Tarek Aboul-Fadl

Antisense oligonucleotides: the state of the art.

The use of antisense oligonucleotides as therapeutic agents has generated considerable enthusiasm in the research and medical community. Antisense oligonucleotides as therapeutic agents were proposed as far back as in the 1970s when the antisense strategy was initially developed. Nonetheless, it has taken almost a quarter of a century for this potential to be realized. The principle of antisense technology is the sequence-specific binding of an antisense oligonucleotide to target mRNA, resulting in the prevention of gene translation. The specificity of hybridization by Watson-Crick base pairing make antisense oligonucleotides attractive as tools for targeted validation and functionalization, and as therapeutics to selectively modulate the expression of genes involved in the pathogenesis of diseases. The last few years have seen a rapid increase in the number of antisense molecules progressing past Phase I, II and III clinical trials. This review outlines the basic concept of the antisense technology, its development and recent potential therapeutic applications.

Schiff bases of indoline-2,3-dione (isatin) derivatives and nalidixic acid carbohydrazide, synthesis, antitubercular activity and pharmacophoric model building.

Tuberculosis (TB) remains among the worlds great public health challenges. Worldwide resurgence of TB is due to two major problems: the AIDS epidemic, which started in the mid-1980s, and the outbreak of multidrug resistant (MDR) TB. Thus, there is an urgent need for anti-TB drugs with enhanced activity against MDR strains. In recent years, Schiff bases of 1H-indole-2,3-diones are reported to exhibit anti-TB activity. On the other hand, several quinolone antibacterial agents have been examined as inhibitors of TB, as well as other mycobacterial infections. Accordingly, the current work involved design and synthesis of Schiff bases of nalidixic acid carbohydrazide and isatin derivatives (5,6a-f and 7,8a-c). Structures of the synthesized derivatives were confirmed on the bases of spectral methods of analyses. Anti-TB activity of the synthesized derivatives was investigated against four Mycobacterium strains: Mycobacterium intercellulari, Mycobacterium xenopi, Mycobacterium cheleneo and Mycobacterium smegmatis. Modest anti-TB activity was observed within the investigated compounds, however, compound 5f revealed potent anti-TB activity with MIC 0.625 microg/ml, which is 20 times greater than the reference drug isoniazid, INH, (MIC = 12.5 microg/ml). A hypothetical pharmacophore model was built using Molecular Operating Environment (MOE) program and 10 compounds structurally related to the synthesized ones with reported anti-TB activity. The Pharmacophoric model built revealed the necessity of the following pharmacophoric features for anti-TB activity: aromatic center, hydrogen bond acceptor/metal ligator center, hydrogen bond donor center and aromatic center/hydrophobic area. Theses features were consistent with the found anti-TB activity of the tested compounds.

Synthesis, antitubercular activity and pharmacokinetic studies of some Schiff bases derived from 1-alkylisatin and isonicotinic acid hydrazide (INH).

N′-(1-alkyl-2,3-dihydro-2-oxo-1H-3-indolyliden)-4-pyridinecarboxylic acid hydrazide derivatives,3(a-g), were synthesized in a trial to overcome the resistance developed with the therapeutic uses of isoniazid (INH). The lipophilicity of the synthesized derivatives supersedes that of the INH as expressed by Clog p values. The synthesized compounds and INH were tested against bovin, human sensitive and human resist strains of Mycobacterium tuberculosis. Compounds3a, 3d, 3f and3g with 1-unsubstituted, 1-propyl, 1-propynyl and 1-benzyl groups respectively exhibited equipotent growth inhibitory activity (MIC 10 μmol) against the tested strains as compared with INH however the later has no activity against human resist strain. Pharmacokinetic study revealed that the rate and extent of absorption of the tested derivatives (3d and3f) significantly higher than that of INH (p<0.05). The relative bioavailabilities (FR%) were 183.15 and 443.25 for3f and3d respectively as compared to INH. These results preliminary indicate the possible use of the prepared derivatives for treatment of tuberculosis infections in order to overcome the resistance developed with INH.

New prodrug approach for amino acids and amino-acid-like drugs

Summary A series of disubstituted tetrahydro-2 H -1,3,5-thiadiazine-2-thione (THTT) derivatives 4a–g were prepared and found to be promising prodrugs for amino acids and similar compounds. The pH profile for the degradation of the THTT derivatives in aqueous buffer solutions was determined using HPLC and was accounted for in terms of specific base-catalyzed reactions. The compounds, however, showed high acid stability. Enzymatic hydrolysis (human serum) of the derivatives offered an advantageous range of t 1/2 values, which may be useful in controlling the onset and the duration of action of drugs.

Cyclic amide derivatives as potential prodrugs II: N-hydroxymethylsuccinimide- / isatin esters of some NSAIDs as prodrugs with an improved therapeutic index.

Ester prodrugs of aspirin 1a, ibuprofen 1b, naproxen 1c and indomethacin 1d were synthesized using N-Hydroxymethylsuccinimide (HMSI) 3 and N-hydroxymethylisatin (HMIS) 4 as promoieties to reduce their gastrointestinal toxicity and improve bioavailability. Additionally, the kinetics of hydrolysis of the synthesized prodrugs 5a-d and 6a-d were studied at 37 degrees C in non-enzymatic simulated gastric fluid (SGF; hydrochloric acid buffer pH = 1.2); 0.02 M phosphate buffer (pH = 7.4); 80% human plasma and 10% rat liver homogenate. The results indicate higher chemical stability of the ester prodrugs in non-enzymatic SGF (t(1/2) congruent with 6.5-18.6 h) and rapid conversion to the parent drugs in 80% human plasma (t(1/2) congruent with 11.4-235 min) as well as in 10% rat liver homogenates (t(1/2) congruent with 12.0-90.0 min). As a general pattern, the HMSI esters 5a-d revealed higher chemical stability than the corresponding HMIS analogues 6a-d. The pH-rate profile of 5c and 6a indicated maximum stability of the former at pH = 1.2-8.0 and of the latter at pH = 1.2-4.0. The distribution coefficient (D(7.4)) values of the prodrugs 5a-d, 6a-d and the parent drugs 1a-d in an n-octanol/phosphate buffer (pH = 7.4) system indicated enhanced lipophilic properties of the prodrugs. Furthermore, the HMIS ester prodrugs 6a-d are more lipophilic than the corresponding HMSI derivatives 5a-d. In vivo ulcerogenicity studies using scanning electron microscopy on stomach specimens of rats treated with an oral dose for 4 d revealed that the synthesized ester prodrugs are significantly less irritating to gastric mucosa than the parent drugs. These results suggested HMSI and/or HMIS esters possess good potential as prodrugs with an improved therapeutic index for oral delivery of NSAIDs.

New 2H-tetrahydro-1, 3, 5-thiadiazine-2-thiones incorporating glycine and glycinamide as potential antifungal agents.

The new title derivatives (4b—h and 5a—i) were synthesized by reaction of the appropriate primary amine, carbon disulphide, and formaldehyde. These derivatives were prepared in order to study the effects of introducing polar groups at N3 or N5 or at both positions on the biological activity. The compounds were tested for their antifungal activity in vitro against pathogenic (Trichophyton rubrum and Candida albicans), phytopathogenic (Penicillum expansum, Trichoderma hazianum, and Fasarium oxysporum), and aflatoxin‐producing (Aspergillus flavus) fungi. These compounds exhibited varied inhibitory effects on growth or sporulation of some tested fungal species.

Schiff Bases of Indoline-2,3-dione: Potential Novel Inhibitors of Mycobacterium Tuberculosis (Mtb) DNA Gyrase †

In the present study a series of Schiff bases of indoline-2,3-dione were synthesized and investigated for their Mtb gyrase inhibitory activity. Promising inhibitory activity was demonstrated with some of these derivatives, which exhibited IC50 values ranging from 50–157 μM. The orientation and the ligand-receptor interactions of such molecules within the Mtb DNA gyrase A subunit active site were investigated applying a multi-step docking protocol using Molecular Operating Environment (MOE) and Autodock4 docking software. The results revealed the importance of the isatin moiety and the connecting side chain for strong interactions with the enzyme active site. Among the tested compounds the terminal aromatic ring benzofuran showed the best activity. Promising new leads for developing a novel class of Mtb gyrase inhibitors were obtained from Schiff bases of indoline-2,3-dione.

Di- and trisubstituted pyrazolo[1,5-a]pyridine derivatives: Synthesis, dopamine receptor binding and ligand efficacy

Based on the lead molecule FAUC 113, a series of di- and trisubstituted pyrazolo[1,5-a]pyridine derivatives was synthesized and investigated for their dopamine receptor binding profile. The carbonitrile 11a (FAUC 327) showed excellent pharmacological properties combining high D4 affinity (K(i)=1.5 nM) and selectivity with significant intrinsic activity (31%) in low nanomolar concentrations (EC50=1.5 nM).

Design, synthesis and pharmacophoric model building of novel substituted nicotinic acid hydrazones with potential antiproliferative activity

Novel 6-aryl-2-methylnicotinic acid hydrazides 4a-c and their corresponding hydrazones 5a-c and 6a-i were synthesized. X-ray single crystal diffraction of 6h confirmed the chemical structure of hydrazones 6a-i. Antiproliferative activity of the synthetic compounds was investigated against K562 leukemia cell lines. Variable cell growth inhibitory activities were obtained with IC50 range from 24.99 to 66.78 μM where the compound 6c exhibited the maximum activity. Structure activity relationship analysis has been performed and a common pharmacophore model for the synthesized derivatives has been obtained by using the pharmacophore elucidation module of the software MOE. The best model obtained is characterized by two projected locations of potential H-bond donors (F 3 and F4) and two Aromatic annotations (F1 and F2).

Selective Spectrophotometric and Spectrofluorometric Methods for the Determination of Amantadine Hydrochloride in Capsules and Plasma via Derivatization with 1,2-Naphthoquinone-4-sulphonate

New selective and sensitive spectrophotometric and spectrofluorometric methods have been developed and validated for the determination of amantadine hydrochloride (AMD) in capsules and plasma. The methods were based on the condensation of AMD with 1,2-naphthoquinone-4-sulphonate (NQS) in an alkaline medium to form an orange-colored product. The spectrophotometric method involved the measurement of the colored product at 460  nm. The spectrofluorometric method involved the reduction of the product with potassium borohydride, and the subsequent measurement of the formed fluorescent reduced AMD-NQS product at 382  nm after excitation at 293  nm. The variables that affected the reaction were carefully studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9972–0.9974) and low LOD (1.39 and 0.013 μg mL−1) were obtained in the ranges of 5–80 and 0.05–10  μg mL−1 for the spectrophotometric and spectrofluorometric methods, respectively. The precisions of the methods were satisfactory; RSD ≤2.04%. Both methods were successfully applied to the determination of AMD in capsules. As its higher sensitivity, the spectrofluorometric method was applied to the determination of AMD in plasma; the recovery was 96.3–101.2 ± 0.57–4.2%. The results obtained by the proposed methods were comparable with those obtained by the official method