BioMarin Pharmaceutical Inc. (BMRN) agreed to acquire Amicus Therapeutics Inc. (FOLD) for about $4.8 billion in cash. The deal expands BioMarin’s portfolio of treatments for rare diseases.

Amicus shareholders will receive $14.50 per share. The price represents a 33% premium to the prior closing price. The companies said the transaction is expected to close in the second quarter of 2026.

The deal is subject to shareholder approval and regulatory clearance. Both companies announced the agreement in a statement released Friday.

Amicus shares surged 31% in New York trading shortly after the market opened. It marked the company’s largest one-day gain in more than a decade. The stock had already risen nearly 16% for the year through Thursday’s close.

BioMarin shares climbed 15% in early trading. The move was the biggest gain for the company since November 2016.

BioMarin Chief Executive Officer Alexander Hardy said the acquisition fits with the company’s existing commercial reach and manufacturing capabilities. Both companies focus on lysosomal storage disorders, a group of rare diseases that impair the body’s ability to break down waste materials in cells.

The transaction gives BioMarin access to approved treatments for Fabry disease and Pompe disease. Those drugs could generate $1.4 billion in combined sales by 2030.

The added products could reduce BioMarin’s reliance on Voxzogo. That drug is the company’s top-selling treatment and is used for achondroplasia, a form of dwarfism.

BioMarin has been seeking acquisitions to grow its rare disease business. Earlier this year, it bought Inozyme Pharma Inc. for about $270 million. That deal added a late-stage treatment for a condition affecting blood vessels, soft tissues, and bones.

Amicus reported more than $500 million in sales in 2024. Analysts said the acquisition strengthens BioMarin’s revenue outlook.

In a note, a Cantor Fitzgerald analyst said the deal immediately adds to BioMarin’s top-line growth. The company has faced pressure from investors to improve revenue momentum.

BioMarin received U.S. approval in 2023 for its gene therapy Roctavian to treat hemophilia. The company later said the therapy failed to gain traction and that it is seeking to divest the asset.

Morgan Stanley and J.P. Morgan are advising BioMarin. Centerview Partners and Goldman Sachs are advising Amicus.