03:40 AM EST, 03/06/2025 (MT Newswires) -- (Updates to add the companies' comments in the fifth and sixth paragraphs)

Merck ( MRK ) is facing a patent dispute that threatens its plans to sell a new version of Keytruda, its top-selling cancer drug, the Wall Street Journal reported Wednesday.

The report said the new version, which allows for injection instead of intravenous use, is at the center of the conflict with Halozyme Therapeutics ( HALO ) , which claims Merck ( MRK ) infringes on its patents for the enzyme Mdase.

Merck ( MRK ) has petitioned US patent regulators to reconsider the patents, arguing they are too broad, according to the Wall Street Journal report.

Halozyme insists Merck ( MRK ) must sign a licensing agreement to sell the new version, the sources told the Journal. While Merck ( MRK ) maintains it developed the enzyme independently.

A Merck ( MRK ) spokesman told MT Newswires that "the ALT-B4 hyaluronidase variant was independently developed by Alteogen scientists", adding "Halozyme did not invent ALT-B4."

"It is our preference to sign a license agreement with any company using our Intellectual property to deliver drugs subcutaneously with a modified human hyaluronidase," Tram Bui, Halozyme's spokesperson said.

Merck ( MRK ) has been working to modify Keytruda to make it easier to use and protect future revenue as its US patent protection expires in 2028, allowing competitors to sell copycat versions.

(Market Chatter news is derived from conversations with market professionals globally. This information is believed to be from reliable sources but may include rumor and speculation. Accuracy is not guaranteed.)