A team of scientists led by stem cell pioneer Professor Robert Lanza has reported today in the Lancet (1) the first evidence for the long-term safety of retinal pigment epithelial (RPE) cells derived from human embryonic stem cells (hESCs) in patients who took part in a trial undertaken in four centres in the US. substantial improvements in vision were also recorded in almost half the treated patients, compared to no improvement in untreated patients.

This is the first time that clinical benefits have been demonstrated in the medium to long term in patients with any disese treated with hESC-derived cells, and is a major milestone in the development of the field of regenerative medicine. It’s an achievement that is due to many years of animal research.

The trial focused on 18 patients with two different types of macular degeneration, Stargardt’s macular dystrophy and nine with dry atrophic age-related macular degeneration, that are common causes of blindness in adults and children and for which no effective treatments are currently available.

Nine patients with Stargardt’s macular dystrophy and nine with dry atrophic age-related macular degeneration received injections of 50,000 to 150,000 RPE cells behind the retina of their worst-affected eye. Robert Lanza, adjunct Professor at the Institute for Regenerative Medicine, Wake Forest University School of Medicine and Chief Scientific Officer at Advanced Cell Technology who funded the trial, describes the results:

The vision of most patients improved after transplantation of the cells. Overall, the vision of the patients improved by about three lines on the standard visual acuity chart, whereas the untreated fellow eyes did not show similar improvements in visual acuity. The patients also reported notable improvements in their general and peripheral vision, as well as in near and distance activities”

Professor Steven Shwartz, who led the team at the Jules Stein Eye Institute that took part in this trial, noted how important this result is to both the patients in this trial and the field of hESC-derived stem cell medicine.

Our results suggest the safety and promise of hESCs to alter progressive vision loss in people with degenerative diseases and mark an exciting step towards using hESC-derived stem cells as a safe source of cells for the treatment of various medical disorders requiring tissue repair or replacement,

You can listen to interviews with Steven Schwartz and several of the participants in this clinical trial in an NPR broadcast here.

In 2011 we discussed the launch of trials of these hESC-derived RPE cells, including some of those whose results are reported today, at Moorfields Eye Hospital in London and the Jules Stein Eye Institute at UCLA. A paper published in the Journal Stem Cells in 2009 showed how studies in rodent models retinal degerneration paved the way for these trials by demonstrating that RPE cells derived from hESCs were safe and could restore vision:

Assessments of safety and efficacy are crucial before human ESC (hESC) therapies can move into the clinic. Two important early potential hESC applications are the use of retinal pigment epithelium (RPE) for the treatment of age-related macular degeneration and Stargardt disease, an untreatable form of macular dystrophy that leads to early-onset blindness. Here we show long-term functional rescue using hESC-derived RPE in both the RCS rat and Elov14 mouse, which are animal models of retinal degeneration and Stargardt, respectively. Good Manufacturing Practice-compliant hESC-RPE survived subretinal transplantation in RCS rats for prolonged periods (>220 days). The cells sustained visual function and photoreceptor integrity in a dose-dependent fashion without teratoma formation or untoward pathological reactions. Near-normal functional measurements were recorded at >60 days survival in RCS rats. To further address safety concerns, a Good Laboratory Practice-compliant study was carried out in the NIH III immune-deficient mouse model. Long-term data (spanning the life of the animals) showed no gross or microscopic evidence of teratoma/tumor formation after subretinal hESC-RPE transplantation. These results suggest that hESCs could serve as a potentially safe and inexhaustible source of RPE for the efficacious treatment of a range of retinal degenerative diseases.”

This work – and earlier studies of RPE cells derived from ESCs – built on decades of basic stem cell research, starting with the pioneering work of Gail Martin, Matthew Kaufman and Martin Evans in mice, and the subsequent derivation of ESCs in macaques and then humans by James Thompson and colleagues at the university of Wisconsin- Madison.

Today’s announcement is a major milestone in regenerative medicine, and one that id justifiably being celebrated, but we should also remember the many years of careful research that has led up to this moment. As with many medical advances much of the early research on embryonic stem cells was undertaken without any immediate clinical application in mind, but it nevertheless created the knowledge that is now driving an important emerging field of medicine. This is a lesson we need to remember when we donate to charities, when we discuss the importance of research with others, and most of all when we go to the ballot box!

Paul Browne

1) Schwartz SD et al. “Human embryonic stem cell-derived retinal pigment epithelium in patients with age-related macular degeneration and Stargardt’s macular dystrophy: follow-up of two open-label phase 1/2 studies” Lancet published onlin3 15 October 2014. Link.

2) Lu B et al. “Long-term safety and function of RPE from human embryonic stem cells in preclinical models of macular degeneration.”

Stem Cells. 2009 Sep;27(9):2126-35. doi: 10.1002/stem.149.