Synthesis and formulation studies of griseofulvin analogues with improved solubility and metabolic stability

Griseofulvin (1) is an important antifungal agent that has recently received attention due to its antiproliferative activity in mammalian cancer cells. Comprehensive SAR studies have led to the identification of 2'-benzyloxy griseofulvin 2, a more potent analogue with low micromolar anticancer potency in vitro. Analogue 2 was also shown to retard tumor growth through inhibition of centrosomal clustering in murine xenograft models of colon cancer and multiple myeloma. However, similar to griseofulvin, compound 2 exhibited poor metabolic stability and aqueous solubility. In order to improve the poor pharmacokinetic properties, 11 griseofulvin analogues were synthesized and evaluated for biological activity and physiological stabilities including SGF, plasma, and metabolic stability. Finally, the most promising compounds were investigated in respect to thermodynamic solubility and formulation studies. The 2'-benzylamine analogue 10 proved to be the most promising compound with low μM in vitro anticancer potency, a 200-fold increase in PBS solubility over compound 2, and with improved metabolic stability. Furthermore, this analogue proved compatible with formulations suitable for both oral and intravenous administration. Finally, 2'-benzylamine analogue 10 was confirmed to induce G2/M cell cycle arrest in vitro.

A novel pseudo-complementary PNA G-C base pair

Pseudo-complementary oligonucleotide analogues and mimics provide novel opportunities for targeting duplex structures in RNA and DNA. Previously, a pseudo-complementary A-T base pair has been introduced. Towards sequence unrestricted targeting, a pseudo-complementary G-C base pair consisting of the unnatural nucleobases n6-methoxy-2,6-diaminopurine (previously described in a DNA context) and N4-benzoylcytosine is now presented for design of pseudo-complementary PNA oligomers (pcPNAs).

Lixisenatide for the treatment of type 2 diabetes

Lixisenatide (trade name Lyxumia®), a short-acting glucagon-like peptide 1 receptor (GLP-1R) agonist, was approved for the treatment of type 2 diabetes by the European Medicines Agency in early 2013. In preclinical investigations, acceptable toxicity and carcinogenicity profiles were demonstrated, as well as pancreatic beta cell-preserving actions and favorable effects on glycemic control. Following subcutaneous administration in humans, lixisenatide displays linear pharmacokinetics and an absorption-dependent elimination half-life of 2-3 hours. In clinical trials of up to 1 year duration in patients with type 2 diabetes, treatment with lixisenatide alone and in combination with insulin and various oral antidiabetics conferred significant reductions in HbA1c, fasting and postprandial plasma glucose. In direct comparison with the other GLP-1R agonists on the market (exenatide and liraglutide), lixisenatide appears to be less efficient, or at best non-inferior in terms of reducing HbA1c, fasting plasma glucose and body weight. Nevertheless, lixisenatide confers fewer adverse events than the other currently marketed GLP-1R agonists, while exhibiting a clinically valuable effect on postprandial hyperglycemia.

Phylogeny and resistance profiles of HIV-1 POL sequences from rectal biopsies and blood

The phylogeny and resistance profiles of human immunodeficiency virus type 1 (HIV-1) protease (PR) and reverse transcriptase (RT) sequences were compared among six patients with HIV-1 who had received numerous treatments. RNA and DNA fractions were obtained from concurrent blood and rectal biopsy samples. Phylogenetic trees and resistance profiles showed that the rectal mucosa and the peripheral blood mononuclear cells (PBMCs) harbored different HIV-1 strains. The resistance-associated mutations found in each strain corresponded to the treatment history of the patients. The resistance mutations acquired during earlier treatment regimens were detected in the sequences obtained from the rectal samples and in the PBMCs in several of the patients. Also, differences in the resistance profiles were observed between anatomical sites and between RNA and DNA fractions. Thus, a single sample probably will not be representative of the HIV-1 archived in different sites. Both the resistance profile and phylogeny of HIV-1 often differed in sequences obtained from RNA and DNA from the same site. These findings suggest that additional information regarding the antiviral resistance profile of the patient might be obtained by testing different anatomical sites.

Hymenoptera venom allergy: analysis of double positivity to honey bee and Vespula venom by estimation of IgE antibodies to species-specific major allergens Api m1 and Ves v5

BACKGROUND

In patients with hymenoptera venom allergy diagnostic tests are often positive with honey bee and Vespula venom causing problems in selection of venoms for immunotherapy.

METHODS

100 patients each with allergic reactions to Vespula or honey bee stings and positive i.e. skin tests to the respective venom, were analysed for serum IgE to bee venom, Vespula venom and crossreacting carbohydrate determinants (CCDs) by UNICAP (CAP) and ADVIA Centaur (ADVIA). IgE-antibodies to species specific recombinant major allergens (SSMA) Api m1 for bee venom and Ves v5 for Vespula venom, were determined by ADVIA. 30 history and skin test negative patients served as controls.

RESULTS

By CAP sensitivity was 1.0 for bee and 0.91 for Vespula venom, by ADVIA 0.99 for bee and 0.91 for Vespula venom. None of the controls were positive with either test. Double positivity was observed in 59% of allergic patients by CAP, in 32% by ADVIA. slgE to Api m1 was detected in 97% of bee and 17% of Vespula venom allergic patients, slgE to Ves v5 in 87% of Vespula and 17% of bee venom allergic patients. slgE to CCDs were present in 37% of all allergic patients and in 56% of those with double positivity and were more frequent in bee than in Vespula venom allergic patients.

CONCLUSIONS

Double positivity of IgE to bee and Vespula venom is often caused by crossreactions, especially to CCDs. IgE to both Api m1 and Ves v5 indicates true double sensitization and immunotherapy with both venoms.

Diphenylphosphinoyl chloride as a chlorinating agent ? the selective double activation of 1,2-diols

Treatment of 1,2-diols with diphenylphosphinoyl chloride in pyridine produces beta-chloroethyl phosphinates which react with complete control of stereochemistry to give epoxides and azido-alcohols, useful intermediates in cyclopropane synthesis.

Acyclic, achiral enamide nucleoside analogues. The importance of the C=C bond in the analogue for its ability to mimic natural nucleosides

The conformations of an acyclic, achiral enamide thymidine analogue 1 have been studied by model building and geometry calculations, as well as by NMR NOE and UV experiments. The results indicate that there are no significant barriers to rotation around any of the sigma bonds, in particular the N1-C1' enamide bond, and that the analogue should be able to accommodate conformations that mimic the conformations of natural nucleosides in A- and B-type helices quite well. For comparison the saturated analogue 2 has been prepared and built into oligonucleotides. It is shown that incorporation of 2 in oligonucleotides results in a much larger depression of the melting temperature (deltaTm -10 to -12.5 degrees C) than does incorporation of 1 (deltaTm -5 to -6.5 degrees C).

Preparation and antiviral properties of new acyclic, achiral nucleoside analogues: 1- or 9-[3-hydroxy-2-(hydroxymethyl)prop-1-enyl]nucleobases and 1- or 9-[2,3-dihydroxy-2-(hydroxymethyl)propyl]nucleobases

Acyclic, achiral nucleoside derivatives 1b-e of adenine, cytosine, 5-methylcytosine, and guanine, containing a 3-hydroxy-2-(hydroxymethyl)prop-1-enyl group on N-1 or N-9, have been prepared analogously to the previously described thymine derivative 1a. In contrast to the adenine and guanine derivatives, the cytosine derivative 9 was unstable, and was obtained in a low yield due to side reactions. These include cleavage of the propenyl group from the base, and the formation of a bicyclic compound. The thymine derivative, although stable under neutral conditions, likewise underwent a reversible cyclization reaction (Michael addition) in the presence of acids or bases. The 5-methylcytosine derivative was stable under neutral and basic conditions. Four other nucleoside derivatives 26a-d containing a 2,3-dihydroxy-2-(hydroxymethyl)propyl group on N-1 or N-9, three of which are new, have likewise been prepared. All compounds were evaluated as antiviral agents against HIV-1 and HSV-1 but were devoid of antiviral activity.

Preparation and properties of a new type of acyclic, achiral nucleoside analogue

Preparation of the nucleoside analogues 1 and incorporation of 1, B = T, in deoxyribooligonucleotides by the phosphoramidite method is described. A two-step deprotection procedure was developed to reduce cleavage of the modified allylic unit. The binding properties of the modified oligonucleotides towards complementary DNA and RNA has been evaluated by Tm measurements showing a deltaTm of -2 to -6.5 degrees C per modification. An oligonucleotide with two modifications at the 3'-end showed considerable resistance towards cleavage by a 3'-exonuclease. No antiviral activity against HIV-1 or HSV-1 was found for 1, B = G or T, or for any of the trihydroxy derivatives 5.

A new type of acyclic, achiral nucleoside analogue. How does it simulate nucleosides?

The new monomer 1 seems to be an excellent mimic of nucleosides with different sugar conformations (north, south, and envelope), because of the relatively free rotation around gamma, delta, and chi. The rotation around chi is primarily controlled by the repulsion between H6 and the two hydrogen atoms on C4' and not pi conjugation between the double bond and the nucleobase. A viable synthesis of the guanine monomer 8 is described.

Oligonucleotides containing a new type of acyclic, achiral nucleoside analogue: 1-[3-hydroxy-2-(hydroxymethyl)prop-1-enyl]thymine

An achiral, acyclic nucleoside analogue has been incorporated once or twice in oligodeoxyribonucleotides by the phosphoramidite method, and conditions found which allow deprotection of the oligonucleotides containing a sensitive modified allylic unit. The binding affinity of the modified oligonucleotides towards complementary DNA and RNA was reduced compared to unmodified DNA (DeltaT(m) -2 to -6.5 degrees C). An oligonucleotide with two modifications at the 3'-end showed considerable resistance towards cleavage with a 3'-exonuclease.

Differences in activation of G2/M checkpoint in keratinocytes after genotoxic stress induced by hydrogen peroxide and ultraviolet A radiation

Long-wave ultraviolet radiation (UVA) may cause extensive DNA damage via reactive oxygen species (ROS). In this study we examined whether UVA- and H2O2-mediated DNA damage have equivalent effects on the induction of G2/M phase checkpoint and cell cycle progression in a transformed keratinocyte cell line HaCaT. By employing single cell gel electrophoresis (comet assay) we determined the equipotent doses of UVA and H2O2 with respect to the induction of alkali-labile sites (an indicator of oxidative DNA decay). However, in contrast to H2O2 which caused a pronounced G2/M cell cycle arrest 24 h after treatment, UVA irradiation did not affect cell cycle progression. Increasing UVA doses up to 150 kJ/m2 did not affect cell cycle and proliferation whereas increasing H2O2 concentrations caused a cell cycle block or cell death. Cytometric analysis revealed that G2/M cell cycle arrest took place beyond the cyclin B1 restriction point. We conclude that the DNA damage induced by UVA is easily repaired and does not perturb cell growth, whereas the H2O2-induced damage leads ultimately to cell cycle arrest or cell death.

Hydrogen peroxide is responsible for UVA-induced DNA damage measured by alkaline comet assay in HaCaT keratinocytes

We investigated the role of different reactive oxygen species (ROS) in ultraviolet A (UVA)-induced DNA damage in a human keratinocyte cell line, HaCaT. UVA irradiation increased the intracellular levels of hydrogen peroxide (H2O2), detected by a fluorescent probe carboxydichlorodihydrofluorescein, and caused oxidative DNA damage, single strand-breaks and alkali-labile sites, measured by alkaline single cell gel electrophoresis (comet assay). Superoxide anion (O2*-) was a likely substrate for H2O2 production since diethyldithiocarbamate (DDC), a superoxide dismutase blocker, decreased the level of intracellular H2O2. Hydrogen peroxide was shown to play a central role in DNA damage. Increasing the intracellular levels of H2O2 with aminotriazole (AT) (a catalase blocker) and buthionine sulfoximine (BSO) (an inhibitor of glutathione synthesis) potentiated the UVA-induced DNA damage. Exogenous H2O2 was also able to induce DNA damage. Since H2O2 alone is not able to damage DNA directly, we investigated the significance of the H2O2-derived hydroxyl radical (*OH). Addition of FeSO4, that stimulates *OH formation from H2O2 (Fenton reaction) resulted in a twofold increase of DNA-damage. Desferrioxamine, an iron chelator that blocks the Fenton reaction, prevented UVA-induced DNA damage. We also employed a panel of less specific antioxidants and enzyme modulators. Sodium selenite (Na-Se) present in glutathione peroxidase and thioredoxin reductase and addition of glutathione (GSH) prevented DNA-damage. Tocopherol potently prevented UVA-and H2O2-induced DNA damage and reduced intracellular H2O2 -levels. Ascorbic acid reduced H2O2 production, but only partly prevented DNA damage. Singlet oxygen (1O2) did not seem to play an important role in the UVA-induced DNA-damage since the specific 1O2 scavenger sodium azide (NaN3) and the less specific 1O2 scavenger beta-carotene did not markedly prevent either DNA-damage or H2O2 production. In conclusion the conversion of H2O2 to *OH appears to be the most important step in UVA-induced generation of strand breaks and alkali-labile sites and the bulk H2O2 appears to originate from O2*- generated by UVA irradiation.

Laser scanning cytometry for comet assay analysis

BACKGROUND

The comet assay (single-cell gel electrophoresis) is a sensitive method for evaluating nuclear DNA damage. Previously used evaluation methods for the comet assay are time consuming and have an inherent risk of biased selection of comets due to manual selection and categorization of comet images. Laser scanning cytometry (LSC), the principle of which is equivalent to flow cytometry, enables quantification of fluorescence emitted from the cells on a microscope slide. In the present study, we explored whether LSC could be used to determine the degree of DNA damage demonstrated by the comet assay.

METHODS

DNA damage was induced by ultraviolet A irradiation of keratinocytes and visualized by the comet assay. The evaluation included (a) LSC determination of DNA-specific fluorescence in 1,000 comet heads (undamaged DNA), (b) image acquisition of comets by rescanning of the microscope slide, and (c) digital image analysis and computation of tail moment and DNA content in the comet tails.

RESULTS

Cells with damaged DNA were observed in a sub-G(1) area because the comet head loses DNA to the tail. We found a strong inverse correlation between tail moment and DNA content per nucleus.

CONCLUSIONS

LSC enables an automated method for cell recognition and evaluation of the comets, thus providing quantitative information about nuclear DNA damage without subjective selection of analyzed comets.