To determine whether pharmacological BCL-XL inhibition combined with osimertinib treatment blocks drug resistance in EGFR-mutated lung cancer, we treated H1975 or PC9-ER cells 7 days with either osimertinib alone or with a combination of osimertinib plus a BCL-XL inhibitor (either ABT-263 or A1331852). The gene discussed is EGFR; the disease is lung cancer.