With much of the low-hanging fruit in cell culture optimization already plucked, progress today is centering on how to produce more complex molecules, improving bioproduction consistency and efficiency, and developing better predictive tools for media and processing performance.
Work on multispecific antibodies isn’t new. They offer many compelling advantages, such as attacking signaling pathways whose redundancies often circumvent monospecific therapeutics. However, creating multispecific antibodies has been challenging.
Speaking at Terrapin’s “Cell Culture World Congress” last month, Ingo Gorr, Ph.D., senior research scientist, cell culture research, Roche Pharmaceuticals, reviewed an approach to developing bispecific antibodies that overcomes many past problems.
“Most anticancer drugs do not work 100 percent; there is usually some leakage,” said Dr. Gorr. “Whenever you can hit two targets in a signaling pathway your drug is likely to be more effective because you’re not allowing the cell to bypass and block the drug’s action.”
According to Dr. Gorr, Roche’s CrossMab technology can convert existing antibodies into IgG-like bispecific antibodies. Two problems must be solved to produce the desired bispecific antibody exclusively and avoid a large mixture: 1) effective induction of heterodimerization of the two heavy chains and 2) discrimination between the two light-chain/heavy-chain interactions.
To accomplish heterodimerization, Roche uses a technology invented by Genentech, which it calls “knobs into holes.”
“Our approach is to alter amino acids in the C-terminal of the antibody. Within one of the heavy chains we build a knob consisting of large amino acids, and on the respective other side we build a hole with small amino acids so that we favor or force pairing of heterogeneous heavy chains,” he explained.
Using this technique, Roche developed a bispecific IgG-like antibody for Ang-2 (angiopoietin-2) and VEGF-A. “We moved it into mouse testing where it was very efficient in preventing tumor growth,” said Dr. Gorr. Because the molecule is similar to naturally occurring IgGs, it has a similar half-life, is not prone to degradation, and is expected to exhibit reduced immunogenicity.
“We get really high titers compared to other multispecific antibody production approaches because the cell recognizes it as an antibody. We also avoid production of many side products and end up with very few product-related impurities present. Development can be done in fast timelines.”