Drug Repurposing Screening for Rare and Neglected Diseases

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In collaboration with NIH and external academic researchers, we have performed drug repurposing screens for multiple projects across a range of therapeutic areas, including rare genetic disorders, rare and drug resistant cancer, and bacterial and viral infectious diseases. DRUG RESISTANT CANCER: Cancer drug resistance is a severe clinical problem that often results in patient death. We performed drug repurposing screens for drug-resistant cell lines of ovarian cancer refractory to multiple standard care chemotherapies. Several approved drugs have been identified that either suppress the drug-resistant cancer cells directly or re-sensitize the resistant cells to the anticancer activities of the standard drugs. We also found that diverse mechanisms are involved in cancer drug resistance, indicating the importance of personalized treatment which can be obtained from personalized drug screens using patient-derived cancer samples. We evaluated the combination therapy of the HIF-1a inhibitor (YC-1) with ERK (inhibitor selumetinib), and TGF-b1 inhibitor (SB431542) with a platinum drug. We found a novel TGF-b1/ERK/PHD2-mediated pathway that regulates the HIF-1a stability in platinum-resistant ovarian cancer. Both YC-1 and selumetinib reversed the drug platinum drug resistance in these ovarian cancer cells. Therefore, inhibition of TGF-b1, ERK or HIF-1a has a potential for further development for treatment of platinum-resistant ovarian cancer patients (Li Z. et al. 2019. Clin Cancer Res. 25:5947-60). We also carried out drug repurposing screens against drug resistant cell lines of colon cancer and studied the mechanism of drug resistance to the TNF-related apoptosis-inducing ligand (TRAIL). We found that 17-hydroxy wortmannin (17-HW) reversed resistance to TRAIL in the TRAIL resistant colon cancer cells. We further identified that the PIK3C3-beclin 1 (BECN1) and autophagy were increased in the TRAIL resistant cancer cells resulting in a reduction of caspase-8 protein in these cells. 17-HW, a PIK3C3-beclin 1 (BECN1) inhibitor, restored caspase 8 activity and re-sensitized these cancer cells to the TRAIL therapy. The results indicated a promising therapeutic approach for drug development to treat colon cancer using a combination therapy of TRAIL and PIK3C3-beclin 1 (BECN1) inhibitor (Dai S. et al. 2019. Mol Cancer Ther. 18:1265-77). In addition, we performed drug repurposing screens of multiple gynecologic cancer lines (Gorshkov K. et al. 2019. Transl Oncol. 12:441-52) and liver cancer lines to identify new therapeutics from among currently approved drugs as well as new drug targets. LYSOSOMAL STORAGE DISEASE: We have collaborated on a chaperone therapy for Mucopolysaccharidosis type IVA (MPS IVA), a rare lysosomal storage disease caused by mutations in the gene encoding the enzyme N-acetylgalactosamine-6-sulfate sulfatase (GALNS). Two GALNS pharmacological chaperone compounds, ezetimibe and pranlukast, were identified and their activity on MPS IVA patient cells were confirmed. We found that these two compounds bind to the active site of GALNS resulting in an increase of GALNS stability and activity. We also found that combination therapy of the recombinant GALNS with ezetimibe or pranlukast produced an additive effect. The results demonstrate that ezetimibe and pranlukast have the potential to be used as a monotherapy (chaperone therapy) or combination therapy with the recombinant GALNS to improve the efficacy of enzyme replacement therapy for treatment of MPS IVA (Almeciga-Diaz CJ et al. 2019. J Med Chem. 62:6175-6189). We previously found that delta-tocopherol reduces lysosomal accumulation of cholesterol and other lipids through enhancement of lysosomal exocytosis (Xu M. et al. 2012 J Biol Chem 287:37349- 60). We further studied the effect of delta-tocopherol on endocytosis. The results suggested that delta-tocopherol not only induces exocytosis of lysosomes but also reduces endocytic cargo and endocytosis. But this effect on endocytosis was transient and became unnoticeable several hours after tocopherol removal. Thus, induction of exocytosis in combination with therapies requiring endocytic uptake, such as ERT, may represent a new type of drug interaction, yet this strategy could be valuable if properly timed for minimal interference. (Manthe RL. Et al., 2019. J Pharmacol Exp Ther. 370:823-33). We also developed several induced pluripotent stem (iPS) cell lines derived from patients with lysosomal storage diseases and NGLY1 deficiency. These iPS cell lines have the genetic background associated with the diseases and individual patients, and can be used as disease models to study the pathophysiology of these diseases. They can also be developed into cell-based disease models for high throughput screening for drug development (details in the nine papers published in 2019). DRUG RESISTANT BACTERIA: Infections with multidrug-resistant (MDR) organisms have emerged as a significant worldwide public health crisis. The incidence is increasing, partially due to the selective pressure from widespread use of antibiotics in both humans and animals. One such fungal species, Candida auris, is responsible for several outbreaks in hospitals and care facilities. We have performed high throughput screening to identify individual drugs and synergistic drug combinations active against multidrug-resistant Candida auris. A set of approved and investigational drugs have been identified that are currently undergoing further confirmation studies. In response to the SARS-CoV-2 / COVID-19 pandemic, we have moved quickly to establish collaborations with academic researchers with expertise in virology and coronaviruses. We have worked on assay development and drug repurposing screens for several targets and phenotypic approaches to identify new therapeutic candidates from among currently approved and investigational drugs. This work is currently in progress.