HS-10296 (almonertinib) enhances radiosensitivity in EGFR-mutant nonsmall cell lung cancer (including T790M) through inhibition of EGFR downstream signaling and DNA damage repair.

Nonsmall cell lung cancer (NSCLC) harboring EGFR mutations, including the resistant T790M variant, continues to require improved therapeutic strategies despite the development of EGFR tyrosine kinase inhibitors (TKIs). This study evaluates the radiosensitizing potential of HS-10296 (almonertinib), a third-generation EGFR-TKI, in EGFR-mutant NSCLC models. In vitro studies demonstrated selective growth inhibition in mutant cells (PC-9: half-maximal inhibitory concentration (IC50) = 2.62 μM; H1975: IC50 = 5.22μM at 48 h) compared to wild-type A549 cells (IC50 = 11.42 μM). Clonogenic assays revealed significant radiosensitization in mutant cells (SER: PC-9 = 1.22; H1975 = 1.55) through multiple mechanisms including enhanced DNA damage (1.5-2.0-fold increase in comet tail moments with 4-10× persistent γH2A.X foci), marked suppression of RAD51-mediated DNA repair, and increased apoptosis (combination therapy: 19.53%-20.71% versus monotherapies: 12.08%-14.05%). Mechanistic investigation showed HS-10296 attenuated phosphorylation of EGFR and downstream effectors AKT and ERK, potentially disrupting DNA damage response pathways. In vivo validation using H1975 xenografts demonstrated superior tumor growth inhibition with the combination of HS-10296 and radiotherapy, which correlated with reduced expression of p-EGFR, p-AKT, and RAD51, along with increased γH2A.X levels. These findings establish HS-10296 as a promising radiosensitizer for EGFR-mutant NSCLC through simultaneous targeting of oncogenic signaling via PI3K/AKT and MAPK/ERK pathways and critical DNA repair mechanisms. The study provides compelling preclinical evidence supporting clinical evaluation of HS-10296 combined with radiotherapy for EGFR-driven NSCLC, including tumors with T790M-mediated resistance.