Feb 11 (Reuters) - Swiss pharmaceutical giant Novartis

has agreed to acquire Anthos Therapeutics, a biopharma

firm majority-owned by Blackstone's drug development

unit, for up to $3.1 billion, to boost its cardiovascular

business.

Anthos was founded by private equity firm Blackstone's Life

Sciences business and by Novartis in 2019 to develop,

manufacture, and commercialise abelacimab, a treatment to

prevent strokes and the recurrence of blood clots.

The deal underlines the Swiss group's commitment to

cardiovascular therapies, one of five medical areas that it is

focusing on, as its best-selling heart failure drug Entresto

loses patent protection this year.

The transaction, expected to close in the first half of

this year, also concludes a high-profile development partnership

between a drug major and a private equity firm, an emerging

funding model that has been explored by the industry.

Novartis will pay $925 million upfront with additional

payments of up to $2.15 billion, contingent on development

achievements, the companies said in statements.

A Blackstone spokesperson said the deal was the largest

sale to date of a majority-owned Blackstone Life Sciences

company.

Reuters reported in December 2023 that Blackstone was

exploring the sale of Anthos.

Abelacimab belongs to a novel class of drugs known as factor

XI inhibitors, designed to replace established blood thinners

Eliquis by Bristol Myers-Squibb ( BMY ) and Pfizer ( PFE ) as

well as Xarelto by Johnson & Johnson ( JNJ ) and Bayer

, which are billion dollar sellers.

Bristol-Myers Squibb ( BMY ), together with Johnson & Johnson ( JNJ ),

are working in late stages of clinical testing on drug candidate

milvexian.

Merck & Co ( MRK ) is also in the factor XI race with a

mid-stage development candidate. Germany's Bayer in 2023

suffered a huge

setback

in its effort to advance its factor XI drug.

Nicholas Galakatos, chairman of Anthos' board of

directors and global head of Blackstone Life Sciences, said the

firm was proud to have launched and helped grow Anthos.

"We believe abelacimab has the potential to be a leader

in the new class of Factor XI anticoagulants and are pleased to

have Novartis as a committed partner to advance the development

and commercialization of abelacimab as a potential treatment ...

for the millions of patients at risk of strokes," he said.

Anthos is conducting several phase 3 clinical studies, with

data from these trials expected in the second half of 2026,

Blackstone said.

Novartis said it already holds a small minority equity

interest in Anthos, but declined to detail the size of it.