As has been reported broadly this week, transplantation of human embryonic stem cell-derived retinal pigment epithelial cells appears to be safe in human patients, and it may even be efficacious (although this can only be confirmed via a Phase II trial).
Advanced Cell Technology (of California) published a preliminary clinical report of their Phase I clinical trials online this Monday in the Lancet. The two Phase I clinical trials were initiated at UCLA’s Jules Stein Eye Institute in July 2011. These trials aimed to treat Stargardt’s Macular Dystrophy and Dry Age-Related Macular Degeneration (two major causes of blindness in the developed world). Each trial will enroll up to 12 patients, with a safety endpoint at 12 months. Four months following transplantation, no adverse affects such as tumorigenicity, ectopic tissue formation, inflammation or cell proliferation could be detected in patients.
The subretinal space of one eye in each patient was injected with retinal pigment epithelial cells generated from human embryonic stem cells. The retinal pigment epithelium is a single cell-thick protective layer in the eye. In the eye of a macular degeneration patient, retinal pigment epithelial cell degeneration causes dysfunction of photoreceptors (which sit on top of the retinal pigment epithelium) and vision in that area of the eye is lost.
Although visual acuity assessments revealed functional improvements in the transplanted eye of each patient, these results should be interpreted with caution. While the Stargardt’s Macular Dystrophy patient only showed improvement in the transplanted eye, the Dry Age-Related Macular Degeneration patient showed improved visual function in both. However, the injected eye did show more improvement than the non-treated eye.
Despite the fact that Monday’s report is very preliminary (results from only two patients at the four-month mark), the company must have a great deal of confidence in the trial for it to have made this public announcement. Additionally, Advanced Cell Technology announced in a press release published on their website Monday that patient enrollment has now begun in the UK for a Phase I clinical trial for Stargardt’s Macular Dystrophy and the first patient was treated in London last Friday.
This exciting news comes just two months after Geron’s announcement to end the first ever FDA-approved human embryonic stem cell Phase I clinical trial, a move described as a strategic financial decision by Geron (covered in a previous blog entry). Disappointment and controversy surrounded the sudden halt of the Geron trial and some question the motive behind this decision. Some speculate that a lack of efficacy in this safety trial is what lead Geron to pull the plug.
Although it felt like the stem cell community took a number of hits in 2011 (including the shut down of the Geron trial and the prohibition of patents for human embryonic stem cell products by the EU), it seems that 2012 is off to a great start.
Angela C. H. McDonald
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