Discovery of N-(1-Acryloylazetidin-3-yl)-2-(1H-indol-1-yl)acetamides as Covalent Inhibitors of KRASG12C.

KRAS regulates many cellular processes including proliferation, survival, and differentiation. Point mutants of KRAS have long been known to be molecular drivers of cancer. KRAS p.G12C, which occurs in approximately 14% of lung adenocarcinomas, 3-5% of colorectal cancers, and low levels in other solid tumors, represents an attractive therapeutic target for covalent inhibitors. Herein, we disclose the discovery of a class of novel, potent, and selective covalent inhibitors of KRASG12C identified through a custom library synthesis and screening platform called Chemotype Evolution and structure-based design. Identification of a hidden surface groove bordered by H95/Y96/Q99 side chains was key to the optimization of this class of molecules. Best-in-series exemplars exhibit a rapid covalent reaction with cysteine 12 of GDP-KRASG12C with submicromolar inhibition of downstream signaling in a KRASG12C-specific manner.

A panel of cytochrome P450 BM3 variants to produce drug metabolites and diversify lead compounds.

Herein we demonstrate that a small panel of variants of cytochrome P450 BM3 from Bacillus megaterium covers the breadth of reactivity of human P450s by producing 12 of 13 mammalian metabolites for two marketed drugs, verapamil and astemizole, and one research compound. The most active enzymes support preparation of individual metabolites for preclinical bioactivity and toxicology evaluations. Underscoring their potential utility in drug lead diversification, engineered P450 BM3 variants also produce novel metabolites by catalyzing reactions at carbon centers beyond those targeted by animal and human P450s. Production of a specific metabolite can be improved by directed evolution of the enzyme catalyst. Some variants are more active on the more hydrophobic parent drug than on its metabolites, which limits production of multiply-hydroxylated species, a preference that appears to depend on the evolutionary history of the P450 variant.

A diverse family of thermostable cytochrome P450s created by recombination of stabilizing fragments.

Thermostable enzymes combine catalytic specificity with the toughness required to withstand industrial reaction conditions. Stabilized enzymes also provide robust starting points for evolutionary improvement of other protein properties. We recently created a library of at least 2,300 new active chimeras of the biotechnologically important cytochrome P450 enzymes. Here we show that a chimera's thermostability can be predicted from the additive contributions of its sequence fragments. Based on these predictions, we constructed a family of 44 novel thermostable P450s with half-lives of inactivation at 57 degrees C up to 108 times that of the most stable parent. Although they differ by as many as 99 amino acids from any known P450, the stable sequences are catalytically active. Among the novel functions they exhibit is the ability to produce drug metabolites. This chimeric P450 family provides a unique ensemble for biotechnological applications and for studying sequence-stability-function relationships.

Total synthesis of ustiloxin D and considerations on the origin of selectivity of the asymmetric allylic alkylation.

As part of investigations into cell cycle checkpoint inhibitors, an asymmetric synthesis of the antimitotic natural product, ustiloxin D, has been completed. A salen-Al-catalyzed aldol reaction was employed to construct a chiral oxazoline 9 (99% yield, 98% ee) that served the dual purpose of installing the necessary 1,2-amino alcohol functionality as well as providing an efficient synthon for the requisite methylamino group at C9. The chiral aryl-alkyl ether was assembled using a Pd-catalyzed asymmetric allylic alkylation that notably delivered a product with stereochemistry opposite to that predicted by precedent. The linear tetrapeptide was subsequently cyclized to produce ustiloxin D. The mechanistic origin of the allylic alkylation selectivity was further investigated, and a working hypothesis for the origin of the observed stereoselectivity has been proposed.

Enantioselective total synthesis of ustiloxin D.

Ustiloxin D and phomopsin A are potent antimitotic agents that bind to tubulin and interfere with cellular microtubule function. A synthetic strategy has been developed to allow access to both of the natural products as well as a variety of variants of the ustiloxin and phomopsin family members in order to provide sufficient quantities for biological studies. Herein we report the enantioselective total synthesis of ustiloxin D using a longest linear sequence of 20 steps. Four of the five stereocenters were set using catalytic asymmetric methodologies. In particular, Evans's new Al-catalyzed asymmetric aldol reaction facilitated access to both syn and anti products corresponding to the different benzylic stereochemistries found in ustiloxins and phomopsins. In addition, due to its high functional group tolerance, Trost's Pd-mediated etherification was used to construct the chiral tertiary alkyl-aryl ether. Taken together, these synthetic strategies allow us to use densely functionalized intermediates to realize an efficient synthesis of ustiloxin D.