Targeting the Liquid-Liquid Separation Region of c-Maf for Treating Chromosomal Translocations in Multiple Myeloma

Multiple myeloma (MM), as an incurable hematologic malignancy, is driven by chromosomal translocations. Recent research suggests that targeting phase separation may offer a new therapeutic vulnerability for MM. The transcription factor c-Maf is implicated in MM-associated translocations and undergoes liquid-liquid phase separation (LLPS). Although c-Maf is historically classified as "undruggable" for its transcription factor nature, we propose a new therapeutic strategy targeting its phase separation mechanism. Comprehensive in vitro and in vivo experiments indicated that elevated c-Maf promoted MM progression through LLPS. Mechanistically, the alanine-rich intrinsically disordered regions (IDRs) in c-Maf drive hydrophobic interactions, enabling phase separation. These IDRs recruit RNA Polymerase II (RNA Pol II) through similar interactions, forming oncogenic condensates that activate the Mtbp/c-Myc axis. Notably, we discovered benzoyl benzoic acid (BBA) as a candidate compound targeting the inter-IDR interaction domain of c-Maf. BBA binding impedes c-Maf's LLPS capacity, consequently blocking RNA Pol II recruitment and Mtbp transcriptional activation. This mechanistic interference successfully inhibited c-Myc-driven MM progression in experimental models. Our study demonstrates that c-Maf-driven LLPS activates the c-Maf/RNA Pol II/Mtbp/c-Myc axis, highlighting phase separation targeting as a promising therapeutic strategy for translocation-associated MM patients.