Dimeric IgA specifically disables intracellular mutated oncodrivers

Despite their long half-life, therapeutic antibodies are considered ineffective against intracellular antigens due to their perceived inability to penetrate epithelial cells. Using recombinant antibodies targeting common mutations in oncogenes, we show that dimeric IgA, but not the same antibody on an IgG backbone, penetrates human epithelial cancer cells through PIGR-dependent directional transcytosis, specifically neutralizing mutated oncodrivers and expelling antigens outside the cell, bound to secretory IgA. Accordingly, targeting of KRasG12D or IDH1R132H with antigen-specific dimeric IgA abrogated the growth of different carcinomas in a mutation-specific manner, including in syngeneic tumor-bearing immunocompetent mice. Our results provide a rationale for developing PIGR-targeting tumor cell-penetrating antibodies to effectively target common mutations in intracellular oncogenes that drive many aggressive and frequent human cancers.