May 14 (Reuters) - GSK will buy efimosfermin, a

liver disease drug in late-stage trials, for up to $2 billion

from U.S. biotechnology firm Boston Pharmaceuticals, the British

drugmaker said on Wednesday.

Efimosfermin, a monthly subcutaneous injection, is a phase

III ready medicine expected to be launched in 2029 to treat

steatotic liver disease (SLD). It is also currently in clinical

development for the treatment of MASH, a form of liver disease,

characterised by inflammation and damage caused by build up of

fat.

GSK will pay up to $2 billion cash, comprising an upfront

payment of $1.2 billion and up to $800 million in success-based

milestone payments.

Under the terms of the agreement, GSK will buy BP Asset IX,

Inc., a subsidiary of Boston Pharmaceuticals, to access

efimosfermin.

GSK is further planning to develop the drug for potential

treatment of alcohol-related liver disease (ALD).

SLD affects about 5% of the global population, ALD affects

about 26 million patients around the world.

GSK has been actively advancing therapies for liver disease.

In a presentation in December 2024, it had said GSK'990, an

experimental drug in phase I trials had shown it can reduce

markers indicating liver damage, suggesting potential to slow or

halt disease progression.

GSK said on Wednesday it will also pay milestone

payments and tiered royalties to Novartis Pharma for

efimosfermin, without giving details.