Human Antibody - Human Rnase Fusion Proteins for Tumor Therapy
Stefan Dübel
Technische Universität Braunschweig, Institute of Biochemistry and Biotechnology, Germany
Abstract:
The modification of the Immunoglobulin Fc part offers various ways to improve the efficacy of naïve IgG for tumor therapy. Here we discribe a strategy based on the addition a new effector function, which allows a different therapeutic paradigm. This approach was hampered for decades by the lack of human fusion partners as effectors. For example, many immunotoxins have been designed and tested, but all to often caused severe side effects due to their immunogenicity and/or unspecific toxicity. Further, their production frequently requires refolding steps. Here, human effector domains may better be employed to avoid these disadvantages.
A now well established class of effectors are RNases. They are usually non-toxic while in circulation but highly effective in cell killing after internalization. We engineered and succesfully produced in mammalian cells an entirely human immunoenzyme directed against CD30+ lymphomas. It was constructed from an scFv-Fc antibody fragmennt and a human RNase. It did not affect the human embryonlal kidney cells used for its production by secretion into the supernatant at concentrations up to 60mg/L, but strongly inhibited proliferation of CD30+ lymphoma cells with an IC50 = 3,3 nM. Our design also improved resistence to RNase inhibitor without the necessity to mutate the human RNase sequence, thus eliminating the risk of added immunogenicity from this end.
