Health care stocks declined Thursday afternoon, with the NYSE Health Care Index shedding 0.9% and the State Street Health Care Select Sector SPDR ETF (XLV) decreasing 0.6%.

The iShares Biotechnology ETF (IBB) dropped 0.8%.

In corporate news, Sanofi (SNY) and Disc Medicine (IRON) saw reviews for their type 1 diabetes and rare blood disorder drugs postponed after US Food and Drug Administration reviewers flagged safety and efficacy concerns, Reuters reported Thursday, citing internal documents. Reviews on two other drugs in the program, Boehringer Ingelheim's lung cancer therapy and Eli Lilly's (LLY) weight-loss pill, have also been delayed, with decisions now expected in mid-February and on April 10, respectively, Reuters reported. Lilly, Disc, and Sanofi shares fell 3.8%, 7%, and 1% respectively.

Boston Scientific (BSX) on Thursday agreed to buy medical device company Penumbra (PEN) in a cash-and-stock deal with an enterprise value of about $14.5 billion, as it aims to strengthen its cardiovascular portfolio. Boston Scientific shares were down 3.7%, and Penumbra jumped past 12%.

Emergent BioSolutions (EBS) former CEO Robert Kramer was sued by New York Attorney General Letitia James for alleged insider trading, according to a statement from the Attorney General's office. Emergent BioSolutions shares were down 9.5%.