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Tiny button will treat CNV in Phase I/II clinical trial
Theragenics Corporation® will investigate the safety and efficacy of using the TheraSight™ Ocular Brachytherapy System to treat wet AMD. With the TheraSight Ocular Brachytherapy System, therapy is administered using a tiny button, which produces low-energy x-rays. The button is mounted on an applicator wand, which is positioned behind the eye and held in place, touching the outer surface of the eye for 5 to 20 minutes. The low-energy x-rays interfere with the growth of abnormal blood vessels, a process known as choroidal neovascularization (CNV), which is responsible for vision loss in people with wet AMD.
The study will take place at six clinical sites and will compare three different dosages or amounts of radiation. All participants will receive one treatment.
Selected eligibility and exclusion criteria — participants should:
- Be 50 years of age or older
- Not have had prior AMD therapy for the same eye
- Not have diabetes
- Not have had a cardiovascular or cerebrovascular event within the last year. (These events include congestive heart failure, heart attack, and stroke.)
For further information about the trial, including more detailed eligibility and exclusion information, contact Theragenics Corporation at 1-877-960-1234 or visiting http://www.clinicaltrials.gov/ct/show/NCT00100087?order=1.
Learn more about Theragenics Corporation at www.theragenics.com.
Squalamine shows good results in Phase II study
Genaera Corporation’s intravenous therapy for the wet form of age-related macular degeneration (AMD), squalamine, performed well in a six-patient, Phase II clinical trial. All participants, all of whom have wet AMD in both eyes, had improved or preserved vision during and after the trial. All participants received four weekly doses of squalamine, and experienced improved or preserved vision at week three of therapy (after two doses), week five (at end of therapy), and after two months. Gain or loss of less than 15 letters (three lines) of visual acuity is considered to be preserved vision. Gain of 15 letters or more of visual acuity is considered to be improved vision.
Genaera is currently conducting three large Phase II trials for squalamine treatment at multiple sites throughout the U.S. One of those trials will include photodynamic therapy with Visudyne® before and after squalamine treatment.
Participants in all of the trials must:
- Be 50 years of age or older
- Have a diagnosis of wet AMD
- Have not had prior AMD treatment in the affected eye
For more information about trial participation, patients and physicians should call Genaera’s Clinical Trials Hotline at 1-800-299-9156. Additional information about Genaera can be found at their Web site, www.genaera.com.
In October 2004, the Food and Drug Administration (FDA) granted a Fast Track designation to squalamine. The FDA’s Fast Track designation is given to facilitate and expedite the development and review of drugs that treat serious or life-threatening conditions.
Squalamine’s effectiveness comes from its anti-angiogenic properties, meaning that it inhibits the growth of blood vessels. The proliferation of unhealthy, leaky blood vessels under the retina causes substantial vision loss for people with wet AMD. Specifically, squalamine appears to block the action of growth factors — including vascular endothelial growth factor (VEGF) — which cause the formation of deleterious blood vessels.
Derived from the liver of the dogfish shark, squalamine is also being studied for the treatment of cancer. As a cancer therapy, it inhibits the development of tumors by blocking the growth of the blood vessels that nourish them.
RNA interference technology in Phase I trial
Acuity Pharmaceuticals has begun testing a technique called RNA interference for inhibiting choroidal neovascularization (CNV) — the growth of unhealthy, leaky blood vessels under the retina. CNV causes vision loss in wet AMD.
Acuity’s product, Cand5, works by destroying certain messenger RNA. Left intact, the messenger RNA would instruct retinal cells to produce vascular endothelial growth factor, a protein that causes vision-robbing CNV.
Because Cand5 is in a Phase I clinical trial, it is primarily being tested for safety. However, researchers will also make some assessments of efficacy.
In a study published on February 18, 2004 in the journal Retina, Acuity reports that Cand5 safely inhibited CNV growth as well as blood vessel leakage in non-human primates.
Blocking stem cells inhibits progress of wet AMD
Stem cells are receiving much publicity, because their regenerative properties make them promising for the treatment of innumerable conditions and ailments including: Parkinson’s disease, spinal cord injuries, diabetes, and retinal degenerative diseases.
However, stem cells can also play a destructive role in the body and the eye. Scientists have discovered that they are a major factor in the proliferation of tumors. Progenitor stem cells — the stem cells that naturally occur in the tissue and organs of humans and animals — are responsible for driving tumor growth.
Researchers are also learning that endothelial precursor cells (EPCs) — stem cells found in bone marrow — contribute to the growth of vision-robbing blood vessels underneath the retina in patients with wet AMD. The abnormal process is known as choroidal neovascularization (CNV).
In a study published in the January 2005 issue of Investigative Ophthalmology & Visual Science, researchers were able to reduce blood vessel growth by preventing stem cell homing and adhesion to the choroid — the layer of tissue under the retina where unhealthy blood vessels grow in people with wet AMD.
In a prior study, researchers learned that the protein vascular endothelial cadherin (CD-144) was involved in stem cell adhesion to the choroid, and that the protein stromal derived factor (SDF)-1 was involved in stem cell homing to the choroid.
In the current study, researchers used a CD-144 antibody to prevent EPC adhesion, and an SDF-1 antibody to prevent EPC homing of EPCs. Though both treatments in mice were effective and reduced CNV, the CD-144 antibody appeared to be more effective.
The study was conducted by researchers from the Program in Stem Cell Biology at the University of Florida in Gainesville, Florida, and the Retina Center in Gainesville, Florida.
Further studies of these antibodies for the prevention of CNV and the progression wet AMD in humans are planned.
DISCLAIMER: Physicians differ in their approach to incorporating research results into their clinical practice. You should always consult with and be guided by your Physician’s advice when considering treatment based on research results.
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