GlaxoSmithKline has entered into an agreement to acquire Sierra Oncology, a California-based, late-stage biopharmaceutical company focused on targeted therapies for rare forms of cancer, for an approximate total equity value of $1.9 billion.   GSK stands to gain Momelotinib, a treatment for Myelofibrosis. Momelotinib has a differentiated mode of action with inhibitory activity along key signaling pathways. This activity may lead to beneficial treatment effects on anemia and reduce the need for...