China seen as the next big growth area for biotechs Biogen and Amgen

SunTrust initiated coverage on Biogen and Amgen on Tuesday, rating each stock as a buy based on solid drug pipelines and growth opportunities in China.

SunTrust's bullish thesis on Biogen is based on the company's Alzheimer's drug aducanumab. In October the company said it was once again seeking regulatory approval for the drug, which would be the first of its kind in the billion-dollar Alzheimer's market.

SunTrust also points to Biogen's strength in biosimilars, which are generic versions of biologic medicines used to treat illnesses like cancer and autoimmune diseases, as well as growth opportunities in China.