PIK3CA mutation has been recommended as a sensitive biomarker for the approved PI3Kα inhibitor alpelisib in combination with fulvestrant for the treatment of HR-positive, HER2-negative advanced breast cancer.13 Accordingly, we found that ESCC PDXs with PIK3CA mutation were sensitive to CYH33. Here, ERBB2 is linked to esophageal squamous cell carcinoma.