Green algae are cheap to grow, hard to kill, and quick to thrive. Such traits make the tiny plants an ideal production factory, one that is already being extensively explored as a source for biofuels. But a few people are also looking to algae to do a completely different brand of work: the manufacturing of therapeutic drugs, a system that could one day produce large quantities of certain drugs at one-thousandth of today’s costs.
A huge number of so-called biologic drugs, made up of proteins rather than small molecules, are produced, en masse, by bacteria, yeast, or mammalian cell culture–the cells produce proteins that are processed and turned into therapies for cancer, multiple sclerosis, and diabetes, among many other diseases. But such methods can be expensive to set up and maintain: Feeding them requires large amounts of nutrients, sustaining them requires large amounts of energy, and creating sterile facilities is a costly proposition. Stephen Mayfield, director of the San Diego Center for Algae Biotechnology at the University of California at San Diego, believes that algae, which subsist on sunlight and carbon dioxide in the air, could be an ideal and cost-effective substitute.
In a paper published in the Plant Biotechnology Journal, Mayfield and his colleagues looked at the versatility of the green alga Chlamydomonas reinhardtii in order to determine whether it had the potential to act as a robust drug factory. They inserted genes for production of seven different therapeutic proteins currently being made in yeast, bacteria, and mammalian cells, including interferon (for multiple sclerosis) and proinsulin (for diabetes). Of the seven, the algae produced four proteins at levels high enough for commercial use and in forms that were identical to those made by bacterial and mammalian cell systems, and are just as easy to isolate and concentrate.
Complicated proteins that are produced in mammalian cell culture, such as the potent multiple sclerosis drug Tysabri, currently cost an estimated $150 or more per gram of protein. (The number is estimated because few companies release such statistics.) In green algae, Mayfield says, it’s closer to a nickel. “That’s because it’s a plant and it grows in minimal media, pulling carbon dioxide out of the air and using sunlight for its energy source.”
In addition to producing drugs more cheaply, algae plants are cheaper to build. Startup costs for mammalian cell culture plants are the “biggest bottleneck in developing new protein therapeutic drugs,” says Mayfield. “Clinical trials are expensive, but before you even get to the clinic, you have to invest $600 million to build a facility to produce it.”