The “Pharming” Challenge - Governing Risk in GM Agriculture - page 181

First, unlike first-generation GM crops, PMPs are designed to have
a physiological effect on man and/or higher animals, hence the hazard
characteristics of the introduced protein might be of greater concern.
Secondly, an entirely different breeding rationale applies. Plants will
be designed, for example, for maximum yield, special morphology, and
growth habit suited to a specific harvesting method that can be used with
the PMP application, absence of metabolites that may compromise prod-
uct integrity or quality during bioprocessing. 34 Pharm crops are consid-
ered production facilities that have to be optimized for maximum yield
of the target substance. Human and environmental exposure could there-
fore be increased compared to first-generation GM crops. Depending on
the expression system maximum yields of up to 25 and 31 percent of
total soluble protein (TSP) 35 and 80 percent TSP 36 have been achieved
(the latter of which in greenhouse experiments). This would constitute
a 700- to 5,000-fold increase in yield of transgene products compared to
first-generation GM crops. 37
Thirdly, the likelihood of unintended secondary effects might be
higher, and the hazard characteristics of GM plants might thus be of
34 H. M. Davies, Plant-made Pharmaceuticals: An Overview and Update. in Agricul-
tural Biotechnology: Beyond Food and Energy to Health and the Environment, 59-70
(National Agricultural Biotechnology Council 2005).
35 H. Daniell et al., Breakthrough in Chloroplast Genetic Engineering of Agronomically
Important Crops, 23 Trends in Biotechnology 238-245 (2005); R. Fischer et al., Plant-
based Production of Biopharmaceuticals. 7 Current Opinion in Plant Biology 152-
158 (2004); R. Fischer et al., Plant-based Production of Biopharmaceuticals. 7 Current
Opinion in Plant Biology 152-158 (2004).
36 D. Gleba, Use of Plant Roots for Phytoremediation and Molecular Farming. 96 Pro-
ceedings of the National Academy of Sciences 5973-5977 (1999); S. Marillonnet et al.,
In Plant Engineering of Viral RNA Replicons: Efficient Assembly by Recombination
of DNA Modules Delivered by Agrobacterium. 101 PNAS 6852-6857 (2004).
37 The yield of 80 percent of TSP was achieved using a production system that is not
intended for open field cultivation. It nevertheless shows what is technically feasible at
present. For open field cultivation, yields of 10 to 35 percent might be more realistic -
but might also be optimized as technology improves. See A. Sp ok, Presentation in
the course of the IPTS Workshop 'Molecular farming in plants - opportunities and
challenges': Molecular Farming, Environmental Health Aspects and Coexistence with
Conventional Crop Plants (June 19, 2006).