A generic drug maker hoping to sell its own version of the popular cholesterol drug Zetia has succeeded in knocking out part of Schering-Plough Corp.’s patent protection on the medication.

U.S. District Judge Jose Linares in Newark, N.J., on Monday invalidated items of protection that were added when Schering obtained a reissued patent in 2002, ruling the patent should not have been reissued because Schering already had a valid and enforceable patent.