Quinocycline B, also known as PA-371-D'', is a synthetic tetracycline derivative with broad-spectrum antibacterial and potential anticancer properties. It was originally developed for its antimicrobial activity but has since attracted interest for its ability to inhibit tumor cell growth, particularly in drug-resistant cancer cells. Quinocycline B functions by targeting mitochondrial function and inducing apoptosis through pathways independent of p53, making it a promising candidate for overcoming resistance mechanisms in cancer therapy.