Cetuximab produced from a goat mammary gland expression system is equally efficacious as innovator cetuximab in model systems of cancer.

Humanised monoclonal antibodies have proven a very effective mode of therapy for a wide range of conditions. With many of the monoclonal antibody drugs now coming off patent there is an increasing interest in developing biosimilar, or even biobetter, forms of these drugs. With the commercial competition associated with such generic products there is increasing demand for improved production and purification system for biosimilars. Cetuximab, also known as Erbitux, is widely used in cancer therapy, especially in advanced colorecal cancer, metastatic non-small cell lung cancer and head and neck cancer and it will come off patent in the near future. We have previously reported on a genetically engineered goat system to produce cetuximab (gCetuximab) in milk. Herein we now report on the further charactization of the gCetuximab produced utilizing additional and more sophisticated biological assays. There is similar bioactivity of the gCetuximab compared with the commercial product produced in mammalian cell culture. In particular both cetuximab antibodies selectively target EGFR and induce its internalization to down regulate EGFR signaling. Both forms have very similar half life in animals and in a HT29 colorectal cancer xenograft model have similar efficacy. We also show that the toxin MMAE can be conjugated to gCetuximab, that this targets it to cells and that this results in direct cell killing in HT29 cells. This demonstrates that the gCetuximab will also be a viable vehicle for antibody drug conjugate based therapies. Taken together, this shows that the goat milk monoclonal antibody production system is an effective way of producing a biosimilar form of cetuximab.