Bedaquiline Amplifies Proteasome Inhibitor Efficacy and Overcomes Resistance in Multiple Myeloma

Proteasome inhibitors (PIs) are cornerstone therapies for multiple myeloma (MM), yet resistance remains a major barrier to durable responses. To identify druggable vulnerabilities that enhance PIs efficacy, we performed a small-molecule chemical screen in the presence of carfilzomib (CFZ). We identified bedaquiline (BDQ), an FDA-approved antimycobacterial agent, as a potent synergistic partner. BDQ and its fumarate salt (BDQ-F) significantly amplified CFZ-induced cytotoxicity in PI-sensitive and PI-resistant MM cells, in AL amyloidosis and other B-cell malignancies, with minimal toxicity toward normal cells. Mechanistic studies confirmed that BDQ specifically targets the ATP5F1C subunit of mitochondrial ATP synthase. BDQ-CFZ combination triggered extensive apoptosis, exacerbating proteotoxic stress and proteasome-associated pathways. BDQ specifically enhanced CFZs inhibition of the proteasomes chymotrypsin-like activity. Importantly, BDQ synergized with multiple proteasome and ubiquitin-activating enzyme inhibitors, but not with other standard MM agents, underscoring its selective interaction with the UPS pathway. BDQ-CFZ co-treatment markedly reduced MM cell viability and tumor burden in patient-derived cells and zebrafish xenograft models. These findings support the therapeutic repurposing of BDQ to potentiate PIs efficacy and overcome resistance in MM and related B-cell malignancies. KEY POINTSO_LIBedaquiline synergizes with proteasome inhibitors in MM and other hematologic malignancies, sparing normal cells C_LIO_LIBedaquiline targets ATP synthase {gamma} and boosts carfilzomib by enhancing chymotrypsin-like proteasome inhibition C_LI NOVELTYWe identify the antimicrobial bedaquiline and its fumarate salt as potent enhancers of proteasome inhibitor efficacy in multiple myeloma and other B-cell malignancies. By inhibiting ATP synthase {gamma}, bedaquiline amplifies chymotrypsin-like proteasome inhibition and overcomes drug resistance. This study reveals a mitochondria- proteasome vulnerability and proposes a clinically actionable strategy to restore sensitivity and reduce toxicity of proteasome-based therapies. VISUAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=135 SRC="FIGDIR/small/661768v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@339391org.highwire.dtl.DTLVardef@1d3271org.highwire.dtl.DTLVardef@daa0faorg.highwire.dtl.DTLVardef@17eb4eb_HPS_FORMAT_FIGEXP M_FIG C_FIG