A phase I and pharmacologic study of elacridar in combination with doxorubicin in patients with advanced solid tumors; elacridar pharmacokinetics were not influenced by coadministration of doxorubicin and produced only minimal side effects at a dose level yielding concentrations able to inhibit the action of P-gp in vitro (hematologic toxicity, namely neutropenia, somnolence, and occasional gastrointestinal complaints). Clinical trial: 2010-020759-30. The gene discussed is PGP; the disease is neutropenia.