Lead optimization of dual tubulin and Hsp27 inhibitors

Targeting androgen receptor in glioblastoma

Glioblastomas are primary brain tumors that originate from glial stem cells or progenitor cells. There is a large difference in the incidence of glioblastoma between males and females. Studies revealed that the gender differences in the tumor may be attributable to the androgen receptor signaling axis. The incidence rate of glioblastoma in men is higher than that in women. Aberrant activation of the androgen receptor signaling pathway, or interactions between the androgen receptor signaling axis and other signaling axes promote the development of glioblastoma. Therefore, targeting the androgen receptor holds promise as a therapeutic approach for glioblastoma. This review investigates the dynamics of drug research into the treatment of glioblastoma by targeting the androgen receptor. The first finding in line with expectations is that androgen receptor antagonists, represented by enzalutamide, have been studied and shown to have anti-glioblastoma effects. In addition, it was found that the combination of 5-alpha reductase inhibitors and androgen receptor antagonists resulted in better therapeutic outcomes than each of them alone. Similar results were obtained with the combination of an epidermal growth factor receptor inhibitor and an androgen receptor antagonist. In addition, four small molecule compounds have been shown to exert significant anti-glioblastoma effects by directly or indirectly targeting the androgen receptor. Expectantly, one of these small molecules, seviteronel, progressed to the phase II clinical trial stage. These findings suggest that targeting the androgen receptor for glioblastoma may be a promising therapeutic option.

Pharmacokinetic study of an anti-trypanosome agent with different formulations and administration routes in mice by HPLC-MS/MS

Previously compound 12 showed great anti-trypanosome activity without toxicity in an in vivo study. In the current study, a sensitive and rapid high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed and validated to investigate its pharmacokinetics in mouse plasma. A protein precipitation method was applied to extract the compound, and it was then separated using a Kinetex C18 column with mobile phase consisting of acetonitrile-0.1% formic acid water (50:50, v/v) at a flow rate of 300 μl/min. The analytes were detected with the multiple reaction monitoring in negative electrospray ionization source for quantitative response of the compounds. Compound 12 was detected at m/z 477.0 → 367.2, while the internal standard compound 14 was detected at m/z 499.2 → 268.2. Inter- and intra-day precision was <5.22 and 2.79% respectively, while the accuracy range was within ±9.65%. The method was successfully applied to evaluate the pharmacokinetics of compound 12 in mouse plasma with two formulations (20% Cremophor EL or sesame oil) and drug administration routes (oral and intraperitoneal injection). We observed a better drug serum concentration with the Cremophor formulation, and the two different drug administration routes did not show significant differences from the drug distribution.

Small-Molecule HSP27 Inhibitor Abolishes Androgen Receptors in Glioblastoma

Androgen receptor (AR) contributes to the progression of glioblastoma (GBM), and antiandrogen agents have the potential to be used for the treatment of GBM. However, AR mutation commonly happens in GBM, which makes the antiandrogen agents less effective. Heat shock 27 kDa protein (HSP27) is a well-documented chaperone protein to stabilize ARs. Inhibition of HSP27 results in AR degradation regardless of the mutation status of ARs, which makes HSP27 a good target to abolish ARs in GBM. Compound I is a HSP27 inhibitor that significantly induces AR degradation in GBM cells via the proteasomal pathway, and it selectively inhibits AR-overexpressed GBM cell growth with IC50 values around 5 nM. The compound also significantly inhibits in vivo GBM xenograft at 20 mg/kg and does not cause toxicity to mice up to 80 mg/kg. These results suggest that targeting HSP27 to induce AR degradation in GBM is a promising and novel treatment.

Multi-Targeting Anticancer Agents: Rational Approaches, Synthetic Routes and Structure Activity Relationship

We live in a world with complex diseases such as cancer which cannot be cured with one-compound one-target based therapeutic paradigm. This could be due to the involvement of multiple pathogenic mechanisms. One-compound-various-targets stratagem has become a prevailing research topic in anti-cancer drug discovery. The simultaneous interruption of two or more targets has improved the therapeutic efficacy as compared to the specific targeted based therapy. In this review, six types of dual targeting agents along with some interesting strategies used for their design and synthesis are discussed. Their pharmacology with various types of the molecular interactions within their specific targets has also been described. This assemblage will reveal the recent trends and insights in front of the scientific community working in dual inhibitors and help them in designing the next generation of multi-targeted anti-cancer agents.

Synthesis and biological evaluation of anti-cancer agents that selectively inhibit Her2 over-expressed breast cancer cell growth via down-regulation of Her2 protein

Compound JCC76 selectively inhibited the proliferation of human epidermal growth factor 2 (Her2) over-expressed breast cancer cells. In the current study, a ligand based structural optimization was performed to generate new analogs, and we identified derivatives 16 and 17 that showed improved activity and selectivity against Her2 positive breast cancer cells. A structure activity relationship (SAR) was summarized. Compounds 16 and 17 were also examined by western blot assay to check their effect on Her2 protein. The results reveal that the compounds could decrease the Her2 protein, which explains their selectivity to Her2 over-expressed breast cancer cells. Furthermore, the compounds inhibited the chaperone activity of small chaperone protein that could stabilize Her2 protein.

Synthesis and biological evaluation of selective tubulin inhibitors as anti-trypanosomal agents

African trypanosomiasis is still a threat to human health due to the severe side-effects of current drugs. We identified selective tubulin inhibitors that showed the promise to the treatment of this disease, which was based on the tubulin protein structural difference between mammalian and trypanosome cells. Further lead optimization was performed in the current study to improve the efficiency of the drug candidates. We used Trypanosoma brucei brucei cells as the parasite model, and human normal kidney cells and mouse macrophage cells as the host model to evaluate the compounds. One new analog showed great potency with an IC₅₀ of 70nM to inhibit the growth of trypanosome cells and did not affect the viability of mammalian cells. Western blot analyses reveal that the compound decreased tubulin polymerization in T. brucei cells. A detailed structure activity relationship (SAR) was summarized that will be used to guide future lead optimization.

Synthesis, molecular docking and biological evaluation of 1-phenylsulphonyl-2-(1-methylindol-3-yl)-benzimidazole derivatives as novel potential tubulin assembling inhibitors

A series of new 1-phenylsulphonyl-2-(1-methylindol-3-yl)-benzimidazole derivatives were designed, synthesized and evaluated as potential inhibitors of tubulin polymerization and anthropic cancer cell lines. Among them, compound 33 displayed the most potent tubulin polymerization inhibitory activity in vitro (IC₅₀  = 1.41 μM) and strong antiproliferative activities against A549, Hela, HepG2 and MCF-7 cell lines in vitro with GI₅₀ value of 1.6, 2.7, 2.9 and 4.3 μM, respectively, comparable with the positive control colchicine (GI₅₀ value of 4.1, 7.2, 9.5 and 14.5 μM, respectively) and CA-4 (GI₅₀ value of 2.2, 4.3, 6.4 and 11.4 μM, respectively). Simultaneously, we evaluated that compound 33 could effectively induce apoptosis of A549 associated with G2/M phase cell cycle arrest. Immunofluorescence microscopy also clearly indicated compound 33 a potent antimicrotubule agent. Docking simulation showed that compound 33 could bind tightly with the colchicine-binding site and act as a tubulin inhibitor. Three-dimensional-QSAR model was also built to provide more pharmacophore understanding that could be used to design new agents with more potent tubulin assembling inhibitory activity in the future.

Orally Active and Selective Tubulin Inhibitors as Anti-Trypanosome Agents

Objectives

There is an urgent need to develop a safe, effective, orally active, and inexpensive therapy for African trypanosomiasis due to the drawbacks of current drugs. Selective tubulin inhibitors have the potential to be promising drug candidates for the treatment of this disease, which is based on the tubulin protein structural difference between mammalian and trypanosome cells. We propose to identify novel tubulin inhibitors from a compound library developed based on the lead compounds that selectively target trypanosomiasis.

Methods

We used Trypanosoma brucei brucei as the parasite model, and human normal kidney cells and mouse microphage cells as the host model. Growth rates of both trypanosomes and mammalian cells were determined as a means to screen compounds that selectively inhibit the proliferation of parasites. Furthermore, we examined the cell cycle profile of the parasite and compared tubulin polymerization dynamics before and after the treatment using identified compounds. Last, in vivo anti-parasite activities of these compounds were determined in T. brucei-infected mice.

Results

Three compounds were selected that are 100 fold more effective against the growth of T. brucei cells than mammalian cells. These compounds caused cell cycle progression defects in T. brucei cells. Western analyses indicated that these compounds decreased tubulin polymerization in T. brucei cells. The in vivo investigation revealed that these compounds, when admitted orally, inhibited T. brucei cell proliferation in mouse blood. However, they were not potent enough to clear up the infection completely.

Conclusions

These compounds are promising lead compounds as orally active agents for drug development of anti-trypanosome agents. A more detail structure activity relationship (SAR) was summarized that will be used to guide future lead optimization to improve the selectivity and potency of the current compounds.

Optimization of N-aryl-6-methoxy-1,2,3,4-tetrahydroquinolines as tubulin polymerization inhibitors

Thirteen new N-aryl 1,2,3,4-tetrahydroquinoline compounds (4a-f, 6a-c, and 8a-d) were synthesized and evaluated for antitumor activity and drug-like properties. Compound 4a exhibited high inhibitory potency with low nanomolar GI50 values of 16-20 nM in cellular assays, including excellent activity against the P-glycoprotein overexpressing cell line KBvin. Compound 4a inhibited colchicine binding to tubulin and tubulin assembly with an IC50 value of 0.85 μM, superior to the reference compound CA4 (1.2 μM) in the same assay. In addition, 4a also exhibited highly improved water solubility (75 μg/mL) and a suitable logP value (3.43) at pH 7.4. With a good balance between antitumor potency and drug-like properties, compound 4a could be a new potential drug candidate for further development. Current results on SAR studies and molecular modeling provided more insight about this class of compounds as tubulin polymerization inhibitors targeting the colchicine site.

Synthesis, biological evaluation, and molecular docking studies of novel 1-benzene acyl-2-(1-methylindol-3-yl)-benzimidazole derivatives as potential tubulin polymerization inhibitors

A series of 1-benzene acyl-2-(1-methylindol-3-yl)-benzimidazole derivatives were designed, synthesized and evaluated as potential tubulin polymerization inhibitors and for the cytotoxicity against anthropic cancer cell lines. Among the novel compounds, compound 11f was demonstrated the most potent tubulin polymerization inhibitory activity (IC50 = 1.5 μM) and antiproliferative activity against A549, HepG2 and MCF-7 (GI50 = 2.4, 3.8 and 5.1 μM, respectively), which was compared with the positive control colchicine and CA-4. We also evaluated that compound 11f could effectively induce apoptosis of A549 associated with G2/M phase cell cycle arrest. Docking simulation and 3D-QSAR model in these studies provided more information that could be applied to design new molecules with more potent tubulin inhibitory activity.