Design and optimization of a series of 4-(3-azabicyclo[3.1.0]hexan-3-yl)pyrimidin-2-amines: Dual inhibitors of TYK2 and JAK1.

Herein, we disclose a new series of TYK2/ JAK1 inhibitors based upon a 3.1.0 azabicyclic substituted pyrimidine scaffold. We illustrate the use of structure-based drug design for the initial design and subsequent optimization of this series of compounds. One advanced example 19 met program objectives for potency, selectivity and ADME, and demonstrated oral activity in the adjuvant-induced arthritis rat model.

Dual Inhibition of TYK2 and JAK1 for the Treatment of Autoimmune Diseases: Discovery of (( S)-2,2-Difluorocyclopropyl)((1 R,5 S)-3-(2-((1-methyl-1 H-pyrazol-4-yl)amino)pyrimidin-4-yl)-3,8-diazabicyclo[3.2.1]octan-8-yl)methanone (PF-06700841).

Cytokine signaling is an important characteristic of autoimmune diseases. Many pro-inflammatory cytokines signal through the Janus kinase (JAK)/Signal transducer and activator of transcription (STAT) pathway. JAK1 is important for the γ-common chain cytokines, interleukin (IL)-6, and type-I interferon (IFN) family, while TYK2 in addition to type-I IFN signaling also plays a role in IL-23 and IL-12 signaling. Intervention with monoclonal antibodies (mAbs) or JAK1 inhibitors has demonstrated efficacy in Phase III psoriasis, psoriatic arthritis, inflammatory bowel disease, and rheumatoid arthritis studies, leading to multiple drug approvals. We hypothesized that a dual JAK1/TYK2 inhibitor will provide additional efficacy, while managing risk by optimizing selectivity against JAK2 driven hematopoietic changes. Our program began with a conformationally constrained piperazinyl-pyrimidine Type 1 ATP site inhibitor, subsequent work led to the discovery of PF-06700841 (compound 23), which is in Phase II clinical development (NCT02969018, NCT02958865, NCT03395184, and NCT02974868).

Selectively targeting an inactive conformation of interleukin-2-inducible T-cell kinase by allosteric inhibitors.

ITK (interleukin-2-inducible T-cell kinase) is a critical component of signal transduction in T-cells and has a well-validated role in their proliferation, cytokine release and chemotaxis. ITK is an attractive target for the treatment of T-cell-mediated inflammatory diseases. In the present study we describe the discovery of kinase inhibitors that preferentially bind to an allosteric pocket of ITK. The novel ITK allosteric site was characterized by NMR, surface plasmon resonance, isothermal titration calorimetry, enzymology and X-ray crystallography. Initial screening hits bound to both the allosteric pocket and the ATP site. Successful lead optimization was achieved by improving the contribution of the allosteric component to the overall inhibition. NMR competition experiments demonstrated that the dual-site binders showed higher affinity for the allosteric site compared with the ATP site. Moreover, an optimized inhibitor displayed non-competitive inhibition with respect to ATP as shown by steady-state enzyme kinetics. The activity of the isolated kinase domain and auto-activation of the full-length enzyme were inhibited with similar potency. However, inhibition of the activated full-length enzyme was weaker, presumably because the allosteric site is altered when ITK becomes activated. An optimized lead showed exquisite kinome selectivity and is efficacious in human whole blood and proximal cell-based assays.

Covalent inhibitors of interleukin-2 inducible T cell kinase (itk) with nanomolar potency in a whole-blood assay.

We wish to report a strategy that targets interleukin-2 inducible T cell kinase (Itk) with covalent inhibitors. Thus far, covalent inhibition of Itk has not been disclosed in the literature. Structure-based drug design was utilized to achieve low nanomolar potency of the disclosed series even at high ATP concentrations. Kinetic measurements confirmed an irreversible binding mode with off-rate half-lives exceeding 24 h and moderate on-rates. The analogues are highly potent in a cellular IP1 assay as well as in a human whole-blood (hWB) assay. Despite a half-life of approximately 2 h in resting primary T cells, the covalent inhibition of Itk resulted in functional silencing of the TCR pathway for more than 24 h. This prolonged effect indicates that covalent inhibition is a viable strategy to target the inactivation of Itk.

Synthesis, molecular modeling and biological evaluation of aza-proline and aza-pipecolic derivatives as FKBP12 ligands and their in vivo neuroprotective effects.

Nonimmunosuppressant ligands, exemplified by GPI 1046 (1), for the peptidyl-prolyl isomerase FKBP12 have been found to unexpectedly possess powerful neuroprotective and neuroregenerative effects in vitro and in vivo. We have extensively explored the therapeutic utility of FKBP12 ligands based on analogues of proline and pipecolic acid. As part of our ongoing program to explore novel structural classes of FKBP12 ligands, we herein wish to report a new class of FKBP12 ligands containing aza-proline and aza-pipecolic acid analogues. Details of the synthetic studies, together with biological activity will be presented.

Synthesis and evaluation of chiral bicyclic proline FKBP12 ligands.

As part of our ongoing program to explore novel structural classes of FKBP12 ligands, we herein wish to report a new class of FKBP12 ligands containing chiral bicyclic proline analogues. Details of the synthetic routes, together with preliminary biological activity, will be presented.

Synthesis of N-glyoxyl prolyl and pipecolyl amides and thioesters and evaluation of their in vitro and in vivo nerve regenerative effects.

The recent discovery that small molecule ligands for the peptidyl-prolyl isomerase (PPIase) FKBP12 possess powerful neuroprotective and neuroregenerative properties in vitro and in vivo suggests therapeutic utility for such compounds in neurodegenerative disease. The neurotrophic effects of these compounds are independent of the immunosuppressive pathways by which drugs such as FK506 and rapamycin operate. Previous work by ourselves and other groups exploring the structure-activity relationships (SAR) of small molecules that mimic only the FKBP binding domain portion of FK506 has focused on esters of proline and pipecolic acid. We have explored amide and thioester analogues of these earlier structures and found that they too are extremely potent in promoting recovery of lesioned dopaminergic pathways in a mouse model of Parkinson's disease. Several compounds were shown to be highly effective upon oral administration after lesioning of the dopaminergic pathway, providing further evidence of the potential clinical utility of a variety of structural classes of FKBP12 ligands.