Tissue oxygenation plays an important role in the pathophysiology of various diseases and is often a marker of prognosis and therapeutic response. EPR (ESR) is a suitable noninvasive oximetry technique. However, to reliably deploy soluble EPR probes as oxygen sensors in complex biological systems, there is still a need to investigate and improve their specificity, sensitivity, and stability. We reproducibly synthesized various derivatives of tetrathiatriarylmethyl and tetrachlorotriarylmethyl (trityl) radicals. Hydrophilic radicals were investigated in aqueous solution mimicking physiological conditions by, e.g., variation of viscosity and ionic strength. Their specificity was satisfactory, but the oxygen sensitivity was low. To enhance the capability of trityl radicals as oxygen sensors, encapsulation into oily core nanocapsules was performed. Thus, different lipophilic triesters were prepared and characterized in oily solution employing oils typically used in drug formulations, i.e., middle-chain triglycerides and isopropyl myristate. Our screening identified the deuterated ethyl ester of D-TAM (radical 13) to be suitable. It had an extremely narrow single EPR line under anoxic conditions and excellent oxygen sensitivity. After encapsulation, it retained its oxygen responsiveness and was protected against reduction by ascorbic acid. These biocompatible and highly sensitive nanosensors offer great potential for future EPR oximetry applications in preclinical research.

A hydrophilic tris(tetrachlorotriaryl)methyl (tetrachloro-TAM) radical labelled 50% with C at the central carbon atom was prepared. The mixture of isotopologue radicals was characterised by continuous wave and pulsed X-band electron paramagnetic spectroscopy (EPS). For the pharmaceutical and medical applications planned, the quantitative influence of oxygen, viscosity, temperature and pH on EPR line widths was studied in aqueous buffer, DMSO, water-methanol and water-glycerol mixtures. Under in vivo conditions, pH can be disregarded. There is a clear oxygen dependence of the width of theC isotopologue single EPR line in aqueous solutions while changes in rotational motion (viscosity) are observable only in the doublet lines of the central carbon of the C isotopologue. The tetrachloro-TAM proved to be very stable as a solid. Its thermal decay was determined quantitatively by thermal annealing. Towards ascorbic acid as a reducing agent and towards an oocyte cell extract it had a half-life of approx. 60 and 10 min. Thus for in vivo applications, 50%C tetrachloro-TAMs are suitable for selective and simultaneous oxygen and macroviscosity measurements in a formulation, e.g. nanocapsules.

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A series of pyridothieno[3,2-d]pyrimidin-4-amines was designed and synthesized as congeners to the classical 4-anilinoquinazolines as ATP-competitive epidermal growth factor receptor (EGFR) inhibitors.Compound 5a exhibited the most potent and selective inhibitory activity against EGFR with an IC 50 value of 36.7 nM. Moreover, compounds 4b and 5a showed remarkable cell growth inhibition against leukemia, central nervous system cancer, and non-small cell lung cancer cell lines that overexpress EGFR, with growth inhibition of 50% (GI 50 ) values of around 10 nM in the full U.S. National Cancer Institute 60 cell panel assay. Cell cycle studies indicated that compounds 4b and 5a induced significant cell cycle arrest in the S-phase and G0/G1, respectively, in addition to boosting P27 kip expression. Compound 5a did not alter the viability of placental trophoblasts, which reflects its safety for normal cells. The standard COMPARE analyses demonstrated considerable correlation levels between compounds 4b and 5a and erlotinib, with pyridinium chlorochromate (PCC) values of 0.707 and 0.727, respectively. Key words pyridothieno[3,2-d]pyrimidine; epidermal growth factor receptor (EGFR); inhibitorThe epidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase (RTK) that plays a vital role in signaling pathways that regulate cellular growth, proliferation and survival.1) Such signaling pathways are triggered by a tightly regulated protein phosphorylation reaction. This reaction is initiated with the binding of the epidermal growth factor (EGF) to the extracellular domain of EGFR leading to the activation of its intrinsic kinase domain. The latter has the ability to activate proteins by removing phosphate groups from ATP and covalently binding them to tyrosine substrates of the proteins.2) Deregulation of this controlled pathway, through overexpression and/or mutation of EGFR, contributes to the malignant transformations of normal cells. Overexpression of EGFR has been observed in a large number of human cancers including breast, prostate, ovarian, colorectal, kidney, brain and non-small cell lung cancers. 3,4)Examples of clinically approved ATP-competitive EGFR inhibitors including gefitinib, lapatinib and erlotinib, are structurally based on a central 4-anilinoquinazoline scaffold 5) (Fig. 1). However the emerging resistance of cancer cells to current medicines derives our passion to search for novel congeners to the 4-anilinoquinazoline scaffold as a beached for cancer therapy.6,7) Structure-activity relationship studies of 4-anilinoquinazolinederivatives revealed that the quinazoline core fits into the ATP-competitive pocket of EGFR. 8,9) Consistent with this, some investigations showed that the isosteric replacement of the benzene ring of the quinazoline core with five-membered heteroaromatic rings is favorable.10,11) The flexibility of the linking NH group between the heteroaryl core and the aniline ring permits the proper orientation of the aniline ring into the hydrophobic pocket, lying in the b...