Abstract 1803: GNP101, anti-HER2-IFN-β mutein immunocytokine, for the treatment of Trastuzumab deruxtecan-resistant HER2-positive cancers
Authors: Lee Chan Gyu , Park Minkyung , Lee Hyun Kyung , Kim Na Young , Choi Jun Young , Hong Sungyoul , Shin Young Kee , Jeong Hae Min 
Published: April 2023

Abstract
Background: Trastuzumab deruxtecan (T-DXd) has been approved in various types cancer and recently expanded its indication to cancers with various HER2 expressions, such as HER2-low breast cancer. Since the effect of T-DXd is based on toxin payload, topoisomerase I inhibitor, the emergence of toxin-resistant cancer cells is unavoidable. Clinical cases of Primary, or secondary resistance to T-DXd have been reported. Therefore, it is necessary to develop novel drugs that can effectively exhibit antitumor effects against T-DXd-resistant carcinoma. Interferon beta (IFN-β), a promising potent cytokine, has been attracting attention for treatment of cancer. It is one of the few cytokines that induce tumor cell killing directly. Importantly, it could be an alternative to conventional drug-resistant cancer, because it regulates tumor growth in a way different from cytotoxic agents. Here, GNP101, an IFN-β mutein-based immunocytokine, exhibits antitumor properties against HER2-positive cancers, including T-DXd-resistant cancer.
Method: A panel of human HER2-positive cancer cell lines derived from breast, stomach and lung were treated with GNP101 or HER2 therapeutics (trastuzumab, T-DM1, T-DXd) to compare direct antitumor effects. To generate a T-DXd-resistant cells, HCC1954, NCI-N87 and Calu-3 were exposed to the IC50, IC80 or IC90 of T-DXd by cyclic treatment. After 4 months, HCC1954-R cells were established and IFN-β signaling was assessed by STAT1-phosphorylation. The direct antitumor effect of GNP101 in vivo was tested in HER2-positive cancer xenograft models.
Result: GNP101 showed superior potency compared to existing HER2 therapies (trastuzumab, T-DM1, and T-DXd) in all HER2-positive cancers regardless of tissue origin. To investigate the antitumor effect of GNP101 against T-DXd resistant cancer, we first generated T-DXd-resistant cell line (HCC1954-R). These HCC1954-R cells were strongly resistant to T-DXd, and showed no antitumor effect even at 100 nM of T-DXd. However, they were sensitive to GNP101, suggesting that GNP101 maintained its antitumor effect in T-DXd resistant cells. In addition, there was no difference in IFN-β-induced STAT1 phosphorylation between the parent cell and HCC1954-R. Taken together, these results indicate that HCC1954-R cells maintain IFN-β signaling and are selectively resistant to T-DXd. The activities of GNP101, T-DM1 and T-DXd on HER2-positive cancer cells were compared in vivo. GNP101 inhibited the growth of tumor by 90%, with no difference from that of T-DXd or T-DM1.
Conclusion: We have evaluated the antitumor properties of GNP101, a trastuzumab-IFN-β mutein in HER2-expressing cancer. Given that GNP101 retains its antitumor properties in T-DXd-resistant cancer cells, the study suggests that anti-HER2-IFN-β mutein is a promising candidate for the treatment of HER2-positive and T-DXd resistant cancers.
Citation Format: Chan Gyu Lee, Minkyung Park, Hyun Kyung Lee, Na Young Kim, Jun Young Choi, Sungyoul Hong, Young Kee Shin, Hae Min Jeong. GNP101, anti-HER2-IFN-β mutein immunocytokine, for the treatment of Trastuzumab deruxtecan-resistant HER2-positive cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1803.