The disclosure relates to aryl hydrocarbon receptor antagonists, such as substituted imidazopyridines and imidazopyrazines, as well as methods of expanding hematopoietic stem cells by culturing hematopoietic stem or progenitor cells in the presence of these agents. Additionally, the disclosure provides methods of treating various pathologies in a patient by administration of expanded hematopoietic stem cells. The disclosure further provides methods of synthesizing aryl hydrocarbon receptor antagonists, such as substituted imidazopyridines and imidazopyrazines, as well as kits containing aryl hydrocarbon receptor antagonists that can be used for the expansion of hematopoietic stem cells.
