The first European guidelines on crop pharming — growing transgenic plants to produce drugs — were published on 7 August, clearing an obstacle to commercial development.

The guidance was drawn up by the European Food Safety Authority in Parma, Italy, which will assess applications from scientists hoping to grow drug-producing plants on a commercial scale. The European Commission and member states will have the final say on all such plans.

Developers must detail the differences between the modified plant and the conventional crop, assess the risks of genes being passed on to other plants, consider the potential dangers to humans and animals and specify monitoring procedures. This is consistent with rules set out by the US Food and Drug Administration and the US Department of Agriculture, says Jeffrey Wolt, an expert in plant biotechnology risk assessment at Iowa State University in Ames.

Internationally, only a handful of clinical trials of plant-pharmed drugs are under way (see Nature 458, 951; 2009), and there are none on the market.