For most biologics, the manufacturer would have requested and got a patent term extension under 35 USC 156. The practical limit seems to be 14 yrs from date of approval. This would be an easy way of looking at upcoming expiry I guess. See <A HREF="http://www.fda.gov/ohrms/dockets/dockets/05e0254/05e-0254-app0001-01-vol.pdf" target="_blank">http://www.fda.gov/ohrms/dockets/dockets/05e0254/05e-0254-app0001-01-vol.pdf</A>