Advances in plant-made vaccines revive interest in plant-produced pharmaceuticals and edible drugs

Recent progress in developing and testing plant-made vaccines has revived interest in plant-produced pharmaceuticals, including edible drugs, for human use. Advances in technology and manufacturing could boost the uptake of therapeutics made in this way, say Hugues Fausther-Bovendo and Gary Kobinger in this Perspective.

Therapeutic proteins such as antibodies, hormones, cytokines, and proteins in vaccines are generally produced in bacteria or eukaryotic systems, including chicken eggs and mammalian or insect cell cultures. In 1986, scientists proposed the use of plants for the production of these proteins; called "molecular farming," this process can be less resource-intensive, less costly, and less likely to be a source of contaminants.

So far, one plant-derived therapeutic protein for human use has been approved (in 2012, for Gaucher disease). In 2019, a plant-produced influenza virus vaccine completed phase 3 clinical trials with promising results, and in spring 2021, phase 3 trials for a plant-made vaccine against SARS-CoV-2 began. Fausther-Bovendo and Kobinger highlight several advantages that plant-produced proteins hold for vaccine development, in particular, citing the strong immune response the plant components of virus-like particles in vaccines can generate, which may reduce the need for adjuvants.

Given orally, plant-made therapeutics are also interesting to consider, say Fausther-Bovendo and Kobinger; they might require minimal processing, thus possibly skipping expensive and time-consuming steps in the manufacturing process. Edible vaccines – still predominantly in the preclinical stage of development – are also currently under development, the authors note.

Compared to proof-of-concept edible vaccines tested decades ago, which generated weak immune responses, new edible plant-made vaccines could now generate more powerful immune responses, thanks to improved technology. Because doses for therapeutics are much higher than for vaccines, investment in manufacturing infrastructure must increase to achieve large-scale manufacturing of plant therapeutic products, Fausther-Bovendo and Kobinger say.