Abstract 328: A novel human-like asparaginase - indication expansion made possible

Abstract L-asparaginase (ASNase) has been a cornerstone of pediatric acute lymphoblastic leukemia (ALL) treatment since the 1970s, leveraging a unique mechanism that exploits the metabolic vulnerability of leukemic cells. Cancer cells deficient in asparagine synthetase (ASNS), which rely on blood asparagine, are starved when ASNase depletes asparagine in the bloodstream. While this approach is effective in ALL, preclinical studies suggest that ASNase could also target other ASNS-deficient (ASNSlow) cancers, including acute myeloid leukemia (AML) and subsets of solid tumors like liver and colorectal cancers. However, the severe toxicity of existing ASNase formulations, largely due to off-target glutaminase activity and immunogenicity, has limited its broader clinical application. To overcome these barriers, we developed a novel human-like mammalian ASNase designed to minimize immunogenicity and eliminate glutaminase-driven toxicity while maintaining high specificity for asparagine. This engineered ASNase demonstrated robust in vitro and in vivo efficacy against both T-cell and B-cell ALL. Notably, it also showed potent activity as a monotherapy in AML, eradicating tumor cells in blood and bone marrow. Beyond blood cancers, this ASNase displayed significant anti-tumor effects against a CRISPR/CAS-9-engineered melanoma model with genetic loss of ASNS and a hepatocellular carcinoma model with low endogenous ASNS expression, achieving durable tumor suppression. This demonstrates that for ASNSlow tumors the glutaminase activity is not required for efficacy. Crucially, the novel ASNase was well tolerated in animal studies, enabling prolonged asparagine depletion—an essential factor for its striking anti-cancer effects. With its enhanced safety profile and specificity, this humanized ASNase represents a transformative advancement, extending the benefits of metabolic tumor starvation to a broader range of cancers. Its predictable mechanism of action, guided by biomarkers of ASNSlow status, positions it as a promising therapeutic breakthrough for targeting diverse malignancies. The authors used GPT-4.o in order to rephrase certain sentences. After using this tool or service, the authors reviewed and edited the content as needed and take full responsibility for the content of the publication. Citation Format: Amanda M. Schalk, Maaike Van Trimpont, Ying Su, Ashley De Loera, Alyssa Garcia, Tim Lammens, Steven Goossens, Arnon Lavie. A novel human-like asparaginase - indication expansion made possible [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 328.