Preclinical Characterization of HPN536, a Trispecific, T-Cell-Activating Protein Construct for the Treatment of Mesothelin-Expressing Solid Tumors

Clin Cancer Res. 2021 Mar 1;27(5):1452-1462. doi: 10.1158/1078-0432.CCR-20-3392. Epub 2020 Dec 1.


Purpose: Mesothelin (MSLN) is a glycophosphatidylinositol-linked tumor antigen overexpressed in a variety of malignancies, including ovarian, pancreatic, lung, and triple-negative breast cancer. Early signs of clinical efficacy with MSLN-targeting agents have validated MSLN as a promising target for therapeutic intervention, but therapies with improved efficacy are still needed to address the significant unmet medical need posed by MSLN-expressing cancers.

Experimental design: We designed HPN536, a 53-kDa, trispecific, T-cell-activating protein-based construct, which binds to MSLN-expressing tumor cells, CD3ε on T cells, and to serum albumin. Experiments were conducted to assess the potency, activity, and half-life of HPN536 in in vitro assays, rodent models, and in nonhuman primates (NHP).

Results: HPN536 binds to MSLN-expressing tumor cells and to CD3ε on T cells, leading to T-cell activation and potent redirected target cell lysis. A third domain of HPN536 binds to serum albumin for extension of plasma half-life. In cynomolgus monkeys, HPN536 at doses ranging from 0.1 to 10 mg/kg demonstrated MSLN-dependent pharmacologic activity, was well tolerated, and showed pharmacokinetics in support of weekly dosing in humans.

Conclusions: HPN536 is potent, is well tolerated, and exhibits extended half-life in NHPs. It is currently in phase I clinical testing in patients with MSLN-expressing malignancies (NCT03872206).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, Neoplasm / immunology
  • Apoptosis
  • Cell Proliferation
  • Female
  • Humans
  • Immunotherapy / methods*
  • Lymphocyte Activation / immunology*
  • Macaca fascicularis
  • Male
  • Mesothelin / antagonists & inhibitors*
  • Mice
  • Mice, Inbred NOD
  • Mice, SCID
  • Neoplasms / drug therapy*
  • Neoplasms / immunology
  • Neoplasms / metabolism
  • Neoplasms / pathology
  • Peptide Fragments / immunology
  • Single-Domain Antibodies / immunology
  • Single-Domain Antibodies / pharmacology*
  • T-Lymphocytes / immunology*
  • Tumor Cells, Cultured
  • Xenograft Model Antitumor Assays


  • Antigens, Neoplasm
  • MSLN protein, human
  • Peptide Fragments
  • Single-Domain Antibodies
  • Mesothelin

Associated data