The creation and characterisation of a National Compound Collection: the Royal Society of Chemistry pilot.

We present a summary of the National Compound Collection (NCC) pilot; which harvested chemical structure data from 746 publicly-available PhD theses to create an enhanced database of diverse and interesting (largely organic) molecular entities. The database comprised ∼75 000 structure entries, of which 70% were new to ChemSpider at the time of upload. The dataset was evaluated for structural uniqueness by twelve external drug discovery groups from the pharmaceutical, biotech, academic and not-for-profit sectors. These partners generated data reported here comparing the NCC pilot with their in-house compound collections. The proportion of NCC structures considered to be useful for drug discovery ranged from 5-80% depending on the strictness of the filters used; most interestingly from a drug discovery standpoint ∼13k NCC compounds (18% of the NCC) passed the filters and were of good diversity. These compounds are quite different from those that are already present in the screening collections but not so different that they are no longer considered to be drug-like. In general, the drug discovery teams would consider these compounds to be high value molecules for inclusion in their screening collections. This pilot addressed the potential value of unpublished data and explored the practicalities of large-scale data extraction, to inform both retrospective and prospective extraction of chemical data from theses.

Discovery of a highly potent series of TLR7 agonists.

The discovery of a series of highly potent and novel TLR7 agonist interferon inducers is described. Structure-activity relationships are presented, along with pharmacokinetic studies of a lead molecule from this series of N9-pyridylmethyl-8-oxo-3-deazapurine analogues. A rationale for the very high potency observed is offered. An investigation of the clearance mechanism of this class of compounds in rat was carried out, resulting in aldehyde oxidase mediated oxidation being identified as a key component of the high clearance observed. A possible solution to this problem is discussed.

Acidic triazoles as soluble guanylate cyclase stimulators.

A series of acidic triazoles with activity as soluble guanylate cyclase stimulators is described. Incorporation of the CF(3) triazole improved the overall physicochemical and drug-like properties of the molecule and is exemplified by compound 25.

Synthesis and evaluation of heteroarylalanine diacids as potent and selective neutral endopeptidase inhibitors.

Heteroarylalanine derivatives 4 were designed as potential inhibitors of neutral endopeptidase (NEP EC 3.4.24.11). Selectivity over other zinc metalloproteinases was explored through occupation of the S2' subsite within NEP. Structural optimisation led to the identification of 5-phenyl oxazole 4f, a potent and selective NEP inhibitor. A crystal structure of the inhibitor bound complex is reported.

Design and optimisation of orally active TLR7 agonists for the treatment of hepatitis C virus infection.

The synthesis and structure-activity relationships of a series of novel interferon inducers are described. Pharmacokinetic studies and efficacy assessment of a series of 8-oxo-3-deazapurine analogues led to the identification of compound 33, a potent and selective agonist of the TLR7 receptor with an excellent in vivo efficacy profile in a mouse model.

1-(2-Ethoxyethyl)-1H-pyrazolo[4,3-d]pyrimidines as potent phosphodiesterase 5 (PDE5) inhibitors.

1H-Pyrazolo[4,3-d]pyrimidines are a class of potent and selective second generation phosphodiesterase 5 (PDE5) inhibitors. This work explores the potency, selectivity and efficacy of 1-(2-ethoxyethyl)-1H-pyrazolo[4,5-d]pyrimidines as PDE5 inhibitors resulting in the advancement of a clinical candidate.

1-(2-(2,2,2-trifluoroethoxy)ethyl-1H-pyrazolo[4,3-d]pyrimidines as potent phosphodiesterase 5 (PDE5) inhibitors.

1H-Pyrazolo[4,3-d]pyrimidines were previously disclosed as a potent second generation class of phosphodiesterase 5 (PDE5) inhibitors. This work explores the advancement of more selective and potent PDE5 inhibitors resulting from the substitution of 2-(2,2,2-trifluoroethoxy)ethyl at the 1 position in the so-called alkoxy pocket.

Identification, synthesis and SAR of amino substituted pyrido[3,2b]pyrazinones as potent and selective PDE5 inhibitors.

A new class of potent and selective PDE5 inhibitors is disclosed. Guided by X-ray crystallographic data, optimization of an HTS lead led to the discovery of a series of 2-aryl, (N8)-alkyl substituted-6-aminosubstituted pyrido[3,2b]pyrazinones which show potent inhibition of the PDE5 enzyme. Synthetic details and some structure-activity relationships are also presented.

Design of second generation phosphodiesterase 5 inhibitors.

The clinical significance of phosphodiesterase 5 (PDE5) inhibition is increasingly understood following the pioneering work with sildenafil, and the continuing development programmes for both sildenafil and other marketed inhibitors. Since the initial launch of sildenafil for male erectile dysfunction (MED), approval has now been granted for treatment of pulmonary hypertension, whilst ongoing studies have indicated the potential of PDE5 inhibition for the treatment of a range of additional indications including cardioprotection, memory retention and diabetes. Many of these additional indications are best suited to chronic oral dosing and emphasise the need for highly selective inhibitors with extended duration of action. This article will focus on a research programme aimed at the discovery of improved second-generation PDE5 inhibitors. Essential features of these new PDE5 inhibitors would be enhanced selectivity across the whole PDE family and pharmacokinetics compatible with once daily dosing. Key elements used in this programme are high throughput screening (HTS), exploitation of co-crystal structural information for bound inhibitor in the PDE5 active site, and employment of parallel chemistry to speed progress. Under the guidance of co-crystal structural information, a non-selective HTS hit with poor physicochemistry was initially modified using parallel chemistry to give a lead compound (3) that established a new PDE5 inhibitor series. Notably, (3) displayed physicochemistry compatible with a long plasma half-life, and wide chemical scope. Subsequent optimisation of (3) using crystal structure information to guide design, led rapidly to highly potent and selective PDE5 inhibitors (47, 50). Continued focus on physical properties through ligand efficiency evaluation and lipophilicity (cLogP), maintained the inherently desirable physicochemistry of the initial lead.