The Discovery of Exarafenib (KIN-2787): Overcoming the Challenges of Pan-RAF Kinase Inhibition.

RAF, a core signaling component of the MAPK kinase cascade, is often mutated in various cancers, including melanoma, lung, and colorectal cancers. The approved inhibitors were focused on targeting the BRAFV600E mutation that results in constitutive activation of kinase signaling through the monomeric protein (Class I). However, these inhibitors also paradoxically activate kinase signaling of RAF dimers, resulting in increased MAPK signaling in normal tissues. Recently, significant attention has turned to targeting RAF alterations that activate dimeric signaling (class II and III BRAF and NRAS). However, the discovery of a potent and selective inhibitor with biopharmaceutical properties suitable to sustain robust target inhibition in the clinical setting has proven challenging. Herein, we report the discovery of exarafenib (15), a highly potent and selective inhibitor that intercepts the RAF protein in the dimer compatible αC-helix-IN conformation and demonstrates anti-tumor efficacy in preclinical models with BRAF class I, II, and III and NRAS alterations.

TACH101, a first-in-class pan-inhibitor of KDM4 histone demethylase.

Histone lysine demethylase 4 (KDM4) is an epigenetic regulator that facilitates the transition between transcriptionally silent and active chromatin states by catalyzing the removal of methyl groups on histones H3K9, H3K36, and H1.4K26. KDM4 overamplification or dysregulation has been reported in various cancers and has been shown to drive key processes linked to tumorigenesis, such as replicative immortality, evasion of apoptosis, metastasis, DNA repair deficiency, and genomic instability. KDM4 also plays a role in epigenetic regulation of cancer stem cell renewal and has been linked to more aggressive disease and poorer clinical outcomes. The KDM4 family is composed of four main isoforms (KDM4A-D) that demonstrate functional redundancy and cross-activity; thus, selective inhibition of one isoform appears to be ineffective and pan-inhibition targeting multiple KDM4 isoforms is required. Here, we describe TACH101, a novel, small-molecule pan-inhibitor of KDM4 that selectively targets KDM4A-D with no effect on other KDM families. TACH101 demonstrated potent antiproliferative activity in cancer cell lines and organoid models derived from various histologies, including colorectal, esophageal, gastric, breast, pancreatic, and hematological malignancies. In vivo , potent inhibition of KDM4 led to efficient tumor growth inhibition and regression in several xenograft models. A reduction in the population of tumor-initiating cells was observed following TACH101 treatment. Overall, these observations demonstrate the broad applicability of TACH101 as a potential anticancer agent and support its advancement into clinical trials.

Discovery of CC-90011: A Potent and Selective Reversible Inhibitor of Lysine Specific Demethylase 1 (LSD1).

Histone demethylase LSDl (KDMlA) belongs to the flavin adenine dinucleotide (FAD) dependent family of monoamine oxidases and is vital in regulation of mammalian biology. Dysregulation and overexpression of LSD1 are hallmarks of a number of human diseases, particularly cancers that are characterized as morphologically poorly differentiated. As such, inhibitors of LSD1 have potential to be beneficial as a cancer therapy. The most clinically advanced inhibitors of LSDl are covalent inhibitors derived from tranylcypromine (TCP). Herein, we report the discovery of a novel series of reversible and selective LSDl inhibitors. Exploration of structure-activity relationships (SARs) and optimization of ADME properties resulted in the identification of clinical candidate CC-90011. CC-90011 exhibits potent on-target induction of cellular differentiation in acute myeloid leukemia (AML) and small cell lung cancer (SCLC) cell lines, and antitumor efficacy in patient-derived xenograft (PDX) SCLC models. CC-90011 is currently in phase 2 trials in patients with first line, extensive stage SCLC (ClinicalTrials.gov identifier: NCT03850067).

Structure-based design and discovery of potent and selective lysine-specific demethylase 1 (LSD1) inhibitors.

The histone demethylase LSD1 is a key enzyme in the epigenetic regulation of gene transcription. Here we present our efforts to discover small molecule reversible inhibitors of LSD1 as an attractive approach to treat hematologic malignancies and certain solid tumors. Using structure-based drug design, we designed and synthesized a novel series of heteroaromatic imidazole inhibitors that demonstrate potent inhibition of the demethylase activity and low nanomolar cell-based activity. This novel LSD1 inhibitor series was further optimized by attenuating the hERG inhibition and improving oral bioavailability.

Design of KDM4 Inhibitors with Antiproliferative Effects in Cancer Models.

Histone lysine demethylases (KDMs) play a vital role in the regulation of chromatin-related processes. Herein, we describe our discovery of a series of potent KDM4 inhibitors that are both cell permeable and antiproliferative in cancer models. The modulation of histone H3K9me3 and H3K36me3 upon compound treatment was verified by homogeneous time-resolved fluorescence assay and by mass spectroscopy detection. Optimization of the series using structure-based drug design led to compound 6 (QC6352), a potent KDM4 family inhibitor that is efficacious in breast and colon cancer PDX models.