After years of regulatory wrangling, a first-of-its kind trial of an HIV prophylactic churned out by GM tobacco plants is underway in the UK.
The phase I trial, which began in June, will test the safety of a vaginally-applied antibody called P2G12 in 11 healthy women, with preliminary results expected in October, Julia Boyle, director of the Surrey Clinical Research Centre at the University of Surrey, UK said at a press briefing today. The antibody recognizes proteins on the surface of HIV to block infection, though it hasn’t yet been proven effective in humans.
The medicine is the first plant-produced antibody to be greenlit for clinical testing by Britain’s Medicines and Healthcare products Agency (MHRA). It took about a year to get that agency’s stamp of approval because it wanted assurances that the drugs did not contain allergenic plant sugars or pesticides, Boyle tells Nature. But she hopes the process will set a precedent, allowing swifter approval of future trials involving other plant-made antibodies.
The Pharma-Planta consortium of 28 academic institutions and 4 small companies, which is leading the trial, began discussions with the European Medicine Agency in 2006 about conducting a clinical trial. However the consortium balked at the fees required by the EMA and turned to the MHRA instead.
It also took the consortium three-and-a-half years to secure a permit to manufacture the drugs at a special facility in Aachen, Germany. The process yields 5 grams of purified antibody from 250 kg of tobacco.
The road to regulatory approval for the microbicide — or any plant-produced biologic drug, for that matter – will likely resemble a pea tendril more than a bean stock. No matter how it is produced, P2G12 antibody hasn’t been shown to actually prevent HIV infection in clinical trials, so a version made by tobacco plants won’t see approval anytime soon. P2G12 would also likely be just one ingredient in a cocktail of plant-produced antibodies, Julian Ma, a member of the Pharma-Planta consortium at St. George’s University in London, said at the briefing.
Other plant-produced biologic drugs are creeping from the garden to the clinic. The pharmaceutical firm Bayer has received approval from the US Food and Drug Administration to test the safety of tobacco-produced human antibodies that attack non-Hodgkin’s lymphomas. A Canadian firm, SemBioSys Genetics, found in a trial of 23 volunteers that its safflower–produced version of insulin is safe and works as well as a version of the drug already on the market.
Image courtesy Bayer