(Adds analyst comment, shares) By Ludwig Burger and Dina Kartit March 13 (Reuters) - France's Sanofi SA on Monday agreed to acquire Provention Bio Inc for $2.9 billion to bolster its work on a U.S.-approved type 1 diabetes therapy and strengthen its drug pipeline following development setbacks. The deal builds on an existing co-promotion agreement between the two companies, and would give the French drugmaker full ownership of the drug, Tzield, Sanofi said, adding it expects to complete the acquisition in the second quarter of 2023.