Tysabri was launched in the US in 2004 for the treatment of relapsing-remitting multiple sclerosis. It initially generated great excitement, being presented at this year's annual JP Morgan Healthcare Conference as "the next multi-billion dollar biotech blockbuster" that "could potentially transform the multiple sclerosis market". In March 2005, this excitement quickly evaporated when safety concerns, based on two cases of confirmed progressive multifocal leukoencephalopathy when administered in combination with Avonex, led to its voluntary withdrawal. Although administered as a single agent, Antisense Therapeutics has subsequently halted a Phase IIa trial of its antisense drug ATL-1102, as it also targets the VLA-4 immune system protein.

Analysis of Pharmaprojects data indicates an increase in the development of VLA-4 antagonists from 1995. However, since 2001, there has been a decline in the development of drugs targeting this protein (Figure 1: http://www.prnewswire.co.uk/media/pictures/3/1189293-3060968.jpg). Pharmaprojects reports 12 VLA-4 antagonists under development, with the majority under development for asthma. Of these 12, only five are in active development for multiple sclerosis. These include Tanabe Seiyaku's T-0047, in Phase II development for multiple sclerosis, and TR-14035, in Phase II trials for arthritis, asthma, multiple sclerosis and irritable bowel syndrome. Preclinical compounds include Schering-Plough's TBC-4746, with potential in asthma and multiple sclerosis, and a compound under development by Uriach.

Pharmaprojects has identified over 1375 individual protein drug targets, which are or have been under investigation since 1980. Precise drug targets have been assigned to 43% of drugs on the database, giving a decidedly detailed picture of the drug development strategies pursued over more than two decades. Searching for targets by complete or partial name or Entrez Gene ID number allows for easy access to all drugs acting on a specific target and is an invaluable tool for any company tracking pharmaceutical R&D or developing drugs against novel targets.

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