Synthesis and antibacterial activities of heterocyclic ring-fused 20(S)-protopanaxadiol derivatives.

Multidrug-resistant (MDR) bacterial infections are becoming a life-threatening issue in public health; therefore, it is urgent to develop novel antibacterial agents for treating infections caused by MDR bacteria. The 20(S)-protopanaxadiol (PPD) derivative 9 was identified as a novel antibacterial hit compound in screening of our small synthetic natural product-like (NPL) library. A series of novel PPD derivatives with heterocyclic rings fused at the C-2 and C-3 positions of the A-ring were synthesized and their antibacterial activities against Staphylococcus aureus (S. aureus) Newman strain and MDR S. aureus strains (USA300, NRS-1, NRS-70, NRS-100, NRS-108, NRS-271, XJ017, and XJ036) were evaluated. Among these compounds, quinoxaline derivative 56 (SH617) exhibited the highest activity with MICs of 0.5-4 µg/mL against the S. aureus Newman strain and the eight MDR S. aureus strains. Its antibacterial activity was comparable to that of the positive control, vancomycin. In the zebrafish, 56 revealed no obvious toxicity even at a high administered dose. In vivo, following a lethal infection induced by USA300 strains in zebrafish, 56 exhibited significantly increased survival rates in a dose-dependent manner.

Synthesis of Heterocyclic Ring-Fused Bisnoralcohol Derivatives as Novel Small-Molecule Antiosteoporosis Agents.

A series of heterocyclic ring-fused derivatives of bisnoralcohol (BA) were synthesized and evaluated for their inhibitory effects on RANKL-induced osteoclastogenesis. Most of these derivatives possessed potent antiosteoporosis activities in a dose-dependent manner. Among these compounds, 31 (SH442, IC50 = 0.052 µM) exhibited the highest potency, displaying 100% inhibition at 1.0 µM and 82.8% inhibition at an even lower concentration of 0.1 µM, which was much more potent than the lead compound BA (IC50 = 2.325 µM). Cytotoxicity tests suggested that the inhibitory effect of these compounds on RANKL-induced osteoclast differentiation did not result from their cytotoxicity. Mechanistic studies revealed that SH442 inhibited the expression of osteoclastogenesis-related marker genes and proteins, including TRAP, TRAF6, c-Fos, CTSK, and MMP9. Especially, SH442 could significantly attenuate bone loss of ovariectomy mouse in vivo. Therefore, these BA derivatives could be used as promising leads for the development of a new type of antiosteoporosis agent.

A sterol analog inhibits hedgehog pathway by blocking cholesterylation of smoothened.

The hedgehog (Hh) signaling pathway has long been a hotspot for anti-cancer drug development due to its important role in cell proliferation and tumorigenesis. However, most clinically available Hh pathway inhibitors target the seven-transmembrane region (7TM) of smoothened (SMO), and the acquired drug resistance is an urgent problem in SMO inhibitory therapy. Here, we identify a sterol analog Q29 and show that it can inhibit the Hh pathway through binding to the cysteine-rich domain (CRD) of SMO and blocking its cholesterylation. Q29 suppresses Hh signaling-dependent cell proliferation and arrests Hh-dependent medulloblastoma growth. Q29 exhibits an additive inhibitory effect on medulloblastoma with vismodegib, a clinically used SMO-7TM inhibitor for treating basal cell carcinoma (BCC). Importantly, Q29 overcomes resistance caused by SMO mutants against SMO-7TM inhibitors and inhibits the activity of SMO oncogenic variants. Our work demonstrates that the SMO-CRD inhibitor can be a new way to treat Hh pathway-driven cancers.

Synthesis and Biological Evaluation of Heterocyclic Ring-Fused 20(S)-Protopanaxadiol Derivatives as Potent Antiosteoporosis Agents.

A series of heterocyclic ring-fused derivatives of 20(S)-protopanaxadiol (PPD) were synthesized and evaluated for their inhibitory effects on RANKL-induced osteoclastogenesis. Among these compounds, 33 (SH491, IC50 = 11.8 nM) showed the highest potency with 100% inhibition at 0.1 µM and 44.4% inhibition at an even lower concentration of 0.01 µM, which was much more potent than the lead compound PPD (IC50 = 10.3 µM). Cytotoxicity tests indicated that the inhibitory effect of these compounds on RANKL-induced osteoclast differentiation was not due to their cytotoxicity. Interestingly, SH491 also exhibited a notable impact on the osteoblastogenesis of MC3T3-E1 preosteoblasts. Mechanistic studies revealed that SH491 inhibits the expression of osteoclastogenesis-related marker genes and proteins, including TRAP, CTSK, MMP-9, and ATPase v0d2. In vivo, SH491 could dramatically decrease the ovariectomy-induced osteoclast activity and relieve osteoporosis obviously. Thus, these PPD derivatives could be served as promising leads for the development of novel antiosteoporosis agents.

Synthesis of heterocyclic ring-fused analogs of HMG499 as novel degraders of HMG-CoA reductase that lower cholesterol.

HMG-CoA reductase (HMGCR) is the rate-limiting enzyme in cholesterol de novo biosynthesis and its degradation may bring therapeutic benefits for the treatment of cardiovascular disease (CVD) and nonalcoholic steatohepatitis (NASH). Before, we disclosed compound HMG499 as a potent HMGCR degrader, which could be a promising agent for treating CVD, however its side-effect of promoting cholesterol accumulation in cells should be eliminated before progression. Herein, a series of novel heterocyclic ring-fused analogs of HMG499 were synthesized and investigated for their activities of stimulating HMGCR degradation using a HMGCR (TM1-8)-GFP reporting system. Among them, the most active compound 29 (QH536) showed an EC50 of 0.22 µΜ in promoting HMGCR degradation, which was about 2 times more potent than HMG499 (EC50 = 0.43 µM). Interestingly, 29 was different from HMG499, it had no side-effect of inducing cholesterol accumulation in cells. Mechanistic studies disclosed that 29 could significantly decrease statin-induced accumulation of HMGCR protein via ubiquitination and degradation of HMGCR through ubiquitin-proteasome pathway and inhibit the cholesterol biosynthesis in cells. Therefore, these heterocyclic ring-fused analogs could be used as promising leads for the development of new types of agents against CVD. Furthermore, 29 also lowered cholesterol levels and suppressed TGFß1-induced proliferation of LX-2 hepatic stellate cells in a dose-dependent manner. In particular, 29 not only decreased the NASH associated fibrotic mRNA and protein expression of α-SMA, COL1A1, TIMP1 and TGFß1 but also suppressed cholesterol levels and inflammatory genes of TNF-α, IL-6 an IL-1ß in RAW264.7 macrophage cells, indicating that 29 may bring therapeutic benefit to treat NASH.

Cholesterylation of Smoothened is a calcium-accelerated autoreaction involving an intramolecular ester intermediate.

Hedgehog (Hh) is a morphogen that binds to its receptor Patched 1 and activates Smoothened (SMO), thereby governing embryonic development and postnatal tissue homeostasis. Cholesterol can bind and covalently conjugate to the luminal cysteine-rich domain (CRD) of human SMO at the D95 residue (D99 in mouse). The reaction mechanism and biological function of SMO cholesterylation have not been elucidated. Here, we show that the SMO-CRD undergoes auto-cholesterylation which is boosted by calcium and involves an intramolecular ester intermediate. In cells, Hh stimulation elevates local calcium concentration in the SMO-localized endosomes through store-operated calcium entry. In addition, we identify the signaling-incompetent SMO D95E mutation, and the D95E mutant SMO can bind cholesterol but cannot be modified or activated by cholesterol. The homozygous SmoD99E/D99E knockin mice are embryonic lethal with severe developmental delay, demonstrating that cholesterylation of CRD is required for full-length SMO activation. Our work reveals the unique autocatalytic mechanism of SMO cholesterylation and an unprecedented role of calcium in Hh signaling.

Synthesis of plant-derived cholesterol from bisnoralcohol.

Currently, the market demand of the non-animal-derived cholesterol is increasing. A novel synthetic route of producing cholesterol was developed through multiple reactions from plant-sourced and commercially available bisnoralcohol (BA). The key reaction conditions, including solvents, reaction temperatures, bases and reducing agents of the route were investigated and optimized. In this straightforward synthetic pathway of cholesterol, most of the reaction steps possess high conversions with average yields of 94%, and the overall yield is up to 74% (5 steps) from the BA. The epicholesterol and were also synthesized. This promising route offers economical and efficient strategies for potential large-scale production of plant-derived cholesterol.

Targeting STAT3 by a small molecule suppresses pancreatic cancer progression.

Pancreatic cancer is lethal in over 90% of cases since it is resistant to current therapeutic strategies. The key role of STAT3 in promoting pancreatic cancer progression has been proven, but effective interventions that suppress STAT3 activities are limited. The development of novel anticancer agents that directly target STAT3 may have potential clinical benefits for pancreatic cancer treatment. Here, we report a new small-molecule inhibitor (N4) with potent antitumor bioactivity, which inhibits multiple oncogenic processes in pancreatic cancer. N4 blocked STAT3 and phospho-tyrosine (pTyr) peptide interactions in fluorescence polarization (FP) assay, specifically abolished phosphor-STAT3 (Tyr705), and suppressed expression of STAT3 downstream genes. The mechanism involved the direct binding of N4 to the STAT3 SH2 domain, thereby, the STAT3 dimerization, STAT3-EGFR, and STAT3-NF-κB cross-talk were efficiently inhibited. In animal models of pancreatic cancer, N4 was well tolerated, suppressed tumor growth and metastasis, and significantly prolonged survival of tumor-bearing mice. Our results offer a preclinical proof of concept for N4 as a candidate therapeutic compound for pancreatic cancer.

Synthesis of ursodeoxycholic acid from plant-source (20S)-21-hydroxy-20-methylpregn-4-en-3-one.

A novel synthetic route of producing ursodeoxycholic acid (UDCA) was developed through multiple reactions from cheap and commercially available bisnoralcohol (BA). The key reaction conditions, including solvents, bases and reaction temperatures of the route were investigated and optimized. In the straightforward route for preparation of UDCA, most of the reaction steps have high conversions with average yields of 91%, and overall yield up to 59% (6 steps) from the plant-source BA. Especially in the last step of reduction and hydrolysis, there are five functional groups converted with calcd 97% per conversion in one-pot reaction. This promising route offers economical and efficient strategies for potential large-scale production of UDCA.

Regression of castration-resistant prostate cancer by a novel compound QW07 targeting androgen receptor N-terminal domain.

Androgen deprivation therapy (ADT) via surgical or chemical castration frequently fails to halt lethal castration-resistant prostate cancer (CRPC), which is induced by multiple mechanisms involving constitutive androgen receptor (AR) splice variants, AR mutation, and/or de novo androgen synthesis. The AR N-terminal domain (NTD) possesses most transcriptional activity and is proposed as a potential target for CRPC drug development. We constructed a screening system targeting AR-NTD transcription activity to screening a compound library and identified a novel small molecule compound named QW07. The function evaluation and mechanism investigation of QW07 were carried out in vitro and in vivo. QW07 bound to AR-NTD directly, blocked the transactivation of AR-NTD, blocked interactions between co-regulatory proteins and androgen response elements (AREs), inhibited the expression of genes downstream of AR, and inhibited prostate cancer growth in vitro and in vivo. QW07 was demonstrated as an AR-NTD-specific antagonist with the potential to inhibit both canonical and variant-mediated AR signaling to regress the CRPC xenografts and is proposed as a lead compound for a specific antagonist targeting AR-NTD.

Synthesis and Preliminary Evaluation of [11 C]GNE-1023 as a Potent PET Probe for Imaging Leucine-Rich Repeat Kinase†2 (LRRK2) in Parkinson's Disease.

Leucine-rich repeat kinase 2 (LRRK2) is a large protein involved in the pathogenesis of Parkinson's disease (PD). It has been demonstrated that PD is mainly conferred by LRRK2 mutations that bring about increased kinase activity. As a consequence, selective inhibition of LRRK2 may help to recover the normal functions of LRRK2, thereby serving as a promising alternative therapeutic target for PD treatment. The mapping of LRRK2 by positron emission tomography (PET) studies allows a thorough understanding of PD and other LRRK2-related disorders; it also helps to validate and translate novel LRRK2 inhibitors. However, no LRRK2 PET probes have yet been reported in the primary literature. Herein we present a facile synthesis and preliminary evaluation of [11 C]GNE-1023 as a novel potent PET probe for LRRK2 imaging in PD. [11 C]GNE-1023 was synthesized in good radiochemical yield (10 % non-decay-corrected RCY), excellent radiochemical purity (>99 %), and high molar activity (>37 GBq µmol-1 ). Excellent in vitro binding specificity of [11 C]GNE-1023 toward LRRK2 was demonstrated in cross-species studies, including rat and nonhuman primate brain tissues by autoradiography experiments. Subsequent whole-body biodistribution studies indicated limited brain uptake and urinary and hepatobiliary elimination of this radioligand. This study may pave the way for further development of a new generation of LRRK2 PET probes.

Synthesis and biological evaluation of methylpyrimidine-fused tricyclic diterpene analogs as novel oral anti-late-onset hypogonadism agents.

Male late-onset hypogonadism (LOH) is reported as one of the most common age-related diseases occurred in middle-aging men. Testosterone replacement therapy (TRT) is currently the main clinical treatment for LOH, however it has obvious side effects. A 2-methylpyrimidine-fused tricyclic diterpene analog 7 was afforded as anti-LOH hit, which was screened out from our small synthetic library. Then a series of derivates were designed and synthesized based on the hit and their effects in promoting testosterone production and cytotoxicities were evaluated in mouse TM3 Leydig cells. The most potent and safe compound 29 (SH379) was obtained, which significantly promoted the expression of the key testosterone synthesis-related enzymes StAR and 3ß-HSD. Further studies discovered that 29 could stimulate autophagy through regulating AMPK/mTOR signaling pathway. More importantly, 29 increased the testosterone levels and the sperm viability and motility in PADAM (partial androgen deficiency in aging males) rats obviously and displayed almost no side effects. Furthermore, Preliminary pharmacokinetics evaluation also indicated an excellent oral bioavailability of 29. Therefore, these methylpyrimidine-fused tricyclic diterpene analogs could be used as leads for the development of a new type of potential anti-LOH agent.

Diastereoselective synthesis of 3,3-disubstituted 3-nitro-4-chromanone derivatives as potential antitumor agents.

We report an efficient and highly diastereoselective protocol for the rapid construction of 3-nitro substituted 4-chromanones by an intramolecular Michael-type cyclization of α-nitro aryl ketones bearing unsaturated ester units. A catalytic amount of KOtBu was found to be crucial for the high diastereoselective control of this transformation. With this protocol, a series of 3,3-disubstituted 3-nitro-4-chromanones were synthesized in good to excellent yields with high diastereoselectivities and showed moderate to good in vitro antitumor activities, representing promising antitumor hits for further drug discovery.

Discovery of methylpyrimidine ring-fused diterpenoid analogs as a novel testosterone synthesis promoter.

Herein we screened our small synthetic library of diterpenoid analogs for hit compounds on promoting testosterone synthesis and the methylpyrimidine ring-fused diterpenoid analog 7 was obtained as the hit. Based on the hit, a series of derivatives were designed, synthesized and evaluated for their effects on testosterone secretion in mouse Leydig TM3 cells. Most of the derivatives showed better activity in promoting testosterone synthesis than the positive control compound icariin, among which compound 17 has optimal activity and little cytotoxicity. Preliminary mechanism studies indicated that 17 significantly promoted the expression of testosterone synthesis-related marker genes (StAR, 3ß-HSD and CYP11A1). Further studies showed that 17 provided sufficient steroid materials for testosterone synthesis by stimulating autophagy in Leydig cells. Thus compound 17 emerged as a potential lead compound for further development of therapeutics for late onset of hypogonadism (LOH).

Synthesis and biological evaluation of 3-nitro-4-chromanone derivatives as potential antiproliferative agents for castration-resistant prostate cancer.

A series of novel 3-nitro-4-chromanones were synthesized and their in vitro cytotoxicity was evaluated on castration-resistant prostate cancer cell (CRPC) lines using the sulforhodamine B (SRB) assay. The amide derivatives showed more potent antitumor activity than their corresponding ester derivatives. Most of the tested compounds showed less toxicity towards human fibroblasts (HAF) compared with the tumor cell lines. The optimal compound 36 possessed much more potent antiproliferative activity than the positive compound cisplatin. The colony formation, cell cycle distribution, apoptosis, transwell migration and wound healing assays of 36 were performed on CRPC cell lines.

Discovery of a potent HMG-CoA reductase degrader that eliminates statin-induced reductase accumulation and lowers cholesterol.

Statins are inhibitors of HMG-CoA reductase, the rate-limiting enzyme of cholesterol biosynthesis, and have been clinically used to treat cardiovascular disease. However, a paradoxical increase of reductase protein following statin treatment may attenuate the effect and increase the side effects. Here we present a previously unexplored strategy to alleviate statin-induced reductase accumulation by inducing its degradation. Inspired by the observations that cholesterol intermediates trigger reductase degradation, we identify a potent degrader, namely Cmpd 81, through structure-activity relationship analysis of sterol analogs. Cmpd 81 stimulates ubiquitination and degradation of reductase in an Insig-dependent manner, thus dramatically reducing protein accumulation induced by various statins. Cmpd 81 can act alone or synergistically with statin to lower cholesterol and reduce atherosclerotic plaques in mice. Collectively, our work suggests that inducing reductase degradation by Cmpd 81 or similar chemicals alone or in combination with statin therapy can be a promising strategy for treating cardiovascular disease.

A facile synthesis of ursodeoxycholic acid and obeticholic acid from cholic acid.

A novel synthetic route of producing ursodeoxycholic acid (UDCA) and obeticholic acid (OCA) was developed through multiple reactions from cheap and readily-available cholic acid. The reaction conditions of the key elimination reaction of mesylate ester group were also investigated and optimized, including solvent, base and reaction temperature. In the straightforward synthetic route for preparation of UDCA and OCA, most of the reaction steps have high conversions with average yields of 94% and 92%, and overall yield up to 65% (7 steps) and 36% (11 steps) from cholic acid, respectively. This promising route offers economical and efficient strategies for potential large-scale production of UDCA and OCA.

Synthesis of Cyanoenone-Modified Diterpenoid Analogs as Novel Bmi-1-Mediated Antitumor Agents.

Bmi-1 is overexpressed in colorectal cancer (CRC) and served as a novel therapeutic target for the treatment of CRC. A series of novel cyanoenone-modified diterpenoid analogs was synthesized and investigated for their antiproliferative activity against CRC cells. The results showed that most of these compounds exhibited potent antiproliferative and Bmi-1 inhibitory activity. Among them, the most active compound 33 (SH498) showed more potent antiproliferative activity than the positive control compound PTC-209. These synthetic diterpenoid analogs were less toxic for normal human fibroblasts (HAF) than for CRC cells. Especially 33, its selectivity index (SI) between HAF and tumor cells was 7.3-13.1, which was much better than PTC-209. The polycomb repressive complex 1 (PRC1) complex, transwell migration, colony formation, cancer stem cell proliferation, and apoptosis assays of 33 were performed on CRC cell lines. The in vivo antitumor effect of 33 was also observed in HCT116 tumor-bearing mice.