Europe's first clinical trial to test a human monoclonal antibody (mAb) made in genetically modified tobacco plants has been given the go-ahead by UK regulators. The Medicines and Healthcare Products Regulatory Agency approved in late June Pharma-Planta's phase-1 clinical trial to test an anti-HIV type 1 protein applied as a vaginal microbicide to stop transmission of the virus between sexual partners. Pharma-Planta, a consortium of 39 academic principal investigators and industrial partners in Europe and Africa funded by the European Commission, launched the project in 2004 as part of the Sixth Framework Program. The partners' goal was to road test the regulatory pathway in Europe by taking a candidate plant-made biotherapeutic and moving it beyond proof-of-concept studies to clinical evaluation. The mAb, designated 2G12, neutralizes HIV by binding to its gp120 surface glycoprotein. If safe, the product will be tested for effectiveness in protecting users against HIV infection. While the clinical trial is conducted at the University of Surrey in the UK, 2G12 is being produced in specialized greenhouses at the Fraunhofer Institute for Molecular Biology and Applied Ecology in Aachen, Germany. The approval is a major milestone. “This is indeed a big step forward in Europe, where development was hampered because of concerns over foods and GMOs [genetically modified organisms],” says Charles Arntzen, a co-director at the Biodesign Institute of Arizona State University in Tempe and a leader in the development of plant-produced vaccines. Perhaps more importantly, Pharma-Planta's step forward could boost the entire field of plant-produced vaccines where a “lot of positive results and exciting things” are ongoing, according to Arntzen. For instance, three major US plant-based, protein production facilities are up and running, providing “abundant capacity,” and presenting a challenge “to fill the pipeline with products to use that capacity.” Prospects now are bright for meeting part of that challenge, with several vaccines—some for sexually transmitted diseases and others for virus-induced diarrheal diseases—moving forward. Additionally, the carrot cell–produced enzyme taliglucerase alfa for treating Gaucher disease, developed by Protalix BioTherapeutics of Carmiel, Israel, has completed phase 3 clinical trials and may soon be licensed as a “biobetter,” Arntzen says. Plants are attractive bioreactors because they are inexpensive and provide a versatile expression system for recombinant protein.
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Fox, J. HIV drugs made in tobacco. Nat Biotechnol 29, 852 (2011). https://doi.org/10.1038/nbt1011-852