THE initial trial of a controversial method for treating spinal cord injuries within two weeks of an accident suggests it may be partly successful. More patients recovered some sensation and movement than would normally be expected, the company behind the trial claims. Independent experts say the results look promising, but caution that with just 16 people treated so far, it is too early to draw any conclusions. Some worry that the technique is risky and could cause serious problems in the long term. The method involves extracting immune cells from a patient’s blood, “activating” them by incubating them with skin cells, and then injecting the cells directly into the damaged spinal cord. This must all be done within 14 days of the injury, so even if larger trials confirm its benefits, the method will not help the hundreds of thousands of people worldwide with existing injuries.
The technique is being developed by ProNeuron Biotechnologies of Los Angeles, which has just submitted results from the first 10 patients for publication. All patients fell into the most severe spinal injury category, called ASIA-A. This is defined as having no sensation or ability to move below the site of injury.
Normal sensation and movement is defined as ASIA-E. According to David Snyder, vice-president of clinical development at ProNeuron, three of the 16 patients treated so far (19 per cent) have recovered some weak muscle function, which means they are now classed ASIA-C. One has regained bladder control, while another can stand and walk with assistance. This degree of recovery can occur spontaneously, but Snyder says less than 4 per cent of patients normally recover from ASIA-A to C. Two other patients (13 per cent) have regained some sensation, and are now classed as ASIA-B. About 10 per cent of patients normally recover to ASIA-B. Four other patients show signs that nerve signals can pass through the injury site, though as yet they have no significant Functional recovery. Snyder describes the results as a good start.
Most importantly for a phase I trial, which is designed to assess safety rather than effectiveness, he says there were no signs of any ill effects. On the basis of the results, ProNeuron announced this week that phase II trials will go ahead in the US. It aims to recruit 61 patients within the year. “The early data is encouraging,” says Phillip Popovich of Ohio State University in Columbus. But since there was no control group, the improvements could just be a result of the emotional boost the treatment gives patients, he points out.
The therapy is based on the work of Michal Schwartz of the Weizmann Institute of Science in Rehovot, Israel. Her theory is that one of the reasons for the poor healing of spinal injuries is that the Central Nervous System is partly isolated from the immune system. It takes months for immune cells called macrophages, which clean up damaged tissue and promote healing by releasing growth factors, to accumulate at a spinal injury site. Her animal studies suggested injecting the cells soon after the injury can help recovery (New Scientist, 4 July 1998, p 17). But many researchers remain unconvinced.
“Whether macrophages are damaging or beneficial is very controversial,” says Geoff Raisman, who works on spinal cord injury at the National Institute for Medical Research in London. There is even a risk that the treatment could make things worse, warns Mark Tuszynski at the University of California, San Diego. “This could hypothetically cause a loss of function in critically valuable tissue that is spared just above the Lesion,” he says.
Tuszynski would prefer to see the animal results replicated in an independent lab before being tried in humans. Although no patients have shown any signs of damage, it could occur much later, Popovich warns. Animal studies show that macrophages can remain at the injury site for years. An inflammatory reaction sparked by infection or surgery might damage any nerves that have recovered, he says.
Author: Helen Phillips
Contact: Claire Bowles