A 10-employee Norwood biotech has received the first of what it expects will be three orphan drug designations from the Food and Drug Administration for a drug it bought last year from a professor at UMass Medical Center in Worcester. Corbus Pharmaceuticals , which just started trading on the Nasdaq exchange in April, has been known among investors mostly for its plan to develop the drug to treat inflammation associated with cystic fibrosis which could potentially be used in conjunction with the suite of drugs being produced at Boston-based Vertex Pharmaceuticals .