Following a few months' experience as a pilot scheme, the monthly rental plan will now operate for the rest of 2008 in the European Union and North America, subject to the availability of stock units for rental. According to Cellexus commercial director Dr Ian Taylor, some 30-40 per cent of orders by volume for the CellMaker Lite2 fermentor in the fourth quarter of 2007 were for rental. Cellexus launched the system, an upgrade on its first-generation disposable bioreactor, last May. New additions included a much smaller footprint (60 per cent less than the previous model) as well as the ability to deliver gases to the aeration mechanism in the base of the disposable cell culture bag and the surface area above the cell culture (the headspace) independently of each other. Another novelty is that CellMaker Lite2 does not rely on the traditional method of physical agitation of the media to supply oxygen to cells. According to Cellexus, the conventional approach can lead to cell damage or ineffective oxygenation, and in turn lower yields. As the company notes, disposable bioreactors and attachments are becoming an increasingly desirable proposition, with their promise to reduce the risk of cross-contamination between cell culture batches while minimising turnaround time, cleaning costs and validations. In the case of CellMaker Lite2 (for bacteria and yeast cells) and CellMaker PLUS (mammalian and insect cells as well as bacteria and yeast), the range extension launched by Cellexus last September, the single-use element is the medical-grade bag in which the cells are cultured. The company now offers two variants on this technology: the CellexusBag for bacteria and yeast cells and the HybridBag (introduced alongside the Cellmaker PLUS last September) for bacteria, yeast, mammalian and insect cells. The monthly rental plan for CellMaker Lite2 includes a supply of CellexusBags as well as full service and warranty delivered by local support personnel from Cellexus or its sales partners. Two plans are available based on the size of the CellMaker enclosure, but both at the same monthly cost of $2,000. The 1-8 litre CellMaker Lite2 system comes with three 8L CellexusBags per month - "about par" for bacterial cell growth, Dr Taylor said. The 10-50 litre system is supplied with one CellexusBag per month, on the assumption that a larger enclosure means fewer production runs. Any additional bags have to be purchased separately at the standard price. While a rental plan with monthly payments is an aid to customers' cash flow, it also provides "a low-risk mechanism for them to evaluate disposable technology for growing their particular cells, allowing customers to assess and approve the CellMaker technology before committing to a final purchase", Dr Taylor said. Without a great deal of data available to measure performance, he told In-PharmaTechnologist.com, renting is a means to "try before you buy in a very controlled way". Some customers are taking the CellMaker Lite2 on rental for the full 12-month contract term while others are converting to purchase after three months, Dr Taylor added, noting that a portion of the rental payment is then offset against the capital costs. According to company spokesperson Jessica Auton, sales of the CellMaker Lite2 have seen a "real upturn" in the US market in particular, where a subsidiary, Cellexus Biosystems Inc, was incorporated in Delaware in February 2007. In its interim results announcement last September, Cellexus said 50% of sales overall during the first half of 2007 were to customers in the US, while 30% were to UK and 19% to European customers. The rental plan has "gone down extremely well" in the US market, Auton told In-PharmaTechnologist.com, with a number of customers extending their rental periods. The arrangement gives clients "a good three months to play around with the system", she commented. Trying out new technology such as the CellMaker Lite2 on a one-off basis "doesn't really give a good feel" for the system as there are so many variables to optimise, she pointed out. According to Auton, the rental plan has already been extended to the CellmakerPlus system for a couple of clients.