6 research outputs found
Prediction of drug penetration in tuberculosis lesions
The
penetration of antibiotics in necrotic tuberculosis lesions is heterogeneous
and drug-specific, but the factors underlying such differential partitioning
are unknown. We hypothesized that drug binding to macromolecules in
necrotic foci (or caseum) prevents passive drug diffusion through
avascular caseum, a critical site of infection. Using a caseum binding
assay and MALDI mass spectrometry imaging of tuberculosis drugs, we
showed that binding to caseum inversely correlates with passive diffusion
into the necrotic core. We developed a high-throughput assay relying
on rapid equilibrium dialysis and a caseum surrogate designed to mimic
the composition of native caseum. A set of 279 compounds was profiled
in this assay to generate a large data set and explore the physicochemical
drivers of free diffusion into caseum. Principle component analysis
and modeling of the data set delivered an in silico signature predictive
of caseum binding, combining 69 molecular descriptors. Among the major
positive drivers of binding were high lipophilicity and poor solubility.
Determinants of molecular shape such as the number of rings, particularly
aromatic rings, number of sp<sup>2</sup> carbon counts, and volume-to-surface
ratio negatively correlated with the free fraction, indicating that
low-molecular-weight nonflat compounds are more likely to exhibit
low caseum binding properties and diffuse effectively through caseum.
To provide simple guidance in the property-based design of new compounds,
a rule of thumb was derived whereby the sum of the hydrophobicity
(clogP) and aromatic ring
count is proportional to caseum binding. These tools can be used to
ensure desirable lesion partitioning and guide the selection of optimal
regimens against tuberculosis
Correction to Absolute Quantitative MALDI Imaging Mass Spectrometry: A Case of Rifampicin in Liver Tissues
Absolute Quantitative MALDI Imaging Mass Spectrometry: A Case of Rifampicin in Liver Tissues
Absolute Quantitative MALDI Imaging Mass Spectrometry: A Case of Rifampicin in Liver Tissues
Matrix-assisted laser
desorption/ionization (MALDI) imaging mass
spectrometry (IMS) elucidates molecular distributions in thin tissue
sections. Absolute pixel-to-pixel quantitation has remained a challenge,
primarily lacking validation of the appropriate analytical methods.
In the present work, isotopically labeled internal standards are applied
to tissue sections to maximize quantitative reproducibility and yield
accurate quantitative results. We have developed a tissue model for
rifampicin (RIF), an antibiotic used to treat tuberculosis, and have
tested different methods of applying an isotopically labeled internal
standard for MALDI IMS analysis. The application of the standard and
subsequently the matrix onto tissue sections resulted in quantitation
that was not statistically significantly different from results obtained
using HPLC-MS/MS of tissue extracts. Quantitative IMS experiments
were performed on liver tissue from an animal dosed <i>in vivo</i>. Each microspot in the quantitative images measures the local concentration
of RIF in the thin tissue section. Lower concentrations were detected
from the blood vessels and around the portal tracts. The quantitative
values obtained from these measurements were comparable (>90% similarity)
to HPLC-MS/MS results obtained from extracts of the same tissue
Design and evaluation of [\ub9\u2078F]CHDI-650 as a positron emission tomography ligand to image mutant Huntingtin aggregates
Design and evaluation of [18F]CHDI-650 as a positron emission tomography ligand to image mutant huntingtin aggregates
Therapeutic interventions are being developed for Huntington's disease (HD), a hallmark of which is mutant huntingtin protein (mHTT) aggregates. Following the advancement to human testing of two [11C]-PET ligands for aggregated mHTT, attributes for further optimization were identified. We replaced the pyridazinone ring of CHDI-180 with a pyrimidine ring and minimized off-target binding using brain homogenate derived from Alzheimer's disease patients. The major in vivo metabolic pathway via aldehyde oxidase was blocked with a 2-methyl group on the pyrimidine ring. A strategically placed ring-nitrogen on the benzoxazole core ensured high free fraction in the brain without introducing efflux. Replacing a methoxy pendant with a fluoro-ethoxy group and introducing deuterium atoms suppressed oxidative defluorination and accumulation of [18F]-signal in bones. The resulting PET ligand, CHDI-650, shows a rapid brain uptake and washout profile in non-human primates and is now being advanced to human testing