Efficient synthesis of [11C]H-1152, a PET probe specific for Rho-kinases, highly potential targets in diagnostic medicine and drug development

Emerging targets in drug discovery against neurodegenerative diseases: Control of synapsis disfunction by the RhoA/ROCK pathway

Synaptic spine morphology is controlled by the activity of Rac1, Cdc42 and RhoA, which need to be finely balanced, and in particular RhoA/ROCK prevents the formation of new protrusions by stabilizing actin formation. These processes are crucial to the maturation process, slowing the de novo generation of new spines. The RhoA/ROCK also influences plasticity processes, and selective modulation by ROCK1 of MLC-dependent actin dynamics leads to neurite retraction, but not to spine retraction. ROCK1 is also responsible for the reduction of the readily releasable pool of synaptic vesicles. These and other evidences suggest that ROCK1 is the main isoform acting on the presynaptic neuron. On the other hand, ROCK2 seems to have broad effects on LIMK/cofilin-dependent plasticity processes such as cofilin-dependent PSD changes. The RhoA/ROCK pathway is an important factor in several different brain-related pathologies via both downstream and upstream pathways. In the aggregate, these evidences show that the RhoA/ROCK pathway has a central role in the etiopathogenesis of a large group of CNS diseases, which underscores the importance of the pharmacological modulation of RhoA/ROCK as an important pathway to drug discovery in the neurodegenerative disease area. This article aims at providing the first review of the role of compounds acting on the RhoA/ROCK pathway in the control of synaptic disfunction.

Discovery of Novel N-Substituted Prolinamido Indazoles as Potent Rho Kinase Inhibitors and Vasorelaxation Agents

Inhibitors of Rho kinase (ROCK) have potential therapeutic applicability in a wide range of diseases, such as hypertension, stroke, asthma and glaucoma. In a previous article, we described the lead discovery of DL0805, a new ROCK I inhibitor, showing potent inhibitory activity (IC50 6.7 μM). Herein, we present the lead optimization of compound DL0805, resulting in the discovery of 24- and 39-fold more-active analogues 4a (IC50 0.27 μM) and 4b (IC50 0.17 μM), among other active analogues. Moreover, ex-vivo studies demonstrated that 4a and 4b exhibited comparable vasorelaxant activity to the approved drug fasudil in rat aortic rings. The research of a preliminary structure-activity relationship (SAR) indicated that the target compounds containing a β-proline moiety have improved activity against ROCK I relative to analogues bearing an α-proline moiety, and among the series of the derivatives with a β-proline-derived indazole scaffold, the inhibitory activity of the target compounds with a benzyl substituent is superior to those with a benzoyl substituent.

Synthesis of PET probe O6-[(3-[11C]methyl)benzyl]guanine by Pd0-mediated rapid C-[11C]methylation toward imaging DNA repair protein O6-methylguanine-DNA methyltransferase in glioblastoma

O⁶-Benzylguanine (O⁶-BG) is a substrate of O⁶-methylguanine-DNA methyltransferase (MGMT), which is involved in drug resistance of chemotherapy in the majority of glioblastoma multiform. For clinical diagnosis, it is hoped that the MGMT expression level could be determined by a noninvasive method to understand the detailed biological properties of MGMT-specific tumors. We synthesized ¹¹C-labeled O⁶-[(3-methyl)benzyl]guanine ([¹¹C]mMeBG) as a positron emission tomography probe. Thus, a mixed amine-protected stannyl precursor, N⁹-(tert-butoxycarbonyl)-O⁶-[3-(tributylstannyl)benzyl]-N²-(trifluoroacetyl)guanine, was subjected to rapid C-[¹¹C]methylation under [¹¹C]CH₃I/[Pd₂(dba)₃]/P(o-CH₃C₆H₄)₃/CuCl/K₂CO₃ in NMP, followed by quick deprotection with LiOH/H₂O, giving [¹¹C]mMeBG with total radioactivity of 1.34GBq and ≥99% radiochemical and chemical purities.

Small Molecule Radiopharmaceuticals - A Review of Current Approaches

Radiopharmaceuticals are an integral component of nuclear medicine and are widely applied in diagnostics and therapy. Though widely applied, the development of an “ideal” radiopharmaceutical can be challenging. Issues such as specificity, selectivity, sensitivity, and feasible chemistry challenge the design and synthesis of radiopharmaceuticals. Over time, strategies to address the issues have evolved by making use of new technological advances in the fields of biology and chemistry. This review presents the application of few advances in design and synthesis of radiopharmaceuticals. The topics covered are bivalent ligand approach and lipidization as part of design modifications for enhanced selectivity and sensitivity and novel synthetic strategies for optimized chemistry and radiolabeling of radiopharmaceuticals.

Recent Advances in the Development and Application of Radiolabeled Kinase Inhibitors for PET Imaging

Over the last 20 years, intensive investigation and multiple clinical successes targeting protein kinases, mostly for cancer treatment, have identified small molecule kinase inhibitors as a prominent therapeutic class. In the course of those investigations, radiolabeled kinase inhibitors for positron emission tomography (PET) imaging have been synthesized and evaluated as diagnostic imaging probes for cancer characterization. Given that inhibitor coverage of the kinome is continuously expanding, in vivo PET imaging will likely find increasing applications for therapy monitoring and receptor density studies both in- and outside of oncological conditions. Early investigated radiolabeled inhibitors, which are mostly based on clinically approved tyrosine kinase inhibitor (TKI) isotopologues, have now entered clinical trials. Novel radioligands for cancer and PET neuroimaging originating from novel but relevant target kinases are currently being explored in preclinical studies. This article reviews the literature involving radiotracer design, radiochemistry approaches, biological tracer evaluation and nuclear imaging results of radiolabeled kinase inhibitors for PET reported between 2010 and mid-2015. Aspects regarding the usefulness of pursuing selective vs. promiscuous inhibitor scaffolds and the inherent challenges associated with intracellular enzyme imaging will be discussed.

Synthesis of 1- and 4-substituted piperazin-2-ones via Jocic-type reactions with N-substituted diamines

Enantiomerically-enriched trichloromethyl-containing alcohols are transformed regioselectively into enantiomerically-enriched 1-substituted piperazinones by modified Jocic reactions.