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Human serine racemase (hSR) catalyses racemisation of L-serine to D-serine, the latter of which is a co-agonist of the NMDA subtype of glutamate receptors that are important in synaptic plasticity, learning and memory. In a ‘closed’ hSR structure containing the allosteric activator ATP, the inhibitor malonate is enclosed between the large and small domains while ATP is distal to the active site, residing at the dimer interface with the Tyr121 hydroxyl group contacting the ATP a-phosphate. In contrast, in ‘open’ hSR structures, Tyr121 sits in the core of the small domain with its hydroxyl contacting the key catalytic residue Ser84. The ability to regulate SR activity by flipping Tyr121 from the core of the small domain to the dimer interface appears to have evolved in animals with a CNS. Multiple X-ray crystallographic enzymefragment structures show that Tyr121 is flipped out of its pocket, suggesting that this pocket is druggable.

The neurotransmitter glutamate and its receptors have long been of interest to scientists involved in pharmaceutical research since dysfunction of the glutamatergic signalling pathway has been associated with the pathophysiology of\ud several psychiatric and neurological disorders. The research on AMPAR positive allosteric modulators offers opportunities to modulate fast excitatory synaptic transmission and identify new potential therapeutic agents for a range of neurodiseases. The field of AMPAR modulators continues to be a dynamic area of drug discovery with a pronounced diversification of the chemotypes explored in recent\ud years. This article reviews literature published in this area in the last 6 years, focusing on the new core templates, some derived from high-throughput screens, with an emphasis on structure-activity relationships, drug metabolism and pharmacokinetics properties, and pharmacological profiles of these series.

New tools are required to ensure the adequate control of the neglected tropical disease human African trypanosomiasis. Annual reports of infection have recently fallen to fewer than 5000 cases per year; however, current therapies are hard to administer and have safety concerns and, hence, are far from ideal. Trypanosome alternative oxidase is an exciting target for controlling the infection; it is unique to the parasite, and inhibition of this enzyme with the natural product ascofuranone has shown to clear in vivo infections. We report the synthesis and associated structure activity relationships of inhibitors based upon this natural product with correlation to T. b. brucei growth inhibition in an attempt to generate molecules that possess improved physicochemical properties and potential for use as new treatments for human African trypanosomiasis.

African trypanosomiasis is a parasitic disease affecting 5000 humans and millions of livestock animals in sub-Saharan Africa every year. Current treatments are limited, difficult to administer and often toxic causing long term injury or death in many patients. Trypanosome alternative oxidase is a parasite specific enzyme whose inhibition by the natural product ascofuranone (AF) has been shown to be curative in murine models. Until now synthetic methods to AF analogues have been limited, this has restricted both understanding of the key structural features required for binding and also how this chemotype could be developed to an effective therapeutic agent. The development of 3 amenable novel synthetic routes to ascofuranone-like compounds is described. The SAR generated around the AF chemotype is reported with correlation to the inhibition of T. b. brucei growth and corresponding selectivity in cytotoxic assessment in mammalian HepG2 cell lines. These methods allow access to greater synthetic diversification and have enabled the synthesis of compounds that have and will continue to facilitate further optimisation of the AF chemotype into a drug-like lead., Graphical abstract Image 1, Highlights • Synthesis of ascofuranone like inhibitors of trypanosome alternative oxidase. • Structure activity relationships of trypanosome alternative oxidase inhibitors. • Correlation of trypanosome alternative oxidase inhibition and T. b. brucei growth.

Aminoglycoside antibiotics are widely used for the treatment of life-threatening bacterial infections, but cause permanent hearing loss in a substantial proportion of treated patients. The sensory hair cells of the inner ear are damaged following entry of these antibiotics via the mechano-electrical transducer (MET) channels located at the tips of the hair cell’s stereocilia. d-Tubocurarine (dTC) is a MET channel blocker that reduces the loading of gentamicin-Texas Red (GTTR) into rat cochlear hair cells and protects them from gentamicin treatment. Berbamine is a structurally related alkaloid that reduces GTTR labeling of zebrafish lateral-line hair cells and protects them from aminoglycoside-induced cell death. Both compounds are thought to reduce aminoglycoside entry into hair cells through the MET channels. Here we show that dTC (≥6.25 µM) or berbamine (≥1.55 µM) protect zebrafish hair cells in vivo from neomycin (6.25 µM, 1 h). Protection of zebrafish hair cells against gentamicin (10 µM, 6 h) was provided by ≥25 µM dTC or ≥12.5 µM berbamine. Hair cells in mouse cochlear cultures are protected from longer-term exposure to gentamicin (5 µM, 48 h) by 20 µM berbamine or 25 µM dTC. Berbamine is, however, highly toxic to mouse cochlear hair cells at higher concentrations (≥30 µM) whilst dTC is not. The absence of toxicity in the zebrafish assays prompts caution in extrapolating results from zebrafish neuromasts to mammalian cochlear hair cells. MET current recordings from mouse outer hair cells (OHCs) show that both compounds are permeant open-channel blockers, rapidly and reversibly blocking the MET channel with half-blocking concentrations of 2.2 µM (dTC) and 2.8 µM (berbamine) in the presence of 1.3 mM Ca2+ at −104 mV. Berbamine, but not dTC, also blocks the hair cell’s basolateral K + current, IK,neo, and modeling studies indicate that berbamine permeates the MET channel more readily than dTC. These studies reveal key properties of MET-channel blockers required for the future design of successful otoprotectants.

Topoisomerase 1 (TOP1) generates transient nicks in the DNA to relieve torsional stress encountered during the cellular processes of transcription, replication, and recombination. At the site of the nick there is a covalent linkage of TOP1 with DNA via a tyrosine residue. This reversible TOP1-cleavage complex intermediate can become trapped on DNA by TOP1 poisons such as camptothecin, or by collision with replication or transcription machinery, thereby causing protein-linked DNA single- or double-strand breaks and resulting in cell death. Tyrosyl-DNA phosphodiesterase 1 (TDP1) is a key enzyme involved in the repair of TOP1-associated DNA breaks via hydrolysis of 3′-phosphotyrosine bonds. Inhibition of TDP1 is therefore an attractive strategy for targeting cancer cells in conjunction with TOP1 poisons. Existing methods for monitoring the phosphodiesterase activity of TDP1 are generally gel based or of high cost. Here we report a novel, oligonucleotide-based fluorescence assay that is robust, sensitive, and suitable for high-throughput screening of both fragment and small compound libraries for the detection of TDP1 inhibitors. We further validated the assay using whole cell extracts, extending its potential application to determine of TDP1 activity in clinical samples from patients undergoing chemotherapy.

A novel approach of the convergent functionalisation of aryl dibromides to form NS5A type inhibitors using C–H activation is reported. The focus of investigation was to reduce the formation of homodimeric side product, as well as to investigate the scope of different aryl dibromides that were tolerated under the reaction conditions. The C–H activation methodology was found to give a viable synthetic route to NS5A inhibitors, with late stage functionalisation of the core portion of the molecule, albeit with some chemical functionalities not tolerated.

A series of novel AMPA receptor positive modulators displaying CNS penetration have been discovered with sub-micromolar activity and good selectivity over the cardiac channel receptor, hERG. We describe here the synthesis of these compounds which are biaryl pyrrolidine and tetrahydrofuran sulfonamides and disclose their activities against the human GluA2 flip isoform homotetrameric receptor.

The (-)-(11R,2'S)-enantiomer of the antimalarial drug mefloquine has been found to be a reasonably potent and moderately selective adenosine A(2A) receptor antagonist. Further investigation of this compound has led to the discovery of a series of keto-aryl thieno[3,2-d]pyrimidine derivatives, which are potent and selective antagonists of the adenosine A(2A) receptor. These derivatives show selectivity against the A(1) receptor. Furthermore, some of these compounds have been shown to have in vivo activity in a commonly used model, suggesting the potential for the treatment of Parkinson's disease.

Helicases are enzymes that unwind DNA or RNA. As a result, they are described as ‘guardians of the genome’ and play roles in key processes such as DNA replication, RNA transcription, translation, DNA repair and DNA recombination. Certain helicases have also been implicated in the DNA damage response (DDR) and with an increasing interest growing in these enzymes, more helicases are likely to be implicated in DNA damage repair as understanding grows. Targeting proteins involved in DDR has recently gained promise as a selective chemotherapeutic strategy due to the high level of genomic instability in cancer cells. One of these helicases, Bloom syndrome protein (BLM), is particularly implicated in homologous recombination (HR), a key pathway in the repair of double strand breaks. The role of BLM in DNA repair and its complex interactions with key proteins in these networks suggest it may be a good chemotherapeutic target. The first BLM helicase inhibitor to be characterised was ML216. However, ML216 does not seem to be highly specific to BLM as it also inhibits DNA unwinding of the closely related WRN helicase. Furthermore, the poor solubility and permeability of this series which would prevent reliable in-vitro data from being generated. Potent and selective inhibitors targeting BLM helicase can increase understanding of its function in human cells and role and relevance in DNA damage repair. Furthermore, the tool can also be used in synthetic lethality screens to assess the potential of BLM inhibition as a chemotherapeutic option. As a result, the discovery of a novel series of potent and selective BLM inhibitors with improved physiochemical properties were sought. In this work, 672 active hits of the NIH Molecular Libraries Small Molecule Repository (MLSMR) qHTS screen on BLM helicase, which have been deposited in the PubChem BioAssay database [AID2386], were analysed and 10 series were selected for in-house testing on a BLM helicase unwinding assay. This led to the medicinal chemistry investigation of a single series that is relatively potent compared to inhibitors of other human helicases. Efforts have been undertaken to establish primary SAR and to improve the activity of the compound to Citation Format: Yusuf Ali, Xiangrong Chen, Simon Ward, Frances Pearl. Design, synthesis and evaluation of a novel series of BLM helicase inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3238. doi:10.1158/1538-7445.AM2017-3238

A novel series of AMPAR positive modulators is described that were identified by high throughput screening. The molecules of the series have been optimized from a high quality starting point hit to afford excellent developability, tolerability, and efficacy profiles, leading to identification of a clinical candidate. Unusually for an ion channel target, this optimization was integrated with regular generation of ligand-bound crystal structures and uncovered a novel chemotype with a unique and highly conserved mode of interaction via a trifluoromethyl group.

A series of AMPA receptor positive allosteric modulators has been optimized from poorly penetrant leads to identify molecules with excellent preclinical pharmacokinetics and CNS penetration. These discoveries led to 17i, a potent, efficacious CNS penetrant molecule with an excellent pharmacokinetic profile across preclinical species, which is well tolerated and is also orally bioavailable in humans.

The carbocyclic analogue 11 of nikkomycin C 1 is prepared by a sequence involving allylic rearrangement of the imino ester adduct 3, palladium-mediated substitution of the allylic lactone 4c with uracil bis(trimethylsilyl)ether 6, and osmylation of the double bond.

A series of 5-(piperidinylethyloxy)quinoline 5-HT(1) receptor ligands have been studied by elaboration of the series of dual 5-HT(1)-SSRIs reported previously. These new compounds display a different in vitro pharmacological profile with potent affinity across the 5-HT(1A), 5-HT(1B) and 5-HT(1D) receptors and selectivity against the serotonin transporter. Furthermore, they have improved pharmacokinetic profiles and CNS penetration.

Investigation of halogen substitution in lead compound 1 has led to the identification of analogues which combine high affinity for 5-HT(1A) receptors and potent serotonin reuptake inhibitory activity. Several compounds show an improved selectivity over 5-HT(1B) and 5-HT(1D) receptors and a superior pharmacokinetic profile in the rat.

Bridgehead lithiations have successfully been carried out on substrates derived from catechinic acid, which possess the core bicyclo[3.3.1]nonane-1,3,5-trione structure present in garsubellin A. Using an external quench method, various electrophiles have been incorporated at the C-5 bridgehead position in a one-step process that appears to be sensitive to the substitution pattern on the bicyclic system. Regioselective lithiation at the C-3 sp(2) centre was achieved by changing the base used from LDA to LTMP. Following the introduction of a prenyl substituent by bridgehead substitution, annulation of a THF ring, analogous to that in garsubellin A, was possible via an epoxidation-ring opening sequence. Oxidative modification of the catechol substituent of the catechinic acid core was possible to give systems with muconic acid, ortho-quinone or furan 2-carboxylic acid side chains.

The carbocyclic analogue 11 of nikkomycin C 1 is prepared by a sequence involving allylic rearrangement of the imino ester adduct 3, palladium-mediated substitution of the allylic lactone 4c with uracil bis(trimethylsilyl)ether 6, and osmylation of the double bond.

A novel route to the synthesis of 3-(tolylsulfonyl)-4,5-cis-disubstituted gamma-lactams using a diastereoselective palladium-catalysed intramolecular allylation of amino acid-derived allylic carbonates has been developed.

An efficient and convenient method for the removal of benzyl ether protecting groups in the presence of other functionality has been developed. The method is sufficiently mild to allow the removal of trityl groups in the presence of benzyl ethers.