Frederick W. Goldberg

Designing novel building blocks is an overlooked strategy to improve compound quality

One pragmatic way to improve compound quality, while enhancing and accelerating drug discovery projects, is the ability to access a high quality, novel, diverse building block collection. Here, we outline general principles that should be applied to ensure that a building block collection has the greatest impact on drug discovery projects, by discussing design principles for novel reagents and what types of reagents are popular with medicinal chemists in general. We initiated a program in 2009 to address this, which has already delivered three candidate drugs, and the success of that program provides evidence that focussing on building block design is a useful strategy for drug discovery.

Medicinal chemistry of inhibitors of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1).

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) is the enzyme primarily responsible for the regulation of intracellular cortisol levels. Inhibition of 11β-HSD1 is an attractive mechanism for the treatment of obesity and other elements of the metabolic syndrome. Emerging literature also supports a potential role in the treatment of other unmet medical needs including Alzheimers disease, vascular inflammation, cardiovascular disease, and glaucoma. The aim of this article is to review the medicinal chemistry literature around small molecule approaches to developing synthetic inhibitors of 11β-HSD1 and to highlight key compounds that have resulted from the efforts of both industrial and academic groups. The reported data from 11β-HSD1 inhibitors that have progressed into the clinic are summarized followed by a perspective from the authors.

Asymmetric synthesis of 2-alkyl-substituted tetrahydroquinolines by an enantioselective aza-Michael reaction

An optically active tetrahydroquinoline intermediate (5) was prepared in 8 steps from monoprotected ethylene glycol, using a Pd-catalysed aza-Michael reaction to induce chirality. This can be transformed into three Galipea alkaloids (angustureine, galipeine and cuspareine). The proximity of a benzyloxy group is found to exert profound effects in several steps of the synthesis.

Free-Wilson and Structural Approaches to Co-optimizing Human and Rodent Isoform Potency for 11β-Hydroxysteroid Dehydrogenase Type 1 (11β-HSD1) Inhibitors

11β-Hydroxysteroid dehydrogenase 1 (11β-HSD1) has been a target of intensive research efforts across the pharmaceutical industry, due to its potential for the treatment of type II diabetes and other elements of the metabolic syndrome. To demonstrate the value of 11β-HSD1 in preclinical models, we required inhibitors with good potency against both human and rodent isoforms. Herein, we describe our efforts to understand how to co-optimize human and murine potency within the (5-hydroxy-2-adamantyl)-pyrimidine-5-carboxamide series. Two approaches are described-a data-driven (Free-Wilson) analysis and a structure-based design approach. The conclusions from these approaches were used to inform an efficient campaign to design compounds with consistently good human/murine potency within a logD(7.4) range of 1-3. Compounds 20 and 26 demonstrated good rodent PK, which allowed us to demonstrate a PK/PD relationship in rat and mouse. We then evaluated 26 against glycemic and body weight end points in murine disease models, where it demonstrated glucose and body weight efficacy at 300 mg/kg/day but only body weight efficacy at 50 mg/kg/day, despite providing >90% target engagement in the liver.

Rapid Generation of a High Quality Lead for Transforming Growth Factor-Beta (Tgf-Beta) Type I Receptor (Alk5).

A novel class of 4-pyridinoxy-2-anilinopyridine-based TGF-beta type I receptor (also known as activin-like kinase 5 or ALK5) inhibitors is reported. The binding mode of this scaffold was successfully predicted by analyzing possible docked binding modes of literature inhibitors and novel synthetic ideas. Compounds such as 19 are potent ALK5 inhibitors with good physicochemical and pharmacokinetic properties and thus represent high quality leads for further optimization.

The changing landscape of cancer drug discovery: a challenge to the medicinal chemist of tomorrow

Since the development of the first cytotoxic agents, synthetic organic chemistry has advanced enormously. The synthetic and medicinal chemists of today are at the centre of drug development and are involved in most, if not all, processes of drug discovery. Recent decreases in government funding and reformed educational policies could, however, seriously impact on drug discovery initiatives worldwide. Not only could these changes result in fewer scientific breakthroughs, but they could also negatively affect the training of our next generation of medicinal chemists.

Optimization of Brain Penetrant 11β-Hydroxysteroid Dehydrogenase Type I Inhibitors and in Vivo Testing in Diet-Induced Obese Mice

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) has been widely considered by the pharmaceutical industry as a target to treat metabolic syndrome in type II diabetics. We hypothesized that central nervous system (CNS) penetration might be required to see efficacy. Starting from a previously reported pyrimidine compound, we removed hydrogen-bond donors to yield 3, which had modest CNS penetration. More significant progress was achieved by changing the core to give 40, which combines good potency and CNS penetration. Compound 40 was dosed to diet-induced obese (DIO) mice and gave excellent target engagement in the liver and high free exposures of drug, both peripherally and in the CNS. However, no body weight reduction or effects on glucose or insulin were observed in this model. Similar data were obtained with a structurally diverse thiazole compound 51. This work casts doubt on the hypothesis that localized tissue modulation of 11β-HSD1 activity alleviates metabolic syndrome.

Identification and optimisation of 7-azaindole PAK1 inhibitors with improved potency and kinase selectivity

A novel series of PAK1 inhibitors was discovered from a kinase directed screen. SAR exploration in the selectivity pocket and solvent tail regions was conducted to understand and optimise PAK1 potency and selectivity against targeted kinases. A liganded PAK1 crystal structure was utilised to guide compound design. Permeability and kinase selectivity impacted the translation of enzyme to cellular PAK1 potency. Compound 36 (AZ-PAK-36) demonstrated improved Gini coefficient, good PAK1 cellular potency and has utility as a tool compound for target validation studies.

Discovery and optimization of efficacious neutral 4-amino-6-biphenyl-7,8-dihydropyrimido[5,4-f][1,4]oxazepin-5-one diacylglycerol acyl transferase-1 (DGAT1) inhibitors

A series of neutral DGAT1 inhibitors with good potency and pharmacokinetics (PK) has been designed by modification of an acidic startpoint. This was achieved by selecting the acid with the highest ligand lipophilicity efficiency (LLE) and replacing the acid with neutral isosteres. PK properties (Fabs) were then improved by removing the sidechain to reduce molecular weight and polar surface area (PSA). Compound 13 has shown good cross-species PK, with pre-clinical efficacy and PK/PD relationships comparable to those previously described for acidic inhibitors.

Design of pyrazolo-pyrimidines as 11β-HSD1 inhibitors through optimisation of molecular electrostatic potential

The inhibition of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) is a potentially attractive mechanism for the treatment of obesity and other elements of the metabolic syndrome. A series of pyrazolo-pyrimidine inhibitors of this enzyme were identified from directed library synthesis. Knowledge of how these compounds bind to the enzyme and the key hydrogen-bonding interactions was used to design further compounds. The hydrogen-bond acceptor strength was calculated from the molecular electrostatic potential using quantum mechanical theory. Compounds were designed to modulate the acceptor strength, thus optimising the potency and other drug-like properties. Compounds with enhanced CNS penetration were designed through further modification of the electrostatic potential and the hydrogen-bond properties.