Phase 1


Spearheading Immunotherapies


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 tumours and hematologic malignancies.

Harpoon's lead TriTAC product candidate, HPN424, is currently in a Phase 1 clinical trial for the treatment of metastatic castration-resistant prostate cancer, or mCRPC. Its second TriTAC product candidate, HPN536, is expected to enter clinical development in the first half of 2019 for the treatment of ovarian cancer and other MSLN-expressing solid tumours. HPN217, targeting BCMA, is in pre-clinical development for the treatment of multiple myeloma. HPN328, targeting DLL3, is in pre-clinical development for the treatment for small cell lung cancer.


Harpoon has a strong management team with deep experience in immunotherapy, redirected T-cell therapies, biologics drug discovery and development and protein engineering. This team brings a strong history of research and development innovation and a proven track record at other companies in the discovery, development and commercialisation of oncology therapeutics.

  • Gerald McMahon, Chief Executive Officer and President
  • Natalie R. Sacks, Chief Medical Officer
  • Holger Wesche, Chief Scientific Officer
  • Georgia L. Erbez, Chief Financial Officer
  • Susan Dana Jones, Senior Vice President, Product Development
  • Rachael Lester, VP of Corporate Development
  • Che-Leung Law, VP of Translational Medicine

Unmet need and market opportunity

Solid tumours comprise a large set of diverse cancers, including prostate, ovarian, lung, and pancreatic. Prostate cancer is expected to have the second highest incidence rate in 2018 and the third highest mortality rate in 2018, including being the second leading cause of male cancer death in the United States. Ovarian cancer is the fifth leading cause of cancer-related death among women in the United States and is the deadliest of the gynecologic cancers with more than 70% of patients diagnosed with an advanced stage and over 14,000 patients dying from the disease each year. According to SEER, the five-year survival rate for women diagnosed with ovarian cancer is approximately 47%. Non-small cell lung cancer (NSCLC) is the most common type of lung cancer, estimated to comprise 80-85% of all lung cancer diagnoses. The five-year survival rate for late-stage NSCLC is about 10%. Pancreatic cancer is one of the most fatal cancers in the world. Of the 55,440 new cases in the United States, SEER estimates that fewer than 9% of patients diagnosed with pancreatic cancer survive five years.

While the five-year survival rate of local and regional prostate cancer is nearly 100%, more aggressive forms of the disease, of which approximately 23% are initially diagnosed, have a five-year survival rate of approximately 30%. Nearly all prostate cancer-specific deaths occur after patients develop mCRPC, for which the median overall survival period is only 13 months. Later-generation anti-androgen drugs such as Johnson & Johnson's Zytiga and Pfizer's/Astellas' Xtandi have widely become the standard of care and generated combined global sales of over $5bn in 2017. There is a significant need for treatments that offer a novel mechanism of action with the potential to modify or cure the disease.

Novel technology: TriTAC – T-cell engagers for solid tumours

Harpoon's proprietary TriTAC™ (Tri-specific T-cell Activating Construct) platform offers the potential to develop drugs that could dramatically change the way in which we combat a variety of diseases. The bi-specific T-cell engager, Blincyto®, was approved in 2014 as a monotherapy treatment of acute lymphoblastic leukaemia (ALL). TriTACs, which are comprised of three binding domains, are designed to have an extended serum half-life and be about one-third the size of a monoclonal antibody.


TriTAC offers distinct advantages

  • Extended half life and stability: Stable in bloodstream and long-serum half-life allows for convenient dosing (weekly)
  • Active at low levels of antigen expression: Does not require high levels of target antigen expression to engage T-cells to kill disease cells
  • MHC Independence: Direct T-cells to kill targeT-cells independent of MHC expression with expectation for more durable therapeutic responses than MHC dependent approaches
  • Small size and tissue penetration: Small size (expected to allow for faster diffusion into human solid tumour tissue


Stage of development
Product candidateTarget/IndicationPre-clinicalPHASE 1PHASE 2PHASE 3Anticipated Milestones
Prostate Cancer
H2 2019: Additional preliminary Phase 1 data
Ovarian Cancer and Other Solid Tumours
H2 2019: Initiate Phase 1/2a
Multiple Myeloma
H2 2019: Initiate Phase 1
Small Cell Lung Cancer
H2 2020: Initiate Phase 1

Milestones achieved

  • Initiated first clinical trial In 2018; first patient dosed in HPN424 trial for Prostate Cancer
  • Announced preliminary data from Phase 1 clinical trial of HPN424 (Prostate Cancer) in January 2019
  • Successful NASDAQ IPO in February 2019, raising $81m of gross proceeds

Anticipated milestones

  • H2 2019: Additional preliminary Phase 1 data from HPN424 (Prostate Cancer)
  • H2 2019: Initiation of Phase 1/2a trial for HPN536 (Ovarian Cancer and other MSLN-expressing solid tumours)
  • H2 2019: Initiation of Phase 1 HPN217 (Multiple Myeloma) trial
  • H2 2020: Initiation of Phase 1 trial of HPN328 (Small Cell Lung Cancer)