Lumacaftor, commonly known as Orkambi, is a drug used to treat specific variants (F508del) of cystic fibrosis, a disease in which the cystic fibrosis transmembrane conductance regulator protein becomes dysfunctional. It is combined with ivacaftor for treatment of cystic fibrosis.

Lumacaftor works as a protein folding chaperone to increase the number of CFTR proteins reaching the cell surface rather than being destroyed by the F508del mutation. Ivacaftor is a potentiator of CFTR already at the cell surface which ensures the defective channel will be open and allow chloride ions to flow through.

Common side effects include interference with hormonal contraceptives, respiratory discomfort upon initiating treatment and children may develop cataracts.