Proton pump inhibitors selectively suppress MLL rearranged leukemia cells via disrupting MLL1-WDR5 protein-protein interaction.

Genetic rearrangements of the mixed lineage leukemia (MLL) leading to oncogenic MLL-fusion proteins (MLL-FPs). MLL-FPs occur in about 10% of acute leukemias and are associated with dismal prognosis and treatment outcomes which emphasized the need for new therapeutic strategies. In present study, by a cell-based screening in-house compound collection, we disclosed that Rabeprazole specially inhibited the proliferation of leukemia cells harboring MLL-FPs with little toxicity to non-MLL cells. Mechanism study showed Rabeprazole down-regulated the transcription of MLL-FPs related Hox and Meis1 genes and effectively inhibited MLL1 H3K4 methyltransferase (HMT) activity in MV4-11 cells bearing MLL-AF4 fusion protein. Displacement of MLL1 probe from WDR5 protein suggested that Rabeprazole may inhibit MLL1 HMT activity through disturbing MLL1-WDR5 protein-protein interaction. Moreover, other proton pump inhibitors (PPIs) also indicated the inhibition activity of MLL1-WDR5. Preliminary SARs showed the structural characteristics of PPIs were also essential for the activities of MLL1-WDR5 inhibition. Our results indicated the drug reposition of PPIs for MLL-rearranged leukemias and provided new insight for further optimization of targeting MLL1 methyltransferase activity, the MLL1-WDR5 interaction or WDR5.

Repurposing of Proton Pump Inhibitors as first identified small molecule inhibitors of endo-ß-N-acetylglucosaminidase (ENGase) for the treatment of NGLY1 deficiency, a rare genetic disease.

N-Glycanase deficiency, or NGLY1 deficiency, is an extremely rare human genetic disease. N-Glycanase, encoded by the gene NGLY1, is an important enzyme involved in protein deglycosylation of misfolded proteins. Deglycosylation of misfolded proteins precedes the endoplasmic reticulum (ER)-associated degradation (ERAD) process. NGLY1 patients produce little or no N-glycanase (Ngly1), and the symptoms include global developmental delay, frequent seizures, complex hyperkinetic movement disorder, difficulty in swallowing/aspiration, liver dysfunction, and a lack of tears. Unfortunately, there has not been any therapeutic option available for this rare disease so far. Recently, a proposed molecular mechanism for NGLY1 deficiency suggested that endo-ß-N-acetylglucosaminidase (ENGase) inhibitors may be promising therapeutics for NGLY1 patients. Herein, we performed structure-based virtual screening utilizing FDA-approved drug database on this ENGase target to enable repurposing of existing drugs. Several Proton Pump Inhibitors (PPIs), a series of substituted 1H-benzo [d] imidazole, and 1H-imidazo [4,5-b] pyridines, among other scaffolds, have been identified as potent ENGase inhibitors. An electrophoretic mobility shift assay was employed to assess the inhibition of ENGase activity by these PPIs. Our efforts led to the discovery of Rabeprazole Sodium as the most promising hit with an IC50 of 4.47±0.44µM. This is the first report that describes the discovery of small molecule ENGase inhibitors, which can potentially be used for the treatment of human NGLY1 deficiency.

Identification of proton-pump inhibitor drugs that inhibit Trichomonas vaginalis uridine nucleoside ribohydrolase.

Trichomonas vaginalis continues to be a major health problem with drug-resistant strains increasing in prevalence. Novel antitrichomonal agents that are mechanistically distinct from current therapies are needed. The NIH Clinical Compound Collection was screened to find inhibitors of the uridine ribohydrolase enzyme required by the parasite to scavenge uracil for its growth. The proton-pump inhibitors omeprazole, pantoprazole, and rabeprazole were identified as inhibitors of this enzyme, with IC50 values ranging from 0.3 to 14.5 µM. This suggests a molecular mechanism for the in vitro antitrichomonal activity of these proton-pump inhibitors, and may provide important insights toward structure-based drug design.