Peking University team cyclizes IL-2 and extends its half-life 4.5–5-fold in mouse autoimmune models

A team led by chemical biologist Wen-Bin Zhang at Peking University, together with rheumatologists Jing He and Zhanguo Li at Peking University People's Hospital, has engineered two topological variants of interleukin-2 (IL-2). The work was published in The Innovation Life doi.orgThe Innovation Lifedoi.orgOpen source ↗. In c-IL-2 the protein's termini are ligated into a ring. In cat-IL-2 two ring-shaped copies are mechanically interlocked into a catenane.

Low-dose IL-2 acts by expanding regulatory T cells (Tregs), but the cytokine's short serum half-life forces frequent injections. The authors addressed this by changing the connectivity of the protein backbone rather than attaching bulky modifications.

Design and pharmacokinetics

Both variants are genetically encoded and produced directly in E. coli cells by split-intein protein splicing, with a dimeric entangling motif called p53dim. According to the authors, no refolding is needed after purification. Circular dichroism spectra and binding assays showed that neither topology disturbed the native fold or receptor binding of IL-2.

In mice, wild-type IL-2 cleared from the blood with a half-life of 1.25 hours. For c-IL-2 and cat-IL-2 the values were 6.23 and 5.67 hours, about 5.0 and 4.5 times longer. The variants also showed higher proteolytic stability doi.orgThe Innovation Lifedoi.orgOpen source ↗.

Results in mouse models and human cells

In the MRL/lpr lupus mouse model, once-weekly low-dose c-IL-2 or cat-IL-2 expanded Tregs and reduced proteinuria, skin lesions and kidney injury. The effect matched that of wild-type IL-2 given weekly or three times a week. The weekly regimen also eased joint swelling and bone erosion in a collagen-induced arthritis model. In a Sjögren's syndrome model, c-IL-2 reduced salivary gland inflammation and improved secretion. No obvious systemic toxicity was observed at the doses and time frames tested.

In peripheral blood mononuclear cells from patients with systemic lupus erythematosus, both variants preferentially expanded Tregs and activated STAT5 signaling without raising the proportion of NK cells. RNA sequencing of patient-derived CD4+ T cells showed lower expression of genes involved in immune activation, antigen presentation and inflammation.

The authors note that dosing, long-term safety and immunogenicity still require systematic evaluation before clinical translation. The therapeutic evidence so far comes from mouse models and ex vivo human cells. They also argue that the approach could be extended to other cytokines doi.orgThe Innovation Lifedoi.orgOpen source ↗.