A clinical trial for an investigational arthritis drug has been put on hold after a subject in the trial, a bodybuilding father of three with no history of heart problems, suffered two heart attacks and died, the company developing the drug announced today (July 8).

Peter Munro, 48, was participating in a Phase 1 trial for RhuDex, a compound that blocks T-cell activation to prevent inflammation in rheumatoid arthritis, at a clinic outside of Edinburgh. After suffering cardiac arrest just over a week ago, Munro was recovering at home on Saturday when he had another attack and died.

Munro was in good health, and "only took part in the trials to clear his debts," his sister told The Times. The family is calling for the clinic to be closed.

RhuDex has so far been tested in 80 individuals in both Phase 1 and Phase 2 trials, and no others have fallen ill, according to today's release by MediGene, the German biotech company developing the drug. The release states that "no signs of cardiac effects due to RhuDex" were observed in preclinical studies. The company's website hails RhuDex as a "blockbuster drug candidate" with an "estimated annual sales potential of more than 1 billion."

An autopsy is being performed to determine the cause of Munro's death, but the event raises fresh concerns over the safety of clinical trials. Last year, a patient died in a phase I/II gene therapy trial for inflammatory arthritis, though an investigation attributed the death to a fungal infection and not the therapy. A year earlier, six healthy trial participants became seriously ill, including losing fingers and toes, after taking a monoclonal antibody designed to treat immune disease and leukemia. In that case, an investigation placed blame on an "unpredictable biological action" of the drug.