Today let’s go on talking about PLK inhibitor. Yesterday I mentioned that PLK1 plays a key role in the mitotic entry, centrosome duplication, bipolar mitotic spindle formation, transition from metaphase to anaphase, cytokinesis and maintenance of genomic stability. Some PLK inhibitors were developed to using in cancer therapy. BI 2536 and GSK461364A are under clinical trials have the study results revealed that they both have potency in cancer treatment. Italo Beria et al. found that 4,5-dihydro-1H-pyrazolo[4,3-h]quinazoline is a wonderful scaffold to obtain potent and selective PLK1 inhibitors. They did some research on this scaffold to develop the potency, selectivity and oral bioavailability of this compound prospect to find new PLK1 inhibitors. Their study results were published on Bioorganic & Medicinal Chemistry Letters (2011). We all know that surgery, chemotherapy and irradiation are most important therapy for cancer. But these treatment methods bring so many side effects which presents must suffering such as cardiac dysfunction, hearing loss and infertility. How to reduce side effects of chemotherapeutics becomes a hot topic in drug discovery. Growing scientists devote their time finding potent and harmfulness chemotherapeutics. Lots of study results proved that tumor initiating cells take part in multiple malignancies and are responsible for sustaining tumor growth, progression, relapse and metastases. So targeting tumor initiating cells may be an effective way to find new compounds for treating cancer. The mother compound is shown as above, the researchers did some structural modification on 5’ and 1 position, and obtained a series of derivates. Among these derivates, they found 7g (NMS-P937) is the most potency compound, and they did some PK/PD and in vivo activity studies using this compound. The i.v. PK results of 7g shown that AUC is about 8.57M h, CL is about 2.36L/h/kg. t1/2 is about 0.89h. the p.o. PK data of 7g shown that AUC is about 2.04M h, Cmax is about 0.64M, t1/2 is about 1.60. The in vivo activity study was performed in HCT116 tumor cell inoculation nude mice. The treatment method is 1-3 bid*2 weekly cycles. The dose is 45mg/kg. The data shown that %TGImax is about 83 day, the %BWLmax is about 16 day. Natalie Grinstein et al. did some research about this issue and published their finding on Cancer Res (2011). NB TICs, skin-derived precursor cells, SMS-KCNR, SK-N-AS cells were cultured for screening assay. In their primary screening assay, 143 drugs active against at least 48 individual knases was tested. Within 143 small molecular inhibitors, the researchers found 15 compounds inhibited NB-TIC growth with high potency. To determine the most potent and selective compounds, they performed a secondary screening using the compounds screened from primary screening. In this study, they found PLK1 inhibitors, GW843682X and BI 2536, showed excellent potency as well as more than 10-fold selectivity toward NB TICs than for SKPs. So they do some further research for these two inhibitors using Western Blot, flow cytometry, Xenograft models etc to discover the mechanism of PLK inhibitors. They found: 1) BI 2536 treatment induces cell-cycle arrest and aberrant accumulation of cyclin B1 and p21. 2) BI 2536 treatment induces cell death via apoptosis. 3) BI 2536 suppresses NB tumor growth in a therapeutic xenograft model as a single agent and in combination with irinotecan. Related Posts: PLK Inhibitor BI 2536 in Drug Resistance PLK Inhibitor: Potent Way to Treating Neuroblastoma Review of PLK1 Inhibitors
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