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How genes are identified, isolated, modified, and produced on a large scale using bacteria or CHO cells to generate the desired protein, whether it be, insulin, mAbs, TNF‐inhibitors, or others has been described in this chapter so far. Following the production of the therapeutic protein in a manufacturing facility, it is purified through a complex process, and formulated into a form that makes it stable for storage and shipment to the pharmacy, hospital, or clinic where it will be delivered or administered. Finally, the therapeutic protein (biopharmaceutical) is administered by an injection either by a medical professional or by the patient.

The latest breakthroughs in biotechnology research and development (R&D) have been in gene therapies. The initial stages of gene therapy development still require identifying a target gene that is clinically important. There are various ways that gene therapy can be used therapeutically. For example, a patient may be missing a gene that codes for a life‐sustaining enzyme, in which case the goal is to introduce that missing gene into the patient, or a patient may have a defective gene that requires modification to restore its normal function. What is unique to gene therapy versus the majority of biological medicines to date is that with gene therapy, the gene is introduced into the patient and the patient makes the protein; the protein is not produced in bacteria or in CHO cells, but rather in the patient.

Like the plasmid vectors described previously for manufacturing biologic drugs like insulin, gene therapies typically require a vector to be successfully administered to a human patient. Viral vectors are the most commonly used vectors in gene therapy representing nearly 70% of clinical trials.²⁷ Viruses make good vectors due to their natural ability to infect cells. For clinical use, the viruses are modified to avoid causing disease when given to patients. Some viruses, such as retrovirus can incorporate the genetic material into a human cell and chromosome, whereas adenoviruses introduce their DNA into the cell, but the DNA does not get integrated into the chromosome. There exists a broad spectrum of viral vectors for delivering gene therapies and their choice can be influenced by factors such as how much expression is desired and for how long.²⁷