PEG interferon-&agr;-2a (RO 253036, PegasysTM, PEG IFN-&agr;-2a) is a polyethylene glycol (PEG)-modified recombinant human interferon (IFN) developed by Roche using a pegylation process developed by Shearwater Polymers. The process involves attaching one or more hair-like strands of an inert, synthetic polymer to anothermolecule. The PEG attachment encircles the protein and disguises it from the human metabolic system. PEG IFN-&agr;-2a has been designed to avoid some of the problems associated with the short t½ of traditional IFN-&agr;. A short t½ may give the hepatitis C virus the opportunity to recover, replicate and generate resistant forms during the trough periods.Shearwater Polymers has a license agreement with Roche for the PEGylation of IFN-&agr;-2a. This agreement provides Shearwater with up-front payments, rights to manufacture the PEG reagent and a share of downstream revenues.PEG IFN-&agr;-2a is in a phase II trial in noncirrhotic patients, a pivotal phase II study in cirrhotic patients, a phase III study comparing IFN-&agr;-2a to standard dose IFN-&agr; and a phase III study comparing IFN-&agr;-2a to an induction regimen of standard IFN-&agr;. Clinical trials of PEG IFN-&agr;-2a in combination with ribavirin are also in progress. Preliminary results from clinical trials indicate PEG IFN-&agr; may be associated with less toxicity and similar efficacy to IFN-&agr; and ribavirin combination therapy (RebetronTM). It is also being investigated preclinically as an anticancer agent in Switzerland.Weston-Medical, a UK-based drug delivery development company have developed a needle-free injector technology for subcutaneous delivery, Intraject®, which is to be used for the delivery of PEG IFN-&agr;-2a.Enzon filed a patent infringement suit against Shearwater concerning the pegylation technology in December 1998 and litigation is ongoing. Roche have filed for a patent for PEG IFN-&agr;-2a.