One of the major safety issues with gene therapies is integration of foreign DNA into the germline of patients, where it would cause problems in future generations. Using a test that is much more sensitive than previously used PCR tests, Avigen Inc. has detected vector DNA in the semen of the first patient given a hepatic artery infusion of its Coagulin B. But while a more sensitive test increases confidence in safety, the clinical implications of the results are not completely clear.

As a result of the finding announced last week, AVGN suspended a Phase I/II trial of its Coagulin B adeno-associated virus vector carrying a gene for human clotting Factor IX in hemophilia B patients.