Design and Synthesis of Novel Cereblon Binders for Use in Targeted Protein Degradation.

Modulating the chemical composition of cereblon (CRBN) binders is a critical step in the optimization process of protein degraders that seek to hijack the function of this E3 ligase. Small structural changes can have profound impacts on the overall profile of these compounds, including depth of on-target degradation, neosubstrate degradation selectivity, as well as other drug-like properties. Herein, we report the design and synthesis of a series of novel CRBN binding moieties. These CRBN binders were evaluated for CRBN binding and degradation of common neosubstrates Aiolos and GSPT1. A selection of these binders was employed for an exploratory matrix of heterobifunctional molecules, targeting CRBN-mediated degradation of the androgen receptor.

CC-90009: A Cereblon E3 Ligase Modulating Drug That Promotes Selective Degradation of GSPT1 for the Treatment of Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) is marked by significant unmet clinical need due to both poor survival and high relapse rates where long-term disease control for most patients with relapsed or refractory AML remain dismal. Inspired to bring novel therapeutic options to these patients, we envisioned protein degradation as a potential therapeutic approach for the treatment of AML. Following this course, we discovered and pioneered a novel mechanism of action which culminated in the discovery of CC-90009. CC-90009 represents a novel protein degrader and the first cereblon E3 ligase modulating drug to enter clinical development that specifically targets GSPT1 (G1 to S phase transition 1) for proteasomal degradation. This manuscript briefly summarizes the mechanism of action, scientific rationale, medicinal chemistry, pharmacokinetic properties, and efficacy data for CC-90009, which is currently in phase 1 clinical development.

Discovery of CRBN E3 Ligase Modulator CC-92480 for the Treatment of Relapsed and Refractory Multiple Myeloma.

Many patients with multiple myeloma (MM) initially respond to treatment with modern combination regimens including immunomodulatory agents (lenalidomide and pomalidomide) and proteasome inhibitors. However, some patients lack an initial response to therapy (i.e., are refractory), and although the mean survival of MM patients has more than doubled in recent years, most patients will eventually relapse. To address this need, we explored the potential of novel cereblon E3 ligase modulators (CELMoDs) for the treatment of patients with relapsed or refractory multiple myeloma (RRMM). We found that optimization beyond potency of degradation, including degradation efficiency and kinetics, could provide efficacy in a lenalidomide-resistant setting. Guided by both phenotypic and protein degradation data, we describe a series of CELMoDs for the treatment of RRMM, culminating in the discovery of CC-92480, a novel protein degrader and the first CELMoD to enter clinical development that was specifically designed for efficient and rapid protein degradation kinetics.

Evolution of Cereblon-Mediated Protein Degradation as a Therapeutic Modality.

Many cellular processes and pathways are mediated by the regulation of protein-protein complexes. For example, E3 ubiquitin ligases recruit substrate proteins and transfer a ubiquitin tag to target those proteins for destruction by the proteasome. It has now been shown that this cellular process for protein destruction can be redirected by small molecules in both laboratory and clinical settings. This presents a new paradigm in drug discovery, enabling the rapid removal of target proteins linked to disease. In this Innovations review, we will describe the work done on cereblon as a case study on the different strategies available for targeted protein degradation.

Protein Degradation via CRL4CRBN Ubiquitin Ligase: Discovery and Structure-Activity Relationships of Novel Glutarimide Analogs That Promote Degradation of Aiolos and/or GSPT1.

We previously disclosed the identification of cereblon modulator 3 (CC-885), with potent antitumor activity mediated through the degradation of GSPT1. We describe herein the structure-activity relationships for analogs of 3 with exploration of the structurally related dioxoisoindoline class. The observed activity of protein degradation could in part be rationalized through docking into the previously disclosed 3-CRBN-GSPT1 cocrystal ternary complex. For SAR that could not be rationalized through the cocrystal complex, we sought to predict SAR through a QSAR model developed in house. Through these analyses, selective protein degradation could be achieved between the two proteins of interest, GSPT1 and Aiolos.

Highly potent and selective 3-N-methylquinazoline-4(3H)-one based inhibitors of B-Raf(V600E) kinase.

Herein we describe the design of a novel series of ATP competitive B-Raf inhibitors via structure-based methods. These 3-N-methylquinazoline-4(3H)-one based inhibitors exhibit both excellent cellular potency and striking B-Raf selectivity. Optimization led to the identification of compound 16, a potent, selective and orally available agent with excellent pharmacokinetic properties and robust tumor growth inhibition in xenograft studies. Our work also demonstrates that by replacing an aryl amide with an aryl sulfonamide, a multikinase inhibitor such as AZ-628, can be converted to a selective B-Raf inhibitor, a finding that should have broad application in kinase drug discovery.

The discovery of potent and selective pyridopyrimidin-7-one based inhibitors of B-RafV600E kinase.

Herein we describe the discovery of a novel series of ATP competitive B-Raf inhibitors via structure based drug design (SBDD). These pyridopyrimidin-7-one based inhibitors exhibit both excellent cellular potency and striking B-Raf selectivity. Optimization led to the identification of compound 17, a potent, selective and orally available agent with excellent pharmacokinetic properties and robust tumor growth inhibition in xenograft studies.

Potent and selective aminopyrimidine-based B-Raf inhibitors with favorable physicochemical and pharmacokinetic properties.

Recent clinical data provided proof-of-concept for selective B-Raf inhibitors in treatment of B-Raf(V600E) mutant melanoma. Pyrazolopyridine-type B-Raf inhibitors previously described by the authors are potent and selective but exhibit low solubility requiring the use of amorphous dispersion-based formulation for achieving efficacious drug exposures. Through structure-based design, we discovered a new class of highly potent aminopyrimidine-based B-Raf inhibitors with improved solubility and pharmacokinetic profiles. The hinge binding moiety possesses a basic center imparting high solubility at gastric pH, addressing the dissolution limitation observed with our previous series. In our search for an optimal linker-hinge binding moiety system, amide-linked thieno[3,2-d]pyrimidine analogues 32 and 35 (G945), molecules with desirable physicochemical properties, emerged as lead compounds with strong efficacy in a B-Raf(V600E) mutant mouse xenograft model. Synthesis, SAR, lead selection, and evaluation of key compounds in animal studies will be described.

Pyrazolopyridine inhibitors of B-RafV600E. Part 2: structure-activity relationships.

Structure-activity relationships around a novel series of B-Raf(V600E) inhibitors are reported. The enzymatic and cellular potencies of inhibitors derived from two related hinge-binding groups were compared and3-methoxypyrazolopyridine proved to be superior. The 3-alkoxy group of lead B-Raf(V600E) inhibitor 1 was extended and minimally affected potency. The propyl sulfonamide tail of compound 1, which occupies the small lipophilic pocket formed by an outward shift of the αC-helix, was expanded to a series of arylsulfonamides. X-ray crystallography revealed that this lipophilic pocket unexpectedly enlarges to accommodate the bulkier aryl group.

Non-oxime pyrazole based inhibitors of B-Raf kinase.

The synthesis and biological evaluation of non-oxime pyrazole based B-Raf inhibitors is reported. Several oxime replacements have been prepared and have shown excellent enzyme activity. Further optimization of fused pyrazole 2a led to compound 38, a selective and potent B-Raf inhibitor.

Pyrazolopyridine Inhibitors of B-Raf(V600E). Part 1: The Development of Selective, Orally Bioavailable, and Efficacious Inhibitors.

The V600E mutation of B-Raf kinase results in constitutive activation of the MAPK signaling pathway and is present in approximately 7% of all cancers. Using structure-based design, a novel series of pyrazolopyridine inhibitors of B-Raf(V600E) was developed. Optimization led to the identification of 3-methoxy pyrazolopyridines 17 and 19, potent, selective, and orally bioavailable agents that inhibited tumor growth in a mouse xenograft model driven by B-Raf(V600E) with no effect on body weight. On the basis of their in vivo efficacy and preliminary safety profiles, 17 and 19 were selected for further preclinical evaluation.

Potent and selective pyrazole-based inhibitors of B-Raf kinase.

Herein we describe a novel pyrazole-based class of ATP competitive B-Raf inhibitors. These inhibitors exhibit both excellent cellular potency and striking B-Raf selectivity. A subset of these inhibitors has demonstrated the ability to inhibit downstream ERK phosphorylation in LOX tumors from mouse xenograft studies.

Total synthesis of (-)-7-epicylindrospermopsin, a toxic metabolite of the freshwater cyanobacterium aphanizomenonovalisporum, and assignment of its absolute configuration.

[reaction: see text] The Z and E nitrones 38 and 39 from condensation of aldehyde 20 with hydroxylamine 36 underwent intramolecular dipolar cycloaddition to give the substituted 1-aza-7-oxobicyclo[2.2.1] heptanes 40 and 41 in a ratio of 2:1, respectively. Reductive N-O bond cleavage of 40 followed by carbonylation gave cyclic urea 47 in which inversion of the secondary alcohol was effected via an oxidation-reduction sequence. After conversion of the p-bromobenzyl ether 50 to azide 54, activation of the cyclic urea as its O-methylisourea and reduction of the azide led to spontaneous cyclization to afford the tricyclic nucleus 59 of cylindrospermopsin. Global deprotection, including hydrolysis of the 2,4-dimethyoxypyrimidine appendage to a uracil, and then monosulfation of the resultant diol 60 afforded a substance identical with natural (-)-7-epicylindrospermopsin (1). The asymmetric synthesis of (-)-7-epicylindrospermopsin defines its absolute configuration as 7S,8R,10S,12S,13R,14S.

Racemic and chiral lactams as potent, selective and functionally active CCR4 antagonists.

A series of racemic and chiral, nonracemic lactams that display high binding affinities, functional chemotaxis antagonism, and selectivity toward CCR4 are described. Compound 41, which provides reasonably high blood levels in mice when dosed intraperitoneally, was identified as a useful pharmacological tool to explore the role of CCR4 antagonism in animal models of allergic disease.

Asymmetric synthesis of epicylindrospermopsin via intramolecular nitrone cycloaddition. Assignment of absolute configuration.

A synthesis of (-)-epicylindrospermopsin (2) was completed that establishes its absolute configuration and corroborates the corrected structural assignment previously made to this toxin by Weinreb et al. The hydroxylamine 3, prepared from 4-bromobenzyloxyacetaldehyde, was condensed with aldehyde 4, obtained in nine steps from (R)-methionine, to give nitrone 16. Intramolecular cycloaddition of 16 proceeded stereoselectively to yield the oxazabicyclo[2.2.1]heptane 17, which after reduction and deprotection afforded piperidine 18. The latter was transformed via cyclic urea 19 to the inverted C12 alcohol 20, and the derived azide 22 was cyclized to produce the guanidine moiety of 25. Final sulfation of the C12 hydroxyl group furnished (-)-2.