Navitoclax, as a single agent, has demonstrated limited outcomes in clinical trials on particular cancer types, namely acute lymphocytic leukemia (ALL) and advanced small cell lung cancer (SCLC), probably due to different expression levels of the BCL-2 family proteins, being thrombocytopenia and neutropenia the most adverse events [48,49]. The gene discussed is BCL2; the disease is small cell lung carcinoma.