TAIPEI, Taiwan, April 29, 2025 — AP Biosciences, a biopharmaceutical company in clinical trials focused on transforming cancer treatment through innovative bispecific antibodies, today announced the presentation of new preclinical findings for its primary asset, AP402, at the 2025 American Association for Cancer Research (AACR) Annual Meeting in San Diego, California.
The data, shared in a poster presentation titled “AP402, a bispecific antibody targeting p95HER2 and CD137, shows potent antitumor activity,” emphasize AP402’s therapeutic potential in addressing HER2-positive cancers resistant to treatment through conditional T-cell engagement.
“The results presented at AACR strengthen the case for moving AP402 into clinical trials,” said Jeng Her, Ph.D., Founder and Chief Executive Officer of AP Biosciences. “By selectively targeting p95HER2—a HER2 isoform implicated in therapeutic resistance—and conditionally activating CD137, AP402 provides a unique mechanism for recruiting and stimulating immune effector cells while reducing the risk of systemic toxicity. These data highlight the effectiveness of our T-cube platform in delivering targeted immune activation precisely within the tumor microenvironment.”
Results Summary
- Specificity for p95HER2: AP402 exhibits high-affinity binding to p95HER2, confirming its selectivity for the truncated isoform over the full-length HER2.
- T-cell Activation: In co-culture assays, AP402 stimulated significant IFN-γ secretion from T cells, with activity related to p95HER2 expression on target cells. AP402 demonstrated synergistic T-cell activation compared to combination treatments using individual parental antibodies.
- Activation Across Multiple Cell Lines: AP402 induced strong IFN-γ responses in several p95HER2-expressing cancer cell lines (e.g., SK-OV-3), demonstrating its potential across various 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, indicating its engagement of innate immune mechanisms.
- Efficacy in Cell Line-Derived and Patient-Derived Xenograft Models: AP402 treatment resulted in significant tumor regression in both CDX and p95HER2-positive breast cancer PDX models.
- Pharmacokinetics and Toxicology in Non-Human Primates (NHPs): AP402 showed a favorable pharmacokinetic profile in cynomolgus monkeys 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 indicate that AP402 effectively engages innate and adaptive immune responses, demonstrates strong antitumor activity in p95HER2-expressing tumor models, and is well tolerated in non-human primates. These results support the continued development of AP402, which recently began clinical evaluation in Australia ().
About AP402
AP402 is a first-in-class bispecific antibody created by AP Biosciences to target p95HER2, a HER2 variant linked to Herceptin resistance and a poorer prognosis. This variant is found in roughly 30–40% of HER2-positive breast cancer patients. By using p95HER2 recognition to cluster CD137, the design enables localized T-cell activation within the tumor microenvironment, helping to lower systemic cytokine-related toxicity. The binding domains for p95HER2 and CD137 are strategically positioned on opposite ends to improve bridging between HER2 variant-expressing cancer cells and CD137-expressing T-cells, ensuring efficient immune cell recruitment without spatial hindrance. This innovative mechanism makes AP402 a promising therapeutic option for tumors resistant to traditional anti-HER2 therapies, offering new potential for patients with refractory/recurrent cancers.
About AP Biosciences
AP Biosciences is a clinical-stage biopharmaceutical company based in Taiwan dedicated to developing innovative antibody-based therapies for cancer and other diseases. Utilizing its proprietary Omni-Mab and T-cube platforms, AP Biosciences is pioneering next-generation bispecific antibodies that activate the immune system precisely where needed, for both established and treatment-resistant cancers.
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