Design, synthesis and evaluation of (R)-3-(7-(methyl(7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino)-5-azaspiro[2.4]heptan-5-yl)-3-oxopropanenitrile as a JAK1-selective inhibitor

Revisiting Structure-activity Relationships: Unleashing the potential of selective Janus kinase 1 inhibitors

Janus kinases (JAKs), a kind of non-receptor tyrosine kinases, the function has been implicated in the regulation of cell proliferation, differentiation and apoptosis, immune, inflammatory response and malignancies. Among them, JAK1 represents an essential target for modulating cytokines involved in inflammation and immune function. Rheumatoid arthritis, atopic dermatitis, ulcerative colitis and psoriatic arthritis are areas where approved JAK1 drugs have been applied for the treatment. In the review, we provided a brief introduction to JAK1 inhibitors in market and clinical trials. The structures of high active JAK1 compounds (IC50 ≤ 0.1 nM) were highlighted, with primary focus on structure-activity relationship and selectivity. Moreover, the druggability processes of approved drugs and high active compounds were analyzed. In addition, the issues involved in JAK1 compounds clinical application as well as strategies to surmount these challenges, were discussed.

Validated DBS method for filgotinib quantitation in rat dried blood spots and its application to a pharmacokinetic study in rats

Filgotinib is a selective JAK1 (Janus kinase) inhibitor, showed efficacy in patients suffering from moderate-to-severe rheumatoid arthritis. In this paper, we present the data on the development and validation of a sensitive, selective and high-throughput LC-MS/MS (liquid chromatography with tandem mass spectrometry) method for the quantitation of filgotinib from rat dried blood spot (DBS) cards. To the DBS disc cards, 0.2% formic acid enriched with internal standard (IS) was added and sonicated. Thereafter the extraction of filgotinib and the IS (tofacitinib) was accomplished using ethyl acetate as an extraction solvent. The resolution of filgotinib and the IS was achieved on a Gemini C₁₈ column with an isocratic mobile phase, which is a mixture of 0.2% formic acid:acetonitrile (20:80, v/v) at a flow-rate of 0.9 mL/min. The total run time was 2.90 min and the retention time of filgotinib and the IS was ~1.31 and 0.89 min, respectively. Filgotinib and the IS were analyzed using positive ion scan mode and parent-daughter mass to charge ion (m/z) transition of 426.3→291.3 and m/z 313.2→149.2, respectively, for quantitation. The calibration range was 1.37-1937 ng/mL. No matrix effect and carry over were observed. All the validation parameters met the acceptance criteria. The validated method has been applied to a pharmacokinetic study in rats. A good correlation between DBS and plasma concentrations for filgotinib was observed.

Molecular modeling studies of pyrrolo[2,3-d]pyrimidin-4-amine derivatives as JAK1 inhibitors based on 3D-QSAR, molecular docking, molecular dynamics (MD) and MM-PBSA calculations

Rheumatoid Arthritis (RA) is an autoimmune disease caused by overproduction of pro-inflammatory cytokines. Janus Kinases (JAKs) mediate cytokines signaling through the Janus Kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathways. Clinical studies have shown that Janus kinase 1 (JAK1) mediated signaling plays a key role in synovial response in rheumatoid arthritis. Hence, the inhibition JAK1 is considered as an important therapeutic route for treatment of rheumatoid arthritis. In this study, we have performed three-dimensional quantitative structure-activity relationship (3 D-QSAR), molecular docking, molecular dynamics (MD) and free energy calculations on a series of pyrrolo[2,3-d]pyrimidin-4-amine JAK1 inhibitors. Molecular docking studies of the compounds 03, 13, 36 and 49 with JAK1 were performed to study the binding interactions. The binding conformations of the compounds from docking studies were selected based on binding energy and H-bond interactions and were used as initial structure for MD simulations. Using 3 D-QSAR techniques, a ligand-based comparative molecular field analysis (CoMFA) model (q² = 0.5, r² = 0.96) and a receptor-based CoMFA model (q² = 0.78, r² = 0.98) were developed. Analysis of the MD results of the most active compound (compound 49) with JAK1 showed the formation of H-bond interactions with residues Glu957, Leu959 and Gly887 and water-mediated H-bond interaction with Gly887 and His885. Based on the contour map analyses of the receptor-based CoMFA, a design strategy was proposed and was used for designing new JAK1 inhibitors. Four of the designed compounds (D57, D58, D98 and D99) showed predicted activity values (pIC₅₀> 8.8) greater than the most active compound for JAK1. MM-PBSA based free energy calculations indicated that the designed compounds were able to form stable binding with JAK1 primarily through electrostatic interactions and van der Waal interactions. Collectively, the outcome of this study can be used to further the progress of JAK1 inhibition for the treatment of rheumatoid arthritis. Communicated by Ramaswamy H. Sarma.