Structural development of biological response modifiers based on thalidomide

Electrophotocatalytic diamination of vicinal C-H bonds

The conversion of unactivated carbon-hydrogen (C-H) bonds to carbon-nitrogen (C-N) bonds is a highly valued transformation. Existing strategies typically accomplish such reactions at only a single C-H site because the first derivatization diminishes the reactivity of surrounding C-H bonds. Here, we show that alkylated arenes can undergo vicinal C-H diamination reactions to form 1,2-diamine derivatives through an electrophotocatalytic strategy, using acetonitrile as both solvent and nitrogen source. The reaction is catalyzed by a trisaminocyclopropenium (TAC) ion, which undergoes anodic oxidation to furnish a stable radical dication while the cathodic reaction reduces protons to molecular hydrogen. Irradiation of the TAC radical dication (wavelength of maximum absorption of 450 to 550 nanometers) with a white-light compact fluorescent light generates a strongly oxidizing photoexcited intermediate. Depending on the electrolyte used, either 3,4-dihydroimidazole or aziridine products are obtained.

[Development of Biological Response Modifiers Based on Unique Medicinal Chemical Strategy]

Chemical biology and structural development studies performed at The University of Tokyo during 1977-2020 are outlined chronologically. The studies are divided into three parts, i.e., (i) chemical biology of chemical carcinogenesis and molecular design of anti-tumor agents, (ii) structural development studies on biological response modifiers, and (iii) studies on so-called dramatype drug discovery focusing on pharmacological chaperones and protein knockdown-inducers. The first part describes analysis of DNA modification by Glu-P-1, which is a typical carcinogenic heterocyclic amine found in cooked foods, as well as molecular design of DNA-cleaving agents with anti-tumor properties. The second part deals with structural development studies of nuclear receptor ligands and various biological response modifiers derived from thalidomide, including the ligand superfamily concept and the multi-template strategy. The third part describes pharmacological chaperones that should be useful for the treatment of protein misfolding diseases, including Niemann-Pick type C disease and retinitis pigmentosa, and a protein knockdown strategy aimed at degradation of neurodegenerative-disease-causing polyglutamic aggregative proteins.

Substituted adamantylphthalimides: Synthesis, antiviral and antiproliferative activity

In this study, three groups of adamantylphthalimides, bearing different substituents at the phthalimide moiety, N-(4'-R² )phthalimidoadamantanes (1-7), 3-[N-(4'-R² )phthalimido]-1-adamantanols (8-10), and 3-[N-(4'-R² )phthalimido]adamantane-1-carboxylic acids (11-15), were synthesized and screened against tumor cells and viruses. The most potent compounds are not substituted at the adamantane and bear an OH or NH₂ substituent at the phthalimide (compounds 3 and 5). The antiproliferative activities of compounds 3 and 5 are in the micromolar range, much higher than the one of thalidomide. A minor antiviral activity against cytomegalovirus and varicella-zoster virus was found for compounds 3 and 5, but these compounds lacked selectivity. The results presented are important for the rational design of the next-generation compounds with anticancer and antiviral activities.

TNFα inhibitors as targets for protective therapies in MSA: a viewpoint

Multiple system atrophy (MSA) is a unique and fatal α-synucleinopathy associated with oligodendroglial inclusions and secondary neurodegeneration affecting striatum, substantia nigra, pons, and cerebellum. The pathogenesis remains elusive; however, there is emerging evidence suggesting a prominent role of neuroinflammation. Here, we critically review the relationship between αS and microglial activation depending on its aggregation state and its role in neuroinflammation to explore the potential of TNFα inhibitors as a treatment strategy for MSA and other neurodegenerative diseases.

Neuropharmacological Screening of Chiral and Non-chiral Phthalimide- Containing Compounds in Mice: in vivo and in silico Experiments

Background:

Thalidomide, the first synthesized phthalimide, has demonstrated sedative- hypnotic and antiepileptic effects on the central nervous system. N-substituted phthalimides have an interesting chemical structure that confers important biological properties.

Objective:

Non-chiral (ortho and para bis-isoindoline-1,3-dione, phthaloylglycine) and chiral phthalimides (N-substituted with aspartate or glutamate) were synthesized and the sedative, anxiolytic and anticonvulsant effects were tested.

Method:

Homology modeling and molecular docking were employed to predict recognition of the analogues by hNMDA and mGlu receptors. The neuropharmacological activity was tested with the open field test and elevated plus maze (EPM). The compounds were tested in mouse models of acute convulsions induced either by pentylenetetrazol (PTZ; 90 mg/kg) or 4-aminopyridine (4-AP; 10 mg/kg).

Results:

The ortho and para non-chiral compounds at 562.3 and 316 mg/kg, respectively, decreased locomotor activity. Contrarily, the chiral compounds produced excitatory effects. Increased locomotor activity was found with S-TGLU and R-TGLU at 100, 316 and 562.3 mg/kg, and S-TASP at 316 and 562.3 mg/kg. These molecules showed no activity in the EPM test or PTZ model. In the 4-AP model, however, S-TGLU (237.1, 316 and 421.7 mg/kg) as well as S-TASP and R-TASP (316 mg/kg) lowered the convulsive and death rate.

Conclusion:

The chiral compounds exhibited a non-competitive NMDAR antagonist profile and the non-chiral molecules possessed selective sedative properties. The NMDAR exhibited stereoselectivity for S-TGLU while it is not a preference for the aspartic derivatives. The results appear to be supported by the in silico studies, which evidenced a high affinity of phthalimides for the hNMDAR and mGluR type 1.

2-Phthalimidethanol and 2-phthalimidethyl nitrate inhibit mechanical allodynia, neutrophil recruitment and cytokine and chemokine production in a murine model of articular inflammation

BACKGROUND

Phthalimide analogs have been shown to exhibit anti-inflammatory, analgesic and immunomodulatory activities in different preclinical assays. This study aimed to investigate the potential role of 2-phthalimidethanol (PTD-OH) and 2-phthalimidethyl nitrate (PTD-NO) in a murine model of antigen-induced articular inflammation.

METHODS

Articular inflammation was induced by intra-articular injection of methylated bovine serum albumin (mBSA) in the knee joint of immunized male C57BL/6J mice. The animals were pre-treated with PTD-OH or PTD-NO (500mg/kg, per os, - 1h). Nociceptive threshold was measured using an electronic von Frey apparatus. The total number of leukocytes in the synovial cavity was determined. Concentrations of tumor necrosis factor (TNF)-α and CXCL-1 and myeloperoxidase (MPO) activity were determined in periarticular tissue.

RESULTS

Both PTD-OH and PTD-NO inhibited at similar extent the mechanical allodynia, neutrophil recruitment to the synovial cavity and periarticular tissue and TNF-α and CXCL-1 production induced by intra-articular challenge with mBSA in immunized mice.

CONCLUSIONS

PTD-OH and PTD-NO exhibit a marked activity in a murine model of antigen-induced articular inflammation in immunized animals. These results reinforce the interest in the investigation of phthalimide analogs devoid of the glutarimide ring as candidates to analgesic and anti-inflammatory drugs.

Model of complex chiral drug metabolic systems and numerical simulation of the remaining chirality toward analysis of dynamical pharmacological activity

In this study, systems of complicated pathways involved in chiral drug metabolism were investigated. The development of chiral drugs resulted in significant improvement in the remedies available for the treatment of various severe sicknesses. Enantiopure drugs undergo various biological transformations that involve chiral inversion and thus result in the generation of multiple enantiomeric metabolites. Identification of the specific active substances determining a given drug׳s efficacy among such a mixture of different metabolites remains a challenge. To comprehend this complexity, we constructed a mathematical model representing the complicated metabolic pathways simultaneously involving chiral inversion. Moreover, this model is applied to the metabolism of thalidomide, which has recently been revived as a potentially effective prescription drug for a number of intractable diseases. The numerical simulation results indicate that retained chirality in the metabolites reflects the original chirality of the unmetabolized drug, and a higher level of enantiomeric purity is preserved during spontaneous degradation. In addition, chirality remaining after equilibration is directly related to the rate constant not only for chiral inversion but also for generation and degradation. Furthermore, the retention of chirality is quantitatively predictable using this combination of kinetic parameters. Our simulation results well explain the behavior of thalidomide in the practical biological experimental data. Therefore, this model promises a comprehensive understanding of dynamic metabolic systems involving chiral drugs that express multiple enantiospecific drug efficacies.

Activities of 2-phthalimidethyl nitrate and 2-phthalimidethanol in the models of nociceptive response and edema induced by formaldehyde in mice and preliminary investigation of the underlying mechanisms

The activities of 2-phthalimidethyl nitrate (PTD-NO) and 2-phthalimidethanol (PTD-OH) were recently demonstrated in models of pain and inflammation. We expanded our investigation by evaluating their activities in models of nociceptive and inflammatory pain and inflammatory edema, the preliminary pharmacokinetic parameter for PTD-NO and the role of opioid and cannabinoid pathways in the activity of analogs. Per os (p.o.) administration of PTD-NO or PTD-OH, 1h before intraplantar injection of formaldehyde, inhibited both phases of the nociceptive response (500 and 750 mg/kg) and paw edema (125, 250, 500 and 750 mg/kg). After p.o. administration of PTD-NO, peak plasma concentrations of PTD-NO and PTD-OH were found 0.92 and 1.13 h, respectively. The plasma concentrations of PTD-NO were higher than those of PTD-OH. Intraperitoneal (i.p.) administration of CB1 (AM251) or CB2 (AM630) cannabinoid receptor antagonists (4 or 8 mg/kg, -30 min) or opioid antagonist naltrexone (5 or 10mg/kg, -30 min) did not affect the antinociceptive activities of the analogs. AM251 (8 mg/kg, i.p., -30 min) attenuated the antiedematogenic activity of both analogs, while naltrexone (10mg/kg, i.p., -30 min) only attenuated the antiedematogenic activity of PTD-NO. The antiedematogenic activities of both analogs were not affected by the CB2 cannabinoid antagonist AM630 (4 or 8 mg/kg, i.p., -30 min). Concluding, we expanded the knowledge on the activities of PTD-NO and PTD-OH by showing that these phthalimide analogs also exhibit marked activity in models of nociceptive and inflammatory pain and inflammatory edema. Opioid and cannabinoid mechanisms partially mediate the anti-inflammatory, but not the antinociceptive activity.

Discovery and structure-activity relationship studies of N6-benzoyladenine derivatives as novel BRD4 inhibitors

Bromodomain and extra-terminal domain (BET) proteins are epigenetic readers that bind to acetylated lysines in histones. Among them, BRD4 is a candidate target molecule of therapeutic agents for diverse diseases, including cancer and inflammatory disease. As a part of our continuing structural development studies of thalidomide to obtain a broad spectrum of biological modifiers based on the 'multi-template' approach, in this work we focused on BRD4-inhibitory activity, and discovered that N6-benzoyladenine derivatives exhibit this activity. Structure-activity relationship studies led to N6-(2,4,5-trimethoxybenzoyl)adenine (29), which exhibits potent BRD4 bromodomain1 inhibitory activity with an IC50 value of 0.427μM. N6-Benzoyladenine appears to be a new chemical scaffold for development of BRD4 inhibitors.

Identification of a promising PI3K inhibitor for the treatment of multiple myeloma through the structural optimization

BACKGROUND

We previously reported a PI3K inhibitor S14161 which displays a promising preclinical activity against multiple myeloma (MM) and leukemia, but the chiral structure and poor solubility prevent its further application.

METHODS

Six S14161 analogs were designed based on the structure-activity relationship; activity of the compounds in terms of cell death and inhibition of PI3K were analyzed by flow cytometry and Western blotting, respectively; anti-myeloma activity in vivo was performed on two independent xenograft models.

RESULTS

Among the six analogs, BENC-511 was one of the most potent compounds which significantly inhibited PI3K activity and induced MM cell apoptosis. BENC-511 was able to inactivate PI3K and its downstream signals AKT, mTOR, p70S6K, and 4E-BP1 at 1 μM but had no effects on their total protein expression. Consistent with its effects on PI3K activity, BENC-511 induced MM cell apoptosis which was evidenced by the cleavage of Caspase-3 and PARP. Notably, addition of insulin-like growth factor 1 and interleukin-6, two important triggers for PI3K activation in MM cells, partly blocked BENC-511-induced MM cell death, which further demonstrated that PI3K signaling pathway was critical for the anti-myeloma activity of BENC-511. Moreover, BENC-511 also showed potent oral activity against myeloma in vivo. Oral administration of BENC-511 decreased tumor growth up to 80% within 3 weeks in two independent MM xenograft models at a dose of 50 mg/kg body weight, but presented minimal toxicity. Suppression of BENC-511 on MM tumor growth was associated with decreased PI3K/AKT activity and increased cell apoptosis.

CONCLUSIONS

Because of its potent anti-MM activity, low toxicity (LD50 oral >1.5 g/kg), and easy synthesis, BENC-511 could be developed as a promising agent for the treatment of MM via suppressing the PI3K/AKT signaling pathway.

Recent approaches to medicinal chemistry and therapeutic potential of dipeptidyl peptidase-4 (DPP-4) inhibitors

Dipeptidyl peptidase-4 (DPP-4) is one of the widely explored novel targets for Type 2 diabetes mellitus (T2DM) currently. Research has been focused on the strategy to preserve the endogenous glucagon like peptide (GLP)-1 activity by inhibiting the DPP-4 action. The DPP-4 inhibitors are weight neutral, well tolerated and give better glycaemic control over a longer duration of time compared to existing conventional therapies. The journey of DPP-4 inhibitors in the market started from the launch of sitagliptin in 2006 to latest drug teneligliptin in 2012. This review is mainly focusing on the recent medicinal aspects and advancements in the designing of DPP-4 inhibitors with the therapeutic potential of DPP-4 as a target to convey more clarity in the diffused data.

Evaluation of the anti-Schistosoma mansoni activity of thiosemicarbazones and thiazoles

Schistosomiasis is a chronic and debilitating disease caused by a trematode of the genus Schistosoma and affects over 207 million people. Chemotherapy is the only immediate recourse for minimizing the prevalence of this disease and involves predominately the administration of a single drug, praziquantel (PZQ). Although PZQ has proven efficacy, there is a recognized need to develop new drugs as schistosomicides since studies have shown that repeated use of this drug in areas of endemicity may cause a temporary reduction in susceptibility in isolates of Schistosoma mansoni. Hydrazones, thiosemicarbazones, phthalimides, and thiazoles are thus regarded as privileged structures used for a broad spectrum of activities and are potential candidates for sources of new drug prototypes. The present study determined the in vitro schistosomicidal activity of 10 molecules containing these structures. During the assays, parameters such motility and mortality, oviposition, morphological changes in the tegument, cytotoxicity, and immunomodulatory activity caused by these compounds were evaluated. The results showed that compounds formed of thiazole and phthalimide led to higher mortality of worms, with a significant decline in motility, inhibition of pairing and oviposition, and a mortality rate of 100% starting from 144 h of exposure. These compounds also stimulated the production of nitric oxide and tumor necrosis factor alpha (TNF-α), thereby demonstrating the presence of immunomodulatory activity. The phthalyl thiazole LpQM-45 caused significant ultrastructural alterations, with destruction of the tegument in both male and female worms. According to the present study, phthalyl thiazole compounds possess antischistosomal activities and should form the basis for future experimental and clinical trials.

Structure-activity relationship studies of thalidomide analogs with a taxol-like mode of action

Anti-microtubule agents such as paclitaxel and docetaxel have played an important role in the treatment of cancer for many years. Recently, a small molecule that has a taxol-like mode of action (5HPP-33) was reported. Herein, the detailed structure-activity relationship (SAR) studies of 5HPP-33 analogs that are substituted at the isoindole and phenyl rings are described. Bulky substitutions (such as di-isopropyl groups) on the phenyl ring result in the isoindole and phenyl rings being perpendicular to each other. It was found that this conformation is critical for anti-microtubule activity. These studies have provided valuable information, which will be helpful in the design of more potent analogs.

A novel aromatic carboxylic acid inactivates luciferase by acylation of an enzymatically active regulatory lysine residue

Firefly luciferase (Luc) is widely used as a reporter enzyme in cell-based assays for gene expression. A novel aromatic carboxylic acid, F-53, reported here for the first time, substantially inhibited the enzymatic activity of Luc in a Luc reporter screening. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and tandem mass spectrometry (MS/MS) analyses showed that F-53 modifies Luc at lysine-529 via amidation of the F-53 carboxyl group. The lysine-529 residue of Luc, which plays a regulatory catalytic role, can be acetylated. Luc also has a long-chain fatty acyl-CoA synthase activity. An in vitro assay that involved both recombinant Luc and mouse liver microsomes identified F-53-CoA as the reactive form produced from F-53. However, whereas the inhibitory effect of F-53 is observed in Hela cells that transiently expressed Luc, it is not observed in an in vitro assay that involves recombinant Luc alone. Therefore, insights into the activities of certain mammalian transferases can be translated to better understand the acylation by F-53. The insights from this study about the novel inhibitory modification mechanism might help not only to avoid misinterpretation of the results of Luc-based reporter screening assays but also to explain the pharmacological and toxicological effects of carboxylic acid-containing drugs.

Synthesis and pharmacological evaluation of novel phenyl sulfonamide derivatives designed as modulators of pulmonary inflammatory response

In this paper we report the design, synthesis and pharmacological evaluation of a new series of phenyl sulfonamide derivatives 2a–h and 3–8 planned by structural modification on the anti-inflammatory prototype LASSBio-468 (1). Among the synthesized analogues, the tetrafluorophthalimide LASSBio-1439 (2e) stands out showing an in vitro anti-TNF-α effect similar to the standard thalidomide. The relevance of tetrafluorination of the phthalimide nucleus was also confirmed by the anti-inflammatory profile of 2e, through oral administration, in a murine model of pulmonary inflammation. The corresponding tetrafluorocarboxyamide metabolite LASSBio-1454 (15), generated from partial hydrolysis of the derivative 2e, presented a significant in vitro effect and a pronounced anti-inflammatory activity in vivo.

Therapeutic approaches for tumor necrosis factor inhibition

Tumor necrosis factor (TNF) consists of an inflammatory cytokine essential for homeostasis and organism defense. Despite its physiological relevance, both increased biosynthesis and release of TNF lead to the exacerbation of inflammatory and oxidative responses, which are related to the pathogenesis of a host of diseases of an inflammatory, autoimmune and/or infectious nature. In this context, effective therapeutic approaches for the modulation of TNF have been the focus of research efforts. Approximately one million individuals worldwide have been treated with biotechnological inhibitors of this cytokine, the so-called anti-TNF biopharmaceuticals. However, given the high risk of infection and the limitations related to cost and administration routes, new therapeutic approaches aimed at biological targets that directly or indirectly modulate the production and/or activation of TNF appear promising alternatives for the discovery of new anti-inflammatory and immunomodulatory orally active drugs and are therefore discussed in this paper.

Synthesis, anti-inflammatory activity and COX-1/COX-2 inhibition of novel substituted cyclic imides. Part 1: Molecular docking study

A group of cyclic imides (1-13) was designed for evaluation as selective COX-2 inhibitors and investigated in vivo for their anti-inflammatory activities using carrageenan-induced rat paw edema model. Compounds 5b, 6b, 11b, 11c, 12b and 12c were proved to be potent COX-2 inhibitors with IC50 range of 0.1-1.0 μM. In vitro COX-1/COX-2 inhibition structure-activity studies identified compound 5b as a highly potent (IC50=0.1 μM), and an extremely selective [COX-2 (SI)=400] comparable to celecoxib [COX-2 (SI)>333.3], COX-2 inhibitor that showed superior anti-inflammatory activity (ED50=104 mg/kg) relative to diclofenac (ED50=114 mg/kg). A Virtual screening was carried out through docking the designed compounds into the COX-2 binding site to predict if these compounds have analogous binding mode to the COX-2 inhibitors. Molecular modeling (docking) study showed that the CH3O substituents of 5b inserted deep inside the 2°-pocket of the COX-2 active site, where the O-atoms of such group underwent a H-bonding interaction with His90 (2.43, 2.83 Å), Arg513 (2.89 Å) and Tyr355 (3.34 Å). Docking study of the synthesized compound 5b into the active site of COX-2 revealed a similar binding mode to SC-558, a selective COX-2 inhibitor.

Development of tryptase inhibitors derived from thalidomide

A novel series of tryptase inhibitors with a N-phenylphthalimide skeleton structurally derived from thalidomide (1) has been developed. Structure-activity relationship studies led to a potent and selective tryptase inhibitor, 2-(4-cyanophenyl)isoindole-1,3-dione-5-yl 3-(2-aminopyridin-5-yl)propanoate (7), with the IC50 value of 78 nM.

Anti-influenza activity of phenethylphenylphthalimide analogs derived from thalidomide

Swine-origin influenza A virus has caused pandemics throughout the world and influenza A is regarded as a serious global health issue. Hence, novel drugs that will target these viruses are very desirable. Influenza A expresses an RNA polymerase essential for its transcription and replication which comprises PA, PB1, and PB2 subunits. We identified potential novel anti-influenza agents from a screen of 34 synthesized phenethylphenylphthalimide analogs derived from thalidomide (PPT analogs). For this screen we used a PA endonuclease inhibition assay, a PB2 pathogenicity-determinant domain-binding assay, and an anti-influenza A virus assay. Three PPT analogs, PPT-65, PPT-66, and PPT-67, were found to both inhibit PA endonuclease activity and retard the growth of influenza A, suggesting a correlation between their activities. PPT-28 was also found to inhibit the growth of influenza A. These four analogs have a 3,4-dihydroxyphenethyl group in common. We also discuss the possibility that 3,4-dihydroxyphenethyl group flexibility may play an important functional role in PA endonuclease inhibition. Another analog harboring a dimethoxyphenethyl group, PPT-62, showed PB2 pathogenicity-determinant domain-binding activity, but did not inhibit the growth of the virus. Our present results indicate the utility of the PA endonuclease assay in the screening of anti-influenza drugs and are therefore useful for future strategies to develop novel anti-influenza A drugs and for mapping the function of the influenza A RNA polymerase subunits.

Effects of immunomodulatory derivatives of thalidomide (IMiDs) and their analogs on cell-differentiation, cyclooxygenase activity and angiogenesis

Various analogs of known immunomodulatory derivatives of thalidomide (1) (IMiDs: 3, 5) were synthesized, focusing on cell-differentiation-inducing, cyclooxygenase-inhibitory and anti-angiogenesis activities. Among the prepared compounds, NIDO-33 (14) showed cell differentiation-inducing activity on HL-60 cells and anti-angiogenic activity on human umbilical vein endothelial cells (HUVEC). AIDO-00 (7) also showed anti-angiogenic activity. NIDO-11 (8) showed an enhancing effect on all-trans retinoic acid (ATRA)-induced HL-60 cell differentiation, and AIDO-30 (13) exhibited cyclooxygenase (COX)-inhibitory activity.

Synthesis of 3-N-sugar-substituted-2, 4(1H,3H)-quinazolinedionesas anti-angiogenesis agents

A series of novel 3-N-sugar-substituted quinazolinediones were synthesized through the cyclization of the intermediate 2-aminobenzamides using triphosgene as the condensing reagent. Their anti-angiogenesis activities were investigated. The compound 3-(2'-aminoglucosyl)-2,4-(1H,3H)-quinazolinedione, (5d) showed good anti-angiogenesis activity.

Separation of alpha-glucosidase-inhibitory and liver X receptor-antagonistic activities of phenethylphenyl phthalimide analogs and generation of LXRalpha-selective antagonists

Liver X receptor (LXR) alpha/beta dual agonists are candidate medicaments for the treatment of metabolic syndrome, because their biological actions include increasing cholesterol efflux mediated by LXRbeta. However, their clinical application is currently limited by their enhancing effect on triglyceride (TG) synthesis mediated by LXRalpha. Combination of an LXRalpha-selective antagonist with an LXRalpha/beta dual agonist may overcome this disadvantage. In the present work, structural development studies of phenethylphenyl phthalimide 9, which possesses LXRalpha/beta dual-antagonistic activity and alpha-glucosidase-inhibitory activity, led to the LXRalpha-selective antagonist 23f. Specific alpha-glucosidase inhibitors were also obtained.