Structural optimization and biological evaluation of 5-fluoro-7H-pyrrolo[2,3- d]pyrimidine derivatives as potent FAK inhibitors for the treatment of triple negative breast cancers (TNBC).

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that plays a crucial role in cancer progression. It is involved in processes such as cell adhesion, motility, proliferation, and survival, and it contributes to tumor drug resistance and malignant transformation. In the present study, we performed structural optimization on a FAK inhibitor previously reported by us, 2-((2-((3-acetamidophenyl)amino)-5-fluoro-7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino)-N-methylbenzamide (compound 1). This effort led to the development of compound 7h, which exhibited a 28-fold increase in FAK inhibitory potency (IC = 0.5 nM), a 17-fold enhancement in solubility in phosphate buffered saline (PBS), and improved metabolic stability in liver microsomes compared to the original hit compound (1). Kinase selectivity profiling demonstrated that compound 7h potently and selectively inhibits FAK with minimal off-target effects. Mechanistically, 7h induces cell cycle arrest in the G2/M phase and promotes late apoptosis in Triple Negative Breast Cancer (TNBC)-derived MDA-MB-231 cells. In xenograft mouse models, 7h (10 mg/kg) achieved a 61.8 % tumor growth inhibition compared to the control group, exceeding the efficacy of paclitaxel (54.8 %) and demonstrating no observable toxicity via intravenous administration. These results indicate that 7h is a potent FAK inhibitor with optimized pharmacokinetics and safety profiles, supporting its potential as a promising therapeutic candidate for the treatment of TNBC.