Solid-phase synthesis for thalidomide-based proteolysis-targeting chimeras (PROTAC)

A preloaded resin consisting of a thalidomide moiety and an ethylene-oxy linker allows the simple and fast formation of PROTACs. The feasibility of the procedure was illustrated by conjugating different protein kinase inhibitors. The biological functionality of an ibrutinib-like conjugate was then confirmed by a cellular experiment.

Anti-angiogenic effects of novel cyclin-dependent kinase inhibitors with a pyrazolo[4,3-d]pyrimidine scaffold

BACKGROUND AND PURPOSE

Cyclin-dependent kinase 5 (CDK5) has recently emerged as an attractive target in several tumour entities. Inhibition of CDK5 has been shown to have anti-angiogenic effects in vitro and in vivo. However, potent inhibitors of CDK5, which can be applied in vivo, are still scarce. We have recently developed a new series of 5-substituted 3-isopropyl-7-[4-(2-pyridyl)benzyl]amino-1(2)H-pyrazolo[4,3-d]pyrimidines that show a preference for inhibiting CDK5 and tested them in vitro and in vivo in a murine model of hepatocellular carcinoma.

EXPERIMENTAL APPROACH

All compounds were initially examined for effects on proliferation of HUVECs. The most potent compounds were then tested on migration, and one of them, LGR2674, was selected for assessing effects on nuclear fragmentation, cell cycle, cell viability and metabolic activity. Furthermore, LGR2674 was tested in a tube formation assay and in vivo in a murine model of hepatocellular carcinoma, induced by s.c. injection of HUH7 cells (measurement of in vivo toxicity, tumour vascularization, tumour cell proliferation and tumour size).

KEY RESULTS

LGR2674 showed an EC50 in the low nanomolar range in the proliferation and migration assays. Cytotoxic effects started at 50 nM, a concentration that did not influence the cell cycle. In vivo, LGR2674 was well tolerated and caused a clear reduction in vessel density in the tumours; also tumour cell proliferation was inhibited and tumour growth retarded.

CONCLUSIONS AND IMPLICATIONS

Pyrazolo[4,3-d]pyrimidine is a novel scaffold for the development of potent CDK inhibitors with in vivo potential. Such structures are good candidates for broadening our pharmacological arsenal against various tumours.

Effects of N-acetylcysteine on tissue oxygenation in patients with multiple organ failure and evidence of tissue hypoxia

Covert tissue hypoxia, particularly of the splanchnic region, appears important in the pathogenesis of multiple organ failure (MOF). This investigation evaluates the effects of N-acetylcysteine (NAC) upon several measures of tissue oxygenation in 10 patients with severe MOF and evidence of splanchnic hypoxia (as suggested by a pathologically low value (< 7.32) of the pH of the gastric mucosa (pHi)). Patients were studied following a prospective, randomized, placebo-controlled, cross-over design. Measurements included pulmonary and systemic haemodynamics, cardiac output by thermodilution, arterial and mixed venous blood gas values, blood lactate concentration, whole-body oxygen uptake by analysis of the expired gases, and pHi by tonometry. A complete set of measurements was obtained before and 45 min after the infusion of NAC (150 mg.kg-1 in 250 mL of saline) and, also, before and 45 min after the infusion of an equivalent volume of saline. NAC increased the cardiac index and vasodilated the systemic circulation (p < 0.01). However, O2 delivery to the tissues did not increase because the arterial oxygen content fell after NAC (p < 0.01). Mean O2 extraction or lactate concentration did not change after NAC, and pHi fell slightly (from 7.11 +/- 0.21 to 7.07 +/- 0.21; p < 0.05). The infusion of saline did not modify any variable significantly. The O2 extraction fraction increased exponentially in those patients with reduced O2 transport to the tissues. These results argue against a beneficial effect of N-acetylcysteine upon tissue oxygenation in patients with severe multiple organ failure and evidence of splanchnic hypoxia. Furthermore, they suggest that the mechanisms controlling the extraction of oxygen by the peripheral tissues in these patients were not impaired.