Covalent molecules (namely TOS-358) achieved complete inhibition of pathway signaling in this format. Overall, this reveals the need to achieve sustained inhibition of both PI3Kα mutant and wild type signaling to achieve durable efficacy in PI3Kα mutant tumors.
Furthermore, we elucidate that previous reversible PI3Kα inhibitors lead to dramatic hyperglycemia due to their potent inhibition of multiple PI3K isoforms at effective concentrations of the molecules in a cellular setting. This data reveals that highly specific and potent covalent inhibition of PI3Kα leads to dramatically superior efficacy and an improved safety profile.
We furthermore utilized this assay to explore the turnover rate of PI3Kα across multiple diverse tumor types, mutations, and tissues. This approach enables highly sensitive target engagement analysis of TOS-358 across multiple formats.