Nathaniel G. Martin

Discovery of a Potent and Selective EGFR Inhibitor (AZD9291) of Both Sensitizing and T790M Resistance Mutations That Spares the Wild Type Form of the Receptor

Epidermal growth factor receptor (EGFR) inhibitors have been used clinically in the treatment of non-small-cell lung cancer (NSCLC) patients harboring sensitizing (or activating) mutations for a number of years. Despite encouraging clinical efficacy with these agents, in many patients resistance develops leading to disease progression. In most cases, this resistance is in the form of the T790M mutation. In addition, EGFR wild type receptor inhibition inherent with these agents can lead to dose limiting toxicities of rash and diarrhea. We describe herein the evolution of an early, mutant selective lead to the clinical candidate AZD9291, an irreversible inhibitor of both EGFR sensitizing (EGFRm+) and T790M resistance mutations with selectivity over the wild type form of the receptor. Following observations of significant tumor inhibition in preclinical models, the clinical candidate was administered clinically to patients with T790M positive EGFR-TKI resistant NSCLC and early efficacy has been observed, accompanied by an encouraging safety profile.

Stereoselective formation of fused tricyclic amines from acyclic aldehydes by a cascade process involving condensation, cyclization, and dipolar cycloaddition.

The preparation of tricyclic amines from acyclic precursors is described using a cascade of tandem reactions involving condensation of an aldehyde with a primary amine, cyclization (with displacement of a halide), and then in situ deprotonation or decarboxylation to give an azomethine ylide or nitrone followed by intramolecular dipolar cycloaddition. The methodology is straightforward, and the aldehyde precursors are prepared easily and quickly in high yield using nitrile alkylations followed by DIBAL-H reduction. The relative ease of reaction of various substrates with different tether lengths between the aldehyde and the halide or dipolarophile has been studied. Several primary amines including simple amino acids such as glycine, alanine, and phenylalanine and derivatives such as glycine ethyl ester and also hydroxylamine have been investigated. High yields are obtained in the formation of different tricyclic ring sizes; the dipolar cycloaddition necessarily creates a five-membered ring, and we have investigated the formation of five- and six-membered rings for the other two new ring sizes. In all cases, yields are high (except when using glycine when the tether to the terminal alkene dipolarophile leads to a six-membered ring), and most efficient is the formation of the tricyclic product in which all five-membered rings are formed. Examples with an alkyne as the dipolarophile were also successful. In all the reactions studied, the products are formed with complete regioselectivity and remarkably with complete stereoselectivity. The key step involves the formation of three new rings and potentially up to four new stereocenters in a single transformation. The power of the chemistry was demonstrated by the synthesis of the core ring systems of the alkaloids (+/-)-scandine and (+/-)-myrioneurinol and the total syntheses of the alkaloids (+/-)-aspidospermine, (+/-)-quebrachamine, and (+/-)-aspidospermidine.

A dearomatizing, thionium ion cyclization for the synthesis of functionalized, azaspirocyclic cyclohexadienones.

Thionium ions, generated by the addition of thiols to N-benzylglyoxamides, undergo a dearomatizing spirocyclization. The alkyl or arylsulfanyl group introduced during the thionium ion cyclization can act as a synthetic handle and a stereochemical control element during modifications of the azaspirocyclic frameworks (R(F) = CH(2)CH(2)C(8)F(17)).

Synthesis of the Core Ring System of the Yuzurimine-Type Daphniphyllum Alkaloids by Cascade Condensation, Cyclization, Cycloaddition Chemistry

Addition of hydroxylamine to substituted 4-chlorobutanals gives intermediate nitrones that undergo tandem cyclization and then intramolecular dipolar cycloaddition to give the core ring system of the yuzurimine-type natural products. Ring-opening of the isoxazolidines gives amino alcohols that can be converted to 1,3-oxazines, representing the tetracyclic core of alkaloids such as daphcalycic acid and daphcalycine.

Identification of pyrazolo-pyrimidinones as GHS-R1a antagonists and inverse agonists for the treatment of obesity

A pyrazolo-pyrimidinone based series of growth hormone secretagogue receptor type 1a (GHS-R1a) antagonists and inverse agonists were identified using a scaffold hop from known quinazolinone GHS-R1a modulators. Lipophilicity was reduced to decrease hERG activity while maintaining GHS-R1a affinity. SAR exploration of a piperidine substituent was used to identify small cyclic groups as a functional switch from partial agonists to neutral antagonists and inverse agonists. A tool compound was identified which had good overall properties and sufficient oral plasma and CNS exposure to demonstrate reduced food intake in mice through a mechanism involving GHS-R1a.

Intramolecular aryl transfer to thionium ions in an approach to α-arylacetamides

An intramolecular aryl transfer to thionium ions has been exploited in a fluorous synthesis of alpha-arylacetamides.

Matched triplicate design sets in the optimisation of glucokinase activators – maximising medicinal chemistry information content

Successful lead optimisation requires the identification of the best compound within the chemical space explored during an optimisation campaign. This can be a costly and inefficient process leading to the synthesis of many sub-optimal compounds. In this paper, a method for carrying out this exercise more effectively is outlined. This relies on the generation of robust datasets on which to build predictive models in a paradigm termed “matched triplicate design sets”. The practical implementation of this approach is exemplified in the optimisation of a new series of glucokinase activators.

Optimising pharmacokinetics of glucokinase activators with matched triplicate design sets – the discovery of AZD3651 and AZD9485

The matched triplicate approach to lead optimisation offers a means of generating more robust quantitative structure activity relationship data and this rigour leads to better quality decision making and greater ability to predict optimal compounds within a series. One of the ultimate aims of this approach is to use the data generated to build more accurate predictive models to identify the best compounds within the exemplified chemical space in an efficient manner. This paper describes the continued application of this approach to the optimisation of a series of glucokinase activators. This second phase focussed primarily on the rational solution to plasma instability observed with the previous compounds and, hence, achieved acceptable oral exposure in the series. The campaign was completed by using the predictive power of Free-Wilson analysis based on the matched triplicate datasets to enable a focussed, matrix based endgame culminating in the identification of two development candidates, AZD3651 and AZD9485.

Synthesis of fused tricyclic amines unsubstituted at the ring-junction positions by a cascade condensation, cyclization, cycloaddition then decarbonylation strategy

Summary Heating aldehydes that contain a protected hydroxymethyl group, a tethered alkyl chloride and a tethered alkenyl group at the α-position of the aldehyde with an amine sets up a cascade (tandem) reaction sequence involving condensation to an intermediate imine, then cyclization and formation of an intermediate azomethine ylide and then intramolecular dipolar cycloaddition. The fused tricyclic products are formed with complete or very high stereochemical control. The hydroxymethyl group was converted into an aldehyde – which could be removed to give the tricyclic amine products that are unsubstituted at the ring junction positions – or was converted into an alkene, which allowed the formation of the core ring system of the alkaloids scandine and meloscine.