The current study presented that I-BET151 could dose-dependently inhibited the ratio of multinucleated TRACP positive cells and osteoclast differentiation, the expression of osteoclast-specific genes including TRACP, MMP-9, Ctsk, and C-Src, and the secretion of inflammatory cytokines including TNF-α, IL-1β, and IL-6 in peripheral blood from both healthy donors and patients with MM induced by RANKL and M-CSF. The gene discussed is CTSK; the disease is Miyoshi myopathy.