Mouse IL-2/CD25 Fusion Protein Induces Regulatory T Cell Expansion and Immune Suppression in Preclinical Models of Systemic Lupus Erythematosus.

Systemic lupus erythematosus (SLE) is associated with an IL-2-deficient state, with regulatory T cells (Tregs) showing diminished immune regulatory capacity. A low dose of IL-2 has shown encouraging clinical benefits in SLE patients; however, its clinical utility is limited because of the requirement of daily injections and the observation of increase in proinflammatory cytokines and in non-Tregs. We recently showed that a fusion protein of mouse IL-2 and mouse IL-2Rα (CD25), joined by a noncleavable linker, was effective in treating diabetes in NOD mice by selectively inducing Treg expansion. In this report, we show that mouse IL-2 (mIL-2)/CD25 at doses up to 0.5 mg/kg twice a week induced a robust Treg expansion without showing signs of increase in the numbers of NK, CD4+Foxp3-, or CD8+ T cells or significant increase in proinflammatory cytokines. In both NZB × NZW and MRL/lpr mice, mIL-2/CD25 at 0.2-0.4 mg/kg twice a week demonstrated efficacy in inducing Treg expansion, CD25 upregulation, and inhibiting lupus nephritis based on the levels of proteinuria, autoantibody titers, and kidney histology scores. mIL-2/CD25 was effective even when treatment was initiated at the time when NZB × NZW mice already showed signs of advanced disease. Furthermore, we show coadministration of prednisolone, which SLE patients commonly take, did not interfere with the ability of mIL-2/CD25 to expand Tregs. The prednisolone and mIL-2/CD25 combination treatment results in improvements in most of the efficacy readouts relative to either monotherapy alone. Taken together, our results support further evaluation of IL-2/CD25 in the clinic for treating immune-mediated diseases such as SLE.

Autoimmune pathways in mice and humans are blocked by pharmacological stabilization of the TYK2 pseudokinase domain.

TYK2 is a nonreceptor tyrosine kinase involved in adaptive and innate immune responses. A deactivating coding variant has previously been shown to prevent receptor-stimulated activation of this kinase and provides high protection from several common autoimmune diseases but without immunodeficiency. An agent that recapitulates the phenotype of this deactivating coding variant may therefore represent an important advancement in the treatment of autoimmunity. BMS-986165 is a potent oral agent that similarly blocks receptor-stimulated activation of TYK2 allosterically and with high selectivity and potency afforded through optimized binding to a regulatory domain of the protein. Signaling and functional responses in human TH17, TH1, B cells, and myeloid cells integral to autoimmunity were blocked by BMS-986165, both in vitro and in vivo in a phase 1 clinical trial. BMS-986165 demonstrated robust efficacy, consistent with blockade of multiple autoimmune pathways, in murine models of lupus nephritis and inflammatory bowel disease, supporting its therapeutic potential for multiple immune-mediated diseases.

Engineering of a novel anti-CD40L domain antibody for treatment of autoimmune diseases.

CD40-CD40L interactions play a critical role in regulating immune responses. Blockade of CD40L by Abs, such as the anti-CD40L Ab 5c8, demonstrated positive clinical effects in patients with autoimmune diseases; however, incidents of thromboembolism (TE) precluded further development of these molecules. In this study, we examined the role of the Fc domain interaction with FcγRs in modulating platelet activation and potential for TE. Our results show that the interaction of the 5c8 wild-type IgG1 Fc domain with FcγRs is responsible for platelet activation, as measured by induction of PAC-1 and CD62P. A version of 5c8 with a mutated IgG1 tail was identified that showed minimal FcγR binding and platelet activation while maintaining full binding to CD40L. To address whether Fc effector function is required for immunosuppression, a potent Ab fragment, termed a "domain Ab" (dAb), against murine CD40L was identified and fused to a murine IgG1 Fc domain containing a D265A mutation that lacks Fc effector function. In vitro, this dAb-Fc demonstrated comparable potency to the benchmark mAb MR-1 in inhibiting B cell and dendritic cell activation. Furthermore, the anti-CD40L dAb-Fc exhibited a notable efficacy comparable to MR-1 in various preclinical models, such as keyhole limpet hemocyanin-induced Ab responses, alloantigen-induced T cell proliferation, "heart-to-ear" transplantation, and NZB × NZW F1 spontaneous lupus. Thus, our data show that immunosuppression and TE can be uncoupled and that a CD40L dAb with an inert Fc tail is expected to be efficacious for treating autoimmune diseases, with reduced risk for TE.

Insulin receptor (IR) pathway hyperactivity in IGF-IR null cells and suppression of downstream growth signaling using the dual IGF-IR/IR inhibitor, BMS-754807.

The biology of IGF-IR/IR signaling was studied in normal mouse embryonic fibroblasts (MEFs) that were either wild type (wt), heterozygous (het), or null for the IGF-IR. The ability of IGF-I, IGF-II, or insulin to stimulate serum-starved MEFs was characterized by gene expression profiling and biochemical analyses for activation of downstream signals. Each genotypic group of MEFs exhibited distinct patterns of expression both while resting and in response to stimulation. The insulin receptor (IR) pathway in IGF-IR null MEFs was hypersensitive to insulin ligand stimulation resulting in greater AKT phosphorylation than in wt or het MEFs stimulated with the same ligand. Interestingly, the IR pathway hypersensitivity in IGF-IR null MEFs occurred with no observed changes in the levels of IR isoforms A or B. A new small molecule IGF-IR inhibitor (BMS-754807), having equipotent activity against both IGF-IR and IR, proved effective in suppressing both AKT and ERK phosphorylation from both the IGF-IR and IR pathways by all three ligands tested in wt, het, and null MEFs. The use of a dual IGF-IR/IR inhibitor addresses concerns about the use of growth inhibiting therapies directed against the IGF-IR receptor in certain cancers. Lastly, comparison of the antiproliferative effects (IC(50)s) of various compounds in wt vs. null MEFs demonstrates that genetically characterized MEFs provide a simple and inexpensive tool with which to define compounds as having mostly on-target or off-target IGF-IR activities because off-target compounds affect both wt and null MEFs equally.

A highly selective inhibitor of I kappa B kinase, BMS-345541, blocks both joint inflammation and destruction in collagen-induced arthritis in mice.

OBJECTIVE: The transcription of several cytokines, cell adhesion molecules, and enzymes involved in the inflammatory and destructive mechanisms of rheumatoid arthritis is dependent on nuclear factor kappa B (NF-kappa B). Because I kappa B kinase (IKK) is critical in transducing the signal-inducible activation of NF-kappa B, we examined whether the highly selective and orally bioavailable IKK inhibitor BMS-345541 is efficacious against collagen-induced arthritis (CIA) in mice. METHODS: Arthritis in DBA/1LacJ male mice was induced by subcutaneous immunization with bovine type II collagen on day 0 and day 21. BMS-345541 was administered perorally daily, either prophylactically (before disease onset) or therapeutically (after disease onset). Clinical assessment of the incidence and severity of disease was conducted throughout the study, and histologic evaluation was performed at the time of study termination (day 42). RESULTS: When administered prophylactically, BMS-345541 (in a dose range of 10-100 mg/kg) was effective, in a dose-dependent manner, in reducing the incidence of disease and inhibiting clinical signs of disease. Histologic evaluation of the joints showed that both inflammation and joint destruction were blocked by the IKK inhibitor. Message levels of interleukin-1 beta in the joints were also dose-dependently inhibited in the mice that received BMS-345541. Dose-dependent efficacy in terms of both disease severity and histologic end points was observed with the therapeutic dosing regimen of BMS-345541, with use of the 100-mg/kg dose resulting in resolution of disease. CONCLUSION: IKK plays a key role in CIA in mice, and inhibitors of this enzyme represent a promising target for the development of novel agents to treat rheumatoid arthritis and other inflammatory diseases. BMS-345541 represents the first example of an inhibitor of IKK that has antiinflammatory activity in vivo.