Shire has extended its relationship with transdermal patch specialist Noven Pharmaceuticals, fronting a $5.9m milestone payment to the firm after deciding to proceed with the clinical development of an amphetamine-based patch. Last year Shire launched Daytrana, a methylphenidate-based patch and the first and only transdermal product to be approved for ADHD therapy. According to the original contract, Shire also had the option to move forward with an amphetamine-based patch, and following the completion of a Phase I trial of the product earlier this year, the company has exercised its right to proceed with clinical development. The decision means that Shire will pay for the remaining clinical development, as well as additional modifications to Noven's existing patch formulation in order to align the product with Shire's future direction in ADHD. If the company had decided against bringing the amphetamine product into its catalogue, Noven would have simply retained the rights to the product and continued development itself. According to Noven, amphetamine products represent about half the US market for stimulant ADHD therapies, and a patch product could bring significant advantages to patients and enhance compliance. By choosing to take on the amphetamine patch, Shire "may be in a position to extend its portfolio to include a patch in each of the two largest market segments in ADHD therapy," according to Noven. Noven has already seen a significant impact on its earnings since the methylphenidate patch, Daytrana, was launched in late June last year. The Daytrana product sales to Shire for 2006 were $8.6m, with $5.9m recognized in related license revenues. The product itself is based on Noven's proprietary DOT Matrix transdermal technology, which the company claims has significant advantages over standard patch products. The system uses a patented multiple adhesive mix of silicone, acrylic and the required drug so that the drug is mixed in with the adhesive that holds the patch on the skin. Each patch is a thin, three-layer laminate made up of the patch backing, the drug/adhesive mix and the release liner (the part that gets peeled off and thrown away once the patch is applied). The patches themselves are compatible with a wide range of medications, and as they deliver the drug more effectively than other competing products they tend to be smaller than other transdermal systems. In addition to this, the patches use one adhesive to hold the drug, and another to make the patch stick to the skin, resulting in superior adhesion to the skin. The Noven transdermal system is already in use in other products beyond Shire's ADHD patch, including DentiPatch (a transmucosal patch for dental pain), Vivelle-Dot (the world's smallest transdermal estrogen patch), and a number of other hormone therapy patches. Transdermal drug delivery is growing market, offering advantages in terms of consumer-friendliness, increased patient compliance and a compelling option for companies looking for line- of life-extension strategies for their products. With Shire's already established position in the ADHD market, this latest potential addition to its catalogue can do the company no harm, and as Noven itself noted could open access to significant revenue stream through additional patch products.