To overcome these limitations, a new class of IL-2 receptor β- and γ-chain (IL-2Rβγ)-biased agonists is currently being developed, some of which are additionally targeted to cell-surface proteins overexpressed in tumours or surrounding stroma to enhance their local tumour retention, such as CEA-IL2v8 and FAP-IL2v12,13. This evidence concerns the gene FAP and neoplasm.