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.

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.

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.

Potent and Selective Inhibitors of the Epidermal Growth Factor Receptor to Overcome C797S-Mediated Resistance.

The epidermal growth factor receptor (EGFR) harboring activating mutations is a clinically validated target in non-small-cell lung cancer, and a number of inhibitors of the EGFR tyrosine kinase domain, including osimertinib, have been approved for clinical use. Resistance to these therapies has emerged due to a variety of molecular events including the C797S mutation which renders third-generation C797-targeting covalent EGFR inhibitors considerably less potent against the target due to the loss of the key covalent-bond-forming residue. We describe the medicinal chemistry optimization of a biochemically potent but modestly cell-active, reversible EGFR inhibitor starting point with sub-optimal physicochemical properties. These studies culminated in the identification of compound 12 that showed improved cell potency, oral exposure, and in vivo activity in clinically relevant EGFR-mutant-driven disease models, including an Exon19 deletion/T790M/C797S triple-mutant mouse xenograft model.

Expeditious Access to Functionalized Tricyclic Pyrrolo-Pyridones via Tandem or Sequential C-N/C-C Bond Formations.

The facile synthesis of both saturated and unsaturated tricyclic pyrrolo-pyridones starting from a single readily available, common monocyclic reagent has been developed. An intermolecular annulation via a tandem Buchwald-Hartwig/Heck reaction led to the synthesis of ß-carbolinones. The analogous semisaturated tricyclic pyrrolo-pyridones were prepared in good to excellent yields by sequential Buchwald-Hartwig and Fischer indole reactions. The methods feature mild reaction conditions and good functional group tolerance.

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.