ViroPharma chief executive officer Vincent Milano did not return a phone message seeking comment.
Spokesmen from Sanofi, Shire, and Goldman Sachs declined comment.
Sanofi is based in Paris, and its U.S. headquarters is in Bridgewater, N.J., and it has research facilities in Malvern and Swiftwater.
Shire is headquartered in Ireland and one of its main U.S. offices is in Chesterbrook.
ViroPharma began operations in December 1994. According to its 2012 annual report, the company had 410 employees worldwide as of Dec. 31, with 265 in the United States and 139 in Europe. At an investor conference Wednesday, company officials said they hired eight more sales representatives in January.
ViroPharma's second-quarter revenue rose from $94.6 million in 2012 to $103.7 million for the same period this year.
There have been bumps in the road to greater profits. A recent clinical study on a new formation of Cinryze was stopped because of the unexpected incidence of antibodies in patients in the study.
ViroPharma has used the Dutch manufacturer Sanquin to produce Cinryze. Sanquin got a warning letter from the U.S. Food and Drug Administration dated Aug. 28 regarding processes at a factory in the Netherlands.
The stock started the day at $30.21 and reached a 52-week high of $39.56 before closing at $39.13 on the Nasdaq Stock Exchange.
Contact David Sell at 215-854-4506, firstname.lastname@example.org, or @phillypharma. Read his blog at www.inquirer.com/phillypharma.