AP Biosciences Presents Preclinical Data on p95HER/CD137 T-Cell Engager at American Association of Cancer Research Annual Meeting

TAIPEI, Taiwan, April 29, 2025 (GLOBE NEWSWIRE) -- AP Biosciences, a clinical-stage biopharmaceutical company dedicated to transforming cancer therapy through innovative bispecific antibodies, today announced the presentation of new preclinical data for its lead asset, AP402, at the 2025 American Association for Cancer Research (AACR) Annual Meeting in San Diego, California.

The data, presented in a poster titled "AP402, a bispecific antibody targeting p95HER2 and CD137, shows potent antitumor activity," highlight the therapeutic potential of AP402 to address treatment-resistant HER2-positive cancers through conditional T-cell engagement.

“The findings presented at AACR reinforce the rationale for advancing AP402 into clinical studies,” said Jeng Her, Ph.D., Founder and Chief Executive Officer of AP Biosciences. “By selectively targeting p95HER2—a truncated HER2 isoform implicated in therapeutic resistance—and conditionally activating CD137, AP402 offers a unique mechanism to recruit and stimulate immune effector cells while minimizing the risk of systemic toxicity. These data demonstrate the strength of our T-cube platform in delivering targeted immune activation precisely within the tumor microenvironment.”

Results Summary

• Specificity for p95HER2: AP402 demonstrates high-affinity binding to p95HER2, confirming its selectivity for the truncated isoform over full-length HER2.
• T-cell Activation: In co-culture assays, AP402 promoted robust IFN-γ secretion from T cells, with activity correlating to p95HER2 expression on target cells. Compared to combination treatments with individual parental antibodies, AP402 showed synergistic T-cell activation.
• Activation Across Multiple Cell Lines: AP402 induced strong IFN-γ responses in multiple p95HER2-expressing cancer cell lines (e.g., SK-OV-3), demonstrating its potential applicability across tumor types.
• Antibody-Dependent Cellular Cytotoxicity (ADCC): AP402 induced dose-dependent ADCC activity in p95HER2-expressing MDA-MB-231 cells using CD16-NK-92MI effector cells. Cytotoxicity levels were positively correlated with p95HER2 expression.
• Antibody-Dependent Cellular Phagocytosis (ADCP): AP402 triggered macrophage-mediated phagocytosis of p95HER2+ tumor cells in vitro, supporting its engagement of innate immune mechanisms.
• Efficacy in Cell Line-Derived and Patient-Derived Xenograft Models: In both CDX and p95HER2-positive breast cancer PDX models, AP402 treatment resulted in significant tumor regression.
• Pharmacokinetics and Toxicology in Non-Human Primates (NHPs): In cynomolgus monkeys, AP402 demonstrated a favorable pharmacokinetic profile and was well tolerated up to 100 mg/kg with no observed adverse effects at the highest dose. All findings reversed during the recovery phase.
  

In conclusion, the preclinical data show that AP402 effectively engages innate and adaptive immune responses, demonstrates robust antitumor activity in p95HER2-expressing tumor models, and is well tolerated in non-human primates. These findings support the continued development of AP402, which recently entered clinical evaluation in Australia (NCT06669975).

About AP402

AP402 is a first-in-class bispecific antibody developed by AP Biosciences to target p95HER2, a truncated variant of HER2 associated with resistance to Herceptin and poorer prognosis. This variant is present in approximately 30–40% of HER2-positive breast cancer patients. By leveraging p95HER2 recognition to cluster CD137, the design enables localized T-cell activation within the tumor microenvironment, helping to minimize systemic cytokine-related toxicity. The binding domains for p95HER2 and CD137 are strategically positioned on opposite ends to enhance bridging between HER2 variant-expressing cancer cells and CD137-expressing T-cells, ensuring efficient immune cell recruitment without spatial hindrance. This novel mechanism has positioned AP402 as a promising therapeutic approach to addressing tumors that have developed resistance to traditional anti-HER2 therapies, offering potential new hope for patients with refractory/recurrent cancers.

About AP Biosciences

AP Biosciences is a Taiwan-based clinical-stage biopharmaceutical company committed to developing innovative antibody-based therapies for cancer and other diseases. Applying its proprietary Omni-Mab and T-cube platforms, AP Biosciences is pioneering next generation bispecific antibodies that activate the immune system precisely where it’s needed, for both established and treatment-resistant cancers.

AP Biosciences Contact

Spike Lo

AP Biosciences

pr@apbioinc.com

+886-2-2653-2886

Media Contact

Jason Braco, PhD

LifeSci Communications

jbraco@lifescicomms.com

(908)-432-4243