[Development and clinical success of novel soft drugs]

Retrometabolic drug design combines the structure-activity and structure-metabolism relationships, allowing the effective separation of drug action and side effects. This combination results in significant improvement of the therapeutic index. The main aim is not only to study the metabolism but to build into the drug molecule the desired metabolic route, in addition to the therapeutic activity. There are two basically different approaches to achieve this aim. Both use designed-in metabolism. The 1. chemical drug-targeting systems (CDS) and 2. soft drug, both control the drug targeting and action by strategically designed metabolism. In the case of the soft drugs, we want to rely on hydrolytic enzymes, avoiding the oxidative processes. In the present work, we focus on the clinical successes of the soft drugs designed in our laboratories. In order to show the difference, we briefly present a brain-targeted delivery system, where the originally inactive molecular construct undergoes sequential metabolism to allow specific concentration of the active drug in the brain. Among the soft drugs first we present the highly successful soft corticosteroids. Loteprednol etabonate has been used worldwide for over twenty years, and its use is constantly growing. In addition to the dramatically improved therapeutic index, the specific, serious ophthalmic side effects (elevation of intraocular pressure; glaucoma and cataract formation) were completely eliminated. Similarly designed second generation of soft corticosteroids are also presented, where the soft pharmacophore is structurally unexpected. The most recent soft drug design involves anticholinergics. Sofpironium bromide, a highly effective molecule but without the typical anticholinergic side effects, was first developed to treat hyperhidrosis, an unmet need. Phase III clinical studies were successfully completed and its marketing approval is pending. Since the soft drug design principles, methods and rules are general and specific in nature, a computerized expert system was also developed. Orv Hetil. 2020; 161(10): 363-373.