ID1 and neoplasm: To better address Omomyc selectivity we investigated its capacity to bind N-Myc – which shares substantial functional redundancy with c-Myc and has important roles in tumor formation in the nervous system –, Mad – a strictly related bHLHZip factor that dimerizes with Max, binds E-boxes and acts as transcriptional repressor [4] –, Heb and Id1 – two HLH proteins representative of a large family of transcriptional regulators implicated in developmental processes [19].