Molecular pharming in plants and plant cell cultures: a great future ahead?

Abstract

Plant biotechnology may not be a familiar concept to the general public, but it is a rapidly developing field of research that involves the use of plants, plant tissues and plant cell cultures to make or modify products and processes. The versatility of plants and plant cells can be harnessed to produce diverse products, including valuable proteins. This is often described as ‘molecular farming’ and it requires the introduction of foreign DNA into plants or plant cells, turning them into factories for the production of specific recombinant protein products. The term ‘molecular pharming’ is often used instead to highlight the production of protein-based biopharmaceuticals, which contributes to the sustainable production of drugs that promote human and animal wellbeing. Both terms also apply to the production of valuable secondary metabolites such as the anticancer drugs paclitaxel, vincristine and vinblastine, but we will focus on recombinant proteins and their use as biopharmaceuticals in this article. The biopharmaceutical markets have expanded rapidly over the last 20 years, and are projected to more than double in volume over the next decade from US$200 billion in 2013 to at least US$500 billion in 2020. The two major biopharmaceutical production systems are microbes (mainly Escherichia coli and yeast) and mammalian cells such as the Chinese hamster ovary platform. In both cases, productivity has increased substantially over the last decade due to process optimization, platform standardization and genetic improvements. Both the US FDA and European Medicines Agency are familiar with these systems, and standard protocols can be followed to ensure the approval of new products. However, equivalent protocols are only just emerging for plant-based production systems, and only one plant-derived biopharmaceutical protein is currently on the market. With their established production infrastructure and regulatory framework, microbial and mammalian production systems have raced far ahead of their plant-based counterparts. No company will change their production host without a clear economic benefit, nor will they consider plants and plant cells for new products if there is no advantage over their incumbent technology. Furthermore, new companies will not base their manufacturing on a second-best option. Therefore, plant-based systems must begin to compete head-to-head with the established systems and, on a technological basis, we can already identify the areas where plantbased systems have the advantage, namely in terms of speed, improved product quality and scalability. The international success story of molecular pharming began in 2006 with the US Department of Agriculture approval of a poultry vaccine against Newcastle disease developed by Dow AgroSciences (IN, USA) [1,2]. The vaccine was manufactured in transgenic tobacco cell suspension cultures and was a benchmark for the regulatory acceptance of plants as a manufacturing platform, Molecular pharming in plants and plant cell cultures: a great future ahead?