Identification of Novel Potent NSD2-PWWP1 Ligands Using Structure-Based Design and Computational Approaches.

Dysregulation of histone methyl transferase nuclear receptor-binding SET domain 2 (NSD2) has been implicated in several hematological and solid malignancies. NSD2 is a large multidomain protein that carries histone writing and histone reading functions. To date, identifying inhibitors of the enzymatic activity of NSD2 has proven challenging in terms of potency and SET domain selectivity. Inhibition of the NSD2-PWWP1 domain using small molecules has been considered as an alternative approach to reduce NSD2-unregulated activity. In this article, we present novel computational chemistry approaches, encompassing free energy perturbation coupled to machine learning (FEP/ML) models as well as virtual screening (VS) activities, to identify high-affinity NSD2 PWWP1 binders. Through these activities, we have identified the most potent NSD2-PWWP1 binder reported so far in the literature: compound 34 (pIC50 = 8.2). The compounds identified herein represent useful tools for studying the role of PWWP1 domains for inhibition of human NSD2.

Discovery and characterisation of quinazolines and 8-Azaquinazolines as NLRP3 agonists with oral bioavailability in mice.

The NLRP3 inflammasome is a multiprotein complex that plays a critical role in activating the immune system in response to danger signals. Small molecule agonists of NLRP3 may offer clinical benefits in cancer immunology either as a monotherapy or in combination with checkpoint blockade, where it is hypothesised that their application can help to initiate an antitumor immune response. In this study, we report the discovery of quinazolines and 8-azaquinazolines as NLRP3 agonists and their chemical optimization to afford compounds with oral bioavailability in mice. We confirm that these compounds engage the NLRP3 inflammasome by verifying their dependence upon lipopolysaccharide (LPS) priming for cytokine release and the activation of Caspase-1. We further demonstrate pathway engagement through loss of activity in an NLRP3-knockout THP1 cell line. Based on their pharmacokinetic profile and biological activity, these compounds represent valuable tools to evaluate the therapeutic potential of NLRP3 activation in a pre-clinical setting.

Discovery of a Potent and Orally Bioavailable Zwitterionic Series of Selective Estrogen Receptor Degrader-Antagonists.

Herein, we report the optimization of a meta-substituted series of selective estrogen receptor degrader (SERD) antagonists for the treatment of ER+ breast cancer. Structure-based design together with the use of modeling and NMR to favor the bioactive conformation led to a highly potent series of basic SERDs with promising physicochemical properties. Issues with hERG activity resulted in a strategy of zwitterion formation and ultimately in the identification of 38. This compound was shown to be a highly potent SERD capable of effectively degrading ERα in both MCF-7 and CAMA-1 cell lines. The low lipophilicity and zwitterionic nature led to a SERD with a clean secondary pharmacology profile and no hERG activity. Favorable physicochemical properties resulted in good oral bioavailability in preclinical species and potent in vivo activity in a mouse xenograft model.

Trends in Molecular Properties, Bioavailability, and Permeability across the Bayer Compound Collection.

For oral drugs, medicinal chemists aim to design compounds with high oral bioavailability, of which permeability is a key determinant. Taking advantage of >2000 compounds tested in rat bioavailability studies and >20,000 compounds tested in Caco2 assays at Bayer, we have examined the molecular properties governing bioavailability and permeability. In addition to classical parameters such as logD and molecular weight, we also investigated the relationship between calculated pKa and permeability. We find that neutral compounds retain permeability up to a molecular weight limit of 700, while stronger acids and bases are restricted to weights of 400-500. We also investigate trends for common properties such as hydrogen bond donors and acceptors, polar surface area, aromatic ring count, and rotatable bonds, including compounds which exceed Lipinski's rule of five (Ro5). These property-structure relationships are combined to provide design guidelines for bioavailable drugs in both traditional and "beyond rule of 5" (bRo5) chemical space.

Addressing the Reciprocal Crosstalk between the AR and the PI3K/AKT/mTOR Signaling Pathways for Prostate Cancer Treatment.

The reduction in androgen synthesis and the blockade of the androgen receptor (AR) function by chemical castration and AR signaling inhibitors represent the main treatment lines for the initial stages of prostate cancer. Unfortunately, resistance mechanisms ultimately develop due to alterations in the AR pathway, such as gene amplification or mutations, and also the emergence of alternative pathways that render the tumor less or, more rarely, completely independent of androgen activation. An essential oncogenic axis activated in prostate cancer is the phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, as evidenced by the frequent alterations of the negative regulator phosphatase and tensin homolog (PTEN) and by the activating mutations in PI3K subunits. Additionally, crosstalk and reciprocal feedback loops between androgen signaling and the PI3K/AKT/mTOR signaling cascade that activate pro-survival signals and play an essential role in disease recurrence and progression have been evidenced. Inhibitors addressing different players of the PI3K/AKT/mTOR pathway have been evaluated in the clinic. Only a limited benefit has been reported in prostate cancer up to now due to the associated side effects, so novel combination approaches and biomarkers predictive of patient response are urgently needed. Here, we reviewed recent data on the crosstalk between AR signaling and the PI3K/AKT/mTOR pathway, the selective inhibitors identified, and the most advanced clinical studies, with a focus on combination treatments. A deeper understanding of the complex molecular mechanisms involved in disease progression and treatment resistance is essential to further guide therapeutic approaches with improved outcomes.

Drug discovery for epigenetics targets.

Dysregulation of the epigenome is associated with the onset and progression of several diseases, including cancer, autoimmune, cardiovascular, and neurological disorders. Members from the three families of epigenetic proteins (readers, writers, and erasers) have been shown to be druggable using small-molecule inhibitors. Increasing knowledge of the role of epigenetics in disease and the reversibility of these modifications explain why pharmacological intervention is an attractive strategy for tackling epigenetic-based disease. In this review, we provide an overview of epigenetics drug targets, focus on approaches used for initial hit identification, and describe the subsequent role of structure-guided chemistry optimisation of initial hits to clinical candidates. We also highlight current challenges and future potential for epigenetics-based therapies.

Diverse, Potent, and Efficacious Inhibitors That Target the EED Subunit of the Polycomb Repressive Complex 2 Methyltransferase.

Aberrant activity of the histone methyltransferase polycomb repressive complex 2 (PRC2) has been linked to several cancers, with small-molecule inhibitors of the catalytic subunit of the PRC2 enhancer of zeste homologue 2 (EZH2) being recently approved for the treatment of epithelioid sarcoma (ES) and follicular lymphoma (FL). Compounds binding to the EED subunit of PRC2 have recently emerged as allosteric inhibitors of PRC2 methyltransferase activity. In contrast to orthosteric inhibitors that target EZH2, small molecules that bind to EED retain their efficacy in EZH2 inhibitor-resistant cell lines. In this paper we disclose the discovery of potent and orally bioavailable EED ligands with good solubilities. The solubility of the EED ligands was optimized through a variety of design tactics, with the resulting compounds exhibiting in vivo efficacy in EZH2-driven tumors.

Free energy perturbation in the design of EED ligands as inhibitors of polycomb repressive complex 2 (PRC2) methyltransferase.

Free Energy Perturbation (FEP) calculations can provide high-confidence predictions of the interaction strength between a ligand and its protein target. We sought to explore a series of triazolopyrimidines which bind to the EED subunit of the PRC2 complex as potential anticancer therapeutics, using FEP calculations to inform compound design. Combining FEP predictions with a late-stage functionalisation (LSF) inspired synthetic approach allowed us to rapidly evaluate structural modifications in a previously unexplored region of the EED binding site. This approach generated a series of novel triazolopyrimidine EED ligands with improved physicochemical properties and which inhibit PRC2 methyltransferase activity in a cancer-relevant G401 cell line.

Peptides as a platform for targeted therapeutics for cancer: peptide-drug conjugates (PDCs).

Peptides can offer the versatility needed for a successful oncology drug discovery approach. Peptide-drug conjugates (PDCs) are an emerging targeted therapeutic that present increased tumour penetration and selectivity. Despite these advantages, there are still limitations for the use of peptides as therapeutics exemplified through their slow progression to get into the clinic and limited oral bioavailability. New approaches to address these problems have been studied and successfully implemented to enhance the stability of peptides and their constructs. There is great promise for the future of PDCs with two molecules already on the market and many variations currently undergoing clinical trials, such as bicycle-toxin conjugates and peptide-dendrimer conjugates. This review summarises the entire process needed for the design and successful development of an oncology PDC including chemical and nanomaterial strategies to enhance peptide stability within circulation, the function of each component of a PDC construct, and current examples in clinical trials.

Targeting PRC2 for the treatment of cancer: an updated patent review (2016 - 2020).

INTRODUCTION: PRC2 is a histone methyltransferase complex associated with several cancer types. Tazemetostat was recently approved as the first inhibitor targeting the catalytic subunit EZH2 and several other EZH2 inhibitors are now under clinical evaluation. Beyond EZH2, researchers have also explored other approaches including PRC2 activators, dual agents inhibiting both EZH1 and EZH2, allosteric inhibitors binding to EED, and compounds which induce the degradation of PRC2 constituent proteins. AREAS COVERED: This review provides an overview of anticancer therapies targeting PRC2 during the period 2016-2020 including clinical trials, patents and the scientific literature. EXPERT OPINION: The approval of tazemetostat marks the clinical validation of EZH2 for the treatment of cancer. Despite this success many questions remain; for instance, tazemetostat was briefly placed on clinical hold for safety concerns, while another EZH2 inhibitor (GSK126) demonstrated insufficient efficacy during a Phase I/II trial. It is important to understand these risks as PRC2 therapies progress through clinic evaluation. Alternative approaches to target PRC2 may offer distinct advantages over the inhibition of EZH2, including the potential to overcome EZH2 resistance mutations. However, these emerging modalities may also incur new challenges as they progress toward the clinic. Nonetheless, the diversity of agents under development represents a wealth of therapeutic options for future patients.

Discovery of AZD9833, a Potent and Orally Bioavailable Selective Estrogen Receptor Degrader and Antagonist.

Herein we report the optimization of a series of tricyclic indazoles as selective estrogen receptor degraders (SERD) and antagonists for the treatment of ER+ breast cancer. Structure based design together with systematic investigation of each region of the molecular architecture led to the identification of N-[1-(3-fluoropropyl)azetidin-3-yl]-6-[(6S,8R)-8-methyl-7-(2,2,2-trifluoroethyl)-6,7,8,9-tetrahydro-3H-pyrazolo[4,3-f]isoquinolin-6-yl]pyridin-3-amine (28). This compound was demonstrated to be a highly potent SERD that showed a pharmacological profile comparable to fulvestrant in its ability to degrade ERα in both MCF-7 and CAMA-1 cell lines. A stringent control of lipophilicity ensured that 28 had favorable physicochemical and preclinical pharmacokinetic properties for oral administration. This, combined with demonstration of potent in vivo activity in mouse xenograft models, resulted in progression of this compound, also known as AZD9833, into clinical trials.

Demonstration of the utility of DOS-derived fragment libraries for rapid hit derivatisation in a multidirectional fashion.

Organic synthesis underpins the evolution of weak fragment hits into potent lead compounds. Deficiencies within current screening collections often result in the requirement of significant synthetic investment to enable multidirectional fragment growth, limiting the efficiency of the hit evolution process. Diversity-oriented synthesis (DOS)-derived fragment libraries are constructed in an efficient and modular fashion and thus are well-suited to address this challenge. To demonstrate the effective nature of such libraries within fragment-based drug discovery, we herein describe the screening of a 40-member DOS library against three functionally distinct biological targets using X-Ray crystallography. Firstly, we demonstrate the importance for diversity in aiding hit identification with four fragment binders resulting from these efforts. Moreover, we also exemplify the ability to readily access a library of analogues from cheap commercially available materials, which ultimately enabled the exploration of a minimum of four synthetic vectors from each molecule. In total, 10-14 analogues of each hit were rapidly accessed in three to six synthetic steps. Thus, we showcase how DOS-derived fragment libraries enable efficient hit derivatisation and can be utilised to remove the synthetic limitations encountered in early stage fragment-based drug discovery.

The Next Generation of Pattern Recognition Receptor Agonists: Improving Response Rates in Cancer Immunotherapy.

The recent success of checkpoint blocking antibodies has sparked a revolution in cancer immunotherapy. Checkpoint inhibition activates the adaptive immune system leading to durable responses across a range of tumor types, although this response is limited to patient populations with pre-existing tumor-infiltrating T cells. Strategies to stimulate the immune system to prime an antitumor response are of intense interest and several groups are now working to develop agents to activate the Pattern Recognition Receptors (PRRs), proteins which detect pathogenic and damageassociated molecules and respond by activating the innate immune response. Although early efforts focused on the Toll-like Receptor (TLR) family of membrane-bound PRRs, TLR activation has been associated with both pro- and antitumor effects. Nonetheless, TLR agonists have been deployed as potential anticancer agents in a range of clinical trials. More recently, the cytosolic PRR Stimulator of IFN Genes (STING) has attracted attention as another promising target for anticancer drug development, with early clinical data beginning to emerge. Besides STING, several other cytosolic PRR targets have likewise captured the interest of the drug discovery community, including the RIG-Ilike Receptors (RLRs) and NOD-like Receptors (NLRs). In this review, we describe the outlook for activators of PRRs as anticancer therapeutic agents and contrast the earlier generation of TLR agonists with the emerging focus on cytosolic PRR activators, both as single agents and in combination with other cancer immunotherapies.

EED-Targeted PROTACs Degrade EED, EZH2, and SUZ12 in the PRC2 Complex.

Deregulation of the PRC2 complex, comprised of the core subunits EZH2, SUZ12, and EED, drives aberrant hypermethylation of H3K27 and tumorigenicity of many cancers. Although inhibitors of EZH2 have shown promising clinical activity, preclinical data suggest that resistance can be acquired through secondary mutations in EZH2 that abrogate drug target engagement. To address these limitations, we have designed several hetero-bifunctional PROTACs (proteolysis-targeting chimera) to efficiently target EED for elimination. Our PROTACs bind to EED (pKD ∼ 9.0) and promote ternary complex formation with the E3 ubiquitin ligase. The PROTACs potently inhibit PRC2 enzyme activity (pIC50 ∼ 8.1) and induce rapid degradation of not only EED but also EZH2 and SUZ12 within the PRC2 complex. Furthermore, the PROTACs selectively inhibit proliferation of PRC2-dependent cancer cells (half maximal growth inhibition [GI50] = 49-58 nM). In summary, our data demonstrate a therapeutic modality to target PRC2-dependent cancer through a PROTAC-mediated degradation mechanism.

Rapid Identification of Novel Allosteric PRC2 Inhibitors.

Enhancer of zeste homologue 2 (EZH2), the catalytic subunit of polycomb repressive complex 2 (PRC2), regulates chromatin state and gene expression by methylating histone H3 lysine 27. EZH2 is overexpressed or mutated in various hematological malignancies and solid cancers. Our previous efforts to identify inhibitors of PRC2 methyltransferase activity by high-throughput screening (HTS) resulted in large numbers of false positives and thus a significant hit deconvolution challenge. More recently, others have reported compounds that bind to another PRC2 core subunit, EED, and allosterically inhibit EZH2 activity. This mechanism is particularly appealing as it appears to retain potency in cell lines that have acquired resistance to orthosteric EZH2 inhibition. By designing a fluorescence polarization probe based on the reported EED binding compounds, we were able to quickly and cleanly re-triage our previously challenging HTS hit list and identify novel allosteric PRC2 inhibitors.

Efficient development of stable and highly functionalised peptides targeting the CK2α/CK2ß protein-protein interaction.

The discovery of new Protein-Protein Interaction (PPI) modulators is currently limited by the difficulties associated with the design and synthesis of selective small molecule inhibitors. Peptides are a potential solution for disrupting PPIs; however, they typically suffer from poor stability in vivo and limited tissue penetration hampering their wide spread use as new chemical biology tools and potential therapeutics. In this work, a combination of CuAAC chemistry, molecular modelling, X-ray crystallography, and biological validation allowed us to develop highly functionalised peptide PPI inhibitors of the protein CK2. The lead peptide, CAM7117, prevents the formation of the holoenzyme assembly in vitro, slows down proliferation, induces apoptosis in cancer cells and is stable in human serum. CAM7117 could aid the development of novel CK2 inhibitors acting at the interface and help to fully understand the intracellular pathways involving CK2. Importantly, the approach adopted herein could be applied to many PPI targets and has the potential to ease the study of PPIs by efficiently providing access to functionalised peptides.

Stapled peptides as a new technology to investigate protein-protein interactions in human platelets.

Platelets are blood cells with numerous crucial pathophysiological roles in hemostasis, cardiovascular thrombotic events and cancer metastasis. Platelet activation requires the engagement of intracellular signalling pathways that involve protein-protein interactions (PPIs). A better understanding of these pathways is therefore crucial for the development of selective anti-platelet drugs. New strategies for studying PPIs in human platelets are required to overcome limitations associated with conventional platelet research methods. For example, small molecule inhibitors can lack selectivity and are often difficult to design and synthesise. Additionally, development of transgenic animal models is costly and time-consuming and conventional recombinant techniques are ineffective due to the lack of a nucleus in platelets. Herein, we describe the generation of a library of novel, functionalised stapled peptides and their first application in the investigation of platelet PPIs. Moreover, the use of platelet-permeable stapled Bim BH3 peptides confirms the part of Bim in phosphatidyl-serine (PS) exposure and reveals a role for the Bim protein in platelet activatory processes. Our work demonstrates that functionalised stapled peptides are a complementary alternative to conventional platelet research methods, and could make a significant contribution to the understanding of platelet signalling pathways and hence to the development of anti-platelet drugs.

C-H Activation Enables a Concise Total Synthesis of Quinine and Analogues with Enhanced Antimalarial Activity.

We report a novel approach to the classical natural product quinine that is based on two stereoselective key steps, namely a C-H activation and an aldol reaction, to unite the two heterocyclic moieties of the target molecule. This straightforward and flexible strategy enables a concise synthesis of natural (-)-quinine, the first synthesis of unnatural (+)-quinine, and also provides access to unprecedented C3-aryl analogues, which were prepared in only six steps. We additionally demonstrate that these structural analogues exhibit improved antimalarial activity compared with (-)-quinine both in vitro and in mice infected with Plasmodium berghei.

Guanidine-based α2-adrenoceptor ligands: Towards selective antagonist activity.

Depression has been linked to a selective increase in the high affinity conformation of the α2-adrenergic autoreceptors (α2-ARs) in the human brain as well as to an overexpression of α2-ARs in the hippocampus and cerebral cortex. Thus, the development of novel α2-AR antagonists represents an attractive source of new antidepressants. This paper describes the design, synthesis and pharmacological evaluation of 30 new guanidinium and 2-iminoimidazolidinium as potential α2-AR antagonists. In order to design this new series of α2-AR antagonists, a pharmacophore model was developed using the GALAHAD software. This study suggested that increased substitution in the space surrounding the cationic guanidine moiety might lead selectively to antagonist activity. Following the preparation of compounds incorporating this feature and competitive radioligand binding, [(35)S]GTPγS functional assays revealed that this structural modification affords exclusively α2-AR antagonists, in contrast with the analogous unsubstituted compounds in which a mixture of antagonist/agonist activities was previously observed.

Dual nucleophilic/electrophilic capture of in situ generated iminium ethers: towards the synthesis of functionalized amide building blocks.

Rearranging its feathers: The transformation of simple linear amides into a diverse range of branched, functionalized products by conversion to iminium esters is followed by sequential treatment with nucleophiles and electrophiles (see scheme). The method takes advantage of a novel Claisen rearrangement and the use of aromatic substrates greatly facilitates the formation of the intermediate iminium ether.