Researchers at the Dartmouth’s Thayer School of Engineering, Dartmouth Medical School, and the biotechnology firm GlycoFi, Inc. are reporting the complete humanization of the glycosylation pathway in the yeast Pichia pastoris. What that means is that they were able to replace four yeast genes by substituting them with over 14 heterologous human genes, all part of the same biochemical pathway. The findings were reported in the latest issue of Science.
The company explains its technology:
GlycoFi’s proprietary technology is based on a library of yeast strains that have been engineered to perform specific human glycosylation at high fidelity. About 70% of all therapeutic proteins are glycoproteins and require the attachment of sugar structures (i.e. glycosylation) to attain full therapeutic activity. Current manufacturing methods based on mammalian cell culture do not allow for the control of glycosylation and produce a mixture of different glycoforms; some of which are more active then others and some of which have no activity at all.
GlycoFi’s glycoengineered yeast strains have been optimized to produce proteins with one particular glycoform at high uniformity. By expressing a given protein in different glycoengineered yeast strains GlycoFi can generate a library of glycoproteins, all with identical peptide backbone but with different sugar structures attached to them. This allows for the identification of the glycoform with the highest therapeutic potency, and creates opportunities to optimize a drug’s therapeutic profile. Since many therapeutic characteristics such as pharmacokinetic stability, bioavailability, tissue specific targeting are dictated by sugar structures GlycoFi’s technology can be broadly applied to all glycoproteins, including growth factors, fusion proteins, and monoclonal antibodies.
GlycoFi refers to this approach of controlling a protein’s glycans in order to optimize a therapeutic protein as GlycoDesign™. Once the proper glycoform has been isolated, the same strain that produced the protein in research quantities can be used in a large scale production process. Yeast based protein manufacture is well established in the Biopharmaceutical industry, for example half the world’s supply of recombinant insulin is made in yeast.