A Novel Squaramide Derivative, HR-19011, Induces the Integrated Stress Response via the HRI–eIF2α–ATF4 Pathway, Effectively Inhibiting Hematologic Malignancies

We investigated the therapeutic potential and mechanisms of HR-19011, a novel eukaryotic translation initiation factor 2 subunit α (eIF2α) phosphorylation inducer, with a focus on its effects on the integrated stress response (ISR) pathway and cell-cycle regulation in K562 cells. Our findings revealed that HR-19011 exerts its anticancer effects primarily through the activation of heme-regulated inhibitor (HRI), leading to the phosphorylation of eIF2α, the induction of ISR signaling, and subsequent G1/S cell-cycle arrest. RNA sequencing analysis further highlighted significant changes in gene expression associated with the ISR pathway, particularly those involving the key components, activating transcription factor 4 and CHOP, underscoring the specific targeting of HRI by HR-19011. Additionally, HR-19011 suppressed the mTORC1 pathway, a critical regulator of cell growth and metabolism, through the downregulation of components such as phosphorylated S6K and phosphorylated 4EBP1, mediated by activating transcription factor 4 and CHOP. In vivo studies demonstrated that HR-19011 effectively inhibited tumor growth in a K562 xenograft model, without significant toxicity, and its broad efficacy across various hematologic malignancies further suggests its potential as a versatile anticancer agent. Our findings position HR-19011 as a promising candidate for targeting the HRI-eIF2α axis in cancer treatment, warranting further investigation and optimization for clinical application.