preclinical data supporting the development of HPN217, a new compound targeting B cell maturation antigen (BCMA). Generated from Harpoon’s Tri-specific T cell Activating Construct ("TriTAC") platform, HPN217 is engineered to re-direct a patient’s own T cells to kill BCMA-positive cancer cells. HPN217 is Harpoon’s first TriTAC designed for the treatment of hematologic cancers, such as multiple myeloma. Data were presented at the 2018 American Society of Hematology (ASH) Annual Meeting in San Diego, held December 1-4.

"We believe the characteristics of HPN217 – including its structure as a single flexible polypeptide, low molecular weight, and in vitro and in vivo stability with half-life extension – offer advantages over conventional bispecific antibodies targeting BCMA," said Che-Leung Law, PhD, Harpoon's Vice President, Translational Medicine. "Supported by preclinical data showing tumor growth inhibition in models of multiple myeloma and mantle cell lymphoma, HPN217 is expected to enter a Phase 1 clinical trial for multiple myeloma in 2019."

“Recent clinical data has validated the importance of BCMA as a drug target for T cells in the treatment of multiple myeloma," said Gerald McMahon, PhD, President and Chief Executive Officer of Harpoon. "The introduction of our third TriTAC compound demonstrates the ability of our technology platform to generate new product candidates."

The poster entitled “Preclinical and Nonclinical Characterization of HPN217: A Tri-specific T cell Activating Construct (TriTAC) Targeting B Cell Maturation Antigen (BCMA) for the Treatment of Multiple Myeloma” can be found on the Publications page of Harpoon’s website.

Key information presented includes:

Design of HPN217 TriTAC

The design of HPN217 is based on Harpoon’s novel TriTAC platform. It is a single polypeptide consisting of three domains that recognize human BCMA for myeloma cell targeting, serum albumin for half-life extension, and CD3ε for T cell engagement.

Proof-of-concept In Vitro and In Vivo Preclinical Studies

HPN217 demonstrated BCMA- and T cell-dependent antitumor activity in tissue culture and in xenografts modeling multiple myeloma and lymphoma. Effective preclinical antitumor activities could be observed in models with BCMA receptor copy number as low as approximately 2,200 per cell.

Pharmacokinetics Properties and In Vivo Stability in Nonclinical Studies

In animal studies, HPN217 demonstrated a circulating terminal half-life of 70-84 hours. Importantly, HPN217 remained functionally intact after one week in circulation.

About Multiple Myeloma

Multiple myeloma is the second most prevalent blood cancer after Non-Hodgkin’s lymphoma. There are approximately 229,000 people living with myeloma worldwide, with 114,000 new cases diagnosed and 87,000 deaths each year. The American Cancer Society estimates that approximately 30,700 new cases will be diagnosed and approximately 12,770 deaths are expected to occur from multiple myeloma in the United States in 2018. Despite advances in the treatment of multiple myeloma over the past decade, there remains a significant unmet need.

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 TriTAC platform, Harpoon is developing a pipeline of novel T cell engagers, or TriTACs, and is initially focused on the treatment of solid tumors and hematologic malignancies. Harpoon’s first drug candidate, HPN424, is currently in a Phase 1 clinical trial as a treatment for prostate cancer. For more information, please visit

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Last Updated: 02-Dec-2018