(Reuters) -Biogen forecast 2025 profit below last year's levels and Wall Street expectations on Wednesday, hurt by a strong dollar and fierce competition for its drugs to treat multiple sclerosis.

Its shares fell 3.7% in premarket trading after losing more than 40% of their value last year. The company had a market capitalization of about $20 billion as of its last closing price.

Investors fled the company's stock in 2024 as a slow US launch of Leqembi, the Alzheimer's disease drug it sells with Japan's Eisai, exacerbated worries of declining sales of its multiple sclerosis drugs.

The company in 2022 hired as its top boss former Sanofi CEO Christopher Viehbacher, who launched a $1 billion cost-savings plan and entered deals such as its $6.5 billion acquisition of Reata Pharmaceuticals in 2023.

Biogen expects 2025 revenue to decline by a mid-single digit percentage, excluding the impact of currency fluctuations, from 2024 levels.

"Our financial discipline has enabled a restructuring of our operating expenses with a reallocation of resources toward potential future growth drivers," CEO Viehbacher said.

On an adjusted basis, Biogen expects 2025 profit between $15.25 and $16.25 per share. It earned $16.47 in 2024 and analysts had forecast 2025 profit of $16.34 per share.

The company, however, beat profit expectations for the fourth quarter, benefiting from a better-than-expected demand for its spinal muscular atrophy drug, Spinraza.

Excluding certain items, Biogen earned $3.44 per share in the fourth quarter ended December 31, compared with estimates of $3.35.

Total revenue rose about 3% to $2.46 billion. Analysts had expected fourth-quarter sales of $2.41 billion. Overall sales of its multiple sclerosis drugs, which includes treatments such as Tecfidera and Tysabri, fell 8% to $1.07 billion.

(Reporting by Manas Mishra in Bengaluru; Editing by Arun Koyyur)