Stem Cells: A Promise Deferred? - Pharmaceutical Executive

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Stem Cells: A Promise Deferred?


Pharmaceutical Executive


High risks remain

Aberman uses Geron, the first company to invest heavily in developing stem cell therapies, as a supportive example of Pluristem's approach. Geron shuttered its embryonic stem cell R&D programs late last year, a sign many interpreted as a swan song for stem cell therapies. "Geron was involved in the field for 20 years, and they tried to differentiate hESC for spinal cord injury. They spent about $500 million over 20 years, and nothing happened," says Aberman. "Talking with them a year ago before they shut down, they agreed that the therapeutic effect is achieved by the factors that are secreted by the embryonic stem cell...so why mess with embryonic stem cells if you're looking for these [secreted] factors? What we do is inject the cell, which releases a multifactorial process that interacts with the patient's body to generate a paracrine or endocrine effect...that helps the body to heal itself and to change or modify the disease progression."

Advanced Cell Technology (ACT), based in Santa Monica, California, hasn't given up on hESC, but "unlike the conventional methodology for creating human embryonic stem cells," which necessarily destroys the embryo, "we don't do that," says Gary Rabin, CEO. "That activity, obviously, has cultural, religious, ethical, political, and legal repercussions involved." So how does ACT avoid destroying embryos during the derivation process? "We take a much earlier stage embryo, when it's at about the eight-cell stage, and remove a single cell," which is then used as the progenitor cell for ACT's embryonic stem cell lines. "This technique is identical to what's done in pre-implantation genetic diagnostics in IVF clinics," a routine procedure conducted when a parent is donating embryos, and the embryos are screened for significant genetic disorders like Huntington's or Tay-Sachs, for example. "We were last in the IVF clinics in about 2005, so our methodology doesn't destroy, harm, or change the fate of the embryo in any way," says Rabin. The problem with using the NIH approved cell lines, per Rabin, is that the NIH lines "are already exhibiting a fairly significant amount of fate commitment to become the kinds of cells that they're already going to become. Our much earlier stage cells don't exhibit any of this kind of fate commitment, so they're much more efficient at creating the three germ cell layers, than any of the NIH lines we tested."

Having sidestepped the cultural, religious, ethical, political, and legal implications associated with embryonic stem cell research and development, ACT's lead clinical program involves taking hESC and turning them into retinal pigment epithelium (RPE), which are cells that sit at the back of the macula, in the eye. These cells provide "a whole variety of trophic factors," as well as waste removal for the photoreceptor layer. As RPE cells decline, the photoreceptor layer begins to decline, the result of which is age-related macular generation (AMD), "a massive unmet medical need," says Rabin. "There are 15 million people in the United States that have this disease, and there's no cure."


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