Effluxremmers

Effluxremmers, or efflux pump inhibitors (EPIs), are compounds that inhibit cellular efflux pumps—proteins that actively transport a wide range of substrates out of cells. By blocking these pumps, EPIs can raise the intracellular concentration of drugs such as antibiotics, antifungals, or anticancer agents, potentially restoring or enhancing their effectiveness against resistant organisms or cells.

Mechanisms include direct blockade of the pump's substrate-binding site, inhibition of ATP hydrolysis in ATP-binding cassette transporters, disruption of proton motive force in proton-driven transporters, or downregulation of pump expression. Efflux pumps belong to several families, including the bacterial RND, MFS, MATE, and ABC transporters, and in humans the P-glycoprotein (ABCB1), MRP1 (ABCC1), and BCRP (ABCG2) pumps.

Applications and contexts: In bacteria, efflux pumps contribute to multidrug resistance and are a target for adjuvant therapies alongside antibiotics. In cancer, efflux pumps are a major mechanism of multidrug resistance, limiting the efficacy of chemotherapeutics. In fungi and yeasts, efflux can underlie resistance to azoles and other antifungals.

Clinical development has faced challenges. Most EPIs have limited clinical success due to toxicity, pharmacokinetic interactions with coadministered drugs, and redundancy among efflux systems. Only a few candidates have progressed to late-stage trials, and none has achieved broad approved use, though research continues.

Research directions include design of selective, low-toxicity inhibitors, use as adjuvants in combination therapies, and discovery of natural product–based inhibitors. Tools such as PAβN are used in laboratory studies to probe pump function, while newer third-generation inhibitors aim to improve specificity and safety.