Nigel James Parr

Discovery of Epigenetic Regulator I-Bet762: Lead Optimization to Afford a Clinical Candidate Inhibitor of the Bet Bromodomains.

The bromo and extra C-terminal domain (BET) family of bromodomains are involved in binding epigenetic marks on histone proteins, more specifically acetylated lysine residues. This paper describes the discovery and structure-activity relationships (SAR) of potent benzodiazepine inhibitors that disrupt the function of the BET family of bromodomains (BRD2, BRD3, and BRD4). This work has yielded a potent, selective compound I-BET762 that is now under evaluation in a phase I/II clinical trial for nuclear protein in testis (NUT) midline carcinoma and other cancers.

Selective inhibition of CD4+ T-cell cytokine production and autoimmunity by BET protein and c-Myc inhibitors

Bromodomain-containing proteins bind acetylated lysine residues on histone tails and are involved in the recruitment of additional factors that mediate histone modifications and enable transcription. A compound, I-BET-762, that inhibits binding of an acetylated histone peptide to proteins of the bromodomain and extra-terminal domain (BET) family, was previously shown to suppress the production of proinflammatory proteins by macrophages and block acute inflammation in mice. Here, we investigated the effect of short-term treatment with I-BET-762 on T-cell function. Treatment of naïve CD4+ T cells with I-BET-762 during the first 2 d of differentiation had long-lasting effects on subsequent gene expression and cytokine production. Gene expression analysis revealed up-regulated expression of several antiinflammatory gene products, including IL-10, Lag3, and Egr2, and down-regulated expression of several proinflammatory cytokines including GM-CSF and IL-17. The short 2-d treatment with I-BET-762 inhibited the ability of antigen-specific T cells, differentiated under Th1 but not Th17 conditions in vitro, to induce pathogenesis in an adoptive transfer model of experimental autoimmune encephalomyelitis. The suppressive effects of I-BET-762 on T-cell mediated inflammation in vivo were accompanied by decreased recruitment of macrophages, consistent with decreased GM-CSF production by CNS-infiltrating T cells. These effects were mimicked by an inhibitor of c-myc function, implicating reduced expression of c-myc and GM-CSF as one avenue by which I-BET-762 suppresses the inflammatory functions of T cells. Our study demonstrates that inhibiting the functions of BET-family proteins during early T-cell differentiation causes long-lasting suppression of the proinflammatory functions of Th1 cells.

BET Inhibition Silences Expression of MYCN and BCL2 and Induces Cytotoxicity in Neuroblastoma Tumor Models

BET family proteins are epigenetic regulators known to control expression of genes involved in cell growth and oncogenesis. Selective inhibitors of BET proteins exhibit potent anti-proliferative activity in a number of hematologic cancer models, in part through suppression of the MYC oncogene and downstream Myc-driven pathways. However, little is currently known about the activity of BET inhibitors in solid tumor models, and whether down-regulation of MYC family genes contributes to sensitivity. Here we provide evidence for potent BET inhibitor activity in neuroblastoma, a pediatric solid tumor associated with a high frequency of MYCN amplifications. We treated a panel of neuroblastoma cell lines with a novel small molecule inhibitor of BET proteins, GSK1324726A (I-BET726), and observed potent growth inhibition and cytotoxicity in most cell lines irrespective of MYCN copy number or expression level. Gene expression analyses in neuroblastoma cell lines suggest a role of BET inhibition in apoptosis, signaling, and N-Myc-driven pathways, including the direct suppression of BCL2 and MYCN. Reversal of MYCN or BCL2 suppression reduces the potency of I-BET726-induced cytotoxicity in a cell line-specific manner; however, neither factor fully accounts for I-BET726 sensitivity. Oral administration of I-BET726 to mouse xenograft models of human neuroblastoma results in tumor growth inhibition and down-regulation MYCN and BCL2 expression, suggesting a potential role for these genes in tumor growth. Taken together, our data highlight the potential of BET inhibitors as novel therapeutics for neuroblastoma, and suggest that sensitivity is driven by pleiotropic effects on cell growth and apoptotic pathways in a context-specific manner.

Potent antimyeloma activity of the novel bromodomain inhibitors I-BET151 and I-BET762.

The bromodomain and extraterminal (BET) protein BRD2-4 inhibitors hold therapeutic promise in preclinical models of hematologic malignancies. However, translation of these data to molecules suitable for clinical development has yet to be accomplished. Herein we expand the mechanistic understanding of BET inhibitors in multiple myeloma by using the chemical probe molecule I-BET151. I-BET151 induces apoptosis and exerts strong antiproliferative effect in vitro and in vivo. This is associated with contrasting effects on oncogenic MYC and HEXIM1, an inhibitor of the transcriptional activator P-TEFb. I-BET151 causes transcriptional repression of MYC and MYC-dependent programs by abrogating recruitment to the chromatin of the P-TEFb component CDK9 in a BRD2-4-dependent manner. In contrast, transcriptional upregulation of HEXIM1 is BRD2-4 independent. Finally, preclinical studies show that I-BET762 has a favorable pharmacologic profile as an oral agent and that it inhibits myeloma cell proliferation, resulting in survival advantage in a systemic myeloma xenograft model. These data provide a strong rationale for extending the clinical testing of the novel antimyeloma agent I-BET762 and reveal insights into biologic pathways required for myeloma cell proliferation.

Generation of a Selective Small Molecule Inhibitor of the CBP/p300 Bromodomain for Leukemia Therapy

The histone acetyltransferases CBP/p300 are involved in recurrent leukemia-associated chromosomal translocations and are key regulators of cell growth. Therefore, efforts to generate inhibitors of CBP/p300 are of clinical value. We developed a specific and potent acetyl-lysine competitive protein-protein interaction inhibitor, I-CBP112, that targets the CBP/p300 bromodomains. Exposure of human and mouse leukemic cell lines to I-CBP112 resulted in substantially impaired colony formation and induced cellular differentiation without significant cytotoxicity. I-CBP112 significantly reduced the leukemia-initiating potential of MLL-AF9(+) acute myeloid leukemia cells in a dose-dependent manner in vitro and in vivo. Interestingly, I-CBP112 increased the cytotoxic activity of BET bromodomain inhibitor JQ1 as well as doxorubicin. Collectively, we report the development and preclinical evaluation of a novel, potent inhibitor targeting CBP/p300 bromodomains that impairs aberrant self-renewal of leukemic cells. The synergistic effects of I-CBP112 and current standard therapy (doxorubicin) as well as emerging treatment strategies (BET inhibition) provide new opportunities for combinatorial treatment of leukemia and potentially other cancers.

Solid-phase reaction monitoring--chemical derivatization and off-bead analysis.

The aim of this review is to give a compendium of colorimetric assays and spectrophotometric-based quantification methods applicable to solid-phase organic chemistry. Comprehensive experimental details for commonly employed color tests performed on solid support will be documented.

The structure based design of dual HDAC/BET inhibitors as novel epigenetic probes

Herein we describe the design and synthesis of a dual active histone deacetylase (HDAC)/bromodomain and extra terminal (BET) small molecule tool inhibitor, DUAL946 (1). Exploiting our extensive epigenetic toolbox, we achieved the functionalisation of a BET active tetrahydroquinoline (THQ) core, with a hydroxamic acid HDAC inhibitor (HDACi) motif. Dual inhibition of BET and HDAC proteins was confirmed by in vitro biochemical and biophysical testing and through chemoproteomic competition experiments in cell lysates. This activity was translated into potent cellular activity in both immune and cancer cells.

Light-fluorous safety-catch arylgermanes - exceptionally robust, photochemically activated precursors for biaryl synthesis by Pd(0) catalysed cross-coupling.

A new class of arylgermane derivative that participate efficiently in Pd(0)-catalysed cross-coupling reactions with aryl bromides following photochemical activation is described.

Abstract CT014: GSK525762, a selective bromodomain (BRD) and extra terminal protein (BET) inhibitor: results from part 1 of a phase I/II open-label single-agent study in patients with NUT midline carcinoma (NMC) and other cancers

Background: GSK525762 is a potent, selective pan-BET inhibitor that abrogates binding of BET family proteins (BRD2, BRD3, BRD4 and BRD-T) to acetylated histones. In pre-clinical models this results in suppression of BET target genes that drive oncogenic pathways, resulting in growth inhibition of cancer cell lines (median IC50 of 50-1698 nM for solid tumors and 50 nM for NMC). GSK525762 is being evaluated clinically for treatment of pts with hematologic malignancies and solid tumors including NMC, a rare, aggressive cancer with few treatment options. NMC is characterized by BRD3-/BRD4-NUT fusion oncoproteins that represents a rational therapeutic target for BET inhibitors. Methods: Primary objectives of Part 1 were to determine safety, tolerability, and maximum tolerated dose (MTD) for GSK525762 in solid tumors, using a combined N-CRM and 3+3 dose escalation. Secondary objectives include PK and PD analysis and preliminary evaluation of activity. Oral once daily (qd) and twice daily (bid) schedules have been evaluated. PD activity was assessed with [18F]-deoxy-glucose-PET scans and changes in cytokine release from LPS-stimulated PBMC of treated pts. The dose-limiting toxicity (DLT) observation period was 28 days. Response evaluation was by RECIST 1.1 and pts were followed to disease progression, discontinuation due to adverse events, withdrawal of consent or death. Results: As of 28-Jan 2016, a total of 70 (including 17 NMC) pts have been treated at doses of 2-100 mg qd and 20 and 30 mg bid. The most common adverse events (all grades, ?20%) observed were thrombocytopenia (44%), nausea (40%), vomiting (29%), anemia (26%), fatigue (26%), decreased appetite (24%), diarrhoea (23%) and dysgeusia (20%). DLTs occurred in 5 pts at doses of 60 mg (n = 1, 11%), 80 mg (n = 3, 14%) and 100 mg (n = 1, 11%). The most common AEs leading to dose interruption were thrombocytopenia and hyperbilirubinemia (each n = 7, 10%). Limited data shows similar tolerability at bid doses. PK was dose-proportional after single and repeat dosing with large between patient variability. Dose dependent inhibition of LPS stimulated BRD regulated cytokine (IL-6, TNF-α, MCP-1, IL-8) release suggests target engagement. Of 11 NMC pts treated at 60-100 mg qd, evaluation is awaited on 1 pt. Of 10 pts evaluated, 2 (20%; 95% CI (2.5%, 56%)) had confirmed PR (15 and 23 weeks) and 4 (40%; 95% CI (12%, 74%)) had SD. An 80mg once-daily dose will be evaluated in NMC and other solid tumor expansion cohorts. Conclusion: GSK525762 is an active, orally bio-available BET inhibitor showing dose-proportional PK and good tolerability up to 80 mg qd dosing. Preliminary evidence of clinical activity observed in pts with NMC provides a rational targeted therapy for this aggressive tumor and proof of concept for BET inhibitors in the clinic. Study funded by GSK (NCT01587703). Citation Format: Peter J. O’Dwyer, Sarina A. Piha-Paul, Christopher French, Sara Harward, Gerladine Ferron-Brady, Yuehui Wu, Olena Barbash, Anastasia Wyce, Meg Annan, Thierry Horner, Nigel J. Parr, Rab K. Prinjha, Christopher Carpenter, Geoffrey Shapiro, Arindam Dhar, Christine Hann. GSK525762, a selective bromodomain (BRD) and extra terminal protein (BET) inhibitor: results from part 1 of a phase I/II open-label single-agent study in patients with NUT midline carcinoma (NMC) and other cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT014.