Crofelemer was also evaluated in a prophylactic setting in a randomized open-label phase 2 study for the prevention of CTD in patients with HER2‐positive breast cancer receiving HER2 targeted therapy with trastuzumab, pertuzumab, and a taxane with/without carboplatin (HALT-D study) for two cycles [9]. Here, ERBB2 is linked to breast carcinoma.