Novel triazines as potent and selective phosphodiesterase 10A inhibitors.

The identification of highly potent and orally active triazines for the inhibition of PDE10A is reported. The new analogs exhibit low-nanomolar potency for PDE10A, demonstrate high selectivity against all other members of the PDE family, and show desired drug-like properties. Employing structure-based drug design approaches, we investigated the selectivity of PDE10A inhibitors against other known PDE isoforms, by methodically exploring the various sub-regions of the PDE10A ligand binding pocket. A systematic assessment of the ADME and pharmacokinetic properties of the newly synthesized compounds has led to the design of drug-like candidates with good brain permeability and desirable drug kinetics (t(1/2), bioavailability, clearance). Compound 66 was highly potent for PDE10A (IC(50)=1.4 nM), demonstrated high selectivity (>200×) for the other PDEs, and was efficacious in animal models of psychoses; reversal of MK-801 induced hyperactivity (MED=0.1mg/kg) and conditioned avoidance responding (CAR; ID(50)=0.2 mg/kg).

Highly potent, selective, and orally active phosphodiesterase 10A inhibitors.

The identification of highly potent and orally active phenylpyrazines for the inhibition of PDE10A is reported. The new analogues exhibit subnanomolar potency for PDE10A, demonstrate high selectivity against all other members of the PDE family, and show desired druglike properties. Employing structure-based drug design approaches, we methodically explored two key regions of the binding pocket of the PDE10A enzyme to alter the planarity of the parent compound 1 and optimize its affinity for PDE10A. Bulky substituents at the C9 position led to elimination of the mutagenicity of 1, while a crucial hydrogen bond interaction with Glu716 markedly enhanced its potency and selectivity. A systematic assessment of the ADME and PK properties of the new analogues led to druglike development candidates. One of the more potent compounds, 96, displayed an IC(50) for PDE10A of 0.7 nM and was active in predictive antipsychotic animal models.

Optimization of a serum-free culture medium for mouse embryonic stem cells using design of experiments (DoE) methodology.

The in vitro culture behaviour of embryonic stem cells (ESC) is strongly influenced by the culture conditions. Current culture media for expansion of ESC contain some undefined substances. Considering potential clinical translation work with such cells, the use of defined media is desirable. We have used Design of Experiments (DoE) methods to investigate the composition of a serum-free chemically defined culture medium for expansion of mouse embryonic stem cells (mESC). Factor screening analysis according to Plackett-Burman revealed that insulin and leukaemia inhibitory factor (LIF) had a significant positive influence on the proliferation activity of the cells, while zinc and L: -cysteine reduced the cell growth. Further analysis using minimum run resolution IV (MinRes IV) design indicates that following factor adjustment LIF becomes the main factor for the survival and proliferation of mESC. In conclusion, DoE screening assays are applicable to develop and to refine culture media for stem cells and could also be employed to optimize culture media for human embryonic stem cells (hESC).

Discovery of imidazo[1,5-a]pyrido[3,2-e]pyrazines as a new class of phosphodiesterase 10A inhibitiors.

Novel imidazo[1,5-a]pyrido[3,2-e]pyrazines have been synthesized and characterized as both potent and selective phosphodiesterase 10A (PDE10A) inhibitors. For in vitro characterization, inhibition of PDE10A mediated cAMP hydrolysis was used and a QSAR model was established to analyze substitution effects. The outcome of this analysis was complemented by the crystal structure of PDE10A in complex with compound 49. Qualitatively new interactions between inhibitor and binding site were found, contrasting with previously published crystal structures of papaverine-like inhibitors. In accordance with the known antipsychotic potential of PDE10A inhibitors, MK-801 induced stereotypy and hyperactivity in rats were reversed by selected compounds. Thus, a promising compound class has been identified for the treatment of schizophrenia that could circumvent side effects connected with current therapies.