Cell Based Delivery
Scientists are constantly searching for new ways to deliver therapeutic drugs to the human body in ways that are more effective and less expensive. For instance, hemophilia is characterized by an inability of blood to clot normally. Therapeutic injections of clotting factor (Factor VIII), though often effective, are expensive, are constantly needed, and can cause the body to develop antibodies that interfere with the clotting factor. One alternative approach that has researchers excited is called autologous cell based delivery (AuCBD). In this method:
Living tissue, usually muscle cells, are extracted from the patient
The patient’s cells are injected with genetic material that codes for therapeutic proteins
The tissue is cultured in vitro
Samples of the tissue are tested for the rate of production of the desired biotherapeutic protein
Implants of the tissue are placed in the patient’s body
By using the patient’s own cells as a protein factory, doctors can avoid the immune reactions that often result from donor materials. Tissue implanted in this way can survive for many months in the patient’s body. During that time, the cells of the implant are constantly producing proteins that the body can use to fight or compensate for the disease.
Various classes of proteins can be synthesized in this way: antibodies, hormones, growth factors and enzymes. By using living cells as protein factories, doctors hope to give long-term treatments to their chronically ill patients. Older non-tissue techniques, such as biodegradable microspheres, unfortunately provide only a week or two of continuous dosing before they are degraded. Animal studies have shown that tissue implants can last six months or longer.
It is important to culture the tissue in vitro so as to gauge the amount of biotherapeutic agent a standard size implant will deliver. Standard size is 20 mm long and one to two mm in diameter. Doctors can then know how much material to implant, using standard surgical procedures. It is thought that this process will have benefits for a wide variety of chronic or cardiovascular diseases. One cited example deals with stimulating the growth of new blood vessels (angiogenesis) around the heart of patient with inadequate blood supply. Several different types of proteins, including growth factors, are known to be angiogenetic. By implanting the properly prepared protein-producing tissues near the heart, new blood vessels would be formed, providing the heart with new sources of oxygen and glucose. Other possible uses of AuCBD include tissues that produce Factor VIII (used to treat hemophilia) and erythropoietin (for the treatment of anemia).