Xuanbi Xiaoliu formula alleviates bone destruction by targeting the CREBBP/c-Myc axis with saponarin in multiple myeloma.

BACKGROUND: Multiple myeloma (MM)-associated bone disease (MBD) is a devastating complication characterized by osteolytic lesions and poor survival. Xuanbi Xiaoliu Formula (XBXLF), an herbal formula for MM, has demonstrated promising therapeutic effects; however, its mechanism of action remains unclear. This study aimed to elucidate the pharmacological actions of XBXLF against MM, with a specific focus on its effects on MBD. METHODS: We employed an integrated approach combining a clinical trial, in vitro and in vivo models, serum pharmacochemistry, UPLC-MS/MS-based metabolomics, single-cell RNA sequencing, and molecular docking/CETSA assays. Functional experiments were performed using KMS28PE/CAG cell lines and RAW264.7 osteoclastogenesis models treated with XBXLF-containing serum or its identified components to investigate the underlying mechanisms. RESULTS: In MM patients with MBD, XBXLF add-on therapy significantly improved survival and quality of life, while reducing adverse events and bone pain markers. In murine models, XBXLF inhibited bone loss and osteoclastogenesis and promoted osteoblast activity. Mechanistically, serum containing XBXLF metabolites dose-dependently suppressed MM cell proliferation and osteoclast formation. RNA-seq analysis identified downregulation of CREBBP as a key event. Saponarin and 3-Hydroxycinnamic acid were identified as the major circulating bioactive components following XBXLF administration. Importantly, Saponarin directly bound to CREBBP and downregulated c-Myc, thereby inhibiting both MM cell proliferation and osteoclast differentiation. CONCLUSION: This study demonstrates that XBXLF improves clinical outcomes in MBD by modulating the CREBBP/c-Myc pathway through its active component Saponarin. These findings reveal a novel therapeutic strategy for MBD and provide a scientific basis for integrating XBXLF into combined treatment regimens for MM.