One of three candidate compounds, in which p40 and p35 formed a covalent heterodimer and each subunit was fused to a molecule of scFv(L19) (known as p40-scFv(L19)/scFv(L19)-p35), demonstrated excellent tumor-targeting efficacy, as evaluated via biodistribution analysis, and potent antitumor activity in animal models of teratocarcinoma, showing superior performance compared to that of the other two IL12-scFv(L19)-FLAG candidates (134). This evidence concerns the gene IL9 and neoplasm.