Antibody
therapy is a validated treatment approach for several
malignancies. All currently clinically applied therapeutic
antibodies (Abs) are of the
IgG isotype. However, not all patients respond to this
therapy and relapses can occur.
IgA represents an alternative isotype for antibody
therapy that engages FcαRI expressing myeloid effector cells, such as neutrophils and monocytes.
IgA Abs have been shown to effectively kill
tumor cells both in vitro and in vivo. However, due to the short half-life of
IgA Abs in mice, daily
injections are required to reach an effect comparable to
IgG Abs. The relatively long half-life of
IgG Abs and
serum albumin arises from their capability of interacting with the
neonatal Fc receptor (FcRn). As
IgA Abs lack a binding site for FcRn, we generated
IgA Abs with the variable regions of the Her2-specific Ab
trastuzumab and attached an
albumin-binding domain (ABD) to the heavy or light chain (HCABD/LCABD) to extend their serum half-life. These modified Abs were able to bind
albumin from different species in vitro. Furthermore,
tumor cell lysis of IgA-Her2-LCABD Abs in vitro was similar to unmodified IgA-Her2 Abs. Pharmacokinetic studies in mice revealed that the serum exposure and half-life of the modified IgA-Her2 Abs was extended. In a xenograft mouse model, the modified
IgA1 Abs exhibited a slightly, but significantly, improved anti-
tumor response compared to the unmodified Ab. In conclusion, empowering
IgA Abs with
albumin-binding capacity results in in vitro and in vivo functional Abs with an enhanced exposure and prolonged half-life.