Jan 30 - French drugmaker Sanofi reported a fourth-quarter profit that came in-line with analysts' estimates on Thursday, and said it would buy back 5 billion euros ($5.21 billion) in shares this year as it seeks to build investor confidence in its drug pipeline.

Sanofi, one of the world's largest maker of vaccines and a leader in anti-inflammatory drugs, also said it expects sales to grow by a mid-to-high single-digit percentage in 2025, at a time the company transitions into a pure-play drugmaker.

Sanofi is close to selling a 50% stake in its consumer health business Opella to investor Clayton Dubilier & Rice, and said it expects the deal to close in the second quarter at the earliest.

Quarterly business operating income, excluding one-off items, fell by 7.7% to 2.08 billion euros but met the average analyst estimate in a poll posted on the company's website.

Sales of its blockbuster asthma drug Dupixent rose 16% to 3.46 billion euros, compared to 3.61 billion euros expected on average by analysts in a company-provided poll. The company said sales growth had been hit by fewer business days in the quarter compared to prior periods.

Investor expectations have been high for the anti-inflammatory drug, on which Sanofi partners with Regeneron REGN.O, after it gained approval for a common lung condition called chronic obstructive pulmonary disease in September.

Sales of Beyfortus, a new treatment to protect newborns from a common respiratory virus, more than doubled to 841 million euros, beating estimates of 648 million euros.

Vaccines sales rose a currency-adjusted 10.8% to 2.18 billion euros in the quarter, ahead of a 1.91 billion euro analyst consensus.

($1 = 0.9602 euros)