The managed care consortium Kaiser Permanente is suing Merck (NYSE: MRK) over alleged pay-to-delay agreements to withhold the production of generic drugs for Zetia and Vytorin.

Zetia (ezetimibe) is a cholesterol absorption inhibitor while Vytorin combines ezetimibe with simvastatin, an inhibitor of 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase. FDA drugs treat high cholesterol levels.

The lawsuit also names Glenmark, a manufacturer of generics of Zetia and Vytorin. It alleges that Merck’s plan to delay the introduction of generics for those drugs had cost Kaiser hundreds of millions of dollars, according to a report from the San Francisco Business Times.

The Oakland, Calif.–headquartered Kaiser Foundation Health Plan first filed the suit in San Francisco Superior Court. That court, however, transferred the case to the U.S. District Court in San Francisco.

FDA first approved Zetia in October 2002.

FDA approved Vytorin in July 2004.

The company Glenmark claimed that the patent for Zetia was invalid in 2006, aiming with that “first-to-file” status to receive a 180-day window to be the exclusive manufacturer of the generic version of the drug. On Dec. 12, 2016, Glenmark announced it was the first and only manufacturer of a Zetia generic in the U.S.

Merck initially attempted to legally block Glenmark’s generic application, but the two manufacturers reached an agreement in May 2010 in which Glenmark agreed to cease manufacturing the drug until Dec. 12, 2016.

Glenmark received permission from FDA to manufacture various doses of a generic Vytorin in 2019.

Merck did not immediately respond to a request for comment.