The Omnitrope Pen 5 with liquid cartridge offers somatropin 5mg pre-dissolved in a ready-to-use cartridge that can be loaded into the pen for injection. The existing version of Omnitrope launched by Sandoz in the US in January 2007 is in lyophilised powder form, which has to be reconstituted by mixing it with bacteriostatic water containing benzyl alcohol as a preservative. As well as presenting a more convenient delivery system for patients, the Omnitrope Pen 5 with liquid cartridge is priced at $33.65 per mg, around 35 per cent below the published price for the reference brand, Pfizer's Genotropin, and other leading recombinant growth hormones, Sandoz noted. Bernhard Hampel, chief executive of the US subsidiary Sandoz Inc, said the launch of the Pen 5 with liquid cartridge formulation was "another milestone in our continuing efforts to provide US healthcare providers and patients with greater access to high-quality biologic medicines at more affordable prices". Omnitrope was famously the first follow-on version of a previously approved recombinant biotech drug to be approved by the Food and Drug Administration (FDA), a decision that came after a good deal of legal wrangling as the FDA dragged its feet in the absence of a formal approval pathway for biogenerics in the US. That debate is still going on but Omnitrope was approved as an exception under the Section 505 (b) (2) provisions of the Hatch-Waxman Act, designed for versions of marketed drugs that are not exactly identical to the original. The Pen 5 injector device is manufactured for Sandoz by Becton Dickinson. There was little more information available on the device and how it may differ from the delivery system used for the lyophilised powder formulation. In Australia, where Omnitrope was approved on the basis of a full application to the country's Therapeutic Goods Administration in September 2004, the drug was originally launched in a ready-to-use liquid formulation together with the Pen 5 device in November 2005. At that time, Sandoz described the Pen 5 as a "light, easy to use" pen system that could deliver doses from as low as 0.05mg up to 2.7mg. Once inserted into the pen, each cartridge containing 5.0mg/1.5mL of somatropin had a shelf life of 21 days, the company added. Asked why Sandoz had not debuted with the more convenient liquid/Pen 5 formulation in the US and Europe, Charles Bruns, director of communications for Sandoz, said the "regulatory pathways are different in Australia, Europe and the US. Therefore, different approval times are likely". In Europe, the version of Omnitrope that eventually secured final approval (on the basis of a second application) in April 2006 - making it the first product to negotiate successfully the EU's new regulatory pathway for biosimilars - was also the lyophilised powder format. An Omnitrope liquid pen system has been available in Europe since the spring of 2007. This is listed as the Omnitrope 5 Pen used to deliver a liquid formulation in glass cartridges of Omnitrope 1.3mg/ml and 5.0mg/ml. Later last year, Sandoz extended that range to include a higher-strength (6.7mg/ml) formulation for use with the Omnitrope 10 Pen device. Bruns would not be drawn on whether Sandoz intends to launch this higher-strength liquid formulation and the Pen 10 device in the US, nor did he have any comment on how sales of Omnitrope have been affected by the launch of ready-to-use formulations in Europe. Presenting its annual results in January, Sandoz mentioned only that there was a "steady and sustainable increase" in the patient pool for Omnitrope. Last year, though, IMS Health said Omnitrope had captured less than 1 per cent of the US$831 million European market for human growth hormone. And Sandoz has admitted itself that Omnitrope made a slow start in a challenging US market. According to Bruns, the lyophilised formulation has not been a hindrance to US sales of Omnitrope. It was just a "very competitive market" and Sandoz had tried to come up with a delivery system that would make the drug easier to use, he said. "Certainly we think [the Pen 5 liquid presentation] will make the product more accessible to patients," Bruns commented.