Download Gene Therapy in RP - University of Louisville Ophthalmology

Gene Therapy in Retinitis Pigmentosa (RP)
Henry J Kaplan, MD
Evans Professor of Ophthalmology
Chair, Department of Ophthalmology & Visual Sciences
Director, Kentucky Lions Eye Center
University of Louisville
Iran 2015
Overview - Gene Therapy in RP
• Gene therapy in Leber’s Congenital
Amaruosis, type 2 (LCA 2)
– Childhood form of RP
– Gene mutation for LCA 2 in RPE65 gene
• Gene therapy in RP
– Most common form of ADRP in North America
– Pro23His mutation in Rhodopsin
Objective of Gene Therapy in Photoreceptor
Degeneration
• Basic objective is
delivery of genes to
cells induce protein
expression
• Where the disease is the
result of an absent gene
(i.e. a null gene mutation)
the objective is to replace
the missing protein
• Where the disease is the
result of an abnormal
protein (mutant gene
mutation) the objective is to
overwhelm the function of
the abnormal protein with
the normal or wild-type
(WT) protein
Objective of Gene Therapy in Photoreceptor
Degeneration
Viruses are most
frequently used to
deliver genes, e.g. AAV
(adeno-associated
virus), but
nanoparticles,
liposomes and other
approaches can be
used.
Viral induced expression
of a normal protein in
null mutations
(i.e.where no protein is
expressed) and is
straightforward, e.g.
AAV-RPE65
Leber’s Congenital
Amaurosis: Bennett,
Wilson & colleagues
Gene Therapy
• Protocols for delivering genes to retinal tissues most
frequently use adenoviral (AAV) vectors
• AAV vectors efficient in delivering the gene to the
targeted cell but are epigenetic and don’t integrate into
the host cell genome in contrast to retroviral vectors
• Expression is not permanent and repeated delivery may
be required
• Host immune repsonse may develop with repeated
injections even though the eye is immunologically
priviledged
Leber’s Congenital Amaurosis (LCA)
• LCA is a group of diseases with early-onset childhood
retinal dystrophy characterized by vision loss,
nystagmus, and severe retinal dysfunction.
• Usually present at birth with profound or modest
vision loss, pendular nystagmus, nonrecordable ERG
and other clinical findings - hypermetropia,
photophobia, oculodigital sign, keratoconus,
cataracts, and a variable appearance to the fundus.
LCA
• At least 19 different types which result from
mutations in at least 14 genes
• Mutations in CEP290, CRB1, GUCY2D, and RPE65
genes are most common
• Occurs in 2 to 3 per 100,000 newborns and is
responsible for ~ 5% retinal dystrophies
• The loss of cone function at birth or shortly
thereafter clinically distinguishes LCA from RP
LCA 2
• Inherited most frequently as autosomal recessive
disease
• LCA2 is distinguished by moderate visual impairment
at infancy that progresses to total blindness by mid
to late adulthood.
• One of the unique qualities of LCA2 is that, even
with profound early visual impairment, retinal cells
are relatively preserved.
LCA2
Fundus photo with yellow dots and mottling of RPE
Yellow dots, mottling RPE
Posterior staphyloma
Gene Therapy for Leber’s Congenital Amaurosis (LCA)
OS Photoreceptors
• 3 independent initial clinical
trials were performed to
evaluate safety and efficacy
in LCA2 caused by the gene
mutation in RPE65.
• A deficiency of 11-cis-retinal
causes rod photoreceptors
unable to respond to light.
RPE
Initial Clinical Trials
• Patients were treated with a single unilateral subretinal
injection of adenoassociated virus 2 (AAV2) carrying the
RPE65 gene in the eye with the worst vision
• No serious adverse effects from AAV2
• Short-term follow-up showed an improvement in selected
measures of vision - including BCVA, kinetic VF, nystagmus,
pupillary light reflex, microperimetry, DA perimetry, and DA
full-field ERG
3 Year F/U in CHOP LCA2 Trial
• Showed that in 5 patients the improvements in visual and
retinal function that had been achieved a few months after
treatment remained stable.
• The maximum improvement was achieved within 6 months
after treatment. Improved BCVA only achieved posttreatment in patients without nystagmus.
• No serious adverse effects.
• F Testa, et al. Ophthalmology 2013;120:1283–1291
Clinical Data from Trial
BCVA
FAF
Jacobson SG. et al. Improvement and Decline in Vision with Gene
Therapy in Childhood Blindness N Engl J Med. 2015 May 14;
372(20): 1920–1926.
• Three years after therapy in 5 patients, improvement in
vision was maintained in 3, but the rate of loss of
photoreceptors in the treated retina was the same as
that in the untreated retina.
• Long-term follow-up data from three treated patients
showed topographic maps of visual sensitivity in
treated regions, nearly 6 years after therapy for two of
the patients and 4.5 years after therapy for the third
patient, indicate progressive diminution of the areas of
improved vision.
J.W.B. Bainbridge et al. Long-Term Effect of Gene Therapy on
Leber’s Congenital Amaurosis. N Engl J Med. 2015 May 14;
372(20): 1887–1897
• Improvements in retinal sensitivity, to varying extents, in 6 of 12
participants for up to 3 years, peaking at 6 to 12 months after
treatment and then declining.
• No associated improvement in retinal function was detected by
means of ERG.
• Three participants had intraocular inflammation, and two had
clinically significant deterioration of visual acuity. The reduction in
central retinal thickness varied among participants.
• CONCLUSIONS—Gene therapy with rAAV2/2 RPE65 vector
improved retinal sensitivity, albeit modestly and temporarily. In
dogs, RPE65 gene therapy with the same vector at lower doses
improved vision-guided behavior, but only higher doses resulted in
improvements in retinal function that were detectable with the use
of ERG.
Retinitis Pigmentosa
 Classic fundus
presentation
 Attenuated retinal vessels
 Mottling/granularity of RPE
 Bone-spicule intraretinal
pigmentation
 Optic nerve head pallor
 Clinical symptoms – night
blindness, constricted
peripheral visual field
 Diagnostic testing abnormal ERG recordings
Why do patients ultimately go blind in RP?
• Although rod
photoreceptor loss
results in nyctalopia and
a constricted visual
field, blindness and
major visual disability
results from cone
photoreceptor
dysfunction and
ultimately death in late
stages of the disease
Objective of Gene Therapy in Pro23His
Retinopathy – Most Common Form AD RP
• But when a mutant
protein is expressed,
can expression of a
virally induced native
protein offset the
mutant protein?
– AAV- cDNA Rho 
expression of Rho
– AAV-siRNA Rho 
suppression of Rho
Preliminary conclusion – gene therapy with cDNA Rho causes
no harm and appears to delay cone loss in P23H retinopathy
Gene Therapy for Pro23His Mutation in ADRP
•
WW Hauswirth and colleagues. Long-Term Rescue of Retinal Structure and
Function by Rhodopsin RNA Replacement with a Single Adeno-Associated Viral
Vector in P23H RHO Transgenic Mice. HUMAN GENE THERAPY 23:356–366 (April
2012)
• They delivered both a modified cDNA and an siRNA by a single
AAV vector and observed long-term rescue of ADRP in this
mouse model. Because the siRNA targets human as well as
mouse rhodopsin mRNAs, the combination vector may be
useful for the treatment of human disease.
LONG-TERM RESCUE OF MOUSE PHOTORECEPTORS BY mRNA
REPLACEMENT
Conclusion
• The molecular ability to shutdown the mutant protein
produced by the diseased cell with siRNA and then produce
normal protein with simultaneously introduced “hardened”
cDNA is an exciting innovation that we are exploring with
Hauswirth, Lewin and colleagues in our model of P23H
retinopathy in the mini-swine.
• Gene therapy for LCA 2 and P23H retinopathy in RP are being
intensively explored and hold great promise.