Dec 4 (Reuters) - Novartis failed to convince a

U.S. appeals court on Wednesday to halt MSN Pharmaceuticals'

proposed generic of Novartis' blockbuster heart drug Entresto.

The U.S. Court of Appeals for the Federal Circuit upheld a

Delaware federal judge's August decision that found Novartis

failed to prove it was likely to win a patent lawsuit against

MSN over the drug, removing a roadblock for MSN's launch of what

would be the first U.S. Entresto generic.

Spokespeople and attorneys for the companies did not

immediately respond to requests for comment.

Entresto is Switzerland-based Novartis' best-selling drug,

bringing the company more than $6 billion in revenue last year.

MSN's version of Entresto was approved by the U.S. Food and Drug

Administration in July.

Novartis sued MSN and others seeking to launch Entresto

generics in Delaware federal court in 2022 for allegedly

infringing a patent that expires in 2026. It requested a

preliminary injunction after the FDA's approval that would block

MSN from launching its generic during the case, which is set to

go to trial on Monday.

U.S. District Judge Richard Andrews rejected Novartis'

request in August, ruling that it was not sufficiently likely to

win on its infringement claims to justify the injunction. The

judge paused MSN's launch of its proposed generic while Novartis

appealed to the Federal Circuit.

The Washington-based appeals court affirmed Andrews'

decision on Wednesday and said it saw "no clear error in the

district court's analysis."