Targeted Genetics will resume studying an experimental gene therapy for rheumatoid arthritis that was halted four months ago after a patient died. The FDA will permit the company to continue clinical trials on its lead drug candidate, tgAAC94, after determining the patient died from a fungal infection that wasn’t connected to the treatment, Bloomberg News reports.

The case renewed questions about the safety of gene therapy, although the FDA, meanwhile, has reviewed all 27 human studies in the US using the technique after the latest death was reported. As many as 35 patients are still eligible to get one more injection of the experimental product. The treatment involves the injection of viruses engineered to produce an immune-suppressing protein, which helps block the inflammation in joints.

“This is a vindication for the product, the company and for the field of gene therapy,” H. Stewart Parker, Targeted’ ceo, tells Bloomberg.

Jolee Mohr, of Taylorville, Ill., died July 24, about three weeks after getting trillions of the genetically engineered viruses injected into her right knee as part of an experiment sponsored by Targeted Genetics. She first became ill the day she got that injection, eventually dying of a fungal infection and massive internal bleeding, The Washington Post reminds us.

But investigations by company scientists, a National Institutes of Health expert panel and docs at the University of Chicago, where Mohr was transferred before she died, found no evidence that the treatment was at fault. Kyle Hogarth, an intensive-care unit physician at the University of Chicago who cared for Mohr and was involved in the investigation, tells the Post that he feels reasonably certain that the treatment did not kill her.

But he is still bothered by the study’s design, because it allows participants to keep taking prescription meds that can’t be distinguished from the immune-suppressing protein made by the treatment’s gene-modified viruses. That makes it impossible to fully sort out whether problems that arise during the experiment may be caused by the treatment or the drugs the subjects are taking, he tells the Post.

“I think they have a horrible design,” Hogarth says. “It muddies the picture.”

Hogarth also echoed a concern raised by others in the course of the investigation: that Mohr was recruited into the study by her personal physician, who stood to profit from each new patient he enrolled. Medical ethicists have criticized such arrangements as posing a potential conflict of interest.

Robb Mohr, Jolee Mohr’s widower, was unaware that the company had gained permission to resume the study. “It seems weird that they are allowing it to go ahead, especially on patients who are already taking immune-system drugs,” Mohr tells the Post. “To me, it is reckless experimentation.”

He and his lawyers haven’t yet had substantive talks with Targeted Genetics, pending the release of results from the NIH investigation. Those results, which are to be made public at a meeting a week from today, conclude that the engineered viruses do not appear to have replicated in Mohr’s body - an initial concern.

A Targeted Genetics spokeswoman tells the paper that the protocol for the experiment has been changed. From now on, she says, participants won’t be allowed to get an injection of the experimental product if they have a fever, as Jolee Mohr did the day she got her shot.