Macrocyclic proteasome inhibitors

Proteasome inhibitors have proven to be effective anticancer agents. Despite the success of the first on the market proteasome inhibitor bortezomib in chemotherapy, alternative clinically useful proteasome inhibitors are still urgently needed as bortezomib therapy causes severe side effects and is limited by arising drug resistance. Experience from previous proteasome inhibitor studies has thereby demonstrated that the identification of proteasome inhibitor structures with suitable pharmacological properties is a key factor for a successful development of clinically useful proteasome inhibitors. Macrocycles often show distinct and in comparison to linear small molecules superior pharmacological properties. Consequently, macrocyclic proteasome inhibitors might represent promising small molecules for drug development. Here, we want to highlight the current state of the art of macrocyclic proteasome inhibitor research. To this end, we give an overview and critically discuss currently known classes of macrocyclic proteasome inhibitors.