NeoVista, Inc announced the official commencement of the CABERNET (Cnv Secondary Amd Treated with BEta RadiatioN Epiretinal Therapy) clinical trial for the treatment of subfoveal choroidal neovascularization associated with wet age-related macular degeneration (AMD). Neovascular AMD is the leading cause of irreparable blindness in the elderly population, afflicting over 200,000 individuals each year in the U.S.
Dr. Nelson Sabates, Professor and Chairman, Department of Ophthalmology, University of Missouri-Kansas City (UMKC)/Truman Medical Centers and Director of Vision Research Center, University of Missouri-Kansas City at Truman Medical Centers performed the procedure on the first patient enrolled in the CABERNET study. When asked for initial feedback on the procedure, Dr. Sabates commented, "The procedure was no different than performing a common vitrectomy and the Epi-Rad device allowed me to deliver a well focused dose of radiation to the lesion. Treating neovascular AMD using a multi-faceted approach like the use of radiation and anti-VEGF therapy may well be the next frontier in combating this sight threatening disease."
The CABERNET clinical trial will involve clinical sites in the United States, Europe, Israel, and South America. The CABERNET trial protocol is divided into two treatment arms - investigational and control.
The investigational treatment arm consists of concomitant delivery of Beta radiation, via the proprietary NeoVista technology (Epi-Rad90™), and an FDA approved anti-VEGF agent. The investigational treatment is administered during an outpatient surgical procedure and delivers Beta radiation directly to the area of the retina that has been compromised by the disease. An injection of the anti-VEGF agent is administered at the time of surgery with one additional injection administered 30 days after surgery. The control arm is utilizing the FDA approved anti-VEGF agent alone.
The surgery was performed in collaboration with, Saint Lukes Hospital in Kansas City. Dr. Terry J. Wall, J.D., M.D. of the Saint Lukes Cancer Institute was the attending radiation oncologist involved with the procedure.
"This is a very good day for NeoVista employees and the investors who are supporting our work," stated John N. Hendrick, President and CEO of NeoVista. "More importantly, it is a potential harbinger of hope for those suffering from wet AMD." We remain optimistic that our treatment approach will provide maximum benefit to this patient population."
Monday, July 26, 2010
Treatment for Cataracts/ other eye diseases
What is a cataract?
There is only one known treatment for cataracts - surgery! A cataract needs to be removed only when vision loss interferes with your everyday activities, or the things you like to do such as driving, reading, sewing, playing golf or watching TV . You and your eye care professional can make this decision together. Once you understand the benefits and risks of surgery, you can make an informed decision about whether cataract surgery is right for you. In most cases, delaying cataract surgery will not cause long-term damage to your eye or make the surgery more difficult. You do not have to rush into surgery.
Additionally, Medicare and most commercial insurance carriers require that best corrected vision be reduced to some level (often 20/50 visual acuity) before they will approve the surgery for payment.
Sometimes a cataract should be removed even if it does not cause problems with your vision. For example, a cataract should be removed if it prevents examination or treatment of another eye problem, such as age-related macular degeneration or diabetic retinopathy.
If you choose surgery, your optometrist will refer you to an ophthalmic surgeon to remove the cataract. This is a very definite advantage over choosing an eye surgeon out of the phone book or from your friends because your doctor knows firsthand the quality of the cataract surgery performed by local eye surgeons. Because they work with the eye surgeons and usually perform some or all of the post-op care they truly know where to refer you for the best possible outcome. If you have cataracts in both eyes that require surgery, the surgery will be performed on each eye at separate times, usually four to eight weeks apart.
As with any surgery, cataract surgery poses risks, such as infection and bleeding. Before cataract surgery, your doctor may ask you to temporarily stop taking certain medications that increase the risk of bleeding during surgery. After surgery, you must keep your eye clean, wash your hands before touching your eye, and use the prescribed medications to help minimize the risk of infection. Serious infection can result in loss of vision. Talk to your eye care professional about these risks. Make sure cataract surgery is right for you.
Cataract surgery slightly increases your risk of retinal detachment. Other eye disorders, such as high myopia (nearsightedness), can further increase your risk of retinal detachment after cataract surgery. One sign of a retinal detachment is a sudden increase in flashes or floaters. Floaters are little "cobwebs" or specks that seem to float about in your field of vision. If you notice a sudden increase in floaters or flashes, see an eye care professional immediately. A retinal detachment is a medical emergency. If necessary, go to an emergency service or hospital. Your eye should be examined by a retinal specialist as soon as possible. A retinal detachment causes no pain. Early treatment for retinal detachment often can prevent permanent loss of vision. The longer the retina stays detached, the less likely you will regain good vision once you are treated. Even if you are treated promptly, some vision may be lost.
There is only one known treatment for cataracts - surgery! A cataract needs to be removed only when vision loss interferes with your everyday activities, or the things you like to do such as driving, reading, sewing, playing golf or watching TV . You and your eye care professional can make this decision together. Once you understand the benefits and risks of surgery, you can make an informed decision about whether cataract surgery is right for you. In most cases, delaying cataract surgery will not cause long-term damage to your eye or make the surgery more difficult. You do not have to rush into surgery.
Additionally, Medicare and most commercial insurance carriers require that best corrected vision be reduced to some level (often 20/50 visual acuity) before they will approve the surgery for payment.
Sometimes a cataract should be removed even if it does not cause problems with your vision. For example, a cataract should be removed if it prevents examination or treatment of another eye problem, such as age-related macular degeneration or diabetic retinopathy.
If you choose surgery, your optometrist will refer you to an ophthalmic surgeon to remove the cataract. This is a very definite advantage over choosing an eye surgeon out of the phone book or from your friends because your doctor knows firsthand the quality of the cataract surgery performed by local eye surgeons. Because they work with the eye surgeons and usually perform some or all of the post-op care they truly know where to refer you for the best possible outcome. If you have cataracts in both eyes that require surgery, the surgery will be performed on each eye at separate times, usually four to eight weeks apart.
As with any surgery, cataract surgery poses risks, such as infection and bleeding. Before cataract surgery, your doctor may ask you to temporarily stop taking certain medications that increase the risk of bleeding during surgery. After surgery, you must keep your eye clean, wash your hands before touching your eye, and use the prescribed medications to help minimize the risk of infection. Serious infection can result in loss of vision. Talk to your eye care professional about these risks. Make sure cataract surgery is right for you.
Cataract surgery slightly increases your risk of retinal detachment. Other eye disorders, such as high myopia (nearsightedness), can further increase your risk of retinal detachment after cataract surgery. One sign of a retinal detachment is a sudden increase in flashes or floaters. Floaters are little "cobwebs" or specks that seem to float about in your field of vision. If you notice a sudden increase in floaters or flashes, see an eye care professional immediately. A retinal detachment is a medical emergency. If necessary, go to an emergency service or hospital. Your eye should be examined by a retinal specialist as soon as possible. A retinal detachment causes no pain. Early treatment for retinal detachment often can prevent permanent loss of vision. The longer the retina stays detached, the less likely you will regain good vision once you are treated. Even if you are treated promptly, some vision may be lost.
Monday, July 19, 2010
Foveal Macular Edema Treatments
Located in the foveal region of the retina, the macula is an important part of the visual system, responsible for clear central vision. A damaged macula means distorted vision when looking at objects straight ahead. Macular edema, one type of damage, occurs when fluid accumulates in the tissue under the macula. Causes of edema include ocular inflammation and, more commonly, complications from uncontrolled diabetes. Prompt treatment is crucial to preserving vision when macular edema occurs.
Laser Treatment
According to the Mayo Clinic, macular edema is the leading cause of decreased vision in patients with early diabetic eye complications, also called background diabetic retinopathy. Uncontrolled diabetes leads to leakage of blood vessels in the back of the eye. Fluids, such as blood and fatty lipid material called exudates, can then accumulate. This can lead to numerous complications, including swelling under the macula tissue. When this occurs, clinically significant macula edema requires treatment with a focal laser procedure, also called focal laser photocoagulation. Laser light focused on the macula targets the leaky vessels, resulting in laser scars or burns that help reduce further leakage and the amount of fluid accumulated. If laser treatment for both eyes is necessary, the treatments are usually scheduled a few weeks apart. Focal laser photocoagulation is the mainstay treatment for macular edema caused by diabetic retinopathy and, according to the National Eye Institute, reduces the chance for vision loss by 50 percent.
Anti-inflammatory Drugs
Macular edema can result from retinal inflammation. It often follows procedures such as cataract surgery. In this type of edema, cyst-like pockets of fluid build up in the macular region--hence its name cystoid macular edema--and the reason for its development is unknown. Often, steroidal anti-inflammatory eyedrops are prescribed to treat cystoid macular edema. An injection of steroids--such as cortisone--into the eye can be necessary in cases of more severe edema. According to the University of Michigan, injecting steroids intraocularly for macular edema caused by diabetes is an emerging treatment option. Repeat injections are often necessary.
Vitrectomy
The vitreous is the large, gel-like area that makes up a bulk of the back of the eye. It comes in contact with the retina and macular tissue. Sometimes tugging of the macula by the vitreous gel can lead to macular edema. When this occurs, it's recommended to have surgery to remove the vitreous gel. This procedure is called a vitrectomy. A vitrectomy is also performed when macular edema and other complications caused by diabetes result in significant blood accumulation in the vitreous. This procedure is usually recommended for advanced diabetic cases.
Preventive Care
The most serious type of macular edema is connected to diabetic retinopathy, because there is a high risk for vision loss. Therefore, doctors strongly recommend control and care of blood sugar through diet, exercise and medication. Other preventive measures include annual eye exams and controlling other diseases such as high blood pressure and high cholesterol. The National Eye Institute reports that macula edema can often occur without symptoms of blur, so preventive care is essential to detecting it before lasting damage can occur.
Laser Treatment
According to the Mayo Clinic, macular edema is the leading cause of decreased vision in patients with early diabetic eye complications, also called background diabetic retinopathy. Uncontrolled diabetes leads to leakage of blood vessels in the back of the eye. Fluids, such as blood and fatty lipid material called exudates, can then accumulate. This can lead to numerous complications, including swelling under the macula tissue. When this occurs, clinically significant macula edema requires treatment with a focal laser procedure, also called focal laser photocoagulation. Laser light focused on the macula targets the leaky vessels, resulting in laser scars or burns that help reduce further leakage and the amount of fluid accumulated. If laser treatment for both eyes is necessary, the treatments are usually scheduled a few weeks apart. Focal laser photocoagulation is the mainstay treatment for macular edema caused by diabetic retinopathy and, according to the National Eye Institute, reduces the chance for vision loss by 50 percent.
Anti-inflammatory Drugs
Macular edema can result from retinal inflammation. It often follows procedures such as cataract surgery. In this type of edema, cyst-like pockets of fluid build up in the macular region--hence its name cystoid macular edema--and the reason for its development is unknown. Often, steroidal anti-inflammatory eyedrops are prescribed to treat cystoid macular edema. An injection of steroids--such as cortisone--into the eye can be necessary in cases of more severe edema. According to the University of Michigan, injecting steroids intraocularly for macular edema caused by diabetes is an emerging treatment option. Repeat injections are often necessary.
Vitrectomy
The vitreous is the large, gel-like area that makes up a bulk of the back of the eye. It comes in contact with the retina and macular tissue. Sometimes tugging of the macula by the vitreous gel can lead to macular edema. When this occurs, it's recommended to have surgery to remove the vitreous gel. This procedure is called a vitrectomy. A vitrectomy is also performed when macular edema and other complications caused by diabetes result in significant blood accumulation in the vitreous. This procedure is usually recommended for advanced diabetic cases.
Preventive Care
The most serious type of macular edema is connected to diabetic retinopathy, because there is a high risk for vision loss. Therefore, doctors strongly recommend control and care of blood sugar through diet, exercise and medication. Other preventive measures include annual eye exams and controlling other diseases such as high blood pressure and high cholesterol. The National Eye Institute reports that macula edema can often occur without symptoms of blur, so preventive care is essential to detecting it before lasting damage can occur.
Friday, July 16, 2010
Gene Therapy for Eye Diseases
The pharmaceutical giant Genzyme has started a clinical trial to see whether a drug to treat macular generation could be delivered via long-lasting gene therapy rather than monthly injections.
Eye colors: Drusen, the yellow flecks in this image of the retina, are common in people with age-related macular degeneration. These flecks are made up of proteins involved in the part of the immune system called the complement system, which has also been implicated in the disease by genetic studies.
A drug called Lucentis, made by Genetech, has proved effective at treating the wet form of age-related macular degeneration, which can lead to blindness. Some 200,000 Americans a year are diagnosed with the disease. But Lucentis has to be injected into the eye every month or two, a burden for patients and doctors.
Lucentis binds to and neutralizes a wound-healing growth factor known as VEGF. This binding action stalls the excess growth of blood vessels in the eye that characterizes age-related macular degeneration. Genzyme's gene therapy drug, officially called AAV2-sFLT01, would insinuate itself into the patient's retinal cell to produce the same VEGF-binding protein as Lucentis over far longer periods--up to several years.
A phase 1 clinical trial of Genzyme's gene therapy treatment began at the end of May. Three patients received the treatment, according to Sam Wadsworth, a Genzyme group vice president in charge of gene and cell therapy. Preliminary results should be available in about a year.
The trial is one of a handful worldwide seeking to prove the effectiveness of gene therapy for eye diseases. The Genzyme trial also involves using new type of virus as the delivery mechanism. Early results of a federally funded trial to deliver normal-functioning genes to patients with a rare retinal disease known as type 2 leber congenital amaurosis, or LCA, have confirmed that this "viral vector" has merit for eye treatments, several researchers say.
The LCA trials "demonstrated success both in terms of safety and ability to introduce the gene and have efficacy and success," said Jeffrey S. Heier, an assistant professor at Tufts University School of Medicine and director of retinal research at Ophthalmic Consultants of Boston, a private practice group, who is involved in the Genzyme research. "This study is taking the virus vector that they used, and [Genzyme has] taken what has really been the success of the anti-VEGF story and they've packaged the two together."
Eyes have been an early target for gene therapy because they are small--meaning they require relatively little active dose, they are self-contained, and because the tools of eye surgery have advanced enough to make the treatments possible. The drug has to be delivered to the retina, a thin film lining the inner wall of the eye. Instrumentation has improved in recent years to allow injections through the retina without piercing it, said Shalesh Kaushal, chairman of ophthalmology at University of Massachusetts Memorial Medical Center and UMass Medical School.
To Kaushal, who is involved in the Genzyme study as well as the LCA research, the big challenge will be broadening the use of gene therapy to dozens more diseases, and using that understanding to eventually reach beyond the eye. "If one could understand those fundamental cellular, biochemical events and identify targets, you might have the chance to treat many diseases with a single gene-therapy construct," Kaushal said.
Earlier gene therapy programs used a type of virus called adenovirus to target genes, but both the LCA and Genzyme trials are using adeno-associated virus, which is far less inflammatory and which expresses itself over longer periods than adenovirus, therefore making the treatment last longer, Wadsworth said. Viruses are used to deliver gene therapies because they are adept at getting through cell walls.
VEGF is involved in vascular cell growth throughout the body, and its expression increases in the presence of a wound. Studies have shown that with Lucentis, virtually all the VEGF-binding protein stays within the eye, and does not significantly affect VEGF levels elsewhere in the body, Wadsworth says. Genzyme's drug will provide even lower levels of the VEGF-binding protein, so it's expected that the drug will not have any adverse affects throughout the body, he said.
The trick will be getting the cells to produce enough VEGF-binding protein to help patients, said Peter Campochiaro, a professor at the Wilmer Eye Institute at Johns Hopkins Medicine, who is involved in the research. In addition to establishing safety, the current phase 1 trial will explore four different doses of the study
Eye colors: Drusen, the yellow flecks in this image of the retina, are common in people with age-related macular degeneration. These flecks are made up of proteins involved in the part of the immune system called the complement system, which has also been implicated in the disease by genetic studies.
A drug called Lucentis, made by Genetech, has proved effective at treating the wet form of age-related macular degeneration, which can lead to blindness. Some 200,000 Americans a year are diagnosed with the disease. But Lucentis has to be injected into the eye every month or two, a burden for patients and doctors.
Lucentis binds to and neutralizes a wound-healing growth factor known as VEGF. This binding action stalls the excess growth of blood vessels in the eye that characterizes age-related macular degeneration. Genzyme's gene therapy drug, officially called AAV2-sFLT01, would insinuate itself into the patient's retinal cell to produce the same VEGF-binding protein as Lucentis over far longer periods--up to several years.
A phase 1 clinical trial of Genzyme's gene therapy treatment began at the end of May. Three patients received the treatment, according to Sam Wadsworth, a Genzyme group vice president in charge of gene and cell therapy. Preliminary results should be available in about a year.
The trial is one of a handful worldwide seeking to prove the effectiveness of gene therapy for eye diseases. The Genzyme trial also involves using new type of virus as the delivery mechanism. Early results of a federally funded trial to deliver normal-functioning genes to patients with a rare retinal disease known as type 2 leber congenital amaurosis, or LCA, have confirmed that this "viral vector" has merit for eye treatments, several researchers say.
The LCA trials "demonstrated success both in terms of safety and ability to introduce the gene and have efficacy and success," said Jeffrey S. Heier, an assistant professor at Tufts University School of Medicine and director of retinal research at Ophthalmic Consultants of Boston, a private practice group, who is involved in the Genzyme research. "This study is taking the virus vector that they used, and [Genzyme has] taken what has really been the success of the anti-VEGF story and they've packaged the two together."
Eyes have been an early target for gene therapy because they are small--meaning they require relatively little active dose, they are self-contained, and because the tools of eye surgery have advanced enough to make the treatments possible. The drug has to be delivered to the retina, a thin film lining the inner wall of the eye. Instrumentation has improved in recent years to allow injections through the retina without piercing it, said Shalesh Kaushal, chairman of ophthalmology at University of Massachusetts Memorial Medical Center and UMass Medical School.
To Kaushal, who is involved in the Genzyme study as well as the LCA research, the big challenge will be broadening the use of gene therapy to dozens more diseases, and using that understanding to eventually reach beyond the eye. "If one could understand those fundamental cellular, biochemical events and identify targets, you might have the chance to treat many diseases with a single gene-therapy construct," Kaushal said.
Earlier gene therapy programs used a type of virus called adenovirus to target genes, but both the LCA and Genzyme trials are using adeno-associated virus, which is far less inflammatory and which expresses itself over longer periods than adenovirus, therefore making the treatment last longer, Wadsworth said. Viruses are used to deliver gene therapies because they are adept at getting through cell walls.
VEGF is involved in vascular cell growth throughout the body, and its expression increases in the presence of a wound. Studies have shown that with Lucentis, virtually all the VEGF-binding protein stays within the eye, and does not significantly affect VEGF levels elsewhere in the body, Wadsworth says. Genzyme's drug will provide even lower levels of the VEGF-binding protein, so it's expected that the drug will not have any adverse affects throughout the body, he said.
The trick will be getting the cells to produce enough VEGF-binding protein to help patients, said Peter Campochiaro, a professor at the Wilmer Eye Institute at Johns Hopkins Medicine, who is involved in the research. In addition to establishing safety, the current phase 1 trial will explore four different doses of the study
Wednesday, July 7, 2010
Tyrosine Kinase inhibitor shows promise for AMD treatment
A new study finds that inhibition of CXCR4 may be useful in preventing neovascularization but does not appear to have an effect on already established angiogenesis, whereas a multiple receptor tyrosine kinase inhibitor (SU14813) reduced the size of previously formed lesions.
Endothelial precursor cells (EPCs) derived from hematopoietic stem cells (HSCs) have been shown to contribute to choroidal neovascularization (CNV) by signaling through the SDF-1 and its receptor, known as CXCR4. Hematopoietic stem cells are implicated in the formation of new pathologic vessels observed in wet AMD. Recruitment of endothelial precursor cells to the site of neovascularization is mediated, in part, by the chemokine SDF-1, and its receptor, CXCR4. CXCR4 is a G-protein-coupled receptor found on lymphocytes, monocytes, hematopoietic, endothelial progenitor cells, and mature endothelial cells.
Methods and Results
CNV in rats was generated by focal rupture of Bruch's membrane with an 810-nm diode laser. In the prevention mode, a CXCR4 antagonist (AMD3100) was delivered via an osmotic pump 1 day after laser induction. In the intervention mode, AMD3100 delivery commenced 14 days after laser induction. Inhibition of CXCR4 was determined through leukocyte and SDF-1 actin polymerization blood biomarker assays. Leakage was assessed by fluorescein angiography, and CNV lesion size was quantified after isolectin B4 endothelial cell staining. SU14813, an anti-VEGFR, PDGFR-beta, KIT, and FLT3 inhibitor, was also assessed in an intervention study protocol.
Related News
CCR3 is a target for AMD diagnosis and therapy
Integrin α5β1 inhibitor JSM6427 combats CNV in animal study
Stem cells show promise to restore vision
Inhibition of CXCR4 was demonstrated by an increase in the number of blood leukocytes, and diminished SDF-1 induced actin polymerization in whole blood. CNV leakage and neovascularization were inhibited when the dose regimen was initiated 1 day after laser-induced CNV induction. AMD3100 did not show efficacy when administered 14 days after lasering. Treatment with SU14813 significantly decreased CNV leakage and lesion size in an intervention modality.
Discussion and Conclusions
In this study, CXCR4 inhibition was efficacious in the prevention of CNV, but failed to reduce choroidal leakage and angiogenesis in the intervention modality. This finding suggests that therapies targeting the SDF-1/CXCR4 axis may be beneficial in blocking the induction of ocular neoangiogenesis, but are unlikely to reduce already established angiogenesis.
There is strong evidence that CXCR4 inhibition disrupts the recruitment of endothelial precursor cells (EPCs) to sites of angiogenesis, most likely the major mechanism leading to efficacy in the prevention model.
In addition to suppressing CNV, CXCR4 inhibition reduced choroidal vascular leakage in the prevention modality (but not in the intervention modality). It is not known whether CXCR4 inhibition decreases leakage directly or as a secondary effect of the reduction of the angiogenic vessel area.
The observation that CXCR4 inhibition did not decrease choroidal leakage or angiogenic lesion size in the intervention modality suggests that after a 2-week generation of laser-induced CNV, there is limited, if any, contribution of EPC cells to the already established vessels
A multiple receptor tyrosine kinase (RTK) inhibitor may still be an effective monotherapy, as SU14813 reduced the size of previously formed lesions. In treatment mode, both leakage and angiogenesis decreased even after the pathologic effect was given 14 days to fully establish before drug intervention. This study suggests that blockade of the VEGF receptor is an effective alternative method of inhibiting the VEGF pathway compared to conventional anti-VEGF strategies.
SU14813 is a small molecule with broad target RTK selectivity, inhibiting the VEGF receptor (VEGFR), PDGFR-β, KIT, and FLT3. Although the primary mechanism that reduces preexisting angiogenesis and leakage is the blockade of the central VEGF pathway, the additional inhibition of PDGFR-β may augment efficacy in this model over single anti-VEGFR agents.
The investigators conclude that inhibition of CXCR4 may be useful in preventing neovascularization but does not appear to have an effect on already established angiogenesis. A multiple receptor tyrosine kinase inhibitor (SU14813) approach shows promise for the treatment of wet age-related macular degeneration.
Endothelial precursor cells (EPCs) derived from hematopoietic stem cells (HSCs) have been shown to contribute to choroidal neovascularization (CNV) by signaling through the SDF-1 and its receptor, known as CXCR4. Hematopoietic stem cells are implicated in the formation of new pathologic vessels observed in wet AMD. Recruitment of endothelial precursor cells to the site of neovascularization is mediated, in part, by the chemokine SDF-1, and its receptor, CXCR4. CXCR4 is a G-protein-coupled receptor found on lymphocytes, monocytes, hematopoietic, endothelial progenitor cells, and mature endothelial cells.
Methods and Results
CNV in rats was generated by focal rupture of Bruch's membrane with an 810-nm diode laser. In the prevention mode, a CXCR4 antagonist (AMD3100) was delivered via an osmotic pump 1 day after laser induction. In the intervention mode, AMD3100 delivery commenced 14 days after laser induction. Inhibition of CXCR4 was determined through leukocyte and SDF-1 actin polymerization blood biomarker assays. Leakage was assessed by fluorescein angiography, and CNV lesion size was quantified after isolectin B4 endothelial cell staining. SU14813, an anti-VEGFR, PDGFR-beta, KIT, and FLT3 inhibitor, was also assessed in an intervention study protocol.
Related News
CCR3 is a target for AMD diagnosis and therapy
Integrin α5β1 inhibitor JSM6427 combats CNV in animal study
Stem cells show promise to restore vision
Inhibition of CXCR4 was demonstrated by an increase in the number of blood leukocytes, and diminished SDF-1 induced actin polymerization in whole blood. CNV leakage and neovascularization were inhibited when the dose regimen was initiated 1 day after laser-induced CNV induction. AMD3100 did not show efficacy when administered 14 days after lasering. Treatment with SU14813 significantly decreased CNV leakage and lesion size in an intervention modality.
Discussion and Conclusions
In this study, CXCR4 inhibition was efficacious in the prevention of CNV, but failed to reduce choroidal leakage and angiogenesis in the intervention modality. This finding suggests that therapies targeting the SDF-1/CXCR4 axis may be beneficial in blocking the induction of ocular neoangiogenesis, but are unlikely to reduce already established angiogenesis.
There is strong evidence that CXCR4 inhibition disrupts the recruitment of endothelial precursor cells (EPCs) to sites of angiogenesis, most likely the major mechanism leading to efficacy in the prevention model.
In addition to suppressing CNV, CXCR4 inhibition reduced choroidal vascular leakage in the prevention modality (but not in the intervention modality). It is not known whether CXCR4 inhibition decreases leakage directly or as a secondary effect of the reduction of the angiogenic vessel area.
The observation that CXCR4 inhibition did not decrease choroidal leakage or angiogenic lesion size in the intervention modality suggests that after a 2-week generation of laser-induced CNV, there is limited, if any, contribution of EPC cells to the already established vessels
A multiple receptor tyrosine kinase (RTK) inhibitor may still be an effective monotherapy, as SU14813 reduced the size of previously formed lesions. In treatment mode, both leakage and angiogenesis decreased even after the pathologic effect was given 14 days to fully establish before drug intervention. This study suggests that blockade of the VEGF receptor is an effective alternative method of inhibiting the VEGF pathway compared to conventional anti-VEGF strategies.
SU14813 is a small molecule with broad target RTK selectivity, inhibiting the VEGF receptor (VEGFR), PDGFR-β, KIT, and FLT3. Although the primary mechanism that reduces preexisting angiogenesis and leakage is the blockade of the central VEGF pathway, the additional inhibition of PDGFR-β may augment efficacy in this model over single anti-VEGFR agents.
The investigators conclude that inhibition of CXCR4 may be useful in preventing neovascularization but does not appear to have an effect on already established angiogenesis. A multiple receptor tyrosine kinase inhibitor (SU14813) approach shows promise for the treatment of wet age-related macular degeneration.
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