A CD25-biased interleukin-2 for autoimmune therapy engineered via a semi-synthetic organism

BACKGROUND

Natural cytokines are poorly suited as therapeutics for systemic administration due to suboptimal pharmacological and pharmacokinetic (PK) properties. Recombinant human interleukin-2 (rhIL-2) has shown promise for treatment of autoimmune (AI) disorders yet exhibits short systemic half-life and opposing immune responses that negate an appropriate therapeutic index.

METHODS

A semi-synthetic microbial technology platform was used to engineer a site-specifically pegylated form of rhIL-2 with enhanced PK, specificity for induction of immune-suppressive regulatory CD4 + T cells (Tregs), and reduced stimulation of off-target effector T and NK cells. A library of rhIL-2 molecules was constructed with single site-specific, biorthogonal chemistry-compatible non-canonical amino acids installed near the interface where IL-2 engages its cognate receptor βγ (IL-2Rβγ) signaling complex. Biorthogonal site-specific pegylation and functional screening identified variants that retained engagement of the IL-2Rα chain with attenuated potency at the IL-2Rβγ complex.

RESULTS

Phenotypic screening in mouse identifies SAR444336 (SAR'336; formerly known as THOR-809), rhIL-2 pegylated at H16, as a potential development candidate that specifically expands peripheral CD4+ Tregs with upregulation of markers that correlate with their suppressive function including FoxP3, ICOS and Helios, yet minimally expands CD8 + T or NK cells. In non-human primate, administration of SAR'336 also induces dose-dependent expansion of Tregs and upregulated suppressive markers without significant expansion of CD8 + T or NK cells. SAR'336 administration reduces inflammation in a delayed-type hypersensitivity mouse model, potently suppressing CD4+ and CD8 + T cell proliferation.

CONCLUSION

SAR'336 is a specific Treg activator, supporting its further development for the treatment of AI diseases.

HVEM is a TNF family receptor that is a crucial regulator of epithelial and lymphocyte responses in the mucosal immune system (P3192)

HVEM is a TNF super family receptor, and previously we showed that epithelial HVEM is required for innate immune responses to pathogenic bacteria in the intestine and lung, and that it acts by enhancing epithelial Stat3 activation (Nature 488:222, 2012). Now, we show that HVEM is also an important regulator of lymphoid cells in the mucosal immune response. IL-17 and IL-22 are protective cytokines after oral infection with Citrobacter rodentium. Mice deficient for HVEM have a reduced IL-22 response by innate lymphoid cells (ILC) in the colon lamina propria at early times after infection. The adaptive immune response is also affected, with reductions in IL-17 and IL-22 by colonic lamina propria CD4+ T cells at days 9-21 after infection. The role of HVEM in mucosal lymphoid cells is more important for controlling bacterial burden and pathology at later times after infection, with the HVEM-dependent epithelial response acting earlier. Also striking, however, is the strong decrease in all intestinal epithelial lymphocyte populations (IEL) in mice deficient for HVEM, at steady state, even in the absence of infection. This reflects a decreased proliferative potential of IEL when HVEM is not expressed. Collectively, our findings establish HVEM as a crucial regulator of the mucosal immunity, affecting IEL homeostasis, innate epithelial responses and innate and adaptive responses by lamina propria lymphocytes.