(Reuters) - A federal judge in Delaware on Tuesday invalidated patents held by Mallinckrodt Pharmaceuticals on its Inomax respiratory treatment system.

The ruling came in a lawsuit brought by Mallinckrodt against the industrial gases company Praxair Inc, which sought to market a generic version of Inomax. The judge found Praxair did not infringe Mallinckrodt’s patents.

Mallinckrodt said it was disappointed in the ruling and would appeal.

Shares of Mallinckrodt fell around 13 percent after the decision.

Praxair did not immediately respond to a request for comment.

Mallinckrodt noted it had regulatory exclusivity for the treatment until October 2018.

Mallinckrodt shares have been targeted by short sellers, with 18.6 percent of the shares outstanding held as short interest as of Aug. 14, according to Thomson Reuters data.