Following disappointing phase 3 results in multiple sclerosis and the negative impact related to new pediatric vaccination schedules in the United States, the research firm said it had revised its medium-term earnings estimates for the company down by around 8%, leading it to downgrade its rating to "neutral" from "buy" previously.

Its price target was also reduced to 88 euros, down from 105 euros.

Although the short-term valuation remains attractive for the pharmaceutical sector, UBS believes that Sanofi's inability to invigorate its portfolio of new projects constitutes too great a strategic risk.

Significant merger and acquisition operations could be the only realistic solution, according to the analyst, who nevertheless considers that this prospect remains associated with a certain degree of uncertainty and significant risks, while also limiting the possibility of share buybacks to support EPS growth.

Sanofi shares were trending lower on Friday on the Paris Stock Exchange in reaction to the Swiss bank's decision, losing 0.7% by midday, while the CAC 40 was down 0.5%.

The stock, which has struggled for almost a year, has lost 17% of its value over the past 12 months.