DETQ, an allosteric potentiator of the dopamine D1 receptor, was tested in therapeutic models that were known to respond to D1 agonists. Because of a species difference in affinity for DETQ, all rodent experiments used transgenic mice expressing the human D1 receptor (hD1 mice). When given alone, DETQ reversed the locomotor depression caused by a low dose of reserpine. DETQ also acted synergistically with L-DOPA to reverse the strong hypokinesia seen with a higher dose of reserpine. These results indicate potential as both monotherapy and adjunct treatment in Parkinson’s disease. DETQ markedly increased release of both acetylcholine and histamine in the prefrontal cortex, and increased levels of histamine metabolites in the striatum. In the hippocampus, the combination of DETQ and the cholinesterase inhibitor rivastigmine increased ACh to a greater degree than either agent alone. DETQ also increased phosphorylation of the AMPA receptor (GluR1) and the transcription factor CREB in the striatum, consistent with enhanced synaptic plasticity. In the Y-maze, DETQ increased arm entries but (unlike a D1 agonist) did not reduce spontaneous alternation between arms at high doses. DETQ enhanced wakefulness in EEG studies in hD1 mice and decreased immobility in the forced-swim test, a model for antidepressant-like activity. In rhesus monkeys, DETQ increased spontaneous eye-blink rate, a measure that is known to be depressed in Parkinson’s disease. Together, these results provide support for potential utility of D1 potentiators in the treatment of several neuropsychiatric disorders, including Parkinson’s disease, Alzheimer’s disease, cognitive impairment in schizophrenia, and major depressive disorder.

Rudolph J, Svensson KA, Hao J, Li X, Matrisciano F, Meltzer HY. Neuropharmacology. 2018 Jan;128:351-365. doi: 10.1016/j.neuropharm.2017.10.032. Epub 2017 Oct 26.

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Gastric cancer is a fatal disease and the availability of early diagnostic methods is limited. There is an urgent need to identify effective targets for early diagnosis and therapeutics. UbcH10 is a ubiquitin-conjugating enzyme with high expression in various types of cancers. In the present study, several gastric tumor cell lines with high or low expression of UbcH10 were exploited to study the role of UbcH10 in gastric cancer. Knockdown of UbcH10 expression using siRNA in gastric cancer cell lines with high expression of UbcH10 resulted in reduced proliferation, increased cisplatin-induced apoptosis and reduced serum-induced ERK, Akt and p38 phosphorylation signaling. In agreement, overexpression of UbcH10 in gastric cancer cell lines with low expression of UbcH10 led to enhanced cell proliferation and resistance to cisplatin-induced apoptosis. Most importantly, IHC analyses showed that the UbcH10 protein was expressed at a high level in most patient gastric cancer tissues, but was absent in adjacent mesenchyme tissues. These data suggest that UbcH10 may promote gastric cancer growth and can serve as a biomarker for diagnosis or as a target for novel therapeutics in gastric cancer.

Wu X, Zhou H, Hu G. Oncol Rep. 2016 Aug;36(2):779-86. doi: 10.3892/or.2016.4906. Epub 2016 Jun 23.

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p21-activated kinase 1 (PAK1) has an important role in transducing signals in several oncogenic pathways. The concept of inhibiting this kinase has garnered significant interest over the past decade, particularly for targeting cancers associated with PAK1 amplification. Animal studies with the selective group I PAK (pan-PAK1, 2, 3) inhibitor G-5555 from the pyrido[2,3-d]pyrimidin-7-one class uncovered acute toxicity with a narrow therapeutic window. To attempt mitigating the toxicity, we introduced significant structural changes, culminating in the discovery of the potent pyridone side chain analogue G-9791. Mouse tolerability studies with this compound, other members of this series, and compounds from two structurally distinct classes revealed persistent toxicity and a correlation of minimum toxic concentrations and PAK1/2 mediated cellular potencies. Broad screening of selected PAK inhibitors revealed PAK1, 2, and 3 as the only overlapping targets. Our data suggest acute cardiovascular toxicity resulting from the inhibition of PAK2, which may be enhanced by PAK1 inhibition, and cautions against continued pursuit of pan-group I PAK inhibitors in drug discovery.

Rudolph J, Murray LJ, Ndubaku CO, O’Brien T, Blackwood E, Wang W, Aliagas I, Gazzard L, Crawford JJ, Drobnick J, Lee W, Zhao X, Hoeflich KP, Zhang H, Heise CE, Oh A, Ong CC, La H, Chakravarty P, Chan C, Jakubiak D, Epler JE, Ramaswamy S, Vega R, Cain G, Diaz D, Zhong Y. J Med Chem. 2016 Jun 9;59(11):5520-41. doi: 10.1021/acs.jmedchem.6b00638. Epub 2016 May 24.

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Signaling pathways intersecting with the p21-activated kinases (PAKs) play important roles in tumorigenesis and cancer progression. By recognizing that the limitations of FRAX1036 (1) were chiefly associated with the highly basic amine it contained, we devised a mitigation strategy to address several issues such as hERG activity. The 5-amino-1,3-dioxanyl moiety was identified as an effective means of reducing pK a and logP simultaneously. When positioned properly within the scaffold, this group conferred several benefits including potency, pharmacokinetics, and selectivity. Mouse xenograft PK/PD studies were carried out using an advanced compound, G-5555 (12), derived from this approach. These studies concluded that dose-dependent pathway modulation was achievable and paves the way for further in vivo investigations of PAK1 function in cancer and other diseases.

Ndubaku CO, Crawford JJ, Aliagas I, Murray LJ, Tay S, Wang W, Heise CE, Hoeflich KP, La H, Mathieu S, Mintzer R, Ramaswamy S, Rouge L, Rudolph J. Design of Selective PAK1 Inhibitor G-5555: Improving Properties by Employing an Unorthodox Low-pK a Polar Moiety. ACS Med Chem Lett. 2015 Oct 31;6(12):1241-6. doi: 10.1021/acsmedchemlett.5b00398. eCollection 2015 Dec 10.

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Molecular modeling was performed on a triazolo quinazoline lead compound to help develop a series of adenosine A2A receptor antagonists with improved hERG profile. Superposition of the lead compound onto MK-499, a benchmark hERG inhibitor, combined with pKa calculations and measurement, identified terminal fluorobenzene to be responsible for hERG activity. Docking of the lead compound into an A2A crystal structure suggested that this group is located at a flexible, spacious, and solvent-exposed opening of the binding pocket, making it possible to tolerate various functional groups. Transformation analysis (MMP, matched molecular pair) of in-house available experimental data on hERG provided suggestions for modifications in order to mitigate this liability. This led to the synthesis of a series of compounds with significantly reduced hERG activity. The strategy used in the modeling work can be applied to other medicinal chemistry programs to help improve hERG profile.

Deng Q, et al. Bioorg Med Chem Lett. 2015 Aug 1;25(15):2958-62. doi: 10.1016/j.bmcl.2015.05.036. Epub 2015 May 21.

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p21-activated kinase 1 (PAK1) has an important role in transducing signals in several oncogenic pathways. The concept of inhibiting this kinase has garnered significant interest over the past decade, particularly for targeting cancers associated with PAK1 amplification. Animal studies with the selective group I PAK (pan-PAK1, 2, 3) inhibitor G-5555 from the pyrido[2,3-d]pyrimidin-7-one class uncovered acute toxicity with a narrow therapeutic window. To attempt mitigating the toxicity, we introduced significant structural changes, culminating in the discovery of the potent pyridone side chain analogue G-9791. Mouse tolerability studies with this compound, other members of this series, and compounds from two structurally distinct classes revealed persistent toxicity and a correlation of minimum toxic concentrations and PAK1/2 mediated cellular potencies. Broad screening of selected PAK inhibitors revealed PAK1, 2, and 3 as the only overlapping targets. Our data suggest acute cardiovascular toxicity resulting from the inhibition of PAK2, which may be enhanced by PAK1 inhibition, and cautions against continued pursuit of pan-group I PAK inhibitors in drug discovery.

Rudolph J, Murray LJ, Ndubaku CO, O’Brien T, Blackwood E, Wang W, Aliagas I, Gazzard L, Crawford JJ, Drobnick J, Lee W, Zhao X, Hoeflich KP, Zhang H, Heise CE, Oh A, Ong CC, La H, Chakravarty P, Chan C, Jakubiak D, Epler JE, Ramaswamy S, Vega R, Cain G, Diaz D, Zhong Y. J Med Chem. 2016 Jun 9;59(11):5520-41. doi: 10.1021/acs.jmedchem.6b00638. Epub 2016 May 24.

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