Update on biological therapies for critical limb ischemia.

Gene and stem cell therapies have been shown to be safe and well tolerated. Early trial results using these therapies have had promising results on important clinical end points such as wound healing, ischemic pain, and major amputation. Despite this, there have been no pivotal trials to date that have proved the benefit of biological therapy, although there are numerous pivotal trials in progress or about to initiate enrollment. Persistent obstacles exist with current study designs that complicate the ability to successfully perform clinical critical limb ischemia trials.