Phenyl phosphotriester derivatives of AZT: Variations upon the SATE moiety

Synthesis, characterization, biological properties, and molecular docking studies of new phosphoramide-based Ag(i) complexes

The effect of two new synthesized Ag(i) complexes on their biological properties was examined.

Nano Co-Crystal Embedded Stimuli-Responsive Hydrogels: A Potential Approach to Treat HIV/AIDS

Currently, the human immunodeficiency virus (HIV) that causes acquired immunodeficiency syndrome (AIDS) can only be treated successfully, using combination antiretroviral (ARV) therapy. Lamivudine (3TC) and zidovudine (AZT), two compounds used for the treatment of HIV and prevention of disease progression to AIDS are used in such combinations. Successful therapy with 3TC and AZT requires frequent dosing that may lead to reduced adherence, resistance and consequently treatment failure. Improved toxicity profiles of 3TC and AZT were observed when combined as a nano co-crystal (NCC). The use of stimuli-responsive delivery systems provides an opportunity to overcome the challenge of frequent dosing, by controlling and/or sustaining delivery of drugs. Preliminary studies undertaken to identify a suitable composition for a stimulus-responsive in situ forming hydrogel carrier for 3TC-AZT NCC were conducted, and the gelation and erosion time were determined. A 25% w/w Pluronic® F-127 thermoresponsive hydrogel was identified as a suitable carrier as it exhibited a gelation time of 5 min and an erosion time of 7 days. NCC-loaded hydrogels were evaluated using in vitro dissolution and cytotoxicity assays. In vitro dissolution undertaken using membrane-less diffusion over 168 h revealed that 3TC and AZT release from NCC-loaded hydrogels was complete and followed zero-order kinetic processes, whereas those loaded with the micro co-crystal and physical mixture were incomplete and best described using the Korsmeyer-Peppas kinetic model. The release of AZT and 3TC from the physical mixture and MCC-loaded gel exhibited a value for n of 0.595 for AZT release from the physical mixture and 0.540 for the MCC technology, whereas the release exponent for 3TC was 0.513 for the physical mixture and 0.557 for the MCC technology indicating that diffusion and erosion controlled 3TC and AZT release. In vitro cytotoxicity assay data revealed that the addition of NCC to the thermoresponsive hydrogel resulted in an improved cell viability of 88.0% ± 5.0% when compared to the cell viability of the NCC of 76.9% ± 5.0%. The results suggest that the use of a thermoresponsive nanosuspension may have the potential to be delivered as an intramuscular injection that can subsequently increase bioavailability and permit dose reduction and/or permit use of a longer dosing frequency.

RNA interference activity of single-stranded oligonucleotides linked between the passenger strand and the guide strand with an aryl phosphate linker

Recently, we demonstrated that asymmetrical 18 base-paired double-strand oligonucleotides comprised of alternately combined 2'-O-methyl RNA and DNA, termed MED-siRNAs, show high RNase resistance, efficient cleavage of target mRNA, and the subsequent reduction of target protein expression. The 5'-terminal phosphate group and the 3'-overhang of the guide strand were required to fully activate the RNAi activity of MED-siRNAs. Here, we evaluated MED-siRNAs modified with aryl phosphate groups at the 5'-end of the guide strand. The 5'-aryl phosphorylated MED-siRNAs showed highly efficient reduction of target protein expression comparable to 5'-phosphorylated MED-siRNAs. Moreover, 5'-aryl phosphorylated MED-siRNAs linked between the aryl phosphate group at the 5'-end of the guide strand and the hydroxyl group at the 3'-end of the passenger strand with alkyl amide linkers or peptides (e.g., DL-Ser-L-Ala-L-Tyr), resulted in single-stranded MED-siRNAs with a highly efficient cleavage activity of target mRNA with binding to Argonaute 2 via an RNA interference mechanism. These linker techniques could also be used to create siRNAs composed of naturally-occurring molecules such as amino acids. These findings suggest the possibility of using these single-stranded MED-siRNAs as siRNA reagents.Supplemental data for this article is available online at https://doi.org/10.1080/15257770.2021.1927077 .

Sonochemical synthesis of a nanodandelion tin(IV) complex with carbacylamidophosphate ligand as anti-Alzheimer agent: Molecular docking study

The dandelion-shaped nanostructure of an organotin complex with formula Sn(CH₃)₂Cl₂}NC₅H₄C(O)NHP(O)[NHC₆H₁₁]₂}₂ (C₁) was synthesized by means of a sonochemical method. Nano-structures were characterized by elemental analysis, NMR, SEM-EDS, XRD, UV-Vis, and FT-IR spectroscopy. The thermal stability of the complex C₁ has been studied by thermal gravimetric analysis (TGA), and compared to the bulk form (C₂). Both the morphology and the size of the ultrasound-assisted synthesized organotin complex have been investigated using scanning electron microscopy (SEM) by changing such parameters as the concentration of initial reactants and the sonication frequency. Two different forms of the organotin complex (C₁, C₂) and the corresponding ligand (L) were evaluated by a modified Ellman's method on acetyl- and butyrylcholinesterase enzymes. Nanodendalion C₁ and ligand L showed the best activity against AChE and BChE, respectively, with the IC₅₀ values being 326.59 μg/ml and 426.68 μg/ml. Further, Lineweaver Burk plots indicated that these compounds are mixed inhibitors. The synthesized compounds and cholinesterase enzymes were simulated by molecular docking for more details concerning the conformation and the orientations of these compounds in the active site of the receptor.

Characteristics of ovarian cancer detection by a near-infrared fluorescent probe activated by human NAD(P)H: quinone oxidoreductase isozyme 1 (hNQO1)

Near-infrared (NIR) fluorescent probes are ideal for in vivo imaging, because they offer deeper tissue penetration by the light and lower background autofluorescence than fluorophores that emit in the visible range. Q₃STCy is a newly synthesized, NIR light-emitting probe that is activated by an enzyme commonly overexpressed in tumor cells, human nicotinamide adenine dinucleotide (phosphate): quinone oxidoreductase isozyme 1, known as hNQO1 or DT-diaphorase. The purpose of this study is to compare the sensitivity of detecting peritoneal ovarian cancer metastasis (POCM) with Q₃STCy and gGlu-HMRG, a green fluorescent probe, upon their surface application. In vitro uptake of Q₃STCy was significantly higher than that of gGlu-HMRG. Using a red fluorescence protein (RFP)-labeled in vivo tumor model of POCM, the Q₃STCy probe provided high sensitivity (96.9%) but modest specificity (61.0%), most likely the result of albumin-probe interactions and non-specific activation in nearby altered but healthy cells. Three types of kinetic maps based on maximum fluorescence signal (MF), wash-in rate (WIR), and area under the curve (AUC) allowed for differentiation of the activated fluorescence signal associated with POCM from the background signal of the small intestine, thereby significantly improving the specificity of Q₃STCy to 80%, 100%, and 100% for MF, WIR, and AUC, as well yielding a moderate improvement in sensitivity (100% for all approaches) that is comparable to that with gGlu-HMRG, but with the added advantages of NIR fluorescence as the transduction modality. Such a new methodology has the potential to afford identification of cancerous lesions deeper within tissue.

B, Golla K, Kondapi AK. Improved Safety, Bioavailability and Pharmacokinetics of Zidovudine through Lactoferrin Nanoparticles during Oral Administration in Rats

Zidovudine (AZT) is one of the most referred antiretroviral drug. In spite of its higher bioavailability (50–75%) the most important reason of its cessation are bone marrow suppression, anemia, neutropenia and various organs related toxicities. This study aims at the improvement of oral delivery of AZT through its encapsulation in lactoferrin nanoparticles (AZT-lactonano). The nanoparticles (NPs) are of 50–60 nm in size and exhibit 67% encapsulation of the AZT. They are stable in simulated gastric and intestinal fluids. Anti-HIV-1 activity of AZT remains unaltered in nanoformulation in acute infection. The bioavailability and tissue distribution of AZT is higher in blood followed by liver and kidney. AZT-lactonano causes the improvement of pharmacokinetic profile as compared to soluble AZT; a more than 4 fold increase in AUC and AUMC in male and female rats. The serum C_max for AZT-lactonano was increased by 30%. Similarly there was nearly 2-fold increase in T_max and t_1/2. Our in vitro study confirms that, the endosomal pH is ideal for drug release from NPs and shows constant release from up to 96h. Bone marrow micronucleus assay show that nanoformulation exhibits approximately 2fold lower toxicity than soluble form. Histopathological and biochemical analysis further confirms that less or no significant organ toxicities when nanoparticles were used. AZT-lactonano has shown its higher efficacy, low organs related toxicities, improved pharmacokinetics parameter while keeping the antiviral activity intact. Thus, the nanoformulation are safe for the target specific drug delivery.

3-Acetyloxy-2-cyano-2-(alkylaminocarbamoyl)propyl groups as biodegradable protecting groups of nucleoside 5´-mono-phosphates

Thymidine 5´-bis[3-acetyloxy-2-cyano-2-(2-phenylethylcarbamoyl)propyl]phosphate (1) has been prepared and the removal of phosphate protecting groups by hog liver carboxyesterase (HLE) at pH 7.5 and 37 °C has been followed by HPLC. The first detectable intermediates are the (R_P)- and (S_P)-diastereomers of the monodeacetylated triester 14, which subsequently undergo concurrent retro-aldol condensation to diester 4 and enzyme-catalyzed hydrolysis to the fully deacetylated triester 15. The former pathway predominates, representing 90% of the overall breakdown of 14. The diester 4 undergoes the enzymatic deacetylation 700 times less readily than the triester, but gives finally thymidine 5´-monophosphate as the desired main product. To elucidate the potential toxicity of the electrophilic 2-cyano-N-(2-phenylethyl)acrylamideby-product 17 released upon the deprotection, the hydrolysis of 1 has also been studied in the presence of glutathione (GSH).

Biodegradable protections for nucleoside 5'-monophosphates: comparative study on the removal of O-acetyl and O-acetyloxymethyl protected 3-hydroxy-2,2-bis(ethoxycarbonyl)propyl groups

The applicability of 3-acetyloxy-2,2-bis(ethoxycarbonyl)propyl and 3-acetyloxymethoxy-2,2-bis(ethoxycarbonyl)propyl groups as biodegradable phosphate protecting groups for nucleoside 5'-monophosphates has been studied in a HEPES buffer at pH 7.5. Enzymatic deacetylation with porcine carboxyesterase triggers the removal of the resulting 3-hydroxy-2,2-bis(ethoxycarbonyl)propyl and 3-hydroxymethoxy-2,2-bis(ethoxycarbonyl)propyl groups by retro-aldol condensation and consecutive half acetal hydrolysis and retro-aldol condensation, respectively. The kinetics of these multistep deprotection reactions have been followed by HPLC, using appropriately protected thymidine 5'-monophosphates as model compounds. The enzymatic deacetylation of the 3-acetyloxymethoxy-2,2-bis(ethoxycarbonyl)propyl 5'-triester (2) is 25-fold faster than the deacetylation of its 3-acetyloxy-2,2-bis(ethoxycarbonyl)propyl-protected counterpart 1, and the difference in the deacetylation rates of the resulting diesters, 12b and 12a, is even greater. With 2, conversion to thymidine 5'-monophosphate (5'-TMP) is quantitative, while conversion of 1 to 5'-TMP is accompanied by formation of thymidine. Consistent with the preceding observations, quantitative release of 5'-TMP from 2 has been shown to take place in a whole cell extract of human prostate cancer cells.

Prodrug approaches to improving the oral absorption of antiviral nucleotide analogues

Nucleotide analogues have been well accepted as therapeutic agents active against a number of viruses. However, their use as antiviral agents is limited by the need for phosphorylation by endogenous enzymes, and if the analogue is orally administered, by low bioavailability due to the presence of an ionizable diacid group. To circumvent these limitations, a number of prodrug approaches have been proposed. The ideal prodrug achieves delivery of a parent drug by attachment of a non-toxic moiety that is stable during transport and delivery, but is readily cleaved to release the parent drug once at the target. Here, a brief overview of several promising prodrug strategies currently under development is given.