Adhiron binders as molecular tools for inhibiting activation dependent, IL-7 mediated long-term survival of CD4+ T-cells.

Tools that enable functional inhibition of the long-term effects of immunological signalling cascades remain challenging to develop, in part because biological outcomes often arise long after the initiating receptor-ligand interaction and lack accessible experimental readouts. Interleukin-7 (IL-7) cytokine signalling through the IL-7 receptor (IL-7R) exemplifies this problem, as IL-7-mediated survival signals in activated CD4+ T cells emerge over extended timescales, yet play a critical role in human disease. Here, we describe the development of engineered Adhiron binders as molecular tools to inhibit IL-7/IL-7R signalling. Using phage display against glycosylated human IL-7Rα ectodomains, we isolated 23 unique Adhiron binders. From this panel, we identified a lead binder, Adh-42, that binds both soluble and membrane-associated IL-7Rα. Adh-42 inhibited proximal IL-7R signalling events in human cells and abrogated IL-7-mediated rescue from activation-induced cell death in human primary CD4+ T-cell blasts (using a recently developed in vitro assay). Together, these findings demonstrate that Adhiron binders can be used to target a cell-surface cytokine receptor (IL-7R) and selectively inhibit downstream biological outcomes in human primary cells. This work establishes Adhirons as versatile molecular tools for probing IL-7 cytokine signalling and provides a framework to support the design and evaluation of future therapeutic strategies.