The Development of HDAC and Tubulin Dual-Targeting Inhibitors for Cancer Therapy.

Histone deacetylases (HDACs) are a class of enzymes that are responsible for the removal of acetyl groups from the ε-N-acetyl lysine of histones, allowing histones to wrap DNA more tightly. HDACs play an essential role in many biological processes, such as gene regulation, transcription, cell proliferation, angiogenesis, migration, differentiation and metastasis, which make it an excellent target for anticancer drug discovery. The search for histone deacetylase inhibitors (HDACis) has been intensified, with numerous HDACis being discovered, and five of them have reached the market. However, currently available HDAC always suffers from several shortcomings, such as limited efficacy, drug resistance, and toxicity. Accordingly, dual-targeting HDACis have attracted much attention from academia to industry, and great advances have been achieved in this area. In this review, we summarize the progress on inhibitors with the capacity to concurrently inhibit tubulin polymerization and HDAC activity and their application in cancer treatment.

Development of VER-50589 analogs as novel Hsp90 inhibitors.

As an important target for tumor therapy, heat shock protein 90 has attracted tremendous attention. Through structure analysis, we rationally designed three analogs of VER-50589 which is a known and potent Hsp90 inhibitor. Target inhibitory activity result showed that one compound dubbed as 12-1 exhibited strong inhibitory activity against Hsp90 with an IC50 value of 9 nM. In tumor cell viability experiment, compound 12-1 robustly repressed the proliferation against six human tumor cells with IC50 values all in nanomolar range scoring over VER-50589 and geldanamycin. 12-1 was able to induce apoptosis of tumor cells and arrest the tumor cell cycle in G0/G1 phase. Meanwhile, western blot results showed that 12-1 could significantly downregulated the expression of two Hsp90 client proteins CDK4 and HER2. Finally, molecular dynamic simulation showed that compound 12-1 could fit well with ATP binding site on N-terminal of Hsp90.

Hybrid Histone Deacetylase Inhibitor: An Effective Strategy for Cancer Therapy.

Inhibition of histone deacetylases (HDACs) has proven to be an effective strategy for cancer therapy. To date, five histone deacetylase inhibitors (HDACis) have been approved for cancer treatment, and numerous others are undergoing clinical trials. An agent that can simultaneously and effectively inhibit two or more targets may offer greater therapeutic benefits over single-acting agents in preventing resistance to treatment and potentiating synergistic effects. A prime example of a bifunctional agent is the hybrid HDACi. Representative classes of reported hybrid HDACis are reviewed here to shed light on the design of novel hybrid HDACis for cancer therapy.

WRQ-2, a gemcitabine prodrug, reverses gemcitabine resistance caused by hENT1 inhibition.

Gemcitabine is widely used in the clinic as a first-line antitumor agent. However, intrinsic and acquired resistance hinders its wide clinical application. In this study, a gemcitabine prodrug nominated as WRQ-2 was designed and synthesized by conjugating gemcitabine with the indole-3-methanol analogue OSU-A9 through a carbamate linkage. WRQ-2 exhibited high cytotoxicity against six cancer cell lines (HeLa, A549, MDA-MB-231, HuH-7, MGC-803, and HCT-116) with IC50 values in low micromolar range. WRQ-2 reversed the resistance of HeLa cells to gemcitabine caused by hENT1 inhibition. Compared to gemcitabine, WRQ-2 induced a higher degree of DNA damage and apoptosis in the presence of hENT1 inhibitor. Our study suggests that compound WRQ-2 is a potential gemcitabine prodrug and worth of further antitumor activity investigation.

Design, synthesis and antitumor activity study of a gemcitabine prodrug conjugated with a HDAC6 inhibitor.

Gemcitabine, as a first-line antitumor drug, has attracted extensive attention. However the occurrence of drug resistance limits its clinical utilization. In this paper, a gemcitabine prodrug GZ was designed and synthesized by conjugation of gemcitabine with a newly reported HDAC6 selective inhibitor pentadecanoic acid. GZ displayed high cytotoxicity to nine cancer cell lines with IC50 values in the low micromolar range. In vivo, GZ displayed superior antitumor activity to gemcitabine in a 4T1 tumor xenograft model without obvious pathological damage to important organs of mice. Our study showed that compound GZ is a potential gemcitabine prodrug, which is worthy of further antitumor activity exploration.

Design, synthesis and antitumor activity study of PARP-1/HDAC dual targeting inhibitors.

Both poly(ADP-ribose)polymerase-1 (PARP-1) and histone deacetylase (HDAC) are important antitumor targets and have attracted extensive attention. In this work, a total of fourteen PARP-1/HDAC dual targeting inhibitors were designed and synthesized using either benzopyrazole or benzimidazole as core structures. Two leading compounds 1-8-6 and 1-8-7 were proven to be dual targeting inhibitors of PARP-1 and HDAC6, and showed high antiproliferative activities against six human cancer cell lines with IC50 values in micromole range. Moreover, compounds 1-8-6 and 1-8-7 could impair tumor cell proliferation in 48 h and 72 h with much higher potency than co-treatment of Olaparib and Tubastatin A. 1-8-6 displayed remarkable anti-migration and anti-angiogenesis activities. Meanwhile, western blot experiment result showed that 1-8-6 was able to heighten expression level of acetylated α-tubulin with marginal effects to acetylated histones H3 and H4. Finally, docking simulation work showed that 1-8-6 could fit into the active sites of PARP-1 and HDAC6. All results indicated that 1-8-6 is a promising candidate for further preclinical studies.

Cost-effectiveness of fuzuloparib compared to routine surveillance, niraparib and olaparib for maintenance treatment of patients with germline BRCA1/2 mutation and platinum-sensitive recurrent ovarian carcinoma in China.

Background: Maintenance therapy with the poly (ADP-ribose) polymerase inhibitors (PARPis) for platinum-sensitive recurrent ovarian carcinoma (OC) have proven to be effective compared with placebo. We aimed to evaluate the cost-effectiveness (CE) of maintenance fuzuloparib compared to routine surveillance (RS), niraparib and olaparib for platinum-sensitive recurrent OC from the Chinese healthcare systems. Method: A partitioned survival model with three-state (progression-free, progressed, death) was constructed utilizing TreeAge Pro 2011 software to evaluate the economic value of fuzuloparib, niraparib and olaparib maintenance treatment for platinum-sensitive recurrent OC based on the clinical data derived from FZOCUS-2, ENGOT-OV16/NOVA and ENGOT-Ov21/SOLO2. Transition probabilities were estimated from the reported survival probabilities in those trials. Cost and health preference data were derived from the literature. The quality-adjusted life-years (QALYs) and lifetime costs were measured for this analysis. A 5 years horizon and 5%/year discount rates were used. One-way analysis, and probabilistic sensitivity analysis (PSA) were performed to explore the model uncertainties. Results: Total cost of fuzuloparib, niraparib and olaparib were $31628.10, $48183.48 and $54605.54, whereas they had an incremental cost-utility ratio of $31992.69, $32216.08 and $23359.26 per additional progression-free survival (PFS) QALYs gained compared with RS, relatively. Model showed that maintenance fuzuloparib achieved at least an 85.5% probability of CE at the threshold of $37654.50/QALY. One-way sensitivity analysis revealed that the results were sensitive to the PFS and the price of medicines. Conclusion: Fuzuloparib was less cost-effective for patients with germline BRCA1/2 mutation and platinum-sensitive recurrent OC compared to olaparib, but was superior to niraparib from the Chinese healthcare systems perspective.

The design and synthesis of transient receptor potential vanilloid 3 inhibitors with novel skeleton.

Transient receptor potential vanilloid 3 (TRPV3) channel as a member of thermo TRPV subfamily is primarily expressed in the keratinocytes of the skin and sensory neurons, and plays critical roles in various physiological and pathological processes such as inflammation, pain sensation and skin disorders. However, TRPV3 studies have been challenging, in part due to a lack of research tools such as selective antagonists. Recently, we synthesized a series of cinnamate ester derivatives and evaluated their inhibitory activities on human TRPV3 channels expressed in HEK293 cells using whole-cell patch clamp recordings. And, we identified two potent TRPV3 antagonists 7c and 8c which IC50 values were 1.05 µM and 86 nM, respectively. It also showed good selectivity to other subfamily members of TRPV, such as TRPV1 and TRPV4.

Design, synthesis and antitumor activity evaluation of novel HDAC inhibitors with tetrahydrobenzothiazole as the skeleton.

HDACs as important targets for cancer therapy have attracted extensive attentions. In this work, a series of sixteen hydroxamic acid based HDAC inhibitors were designed and synthesized with 4,5,6,7-tetrahydrobenzothiazole as the structural core. Majority of them exhibited potent inhibitory activities against HDACs and one leading compound 6h was dug out. 6h was proven to be a pan-HDAC inhibitor and displayed high cytotoxicity against seven human cancer cell lines with IC50 values in low micromolar range. 6h could arrest cell cycle in G2/M phase and induce apoptosis in A549 cells. Moreover, compound 6h exhibited remarkable anti-migration and anti-angiogenesis activities. At the same time, 6h was able to elevate the expression of acetylated α-tubulin and acetylated histone H3 in a dose-dependent manner. Docking simulation revealed that 6h fitted well into the active sites of HDAC2 and 6. Finally, compound 6h also exerted potent antitumor effects in an A549 zebrafish xenograft model. Our study demonstrated that compound 6h was a promising candidate for further preclinical studies.

Small Molecular Gemcitabine Prodrugs for Cancer Therapy.

Gemcitabine as a pyrimidine nucleoside analog anticancer drug has high efficacy for a broad spectrum of solid tumors. Gemcitabine is activated within tumor cells by sequential phosphorylation carried out by deoxycytidine kinase to mono-, di-, and triphosphate nucleotides with the last one as the active form. But the instability, drug resistance and toxicity severely limited its utilization in clinics. In the field of medicinal chemistry, prodrugs have proven to be a very effective means for elevating drug stability and decrease undesirable side effects including the nucleoside anticancer drug such as gemcitabine. Many works have been accomplished in design and synthesis of gemcitabine prodrugs, majority of which were summarized in this review.

Drugs for the Treatment of Zika Virus Infection.

Zika virus is an emerging flavivirus that causes the neurodevelopmental congenital Zika syndrome and that has been linked to the neuroinflammatory Guillain-Barré syndrome. The absence of a vaccine or a clinically approved drug to treat the disease combined with the likelihood that another outbreak will occur in the future defines an unmet medical need. Several promising drug candidate molecules have been reported via repurposing studies, high-throughput compound library screening, and de novo design in the short span of a few years. Intense research activity in this area has occurred in response to the World Health Organization declaration of a Public Health Emergency of International Concern on February 1, 2016. In this Perspective, the authors review the emergence of Zika virus, the biology of its replication, targets for therapeutic intervention, target product profile, and current drug development initiatives.

Novel histone deacetylase inhibitors bearing a 4-piperidin-4-yl-triazole scaffold as antitumor agents.

Histone deacetylases have proven to be promising targets for the development of anticancer drugs. In this work, we reported the design and synthesis of a series of 20 novel hydroxamic acid-based histone deacetylase inhibitors with 4-piperidin-4-yl-triazole as the core structure. Five newly obtained compounds displayed excellent HDAC6 inhibitory activities. Among them, compounds WY-12 and WY-15 also exhibited excellent antiproliferative activities against six human tumor cell lines. WY-15 could increase the level of acetylated histone H3 in a dose-dependent manner. Furthermore, WY-15 remarkably induced cell cycle arrest of Sy5y cancer cells in G0 /G1 phase. Finally, the high potency of compound WY-15 toward HDAC6 was rationalized by molecular docking study.

Anti-tumor activity evaluation of novel tubulin and HDAC dual-targeting inhibitors.

Histone deacetylases (HDACs) have proven to be promising targets for the development of anti-cancer drugs. In this study, we reported a series of novel chalcone based tubulin and HDAC dual-targeting inhibitors. Three compounds inhibited the activities of HDAC and tubulin polymerization simultaneously and displayed anti-proliferative activities toward eleven human tumor cell lines. Compound 8a remarkably induced growth inhibition, apoptosis and G2/M phase arrest of A549 tumor cells. Finally, the inhibitory activities of 8a against HDAC6 and tubulin were rationalized by molecular docking studies.

Design and synthesis of novel histone deacetylase 6 inhibitors with benzyl-triazole as the core skeleton.

In the field of epigenetics, histone deacetylases (HDACs) are important members and well validated targets for anti-cancer drugs discovery. In this study, we designed and synthesized twenty-seven novel hydroxamic acid-based HDAC inhibitors (HDACis) with benzyl-triazole as the core skeleton. Most target compounds displayed excellent inhibition rates toward HDACs. Among them, compounds ZM-22 to ZM-27 with inhibition rates more than 90% toward HDACs exhibited potent inhibitory activity toward HDAC6, and ZM-23 possessed the best selectivity to HDAC6 over HDAC1. The high potency of compound ZM-23 toward HDAC6 was rationalized by molecular docking simulation. This series of compounds is worthy for further anti-cancer activity evaluation and structural optimization works.

Design, synthesis and biological evaluation of 4-piperidin-4-yl-triazole derivatives as novel histone deacetylase inhibitors.

Histone deacetylase is an important member of epigenetics and a well validated target for anti-cancer drug discovery. In this study, we designed and synthesized a series of twenty-one novel hydroxamic acid-based histone deacetylase inhibitors with 4-piperidin-4-yl-triazole as the core skeleton. Most target compounds displayed excellent inhibition rates toward histone deacetylases at the concentration of 1 µM. Among them, the inhibition rates of two compounds MH1-18 and MH1-21 exceeded 90%. Furthermore, these two compounds selectively inhibited the activity of histone deacetylase 6 with low IC50 values. The high potency of them toward histone deacetylase 6 was rationalized by molecular docking studies. We found that MH1-18 and MH1-21 moderately inhibited the proliferation of four human cancer cell lines SGC-7901, NCI-H226, MCF-7, and HL-60. However, MH1-21 showed potent efficacy in suppressing the migration of MCF-7 cells. Results obtained in the current study shed light on designing potent HDAC6 inhibitors as anti-cancer agents.

Novel HDAC6 selective inhibitors with 4-aminopiperidine-1- carboxamide as the core structure enhanced growth inhibitory activity of bortezomib in MCF-7 cells.

In epigenetics, histone deacetylases (HDACs) are well validated targets for the development of anticancer drugs. In this work, we reported the design and synthesis of a series of twenty two novel (E)-N-hydroxycinnamamide-based HDAC inhibitors with 4-aminopiperidine1-carboxamide as the core structure. Most newly synthesized compounds displayed high inhibition rates toward HDAC at the concentration of 1 µM. Among them, the inhibition rates of compounds LYP-2, LYP-3, LYP-6, and LYP-15 were more than 75%. Furthermore, compounds LYP-2, LYP-3, and LYP-6 potently inhibited the activity of HDAC6 with selectivity over HDAC1. We chose LYP-2 and LYP-6 to test its antiproliferative effect on breast cancer cells MCF-7. Either LYP-2 or LYP-6 alone moderately suppressed the cell growth, but could synergistically enhance the inhibitory effect of bortezomib. These results suggested that combined HDAC6 inhibitor and bortezomib regimen might be an option for breast cancer treatment.

Aspergiolides A and B: Core Structural Establishment and Synthesis of Structural Analogues.

The core structure of marine natural products aspergiolides A (1a) and B (1b) was achieved via a concise, two-step procedure with satisfactory yield. Based on this protocol, a natural products mimic library containing 25 structural simplified analogues of 1a was then constructed. Several prepared analogues showed potential cytotoxic activity against five different tumor cell lines, and compound 7bb, in particular, exhibited cytotoxicity comparable to that of 1a.

Kinase and Histone Deacetylase Hybrid Inhibitors for Cancer Therapy.

Histone deacetylases (HDACs), encompassing at least 18 members, are promising targets for anticancer drug discovery and development. To date, five histone deacetylase inhibitors (HDACis) have been approved for cancer treatment, and numerous others are undergoing clinical trials. It has been well validated that an agent that can simultaneously and effectively inhibit two or more targets may offer greater therapeutic benefits over single-acting agents in preventing resistance to treatment and in potentiating synergistic effects. A prime example of a bifunctional agent is the hybrid HDAC inhibitor. In this perspective, the authors review the majority of reported kinase/HDAC hybrid inhibitors.

Tip60: Main Functions and Its Inhibitors.

BACKGROUND: Tip60, the founding member of MYST histone acetyltransferase family, was originally identified as a cellular acetyltransferase protein that interacts with HIV-1 Tat. Tip60 plays roles in many processes such as cellular signaling transmission, DNA damage repair, cell cycle and checkpoint control and apoptosis by acetylating its histone or non-histone substrates. RESULTS: Dysfunction of Tip60 could promote or suppress diseases including different kinds of cancers. CONCLUSION: Here, main functions and its known inhibitors were summarized.

Discovery of N-hydroxy-4-(1H-indol-3-yl)butanamide as a histone deacetylase inhibitor.

The indoles plant growth hormones have exhibited potentially antitumor activities. However, the targets of these indoles have not been clearly elucidated. By introduction of hydroxamic acid group to the structure of indolebutyric acid, the derived molecule (IBHA) exhibited potent HDAC2 (IC50 value of 0.32 ± 0.02 µM) and HDAC3 (IC50 value of 0.14 ± 0.01 µM) inhibitory activities compared with SAHA (IC50 value of 1.25 ± 0.06 µM and 0.97 ± 0.04 µM against HDAC2 and HDAC3). In the antiproliferative assays, the tested hematologic cell lines (U937 and K562) are more sensitive to IBHA than the solid tumor cell lines (MDA-MB-231 and PC-3). In the docking studies, the derived molecule (IBHA) could bind to the active site of human HDAC2 and HDAC3 by strong H-bond interactions and hydrophobic interactions. Pharmacophore mapping results revealed that properties of IBHA matches the receptor (HDAC3) based pharmacophore model.