An agreement has been made by Impac Laoratories Inc to pay $35 million. The payment will be part of a resolution of litigation over claims it entered into an anticompetitive deal in a patent case to delay releasing a generic version of the acne medication Solodyn.

The settlement information was disclosed in papers that were filed in Boston Federal Court late last week. The settlement only resolved part of the antitrust litigation Impax faces over Solodyn related to sales of the drug to direct purchasers such as retailers and wholesalers. The remaining claims – from a class of consumers and third-party insurers and cases by individual retailers like CVS Health Corp and Rite Aid Corp – began this week and opening statements have been made by both sides. Total costs for the case could reach over a billion dollars.

The case is In re Solodyn (Minocycline Hydrochloride) Antitrust Litigation, U.S. District Court, District of Massachusetts, No. 14-md-02503 and is among several filed in recent years targeting“pay-for-delay” settlements, in which brand-name drugmakers resolve patent lawsuits by paying generic companies to keep their products off the market for a longer period.