CHICAGO (Reuters) – An experimental Bristol-Myers Squibb drug helped shrink tumors in patients with advanced melanoma, kidney and lung cancers in a preliminary trial, raising hopes for yet another drug that can wake up the immune system and train it to attack cancer cells. Early-stage tests of the drug BMS-936558, known as an anti-PD-1 treatment, showed it was relatively safe and shrank tumors in three of the five cancer types studied, the team reported at the American Society of Clinical Oncology (ASCO) meeting on Saturday and published online in the New England Journal of Medicine. …