The new cancer drug MPDL3280A has produced promising results in an early clinical trial that investigated patients with various advanced cancers including lung cancer; melanoma; and cancer of the kidney, intestines, or stomach. All participants had previously seen their cancer worsen despite treatment. Yet, during treatment with MPDL3280A, tumors shrank significantly in more than one-fifth of the patients. Response rates were especially high in lung cancer and melanoma patients. Of the patients who responded to MPDL3280A, almost all continue to see effects now, 3 to 15+ months into the study. MPDL3280A targets a protein, PD-L1, that is often expressed on cancer cells and 'hides' the cells from the body's immune response; by blocking PD-L1, MPDL3280A allows the immune system to attack the tumors. Further studies will be needed to confirm these findings.