April 25 (Reuters) - Sanofi's said on Thursday first-quarter operating income declined 14.7% as unfavourable currency effects and cheap competition to multiple sclerosis drug Aubagio outweighed rising sales of anti-inflammatory drug Dupixent.

The French drugmaker said in a statement that operating income, adjusted for one-offs, slipped 14.7% to 2.84 billion euros ($3.04 billion), a touch above the 2.79 billion euros expected on average by analysts in a poll on the company's website.

The company reiterated it expects 2024 adjusted earnings per share (EPS) to slip by a "low single-digit" percentage, excluding currency swings, citing higher taxes and an increase in development expenditure.

Currency changes would drag 2024 earnings lower by between 5.5% and 6.5% at current rates, it added. ($1 = 0.9338 euros) (Reporting by Ludwig Burger; Editing by Benoit Van Overstraeten)