Quantitative Evaluation of Dendritic Nanoparticles in Mice: Biodistribution Dynamics and Downstream Tumor Efficacy Outcomes.

A physiologically based pharmacokinetic model was developed to describe the tissue distribution kinetics of a dendritic nanoparticle and its conjugated active pharmaceutical ingredient (API) in plasma, liver, spleen, and tumors. Tumor growth data from MV-4-11 tumor-bearing mice were incorporated to investigate the exposure/efficacy relationship. The nanoparticle demonstrated improved antitumor activity compared to the conventional API formulation, owing to the extended released API concentrations at the site of action. Model simulations further enabled the identification of critical parameters that influence API exposure in tumors and downstream efficacy outcomes upon nanoparticle administration. The model was utilized to explore a range of dosing schedules and their effect on tumor growth kinetics, demonstrating the improved antitumor activity of nanoparticles with less frequent dosing compared to the same dose of naked APIs in conventional formulations.

Experimental design, development and evaluation of extended release subcutaneous thermo-responsive in situ gels for small molecules in drug discovery.

The objective of this work is to develop extended release subcutaneous thermo-responsive in situ gel-forming delivery systems using the following commercially available triblock polymers: poly (lactic-co-glycolic acid)-poly (ethylene glycol)-poly (lactic-co-glycolic acid) (PLGA-PEG-PLGA, copolymer A & B) and poly (lactide-co-caprolactone)-poly (ethylene glycol)-poly (lactide-co-caprolactone) (PLCL-PEG-PLCL, copolymer C). Performance of two optimized formulations containing ketoprofen as a model compound, was assessed by comparing in vitro drug release profiles with in vivo performance following subcutaneous administration in rats. This work employs a Design of Experiment (DoE) approach to explore first, the relationship between copolymer composition, concentration, and gelation temperature (GT), and second, to identify the optimal copolymer composition and drug loading in the thermo-responsive formulation. Furthermore, this work discusses the disconnect observed between in vitro drug release and in vivo pharmacokinetic (PK) profiles. In vitro, both formulations showed extended-release profiles for 5-9 days, while PK parameters and plasma profiles were similar in vivo without extended release observed. In conclusion, a clear disconnection is observed between in vitro ketoprofen drug release and in vivo performance from the two thermogel formulations tested. This finding highlights a remaining challenge for thermogel formulation development, that is, being able to accurately predict in vivo behavior from in vitro results.

Generation of High-Quality Pharmacokinetic Data From Parallel Tail Vein Dosing And Bleeding in Non-cannulated Rats.

It is common practice to use cannulated rats for pharmacokinetic (PK) in-life studies as it yields high quality PK parameter estimation. While offering many benefits, cannulation requires surgery, post-surgical care, and cannula maintenance. As an alternative approach, the strategy of dosing and bleeding rats via the tail vein in a single experiment is technically feasible and theoretically offers many benefits. Unfortunately, however, as reported by F Tse et al. in 1984 (J Pharm Sci 73: https://doi.org/10.1002/jps.2600731128), parallel tail dosing and bleeding is scientifically flawed and yields inaccurate estimation of PK parameters following intravenous administration. The underlying causality of poor data quality has not been addressed in over 35 years. To overcome the technical flaws associated with parallel tail dosing and bleeding, we have developed a Tail-Dose-Bleed (TDB) method as a substitute for use of cannulated rats. Specifically, the method introduces a flush procedure after dosing, uses separate tail veins for dosing and bleeding, and adjusts dosing and sampling to the proximal and distal portions of the tail, respectively. To demonstrate the proof of principle for this TDB technique, several cassette dosing studies were conducted. The performance of the TDB technique is compared in both stand alone and animal crossover studies employing conventional jugular/femoral bleeding and dosing. The poor data via tail dosing and bleeding previously described by Tse et al. are also recapitulated using their described approach. To ensure broad applicability of the TDB technique, data were generated utilizing compounds of diverse physical chemical properties manifesting a range of clearance and/or volume of distribution characteristics. These data demonstrate that the TDB approach yields comparable PK profiles and parameters as compared to conventional femoral dosing / jugular bleeding. Using this newly described TDB procedure, we demonstrate the ability to overcome documented data quality issues when dosing and bleeding via the tail. The TDB technique has numerous operational advantages of reduced study turnaround time and improved cost effectiveness, but most importantly, addresses key animal welfare concerns relevant to institutional animal care and use committees (IACUC). The notable advantage here is reduced animal stress and discomfort by eliminating the need for surgery and recovery. And by consequence, allows for animals to be group housed and re-used without concern for loss of cannula patency. The tail dose and bleed method is simple and appears readily transferable to other laboratories.

A candidate drug administered subcutaneously to rodents as drug particles showing hepatic recirculation which influenced the sustained release process.

The aim of the present study was to evaluate and interpret the pharmacokinetic profiles after subcutaneous (s.c.) administration of crystalline AZ'72 nano- and microsuspensions to rodents. Both formulations were injected at 1.5 and 150 mg/kg to rats. For the lower dose, the profiles were similar after s.c. injection but extended as compared to oral administration. The overall exposure was higher for nanoparticles compared with microparticles during the investigated period. For the higher dose, injection of both suspensions resulted in maintained plateaus caused by the drug depots but, unexpectedly, at similar exposure levels. After addition of a further stabilizer, pluronic F127, nanosuspensions showed improved exposure with dose and higher exposure compared to larger particles in mice. Obviously, a stabilizer mixture that suits one delivery route is not necessarily optimal for another one. The differences in peak concentration (Cmax) between nano- and microparticles were mainly ascribed to differences in dissolution rate. Plasma profiles in mice showed curves with secondary absorption peaks after intravenous and oral administration, suggesting hepatic recirculation following both administration routes. This process, together with the depot formulation, complicates the analysis of absorption from s.c. administration, i.e. multiple processes were driving the plasma profile of AZ'72.

Simultaneous quantitative and qualitative analysis of bioactive phenols in Dendrobium aurantiacum var. denneanum by high-performance liquid chromatography coupled with mass spectrometry and diode array detection.

A novel high-performance liquid chromatographic method with mass spectrometry and diode array detection method for the simultaneous qualitative and quantitative analysis of bioactive phenols was developed. In total, nine chemically diverse phenols including five bibenzyls, three phenanthrenes and a coumarin were unambiguously identified in Dendrobium aurantiacum var. denneanum by comparison with the available references or reported data according to their retention behaviors, UV spectra and fragmentations of ESI-MS. The contents of the four main phenolic compounds, moscatilin, gigantol, moscatin and coumarin, in D. aurantiacum var. denneanum from the wild and various cultivated populations were determined by HPLC-UV. The sample preparation involved a rapid and simple procedure based on solid-phase extraction using a C(18) reversed-phase cartridge. The quantitative analysis was performed on a Beckman Coulter ODS column (5 microm, 250 x 4.6 mm) using a linear gradient elution system of acetonitrile-0.5% formic acid. The method was validated for linearity, limits of detection (LOD) and quantification (LOQ), precision and accuracy. Good results were obtained with respect to the overall intra- and inter-day variations (RSD less than 3.22%) and the percentage recoveries (ranging from 90.50 to 99.22%). Notable differences in the contents of phenols were observed among different cultivated populations. The samples colleted in April and May (spring), or October and November (autumn) accumulated much higher contents of phenols than those collected in other seasons.

Simultaneous analysis of trans- and cis-isomers of 2-glucosyloxycinnamic acids and coumarin derivatives in Dendrobium thyrsiflorum by high-performance liquid chromatography (HPLC)-photodiode array detection (DAD)-electrospray ionization (ESI)-tandem mass spectrometry (MS).

A novel method has been developed for simultaneous analysis for three pairs of trans- and cis-isomers of 2-glucosyloxycinnamic acids, along with their biogenic metabolites (three coumarin derivatives including scopoletin, scoparone and ayapin) in a Chinese medicinal herb Dendrobium thyrsiflorum by using high-performance liquid chromatography (HPLC)-photodiode array detection (DAD)-electrospray ionization (ESI)-tandem mass spectrometry (MS). The method was carried out by using a Polaris C18 column with a gradient solvent system of 0.5% acetic acid aqueous solution-acetonitrile. Seven target analytes including isodensifloside, isothyrsifloside, densifloside, thyrsifloside, scoparone, ayapin and scopoletin were exclusively identified by comparing their retention behaviors, UV and MS spectra with the authentic standards, and their contents in D. thyrsiflorum were simultaneous determined by employing UV detection at 342 nm. In addition, another pair of isomers of 2-glucosyloxycinnamic acids was putatively elucidated mainly based on the MS fragmentation. The method was validated and found to be satisfactorily linear, selective and robust. Recoveries ranged from 95.56 to 97.94% for all compounds at three different spiking levels. The limits of detection (LOD) and quantitation (LOQ) ranged, respectively, from 0.02 to 0.13 microg mL(-1) and 0.07 to 0.39 microg mL(-1) depending on various compounds. The established quality evaluation method was successfully used for evaluating the quality of D. thyrsiflorum samples of different organs and collections.

Bi-bicyclic and bi-tricyclic compounds from Dendrobium thyrsiflorum.

One bi-bicyclic and two bi-tricyclic derivatives of coumarin-benzofuran, phenanthrene-phenanthrene and phenanthrene-phenanthraquinone, along with seven known compounds, were isolated from stems of Dendrobium thyrsiflorum Rchb.f. (Orchidaceae). On the basis of chemical, NMR (1H, 13C, HMQC, HMBC and NOESY) and mass spectrometry data, their structures were elucidated as denthyrsin [3-(5',6'-dimethoxybenzofuran-2'-yl)-6,7-dimethoxy-2H-chromen-2-one; 1], denthyrsinol (4,5'-dimethoxy-[1,1']biphenanthrenyl-2,5,4',7'-tetraol; 2), and denthyrsinone (7,4',7'-trihydroxy-2,2',8'-trimethoxy-[5,1']biphenanthrenyl-1,4-dione; 3). Compounds 1-3 and denthyrsinin (1,5,7-trimethoxyphenanthrene-2,6-diol; 4) showed significant cytotoxic activities against Hela (13.5, 9.3, 9.9 and 2.7 microM, respectively), K-562 (0.45, 1.6, 6.0 and 2.3 microM, respectively) and MCF-7 (18.1, not tested, 3.5 and 4.8 microM, respectively) cell lines.