Results from a Phase 1b/2 Study of Ibrutinib Combination Therapy in Advanced Urothelial Carcinoma.

Ibrutinib is a first-in-class Bruton's tyrosine kinase inhibitor approved for the treatment of various B-cell malignancies and chronic graft-versus-host disease. We evaluated the safety and efficacy of ibrutinib, alone or combined with standard-of-care regimens, in adults with advanced urothelial carcinoma (UC). Once-daily ibrutinib was administered orally at 840 mg (single-agent or with paclitaxel) or at 560 mg (with pembrolizumab). Phase 1b determined the recommended phase 2 dose (RP2D) of ibrutinib, and phase 2 assessed progression-free survival (PFS), overall response rate (ORR), and safety. Thirty-five, eighteen, and fifty-nine patients received ibrutinib, ibrutinib plus pembrolizumab, and ibrutinib plus paclitaxel at the RP2D, respectively. Safety profiles were consistent with those of the individual agents. The best-confirmed ORRs were 7% (two partial responses) with single-agent ibrutinib and 36% (five partial responses) with ibrutinib plus pembrolizumab. Median PFS was 4.1 months (range, 1.0-37.4+) with ibrutinib plus paclitaxel. The best-confirmed ORR was 26% (two complete responses). In previously treated patients with UC, ORR was higher with ibrutinib plus pembrolizumab than with either agent alone (historical data in the intent-to-treat population). ORR with ibrutinib plus paclitaxel was greater than historical values for single-agent paclitaxel or ibrutinib. These data warrant further evaluation of ibrutinib combinations in UC.

Discovery of (R)-(3-fluoropyrrolidin-1-yl)(6-((5-(trifluoromethyl)pyridin-2-yl)oxy)quinolin-2-yl)methanone (ABBV-318) and analogs as small molecule Nav1.7/ Nav1.8 blockers for the treatment of pain.

The voltage-gated sodium channel Nav1.7 is an attractive target for the treatment of pain based on the high level of target validation with genetic evidence linking Nav1.7 to pain in humans. Our effort to identify selective, CNS-penetrant Nav1.7 blockers with oral activity, improved selectivity, good drug-like properties, and safety led to the discovery of 2-substituted quinolines and quinolones as potent small molecule Nav1.7 blockers. The design of these molecules focused on maintaining potency at Nav1.7, improving selectivity over the hERG channel, and overcoming phospholipidosis observed with the initial leads. The structure-activity relationship (SAR) studies leading to the discovery of (R)-(3-fluoropyrrolidin-1-yl)(6-((5-(trifluoromethyl)pyridin-2-yl)oxy)quinolin-2-yl)methanone (ABBV-318) are described herein. ABBV-318 displayed robust in vivo efficacy in both inflammatory and neuropathic rodent models of pain. ABBV-318 also inhibited Nav1.8, another sodium channel isoform that is an active target for the development of new pain treatments.

Beyond Traditional Structure-Based Drug Design: The Role of Iron Complexation, Strain, and Water in the Binding of Inhibitors for Hypoxia-Inducible Factor Prolyl Hydroxylase 2.

A combination of structure-based drug design and medicinal chemistry efforts led us from benzimidazole-2-carboxamide with modestly active hypoxia-inducible factor prolyl hydroxylase 2 inhibition to certain benzimidazole-2-pyrazole carboxylic acids that were more potent as well as orally efficacious stimulators of erythropoietin secretion in our in vivo mouse model. To better understand the structure-activity relationship, it was necessary to account for (i) the complexation of the ligand with the active site Fe2+, (ii) the strain incurred by the ligand upon binding, and (iii) certain key water interactions identified by a crystal structure analysis. With this more complete computational model, we arrived at an overarching paradigm that accounted for the potency differences between benzimidazole-2-carboxamide and benzimidazole-2-pyrazole carboxylic acid enzyme inhibitors. Moreover, the computational paradigm allowed us to anticipate that the bioisostere replacement strategy (amide → pyrazole), which had shown success in the benzimidazole series, was not generally applicable to other series. This illustrates that to fully reconcile the important ligand-active site interactions for certain targets, one often needs to move beyond traditional structure-based drug design (such as crystallographic analysis, docking, etc.) and appeal to a higher level of computational theory.

Emerging technologies for metabolite generation and structural diversification.

Multiple technologies have emerged for structural diversification and efficient production of metabolites of drug molecules. These include expanded use of enzymatic and bioorganic transformations that mimic biological systems, biomimetic catalysis and electrochemical techniques. As this field continues to mature the breadth of transformations is growing beyond simple oxidative processes due in part to parallel development of more efficient catalytic methods for functionalization of unactivated scaffolds. These technologies allow for efficient structural diversification of both aromatic and aliphatic substrates in many cases via single step reactions without the use of protecting groups.

Pharmacological characterization of 1-(5-chloro-6-(trifluoromethoxy)-1H-benzoimidazol-2-yl)-1H-pyrazole-4-carboxylic acid (JNJ-42041935), a potent and selective hypoxia-inducible factor prolyl hydroxylase inhibitor.

The hypoxia-inducible factor (HIF) prolyl hydroxylase (PHD) enzymes represent novel targets for the treatment of anemia, ulcerative colitis, and ischemic and metabolic disease inter alia. We have identified a novel small-molecule inhibitor of PHD, 1-(5-chloro-6-(trifluoromethoxy)-1H-benzoimidazol-2-yl)-1H-pyrazole-4-carboxylic acid (JNJ-42041935), through structure-based drug design methods. The pharmacology of JNJ-42041935 was investigated in enzyme, cellular, and whole-animal systems and was compared with other compounds described in the literature as PHD inhibitors. JNJ-42041935, was a potent (pK(I) = 7.3-7.9), 2-oxoglutarate competitive, reversible, and selective inhibitor of PHD enzymes. In addition, JNJ-42041935 was used to compare the effect of selective inhibition of PHD to intermittent, high doses (50 µg/kg i.p.) of an exogenous erythropoietin receptor agonist in an inflammation-induced anemia model in rats. JNJ-42041935 (100 µmol/kg, once a day for 14 days) was effective in reversing inflammation-induced anemia, whereas erythropoietin had no effect. The results demonstrate that JNJ-42041935 is a new pharmacological tool, which can be used to investigate PHD inhibition and demonstrate that PHD inhibitors offer great promise for the treatment of inflammation-induced anemia.

Benzimidazole-2-pyrazole HIF Prolyl 4-Hydroxylase Inhibitors as Oral Erythropoietin Secretagogues.

HIF prolyl 4-hydroxylases (PHD) are a family of enzymes that mediate key physiological responses to hypoxia by modulating the levels of hypoxia inducible factor 1-α (HIF1α). Certain benzimidazole-2-pyrazole carboxylates were discovered to be PHD2 inhibitors using ligand- and structure-based methods and found to be potent, orally efficacious stimulators of erythropoietin secretion in vivo.

Expedient synthesis of N-methyl tubulysin analogues with high cytotoxicity.

An optimized and highly efficient synthesis of potent, bioactive N-methyl tubulysin analogues 2 and 4 has been achieved with > 40% overall yields. This synthesis represents a significant improvement over previously reported syntheses of these and related tubulysin analogues. The stereoselective synthesis of the unnatural amino acid tubuvaline is accomplished using tert-butanesulfinamide chemistry. N-Alkylation to form N-methyl tubuvaline is performed without protection of the tubuvaline alcohol by implementing a unique N-methylation strategy via formation and reduction of a 1,3-tetrahydrooxazine heterocycle. Acylation of the hindered N-methyl tubuvaline amine utilizes a novel sequence of O-acylation followed by an O- to N-acyl transfer to form the hindered amide bond between N-methyl tubuvaline and isoleucine. This high-yielding synthesis should enable the production of large quantities of material for biological studies.

Design, synthesis, and biological properties of highly potent tubulysin D analogues.

Ten analogues of tubulysin D were synthesized and assayed against established mammalian cell lines, including cancer cells measuring inhibition of cell growth by an MTT assay. These experiments establish for the first time the essential features for the potent cytotoxicity of tubulysin D. The activities of analogues 2 to 5 demonstrate that numerous modifications may be introduced at the C-terminus of the natural product with only modest loss in activity, while the activities of analogues 6 to 8 suggest that a basic amine must be present at the N-terminus to maintain activity. Most surprisingly, analogue 10 establishes that replacement of the chemically labile O-acyl N,O-acetal with the stable N-methyl group results in almost no loss in activity. In aggregate, these structure-activity relationships enable the design of analogues such as 11 that are smaller and considerably more stable than tubulysin D but that maintain most of its potent cell-growth inhibitory activity.

One-pot asymmetric synthesis of either diastereomer of tert-butanesulfinyl-protected amines from ketones.

A one-pot method for the asymmetric synthesis of tert-butanesulfinyl-protected amines is described. Condensation of aryl alkyl and dialkyl ketones with tert-butanesulfinamide followed by in situ reduction with the appropriate reagent provides either diastereomer of the sulfinamide products in good yields and with diastereomeric ratios of up to 99:1.

The total synthesis of tubulysin D.

The first total synthesis of tubulysin D is reported. The development and application of new tert-butanesulfinamide methods allowed for rapid syntheses of the tubuvaline and tubuphenylalanine fragments. Most significantly, a route was devised and implemented to introduce and carry forward the highly labile N,O-acetal functionality. Tubulysin D is the most active member of the tubulysin family, and the efficient synthetic route described herein will allow for the rapid syntheses of analogues to probe the biological activity of this important class of natural products.

N-sulfinyl metalloenamine conjugate additions: asymmetric synthesis of piperidines.

[reaction: see text] The first examples of conjugate additions of N-tert-butanesulfinyl metalloenamines are reported. Highly stereoselective conjugate additions (97:3 to 99:1 dr) were observed between metalloenamines derived from N-sulfinyl ketimines and alpha,beta-unsaturated ketones bearing either alkyl or aryl substituents. The conjugate addition products could rapidly be converted with high diastereoselectivity to 2,4,6-trisubstituted piperidines, which are difficult to access by other methods.

Catalytic enantioselective sulfinyl transfer using cinchona alkaloid catalysts.

[reaction: see text] Practical reaction conditions for the catalytic enantioselective synthesis of sulfinate esters are reported. Commercially available cinchona alkaloids were found to be superior catalysts for the sulfinyl transfer reaction of tert-butanesulfinyl chloride and a variety of benzyl alcohols. Sulfinyl transfer with 2,4,6-trichlorobenzyl alcohol and 10 mol % of the commercially available, inexpensive catalyst quinidine provided the pure sulfinate ester product in 92% isolated yield and with 90% ee.