Stem cells approved to treat ‘orphan’ disease

Stargardt’s Macular Dystrophy is the most common form of
genetic juvenile macular degeneration. Manifestation of the condition begins in
late childhood, leading to legal blindness. It is symptomatically similar to
age-related macular degeneration, and it affects approximately one in 10,000
children.  Olympic and Paralympic skier Brian McKeever is the best-known victim
of the disease, which has no treatment.  Today the company Advanced Cell
Technology obtained "Orphan Drug Status" of use of its embryonic stem cell
derived product MA09-hRPE as a treatment for Stargardt’s disease. 

Orphan Drug Status is a mechanism the government uses to
promote interest of pharmaceutical in disease for which a small market exists. 
Typically to obtain this the target market must be less than 200,000 people in
the United States.  Orphan Drug Status allows a company to retain market
exclusivity for seven years, as well as allows for various clinical trial tax

Human embryonic stem cells have been demonstrated to be
capable of giving rise to the cells that make up practically every tissue in the
body.  The ability of these cells to make anything from liver, to lung, to nerve
cells makes them attractive as sources of replacement tissues to biomedical
researchers. Last year the Obama Administration opened federal funding to
more-recent generations of such stem cells, and in January allowed research
funding to cells such as ACT’s, grown from a single cell clipped from an
early-stage embryo.

Designation of Orphan Drug Status is not approval of the
embryonic stem cell based product for sale, but only classifies the cells as a
product in development.  Approval of a drug, whether it is a chemical, a
biologic, or a cell, requires clinical trials in which safety and efficacy is
demonstrated.  The initial hurdle companies must pass is to obtain
Investigational New Drug status.  This was only granted to one embryonic stem
cell company, Geron, for use of their embryonic stem cell derived
oligodendrocytes for treatment of spinal cord injury.  The approval, however,
was rapidly retracted after additional preclinical data demonstrated development
of abnormal growths in treated animals.  Subsequent to IND approval companies
have to demonstrate safety in Phase I studies, efficacy in Phase II studies, and
double blinded efficacy in Phase III studies which usually involve numerous
clinical trial sites. 

The major problem with embryonic stem cell derived products
is the risk of tumor formation.  In general embryonic stem cells are defined by
the ability to form a type of cancer called teratoma.  These tumors are highly
aggressive and comprise numerous cells of the body.  When Advanced Cell
Technologies or Geron are differentiating retinal epithelia cells, or
oligodendrocytes, respective, they must demonstrate to the FDA that no
contaminating stem cells are present in the injection mixture that could
possibly lead to tumor formation.  Another drawback of embryonic stem cell
technology is that it is extremely difficult to selectively add new cells to the
area of injury.  Specifically, the de novo created functional body cells must be
capable of integrating into the existing cells and taking over their function. 
Optimization of these approaches requires understand the molecular cues involved
in natural stem cell differentiation into cells of the body.    Yet another
drawback is that embryonic stem cell lines are not patient-specific.  This
requires the use of immune suppression, which often comes with numerous side

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