Back in July, a Phase I/II study was halted after patient Jolee Mohr died from a fungal infection called histoplasmosis while testing the Seattle-based firm's lead drug, tgAAC94. Although the full findings of the FDA aren't due to be made public until 3 December, Targeted Genetics has now said it has received permission from the regulators to finish the trial.

The therapy uses an adenovirus to deliver the gene for tumour necrosis factor alpha (

TNF-alpha) receptor in order to inhibit the immune stimulating activity of the protein. It was designed to supplement other immunosuppressant therapies that block TNF-alpha, only instead of being given systemically like those rival drugs, tgAAC94 is injected only into the diseased joint.

Earlier, the company had said that only trace amounts of the viral vector were found outside the joint and it was "unlikely that tgAAC94 contributed to the conditions that caused the death".

"The level of vector that is present outside the locally treated area is insufficient to have further exacerbated an infection," said H. Stewart Parker, CEO of Targeted Genetics, a month ago after the US National Institutes of Health (NIH) Recombinant DNA Advisory Committee (RAC) conducted a public hearing into the case.

Targeted Genetics will encompass suggestions made by the FDA and its independent data safety monitoring board into a revised trial protocol.

The 35 patients who have not yet received their second dose of tgAAC94 will be shown an updated consent form, which includes information about Mohr's death and patients will not be allowed to receive the treatment if they are suffering from a fever at the time of injection, as Mohr was.

"We are working closely with trial site physicians to ensure we resume development in the most efficient manner possible with patient safety, as always, of paramount importance," Parker said today.

Whether or not the revised protocol also addresses efficacy concerns is, as yet, unclear. The original trial design has been widely lambasted in the media because patients already taking TNF-alpha blocking medications are not excluded. As such, many believe it could be difficult for Targeted Genetics to prove that it is their gene therapy having a positive effect, rather than one of these other drugs.

Ironically, it is also these other drugs that the firm is keen to point out could have had an effect on Mohr's health. She was also taking Abbott's TNF blocker Humira (adalimumab), methotrexate and prednisone.

"[These] are known to be immunosuppressive and a risk factor for histoplasma infection," the company said in a statement.

In the meantime, Parker said the company hope to have full data from the trial in the second half of next year but that it believes it already has enough data to simultaneously plan a Phase II trial to start at that time.