Antibody Expression in a Fraction of the Time 4/26/05
Scientists from Cell Genesys Inc., South San Francisco, recently published a paper describing a novel gene expression method for producing full-length monoclonal antibodies with greater efficiency than current methods. The technology, they say, could potentially be used for commercial-scale production of monoclonal antibodies.
One of Cell Genesys’ investigational areas is in gene therapies for cancer, which led them to look at using a monoclonal antibody. “We were evaluating the problem that if we were going to deliver a monoclonal antibody using a viral vector, how were we going to get the genes expressed in such a way that they would combine into an active antibody,” says Peter Working, PhD, senior vice president, research and development, Cell Genesys.
“Most of the technologies that were currently available at that time either were too big, they required too many nucleotides to fit into our viral vectors, or they resulted in the uneven expression of the long and short chains of antibodies, meaning that you didn’t get a biologically active antibody in the end.”
In looking for a way to make full-length, four-chain antibodies at active levels in vivo with a single injection of gene therapy, the researchers found a strategy that uses a short self-processing sequence derived from the foot-and-mouth disease virus, referred to as 2A, to express full-length antibodies from a single open reading frame. The result of the 2A sequence was the even expression of heavy and light chains that are linked together to become an active antibody.
As reported in the study in the April 17 on-line issue of Nature Biotechnology, the 2A antibody expression process worked in vivo where the administration of adenovirus vector expressing an anti-angiogenic monoclonal antibody targeting VEGFR resulted in significant anti-tumor efficacy. The results, they say, show broad implications for monoclonal antibody therapy for treatment of cancer or other diseases.
Cell Genesys is also pursuing the process as a commercial means for producing antibodies and other complex proteins in high quantities. They found that they could generate cells that produce very high quantities of a desired antibody in much less time than current cloning methods that can take nine months to a year to generate an initial antibody-producing cell line, Working says.
“The standard clone in final production will produce 10 to 20 picograms per cell per day of the protein, which is a very small amount, but this is multiplied by millions of cells,” says Working. “Using this 2A linking technology and a viral vector, we found that we can, within four to six weeks, produce tens or hundreds of initial clones that produce the same 10 to 20 picograms per cell per day. In another two to three weeks we can produce clones that reach levels of 20 to 40 picograms per cell per day.”
This provides a much abbreviated clone selection process, which is costly and labor intensive, he says and results in a system that produces twice as much product in a fraction of the time.
“This technology could potentially be of great value to antibody-producing companies and other companies that produce any complex multi-chain proteins, which is what this is best suited for. Theoretically, we see no limitations on the kinds of proteins we can produce.”
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