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RBBP4 is a nuclear WD40 motif-containing protein widely implicated in various cancers and a putative drug target. It interacts with multiple proteins within diverse complexes such as nucleosome remodeling and deacetylase (NuRD) complex and polycomb repressive complex 2 (PRC2), as well as histone H3 and H4 through two distinct binding sites. B-cell lymphoma/leukemia 11A (BCL11A), friend of GATA-1 (FOG-1), plant homeodomain finger protein 6 (PHF6) and histone H3 bind to the top of the donut-shaped seven-bladed β-propeller fold of RBBP4, while suppressor of zeste 12 (SUZ12), metastasis associated protein 1 (MTA1) and histone H4 bind to a pocket on the side of the WD40 repeats of this protein. Here, we report the discovery of the first small molecule antagonists of the RBBP4 top pocket, competing with interacting peptides from proteins such as BCL11A and histone H3. We also determined the first crystal structure of RBBP4 in complex with a small molecule (OICR17251), paving the path for structure-guided design and optimization towards more potent antagonists.

There are currently no effective chemotherapeutic drugs approved for the treatment of diffuse intrinsic pontine glioma (DIPG), an aggressive pediatric cancer resident in the pons region of the brainstem. Radiation therapy is beneficial but not curative, with the condition being uniformly fatal. Analysis of the genomic landscape surrounding DIPG has revealed that activin receptor-like kinase-2 (ALK2) constitutes a potential target for therapeutic intervention given its dysregulation in the disease. We adopted an open science approach to develop a series of potent, selective, orally bioavailable, and brain-penetrant ALK2 inhibitors based on the lead compound LDN-214117. Modest structural changes to the C-3, C-4, and C-5 position substituents of the core pyridine ring afforded compounds M4K2009, M4K2117, and M4K2163, each with a superior potency, selectivity, and/or blood-brain barrier (BBB) penetration profile. Robust in vivo pharmacokinetic (PK) properties and tolerability mark these inhibitors as advanced preclinical compounds suitable for further development and evaluation in orthotopic models of DIPG.

We previously reported medicinal chemistry efforts that identified MK-5204, an orally efficacious β-1,3-glucan synthesis inhibitor derived from the natural product enfumafungin. Further extensive optimization of the C2 triazole substituent identified 4-pyridyl as the preferred replacement for the carboxamide of MK-5204, leading to improvements in antifungal activity in the presence of serum, and increased oral exposure. Reoptimizing the aminoether at C3 in the presence of this newly discovered C2 substituent, confirmed that the (R) t-butyl, methyl aminoether of MK-5204 provided the best balance of these two key parameters, culminating in the discovery of ibrexafungerp, which is currently in phase III clinical trials. Ibrexafungerp displayed significantly improved oral efficacy in murine infection models, making it a superior candidate for clinical development as an oral treatment for Candida and Aspergillus infections.

Activating mutations in the epidermal growth factor receptor (EGFR) are common driver mutations in non-small cell lung cancer (NSCLC). First, second and third generation EGFR tyrosine kinase inhibitors (TKIs) are effective at inhibiting mutant EGFR NSCLC, however, acquired resistance is a major issue, leading to disease relapse. Here, we characterize a small molecule, EMI66, an analog of a small molecule which we previously identified to inhibit mutant EGFR signalling via a novel mechanism of action. We show that EMI66 attenuates receptor tyrosine kinase (RTK) expression and signalling and alters the electrophoretic mobility of Coatomer Protein Complex Beta 2 (COPB2) protein in mutant EGFR NSCLC cells. Moreover, we demonstrate that EMI66 can alter the subcellular localization of EGFR and COPB2 within the early secretory pathway. Furthermore, we find that COPB2 knockdown reduces the growth of mutant EGFR lung cancer cells, alters the post-translational processing of RTKs, and alters the endoplasmic reticulum (ER) stress response pathway. Lastly, we show that EMI66 treatment also alters the ER stress response pathway and inhibits the growth of mutant EGFR lung cancer cells and organoids. Our results demonstrate that targeting of COPB2 with EMI66 presents a viable approach to attenuate mutant EGFR signalling and growth in NSCLC.

The clinical success of the echinocandins, which can only be administered parentally, has validated β-1,3-glucan synthase (GS) as an antifungal target. Semi-synthetic modification of enfumafungin, a triterpene glycoside natural product, was performed with the aim of producing a new class of orally active GS inhibitors. Replacement of the C2 acetoxy moiety with various heterocycles did not improve GS or antifungal potency. However, replacement of the C3 glycoside with an aminoether moiety dramatically improved oral pharmacokinetic (PK) properties while maintaining GS and antifungal potency. Installing an aminotetrazole at C2 in conjunction with an N-alkylated aminoether at C3 produced derivatives with significantly improved GS and antifungal potency that exhibited robust oral efficacy in a murine model of disseminated candidiasis.

The transcription factor B cell lymphoma 6 (BCL6) is required for the generation of an effective humoral immune response through the development and maintenance of germinal centers (GCs). The inhibition of the protein−protein interaction between BCL6 and its corepressors has been implicated as a therapeutic target for diffuse large B-cell lymphoma (DLBCL), a type of non-Hodgkin’s lymphoma (NHL). Using structure-based drug design, we initiated a program to identify novel BCL6 inhibitors. We identified a high micromolar virtual screening hit which was then optimized for potent biophysical binding and anti-proliferative cellular activity resulting in the identification of OICR-10268, a potent and selective Bcl6 inhibitor. Citation Format: Iain D. Watson, Methvin Isaac, Brian Wilson, Anh Chau, Justin Morin, Pandiaraju Subramanian, Ahmed Mamai, Babu Joseph, Michael Prakesch, David Uehling, Ayome Abibi, Richard Marcellus, Craig Strathdee, Ratheesh Subramaniam, Brigitte Theriault, Jeffrey Winston, Manuel Chan, Carly Griffin, Herman Cheung, Taira Kiyota, Elijus Undzys, Ahmed Aman, Gennady Poda, Doug Kuntz, Neil C. Pomroy, Gil G. Privé, Rima Al-awar. Discovery of OICR-10268: A potent and selective BCL6 inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 7.

Orally bioavailable inhibitors of β-(1,3)- d -glucan synthase have been pursued as new, broad-spectrum fungicidal therapies suitable for treatment in immunocompromised patients. Toward this end, a collaborative medicinal chemistry program was established based on semisynthetic derivatization of the triterpenoid glycoside natural product enfumafungin in order to optimize in vivo antifungal activity and oral absorption properties. In the course of these studies, it was hypothesized that the pharmacokinetic properties of the semisynthetic enfumafungin analog 3 could be improved by tethering the alkyl groups proximal to the basic nitrogen of the C3-aminoether side chain into an azacyclic system, so as to preclude oxidative N-demethylation. The results of this research effort are disclosed herein.

SummaryTo identify therapeutic opportunities for oncolytic viral therapy, we conducted genome-wide RNAi screens to search for host factors that modulate rhabdoviral oncolysis. Our screens uncovered the endoplasmic reticulum (ER) stress response pathways as important modulators of rhabdovirus-mediated cytotoxicity. Further investigation revealed an unconventional mechanism whereby ER stress response inhibition preconditioned cancer cells, which sensitized them to caspase-2-dependent apoptosis induced by a subsequent rhabdovirus infection. Importantly, this mechanism was tumor cell specific, selectively increasing potency of the oncolytic virus by up to 10,000-fold. In vivo studies using a small molecule inhibitor of IRE1α showed dramatically improved oncolytic efficacy in resistant tumor models. Our study demonstrates proof of concept for using functional genomics to improve biotherapeutic agents for cancer.

The synthesis of two conformationally constrained lysine analogues is reported. The synthesis of the novel analogue 1 based on the 3-aza-bicyclo[3.1.0]hexane system is accomplished from the known tricycle 3 in eight steps. The synthesis of the analogue 2 is accomplished in eight steps from 4-hydroxy proline. Both analogues are synthesized appropriately protected for Fmoc/Boc solid-phase peptide synthesis.

Metal salen complexes containing intramolecular bases have been designed for use as bifunctional catalysts. A ligand containing a quinoline base and the salen core has been synthesized for this purpose. Ruthenium, chromium, titanium, and zinc complexes of the salen have been formed and characterized. A crystal structure of a μ-oxo−titanium dimer incorporating the bifunctional ligand shows a typical salen coordination pattern and illustrates that the nitrogens of the quinoline groups participate in neither intra- nor intermolecular coordination. In addition, the quinoline groups orient in an appropriate manner to act as bases toward substrates coordinated at the apical positions of these complexes. As an indication that the quinoline bases can alter the activity of salen metal complexes, the addition of dialkylzincs to aldehydes was shown to be accelerated by the quinoline salen ligand relative to a salen lacking the quinoline groups.

The reaction of N-enoyloxazolidinones with diphenylsulfonium isoproylide in the presence of Lewis acids is explored. The diastereoselectivity of the reaction of N-enoyloxazolidinones 1a and 1b with diphenylsulfonium isopropylide could be mediated by the addition of some Lewis acids. The reaction of N-enoyloxazolidinone 4 with diphenylsulfonium isoproylide was also explored with chiral Lewis acids. When this reaction was run with bis(oxazoline) ligand 6 and a number of Lewis acids, product was obtained in as high as 95% ee. A loss of stereoselectivity was observed with less than stoichiometric amounts of Lewis acid.

A novel series of melatonin analogues based on the benzodioxin nucleus is described. The compounds were prepared in several steps from 2-carbethoxy-1,4-benzodioxin. Some of these derivatives competitively inhibited 2-[125I]-iodomelatonin binding to chicken brain and ovine pars tuberalis membranes, albeit with very reduced affinity compared with melatonin.

The cyclopropanation of unsaturated lactams 1 and 3 derived from pyroglutamic acid with nucleophilic alkylidene transfer reagents is investigated. Good-to-modest yields of cyclopropanes were obtained with most sulfur ylides explored. Syn/anti selectivity was found to be dependent on the synthon as well as the sulfur ylide. This cyclopropanation methodology is used in the synthesis of arginine and glutamic acid analogues.

The reaction of N-enoyloxazolidinones with diphenylsulfonium isoproylide in the presence of Lewis acids is explored. The diastereoselectivity of the reaction of N-enoyloxazolidinones 1a and 1b with diphenylsulfonium isopropylide could be mediated by the addition of some Lewis acids. The reaction of N-enoyloxazolidinone 4 with diphenylsulfonium isoproylide was also explored with chiral Lewis acids. When this reaction was run with bis(oxazoline) ligand 6 and a number of Lewis acids, product was obtained in as high as 95% ee. A loss of stereoselectivity was observed with less than stoichiometric amounts of Lewis acid.

A strategy for the solid-phase diversification of PPII mimic scaffolds through guanidinylation is presented. The approach involves the synthesis N-Pmc-N'-alkyl thioureas as diversification reagents. Analogues of Fmoc-Orn(Mtt)-OH can be incorporated into a growing peptide chain on Wang resin. Side chain deprotection with 1% TFA/CH2Cl2 followed by EDCI-mediated reaction of N-Pmc-N'-alkyl thioureas with the side chain amine affords arginine analogues with modified guanidine head groups. The scope, limitations, and incidental chemistry are discussed.

Based on the X-ray crystal structure of cAMP-dependent protein kinase (PKA) with the endogenous inhibitor PKI and the X-ray crystal structure of cyclin-dependent kinase 2 (CDK2) with a substrate peptide, a proposal is put forth that some protein kinases bind peptide substrates in their active sites in the poly-L-proline type II (PPII) conformation. In this work, PPII peptide mimics are evaluated as pseudosubstrate inhibitors of cGMP-dependent protein kinase (PKG) to explore if PKG also binds peptide substrates in the PPII conformation. Inhibition data of our PPII mimetics provide evidence that the P-1, P-2, and P-3 residues of substrate peptides bind in the PPII conformation (phi approximately -75 degrees, psi approximately 145 degrees). In addition, the inhibition data also suggest that the P-1, P-2, and P-3 residues in substrate peptides bind with a gauche(-) chi1 angle.

This paper describes conformational studies of proline-templated amino acids (PTAAs) based on the 3-azabicyclo[3.1.0]hexane system as well as conformational studies on short peptides composed of these PTAAs. NOE data, coupling constants, and molecular modeling are consistent with a flattened boat conformation for monomeric and oligomeric residues based on this bicyclic system. NMR studies on dimeric and trimeric oligomers are consistent with a populated poly-L-proline type II conformation in CDCl3 and D2O. Solution studies and molecular modeling predicts phi approximately -70 degrees, psi approximately 131 degrees, chi 1 approximately -57 degrees, and chi 2 approximately -158 degrees for oligomeric residues.

[reaction: see text] Solid-phase guanidinylation of proline-templated amino acids is studied as a diversification strategy of poly-L-proline type II scaffolds.

A new series of substituted oxygenated heterocycles and thio-analogues were synthesized and evaluated as melatonin receptor ligands. The replacement of the indolic moiety of melatonin by heterocyclic skeleton such as 1,4-benzodioxin, 2,3-dihydro-1,4-benzodioxin, chroman, 2,3-dihydro-1,4-benzoxathiin, thiochroman, carrying the amidic chain on the aromatic ring, leads to compounds showing a weak affinity for melatonin receptors, except for the compounds 1cb and 1hb.