Joey L. Methot

Exploration of the internal cavity of histone deacetylase (HDAC) with selective HDAC1/HDAC2 inhibitors (SHI-1:2)

We report herein the initial exploration of novel selective HDAC1/HDAC2 inhibitors (SHI-1:2). Optimized SHI-1:2 structures exhibit enhanced intrinsic activity against HDAC1 and HDAC2, and are greater than 100-fold selective versus other HDACs, including HDAC3. Based on the SAR of these agents and our current understanding of the HDAC active site, we postulate that the SHI-1:2 extend the existing HDAC inhibitor pharmacophore to include an internal binding domain.

SAR profiles of spirocyclic nicotinamide derived selective HDAC1/HDAC2 inhibitors (SHI-1:2)

A potent family of spirocyclic nicotinyl aminobenzamide selective HDAC1/HDAC2 inhibitors (SHI-1:2) is profiled. The incorporation of a biaryl zinc-binding motif into a nicotinyl scaffold resulted in enhanced potency and selectivity versus HDAC3, but also imparted hERG activity. It was discovered that increasing polar surface area about the spirocycle attenuates this liability. Compound 12 induced a 4-fold increase in acetylated histone H2B in an HCT-116 xenograft model study with acute exposure, and inhibited tumor growth in a 21-day efficacy study with qd dosing.

Molecular and biologic analysis of histone deacetylase inhibitors with diverse specificities.

Histone deacetylase inhibitors (HDACi) are anticancer agents that induce hyperacetylation of histones, resulting in chromatin remodeling and transcriptional changes. In addition, nonhistone proteins, such as the chaperone protein Hsp90, are functionally regulated through hyperacetylation mediated by HDACis. Histone acetylation is thought to be primarily regulated by HDACs 1, 2, and 3, whereas the acetylation of Hsp90 has been proposed to be specifically regulated through HDAC6. We compared the molecular and biologic effects induced by an HDACi with broad HDAC specificity (vorinostat) with agents that predominantly inhibited selected class I HDACs (MRLB-223 and romidepsin). MRLB-223, a potent inhibitor of HDACs 1 and 2, killed tumor cells using the same apoptotic pathways as the HDAC 1, 2, 3, 6, and 8 inhibitor vorinostat. However, vorinostat induced histone hyperacetylation and killed tumor cells more rapidly than MRLB-223 and had greater therapeutic efficacy in vivo. FDCP-1 cells dependent on the Hsp90 client protein Bcr-Abl for survival, were killed by all HDACis tested, concomitant with caspase-dependent degradation of Bcr-Abl. These studies provide evidence that inhibition of HDAC6 and degradation of Bcr-Abl following hyperacetylation of Hsp90 is likely not a major mechanism of action of HDACis as had been previously posited. Mol Cancer Ther; 12(12); 2709–21. ©2013 AACR.

Parallel medicinal chemistry approaches to selective HDAC1/HDAC2 inhibitor (SHI-1:2) optimization

The successful application of both solid and solution phase library synthesis, combined with tight integration into the medicinal chemistry effort, resulted in the efficient optimization of a novel structural series of selective HDAC1/HDAC2 inhibitors by the MRL-Boston Parallel Medicinal Chemistry group. An initial lead from a small parallel library was found to be potent and selective in biochemical assays. Advanced compounds were the culmination of iterative library design and possess excellent biochemical and cellular potency, as well as acceptable PK and efficacy in animal models.

Triazoles as γ-secretase modulators.

Synthesis, SAR, and evaluation of aryl triazoles as novel gamma secretase modulators (GSMs) are presented in this communication. Starting from the literature and in-house leads, we evaluated a range of five-membered heterocycles as replacements for olefins commonly found in non-acid GSMs. 1,2,3-C-aryl-triazoles were identified as suitable replacements which exhibited good modulation of γ-secretase activity, excellent pharmacokinetics and good central lowering of Aβ42 in Sprague-Dawley rats.

Triazoloamides as potent γ-secretase modulators with reduced hERG liability.

Synthesis and SAR studies of novel aryl triazoles as gamma secretase modulators (GSMs) are presented in this communication. Starting from our aryl triazole leads, optimization studies were continued and the series progressed towards novel amides and lactams. Triazole 57 was identified as the most potent analog in this series, displaying single-digit nanomolar Aβ42 IC(50) in cell-based assays and reduced affinity for the hERG channel.

Discovery of 1-(1H-Pyrazolo[4,3-c]pyridin-6-yl)urea Inhibitors of Extracellular Signal-Regulated Kinase (ERK) for the Treatment of Cancers

The ERK/MAPK pathway plays a central role in the regulation of critical cellular processes and is activated in more than 30% of human cancers. Specific BRAF and MEK inhibitors have shown clinical efficacy in patients for the treatment of BRAF-mutant melanoma. However, the majority of responses are transient, and resistance is often associated with pathway reactivation of the ERK signal pathway. Acquired resistance to these agents has led to greater interest in ERK, a downstream target of the MAPK pathway. De novo design efforts of a novel scaffold derived from SCH772984 by employing hydrogen bond interactions specific for ERK in the binding pocket identified 1-(1H-pyrazolo[4,3-c]pyridin-6-yl)ureas as a viable lead series. Sequential SAR studies led to the identification of highly potent and selective ERK inhibitors with low molecular weight and high LE. Compound 21 exhibited potent target engagement and strong tumor regression in the BRAF(V600E) xenograft model.

Delayed and Prolonged Histone Hyperacetylation with a Selective HDAC1/HDAC2 Inhibitor.

The identification and in vitro and in vivo characterization of a potent SHI-1:2 are described. Kinetic analysis indicated that biaryl inhibitors exhibit slow binding kinetics in isolated HDAC1 and HDAC2 preparations. Delayed histone hyperacetylation and gene expression changes were also observed in cell culture, and histone acetylation was observed in vivo beyond disappearance of drug from plasma. In vivo studies further demonstrated that continuous target inhibition was well tolerated and efficacious in tumor-bearing mice, leading to tumor growth inhibition with either once-daily or intermittent administration.

Potent benzoazepinone γ-secretase modulators with improved bioavailability.

The triazolyl amide γ-secretase modulators are potent alternatives to the cinnamyl amides that have entered the clinic for the treatment of Alzheimers disease. Herein we build on the lead benzoazepinones described in our prior communication with imidazomethoxyarene moiety alternatives that offer opportunities to fine tune physical properties as well as address hERG binding and PK. Both half-life and bioavailability were significantly improved, especially in dog, with robust brain Aβ42 lowering maintained in both transgenic mouse and rat.

Discovery of novel triazolobenzazepinones as γ-secretase modulators with central Aβ42 lowering in rodents and rhesus monkeys.

Synthesis and SAR studies of novel triazolobenzazepinones as gamma secretase modulators (GSMs) are presented in this communication. Starting from our azepinone leads, optimization studies toward improving central lowering of Aβ42 led to the discovery of novel benzo-fused azepinones. Several benzazepinones were profiled in vivo and found to lower brain Aβ42 levels in Sprague Dawley rats and transgenic APP-YAC mice in a dose-dependent manner after a single oral dose. Compound 34 was further progressed into a pilot study in our cisterna-magna-ported rhesus monkey model, where we observed robust lowering of CSF Aβ42 levels.