The invention provides a method of sustained delivery of a lactam, imide, amide, sulfonamide, carbamate or urea containing parent drug by administering to a patient an effective amount of a prodrug compound of the invention wherein upon administration to the patient, release of the parent drug from the prodrug is sustained release. Prodrug compounds suitable for use in the methods of the invention are labile conjugates of parent drugs that are derivatized through carbonyl linked prodrug moieties. The prodrug compounds of the invention can be used to treat any condition for which the lactam, imide, amide, sulfonamide, carbamate or urea containing parent drug is useful as a treatment.

This invention relates to a compound of formula I ##STR00001##
wherein A and Cy have one of the meanings as indicated in the specification and their use as inhibitors of Cathepsin C, pharmaceutical compositions containing the same and methods of using the same as agents for treatment and/or prevention of diseases connected with dipeptidyl peptidase I activity, e.g. respiratory diseases.