A laboratory study in Germany suggests that a drug now being tested for treating the common cold could be modified to treat SARS (search), a respiratory virus that has killed at least 577 people worldwide, and which has no known treatment.

In a study appearing this week in the journal Science, German virus researchers say they have tentatively determined the structure of a key protein used by the SARS virus to infect cells and believe that the virus would be vulnerable to treatment by a modified version of an experimental common cold drug called AG7088 (search).

AG7088 is currently in clinical trials for the treatment of rhinovirus, a pathogen that can cause the common cold, according to experts at the journal Science.

Rolf Hilgenfeld of the University of Luebeck (search) in Germany, senior author of the study, said he and his co-authors have developed a model for an enzyme that the SARS virus uses to infect cells. Based on this model, Hilgenfeld said in a statement that AG7088 provides "a good starting point" for developing a drug that will block the ability of the SARS virus to reproduce.

The enzyme, called a protease, is typical of proteins that viruses use to take over a host cell and force that cell to make new virus particles, thus spreading the infection throughout the body. Blocking the protease action would not prevent an initial infection, experts say, but it would prevent the spread of the virus.

Hilgenfeld said the researchers found close similarities between the protease enzyme of rhinovirus and the protein in SARS, which is a type of coronavirus.

Since AG7088 is effective against rhinovirus, he said, then a modified version of the drug might inhibit the action of the SARS virus enzyme.