ABCC5 (ATP-binding cassette subfamily C member 5) is an ATP-dependent organic anion transporter that mediates cellular efflux of diverse substrates. Functionally, ABCC5 exports endogenous metabolites including cyclic nucleotides (cAMP and cGMP), glutamate conjugates, folic acid, and heme 1. The transporter also confers resistance to antiviral nucleotide analogs and can transport anticancer drugs with low affinity, though its precise role in chemoresistance remains unclear 2. Structurally, ABCC5 contains a positive electrostatic substrate translocation chamber compatible with organic anion transport 3. Beyond drug resistance, emerging evidence reveals broader physiological roles for ABCC5. Knockout studies in animal models demonstrate its involvement in gut formation, brain development, eye development, and iron metabolism, with effects on adipocyte differentiation, insulin sensitivity, and glutamatergic signaling 1. In humans, ABCC5 genetic variants associate with anterior chamber depth and primary angle closure glaucoma susceptibility 4. Clinical relevance extends to doxorubicin-induced cardiotoxicity; ABCC5 knockout increased susceptibility of cardiomyocytes to doxorubicin, suggesting efflux transporter function protects against anthracycline cardiotoxicity 5. However, ABCC5's underappreciated physiological functions in the brain and reproductive system warrant caution against therapeutic targeting 1.