The present disclosure provides compounds of Formula (I-a), Formula (I), and Formula (II),. The compounds described herein may be Myc modulators (e.g., Myc inhibitors) and may be useful in treating in a subject in need thereof diseases associated with Myc and proliferative diseases (e.g., cancer). Also provided in the present disclosure are pharmaceutical compositions, kits, methods, and uses including a compound described herein. (Formulae (I-a), (I), (II))