Inhibition of IRF5 cellular activity with cell-penetrating peptides that target homodimerization.

The transcription factor interferon regulatory factor 5 (IRF5) plays essential roles in pathogen-induced immunity downstream of Toll-, nucleotide-binding oligomerization domain-, and retinoic acid-inducible gene I-like receptors and is an autoimmune susceptibility gene. Normally, inactive in the cytoplasm, upon stimulation, IRF5 undergoes posttranslational modification(s), homodimerization, and nuclear translocation, where dimers mediate proinflammatory gene transcription. Here, we report the rational design of cell-penetrating peptides (CPPs) that disrupt IRF5 homodimerization. Biochemical and imaging analysis shows that IRF5-CPPs are cell permeable, noncytotoxic, and directly bind to endogenous IRF5. IRF5-CPPs were selective and afforded cell type- and species-specific inhibition. In plasmacytoid dendritic cells, inhibition of IRF5-mediated interferon-α production corresponded to a dose-dependent reduction in nuclear phosphorylated IRF5 [p(Ser462)IRF5], with no effect on pIRF5 levels. These data support that IRF5-CPPs function downstream of phosphorylation. Together, data support the utility of IRF5-CPPs as novel tools to probe IRF5 activation and function in disease.

Fragment-Based Drug Design of Novel Pyranopyridones as Cell Active and Orally Bioavailable Tankyrase Inhibitors.

Tankyrase activity has been linked to the regulation of intracellular axin levels, which have been shown to be crucial for the Wnt pathway. Deregulated Wnt signaling is important for the genesis of many diseases including cancer. We describe herein the discovery and development of a new series of tankyrase inhibitors. These pyranopyridones are highly active in various cell-based assays. A fragment/structure based optimization strategy led to a compound with good pharmacokinetic properties that is suitable for in vivo studies and further development.

Oxazole- and imidazole-based Ser-Leu dipeptide mimetics in potent inhibitors of antigen presentation by MHC class II DR molecules.

Imidazole and oxazole derivatives 1 to 4 were designed and prepared as dipeptide mimetics to replace the Ser-Leu dipeptide sequence of Ro-25-9980 (Ac-(Cha)-RAMA-S-L-NH2), a peptidic inhibitor of antigen binding to major histocompatibility complex (MHC) class II DR molecules linked to rheumatoid arthritis (RA). The most potent analog in binding assays (IC50 = 30 nM in DRB1*0401 binding; 1.6 times as potent as Ro 25-9980) was 16, Ac-(Cha)RAMA-(S)S-psi(oxazole)-L-NH2. The SAR of peptide hybrids 10 to 24, prepared by incorporating the dipeptide mimetics 1 to 4 is discussed. Of these hybrids, 23 and 24, analogs that incorporated the imidazole and oxazole mimetics as well as optimized variants at positions 3 to 5, were found to have 70 to 80 nM binding affinity comparable to the parent peptide in DRB 1*0401 binding and were also active in DRB1*0101 binding, while being resistant to proteolysis by cathepsin B. Both of these compounds showed inhibitory activity in an antigen-stimulated T-cell proliferation assay, indicating their potential to suppress autoimmune responses and as leads for therapeutic agents to treat RA.