Selective impact on regulatory T cells with sustained functional phenotypes by the interleukin-2 mutein VIS171 in a...

The interleukin-2 mutein, VIS171, was engineered to extend half-life and enhance selective binding and expansion of regulatory T cells (Tregs) expressing high levels of the trimeric interleukin-2 receptor. This study evaluated the effects of VIS171 on immune cell populations in nonhuman primates, focusing on its ability to selectively expand Tregs, and then characterized their phenotype during expansion and contraction. Naïve rhesus macaques were treated subcutaneously with VIS171, along with daily rapamycin. VIS171 was well tolerated with repeated administration. Tregs, identified as cluster of differentiation CD4⁺CD25⁺FoxP3⁺ or CD4⁺CD25⁺CD127^lo cells, expanded significantly after treatment. Peak Treg expansion was evident in the peripheral circulation between days 5 and 7 postdose, with frequency and absolute counts markedly increasing from 4- to 6-fold after administration. In contrast, no significant effect was found in cytotoxic T lymphocyte populations, highlighting the specificity of VIS171 for expanding Tregs. Single-cell RNA sequencing revealed 3 distinct Treg clusters: resting (SELL^high) Tregs and 2 Treg subsets with distinct activation and metabolic profiles (HACD4^high and TIGIT^high). The transcriptomic profile of expanded Tregs was consistent, with an effector Treg signature associated with immunoregulatory function. Differentiation signature scores indicated preserved Treg functionality after expansion. These findings suggest that VIS171 with rapamycin promotes robust, selective, and durable Treg expansion, offering a strategy to enhance transplant tolerance without broad immunosuppression.