Stem cell transplants show potential in patients with extremely rare brain disease

StemCells ($STEM) has shed light on follow-up data from a study of four patients with a genetic neurological disease who got transplanted stem cells in their brains, with evidence of greater production of a missing neuronal myelin sheath.

Like most potential stem cell therapies, StemCells' have made slow progress in clinical development. The Newark, CA-based company's two-year follow-up data come from its Phase I study of four patients with Pelizaeus-Merzbacher disease (PMD) completed in February 2012, and the company has yet to strike an agreement with the FDA on meaningful measures for further clinical development of the treatment.

In October 2012 the company highlighted one-year data from the study that was published in Science Translational Medicine. After two years, MRIs of study subjects show more "pronounced" creation of myelin in study subjects compared the level of so-called myelination after one year. The patients maintained improvements in neurological function at two years as compared with results from one year after they received donated neuronal stem cells in their brains. Yet the study lacks control patients, making it difficult to say how much of a benefit the therapy really provided.

"Even in the context of a small open-label study, these MRI results, measured at time points long after transplantation, make an even more convincing case that the HuCNS-SC cells are biologically active and that their effect is measurable, sustainable and progressive," said Stephen Huhn, StemCells' vice president of CNS clinical research. "Our challenge now is to reach agreement with the FDA on how best to correlate changes in MRI with meaningful clinical benefit, as this will be a critical step in determining a viable registration pathway for PMD." 

Most PMD patients have a genetic defect that robs their brains of the ability to produce myelin, the protective sheath around neurons that helps maintain healthy transmission of nerve signals. This leads to loss of motor function and eventual death. The disease afflicts one in 200,000 to 500,000 people, qualifying it as an ultra rare disorder.

StemCells has initially tested its experimental HuCNS-SC cells in patients with PMD and another rare ailment known as neuronal ceroid lipofuscinosis, with the hope of eventually expanding the approach to treat more common myelin disorders such as multiple sclerosis and cerebral palsy.

Yet the company faces many hurdles in larger clinical studies to prove that its stem cell approach really works. The company had a market value of $63.39 million after trading ended on Thursday, which is far lower than those of companies such as Sarepta ($SRPT) and Alnylam ($ALNY) that have provided greater evidence in clinical trials that their experimental genetic drugs could benefit patients.

- here's the press release