Plant-based expression systems expedite time to market

Leaf Expression Systems is a new contract development business specialising in the plant-based expression and production of proteins, metabolites and complex natural products for research and biomedical applications using a proprietary, transient expression technology. Dr Kevin Robinson recently caught up with Simon Saxby, Chief Executive Officer, to find out more

Leaf Expression Systems, based in the Norwich Research Park, UK, is a spinout from the John Innes Centre (JIC) and funded by JIC and Plant Bioscience Ltd as investors in the company.

“We’re almost 2 years old now and working in a brand new, fully operational facility with state-of-the-art equipment. Part of what we’re doing includes licencing some technology from the John Innes Centre called Hypertrans, which is essentially an expression system,” says Simon.

Originally developed by Professor George Lomonossoff at the John Innes Centre, Hypertrans is efficient, safe and simple to use to quickly produce proteins such as vaccines, antibodies or enzymes in the leaves of tobacco plants.

The proteins are then extracted and purified to give the desired product. The speed of the system means that it can rapidly produce large amounts of protein, so it’s well suited to rapidly responding to emergencies such as pandemics.

Other potential uses include producing many proteins at the same time and creating new biochemical pathways to produce complex bioactive molecules such as novel anticancer drugs and anti-infectives.

Adds Simon: “A key aim for Leaf is to help the pharmaceutical industry to look into alternative ways to produce drugs and vaccines, as well as other molecules and secondary metabolites that don’t necessarily express in other systems. We understand that the sector is under extreme pressure to deliver new drugs, improve patient outcomes and manage costs, which is an area we think we might be able to help with.”

“One of the early ideas and perhaps a key benefit of the technology is that we can respond very quickly to disease outbreaks, for example. We’re in a situation whereby using Hypertrans, we can actually generate vaccines on demand to address an emergency condition within weeks as opposed to months … to both tackle the immediate outbreak and give Big Pharma more time to come up with a more permanent solution. This has already been tested to some extent against Zika outbreaks and Ebola.”

Being such an obvious vehicle, why hasn’t it been done before? Although plant expression is considered to be more cost effective (20–30%) owing to the lower cost of upstream production (plant growth) when compared with other eukaryotic systems, the greater pharmaceutical industry has been reticent to adopt the technology.

In the late 1990s, with the development of stable transgenics, there was some progress, with the vision that companies could grow acres and acres of corn expressing their favourite antibody or protein and rapidly convert that into a therapeutic, for example. However, GMO issues and concerns pretty much halted commercial production. “Now, with the advent of new technologies, we’re not actually making transgenic plants; plus, it all happens very quickly compared with traditional farming-based practices — which can take years to get from lab to field,” notes Simon.

Protein expression is currently achieved after about 1 week, following infiltration for plant transient expression, which is much quicker than even culture-based systems that require weeks or months of cell culture expansion. Furthermore, plant expression can be scaled-up simply by growing more plants.

Scaling in other systems has limitations and issues are often encountered during this process. So, much has happened in the last 5–10 years, including the development of better expression systems that enable enhanced protein yields, etc.

Expediting time to market

A critical advantage is speed, explains Simon: “We can be turning around and handing product back to customers within a period of 12 weeks. And, because it’s directly scalable, once we know what the yields are, we know how many plants we need to grow to produce a certain amount of protein and can extrapolate that in terms of both scale and cost."

"From a very early stage, we can provide accurate financial estimates regarding the delivery of gram quantities of a product for clinical trial studies and beyond. Compared with mammalian or microbial systems, wherein scale-up can often be problematic, the benefits in terms of speed, simplicity, regulatory compliance and sheer predictability are substantial … not to mention that there are no animal-derived products involved.”

“As an emerging technology in terms of uptake by the life science sector, I’m sure we’re not alone and that, with time, we’ll have competition in the market. But, one of the things that strikes us is that there are a number of diseases for which making the product/therapeutic would be very difficult from a commercial viability point of view, just because patient numbers are so low."

"It’s an area that we’d like to investigate further because we can potentially produce those sorts of quantities relatively inexpensively and more efficiently to address some of those orphan drug and personalised medicine situations, for example, when traditional methods may struggle to deliver.”

Safe and effective

Intrigued by the possibility of producing highly potent anticancer drugs in plants, I ask Simon about containment issues and safety.

He explains: “At the moment, all production steps occur within the Leaf Expression Systems facility to maintain complete control. Our growth chambers have a computer-monitored system that ensures absolutely constant growing conditions; illumination, temperature and humidity are optimised to levels that ensure ideal growth conditions and maximal biomass and protein production."

"We’ve not yet experienced any containment issues and nothing leaves the building without being autoclaved … but if we end up having to bring toxic compounds into the facility — for assay purposes, for example — then operator and environmental safety will be paramount.”

“Generally speaking, what we’ll be doing is obtaining a (genetic) sequence and inserting that sequence into a bacterium to infiltrate a plant, so I envision a very safe handling process for the upstream work. When we harvest the plants, the leaves are collected, transferred to a blender to extract the required compound and the subsequent steps (purification) are very similar — if not identical — to more established technologies such as those used to process an antibody. We’re not actually adding anything different or more complicated to the procedure compared with normal cell breakage techniques.”

I suggest to Simon that the technology isn’t limited to a single industry and could be applied to food, biotechnology or nutraceutical platforms, for instance.

“Absolutely,” he confirms: “We have some ongoing internal programmes looking at diagnostic applications and the nutra space is very much an opportunity."

"In Asia, for example, extracting food-relevant molecules and nutraceutical moieties is big business — albeit not using Leaf technologies — but it’s very relevant to our production model. What we have to do right now, though, is focus on establishing the business and generating some profits before expanding into other areas.”

Open for business

Currently, Leaf has both grant-funded and commercially supported projects under way, but it’s an area that the company is very much looking to develop.

“We’re in recruitment mode right now and we’ll be adding a dedicated business development person as soon as possible; we’re also reaching out to the industry — to diagnostic, biotech and Big Pharma companies — to promote our technology and the service we provide. In terms of where we would like to be in the next 2–3 years, we’re aiming to be self-funded, profitable and with an order book that prompts us to look at expanding or selling the business to be able to satisfy customer demand,” says Simon.

“On top of that, we’re always on the lookout for potential strategic alliances with other players in the market who might be able to offer something complementary to our current proposition. Very much, we want to build Leaf as a commercial enterprise, get industry recognition for what is now considered to be a disruptive approach to production and, ultimately, address unmet patient needs.”

As a conservative industry, I ask Simon how well Big pharma has taken to the concept of plants as bioreactors.

“There is indeed some conservatism,” acknowledges Simon, “possibly driven by the regulatory bodies; but, having said that, many agencies are very open to the use of plant-based systems to manufacture pharmaceuticals and critical diagnostics. Any product, however it’s produced, has to meet the same criteria of quality, safety and efficacy.”

Simon Saxby

“It’s been interesting for me because I’ve been aware of people producing proteins and antibodies in plants for 20–25 years or more … but I’ve found almost polar opposite views in the marketplace; some are aware of it and interested, whereas others are completely oblivious!"

"We now have an opportunity to educate and convince the more conformist elements and, at the same time, present something that’s novel and exciting. In terms of Big Pharma and large biotech companies, we want to attract their attention because of the fast throughput that Hypertrans offers; it’s ideal for research and development (R&D) applications, so products going into clinical trials are perfect candidates.”

“It also supports the fail fast principle for potential drug candidates. We can quickly provide adequate quantities to conduct initial studies with and enable sponsor organisations to make critical decisions regarding which actives to terminate and which ones to proceed with. Our system is significantly more cost-effective than established methods and extant mammalian or microbial systems, facilitating R&D throughput and accelerating novel drugs both into the clinic and, eventually, the market.”

He adds: “Not to mention patent life and return on investment for pharmaceutical companies. If, for example, a drug generates annual revenues of $365 million, then every day that we get that drug into the market earlier represents $1 million, which is a pretty convincing argument.”

In conclusion, Simon summarises: “Leaf’s revolutionary Hypertrans technology offers a solution to the significant financial pressures being experienced by the global life sciences industry to lower the costs of new diagnostics and therapeutics by providing an innovative way of rapidly and cost-effectively producing proteins, vaccines and complex biomolecules."

"Our goal is now to establish Leaf Expression Systems as a partner of choice by adding real value to the research and development programmes of our clients across the globe.”