Darunavir analog precursors target mitochondrial metabolism in multiple myeloma and CLL.

BACKGROUND: Multiple myeloma (MM) and chronic lymphocytic leukemia (CLL) are hematological malignancies with poor prognosis due to drug resistance, with no effective therapies. Drug resistance occurs from alterations in microenvironment and metabolism. Impaired mitochondrial metabolism underlies drug resistance in MM and CLL, and drugs targeting mitochondrial respiration show cytotoxicity and increase chemotherapy sensitivity. HIV protease inhibitors like nelfinavir show antitumor activity and resensitize drug-resistant cells to bortezomib and venetoclax. We evaluated effects of two HIV protease inhibitor precursors, BupM-NH2 and BnpM-NH2, on MM and CLL cells and their mechanism. METHODS: The cytotoxicity of the compounds was evaluated in MM (MM1S and RPMI-8226) and CLL (HG3) cell lines, peripheral blood mononuclear cells (PBMCs) and in patient-derived MM cells using MTS assays. Apoptosis was assessed by Annexin V staining and cell cycle analysis using flow cytometry. Western blotting was employed to assess protein expression to investigate the effects of the tested compounds on autophagy, endoplasmic reticulum stress, and respiratory chain function. Cellular metabolic activity was measured using Seahorse analyzer, whereas mitochondrial function and ROS generation were quantified via flow cytometry with MitoSOX and MitoTracker staining. RESULTS: BupM-NH2 and BnpM-NH2 at 50 µM decreased MM and CLL cell viability by 60% and 90%, while reducing PBMC viability by 40% and 50%. These compounds inhibited autophagy and mitochondrial respiration, reducing ATP production by 70% in MM, 30-60% in CLL, and 50% in PBMCs. BnpM-NH2 decreased the viability of cells from newly diagnosed multiple myeloma (NDMM) patients by 60% but showed a non-significant 15% reduction in relapsed/refractory multiple myeloma (RRMM) patients, whereas BupM-NH2 had no significant impact. Both compounds induced stress in respiratory chain and mitochondria that may help resensitize drug-resistant MM and CLL. CONCLUSIONS: BupM-NH2, and particularly BnpM-NH2, showed enhanced cytotoxicity against MM, CLL, and NDMM cells compared to PBMCs by inducing apoptosis through autophagy and mitochondrial respiration inhibition. While the cytotoxic effect in RRMM is less pronounced and nonsignificant, BupM-NH2 and BnpM-NH2 induces stress in respiratory chain and mitochondria, which may re-sensitize resistant tumor cells to treatments. Therefore these compounds may hold promise as novel therapeutic agents for MM and CLL treatment.