Compound A8(University of Chinese Academy of Sciences)

The integrated stress response (ISR) is a eukaryotic stress-responsive signaling pathway that attenuates global protein synthesis while allowing selective translation of specific mRNAs, which together can reestablish homeostasis following acute stress. Diverse pathologic insults activate one or more of the four ISR kinases, which selectively phosphorylate eIF2α to mediate ISR functions. Recent results suggest that enhancing ISR kinase activity could ameliorate pathologies linked to numerous diseases, including many neurodegenerative disorders. However, few pharmacological strategies exist to selectively activate ISR kinases and downstream adaptive signaling. Here, we report that compound A8 can preferentially activate the ISR through the binding of the cytosolic pattern recognition receptor RIG-I, which subsequently activates the heme-regulated inhibitor (HRI) ISR kinase independent of an interferon response. The establishment of A8 and its active metabolite CC81 provides opportunities to probe the biological and therapeutic relationship between innate immune signaling and ISR activation in health and disease.

FAK has emerged as a promising therapeutic target for cancer treatment due to its role in tumor survival, metastasis, and invasion. Herein, we report the rational design, synthesis, and comprehensive evaluation of a novel FAK inhibitor, compound A8. Our structure-activity relationship (SAR) studies identified A8 as a potent FAK inhibitor, with an FAK-IC₅₀ value of 0.87 nM, superior to VS6063 (1.49 nM). In vitro studies demonstrated that A8 significantly suppressed tumor cell viability, cancer stem cell activity, and cell migration in A549 and SKOV-3 cell lines. Mechanistic insights were provided by surface plasmon resonance (SPR) analysis, revealing high-affinity binding of A8 to FAK with a Kd value of 15 μM. Radiolabeling studies with [¹⁸F]A8 highlighted favorable tumor uptake and retention in S180 tumor-bearing mice. Notably, A8 efficiently penetrated the blood-brain barrier, with brain uptake values reaching 2.63 ± 0.63 %ID/g at 15 min and 1.62 ± 0.77 %ID/g at 120 min. In vivo antitumor efficacy trials in A549 and SKOV-3 tumor models confirmed A8's robust activity, with tumor inhibition rates of 59.15 % and 57.9 %, respectively, surpassing VS6063 and standard chemotherapeutics. Combination therapy with paclitaxel further enhanced A8's antitumor effects in SKOV-3 models. Acute toxicity studies indicated that A8 was well-tolerated up to 2000 mg/kg in mice, with no observed acute toxicity. Molecular docking and dynamics simulations substantiated the stable binding of A8 to the FAK protein. Collectively, our findings underscore the potential of compound A8 as a lead candidate for FAK-targeted cancer therapeutics, warranting further preclinical and clinical investigations.