Furthermore, we here demonstrated that in vivo intraperitoneal treatment of stERAP-6 every 4 days (1.4 mg kg−1 and 14 mg kg−1, TGI: 103.7% and 103.3%, respectively) resulted in enhanced suppression of E2-induced tumour progression in mice bearing KPL-3C breast cancer cells compared with unstapled, original ERAP (1.4 mg kg−1 and 14 mg kg−1, TGI: 36.9% and 40.3%, respectively), further illustrating that stERAP enhances these suppression due to the prolonged inhibition of BIG3-PHB2 interaction via higher PHB2-binding affinity than unstapled original ERAP. Here, PHB2 is linked to breast cancer.