By CRG staff - interview with William Gavin of GTC Biotherapeutics

Goat PharmingGTC Biotherapeutics was the first company to bring a pharmaceutical product to market which had been derived from transgenic animals, using goats modified to produce therapeutic proteins in their milk. The product, ATryn (an antithrombrin) received regulatory approval in the EU in 2006 and in the U.S. in 2008. Dr. William Gavin, DVM, is the chief veterinarian at the company's Massachusetts farm.

How many goats does GTC currently have on the farm? Do you think of it more as a "farm" or a "lab"?

While our facility in Charlton is indeed a farm, it is a very unique and specialized facility licensed by the appropriate regulatory agencies to house the goats and to produce human recombinant therapeutic proteins in their milk. Currently, we have approximately 600 goats on the farm.

After inserting the transgene into early stage embryos, what are your success rates getting live births and offspring that carry the transgene? What happens to the offspring that don't carry the transgene?

We use more than one technology to insert the transgene of interest, and while we do not disclose our success rates for those programs, we do feel we have developed a certain expertise in this area and have a (comparatively) high level of success.

With regard to offspring that do not carry the transgene, there are other potential uses for those animals within our operations (such as use in breeding in future programs). We work very hard to efficiently use animals within our operation.

How do you respond to concerns about animal welfare in using goats to produce biotherapeutics rather than, say, bacteria?

We do not believe that there are any animal welfare concerns inherent in the use of goats for producing milk that contains a human recombinant therapeutic. On the contrary, the goats at GTC are very well cared for and enjoy some benefits not found on a traditional dairy farm, such as full-time veterinarian oversight and regular health checks.

The bottom line is that we are maintaining and milking dairy goats in a very similar fashion to how it is done in the commercial goat milk industry - albeit with significantly more monitoring and documentation. The only difference is that our animals have an additional piece of DNA that affords them a unique ability to produce an additional specific recombinant protein in their normal milk production.

With regard to comparisons to the bacterial fermentation platform for biologics (or other production systems for recombinant therapeutics), we at GTC feel that our system has a number of significant advantages in comparison. Not only can we produce a number of molecules that bacterial fermentation cannot, we can also produce therapeutic proteins in a very cost effective fashion. As you are aware, the state of our health care system begs for a capability to produce medicines that will start to bring down the cost of life saving therapies. Lastly, there are at times significant limits to alternative production systems that impact the availability of these medicines and therefore limit their usefulness to the general population that might need them. Our system of production has clearly shown a significant ability to produce large quantities of these medicines that could meet the current unmet medical needs for more patients

Do you see transgenic dairy goats as the ideal production method for drugs like ATryn? Is there a "next step" from here, or is it just a matter of tweaking the system you already have in place?

In the case of antithrombin/ATryn, yes, we believe that the product is best suited for the goat. Our next steps from here are always looking for improved efficiencies across the whole process but we will be staying with the goats as the production species. Additionally, we will be exploring unmet needs for this product through the development of new indications that have not been previously explored, possibly due to limited supply or perhaps over safety concerns of the risks of blood-borne pathogens, for the competing plasma-derived alternative that is currently on the market.

As you develop your breeding herd, what qualities do you select for to mold the perfect human-protein producers?

The attributes that we look for are what you might look for in any commercial dairy operation across the country. We look for those goats that pass on superior dairy genetics with regard to daily volume of milk production as well as overall length of lactation. Additionally, all dairy animals have slight variability that impact the proteins found in their milk, so we also select for goats with optimal protein production.

As GTC and other companies scale up production herds, are there likely to be opportunities for independent farmers to start their own herds or manage a contract operation, or are companies more likely to keep production confined to their own secure sites?

Due to the rigors imposed (e.g. extensive and on-going documentation requirements) by regulatory authorities, we believe that it is highly unlikely that these activities will be contracted out to independent farmers.

What other techniques or products would you consider to be "the competition?"

As you mentioned, cell-based fermentation production technologies are currently used for the production of many therapeutic proteins.  Unfortunately, that technology is a very inefficient system for many proteins, unable to produce other proteins, and where it is employable it does not offer the "scalability"-the ability to increase production easily and inexpensively-of transgenic mammary gland protein production.

GTC has an issued U.S. patent broadly covering the production of therapeutic proteins in the mammary glands of mammals until 2027, and thus does not foresee any near-term direct competitors.

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