A patient who became ill following two experimental gene therapy injections for arthritis has died and U.S. health regulators are investigating the cause, officials said on Thursday.

The gene therapy trial by Targeted Genetics Corp. was placed on hold before the death, after the patient suffered a serious, unidentified health problem.

The hold means that no one else can receive the treatment, called tgAAC94, and no new patients can be enrolled in the study, the Food and Drug Administration said.

The company and the FDA said they were working to determine the cause of the death. The investigation into the cause of the patient's illness and subsequent death is intensive and ongoing, an FDA statement said.

The incident will be discussed at a September meeting of a National Institutes of Health advisory panel, the FDA said.

Gene therapy aims to replace a faulty gene with a healthy one. Often a virus is used to carry a new gene into cells.

Scientists have touted gene therapy as holding great promise for a range of ailments, but safety problems have set the field back. One experiment cured two French bubble boys with a rare immune disorder, but later gave them leukemia, and an Arizona teenager died in a 1999 gene therapy experiment.

The Targeted Genetics product was injected directly to affected joints of patients with inflammatory arthritis.

The company used an adeno-associated virus (AAV) to deliver a gene with the aim of suppressing inflammation. Adenoviruses are a group that typically cause respiratory illnesses such as colds.

Targeted Genetics Chief Executive Stewart Parker said in a statement the clinical course that this individual experienced has, to our knowledge, never been seen as a consequence of exposure to adeno-associated viral (AAV) vectors or naturally occurring AAV.

The FDA said it was not aware of any similar problems in other gene therapy trials but, as a precaution, was reviewing all ongoing trials that used the AAV delivery method.

Targeted Genetics said patients who have already enrolled in the study will continue to be monitored.

Since the trial began in October 2005, as many as 127 patients have received an initial dose of the active treatment or placebo. Some received two doses of the active drug, the company said.

(Additional reporting by Varsha Tickoo in Bangalore)

Medicine Arizona