2-(3-{(3R,4R)-4-Methyl-3-[meth-yl(7H-pyrrolo-[2,3-d]pyrimidin-4-yl)amino]-piperidin-1-yl}oxetan-3-yl)aceto-nitrile monohydrate.

In the title compound, C18H24N6O·H2O, the piperidine ring adopts a chair conformation with an N-C-C-C torsion angle of 39.5 (5)° between the cis-related substituents. The pyrrole N-H group forms a water-mediated inter-molecular hydrogen bond to one of the N atoms of the annelated pyrimidine ring. The water mol-ecule connects two organic mol-ecules and is disorderd over two positions (occupancies of 0.48 and 0.52). The crystal packing shows zigzag chains of alternating organic and water mol-ecules running parallel to the a axis.

N-[(3RS,4SR)-1-Benzyl-4-methyl-piperi-din-3-yl]-1-(4-methylphenyl-sulfonyl)-5-nitro-1H-pyrrolo-[2,3-b]pyridin-4-amine.

The structure of the title compound, C(27)H(29)N(5)O(4)S, displays an intra-molecular N-H⋯O hydrogen bond. The pyrrolo-[2,3-b]pyridine core makes a dihedral angle of 85.5 (4)° with the benzyl residue and a dihedral angle of 89.4 (9)° with the tosyl ring. The nitro group is slightly twisted out of the plane of the planar pyrrolo-pyridine system [(-N-)C-C-N-O torsion angle = -4.61 (18)° and (-NH-)C-C-N-O = -6.46 (18)°].

N-[(3RS,4RS)-1-Benzyl-4-methyl-piperidin-3-yl]-5-nitro-1-phenyl-sulfonyl-1H-pyrrolo-[2,3-b]pyridine-4-amine.

The pyrrolo-pyridine system in the title compound, C(27)H(29)N(5)O(4)S, is oriented at a dihedral angle of 71.20 (5)° towards the phenyl ring of the tosyl residue and at a dihedral angle of 45.43 (4)° towards the benzyl group. The structure shows an intra-molecular N-H⋯O and a weak intra-molecular N-H⋯N hydrogen bond. The piperidine ring adopts a chair conformation, with the cis substituents displaying a torsion angle of -54.59 (18)°.

1-[(3RS,4RS)-1-Benzyl-4-methyl-piperi-din-3-yl]-1,6-dihydro-imidazo[4,5-d]pyrrolo-[2,3-b]pyridine hemihydrate.

The benzyl residue in the title compound, C(21)H(23)N(5)·0.5H(2)O, is oriented at a dihedral angle of 83.8 (3)° towards the 1,6-dihydro-imidazo[4,5-d]pyrrolo-[2,3-b]pyridine system. The piperidine ring adopts a chair conformation with the cis substituents displaying a torsion angle of -45.91 (16)°. In the crystal, mol-ecules are accumulated as racemic dimers by two inter-molecular hydrogen bonds between the pyrrolo-pyridine systems. Another hydrogen bond is formed between the imidazole ring and the cocrystallized water mol-ecule, which is located on a twofold rotation axis.

Selective JAK3 Inhibitors with a Covalent Reversible Binding Mode Targeting a New Induced Fit Binding Pocket.

Janus kinases (JAKs) are a family of cytoplasmatic tyrosine kinases that are attractive targets for the development of anti-inflammatory drugs given their roles in cytokine signaling. One question regarding JAKs and their inhibitors that remains under intensive debate is whether JAK inhibitors should be isoform selective. Since JAK3 functions are restricted to immune cells, an isoform-selective inhibitor for JAK3 could be especially valuable to achieve clinically more useful and precise effects. However, the high degree of structural conservation makes isoform-selective targeting a challenging task. Here, we present picomolar inhibitors with unprecedented kinome-wide selectivity for JAK3. Selectivity was achieved by concurrent covalent reversible targeting of a JAK3-specific cysteine residue and a ligand-induced binding pocket. We confirmed that in vitro activity and selectivity translate well into the cellular environment and suggest that our inhibitors are powerful tools to elucidate JAK3-specific functions.

Tofacitinib and analogs as inhibitors of the histone kinase PRK1 (PKN1).

AIM: The histone kinase PRK1 has been identified as a potential target to combat prostate cancer but selective PRK1 inhibitors are lacking. The US FDA -approved JAK1-3 inhibitor tofacitinib also potently inhibits PRK1 in vitro. RESULTS: We show that tofacitinib also inhibits PRK1 in a cellular setting. Using tofacitinib as a starting point for structure-activity relationship studies, we identified a more potent and another more selective PRK1 inhibitor compared with tofacitinib. Furthermore, we found two potential PRK1/JAK3-selectivity hotspots. CONCLUSION: The identified inhibitors and the selectivity hotspots lay the basis for the development of selective PRK1 inhibitors. The identification of PRK1, but also of other cellular tofacitinib targets, has implications on its clinical use and on future development of tofacitinib-like JAK inhibitors. [Formula: see text].

Design and synthesis of tricyclic JAK3 inhibitors with picomolar affinities as novel molecular probes.

The Janus kinase (JAK) signaling pathway is of particular importance in the pathology of inflammatory diseases and oncological disorders, and the inhibition of Janus kinase 3 (JAK3) with small molecules has proven to provide therapeutic immunosuppression. A novel class of tricyclic JAK inhibitors derived from the 3-methyl-1,6-dihydrodipyrrolo[2,3-b:2',3'-d]pyridine scaffold was designed based on the tofacitinib-JAK3 crystal structure by applying a rigidization approach. A convenient synthetic strategy to access the scaffold via an intramolecular Heck reaction was developed, and a small library of inhibitors was prepared and characterized using in vitro biochemical as well as cellular assays. IC50 values as low as 220 pM could be achieved with selectivity for JAK3 over other JAK family members. Both activity and selectivity were confirmed in a cellular STAT phosphorylation assay, providing also first-time data for tofacitinib. Our novel inhibitors may serve as tool compounds and useful probes to explore the role of JAK3 inhibition in pharmacodynamics studies.

Novel hinge-binding motifs for Janus kinase 3 inhibitors: a comprehensive structure-activity relationship study on tofacitinib bioisosteres.

The Janus kinases (JAKs) are a family of cytosolic tyrosine kinases crucially involved in cytokine signaling. JAKs have been demonstrated to be valid targets in the treatment of inflammatory and myeloproliferative disorders, and two inhibitors, tofacitinib and ruxolitinib, recently received their marketing authorization. Despite this success, selectivity within the JAK family remains a major issue. Both approved compounds share a common 7H-pyrrolo[2,3-d]pyrimidine hinge binding motif, and little is known about modifications tolerated at this heterocyclic core. In the current study, a library of tofacitinib bioisosteres was prepared and tested against JAK3. The compounds possessed the tofacitinib piperidinyl side chain, whereas the hinge binding motif was replaced by a variety of heterocycles mimicking its pharmacophore. In view of the promising expectations obtained from molecular modeling, most of the compounds proved to be poorly active. However, strategies for restoring activity within this series of novel chemotypes were discovered and crucial structure-activity relationships were deduced. The compounds presented may serve as starting point for developing novel JAK inhibitors and as a valuable training set for in silico models.