{"entity":{"id":"drug-efflux-pumps","kind":"pathway","name":"Drug efflux pumps (ABC transporters)","aka":[],"tldr":"Cancer cells can install pumps in their outer membrane that throw chemotherapy back out as fast as it comes in. The same pumps guard the gut, brain and bone marrow in healthy tissue, which is why blocking them failed as a strategy and why drug designers now choose payloads the pumps cannot grip.","summary":"ATP-binding cassette transporters, chiefly ABCB1 (P-glycoprotein/MDR1), ABCG2 (BCRP) and ABCC1 (MRP1), hydrolyse ATP to export hydrophobic drugs: taxanes, vinca alkaloids, anthracyclines, MMAE, DM1, several TKIs (ABCB1); SN-38, topotecan, mitoxantrone, methotrexate (ABCG2). They are constitutive in intestine, liver, kidney, the blood-brain barrier and stem cells (including leukaemia and cancer stem cells, the 'side population'), and are induced by EMT transcription factors, hypoxia, NRF2 (KEAP1-mutant tumours), and by drug exposure itself (ABCB1 amplification and promoter fusions in ovarian cancer after taxanes). Three generations of P-gp inhibitors (verapamil, valspodar, tariquidar) failed in phase 3 through pharmacokinetic interactions and lack of benefit. Modern responses: choose payloads that are poor substrates (DXd and exatecan are less affected than SN-38 and MMAE; PBD dimers; radionuclides are pump-independent), use ADCs to raise intracellular delivery, and exploit collateral sensitivity (pump-expressing cells are more sensitive to some agents). Efflux at the BBB limits CNS activity of most drugs; brain-penetrant TKIs are engineered to evade P-gp.","asOf":"2026-09-09","wikipedia":"https://en.wikipedia.org/wiki/P-glycoprotein","links":[{"label":"Robey et al., Revisiting the role of ABC transporters in multidrug-resistant cancer (Nat Rev Cancer 2018)","url":"https://doi.org/10.1038/s41568-018-0005-8"}],"tags":["mechanism","mechanics-atlas"],"related":[],"cancers":[],"sections":[],"technologies":["adc","radioligand-therapy","cytotoxic-chemotherapy","topoisomerase-inhibitors"],"targets":["trop2","her2","kras","alk"],"drugs":["trastuzumab-deruxtecan","datopotamab-deruxtecan","sacituzumab-tirumotecan","sacituzumab-govitecan","enfortumab-vedotin","paclitaxel","doxorubicin","lorlatinib"],"companies":[],"institutions":[],"pathways":["emt","keap1-nrf2","blood-brain-barrier-metastasis","resistance-routes-map","cancer-stem-cells-plasticity"],"terms":["efflux-pump","payload","dxd","exatecan","sn-38","mmae","bystander-effect","adc-sequencing","resistance"],"trials":[],"people":[],"bottlenecks":["b-resistance"],"keyPapers":["paper-robey-nat-rev-cancer"],"journals":[],"dependsOn":[],"notes":[],"analogy":"A nightclub bouncer who throws out anyone in a particular jacket. Sacking the bouncer (P-gp inhibitors) also emptied the club of the staff who kept the place safe (gut, brain, marrow). The fix was to change jackets: payloads the bouncer does not recognise.","nodes":[{"id":"drug","label":"Chemo / payload enters","x":12,"y":30},{"id":"abcb1","label":"ABCB1 (P-gp)","x":45,"y":15},{"id":"abcg2","label":"ABCG2 (BCRP), ABCC1","x":45,"y":48},{"id":"out","label":"Drug exported (ATP)","x":78,"y":30},{"id":"conc","label":"Sub-lethal intracellular dose","x":78,"y":62},{"id":"ind","label":"EMT, hypoxia, NRF2 induce","x":12,"y":62,"targetId":"kras"},{"id":"bbb","label":"BBB, stem cells, marrow","x":12,"y":90},{"id":"payload","label":"Non-substrate payloads (DXd)","x":45,"y":82,"targetId":"trop2"},{"id":"kill","label":"Cell death","x":78,"y":92}],"edges":[{"from":"drug","to":"abcb1","type":"activates"},{"from":"drug","to":"abcg2","type":"activates"},{"from":"abcb1","to":"out","type":"activates"},{"from":"abcg2","to":"out","type":"activates"},{"from":"out","to":"conc","type":"activates"},{"from":"conc","to":"kill","type":"inhibits"},{"from":"ind","to":"abcb1","type":"activates"},{"from":"ind","to":"abcg2","type":"activates"},{"from":"bbb","to":"abcb1","type":"activates"},{"from":"payload","to":"abcb1","type":"inhibits"},{"from":"payload","to":"kill","type":"activates"}],"interventions":["Payload selection: DXd and exatecan (T-DXd, Dato-DXd, sac-TMT) retain activity where MMAE and SN-38 are pumped out; PBD dimers and radionuclides are pump-independent","Brain-penetrant TKIs engineered to evade P-gp (lorlatinib, tucatinib, osimertinib)","P-gp inhibitors (valspodar, tariquidar, zosuquidar) failed in phase 3; a museum exhibit","Collateral sensitivity and MDR-selective compounds are experimental"]},"route":"/pathways/drug-efflux-pumps/","neighbours":{"technology":[{"id":"adc","kind":"technology","name":"Antibody-drug conjugate (ADC)","route":"/technologies/adc/"},{"id":"cytotoxic-chemotherapy","kind":"technology","name":"Cytotoxic chemotherapy","route":"/technologies/cytotoxic-chemotherapy/"},{"id":"radioligand-therapy","kind":"technology","name":"Radioligand therapy (beta emitters)","route":"/technologies/radioligand-therapy/"},{"id":"topoisomerase-inhibitors","kind":"technology","name":"Topoisomerase-I inhibitors (and ADC payloads)","route":"/technologies/topoisomerase-inhibitors/"}],"target":[{"id":"abcb1","kind":"target","name":"ABCB1","route":"/targets/abcb1/"},{"id":"abcc1","kind":"target","name":"ABCC1","route":"/targets/abcc1/"},{"id":"abcg2","kind":"target","name":"ABCG2","route":"/targets/abcg2/"},{"id":"alk","kind":"target","name":"ALK","route":"/targets/alk/"},{"id":"her2","kind":"target","name":"HER2","route":"/targets/her2/"},{"id":"kras","kind":"target","name":"KRAS","route":"/targets/kras/"},{"id":"nfe2l2","kind":"target","name":"NFE2L2","route":"/targets/nfe2l2/"},{"id":"trop2","kind":"target","name":"TROP2","route":"/targets/trop2/"}],"drug":[{"id":"datopotamab-deruxtecan","kind":"drug","name":"Datopotamab deruxtecan","route":"/drugs/datopotamab-deruxtecan/"},{"id":"doxorubicin","kind":"drug","name":"Doxorubicin","route":"/drugs/doxorubicin/"},{"id":"enfortumab-vedotin","kind":"drug","name":"Enfortumab vedotin","route":"/drugs/enfortumab-vedotin/"},{"id":"lorlatinib","kind":"drug","name":"Lorlatinib","route":"/drugs/lorlatinib/"},{"id":"paclitaxel","kind":"drug","name":"Paclitaxel / nab-paclitaxel","route":"/drugs/paclitaxel/"},{"id":"sacituzumab-govitecan","kind":"drug","name":"Sacituzumab govitecan","route":"/drugs/sacituzumab-govitecan/"},{"id":"sacituzumab-tirumotecan","kind":"drug","name":"Sacituzumab tirumotecan","route":"/drugs/sacituzumab-tirumotecan/"},{"id":"trastuzumab-deruxtecan","kind":"drug","name":"Trastuzumab deruxtecan","route":"/drugs/trastuzumab-deruxtecan/"}],"pathway":[{"id":"cancer-stem-cells-plasticity","kind":"pathway","name":"Cancer stem cells & phenotypic plasticity","route":"/pathways/cancer-stem-cells-plasticity/"},{"id":"emt","kind":"pathway","name":"Epithelial-mesenchymal transition & drug efflux","route":"/pathways/emt/"},{"id":"keap1-nrf2","kind":"pathway","name":"KEAP1-NRF2 antioxidant pathway","route":"/pathways/keap1-nrf2/"},{"id":"resistance-routes-map","kind":"pathway","name":"Resistance routes: how a blocked pathway comes back","route":"/pathways/resistance-routes-map/"},{"id":"blood-brain-barrier-metastasis","kind":"pathway","name":"The blood-brain barrier & brain metastasis","route":"/pathways/blood-brain-barrier-metastasis/"}],"term":[{"id":"adc-sequencing","kind":"term","name":"ADC sequencing","route":"/terms/adc-sequencing/"},{"id":"bystander-effect","kind":"term","name":"Bystander effect (ADC)","route":"/terms/bystander-effect/"},{"id":"efflux-pump","kind":"term","name":"Drug efflux pumps (ABC transporters)","route":"/terms/efflux-pump/"},{"id":"resistance","kind":"term","name":"Drug resistance (primary and acquired)","route":"/terms/resistance/"},{"id":"dxd","kind":"term","name":"DXd","route":"/terms/dxd/"},{"id":"exatecan","kind":"term","name":"Exatecan (and derivatives)","route":"/terms/exatecan/"},{"id":"mmae","kind":"term","name":"MMAE","route":"/terms/mmae/"},{"id":"payload","kind":"term","name":"Payload (ADC)","route":"/terms/payload/"},{"id":"sn-38","kind":"term","name":"SN-38","route":"/terms/sn-38/"}],"bottleneck":[{"id":"b-resistance","kind":"bottleneck","name":"Acquired resistance to every therapy","route":"/bottlenecks/b-resistance/"}],"paper":[{"id":"paper-robey-nat-rev-cancer","kind":"paper","name":"Revisiting the role of ABC transporters in multidrug-resistant cancer","route":"/key-papers/paper-robey-nat-rev-cancer/"}]}}