AgamOBP1-Directed Discovery of Repellents to Control the Spread of Mosquito-Borne Diseases

Toward the discovery of novel efficient repellents, protein-directed dynamic combinatorial chemistry (pdDCC) coupled to saturation-transfer difference (STD) NMR spectroscopy was initially employed to identify modulators of the malaria vector Anopheles gambiae Odorant Binding Protein 1 (AgamOBP1). A library of potential binders of AgamOBP1 (secondary amines) generated from two amines and seven aldehydes was designed aiming to enable interactions with critical amino acids at the DEET-site and to bridge the DEET- and Icaridin sIC-binding pockets, both implicated in repellents recognition. Solubility issues hindered the clear identification of binders among the DCL members, except for one sublibrary, leading us to shift our strategy towards the synthesis of the designed amines, followed by direct evaluation of their binding to AgamOBP1 using ¹H STD NMR spectroscopy. The identified binders were further validated in vitro by fluorescence competition assays, and the most potent compounds which also possessed suitable vapor pressure were evaluated as repellents in arm-in-cage behavioral assays against Aedes albopictus. Amines 2A, 3A, 4A, and 6A showed significant repellent activity. The most potent was compound 4A (4-methyl-N-(pyridin-4-ylmethyl)aniline) which acted as a a DEET-like repellent at 0.4 μL cm^{- 2} dose. Thus, our strategy showcased a promising scaffold for further optimization toward efficient mosquito repellents.