Manufacturing

This section presents a general example of the process used to manufacture enzymes for use in treating humans. It is not specific to Pompe disease. Depending on the particular enzyme being manufactured, the process can vary.

The production of any genetically engineered enzyme tends to be both long and complex. Although great strides have been made through technology, the manufacturing process takes some time, spanning months to years.

Unlike pharmaceutical drugs, which are made from chemicals, biotechnology drugs, such as genetically engineered enzymes, come from living organisms and their products. Biotechnology manufacturing requires the combination of several fields of science--microbiology, biochemistry, engineering--with large-scale industrial processes so that microorganisms, cells, and/or tissue cultures can be engineered to manufacture a biological product. The cost and difficulty involved in manufacturing these products may be higher than that of a conventional pharmaceutical drug.

What is an enzyme?

An enzyme is a protein that triggers or "catalyzes" a biochemical reaction. Some of the critical functions of enzymes include:

Regulating the growth of the body from a single cell to a mature organism
Converting food to energy to satisfy the body's needs
Breaking down or building up certain substances within the cell

Genetic engineering is the process that allows scientists to change the genetic makeup of an organism so that it can produce human proteins, including enzymes. This technology, known as recombinant DNA technology, makes it possible for scientists to make large quantities of therapeutic enzymes that in the past were only available in very small quantities, if at all.

These manufactured proteins (enzymes) can then be administered to patients who lack or are in short supply of these enzymes to replace the missing or abnormal enzyme. There are three main stages to producing recombinant human enzymes for use in enzyme replacement therapies (ERT).

Stage One: Cell Culture, Growth, and Harvest

Before genetic engineering, it was extremely difficult to purify enough enzyme to treat even a single patient. Today, special "cell production lines" have been created for large-scale manufacturing. These cells are frozen in a cell bank or storage facility before use, and they provide the starter material for the genetic engineering process.

The most commonly used cell production line in genetic engineering is the Chinese hamster ovary cell, commonly abbreviated as "CHO cell." To produce a certain enzyme, the gene for that enzyme is obtained from human DNA and inserted into the CHO cells, causing them to express or "manufacture" the enzyme.

Cultivating and harvesting the cells requires advanced technology and a step-by-step procedure that must be followed exactly. First, the genetically altered CHO cells are grown in a large tank called a bioreactor, in which the environment is carefully controlled. To feed the cells and enable their growth, a liquid broth of many different nutrients, such as sugar, is constantly added to the bioreactor.

A special propeller (or a machine that keeps the cells moving) keeps the cells in constant motion, which is also critical. Over the course of several weeks or months, the CHO cells multiply like a living production factory. In fact, each bioreactor can contain more than 20 million CHO cells. The cells produce the enzyme, and they shuttle it out into the liquid. Liquid is removed daily and the enzyme is then drawn off and collected for purification.

Stage Two: Enzyme Purification

Because enzymes are proteins, they are digested if swallowed, which makes taking enzymes by mouth (such as by tablet or liquid, for example) very difficult. Because of this, enzyme replacement therapy must be injected directly into the bloodstream and must meet very high purity standards.

Chromatography is a way of separating and isolating the components of a mixture, and in the ERT production process, it is used to remove unwanted substances from the recombinant enzyme product. There are generally several stages of chromatography that continue to purify the recombinant enzyme. Rigorous testing takes place during every stage. Afterwards, the product is ready for formulation (development to a final product). It is then transported to a sterile area, where it is put into its final packaging.

Stage Three: Filling and Finishing

In the last stage of the production process, the manufactured enzyme is filled into vials in "the fill room," which is kept more sterile than a hospital surgical suite to prevent contamination. In the case of many recombinant therapeutic products, the vials are lyophilized, which means that they then go into a freeze dryer.

During this time, water evaporates to leave a cake-like dry product that is more stable and easier to store. Then, the vials are ready to be sealed, labeled, and inspected. Samples of the finished product are sent to a lab for extensive Quality Control (QC) testing of factors such as appearance, potency, purity, and sterility.

Then a Quality Assurance (QA) process reviews the documents associated with the manufacturing process to ensure that all procedures have been followed correctly. Only after QA approval can the enzyme be shipped out from the manufacturing facility.

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