Using Keytruda (pembrolizumab) in combination with chemotherapy increased the percentage of patients showing no signs of breast cancer after completing a course of neoadjuvant therapy — treatment to shrink a tumor — and  surgery, interim analysis of a Phase 3 trial shows. This marks the first time this type of therapy plus chemotherapy has demonstrated a statistically significant improvement in treating triple-negative breast cancer, the researchers said. Keytruda is a checkpoint blockade immunotherapy developed by Merck (known as MSD outside the U.S. and Canada), which has been approved by the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for treating several types of cancer. It is a monoclonal antibody that has been designed to target and block the activity of the PD-1 receptor — a protein found on the surface of