Abstract 2096: A novel, orally available ferroptosis inducer targeting Fe-S assembly with significant in vivo anti-tumor efficacy
Authors: Green Yangsook Song , Santos Maria Ferreira dos , Ciofi-Baffoni Simone , Liu Xiaohui , Koh Mei Yee 
Published: March 2024

Background: Ferroptosis is a novel form of cell death driven by iron-dependent lipid peroxidation, which disrupts cellular membranes resulting in immune-activating death. A variety of tumor types, particularly those associated with enhanced lipid and/or iron content, or which experience increased oxidative stress (including drug tolerant persister cells), are sensitive to ferroptosis, rendering ferroptosis a promising therapeutic strategy for cancer. However, currently available ferroptosis inducers show limited activity in vivo, suggesting a need for novel molecular targets to validate the clinical utility of ferroptosis induction. Clear cell renal cell carcinoma (ccRCC), the most common form of kidney cancer, is typically initiated by inactivation of VHL resulting in constitutive activation of HIF-1α and HIF-2α, which contribute to disease progression, including by promoting lipid accumulation that sensitizes ccRCC cells to ferroptosis.

Methods: We performed a high-throughput screen to identify small molecule inhibitors of HIF-2α followed by structure-activity-relationship studies for validation. The molecular target of these inhibitors was identified using the Drug Affinity Responsive Target Stability assay, and target validation was confirmed using siRNA and NMR. In vitro efficacy was determined in a panel of cancer cell lines and in vivo anti-tumor efficacy was verified using mouse models of cancer.

Results: We identified a novel molecule, KD061, which decreases HIF-1/2α and induces ferroptosis in vivo through oral administration by targeting Iron Sulfur Cluster Assembly 2 (ISCA2). ISCA2 is a component of the late mitochondrial Iron Sulfur Cluster (L-ISC) assembly complex and ISCA2 inhibition either pharmacologically or using siRNA triggers the iron starvation response, resulting in iron/metals overload and death via ferroptosis. ISCA2 inhibition also decreases HIF-2α protein levels by blocking iron-responsive element (IRE)-dependent translation, and at higher concentrations, also decreases HIF-1α translation. These studies reveal a novel function of ISCA2 in extra-mitochondrial Fe-S assembly that may be limiting in cancer due to the increased need for these proteins in DNA replication and maintenance. Outside of ccRCC, a 92-cell line screen reveals a variety of tumor types sensitive to ISCA2 inhibition including melanoma and clear cell ovarian cancer. Treatment of tumor-bearing mice with KD061 resulted in &gt; 65% tumor growth inhibition, associated with significantly increased lipid peroxidation, thus confirming ferroptosis in vivo, and with decreased HIF-1/2α. The anti-tumor efficacy of KD061 exceeded that of α-PD1 and was well tolerated at the therapeutic dose.

Conclusions: We describe the first orally available inducer of ferroptosis with significant anti-tumor efficacy in ccRCC and other tumor types.

Citation Format: Yangsook Song Green, Maria Ferreira dos Santos, Simone Ciofi-Baffoni, Xiaohui Liu, Mei Yee Koh. A novel, orally available ferroptosis inducer targeting Fe-S assembly with significant in vivo anti-tumor efficacy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2096.