Isolation, identification and characterization of potential impurities in cabazitaxel and their formation

Rhodamines with a Chloronicotinic Acid Fragment for Live Cell Superresolution STED Microscopy*

Formylation of 2,6-dichloro-5-R-nicotinic acids at C-4 followed by condensation with 3-hydroxy-N,N-dimethylaniline gave analogs of the popular TAMRA fluorescent dye with a 2,6-dichloro-5-R-nicotinic acid residues (R=H, F). The following reaction with thioglycolic acid is selective, involves only one chlorine atom at the carbon between pyridine nitrogen and the carboxylic acid group and affords new rhodamine dyes absorbing at 564/ 573 nm and emitting at 584/ 597 nm (R=H/ F, in aq. PBS). Conjugates of the dyes with "small molecules" provided specific labeling (covalent and non-covalent) of organelles as well as of components of the cytoskeleton in living cells and were combined with fluorescent probes prepared from 610CP and SiR dyes and applied in two-color STED microscopy with a 775 nm STED laser.

Degradation Pathway of a Taxane Derivative DS80100717 Drug Substance and Drug Product

The degradation pathway of a taxane derivative and anticancer agent, DS80100717, was investigated. Several degradants were generated under acidic, basic, and oxidative stress conditions in solution. The chemical structures of eight degradants of DS80100717 were elucidated using MS and NMR. The major degradant of the DS80100717 drug substance derived by heating in solid-state was the N-oxide form via oxidation and C2'-epimer of the side chain via acid hydrolysis. We proposed previously unreported degradation pathways of DS80100717 with taxane derivatives such as paclitaxel, docetaxel, and cabazitaxel.

Green-Emitting Rhodamine Dyes for Vital Labeling of Cell Organelles Using STED Super-Resolution Microscopy

Fluorescence microscopy reveals the localization, spatial distribution, and temporal dynamics of the specifically labeled organelles in living cells. Labeling with exogenous conjugates prepared from fluorescent dyes and small molecules (ligands) is an attractive alternative to the use of fluorescent proteins, but proved to be challenging due to insufficient cell-permeability of the probes, unspecific staining, or low dye brightness. We evaluated four green-emitting rhodamine dyes and their conjugates intended for the specific labeling of lysosomes, mitochondria, tubulin, and actin in living cells. The imaging performance of the probes in living human fibroblasts has been studied by using confocal and stimulated emission depletion (STED) super-resolution microscopy with a commercial 595 nm STED laser. Two bright and photostable dyes (LIVE 510 and LIVE 515) provide specific and versatile staining.

Two-Color 810 nm STED Nanoscopy of Living Cells with Endogenous SNAP-Tagged Fusion Proteins

A 810 nm STED nanoscopy setup and an appropriate combination of two fluorescent dyes (Si-rhodamine 680SiR and carbopyronine 610CP) have been developed for near-IR live-cell super-resolution imaging. Vimentin endogenously tagged using the CRISPR/Cas9 approach with the SNAP tag, together with a noncovalent tubulin label, provided reliable and cell-to-cell reproducible dual-color confocal and STED imaging of the cytoskeleton in living cells.