New asthma treatment gets US go-ahead

Critical Therapeutics today kicked off the nationwide launch of Zyflo CR (zileuton), an extended release version of zileuton developed by UK firm Skye Pharma. The controlled release formulation offers a twice daily dosing regimen, providing a more convenient option for the prevention and chronic treatment of asthma in adults and children over 12 years than the current four-times-a-day version of Zyflo. The launch today represents a significant addition to the companies' portfolios, building on the firm's immediate release version of the drug, which generated product sales of $5.2m over the first half of this year according to Critical Therapeutics' figures. A real boost to sales is likely to come thanks to a recent recommendation by the National Asthma Education and Prevention Program (NAEPP), which specifically named zileuton as a suggested therapeutic alternative for patients to help reduce asthma symptoms and prevent exacerbations. The mention of zileuton in the 2007 Guidelines for Diagnosis and Management of Asthma is the first time the drug has been separately recognized in the guidance since the formation of the NAEPP in 1989, and is likely to have some influence over the choices made by prescribers. This, coupled with the fact that Zyflo (both immediate and controlled release versions) is the only US Food and Drug Administration (FDA) approved leukotriene inhibitor for the prevention and chronic treatment of asthma, makes the product's position in the market look relatively strong. The drug itself is an oral inhibitor of the enzyme 5-lipoxygenase, working by blocking formation of leukotrienes and therefore controlling a key part of the inflammatory cascade that is the consequence of an allergic challenge. Zyflo is the latest drug to be given a makeover by Skye Pharma, applying its Geomatrix drug delivery technology to achieve a controlled release profile of the drug into the body. The controlled release is achieved by constructing a tablet made of two basic components, hydroxypropyl methycellulose (HPMC) and one or more barrier layers. The HPMC core contains the drug's active ingredient, and the combination of barrier layers control the surface area diffusion of the drug (or drugs) out of the core. The combination of layers, each with different rates of swelling, gelling and erosion, is responsible for the rate of drug release within the body. When first swallowed, for example, the drug concentration is high but the surface area low. As time progresses the core swells, and the surface area increases to make up for the decrease in drug concentration. According to Skye Pharma, one of the major benefits of the GeoMatrix technology is its ability to be easily incorporated into the production line. The firm claims that GeoMatrix tablets can manufactured by readily available equipment that can be integrated into widely-used pharmaceutical processes, thus giving firms more control over their own production activities. Zyflo CR, however, is due to be produced by Skye Pharma itself, manufacturing the product at its plant in Lyon, France. The company will receive a "high-mid single digit royalty​" on net sales of the controlled release product. Earlier this year Critical Therapeutics initiated a Phase IV trial to evaluate Zyflo CR as an add-on therapy to help boost sales and marketing efforts for the drug, and is also in the process of developing an injectable formulation of zileuton for use in the emergency room or other urgent care settings.