Engineering of tandem bispecific IL-7 receptor agonist antibody promoting selective T cell expansion

Abstract

Interleukin-7 (IL-7) is indispensable for T cell development and homeostasis, and clinical studies have demonstrated its ability to restore T cell numbers in lymphopenic conditions. However, the therapeutic application of IL-7 has been limited by its short half-life and potential immunogenicity of recombinant variants. To overcome these challenges, we engineered a fully human tandem bispecific antibody, TB4, that functions as a potent IL-7 receptor agonist by cis-targeting IL-7 receptor alpha (IL-7R alpha) and the common gamma chain (gamma c). The tetravalent tandem scFv-Fc architecture, coupled with optimized linker length, conferred markedly enhanced binding affinity and avidity compared to the knobs-into-holes bispecific format, with domain orientation designed to limit unintended gamma c binding. At the cellular level, TB4 engaged both receptor subunits and exhibited reduced internalization dynamics, features that are likely to contribute to the sustained STAT5 phosphorylation observed in primary human T cells. Functionally, TB4 supported long-term T cell survival and expansion, but selectively promoted the expansion of CD4+ memory subsets, especially effector memory cells re-expressing CD45RA populations, in contrast to the broader effects of native IL-7. Transcriptomic profiling further revealed that while both TB4 and IL-7 activated proliferative gene programs, TB4 uniquely drove an antiviral and innate immune signature. Collectively, these findings establish TB4 as a next-generation IL-7R agonist antibody with a differentiated mechanism of action and potential as a precision immunomodulator that can selectively expand and reprogram T cells.