Identification of Brain-Penetrant ATP-Competitive mTOR Inhibitors for CNS Syndromes.

The allosteric inhibitor of the mechanistic target of rapamycin (mTOR) everolimus reduces seizures in tuberous sclerosis complex (TSC) patients through partial inhibition of mTOR functions. Due to its limited brain permeability, we sought to develop a catalytic mTOR inhibitor optimized for central nervous system (CNS) indications. We recently reported an mTOR inhibitor (1) that is able to block mTOR functions in the mouse brain and extend the survival of mice with neuronal-specific ablation of the Tsc1 gene. However, 1 showed the risk of genotoxicity in vitro. Through structure-activity relationship (SAR) optimization, we identified compounds 9 and 11 without genotoxicity risk. In neuronal cell-based models of mTOR hyperactivity, both corrected aberrant mTOR activity and significantly improved the survival rate of mice in the Tsc1 gene knockout model. Unfortunately, 9 and 11 showed limited oral exposures in higher species and dose-limiting toxicities in cynomolgus macaque, respectively. However, they remain optimal tools to explore mTOR hyperactivity in CNS disease models.

X-ray Structures and Feasibility Assessment of CLK2 Inhibitors for Phelan-McDermid Syndrome.

CLK2 inhibition has been proposed as a potential mechanism to improve autism and neuronal functions in Phelan-McDermid syndrome (PMDS). Herein, the discovery of a very potent indazole CLK inhibitor series and the CLK2 X-ray structure of the most potent analogue are reported. This new indazole series was identified through a biochemical CLK2 Caliper assay screen with 30k compounds selected by an in silico approach. Novel high-resolution X-ray structures of all CLKs, including the first CLK4 X-ray structure, bound to known CLK2 inhibitor tool compounds (e.g., TG003, CX-4945), are also shown and yield insight into inhibitor selectivity in the CLK family. The efficacy of the new CLK2 inhibitors from the indazole series was demonstrated in the mouse brain slice assay, and potential safety concerns were investigated. Genotoxicity findings in the human lymphocyte micronucleus test (MNT) assay are shown by using two structurally different CLK inhibitors to reveal a major concern for pan-CLK inhibition in PMDS.

Ergoline-derived inverse agonists of the human h3 receptor for the treatment of narcolepsy.

Ergoline derivative (6aR,9R)-4-(2-(dimethylamino)ethyl)-N-phenyl-9-(pyrrolidine-1-carbonyl)-6,6a,8,9-tetrahydroindolo[4,3-fg]quinoline-7(4H)-carboxamide (1), a CXCR3 antagonist, also inhibits human histamine H3 receptors (H3R) and represents a structurally novel H3R inverse agonist chemotype. It displays favorable pharmacokinetic and in vitro safety profiles, and served as a lead compound in a program to explore ergoline derivatives as potential drug candidates for the treatment of narcolepsy. A key objective of this work was to enhance the safety and efficacy profiles of 1, while minimizing its duration of action to mitigate the episodes of insomnia documented with previously reported clinical candidates during the night following administration. Modifications to the ergoline core at positions 1, 6 and 8 were systematically investigated, and derivative 23 (1-((4aR,8R,9aR)-8-(hydroxymethyl)-1-(2-((R)-2-methylpyrrolidin-1-yl)ethyl)-4,4a,7,8,9,9a-hexahydroindolo[1,14-fg]quinolin-6(1H)-yl)ethanone) was identified as a promising lead compound. Derivative 23 has a desirable pharmacokinetic profile and demonstrated efficacy by enhancing brain concentrations of tele-methylhistamine, a major histamine metabolite. This validates the potential of the ergoline scaffold to serve as a template for the development of H3R inverse agonists.

Macrocyclic BACE-1 inhibitors acutely reduce Abeta in brain after po application.

A series of macrocyclic peptidic BACE-1 inhibitors was designed. While potency on BACE-1 was rather high, the first set of compounds showed poor brain permeation and high efflux in the MDRI-MDCK assay. The replacement of the secondary benzylamino group with a phenylcyclopropylamino group maintained potency on BACE-1, while P-glycoprotein-mediated efflux was significantly reduced and brain permeation improved. Several compounds from this series demonstrated acute reduction of Abeta in human APP-wildtype transgenic (APP51/16) mice after oral administration.

Synthesis of (+/-)-strychnofoline via a highly convergent selective annulation reaction.

Studies aimed at preparing (+/-)-strychnofoline by total synthesis are detailed. The route described makes use of a recently developed MgI(2)-mediated ring-expansion reaction of spiro[cyclopropan-1,3'-oxindole] with a cyclic disubstituted aldimine. The ring-expansion product was formed as a single diastereoisomer in 55 % yield, possessing the same stereochemical pattern found in strychnofoline. In addition, our synthetic effort has led to the development of new reaction methodology to access 3,4-disubstituted cyclic aldimines.

Highly enantioselective conjugate additions to alpha,beta-unsaturated ketones catalyzed by a (salen)Al complex.

Chiral (salen)Al complex 1a catalyzes the highly enantioselective conjugate addition of carbon- and nitrogen-based nucleophiles to acyclic alpha,beta-unsaturated ketones. This methodology is tolerant of substantial variation of the ketone structure, providing access to a wide range of useful chiral building blocks in high yield and enantiomeric excess. Synthetic manipulations of the conjugate addition products are demonstrated, including the straightforward preparation of beta-amino ketones and highly enantioenriched carbo- and heterocyclic compounds.

First total synthesis of (+/-)-strychnofoline via a highly selective ring-expansion reaction.

An efficient synthesis of the antitumor alkaloid (+/-)-strychnofoline is documented. Key to the development of the highly convergent strategy delineated is the coupling of a cyclic imine with spiro[cyclopropan-1,3'-oxindole], which takes place in a highly diastereoselective manner. The ability to conduct annulation reactions of spirocyclopropyloxindoles with functionalized cyclic imines provides new avenues for the preparation of this important class of biologically active structures.