They found that the format with 2:1 antibody to cytokine ratio of p40-L19 scFv/L19 scFv-p35, a heterodimeric fusion protein in which the disulfide-linked p35 and p40 subunits of IL12 are fused to L19 scFv, displayed the highest tumor-targeting performance in biodistribution studies. The gene discussed is IL9; the disease is neoplasm.