Share of Galapagos (GLPG), a Belgian biotechnology firm, surged early on Monday as the US drugmaker Gilead Sciences (GILD) said it signed a deal under which it will pay Galapagos $5.05 billion in return for an exclusive product license and option rights to develop and commercialize all current and future programs in all countries outside Europe.

The 10-year global research and development collaboration will allow Gilead, which focuses primarily on antiviral drugs used in the treatment of HIV, hepatitis B, hepatitis C, and influenza, to gain access to a portfolio of compounds, including six molecules currently in clinical trials, more than 20 preclinical programs and a proven drug discovery platform, according to a statement.

Of the aggregate amount pledged to the deal, $3.95 billion is payable upfront and the remaining $1.1 billion is in the form of equity investment into Galapagos shares at a price of 140.59 euros per share, representing a 20% premium to 30-day, volume-weighted average price.

Gilead and Galapagos have also agreed to amend certain terms of an agreement governing filgotinib, the candidate being advanced for rheumatoid arthritis, to provide a broader commercialization role for Galapagos in Europe.

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Both companies will co-commercialize filgotinib in France, Germany, Italy, Spain, and the UK and retain the 50/50 profit share in these countries that was part of the original filgotinib license agreement, and under the revised pact, Galapagos will have an “expanded commercial role.”

As part of the deal, the Foster City, Calif.-based Gilead said it would have access to Galapagos’ research base, which includes more than 500 scientists, and to its platform, which utilizes disease-related, human primary cell-based assays to discover and verify novel drug targets, enabling a closer scientific partnership between the companies.

“The collaboration reflects Gilead’s intent to grow our innovation network through diverse and creative partnerships,” Daniel O’Day, chief executive officer of Gilead, said in the statement. “Gilead gains exclusive access to all current and future compounds in Galapagos’ rich pipeline while Galapagos is able to expand its research activities and build commercial infrastructure.”