THE PRESENT STATE OF GENE TECHNOLOGY IN THE MANUFACTURE OF HUMAN COAGULATION PROTEINS
Authors: Vehar G A 
Published: August 2018

The production of pharmaceuticals from human plasma that are useful in the treatment of bleeding disorders had its beginning with the development of the Cohn fractionation procedure in the 1940's. As a result of these advances, concentrates became available for the treatment of the hemophilias. Although of low purity and subject to contamination by hepatitis virus, the availability of these compounds resulted in dramatic improvements in the life expectancy and quality of life of afflicted individuals. The numerous problems associated with production of pharmaceuticals from pooled plasma made these products obvious goals for recombinant DNA technology as soon as the commercial aspects of the field became apparent. The subsequent contamination of blood products with the AIDS virus has resulted in an urgent need for a production source that is independent of human plasma. Several industrial and academic laboratories have cloned the cDNA's for human factors VIII and IX. In addition to these proteins, the utility of factor Vila in the treatment of hemophiliacs with inhibitors has shown promise. Efforts to develop a recombinant preparation of factor Vila are at a comparable stage of development as factors VIII and IX. Continuing efforts have resulted in the successful expression of these recombinant proteins in mammalian cell lines, thereby successfully completing the first steps of commercial development.

Although much interest has focused upon the theoretical superiority of recombinant proteins as therapeutics, one must keep in mind that there are numerous developmental aspects of large-scale production and regulatory issues that must be addressed and solved before these drugs will be available. The coagulation proteins are complex glycoproteins that will in all probability require mammalian cell cell culture in order to produce functional proteins. The fact that these preparations will be administered over the lifetime of the patient serves to reinforce that the recombinant products be as similar to the natural proteins as possible, further supporting the concept of mammalian cell expression systems.

Regulatory approval of a recombinant product are fundamentally no different than those for any other product in regards to efficacy, potency, purity, and identity. There are, however, additional considerations that must be addressed in the production of recombinant cell culture derived biologies. These relate to the possible presence in the final product of pathogenic and tumorigenic agents, and possible contamination by cell culture and cell substrate compounds. A detailed characterization of the production cell line will therefore be required, including identification and characterization of any associated viral particles. These cells must be capable of being reproducibly grown, while maintaining protein production, on ascale (tens of thousands of liters) suitable to meet the market demand of the specific protein. Apurification process must be established capable of handling the resulting large volumes of feedstock, generating a protein preparation of high purity (greater than 99% pure). Numerous assays must be developed to quantitate the purity and identity of the resulting recombinant pharmaceutical on a lot by lot basis.

Studies to date have shown that recombinant forms of factors VIII and IX, produced by laboratory processes, are very similar to the plasma-derived forms as assessed by a variety of in vitro and in vivo tests. Although these results are promising, the ultimate safety and efficacy testing of these drugs will have to await the initiation of human clinical trials. Such studies will have to await the successful completion of the certain regulatory concerns. Clinical trials should begin within the near future, hopefully leading to a source of these products independent of pooled human plasma.