Two Decades of Progress in

Retinal Degeneration Research: 1990-2011

From Scientific Darkness to the Light

of Clinical Trials

ohenetihoolLGerald J. Chader, Ph.D., M.D.hc

Doheny Eye InstituteLos Angeles, CA USA

os Angeles, CA University atloOctober 22, 2009

What is Our Goal?To rapidly move from research at the laboratory bench to the clinic to deliver preventions, treatments and cures for all patients within the two general families of inherited retinal degenerations – the RPs and the Macular Degenerations.

How do we get to our Goal?

• The path starts with scientific “Proof of Principle”, i.e., lab work

that shows that a treatment is safe and works in RD animal models.

• Our basic scientists have done their job well in giving us much information on the RDs – including treatments.

• Work on RP and allied diseases leads the way and is mainly based on genetic studies…

So Let’s look at some of the Progress in RP Genetics…..

• In 1990, the first RP gene mutation was reported. This was in the rhodopsin gene in work by Dr. Humphries, Farrar and group and then by Drs. Dryja and Berson.

• Now: Over 160 genes have been identified whose mutations cause forms of RD such as RP and the other rare degenerative diseases.

• It is thought that we now know about 50% of the mutations.

Genes for Rare Diseases• Most of the Rare Inherited Retinal Diseases are

considered to be part of the RP Family. • But - as special subgroupings, we have:

Usher Syndrome – where 9 genes are known whose mutations lead to forms of Ushers.

Bardet-Beidl – 13 genes known

LCA – 16 genes known whose mutations account for up to 70% of problems in LCA.

• Several mutations leading to macular degenerations also have been identified – e.g., the ABCA4 mutation in Stargardt disease

Also, Progress in Cell BiologyBefore 1990, we had almost no way to slow

photoreceptor cell degeneration and we did not understand the mechanism by which photoreceptor cells died in RP, but,

In 1990, Drs. Steinberg and LaVail reported the first natural factor that slowed photoreceptor cell death in an animal model of RP. These are now called “Neurotrophic Agents” or “Neuron-Survival Agents”.

Now, we know that photoreceptor cells die by a common mechanism called “Apoptosis” or “Programmed Cell Death” in both RP and AMD. Neurotrophic Agents work by inhibiting the Apoptosis pathway and this process is now called “Neuroprotection”.

Now, What Are the Major Contributing Factors To The AMD Disease Process?

Unlike RP, AMD is a complex disease with several risk factors not just the genetic input:

1) Gene Mutations – Gene mutations have been implicated in almost 3/4

of AMD cases. Mostly these are genes that are related to our immune system. Because of this, it is much more difficult to do simple gene replacement therapy in AMD patients than in RP patients.

2) Environmental Factors – Things like smoking that might directly cause AMD

or work with gene mutations to greatly increase the risk factor.

But, whatever the initial cause, AMD is a slow disease of aging, again making it difficult to treat.

Basic Science SummaryResearchers have now established a firm basis in the

genetics and cell biology of most of the RD diseases.• We know many of the genetic mutations. • We also know the common pathway (apoptosis) that

leads to cell death and we know several neuron-survival agents that slow apoptosis.

• Animal models for many of the RD diseases are known. These are invaluable since approval for human Clinical Trials is much easier if efficacy and safety can be demonstrated in an animal model.

Now, building on this basic information what potential treatments and cures for the RDs are here or are coming?

• But, before talking about specific treatments, we must first understand the different disease situations that will determine which type of therapy might or might not be applied.

The first disease situation is…

When most or all of the photoreceptor or RPE cells do not function or are dead.

Here we use treatments that replace the deadcells or at least replace

their function in the retina.

Therapies could be:1)Transplantation: the use

of fresh tissue or of Stem cells (Progenitor)

2) Electronic Prosthetic

Devices (Artificial Vision) 3) Optical Photoswitchs

The second disease situation is…

When at least some photoreceptor cells yet are alive.

Here, we would use treatments that prolong

photoreceptor life and make them function better such as:4) Neuroprotection for

both RP and AMD5) Anti-angiogenic agents in wet AMD6) Antioxidants7) Gene Therapy

1) PhotoreceptorTransplantation

• If photoreceptor cells are dead, why not just transplant normal photoreceptor cells into the RD retina from a normal donor retina?

• Unfortunately, this has shown only limited success in many animal studies.

• Dr. Norman Radtke in the USA had gotten government approval to treat several human RP patients by photoreceptor cell transplantation and has reported good safety but only very limited efficacy.

• So, photoreceptor cell transplantation has yet to be proven to be effective.

1) Stem CellTransplantation• Stem cells are multipotential cells that have the ability to develop into all different adult cell types – such as photoreceptor cells.• So, stem cells transplanted into the retina might replenish the supply of photoreceptor cells that died due to degeneration.

Q.: For RP, Can We Actually Transform Stem Cells into Mature Photoreceptor Cells?

Good progress has been made in differentiating SCs into photoreceptor cells with many adult characteristics but more work yet needs to be done. Safety looks good in RD animal models.

In an important preclinical study, human embryonic stem cells transplanted into the retina of a mouse model of LCA restore some visual function. A human clinical trial could result.

Q.: Are There Sources of Stem Cells Other Than Embryonic?

Some scientists are studying stem cells derived from adult tissues to see if they can develop into photoreceptor cells.

Some scientists are studying cells called “photoreceptor precursors” from the young, developing retina.

Some scientists are working to see if they can transform support cells of the retina called Muller glial cells into photoreceptors.

A clinical trial is underway in Brazil using bone marrow-derived stem cells injected into the eye in RP patients. No final news yet.

In AMD, the Focus is on Stem Cells Replenishing the RPE Cell Layer

• The RPE may be the first cell type affected in AMD and in some RPs. Therefore, transplantation of fresh RPE cells could save the photoreceptors.

• Successful transplantation of donor RPE cells in RP animal models was first reported in 1988 (Turner).

• Some groups (Binder) have already transplanted human RPE cells in wet AMD with fairly good results.

• The supply of natural RPE cells is small but a ready source could come from stem cells induced to differentiate into mature, functional RPE cells.

Clinical Trials?Advanced Cell Technology (ACT)

is conducting a clinical trial using embryonic stem cells to supply new RPE cells in Stargardt Disease and AMD. Good results already had been reported in a mouse RD model.

Other groups are working on RPE cell replacement in AMD using established cell lines of human ESCs. The ESCs are induced to differentiate into mature RPE cells for use in transplantation. Preclinical results are good.

London Project to Cure Blindness

California Project to Cure Blindness

Future Treatment?

• For Direct Photoreceptor cell transplantation: Not yet!

• For ESC→Photoreceptor Cells: research is continuing. It is not yet clear that all photoreceptor characteristics can be induced in the cells.

• For Photoreceptor repopulation from other cell types: good progress is being made in basic, preclinical research.

• For ESC →RPE cells: a clinical trial is underway for Stargardt disease and dry AMD.

2) Artificial VisionUses an electronic prosthetic device to replace the function of dead photoreceptor cells.

The design is simple:

1)External camera captures the light image and converts it to an electrical signal

2)Computer processing

3)Electronic signal passes to an array of electrodes attached to remaining inner retinal cells in the eye.

4)Finally, the signal is passed down the optic nerve to the brain to produce a visual image.

Clinical Trials?

• Second Sight Medical Products implanted about 40 RP patients in Europe and the Americas. With these, Dr. Mark Humayun at USC has reported good results in restoring at least some functional vision. Importantly, safety is very good over several years.

• Other groups such as in Ireland are doing great work. Professor Zrenner in Tuebingen is doing excellent clinical work on another type of retinal device that should lead to a commercial product in the near future.

Status of Present SSMP Clinical Trial and Future Work to Restore More Useful Vision Argus 1: Phase 1 clinical trial started in 2001; now finished

- the 1st generation device with 16 electrodes on implant - very good safety record - restores light perception and some form vision

Argus 2: Phase 2/3 trial just finished – CE-Mark approval- 60 electrodes – better vision and increased mobility- smaller package and reduced surgical time

3rd generation device: in design and prototype production - 200+ electrodes on the implant - should give even better vision

4th generation device: in design - 1000+ electrodes on implant

- restoration of face recognition and reading ability - restoration of independent living and work ability if lost

Testing: Object Recognition with Argus 1

Testing: Comparing Object Recognition using Argus 1 vs. Argus 2

Argus I (16 Electrodes)* Argus II (60 Electrodes)

*AJO 2007, 143:820-827 Visual performance using a retinal prosthesis in three subjects with retinitis pigmentosa. Yani et al.

15 sec 2 sec

Argus II patients Can Read Letters and Words

Courtesy Drs. da Cruz and Webster (Moorfields Eye Hospital, London)

Argus II Subjects Can Identify Numbers

Courtesy Drs Sahel, Barale, Said, Scheer (Quinze-Vingts, Paris, France)

Examples:

• Walking a line

• Walking to an object 20 ft. away

Improvement in Orientation and Mobility Tasks with the Argus 2:

Future Treatments?

• Several groups are doing human testing including at least three companies.

• SSMP has a product that has received the European CE-Mark and is available for general implantation in RP but not yet dry AMD.

• Technologies are being improved to allow for face recognition and reading ability.

This is NOT Vision of Terminator orGeordi from Star Trek…..Yet

Cortical Implant (Dobelle)

3) Optical Photoswitches

• Many animal and plant cells have proteins that react to light and produce an electrical signal.

• Molecular engineering can be used to insert channelrhodopsin molecules into retinal ganglion cells in RD animals to make them light sensitive.

• These light signals can be passed on to the brain which can distinguish a “lights on” or “lights off” situation.

Chlamydomonas is a tiny one celled algae that contains a light-sensitive protein called channel rhodopsin

Future Treatments?

• Basic work on Photoswitches is yet at an early stage of development.

• Some only work at very high and dangerous light intensities.

• Some react to light too slowly to be useful in human vision.

• However, photoswitches could yet give functional vision if these problems can be overcome.

Remember that the second disease situation is……

when some living photoreceptors yet remain.

Possible therapies would be:

4) Neuroprotection

5) Antiangiogenic Agents in wet AMD

6) Antioxidants

7) Gene Therapy

4) Neuroprotection In 1990, Steinberg and LaVail

first showed that a natural neuron-survival factor could delay photoreceptor cell degeneration in an animal model of RP.

• Now, this research area is called “Neuroprotection”.

• because many natural factors in brain, retina and other tissues have been found that inhibit photoreceptor cell death. One is named CNTF.

• We now have over 30 “Neurotrophic Factors” or “Neuron-Survival Agents” .

7 Days after PDT: PBS vs. CNTF

PBS

CNTF

Neuroprotection: Clinical Trials?

• Neurotech is in clinical trials with CNTF on RP and dry AMD.

• Using a technique called Encapsulated Cell Technology, they deliver the neuron-survival protein, CNTF to the retina.

• In ECT, a small capsule is placed inside the eye of the patient. In the capsule are special cells that produce CNTF.

• The CNTF diffuses out of the capsule and enters the retina where it helps to protect the sick photoreceptor cells.

Future Treatments?

• The current Neurotech clinical trial should soon be completed. It has shown good results.

• It thus should produce the first effective and generally available treatment for most forms of RP and dry AMD.

• There are many other neurotrophic agents to try in the future.

Drugs:Valproic Acid

• Valproic Acid is a small molecule that is used - epilepsy, seizures, and similar conditions.

• It has been reported to improve vision in some RP patients.

• The mechanism of neuro-protection by VA is unknown but may be through anti-oxidative or anti-inflammatory properties.

• The drug can have serious side effects but none were found in a small preliminary study.

• The US FDA has approved a 3 year trial on 90 adRP patients.

For dry AMD, there Are Possible Treatments Using Small Molecule Drugs

Use of Fenretinide in a Phase 2 trial from Sirion• Fenretinide is an analog of vitamin A that will

hopefully slow Geographic Atrophy. It slows down the visual process and thus slows the accumulation of toxic byproducts likeA2E.

• In the trial, it reduced the risk of progression to wet AMD by 2.2-fold. Phase 3 study coming.

Use of Brimonidine in a Phase 2 trial from Allergan• a drug already used in glaucoma to lower IOP.• may protect in Geographic Atrophy.• supplied by intraocular implant – good for 1-2 yr.

AMD: A Complex Disease• The causes of AMD are complex and so are

treatment regimes. It is almost as if dry and wet AMD are separate diseases.– For dry AMD, many pathways are available to

slow the disease process as in RP.

– In wet AMD, there is an unexplained growth of new abnormal blood vessels near the retina. This is called angiogenesis or neovascularization. These new, abnormal vessels can leak and bleed and quickly degrade vision. Thus, the aim is simple: stop the neovascularization and promote regression of the abnormal vessels (membranes).

5) Wet AMD Treatment

An early step in neovascularization is tissue production of a growth factor such as VEGF which calls in new abnormal blood vessels. Thus, inhibiting VEGF is the current main focus in treating wet AMD. Two of these inhibitors are:

Lucentis - Genentech’s antibody that binds and inactivates VEGF.

• It actually can improve vision• But… cost is high!Avastin is a well-studied anti-cancer

drug very similar to Lucentis. • It thus has been used “off-label”

in wet AMD because the cost is far less than Lucentis.

What’s New?

Because of the high cost of Lucentis, it was important to see if Avastin worked as well and was as safe. So, several clinical trials were designed to make the comparison.

The results of the US-CATT trial (Comparison of AMD Treatment Trials) and the UK-IVAN studies show that the 2 agents are comparable in action.

• A trial in Brazil also reported that action of the 2 drugs is “comparable” in efficacy and safety.

• In spite of this, some controversy yet remains in the use of Avastin in wet AMD –but they work!

New Player in Field: VEGF Trap from Regeneron

• VEGF Trap strongly binds or “traps” and inactivates VEGF. It does not allow it to bind to its natural receptor. This stops it from stimulating new blood vessel growth.

• The phase 3 trial found VEGFTrap is “non-inferior” to Lucentis with a “favorable” safety profile.

• This agent should soon join Lucentis and Avastin in use for treating wet AMD.

Trials using Gene Therapy: • Bevasiranib – a gene silencing molecular approach

to anti-neovascularization from OPKP.• RetinoStat – a gene-therapy based approach to

stopping new blood vessel formation from Oxford Biomedica. It delivers the genes for 2 natural anti-angiogenic proteins to the retina. Phase I/II clinical trial.

• Genvec – also uses gene therapy to deliver a potent anti-neovascular protein called PEDF to the retina. The trial seems to be completed but there has been no final public announcements.

• Bottom Line: Many new treatments in the pipeline!

6) AntioxidantsIt is clear that antioxidants can slow disease progression

in some patients with mid-stage dry AMD. This was proven in the AREDS clinical trials.

In RP, two research groups - Van Veen and Campochiaro have demonstrated that antioxidants slow the course of retinal degeneration in RP animal models. This is specifically photoreceptor cell death through apoptosis so the treatment is applicable to dry AMD as well as RP. .

Antioxidant Trial van Veen fed animals with retinal degeneration a special combination of antioxidants and slowed the degeneration process.

Together, they are called RetinaComplex.

Based on this preclinical work, a small clinical trial in Spain has finished on RP and dry AMD patients. The results look good. More extensive trials are planned.

Ingredients:

Lutein, zeaxanthin, alpha-lipoic acid, L-glutathione, extract of lycium barbarum (wolfberry)

Are There Other Antioxidant Trials?

NEI AREDS2 Trial: Lutein/Zeaxanthin These yellow pigments called carotenoids from plants are

concentrated in the retina after eating. • It is thought that they act as antioxidants and thus

protect photoreceptor cells. • Testing here is also with unsaturated fatty acids –

Omega - 3 LC-PUFAs.Othera’s Omega Study: Eye drops used to treat GA• The agent (OT-551) is thought to be an antioxidant.

Mixed results have been reported. It is an important study since the treatment is non-invasive!

The Women’s Antioxidant and Vitamin B Study:• Epidemiology data from a very large group of women at

risk of cardiovascular disease indicates that daily supplementation with B vitamins significantly reduces their risk of AMD.

Future Treatments?

• First, the ongoing clinical trials such as on Lutein and on RetinaComplex must be completed. Look good!

• It is clear that antioxidants are important in both RP and AMD

• In the future, there are many types of antioxidants that can be tested in RD animal models and then in the human.

• Until then, take your mother’s advice – Eat your Vegetables!

7) Gene Therapy

• Gene Therapy is the replacement of defective mutated genes in living cells with new, normal copies of the gene.

• The new gene will synthesize a normal protein product that replaces the mutated or missing protein and restore photoreceptor cell function.

• Long-term, positive effects of Gene Therapy in RP animal models have been shown even if treatment is done fairly late in the disease after significant photoreceptor loss.

Extensive Preclinical Gene Therapy Studies

• In 2001, Dr. Gus Aguirre and a consortium of investigators reported remarkable restoration of visual function in Lancelot the Briard dog, a model for Leber’s disease – born blind.

• After therapy, Lance’s ERG was greatly improved and functional connections to his brain could be demonstrated.

• It is over 10 years later now and all the dogs first treated are still seeing very well.

Gene Therapy Clinical TrialsThe newer and exciting news is that Gene Therapy will

not just slow down the RD disease process but it can restore some visual function in the human.

• About 3 years ago, Robin Ali et al. started the first gene therapy clinical trial supplying a normal copy of the RPE65 gene to specific patients with LCA. Other groups soon started similar trials and all the patients seem to be doing well with some restored vision.

• The focus now is on early treatment, i.e., children.• This success can now be used as a model for

treatment of many other retinal diseases.

Future Treatments?

Now, trials are planned for:• Stargardt’s Disease • LCA 5 – Lebercillin • Retinoschisis• Forms of Usher Syndrome• Choroideremia

Also, for forms of dominant, recessive and X-linked RP.

Gene Replacement Therapy for AMD is more difficult because it is a complex disease but gene therapy can yet be useful here.

In Conclusion….Before 1990- No gene mutations for RD were known. We had little

idea as to the mechanism of photoreceptor cell death and there were no agents know that could slow the degeneration and cell death.

Now – Basic science work has identified about one-half of the

RP gene mutations and about ¾ of the gene mutations for AMD.

Much is known about the basic mechanism of photoreceptor cell death, apoptosis, in both RP and AMD and how to inhibit it through Neuroprotection.

Also Now – some treatments are actually available:• For RP patients, electronic implants (to be improved)• In dry AMD, the AREDS supplements and, in

Stargardt’s as well, we have an implantable miniature telescope (IMT) which magnifies images on the macula

• In wet AMD, effective antineovascular agentsAlso, several Clinical Trials are in progress in

Neuroprotection, Gene Therapy, Antioxidant Therapy and the use of Stem Cells

Other basic work such as with Optical Photoswitches shows great promise for future Clinical Trials.

In Conclusion….

So, looking back on 1990-today….

I hope you agree that we are finally passing out of the time of scientific darkness and into the enlightened era of clinical trials.

These should soon lead to many new therapies that will save and restore vision in all RD patients.

THANK YOU FOR YOUR ATTENTION!

Another Wet AMD Clinical Trial -RPE Cell Transplantation

Why transplant fresh RPE cells in AMD?RPE cells are critical in supporting photoreceptor cell

function and early degeneration of RPE cells is a hallmark of AMD leading to photoreceptor death.

• Some researchers think that defects in RPE cells could precede other damage.

Boltzman Institute Trial (Dr. S. Binder):• To test if RPE cell transplantation helps at the time

of surgical extraction of submacular neovascular membranes in wet AMD.

• Good preliminary results have been reported.

Other Trials include…• Focal Radiation Treatment – from Neovista.

(Intraocular Brachytherapy) Here a dose of focal radiation with radioactive strontium-90 is delivered directly to the choroidal neovascular membranes to kill the new blood vessel cells.

A recently completed phase 3 trial reports that vision is stabilized and that the treatment is safe.

• Finally, combination therapy is being investigated. This uses combinations of agents such as corticosteroids and anti-VEGF agents with PDT.

• Conclusion: There are many new treatments for wet AMD coming soon and we have gone a long way from the first treatment available – PDT.