New medical, genetic therapies dominate advances in retina field

In this report from the OSN Section Editor Summit, Eugene de Juan Jr., MD, discusses recent news in retina.

Many developments are currently taking place in the retina field, including the introduction of new drugs, the advent of genetic therapies and the adoption of new surgical instrumentation.

Why is there so much activity in the retina field now, especially in the area of age-related macular degeneration? One important reason is the effect the disease has on our patients’ quality of life.

If you look at patients’ answers to quality-of-life questionnaires — validated, approved, National Institutes of Health-sponsored quality-of-life measures — mild AMD is rated similar to other debilitating conditions, such as symptomatic AIDS or moderate angina. In response to questions about quality of life, such as, “How do you get around?” “Can you drive?” and “Can you read?” with moderate AMD the patient cannot do any of those things.

Some of these questionnaires ask if a patient would rather be blind than deaf or not be able to walk. From a quality-of-life standpoint, I think I’d rather be blind than have a stroke and be bedridden and incontinent, but from the standpoint of functioning, there’s not a lot of difference. If I can’t see, I can’t drive and I can’t read.

Genes identified

There has been much progress in the area of gene research and potential gene therapy in retina in recent years.

Eugene de Juan Jr.

The ABCR gene was the first gene to be associated with AMD. It is the gene responsible in Stargardt’s disease, so it’s a macular disease gene, but it has also been found in retinitis pigmentosa and in pattern dystrophy.

Pattern dystrophy looks just like AMD to everybody but a retina specialist. Pattern dystrophy is a different disease. It is a softer disease than AMD. Depending on how you want to define it, it either is AMD or it’s not AMD. The issue about this gene is that it does not correlate with vision loss. So the picture looks like AMD, but it’s not the AMD that causes blindness.

Complement factor H is a gene that does correlate with vision loss in AMD. Who would have thought that an inflammatory disease is somehow associated with AMD? Five groups confirmed this association at the same time. In whites, complement factor H appears to cause AMD in 35% of people with the gene. Not everyone with this gene, even if they’re homozygous, gets the disease.

The complement system essentially is the system that punches holes into cells and lyses them. There is the alternative pathway or the classic pathway. The alternative pathway was described second, so it was the alternative. It may be more important in certain cases. The things that activate the alternative pathway are bugs, crystalline cholesterol or beta peptides.

Temporary vs. permanent therapy

There are two types of gene therapies: the temporary kind, which is drug therapy, and the permanent kind, which goes into the DNA through an adenovirus vector, similar to the cold virus.

The adeno-associated virus vector is a permanent vector, it goes into the DNA, and this year researchers are going to be targeting Leber’s congenital amaurosis. This is a multigenic disease. It has five or six genes associated with it.

Researchers have been able to inject this vector, carrying a gene therapy, into blind dogs, and the dogs are able to see. So research in humans may begin soon. It’s possible that within a year they might inject this drug into a blind child, and he or she will be able to see.

Nutrition

Who would have thought that a vitamin could reduce visual loss in patients with AMD? The Age-Related Eye Disease Study (AREDS) supplement prevents choroidal neovascularization, which is the major cause of visual loss in AMD, but it doesn’t prevent the disease. The supplement has no effect on the development of drusen.

A follow up to the AREDS trial, AREDS 2, is scheduled to begin soon. This trial will evaluate the efficacy of additional supplements including lutein, zeaxanthin, omega-3 fatty acids and combinations of these supplements. I think the findings from AREDS 2 are going to be positive.

We’ve learned so much from AREDS we should be looking into nutritional supplementation for diabetic retinopathy. I think that’s something we will see in the next few months.

Therapeutics

Therapeutics are where the real story has been in the past few years. The latest therapeutic drug approved for use in AMD is Lucentis (ranibizumab, Genentech), which received Food and Drug Administration approval in June.

When I saw the data on Lucentis presented at the American Society of Retinal Specialists meeting in Montreal in 2005, I thought that I had seen something that was equivalent to the invention of penicillin. That is how interesting this drug is. I did not ever think we would see a therapy that improved vision in AMD. I had accepted that as a fact. Maybe we could stop visual loss, but we were not going to improve it. The statistics are that something like 30% or 40% of patients treated now are 20/40 or better.

However, what is beginning to be talked about now is that an injection into the eye introduces significant risk of cardiovascular event or stroke. AMD without an injection has a myocardial infarction risk of 1.3%. That goes up to 2.9% with a 0.5-mg injection into the eye. It has a 3% incidence per year, and there’s no indication that you can stop this therapy. It prevents leakage, but it doesn’t treat the disease.

Regarding Avastin (bevacizumab, Genentech), Philip J. Rosenfeld, MD, PhD, published a handful of cases where he injected the drug into the eye, and he showed dramatic results. Now 18 out of 20 physicians are either using it in their practice or want to start using it. The American Academy of Ophthalmology sent a letter to the Centers for Medicare and Medicaid Services supporting reimbursement for Avastin therapy in AMD when it is medically appropriate.

The AAO and the American Society of Retinal Specialists are saying, “All of us, if we had the disease, or if our parents had the disease, would want the best available therapy.” We are talking about blindness vs. sight.

So the use of Avastin is a moral-ethical issue, just as much as it is a regulatory one. We as physicians must decide whether we want our practices being invaded by off-label use. Can we do that or not, and do we give up this therapy that seems to be so effective?

Other treatment strategies

PDT with steroids is still widely used and accepted in Europe. They are reporting improved results. There is not much published data, just as there is not much published data on Avastin, but if you look at the small, anecdotal series, they show overall average visual improvement.

There are other strategies for AMD treatment being investigated. There are several anti-VEGF strategies.

There are short-interfering RNAs. This is another interesting approach in which the drug goes into the cell and knocks out the VEGF being produced, and this is very exciting.

The problem with that, as opposed to the anti-VEGF therapies, is that SiRNAs have to actually go into the cell. It is not a simple slam-dunk, even though it’s exciting, because it’s a new therapeutic approach.

Intravitreal implants

Steroid implants are going to play an important role in the posterior segment, just as steroid drops do in anterior segment ophthalmology. These implants have shown dramatic results for uveitis.

The Bausch & Lomb Retisert implant has to be surgically implanted. It is basically a stab incision with one suture. This is one reason that I think we should not go to the OR to do this.

The Surmodics implant is one with which I was personally involved. It has now been used in about 40 patients with no problem, no retinal detachment, and if we want to we can put it back in. It is designed to last more than a year. You can put a glaucoma drug on it. If you want to increase it, decrease it, or stop it, you can do all of that with this type of device. I think it’s a next-generation device.

25-gauge vitrectors

Three years ago, less than 10% of vitreoretinal surgeons were using 25-gauge vitrectors. Now 40% of us are using it. So every year its use is almost doubling. There is also a fallback position, the 23-gauge vitrector. It uses basically the same transconjunctival approach.

For vitreoretinal surgeons these smaller gauge instruments are the equivalent of the cataract surgeon’s clear corneal incision. It is much easier on the eye, much easier on the surgeon.

These next-generation instruments are not going to do vitrectomy that much better. They are going to make our lives easier, and the cost savings is going to be found in staff reduction.

To me, the 25-gauge has changed the way I think about vitreoretinal surgery. It’s changed the way I think about a lot of surgeries. We can do almost everything through a 25-gauge needle.

For more information:

• Eugene de Juan Jr., MD, OSN Retina/Vitreous Section Member, can be reached at the Beckman Vision Center, 10 Koret Way, K321, San Francisco, CA 94143-0730; 415-514-3178; fax 323-442-6519; e-mail: forsight@gmail.com.