HIF1A and neoplasm: Likewise, acriflavine, an antibacterial drug that was clinically used before penicillin, was noticed to directly bind to the HIF-1α and HIF-2α PAS-B subdomain and prevents them from interacting with HIF-1β, preventing the transcription of genes controlled by HIF and impairing the development and vascularization of the tumor [99,100,101].