Discovery of 3(S)-thiomethyl pyrrolidine ERK inhibitors for oncology.

Compound 5 (SCH772984) was identified as a potent inhibitor of ERK1/2 with excellent selectivity against a panel of kinases (0/231 kinases tested @ 100 nM) and good cell proliferation activity, but suffered from poor PK (rat AUC PK @10 mpk = 0 µM h; F% = 0) which precluded further development. In an effort to identify novel ERK inhibitors with improved PK properties with respect to 5, a systematic exploration of sterics and composition at the 3-position of the pyrrolidine led to the discovery of a novel 3(S)-thiomethyl pyrrolidine analog 28 with vastly improved PK (rat AUC PK @10 mpk = 26 µM h; F% = 70).

Regioselective Bromination of Thieno[2',3':4,5]pyrrolo[1,2-d][1,2,4]triazin-8(7H)-one and Sequential Suzuki Couplings.

Regioselective bromination of thieno[2',3':4,5]pyrrolo[1,2-d][1,2,4]triazin-8(7H)-one at the 2- or 9-position was achieved by modulating the basicity of the reaction conditions. An anion-directed site-specific bromination mechanism was proposed. In addition, a one-pot bromination-Suzuki coupling protocol was developed for quick access of analogues at the 9-position.

Discovery of novel BTK inhibitors with carboxylic acids.

We report the design and synthesis of a series of novel Bruton's Tyrosine Kinase (BTK) inhibitors with a carboxylic acid moiety in the ribose pocket. This series of compounds has demonstrated much improved off-target selectivities including adenosine uptake (AdU) inhibition compared to the piperidine amide series. Optimization of the initial lead compound 4 based on BTK enzyme inhibition, and human peripheral blood mononuclear cell (hPBMC) and human whole blood (hWB) activity led to the discovery of compound 40, with potent BTK inhibition, reduced off target activities, as well as favorable pharmacokinetic profile in both rat and dog.

Discovery of 3-morpholino-imidazole[1,5-a]pyrazine BTK inhibitors for rheumatoid arthritis.

8-Amino-imidazo[1,5-a]pyrazine-based Bruton's tyrosine kinase (BTK) inhibitors, such as 6, exhibited potent inhibition of BTK but required improvements in both kinase and hERG selectivity (Liu et al., 2016; Gao et al., 2017). In an effort to maintain the inhibitory activity of these analogs and improve their selectivity profiles, we carried out SAR exploration of groups at the 3-position of pyrazine compound 6. This effort led to the discovery of the morpholine group as an optimized pharmacophore. Compounds 13, 23 and 38 displayed excellent BTK potencies, kinase and hERG selectivities, and pharmacokinetic profiles.

Discovery of hydroxyaniline amides as selective Extracellular Regulated Kinase (Erk) inhibitors.

Starting from weak µM hits identified through affinity based Automated Ligand Identification System (ALIS) screenings, double digit nM hydroxyaniline amide Erk inhibitors were discovered. This class of compounds had the unique dual mechanism of inhibiting activated and non-activated forms of Erk. They generally had high degree of selectivity in kinase panel tested.

New class of azaheptapyridine FPT inhibitors as potential cancer therapy agents.

Tertiary hydroxyl class of C-imidazole bridgehead azaheptapyridine FPT inhibitors were prepared in an attempt to block in vivo oxidation of secondary hydroxyl series. One representative compound 5a exhibited potent enzyme (IC50=1.4 nM) and cellular activities (soft agar IC50=1.3 nM) with excellent oral pharmacokinetic profiles in rats, mice, monkeys and dogs. The in vivo study in wap-ras TG mouse models showed dose dependent tumor growth inhibition and regression.

Discovery of C-imidazole azaheptapyridine FPT inhibitors.

The discovery of C-linked imidazole azaheptapyridine bridgehead FPT inhibitors is described. This novel class of compounds are sub nM FPT enzyme inhibitors with potent cellular inhibitory activities. This series also has reduced hERG activity versus previous N-linked imidazole series. X-ray of compound 10a bound to FTase revealed strong interaction between bridgehead imidazole 3N with catalytic zinc atom.

Direct photochemical cross-coupling between aliphatic acids and BF3K salts.

We describe a novel photoredox hetero-coupling reaction of two C (sp3) radicals from aliphatic acids or BF3K salts. The kinetic differences in radical persistence provide cross-selectivity, using an organic photoredox catalyst and an oxidant with visible light. This method exhibits broad scope, including several examples constructing sterically hindered C(sp3)-C(sp3) bonds.

Crystal structures of MEK1 binary and ternary complexes with nucleotides and inhibitors.

MEK1 is a member of the MAPK signal transduction pathway that responds to growth factors and cytokines. We have determined that the kinase domain spans residues 35-382 by proteolytic cleavage. The complete kinase domain has been crystallized and its X-ray crystal structure as a complex with magnesium and ATP-gammaS determined at 2.1 A. Unlike crystals of a truncated kinase domain previously published, the crystals of the intact domain can be grown either as a binary complex with a nucleotide or as a ternary complex with a nucleotide and one of a multitude of allosteric inhibitors. Further, the crystals allow for the determination of costructures with ATP competitive inhibitors. We describe the structures of nonphosphorylated MEK1 (npMEK1) binary complexes with ADP and K252a, an ATP-competitive inhibitor (see Table 1), at 1.9 and 2.7 A resolution, respectively. Ternary complexes have also been solved between npMEK1, a nucleotide, and an allosteric non-ATP competitive inhibitor: ATP-gammaS with compound 1 and ADP with either U0126 or the MEK1 clinical candidate PD325089 at 1.8, 2.0, and 2.5 A, respectively. Compound 1 is structurally similar to PD325901. These structures illustrate fundamental differences among various mechanisms of inhibition at the molecular level. Residues 44-51 have previously been shown to play a negative regulatory role in MEK1 activity. The crystal structure of the integral kinase domain provides a structural rationale for the role of these residues. They form helix A and repress enzymatic activity by stabilizing an inactive conformation in which helix C is displaced from its active state position. Finally, the structure provides for the first time a molecular rationale that explains how mutations in MEK may lead to the cardio-facio-cutaneous syndrome.

Achieving High-Quality Sn-Pb Perovskite Films on Complementary Metal-Oxide-Semiconductor-Compatible Metal/Silicon Substrates for Efficient Imaging Array.

Although Sn-Pb perovskites sensing near-ultraviolet-visible-near-infrared light could be an attractive alternative to silicon in photodiodes and imaging, there have been no clear studies on such devices constructed on metal/silicon substrates, hindering their direct integration with complementary metal-oxide semiconductor (CMOS) and silicon electronics. Typically, high surface roughness and severe pinholes of Sn-rich binary perovskites make it difficult for them to fulfill the requirements of efficient photodiodes and imaging. These issues cause inherently high dark current and poor (dark and photo-) current uniformity. Herein, we propose and demonstrate the room-temperature crystallization in the Sn-rich binary perovskite system to effectively control film crystallization kinetics. With experimental and theoretical studies of the crystallization mechanism, we successfully tune the density and location of nanocrystals in precursor films to achieve compact nanocrystals, which coalesce into high-quality (smooth, dense, and pinhole-free) perovskites with intensified preferred orientation and decreased trap density. The high-quality perovskites reduce dark current and improve (dark and photo-) current uniformity of perovskite photodiodes on CMOS-compatible metal/silicon substrates. Meanwhile, self-powered devices achieve a high responsivity of 0.2 A/W at 940 nm, a large dynamic range of 100 dB, and a fast fall time of 2.27 µs, exceeding those of most silicon-based imaging sensors. Finally, a 6 × 6 pixel integrated photodiode array is successfully demonstrated to realize the imaging application. The work contributes to understanding the fundamentals of the crystallization of Sn-rich binary perovskites and advancing perovskite integration with Si-based electronics.

Discovery of Small-Molecule Antagonists of the H3K9me3 Binding to UHRF1 Tandem Tudor Domain.

Ubiquitin-like with PHD and RING finger domains 1 (UHRF1) is a multidomain protein that plays a critical role in maintaining DNA methylation patterns through concurrent recognition of hemimethylated DNA and histone marks by various domains, and recruitment of DNA methyltransferase 1 (DNMT1). UHRF1 is overexpressed in various cancers, including breast cancer. The tandem tudor domain (TTD) of UHRF1 specifically and tightly binds to histone H3 di- or trimethylated at lysine 9 (H3K9me2 or H3K9me3, respectively), and this binding is essential for UHRF1 function. We developed an H3K9me3 peptide displacement assay, which was used to screen a library of 44,000 compounds for small molecules that disrupt the UHRF1-H3K9me3 interaction. This screen resulted in the identification of NV01, which bound to UHRF1-TTD with a Kd value of 5 µM. The structure of UHRF1-TTD in complex with NV01 confirmed binding to the H3K9me3-binding pocket. Limited structure-based optimization of NV01 led to the discovery of NV03 (Kd of 2.4 µM). These well-characterized small-molecule antagonists of the UHRF1-H3K9me2/3 interaction could be valuable starting chemical matter for developing more potent and cell-active probes toward further characterizing UHRF1 function, with possible applications as anticancer therapeutics.

MK-8353: Discovery of an Orally Bioavailable Dual Mechanism ERK Inhibitor for Oncology.

The emergence and evolution of new immunological cancer therapies has sparked a rapidly growing interest in discovering novel pathways to treat cancer. Toward this aim, a novel series of pyrrolidine derivatives (compound 5) were identified as potent inhibitors of ERK1/2 with excellent kinase selectivity and dual mechanism of action but suffered from poor pharmacokinetics (PK). The challenge of PK was overcome by the discovery of a novel 3(S)-thiomethyl pyrrolidine analog 7. Lead optimization through focused structure-activity relationship led to the discovery of a clinical candidate MK-8353 suitable for twice daily oral dosing as a potential new cancer therapeutic.

Discovery of Potent, Selective, and Structurally Novel Dot1L Inhibitors by a Fragment Linking Approach.

Misdirected catalytic activity of histone methyltransferase Dot1L is believed to be causative for a subset of highly aggressive acute leukemias. Targeting the catalytic domain of Dot1L represents a potential therapeutic approach for these leukemias. In the context of a comprehensive Dot1L hit finding strategy, a knowledge-based virtual screen of the Dot1L SAM binding pocket led to the discovery of 2, a non-nucleoside fragment mimicking key interactions of SAM bound to Dot1L. Fragment linking of 2 and 3, an induced back pocket binder identified in earlier studies, followed by careful ligand optimization led to the identification of 7, a highly potent, selective and structurally novel Dot1L inhibitor.

Room-Temperature Solution-Processed NiOx:PbI2 Nanocomposite Structures for Realizing High-Performance Perovskite Photodetectors.

While methylammonium lead iodide (MAPbI3) with interesting properties, such as a direct band gap, high and well-balanced electron/hole mobilities, as well as long electron/hole diffusion length, is a potential candidate to become the light absorbers in photodetectors, the challenges for realizing efficient perovskite photodetectors are to suppress dark current, to increase linear dynamic range, and to achieve high specific detectivity and fast response speed. Here, we demonstrate NiOx:PbI2 nanocomposite structures, which can offer dual roles of functioning as an efficient hole extraction layer and favoring the formation of high-quality MAPbI3 to address these challenges. We introduce a room-temperature solution process to form the NiOx:PbI2 nanocomposite structures. The nanocomposite structures facilitate the growth of the compact and ordered MAPbI3 crystalline films, which is essential for efficient photodetectors. Furthermore, the nanocomposite structures work as an effective hole extraction layer, which provides a large electron injection barrier and favorable hole extraction as well as passivates the surface of the perovskite, leading to suppressed dark current and enhanced photocurrent. By optimizing the NiOx:PbI2 nanocomposite structures, a low dark current density of 2 × 10(-10) A/cm(2) at -200 mV and a large linear dynamic range of 112 dB are achieved. Meanwhile, a high responsivity in the visible spectral range of 450-750 nm, a large measured specific detectivity approaching 10(13) Jones, and a fast fall time of 168 ns are demonstrated. The high-performance perovskite photodetectors demonstrated here offer a promising candidate for low-cost and high-performance near-ultraviolet-visible photodetection.

Discovery of Novel Dot1L Inhibitors through a Structure-Based Fragmentation Approach.

Oncogenic MLL fusion proteins aberrantly recruit Dot1L, a histone methyltransferase, to ectopic loci, leading to local hypermethylation of H3K79 and misexpression of HoxA genes driving MLL-rearranged leukemias. Inhibition of the methyltransferase activity of Dot1L in this setting is predicted to reverse aberrant H3K79 methylation, leading to repression of leukemogenic genes and tumor growth inhibition. In the context of our Dot1L drug discovery program, high-throughput screening led to the identification of 2, a weak Dot1L inhibitor with an unprecedented, induced pocket binding mode. A medicinal chemistry campaign, strongly guided by structure-based consideration and ligand-based morphing, enabled the discovery of 12 and 13, potent, selective, and structurally completely novel Dot1L inhibitors.

A general design rule to manipulate photocarrier transport path in solar cells and its realization by the plasmonic-electrical effect.

It is well known that transport paths of photocarriers (electrons and holes) before collected by electrodes strongly affect bulk recombination and thus electrical properties of solar cells, including open-circuit voltage and fill factor. For boosting device performance, a general design rule, tailored to arbitrary electron to hole mobility ratio, is proposed to decide the transport paths of photocarriers. Due to a unique ability to localize and concentrate light, plasmonics is explored to manipulate photocarrier transport through spatially redistributing light absorption at the active layer of devices. Without changing the active materials, we conceive a plasmonic-electrical concept, which tunes electrical properties of solar cells via the plasmon-modified optical field distribution, to realize the design rule. Incorporating spectrally and spatially configurable metallic nanostructures, thin-film solar cells are theoretically modelled and experimentally fabricated to validate the design rule and verify the plasmonic-tunable electrical properties. The general design rule, together with the plasmonic-electrical effect, contributes to the evolution of emerging photovoltaics.

Discovery of novel, dual mechanism ERK inhibitors by affinity selection screening of an inactive kinase.

An affinity-based mass spectrometry screening technology was used to identify novel binders to both nonphosphorylated and phosphorylated ERK2. Screening of inactive ERK2 identified a pyrrolidine analogue 1 that bound to both nonphosphorylated and phosphorylated ERK2 and inhibited ERK2 kinase activity. Chemical optimization identified compound 4 as a novel, potent, and highly selective ERK1,2 inhibitor which not only demonstrated inhibition of phosphorylation of ERK substrate p90RSK but also demonstrated inhibition of ERK1,2 phosphorylation on the activation loop. X-ray cocrystallography revealed that upon binding of compound 4 to ERK2, Tyr34 undergoes a rotation (flip) along with a shift in the poly-Gly rich loop to create a new binding pocket into which 4 can bind. This new binding mode represents a novel mechanism by which high affinity ATP-competitive compounds may achieve excellent kinase selectivity.

Discovery of a novel ERK inhibitor with activity in models of acquired resistance to BRAF and MEK inhibitors.

The high frequency of activating RAS or BRAF mutations in cancer provides strong rationale for targeting the mitogen-activated protein kinase (MAPK) pathway. Selective BRAF and MAP-ERK kinase (MEK) inhibitors have shown clinical efficacy in patients with melanoma. However, the majority of responses are transient, and resistance is often associated with pathway reactivation of the extracellular signal-regulated kinase (ERK) signaling pathway. Here, we describe the identification and characterization of SCH772984, a novel and selective inhibitor of ERK1/2 that displays behaviors of both type I and type II kinase inhibitors. SCH772984 has nanomolar cellular potency in tumor cells with mutations in BRAF, NRAS, or KRAS and induces tumor regressions in xenograft models at tolerated doses. Importantly, SCH772984 effectively inhibited MAPK signaling and cell proliferation in BRAF or MEK inhibitor-resistant models as well as in tumor cells resistant to concurrent treatment with BRAF and MEK inhibitors. These data support the clinical development of ERK inhibitors for tumors refractory to MAPK inhibitors.