The second-ever clinical trial of a therapy involving the use of human embryonic stem cells has received the green light from US regulators.
The company developing the therapy, Advanced Cell Technology (ACT), based in Marlborough, Massachusetts, got the go-ahead from the US Food and Drug Administration on 18 November, according to Robert Lanza, ACT’s chief scientific officer. ACT first requested approval from the agency to conduct the clinical trial a year ago.
The trial will examine the safety of a therapy for Stargardt’s Macular Degeneration, an inherited juvenile eye disease affecting an estimated 1 in 10,000 young people in the US. As the disease progresses, a layer of the retina called the retinal pigment epithelium (RPE) degenerates, causing vision loss. It’s hoped the new therapy would also work for other types of macular degeneration, a widespread cause of blindness, particularly in the elderly.
The treatment involves replacing diseased RPE cells with healthy ones generated from human embryonic stem cells, and hinges on a technique the company developed to create extremely pure concoctions of the cells. In the trial, 12 individuals at several US medical centres will receive injections of the cells directly into the eye to test the safety of the procedure. (Although the disease begins to take its toll at around 6 years of age, the trial will start with patients who are over 18.)
In a rat model, the group showed that the treatment could extensively rescue photoreceptors, thereby improving vision. “We’re hoping to see a similar rescue effect in humans,” Lanza says.
Macular degeneration has been seen as stem cell therapy’s low-hanging fruit because the cells that need replacing are so accessible, both for delivering the treatment and for monitoring its effects. The eye is also an immune-privileged site – meaning that injections won’t elicit an immune response. Last year, the pharmaceutical giant Pfizer agreed to back the work of researchers at University College, London, who are developing a similar therapy.
Just one other trial for a human embryonic stem cell-based therapy — developed by Geron, a stem cell company based in Menlo Park, California, to treat spinal cord injury — is currently underway. That trial first gained approval in January 2009, but was halted due to safety concerns. It was cleared to restart this summer, and its first patient received the treatment in October.
Lanza says ACT’s macular degeneration trial is likely to be significantly more straightforward. “The advantage, of course, is that we’re talking about a very small number of cells going into a very local area,” he says. Using instruments that can track a single retinal cell in the eye in real time, the researchers will also be able to easily monitor patients’ progress.
“Also, with the eyes there are very objective tests for visual acuity,” he notes, “so we can measure performance gains very objectively.” Tracking improvement after spinal cord injury, on the other hand, is notoriously tricky.
ACT has faced its share of financial struggles. Indeed, says Lanza with a laugh, there were times during the therapy’s development when the company was about to have its phone service disconnected. “But we made it,” he says.
Image: The fundus of the eye, showing intermediate macular degeneration.
Credit: The National Eye Institute, via Wikipedia