The invention provides novel compositions of bioactive polypeptides and proteins with improved stability and shelf-life. The compositions are based on liquid vehicles selected from semifluorinated alkanes. These vehicles are remarkably effective in protecting polypeptides and proteins from degradation and/or aggregation. The compositions are useful for topical administration, e.g. into an eye, or by parenteral injection, e.g. via the subcutaneous or intramuscular route.