French drugmaker Sanofi (SASY.PA) on Thursday posted better-than-expected earnings for the first quarter as continued gains from anti-inflammatory drug Dupixent more than offset declining sales from an established multiple sclerosis drug.

It reported an 8.7% rise in quarterly business operating income, or adjusted earnings before interest and tax, to 3.33 billion euros ($3.7 billion), ahead of an average analyst estimate of 3.14 billion posted on the company’s website.

Revenue from eczema and asthma drug Dupixent, jointly developed with Regeneron (REGN.O), surged more than 43% to 2.32 billion euros, above a consensus of 2.27 billion euros.

Quarterly sales of an older multiple sclerosis pill known as Aubagio dropped almost 17% to 419 million euros, after it was hit by cheap generic copies that came to U.S. markets in mid-March. In Europe, market exclusivity is expected to end in the fourth quarter.

The Paris-based drugmaker said on Thursday it still expected 2023 adjusted earnings per share to grow by a “low single digit” percentage, not taking into account an expected negative currency impact of between 5.5% and 6.5%.

It had previously flagged a negative currency impact of between 3.5% and 4.5%.

Dupixent was successfully tested last month to treat “smoker’s lung” or chronic obstructive pulmonary disease (COPD), potentially adding billions to the Sanofi’s growth prospects, but also underscoring a heavy reliance on the bestseller.

Finance chief Jean-Baptiste de Chatillon said in a media call that, for now, there would be no new annual peak sales estimate for the product, which Sanofi has put at more than 13 billion euros.

According to presentation slides, the details of the COPD study are scheduled to be published at a meeting of the American Thoracic Society in Washington DC on May 19-24.

Also last month, Sanofi struck a deal to acquire Provention Bio (PRVB.O) for $2.9 billion to bolster its work on an approved type 1 diabetes therapy and strengthen its drug pipeline following development setbacks. CFO de Chatillon said on Thursday the takeover was progressing as planned.