ESR1 and squamous cell lung carcinoma: For example, clinical studies have demonstrated that Fexagratinib (AZD4547), an FGFR inhibitor, shows moderate anti-tumor activity in patients with advanced squamous cell lung cancer (SQCLC) harboring FGFR1 amplification, but its effectiveness in estrogen receptor-positive metastatic breast cancer is suboptimal, with patients experiencing significant adverse effects [96].