To discover group-1-specific neuraminidase (NA) inhibitors that are especially involved in combating the H5N1 virus, two series of oseltamivir derivatives were designed and synthesized by targeting the 150-cavity. Among these, compound 20l was the most potent N1-selective inhibitor, with IC50 values of 0.0019, 0.0038, and 0.0067 μM against NAs from three H5N1 viruses. These values are better than those of oseltamivir carboxylate. Compound 32 was another potent N1-selective inhibitor that exhibited a 12-fold increase in activity against the H274Y mutant relative to oseltamivir carboxylate. Molecular docking studies revealed that the 150-cavity was an auxiliary binding site that may contribute to the high selectivity of these compounds. The present work is a significant breakthrough in the discovery of potent group-1-specific neuraminidase inhibitors, which may be further investigated for the treatment of infection by the H5N1 virus.

Previously, we designed and synthesized a series of o-aminobenzamide-based histone deacetylase (HDAC) inhibitors, among which the representative compound 11a exhibited potent inhibitory activity against class I HDACs. In this study, we report the development of more potent hydrazide-based class I selective HDAC inhibitors using 11a as a lead. Representative compound 13b showed a mixed, slow, and tight binding inhibition mechanism for HDAC1, 2, and 3. The most potent compound 13e exhibited low nanomolar ICs toward HDAC1, 2, and 3 and could down-regulate HDAC6 in acute myeloid leukemia MV4-11 cells. The EC of 13e against MV4-11 cells was 34.7 nM, which is 26 times lower than its parent compound 11a. In vitro responses to 13e vary significantly and interestingly based on cell type: in p53 wild-type MV4-11 cells, 13e induced cell death via apoptosis and G1/S cell cycle arrest, which is likely mediated by a p53-dependent pathway, while in p53-null PC-3 cells, 13e caused G2/M arrest and inhibited cell proliferation without inducing caspase-3-dependent apoptosis.

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Herein a novel series of pazopanib hybrids as polypharmacological antitumor agents were developed based on the crosstalk between histone deacetylases (HDACs) and vascular endothelial growth factor (VEGF) pathway. Among them, one ortho-aminoanilide 6d and one hydroxamic acid 13f exhibited considerable total HDACs and VEGFR-2 inhibitory activities. The HDAC inhibitory activities endowed 6d and 13f with potent antiproliferative activities, which was not observed in the approved VEGFR inhibitor pazopanib. Compounds 6d and 13f possessed comparable HDAC isoform selectivity profiles to the clinical class I HDAC inhibitor MS-275 and the approved pan-HDAC inhibitor SAHA, respectively. 6d and 13f also exhibited uncompromised multiple tyrosine kinases inhibitory activities relative to pazopanib. The intracellular dual inhibition to HDAC and VEGFR of 6d and 13f was validated by Western blot analysis. In both HUVECs tube formation assay and rat thoracic aorta rings assay, 6d and 13f showed comparable antiangiogenic potencies to pazopanib. What's more, 6d possessed desirable pharmacokinetic profiles with the oral bioavailability of 72% in SD rats and considerable in vivo antitumor efficacy in a human colorectal adenocarcinoma (HT-29) xenograft model.

In our previous study, we designed and synthesized a novel series of N-hydroxycinnamamide-based HDAC inhibitors (HDACIs), among which the representative compound 14a exhibited promising HDACs inhibition and antitumor activity. In this current study, we report the development of a more potent class of N-hydroxycinnamamide-based HDACIs, using 14a as lead, among which, compound 11r gave IC50 values of 11.8, 498.1, 3.9, 2000.8, 5700.4, 308.2, and 900.4 nM for the inhibition of HDAC1, HDAC2, HDAC3, HDAC8, HDAC4, HDAC6, and HDAC11, exhibiting dual HDAC1/3 selectivity. Compounds 11e, 11r, 11w, and 11y showed excellent growth inhibition in multiple tumor cell lines. In vivo antitumor assay in U937 xenograft model identified compound 11r as a potent, orally active HDACI. To the best of our knowledge, this work constitutes the first report of oral active N-hydroxycinnamamide-based HDACIs with dual HDAC1/3 selectivity.

On the basis of the strategy of creating multifunctional drugs, a novel series of phenylsulfonylfuroxan-based hydroxamates with histone deacetylase (HDAC) inhibitory and nitric oxide (NO) donating activities were designed, synthesized, and evaluated. The most potent NO donor–HDAC inhibitor (HDACI) hybrid, 5c, exhibited a much greater in vitro antiproliferative activity against the human erythroleukemia (HEL) cell line than that of the approved drug SAHA (Vorinostat), and its antiproliferative activity was diminished by the NO scavenger hemoglobin in a dose-dependent manner. Further mechanism studies revealed that 5c strongly induced cellular apoptosis and G1 phase arrest in HEL cells. Animal experiment identified 5c as an orally active agent with potent antitumor activity in a HEL cell xenograft model. Interestingly, although compound 5c was remarkably HDAC6-selective at the molecular level, it exhibited pan-HDAC inhibition in a western blot assay, which is likely due to class I HDACs inhibition caused by NO release at the cellular level.

Histone deacetylase (HDAC) has emerged as an attractive target for the development of antitumor agents during the past decade. Previously tetrahydroisoquinoline-bearing hydroxamic acid analogue, ZYJ-25e (1), was identified and validated as a potent histone deacetylase inhibitor (HDACi) with marked in vitro and in vivo antitumor potency. In the present study, further modification of 1 led to another more potent, orally active HDACi, ZYJ-34c (4). Compared to FDA-approved drug suberoylanilide hydroxamic acid (SAHA), compound 4 exhibited higher in vivo antitumor potency in a human breast carcinoma (MDA-MB-231) xenograft model and in a mouse hepatoma-22 (H22) pulmonary metastasis model and similar in vivo antitumor potency in a human colon tumor (HCT116) xenograft model.

Concurrent inhibition of Janus kinase (JAK) and histone deacetylase (HDAC) could potentially improve the efficacy of the HDAC inhibitors in the treatment of cancers and resolve the problem of HDAC inhibitor resistance in some tumors. Here, a novel series of pyrimidin-2-aminopyrazol hydroxamate derivatives as JAK and HDAC dual inhibitors was designed, synthesized, and evaluated, among which 8m possessed potent and balanced activities against both JAK2 and HDAC6 with half-maximal inhibitory concentration at the nanomolar level. 8m exhibited improved antiproliferative and proapoptotic activities over SAHA and ruxolitinib in several hematological cell lines. Remarkably, 8m exhibited more potent antiproliferation effect than the combination of SAHA and ruxolitinib in HEL cells bearing JAK2 V617F mutation. Pharmacokinetic studies in mice showed that 8m possessed good bioavailability after intraperitoneal administration. Finally, 8m showed antitumor efficacy with no significant toxicity in a HEL xenograft model. Collectively, the results confirm the therapeutic potential of JAK and HDAC dual inhibitors in hematological malignancies and provide valuable leads for further structural optimization and antitumor mechanism study.