Development of selective HDAC6 inhibitors with in vitro and in vivo anti-multiple myeloma activity.

Histone deacetylase 6 (HDAC6) is a promising therapeutic target for the treatment of cancers, neurodegenerative diseases and autoimmune disorders. Herein a novel series of pyrrolo[2,3-d]pyrimidine-based HDAC inhibitors were designed, synthesized and biologically evaluated, among which compounds 7a, 12a1, and 16a1 exhibited potent inhibitory activities and selectivities against HDAC6. Notably, compared with the well-known HDAC6 inhibitor Tubastatin A, our pyrrolo[2,3-d]pyrimidine-based HDAC6 inhibitors showed superior in vitro antiproliferative activity against human multiple myeloma cell lines RPMI 8226, U266 and MM.1S, while maintaining the low cytotoxicity against human breast cancer cell line MDA-MB-231 and two normal cell lines. The HDAC6 selective inhibition of one representative compound 12a1 in RPMI 8226 cells was confirmed by western blot analysis. Although pyrrolo[2,3-d]pyrimidine is a privileged structure in many kinase inhibitors, compound 12a1 showed negligible inhibition against several kinases including JAK family members and Akt1, indicating its acceptable off-target profile. Besides, compound 12a1 exhibited desirable metabolic stability in mouse liver microsome. The in vivo anti-multiple myeloma potency of 12a1, alone and in combination with bortezomib, was demonstrated in a RPMI 8226 xenograft model.

Synthesis and biological study of class I selective HDAC inhibitors with NO releasing activity.

Based on the multi-mechanism antitumor strategy and the regulatory effect of nitric oxide (NO) on histone deacetylases (HDACs), a series of N-acyl-o-phenylenediamine-based HDAC inhibitors equipped with the phenylsulfonylfuroxan module as NO donor was designed, synthesized and biologically evaluated. The in vitro HDAC inhibitory assays revealed that compared with the clinical class I selective HDAC inhibitor MS275, compounds 7c, 7d and 7e possessed similar HDAC inhibitory potency and selective profile, which were confirmed by the results of western blot analysis. The western blot analysis also showed that NO scavenger N-acetyl cysteine (NAC) could weaken the intracellular HDAC inhibitory ability of compound 7c, supporting the HDAC inhibitory effect of NO generated by 7c. It is worth noting that compounds 7c, 7d and 7e exhibited more potent in vitro antiproliferative activities than MS275 against all four tested solid tumor cell lines. The promising in vivo antitumor potency of 7c was demonstrated in a HCT116 xenograft model.

In vivo pharmacokinetic study and oral glucose tolerance test of sulfoxide analogs of GPR40 agonist TAK-875.

TAK-875 (compound 1) was the only GPR40 agonist with promising oral glucose-lowering effect, which entered phase III clinical trials. In previous studies, we successfully synthesized the TAK-875 sulfoxide analog 2, which was further separated to optically pure compounds 3 (S, S, 100.0% de) and 4 (R, S, 100.0% de). In vitro biological evaluation revealed that the sulfoxide analogs 3 and 4 possessed comparable GPR40 agonist activity to TAK-875. Herein, in order to further evaluate the druglikeness of TAK-875 sulfoxide analogs, the pharmacokinetic properties of compounds 2, 3, and 4 in rats were investigated and compared with that of TAK-875. The results showed that sulfoxide (2, 3, and 4) and sulfone (TAK-875) could be converted into each other in different degrees in vivo. Interestingly, compound 3 showed higher drug exposure calculated by the AUC sum of sulfoxide and sulfone in plasma than TAK-875, 2 and 4. In order to further investigate the in vivo glucose-lowering potency of sulfoxide analogs, asymmetric synthesis was carried out and led to two sulfoxides with moderate de values, 5 (S, S, 66.4% de) and 6 (R, S, 71.0% de). The following oral glucose tolerance test (OGTT) in rats showed that 5 (S, S, 66.4% de) had stronger glucose-lowering effect in vivo than 6 (R, S, 71.0% de) and TAK-875, which could be partly rationalized by the superior pharmacokinetic property of sulfoxide 3 (the main component of 5) relative to sulfoxide 4 (the main component of 6) and TAK-875.

Inhibitors of the GTPase KRASG12C in cancer: a patent review (2019-2021).

INTRODUCTION: KRAS is one of the most important oncology proteins, which can activate multiple downstream signaling pathways. Despite the prevalence of KRAS mutations in approximately 30% of human cancers, it has long been considered to be 'undruggable' due to the lack of recognizable binding pockets. AREAS COVERED: This review covers the recent patents (2019-2021) on KRASG12C inhibitors, which are mostly highlighted in terms of chemical structures, molecular mechanisms of action, pharmacokinetic properties, and potential clinical applications. EXPERT OPINION: The last 3 years have seen a significant breakthrough in the development of KRAS inhibitors. So far, ten compounds entered the clinical trials with AMG510 being approved by FDA in May 2021 for the treatment of lung cancer. Moreover, MRTX849 also holds the promise of becoming the next approved drug targeting KRASG12C. However, it is noteworthy that acquired resistance is expected to arise inevitably. With a potentially effective treatment on the horizon, combination strategies could further enhance the efficacy of KRAS-targeted inhibition. Whatever their strengths or limitations, emerging KRASG12C inhibitors will undoubtedly enrich our understanding of KRAS biology and KRAS-targeted therapy, which will shed light on the development of inhibitors targeting other KRAS mutations.

Characteristics of the cylindrical reflex triode driven by a four-stage linear transformer driver.

A cylindrical reflex triode was designed and directly driven by a four-stage linear transformer driver to generate high intensity pulsed warm x rays. We developed a numerical model of the cylindrical reflex triode and simulated and studied the experimental electron distribution and the radiation characteristics. The working voltage of the cylindrical reflex triode is 220 kV, and the current is about 600 kA. Under the voltage pulse with a rise time of 100 ns, the electron beam spot is uniform, and the duration of the gap without short circuit reaches 200 ns. The x-ray dose is 385 rad (Si), with an irradiation area of 615 cm2 and a uniformity of less than 2:1. The radiation field distribution is basically consistent with the simulation results. Compared with the two-stage series diode on the Flash-II accelerator, the x-ray conversion efficiency of the cylindrical reflex triode is increased about 1.6 times.

Discovery of Novel Pyrrolo[2,3-d]pyrimidine-based Derivatives as Potent JAK/HDAC Dual Inhibitors for the Treatment of Refractory Solid Tumors.

It remains a big challenge to develop HDAC inhibitors effective for solid tumors. Previous studies have suggested that the feedback activation of JAK-STAT3 pathway represents a key mechanism leading to resistance to HDAC inhibitors in breast cancer, suggesting the therapeutic promise of JAK/HDAC dual inhibitors. In this work, we discovered a series of pyrrolo[2,3-d]pyrimidine-based derivatives as potent JAK and HDAC dual inhibitors. Especially, compounds 15d and 15h potently inhibited JAK1/2/3 and HDAC1/6 and displayed antiproliferative and proapoptotic activities in triple-negative breast cancer cell lines. Besides, compounds 15d and 15h also diminished the activation of LIFR-JAK-STAT signaling triggered by tumor-associated fibroblasts, which suggests that these compounds could potentially overcome the drug resistance caused by the tumor microenvironment. More importantly, compound 15d effectively inhibited the tumor growth in MDA-MB-231 xenograft tumor model. Overall, this work provides valuable leads and novel antitumor mechanisms for the treatment of the SAHA-resistant triple-negative breast cancers.

Development of pyrazoline-based derivatives as aminopeptidase N inhibitors to overcome cancer invasion and metastasis.

Aminopeptidase N is considered as a promising anti-tumor target due to its role in tumor invasion, metastasis and angiogenesis. In this report, a new series of pyrazoline-based derivatives were designed, synthesized and evaluated for biological activities. The structure-activity relationships of these pyrazoline-based derivatives were also discussed in detail. Among them, compound 2k, with 2,6-dichloro substitution, showed the best APN inhibitory activity, of which the IC50 value was two orders of magnitude lower than that of the positive control bestatin. At the same concentration of 100 µM, the in vitro anti-invasion activity of compound 2k was also significantly better than that of bestatin. Moreover, compound 2k could effectively prevent the pulmonary metastasis of mice H22 hepatoma cells in vivo, supporting its further research and development as an antitumor agent.

Design, Synthesis, and Biological Evaluation of APN and AKT Dual-Target Inhibitors.

Herein a novel series of APN and AKT dual inhibitors were derived from the clinical AKT inhibitor AZD5363. It was demonstrated that most compounds exhibited remarkable APN inhibitory activities with the most potent compound 8b (IC50 = 0.05 ± 0.01 µM) being over 70-fold more potent than the approved APN inhibitor bestatin (IC50 = 3.64 ± 0.56 µM). The moderate AKT inhibitory potencies of target compounds were also confirmed, with 5f and 5h possessing AKT1 IC50 values of 0.12 and 0.27 µM, respectively. More importantly, the APN IC50 values of 5f and 5h were 0.96 and 0.21 µM, respectively, indicating their balanced APN and AKT dual inhibition. HUVEC tube formation assays confirmed the superior APN inhibitory activities of 5f and 5h relative to bestatin at the cellular level. Western blot analysis demonstrated that 5h could effectively inhibit the phosphorylation of GSK3ß, the intracellular substrate of AKT.

Histone deacetylase (HDAC) inhibitors in cancer: a patent review (2017-present).

Introduction: Histone deacetylase (HDAC) inhibitors play a crucial role in restoring the balance of acetylation and deacetylation of lysine residues of histones and non-histone proteins, which are applied to treat several diseases including cancer.Area covered: This review covers recent efforts in the synthesis and applications of inhibitors and hybrid inhibitors targeting HDAC from 2017 to 2019.Expert opinion: HDACs are important epigenetic targets and HDAC inhibitors have become important biologically active compounds for the treatment of cancers. Among the recent patents available, most of them place emphasis on HDAC selective inhibitors and multitarget HDAC inhibitors. Although great accomplishments have been achieved in developing HDAC selective inhibitors, there is still an urgent need for discovery of novel HDAC inhibitors with new zinc-binding groups avoiding the unfavorable pharmacokinetics profiles of hydroxamic acid. Apart from cancer therapy, HDAC inhibitors have recently been considered as a new strategy in treating other human diseases, such as alcohol use disorder (AUD), neurological disorders, age-related diseases, and so forth.

Discovery of a Novel Hybrid of Vorinostat and Riluzole as a Potent Antitumor Agent.

Vorinostat (suberoylanilide hydroxamic acid) was the first approved histone deacetylase (HDAC) inhibitor in a group of validated cancer therapeutic agents targeting epigenetics. Riluzole is a drug used to treat amyotrophic lateral sclerosis, the antitumor potency of which has been recently revealed. Herein, a novel hybrid of vorinostat and riluzole (compound 1) was rationally designed, synthesized, and evaluated. Compared with vorinostat, compound 1 exhibited superior total HDAC inhibitory activity and similar HDAC isoform selective profiles. The intracellular HDAC inhibition of compound 1 was confirmed by Western blot analysis. Moreover, compound 1 possessed more potent in vitro antiproliferative activity against all tested solid and hematological tumor cell lines than vorinostat. In vitro metabolic stability evaluation of compound 1 revealed better human plasma stability and comparable human liver microsomal stability than vorinostat. Additionally, compound 1 demonstrated more significant in vivo antitumor activity in a MDA-MB-231 xenograft model than vorinostat, which could be attributed to its superior in vitro antiproliferative activity and metabolic stability. Taken together, the results presented here support further research and development of compound 1 as a promising antitumor agent.

A two-stage series diode for intense large-area moderate pulsed X rays production.

This paper presents a method for moderate pulsed X rays produced by a series diode, which can be driven by high voltage pulse to generate intense large-area uniform sub-100-keV X rays. A two stage series diode was designed for Flash-II accelerator and experimentally investigated. A compact support system of floating converter/cathode was invented, the extra cathode is floating electrically and mechanically, by withdrawing three support pins several milliseconds before a diode electrical pulse. A double ring cathode was developed to improve the surface electric field and emission stability. The cathode radii and diode separation gap were optimized to enhance the uniformity of X rays and coincidence of the two diode voltages based on the simulation and theoretical calculation. The experimental results show that the two stage series diode can work stably under 700 kV and 300 kA, the average energy of X rays is 86 keV, and the dose is about 296 rad(Si) over 615 cm2 area with uniformity 2:1 at 5 cm from the last converter. Compared with the single diode, the average X rays' energy reduces from 132 keV to 88 keV, and the proportion of sub-100-keV photons increases from 39% to 69%.

Variation of anode grid surface morphology and its effect on operation of a triode virtual cathode oscillator.

After repeatedly operation of a triode virtual cathode oscillator, the surface morphology of anode grid is studied by a scanning electron microscope. It is found that there are many quasi-periodic sawteeth formed on the anode grid, which are about 300-500 µm in height, ~200 µm in width, and 150-200 µm in period. The formation of this sawteeth implies that there is possible Rayleigh-Taylor-like instability on the anode grid during the irradiation by high-current relativistic electron beam. These sawteeth enhance the electric field on anode grid, leading to more feasible of anode plasma generation, and more rapidly expansion of that plasma. As a result, the electron transmissivity of anode grid is decreased, the output microwave power of the virtual cathode oscillator is lowered and its operational performance is degraded.

Design of a simple annular electron beam source and its operating characteristics in single and repetitive shot modes.

In this work, design and performance of an annular carbon fiber cathode are presented. Measurements on this cathode were performed in a single high-voltage pulse generator (600 kV, 50 ns, and 50 Omega) and a repetitive one (350 kV, <10 ns, 180 Omega, and 100 Hz), respectively. In a single pulse regime, emphasis was placed on the uniformity of electron beam extracted from this cathode. It was found that this cathode could deliver uniform electron beams with current densities exceeding kA/cm(2). Cesium iodide (CsI) coating eliminated hot spots on the cathode surface, significantly improving the uniformity of electron emission. Under repetitively pulsed operation, this cathode exhibited a good shot-to-shot reproducibility at the pressure of 1.5x10(-4) Torr, suggesting an ability of surviving even in poor vacuum. However, once the base pressure rose up to 3.76x10(-4) Torr, the cathode performance gradually degraded as the pulse shot proceeded. Besides, some possible explanations for these experimental results are presented. These results show that given proper diode design, carbon fiber with CsI coating has great promise as electron emitter producing high-current electron beams.