Structural Optimization And Biological Evaluation Of Benzodiazepines And Pyrrolidones As P53-MDM2Inhibitors

In recent years, environmental degradation, bad life habits and other factors have lead toa sharp rise in the incidence of malignant tumors, and become one of the leading causes ofdeath in most countries in the world. Most of the traditional treatment is cytotoxic drugs withbig side effects, and the effect is not very ideal. So it is necessary for us to develop newtreatments. The p53protein was first reported in1979and it was thought to be a tumorprotein at the beginning. After the structure of the p53protein was uncovered, people find thatthe tumor suppressor p53is one of the most important proteins in human cancers, and its mainfunctions are cell-cycle arrest, DNA repair, differentiation, senescence, and apoptosis.Although50%of all human tumors express wild-type p53, many are thought to haveinadequate p53function due to abnormalities in p53regulation or defective signaling in thep53pathway. Murine double minute2(MDM2) is an oncoprotein can inhibit p53’s ability tobind to DNA, activate transcription and promote rapid degradation of p53. In turn, p53activates the expression of the MDM2protein in an autoregulatory negative feedback loop.This target has many advantages, such as good selectivity, low toxic and side effects.Therefore, more and more investigators are attracted to this field. Having attract more andmore attention and research. Due to the crucial role of p53in tumour suppression, reactivationof the p53function by disruption of the p53-MDM2interaction is now recognized as a noveland promising strategy for anticancer drug design. There are two series of inhibitors about thistarget, peptide and non-peptide inhibitors. And the latter are got more attention. So far, manyseries of small-molecule inhibitors were described, including benzodiazepinediones, nutlins,spiro-oxindoles, quinolinols, isoindolinones, chlorofusin, norbornanes, sulfonamides,chalcones, terphenyls, and piperazine-4-phenyl derivatives. However, the majority of themshowed weak inhibitory activity. And the most potent p53MDM2inhibitors are the nutlins,the spiro-oxindoles and the benzodiazepinediones. So far, RG7112and RO5503781haveentered Phase I clinical trials.This project is a further research based on our preliminary work. We have designed andsynthesized two classes of compounds and evaluated their binding Kiconstants withp53-MDM2binding assays and in vitro antitumor activity. 1Design, synthesis and antitumor activity of benzodiazepine analogues asp53-MDM2inhibitors1.1Structure-activity relationship and antitumor activity of thio-benzodiazepinesIn our previous work, we reported and synthesized a series of thio-benzodiazepines withthe principle of bioisosterism and found that many compounds had nanomolar affinity towardMDM2and exhibited potent antitumor activities against the U-2OS human osteosarcoma cellline, which is worthy of further structural optimization. Herein, we designed and synthesizeda series of thio-benzodiazepines with electrophilic and nucleophilic groups on the benzenering to extend the SAR and find promising lead compounds with excellent biologicalproperties. In particular, two representative compounds, namely8i and8n, showed excellentbiological activity in both p53-MDM2binding affinity and in vitro antitumor activity. TheSAR study reveled that the substituents on sulphur atom led to significant decrease of activity,which may be due to the conformational change. Substitutions by halogen on other positionsretain good activity.1.2Design, synthesis and antitumor activities of sulfamide benzodiazepinesThe benzodiazepine was thought to be a “privileged structure” in medicinal chemistry.Encouraged by our previous result, we designed and synthesized8sulfamide benzodiazepineswith the principle of bioisosterism in order to break through the patent restrictions andincrease the solubility of the lead compound. We evaluate these compounds by p53-MDM2binding assay and in vitro antitumor activity. Unfortunately, we got an unexpected result.These compounds demonstrated poor biological activity because of conformation change. Thedata reveled the importance of the carboxyl on the position5.2. Design, synthesis and antitumor activities of pyrrolidones as p53-MDM2inhibitorsIn our previous work, we obtained a class of structurally novel p53-MDM2inhibitorsbearing pyrrolidone scaffold by structure-based virtual screening. Then we optimized the leadcompound and obtained two series of active compounds (amino-substituted pyrrolidones andether pyrrolidones). For the poor antitumor activity of the lead compound, we hypothesizedthat its low solubility affected the process in cells. Therefore, it is necessary to do furtherresearch on the pyrrolidone. On the one hand, we studied on the relationship between water solubility with activity. On the other hand we wanted to do further optimization and explorethe SAR of the N-substituent pyrrolidone. Thirty-one compounds were obtained andbiological activity showed that compounds13a,13b,13c and13d had poor antitumor activity.Thus, substituent on the hydroxyl group of the lead compound should be a crucial factor forits antitumor potency. Compounds7a-g and8a-g were dead in cells. The possible reason isthat the substituents on the nitrogen break the conformation so that these compounds cannotmimic the critical residues of the p53. When introducing saturated heterocycles on thehydroxyl group (eg. compounds11a,11b and11c), medium activity in cells was obseverd.Ester compounds (15a,15b,15c,15d,15f,16b) possess excellent biological activity. Wespeculated that these compounds might also affect other targets due to the scaffold has bigchanges.