Approaches Towards Better Immunosuppressive Agents.

Several classes of compounds are applied in clinics due to their immunosuppressive properties in transplantology and the treatment of autoimmune diseases. Derivatives of mycophenolic acid, corticosteroids and chemotherapeutics bearing heterocyclic moieties like methotrexate, azathioprine, mizoribine, and ruxolitinib are active substances with investigated mechanisms of action. However, improved synthetic approaches of known drugs and novel derivatives are still being reported to attempt better accessibility and therapeutic properties. In this review article, we present the synthesis of the designed chemical structures based on recent literature reports concerning novel compounds as promising immunosuppressive drugs. Moreover, some of the discussed derivers revealed also other types of activities with prospective medicinal potential.

Novel amides of mycophenolic acid and some heterocyclic derivatives as immunosuppressive agents.

The group of 18 new amide derivatives of mycophenolic acid (MPA) and selected heterocyclic amines was synthesised as potential immunosuppressive agents functioning as inosine-5'-monophosphate dehydrogenase (IMPDH) uncompetitive inhibitors. The synthesis of 14 of them employed uronium-type activating system (TBTU/HOBt/DIPEA) while 4 of them concerned phosphonic acid anhydride method (T3P/Py) facilitating amides to be obtained in moderate to excellent yields without the need of phenolic group protection. Most of optimised protocols did not require complicated reaction work-ups, including chromatographic, solvent-consuming methods. The biological activity assay was performed on the T-Jurkat cell line and peripheral mononuclear blood cells (PBMCs) which are both dedicated for antiproliferative activity determination. Each of designed derivatives was characterised by reduced cytotoxicity and benzoxazole analogue (A2) revealed the most promising activity. Subsequently, an observed structure-activity relationship was discussed.

Anticancer Properties of Amino Acid and Peptide Derivatives of Mycophenolic Acid.

BACKGROUND: Although Mycophenolic Acid (MPA) is applied as prodrugs in clinic as an immunosuppressant, it also possesses anticancer activity. MPA acts as Inosine-5'-Monophosphate Dehydrogenase (IMPDH) inhibitor, where the carboxylic group at the end of the side chain interacts with Ser 276 of the enzyme via hydrogen bonds. Therefore, MPA derivatives with other polar groups indicated high inhibition too. On the other hand, potent anticancer agents like dacarbazine and cisplatin give numerous side-effects. OBJECTIVE: Based on the literature data, MPA derivatives should be explored towards anticancer properties. Conversion of the carboxylic group of MPA to amide could maintain antiproliferative activity. Therefore, we decided to investigate several amino acid and peptide derivatives of MPA against chosen cancer cell lines in vitro. METHODS: Amides of MPA hold threonine and arginine amino acid unit. These amino acid derivatives were tested as L and D enantiomers and both in free acid and methyl esters forms. Additionally, MPA was modified with tuftsin or retro-tuftsin as biologically active peptides, which could act as a drug carrier. RESULTS: Amino acid and peptide derivatives of MPA were investigated in vitro as potential anticancer agents on cell lines: Ab melanoma, A375 melanoma and SHSY5Y neuroblastoma. The activity of the tested compounds was compared to parent MPA and known chemotherapeutics: dacarbazine and cisplatin. CONCLUSION: Amino acid moiety and the sequence of amino acids in the peptide part influenced observed activity. The most active amino acid MPA analogues occurred to be D and L-threonine derivatives as methyl esters, probably due to better cell membrane penetration.

Immunosuppressive properties of amino acid and peptide derivatives of mycophenolic acid.

Mycophenolic acid (MPA) was coupled with amino acids and biologically active peptides including derivatives of tuftsin to modify its immunosuppressive properties. Both amino acid unit in the case of simple MPA amides and modifications within peptide moiety of MPA - tuftsin conjugates influenced the observed activity. Antiproliferative potential of the obtained conjugates was investigated in vitro and MPA amides with threonine methyl ester and conjugate of MPA with retro-tuftisin occurred to be more selective against PBMC in comparison to parent MPA. Both amino acid and peptide derivatives of MPA acted as inosine-5'-monophosphate dehydrogenaze (IMPDH) inhibitors.

Synthesis and antiproliferative activity of new mycophenolic acid conjugates with adenosine derivatives.

New conjugates of mycophenolic acid (MPA) and adenosine derivatives were synthesized and assessed as potential immunosuppressants on Jurkat cell line and peripheral blood mononuclear cells (PBMC) from healthy donors. As compared to MPA, all compounds were found to be more active against Jurkat cell line. The antiproliferative activities were compared with MPA and adenosine, in both 2',3'-O-isopropylidene protected and free hydroxyl groups possessing forms. The obtained results were also discussed in terms of selectivity index, defined as SI = IC50/EC50.

Synthesis and antimicrobial activity of amino acid and peptide derivatives of mycophenolic acid.

The series of 16 novel amino acid and peptide mycophenolic acid (MPA) derivatives was obtained as potential antibacterial agents. Coupling of MPA with respective amines was optimized with condensing reagents such as EDCI/DMAP and T3P/TEA. Amino acid analogs were received both as methyl esters and also with the free carboxylic group. The biological activity of the products was tested on five references bacterial strains: Klebsiella pneumoniae ATCC 700603 (ESBL), Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus MRSA ATCC 43300, Staphylococcus aureus MSSA ATCC 25923. Peptide derivatives proved to be the most versatile ones, their MIC values relative to most strains was lower than MPA alone. It has been noted that the activity of amino acid derivatives depends on the configuration at the chiral center in the amino acid unit and methyl esters indicated better antimicrobial activity than analogs with free carboxylic group.

Tuftsin - Properties and Analogs.

BACKGROUND: Immunomodulation is one of the significant therapeutic strategies. It includes both stimulation and suppression of the immune system by a variety of substances called immunomodulators, designed to regulate the immune response of the organism against infections of varying etiology. An example of such a substance is tuftsin (TKPA) 3 (Fig. (1)). In this paper were included tuftsin derivatives, which were described over the years, their together with biological activity and clinical potential. METHODS: We reviewed a bibliographic database to gather all the important information about the tuftsin peptide. We have delineated the significant information on the activity of the tetrapeptide itself and its derivatives. Analogs were divided because of their anti-tumor, anti-inflammatory, antimicrobial and anti-viral activity. RESULTS: This paper describes eighty-six documents. Thirty-two of them concern on activity of tuftsin in the human organism. The remaining fifty-four describe peptide analogues and their properties, including eleven papers about the tuftsin-based peptides contained in the vaccines, nine papers representing anticancer activity of the tuftsin derivatives, twenty-six about antiinflammatory compounds, and five papers describing the antitumor activity of the tuftsin analogs. CONCLUSION: The findings of this review confirm the importance of the tuftsin and their derivatives. Most of these substances showed anti-tumor, anti-inflammatory or antibacterial activities. A large amount of the compounds may find use in vaccines. Tuftsin can also be used to prepare fusion proteins in the treatment of cancer and as carriers of many biologically active substances.

Investigations on the immunosuppressive activity of derivatives of mycophenolic acid in immature dendritic cells.

The main activity of mycophenolic acid 1 (MPA) and its analogs is the inhibition of proliferation of T cells. Here, we hypothesized that MPA and its conjugates inhibits also the activity of antigen-presenting cells (APC) including dendritic cells (DCs). We tested the effect of novel amino acid derivatives of MPA and conjugates of MPA with acridines/acridones on DCs by flow cytometry, ELISA and MLR assay. Both acridines/acridone derivatives could inhibit the maturation of DC, as shown by the decreased expression of B7 family receptors. It was confirmed in the mixed leucocyte reaction (MLR), in which T cells challenged with DCs pretreated with the analogs showed decreased proliferation and reduced cytokine secretion. The most interesting activity in this series of studies, that is, the suppression of CD86 receptor expression, decreased cytokine production and suppressed mixed leucocyte reaction, exhibited (mycophenoyl-N-3-propyl)-9-acridone-4-carboxamide ester 5a and (mycophenoyl-N-5-pentyl)-9-acridone-4-carboxamide ester 5b. These compounds reduced also the secretion of IL-2 and IL-15. In addition, they increased secretion of suppressive IL-10. Equally promising results were obtained for the N-mycophenoyl-D-glutamic acid 4b, which previously gave the highest value of selectivity. Acridone derivatives of MPA are therefore good immunosuppressive drug candidates for further testing.

New Analogues of Mycophenolic Acid.

BACKGROUND: Mycophenolic acid (MPA) possesses antibacterial, antifungal, antiviral, immunosuppressive and anticancer properties. It is a non-competitive and reversible inhibitor of dehydrogenase inosine-5'-monophosphate (IMPDH). This compound belongs to the immunosuppressive drugs used for the prevention of both acute and chronic transplant rejection. Until now, two derivatives of MPA have been used clinically: mycophenolate mofetil (MMF, CellCept) and mycophenolate sodium (MPS, Myfortic). They cause, similar to MPA, although at lower degree, the side effects such as vomiting, abdominal pain, diarrhea, nausea, gastrointestinal, urogenital tract, blood or nervous system disorders. These drawbacks and glucuronidation of MPA in vivo limit the use of these compounds as pharmaceuticals. Therefore, research is still going on for more effective analogs that are less toxic to the organism and could improve the quality of life of patients. CONCLUSION: In this review article, the authors present the synthesis of novel derivatives of mycophenolic acid, together with their initial biological investigations.

New conjugates of mycophenolic acid and their antiproliferative activity.

The new conjugates of mycophenolic acid (MPA) were obtained in the reaction of N(6)-(ω-aminoalkyl)adenosines with MPA in the presence of EDCI as a coupling reagent. New compounds 4a-h were evaluated on leukemia cell line (Jurkat) and PBMC from healthy donors. Length of the linker influenced observed activity. The compound 4b possessing 1,3-diamine spacer exhibited the most promising results and can be considered to further investigations.

Synthesis of Combretastatin A-4 Analogs and their Biological Activities.

Combretastatin A-4 (CA-4) is a natural product, which consists of two phenyl rings, linked by an ethylene bridge. CA-4, inhibitor of polymerization of tubulin to microtubules, possesses a strong antitumor and anti-vascular properties both in vitro and in vivo. Previous studies showed that disodium phosphate salt of CA-4, a water-soluble prodrug is well tolerated at therapeutically useful doses. However, it should be noted that the cis-configuration of the double bond and the 3,4,5-trimethoxy group on ring A is necessary for the biological activity of CA-4. Structure of CA-4 renders the compound readily susceptible to isomerization, which reduces the potency and bioavailability. To circumvent this problem, a lot of scientists in the world synthesized a series of cis-restricted CA-4 analogs, where the double bond has been replaced by introduction of non-heterocyclic groups or heterocyclic groups like ß -lactam and oxadiazole. This paper reviews the most important approaches in analogs of combretastatin synthesis and presents structure-reactivity relationships for these compounds.

Synthesis and biological activity of ester derivatives of mycophenolic acid and acridines/acridones as potential immunosuppressive agents.

Improved derivatives of mycophenolic acid (MPA) are necessary to reduce the frequency of adverse effects, this drug exerts in treated patients. In this study, MPA was coupled with N-(ω-hydroxyalkyl)-9-acridone-4-carboxamides or N-(ω-hydroxyalkyl)acridine-4-carboxamides to give respective ester conjugates upon Yamaguchi protocol. This esterification required protection of phenol group in MPA. Designed conjugates revealed higher potency in vitro than parent MPA. Acridine derivatives were more active than acridone analogs and length of the alkyl linker between MPA and heterocyclic units influenced the observed cytotoxicity. Derivatives 2b, 2d, 3a, 3b displayed the most promising immunosuppressive activity.

Synthesis of functionalized new conjugates of batracylin with tuftsin/retro-tuftsin derivatives and their biological evaluation.

New batracylin conjugates with tuftsin/retro-tuftsin derivatives were designed and synthesized using T3P as a coupling agent. The conjugates possess an amide bond formed between the carboxyl group of heterocyclic molecule and the N-termini of the tuftsin/retro-tuftsin chain. The in vitro cytotoxic activity of the new analogues and their precursors was evaluated using a series of human and murine tumor cells. BAT conjugates containing retro-tuftsin with branched side aminoacid chain, in particular with leucine or isoleucine, were about 10-fold more cytotoxic toward two human tumor cell lines (lung adenocarcinoma (A549) and myeloblastic leukemia (HL-60)). These compounds showed about 10-fold increased cytotoxicity against the two types of tumor cells compared to parent BAT. We have not observed important differences in the mechanism of action between BAT and its cytotoxic tuftsin/retro-tuftsin conjugates. We propose that high biological activity of the most active BAT conjugates is a result of their greatly increased intracellular accumulation.

Inhibitors of Angiogenesis in Cancer Therapy - Synthesis and Biological Activity.

Angiogenesis is the process of formation of new capillaries from preexisting blood vessels. Angiogenesis is involved in normal physiological processes, and plays an important role in tumor invasion and development of metastases. Vascular endothelial growth factor (VEGF) plays a key role in angiogenesis. VEGF is a mitogen for vascular endothelial cells and stimulates their proliferation. By inhibiting the biological activity of VEGF, and then signal cascades with neutralizing VEGF antibodies and signal inhibitors, may negatively regulate the growth and metastasis. Anti-angiogenesis therapy is less toxic than chemotherapy. Angiogenesis is a multistep and multifactorial process, and therefore, can be blocked at different levels. In this review article, the authors present the synthesis of novel inhibitors of angiogenesis, together with the results of biological tests in vitro, and in some cases, state trials.

Synthesis of the inosine 5'-monophosphate dehydrogenase (IMPDH) inhibitors.

Inosine 5'-monophosphate dehydrogenase (IMPDH) is important molecular target for potential anticancer, antiviral, antibacterial and immunosuppressive agents. A lot of compounds were obtained to establish their activity toward this enzyme, and to improve therapeutic properties of IMPDH inhibitors used as the drugs. Some of the recently reported analogs exhibited promising results during in vitro and in vivo examinations in comparison to substances applied in clinic. In this review, we describe synthesis and biological activity evaluations of the newly designed IMPDH inhibitors.

Synthesis and biological activity of mycophenolic acid-amino acid derivatives.

In search of new immunosuppressants we synthesized 11 amino acids derivatives of MPA as methyl esters 10a-k using EDCI/DMAP and their corresponding amino acid derivatives in free acid form 11a-k by hydrolysis of ester group with LiOH/MeOH. New analogs were evaluated as growth inhibitors of lymphoid cell line (Jurkat) and human peripheral blood mononuclear cells (PBMC) from healthy donors. According to obtained results recovering of free carboxylic group increased their activity. Additionally, the cytotoxic properties depends on the substituent and configuration at chiral center in amino acid unit. The compounds 10j, 11e and 11h exhibited higher potency than MPA 1 in vitro.

Synthesis and biological activity of novel mycophenolic acid conjugates containing nitro-acridine/acridone derivatives.

Hybrid pharmacophore anti-proliferative compounds, comprised of mycophenolic acid (MPA) and 1-nitroacridine/4-nitroacridone derivative have been synthesized and evaluated as inhibitors of five different leukemia cell lines (Jurkat, Molt-4, HL-60, CCRF-CEM, L1210) and human peripheral blood mononuclear cells from healthy donors. These conjugates possess different length of the linker between MPA and heterocyclic units. The type of heterocyclic part influenced their cytotoxic and anti-proliferative properties. Coupling of MPA 1 with 9-(ω-aminoalkyl)amino-1-nitroacridines 2 and 1-[(ω-aminoalkyl)-4-nitro-9(10H)]-acridones 3 was tested. Although all tested conjugates were active, compounds 4a-e exhibited the highest potency. Preliminary experiments with GMP suggested that the tested compounds acted as IMPDH inhibitors.

4-[(tert-Butyl-dimethyl-sil-yl)-oxy]-6-meth-oxy-7-methyl-5-(oxiran-2-ylmeth-yl)-2-benzofuran-3(1H)-one.

The title compound, C(19)H(28)O(5)Si, was obtained in the reaction of 1,3-dihydro-4-[(tert-butyl-dimethyl-sil-yl)-oxy]-6-meth-oxy-7-methyl-3-oxo-5-(prop-2-en-yl)isobenzofuran with meta-chloro-perbenzoic acid. This reaction is one of the stages of the total synthesis of mycophenolic acid, which we attempted to modify. The title compound forms crystals with only weak inter-molecular inter-actions. The strongest stacking inter-action is found between the benzene and furan rings of inversion-related mol-ecules with a distance of 3.8773 (13) Šbetween the ring centroids.

Natural and synthetic acridines/acridones as antitumor agents: their biological activities and methods of synthesis.

Acridine derivatives constitute a class of compounds that are being intensively studied as potential anticancer drugs. Acridines are well-known for their high cytotoxic activity; however, their clinical application is limited or even excluded because of side effects. Numerous synthetic methods are focused on the preparation of target acridine skeletons or modifications of naturally occurring compounds, such as acridone alkaloids, that exhibit promising anticancer activities. They have been examined in vitro and in vivo to test their importance for cancer treatment and to establish the mechanism of action at both the molecular and cellular level, which is necessary for the optimization of their properties so that they are suitable in chemotherapy. In this article, we review natural and synthetic acridine/acridone analogs, their application as anticancer drugs and methods for their preparation.