Discovery of a Miniaturized PROTAC with Potent Activity and High Selectivity

Background and Purpose The approved small-molecule inhibitors of anaplastic lymphoma kinase (ALK) have shown remarkable efficacy in some subset of cancer patients. However, the numerous ALK mutants or fusion partners are resistant to such drugs, greatly limiting their application in clinic. Despite the drug design strategy of proteolysis-targeting chimera (PROTAC) holds great potential to overcome drug resistance in theory, there are obvious disadvantages for the reported PROTACs that include high molecular weight, long linkers, difficult synthesis routes as well as insufficient evidence in activity for diverse ALK mutants. Experimental Approach In this study, we synthesized a miniaturized PROTAC of ALK named AP-1 following the principle of minimalist design. Two simple chemical units of ligands and a minimized linker with only two atoms were selected for synthesis of AP-1. Key Results At cellular level, AP-1 successfully degraded three types of ALK mutants including NPM-ALK, EML4-ALK and F1174L mutation ALK form with strong activity, high selectivity in ALK-positive cells. In tumor-bearing mouse models, AP-1 showed the stronger antitumor efficacy than controls as well as the similar compounds reported in literatures. Conclusion and Implications AP-1 with an extremely simple PROTAC structure can be served as an effective candidate drug for therapy of various types of ALK-positive cancers. And the design principle of AP-1 has a good guiding significance for overcoming the disadvantages such as excessive molecular weight and poor solubility of PROTAC.