Evaluation of JAK3 Biology in Autoimmune Disease Using a Highly Selective, Irreversible JAK3 Inhibitor.

Reversible janus associated kinase (JAK) inhibitors such as tofacitinib and decernotinib block cytokine signaling and are efficacious in treating autoimmune diseases. However, therapeutic doses are limited due to inhibition of other JAK/signal transducer and activator of transcription pathways associated with hematopoiesis, lipid biogenesis, infection, and immune responses. A selective JAK3 inhibitor may have a better therapeutic index; however, until recently, no compounds have been described that maintain JAK3 selectivity in cells, as well as against the kinome, with good physicochemical properties to test the JAK3 hypothesis in vivo. To quantify the biochemical basis for JAK isozyme selectivity, we determined that the apparent Km value for each JAK isozyme ranged from 31.8 to 2.9 µM for JAK1 and JAK3, respectively. To confirm compound activity in cells, we developed a novel enzyme complementation assay that read activity of single JAK isozymes in a cellular context. Reversible JAK3 inhibitors cannot achieve sufficient selectivity against other isozymes in the cellular context due to inherent differences in enzyme ATP Km values. Therefore, we developed irreversible JAK3 compounds that are potent and highly selective in vitro in cells and against the kinome. Compound 2, a potent inhibitor of JAK3 (0.15 nM) was 4300-fold selective for JAK3 over JAK1 in enzyme assays, 67-fold [interleukin (IL)-2 versus IL-6] or 140-fold [IL-2 versus erythropoietin or granulocyte-macrophage colony-stimulating factor (GMCSF)] selective in cellular reporter assays and >35-fold selective in human peripheral blood mononuclear cell assays (IL-7 versus IL-6 or GMCSF). In vivo, selective JAK3 inhibition was sufficient to block the development of inflammation in a rat model of rheumatoid arthritis, while sparing hematopoiesis.

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.

Exploring the pharmacokinetic properties of phosphorus-containing selective HDAC 1 and 2 inhibitors (SHI-1:2).

We report the preparation and structure-activity relationships of phosphorus-containing histone deacetylase inhibitors. A strong trend between decreasing phosphorus functional group size and superior mouse pharmacokinetic properties was identified. In addition, optimized candidates showed tumor growth inhibition in xenograft studies.

A divergent approach to the synthesis of 3-substituted-2-pyrazolines: Suzuki cross-coupling of 3-sulfonyloxy-2-pyrazolines.

The efficient Suzuki cross-coupling of pyrazoline nonaflates with organoboron reagents was achieved to afford diverse 3-substituted-2-pyrazolines in excellent yield. The nonaflates displayed improved reactivity over the corresponding triflates and smoothly coupled to a variety of aryl- and heteroarylboronic acids. This process and its broad scope constitute a rapid, divergent strategy for the synthesis of elaborated 2-pyrazolines that are not readily obtained via conventional methods.

Phenylglycine and phenylalanine derivatives as potent and selective HDAC1 inhibitors (SHI-1).

An HTS screening campaign identified a series of low molecular weight phenols that showed excellent selectivity (>100-fold) for HDAC1/HDAC2 over other Class I and Class II HDACs. Evolution and optimization of this HTS hit series provided HDAC1-selective (SHI-1) compounds with excellent anti-proliferative activity and improved physical properties. Dose-dependent efficacy in a mouse HCT116 xenograft model was demonstrated with a phenylglycine SHI-1 analog.

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.

Optimization of biaryl Selective HDAC1&2 Inhibitors (SHI-1:2).

A class of biaryl benzamides was identified and optimized as selective HDAC1&2 inhibitors (SHI-1:2). These agents exhibit selectivity over class II HDACs 4-7, as well as class I HDACs 3 and 8; providing examples of selective HDAC inhibitors for the HDAC isoforms most closely associated with cancer. The hypothesis for the increased selectivity is the binding of a pendant aromatic group in the internal cavity of the HDAC1&2 enzymes. SAR development based on an initial lead led to a series of potent and selective inhibitors with reduced off-target activity and tumor growth inhibition activity in a HCT-116 xenograft model.

A new strategy for the synthesis of benzylic sulfonamides: palladium-catalyzed arylation and sulfonamide metathesis.

An efficient two-step strategy has been developed to access diversely functionalized benzylic sulfonamides. Execution of this strategy required the development of two reaction methods: the palladium-catalyzed cross-coupling of aryl halides with CH-acidic methanesulfonamides and a metathesis reaction between the resulting alpha-arylated sulfonamides and diverse amines. The broad scope of the cross-coupling process combined with a versatile sulfonamide metathesis constitutes an efficient strategy for the synthesis of various benzylic sulfonamides.

Benzo[b]thiophene-based histone deacetylase inhibitors.

Benzo[b]thienyl hydroxamic acids, a novel class of histone deacetylase (HDAC) inhibitors, were identified via a targeted screen of small molecule hydroxamic acids. Various substitutions were explored in the C5- and C6-positions of the benzo[b]thiophene core to characterize SAR and develop optimal inhibitors. It was determined that substitution at the C6-position of the benzo[b]thiophene core with a three-atom spacer yielded optimal HDAC1 inhibition and anti-proliferative activity in murine erythroleukemia (SC-9) cells.

Design of novel histone deacetylase inhibitors.

Histone deacetylase (HDAC) inhibitors that target Class I and Class II HDACs are of synthetic and therapeutic interest and ongoing clinical studies indicate that they show great promise for the treatment of cancer. Moreover, Zolinza (vorinostat) was recently approved by the FDA for the treatment of the cutaneous manifestations of cutaneous T-cell lymphoma [Nat. Rev. Drug Disc. 2007, 6, 21]. As part of a broader effort to more fully explore the structure-activity relationships (SAR) of HDAC inhibitors, we sought to identify novel HDAC inhibitor structures through iterative design by utilizing low affinity ligands as synthetic starting points for SAR development. Novel and potent HDAC inhibitors have been identified using this approach and herein we report the optimization of the recognition elements of a novel series of malonyl-derived HDAC inhibitors.

Aminosuberoyl hydroxamic acids (ASHAs): a potent new class of HDAC inhibitors.

Histone deacetylase (HDAC) inhibitors that target Class I and Class II HDACs are currently in advanced clinical trials for the treatment of cancer. Vorinostat (Zolinza, SAHA) is a hydroxamic acid approved for the treatment of patients with cutaneous T-cell lymphoma who have progressive, persistent or recurrent disease on or following two systemic therapies. As part of an on-going effort to better understand the nature of the HDAC enzyme/inhibitor interaction and design highly effective HDAC inhibitors, we herein report the design, synthesis and HDAC inhibitory activity of a vorinostat-derived series of substrate-based HDAC inhibitors.

Putative Diels-Alder-Catalyzed Cyclization during the Biosynthesis of Lovastatin.

A Diels-Alder cyclization proposed to occur during polyketide synthase assembly of the bicyclic core of lovastatin (1) (mevinolin) by Aspergillus terreus MF 4845 was examined via the synthesis of the N-acetylcysteamine (NAC) thioester of [2,11-(13)C(2)]-(E,E,E)-(R)-6-methyldodecatri-2,8,10-enoate (5a). In vitro Diels-Alder cyclization of the corresponding unlabeled NAC ester 5b, ethyl ester 18b, and acid 20b yielded two analogous diastereomers in each case, under either thermal or Lewis acid-catalyzed conditions. The reaction of thioester 5 proceeds readily at 22 degrees C in aqueous media. For 18b, one product is trans-fused ethyl (1R,2R,4aS, 6R,8aR)-1,2,4a,5,6,7,8,8a-octahydro-2,6-dimethylnaphthalene-1-carboxylate (30) (endo product), and the other is cis-fused ethyl (1R,2S,4aR,6R,8aR)-1,2,4a,5,6,7,8,8a-octahydro-2,6-dimethylnaphthalene-1-carboxylate (31) (exo product). Isomer 21 with stereochemistry analogous to 4a,5-dihydromonacolin L (2), a precursor of 1, was made by transformation of a tricyclic lactone, (1S,2S,4aR,6S,8S,8aS)-1-(ethoxycarbonyl)-1,2,4a,5,6,7,8,8a-octahydro-2-methyl-6,8-naphthalenecarbolactone (22) using reduction and Barton deoxygenation. Comparison of 21 with 30 and 31 confirmed the structural assignments and showed that the nonenzymatic 4 + 2 cyclizations of 5, 18, and 20 proceed via chairlike exo and endo transition states with the methyl substituent pseudoequatorial. The proposed biosynthetic Diels-Alder leading to lovastatin (1) would require an endo conformation with the methyl substituent pseudoaxial. Intact incorporation of the labeled hexaketide triene 5a into 1 was not achieved because of rapid degradation by A. terreus cells.