WO2008065429A1 - Method for delivering gene therapy vectors to the optic nerve head - Google Patents

Abstract

The invention relates to a method of delivering gene therapy vectors to the optic nerve head, particularly for the treatment of glaucoma.

Description

METHOD FOR DELIVERING GENE THERAPY VECTORS TO THE OPTIC NERVE HEAD

The invention relates to a method of delivering gene therapy vectors to the optic nerve head, particularly for the treatment of glaucoma.

Glaucoma is now the major cause of irreversible blindness worldwide. [1-3] Glaucoma affects 2% of people over 40, & 4% over 80 years in Europe, with a rising incidence as the general shift towards older populations increases. It is characterized by progressive optic nerve damage and visual field loss. Growth factors and various wound healing processes has been implicated in being involved in the pathogenesis and treatment of glaucoma by several different mechanisms: firstly, in trabecular meshwork tissue and aqueous outflow; secondly, and more recently at the optic nerve head (ONH); and finally in the subconjunctival scaring response following glaucoma filtration surgery. [4] Currently all available therapies are aimed at lowering intraocular pressure (IOP), the main identifiable risk factor for the disease.[5, 6] However these treatments do not always prevent visual loss. Furthermore, there is a subgroup of glaucoma patients with "normaP'-recorded IOP (so-called low tension glaucoma (LTG)) yet progressive disease. [7] There is currently a trend therefore for the identification and development of non-IOP lowering glaucoma treatments, the optic nerve head (ONH) being a potential therapeutic target. The process of extracellular matrix (ECM) remodelling at the ONH structure is increasingly implicated in the development of glaucoma. [8] It is believed that the physical force of elevated intraocular pressure (IOP) leads to deformation of the lamina cribosa (seen as "cupping") - a hypothesis supported by biophysical modelling data and histological evidence. [9- 13] Increased deposition of ECM at the ONH is believed to account for the optic nerve axonal compression seen in glaucoma, which then results in retinal ganglion cell (RGC) apoptosis and loss. [14-18]

According to the invention, there is provided a method for delivering gene therapy vectors to the optic nerve head, comprising administering a pharmaceutically acceptable composition comprising the gene therapy vector to the sub-Tenon's space.

Additionally provided is the use of a gene therapy vector in the preparation of a medicament for delivery to the optic nerve head, wherein the medicament is for administration to the sub- Tenon's space. The term gene therapy vector is used herein to mean any delivery vector that can be used to transduce genetic material into a target cell, specifically in this case, cells of the optic nerve head. The term gene therapy vector is used herein to mean a vector containing genetic material to be introduced into the cells of the optic nerve head. Appropriate vectors are well known in the art and include, for example, viral vectors, such as adeno-associated virus vectors, expecially AA V2; naked DNA; liposome complexes and polymer complexes.

The genetic material for transduction is preferably material that allows the production of the extracellular matrix or axonal compression to be modulated. For example, a variety of compounds, such as TGF-β, are involved in these processes. The genetic material for transduction is preferably material that allows the production or effect of such compounds to be modulated. The material may affect the compound itself or a receptor to which the compound binds or any pathway, such as signal transduction pathway upon which the compound or receptor has an effect. The genetic material may, for example, encode a protein that affects the compound or receptor or expression thereof, or may encode, for example, interfering RNA that affects the expression of the compound or receptor. The compound and/or receptor may be affected in any way, for example, the expression of either may be increased or reduced, by, for example, modulating the promotor controlling expression of the compound or receptor, mutating the endogenous DNA encoding the compound or receptor such that compounds or receptors expressed are non functional or have reduced functionality, introducing exogenous DNA encoding the compound or receptor, or modulating a feedback loop that regulates the expression of the compound. Alternatively, the action of either compound or the receptor may be affected by, for example, expressing a molecule that binds to and inhibits the action of the compound or receptor, such as an antibody or fragment thereof, a soluble receptor or fragment thereof or an enzyme, or an agonist or antagonist of the receptor. In one embodiment of the invention, the genetic material may be TGF-β Shield™, available from ResVerlogiX Corp, 202, 279 Midpark Way SE, Calgary, AB T2X 1M2. Alternatively, the genetic material may be DNA encoding, for example, a molecule that binds to and inhibits the activity of TGF-β, or a molecule that antagonises the TGF-β receptor so that the effect of TGF-β expression is minimised. Further the genetic material may be material that reduces the expression of TGF-β or the TGF-β receptor by any appropriate means. The term optic nerve head is used herein to mean the area at the back of the eye where the optic nerve meets the retina, that is to say the area of the eye through which the optic nerve passes to reach the retina. The optic nerve head encompasses the lamina cribosa. The term optic nerve head is well known in the art.

The term sub-Tenon's space means the area between the Tenon's capsule, the fibrous tissue that lines the orbit, and the eyeball. The term is well known in the art. The pharmaceutical composition may be administered to the sub-Tenon's space by any appropriate means, for example, by injection or by using a cannula.

The pharmaceutically acceptable composition is a composition comprising the gene therapy vectors in a pharmaceutically acceptable carrier or vehicle. Appropriate carriers or vehicles are well known in the art and include saline.

According to a second aspect of the invention, there is provided a method for treating glaucoma, comprising delivering gene therapy vectors to the optic nerve head.

Further provided is the use of a gene therapy vector in the preparation of a medicament for treatment of glaucoma, wherein the medicament is for delivery to the optic nerve head.

The gene therapy vectors are as described in relation to the first aspect of the invention. The vectors may be administered to the optic nerve head via any appropriate route, such as intravitreal injection, scleral injection, retrobulbar injection, application to the optic nerve head using a gelfoam or via administration to the sub-Tenon's space. Administration to the sub-Tenon's space is preferred in order to obtain selective delivery to the optic nerve head.

The invention will now be described in detail by way of example only, with reference to the drawings, in which

Figure 1 shows in vivo and histological images of the retina following ONH transduction;

Figure 2 is a comparison of histological retinal montages showing the spread or selectivity of the transduction;

Figure 3 is an in vivo image of a retina following transduction using the sub-Tenon's route; Figure 4 shows in vivo images of retinas following ONH transduction, comparing low and high doses of vectors;

Figure 5 shows a volumetric reconstruction of cross-section through the centre of ONH; Figure 6 shows the results of the picrocirius red stain to evaluate scarring; Figure 7 shows the cellularity following transduction;

Figure 8 shows the level of oxytalan deposits following transduction; Figure 9 shows the level of elastic fibre deposits following transduction; Figure 10 shows the effect of transduction on RGC apoptosis 3, 6 and 12 weeks after intraocular pressure increase; Figure 11 compares the effect of low and high doses of TGF-β on RGC apoptosis; Figure 12 shows the effect of TGF-β on Scleral Canal Opening; and Figure 13 shows the effect of TGF-β on intraocular pressure.

EXAMPLES The inventors have, firstly, assessed the selective transduction of the TGF-β SHIELD™ vector (AA V2) in target cells at the ONH in vivo; secondly, determined the most effective route of administration (vector delivery); and finally established the optimum dose for sustained transduction and GFP expression.

Example 1 Materials

RVX provided 5 vials of AAV-GFP; 1 vial containing 0.825 x 10¹² genomic viral particles (VP) in 250 micro liters, and 4 vials containing 0.132 x 10¹² in 10 microliters/each. Our studies used 3 different doses: a) 0.0033 x lO¹² in 1 μl b) 0.0132 x lθ¹²in 4 μl c) 0.0264 X lO¹² Ui 8 μl

Administration Regimens Animals were randomly assigned to treatment groups as shown below. RVX supplied all agents and the experimenters were "blinded" as the contents of each supplied vial containing the agent. The experiment was in 2 parts a) Assessment of the different modes of delivery was made with imaging of GFP on days 3, 7 and 21, following which they were analysed histologically. (Groups 1-5) b) From the above results, the optimal mode of delivery was identified and different volumes/ doses assessed with histology at Day 7 & Day 21 (Group 6)

Modes of delivery

Routes of administration for vector delivery were chosen at the start of the study, with a view to assessing potential transduction of the ONH & optimizing selective transduction to the target cells. These routes are described below in more detail : a) Intravitreal injection

This is the most commonly used route for intraocular drug administration, where the injection is given directly into the vitreous cavity. Clinically it has become increasingly acceptable in patients since the advent of age-related macular degeneration treatments such as 24 monthly intravitreal injections of ranibizumab (Lucentis) and 6 weekly for 48 weeks of pegaptanib sodium (Macugen). The problem with this mode of delivery, as we had anticipated, is that AAV is known to transduce RGC. [29] b) Scleral injection

This was an injection into the sclera. This mode has recently gained favour for polyamine analogs & sustained release drug delivery. [30] There is little or no data available with respect to AA V2 transduction. c) Local application on Gelfoam around optic nerve

We had suggested this as a potential method - the idea being that local delivery to the ONH would occur as the AA V2 was released slowly. As far as we are aware, this has not previously been described, possibly because this would be an impractical route clinically. This mode consisted of applying AA V2 on to a piece of gelfoam which was then placed behind the globe, around the optic nerve. d) Retrobulbur injection

This route is routinely used in local anaesthesia administration in patients undergoing cataract & intraocular surgery. It involves the transcutaneous injection of anesthetic solution into the retrobulbar space, with anaesthesia being achieved. Retrobulbar block is aimed at blocking the ciliary ganglion and ciliary nerves, and the optic, oculometer & lateral rectus nerves. Due to the optic nerve being accessed in this method, we chose this as a potential mode of targeting ONH. e) Sub-Tenon's injection As selective ONH transduction was not shown effectively in Groups 1-4, a new method of administration was introduced, which in fact clinically has replaced retrobulbar injections for local anaesthesia. This route is via an injection through the membrane surrounding the muscles and nerves posterior to the eyeball. In vivo cSLO imaging and histological assessment of GFP signal

Animals were given injections at Day 0, and then imaged up to Day 21 for assessment of ONH transduction, on days 3, 7 and 21, following which they were analysed histologically. In the second study, animals were killed for histology on Days 7 & Days 21. The animals were killed after the last session of cSLO imaging. The eyes were enucleated and fixed in 4% fresh paraformaldehyde overnight. The retinas were dissected and whole flat retinas were mounted as we have described before. [17, 18] The flat retinas were examined under confocal laser scanning microscopy LSM software (CLSM 510 META; Carl Zeiss Meditec, Oberkochen, Germany). ONH were assessed using both retinal montages [17, 18] and volumetric reconstructions using xl 6 magnification.

Results ONH Transduction a) Identification of best route of administration

Of all routes, the sub-Tenon's mode of vector delivery was found to be best. Typical in vivo and histological images of each route of administration are shown in the figures. As predicted, the intravitreal route was associated with retinal cell transduction as seen in figure

1 in vivo, and confirmed histologically. The scleral route did not provide sustained or selective transduction of ONH cells. Very little ONH transduction was seen with gelfoam delivery. Similarly, the level of sustained ONH transduction seen with retrobulbar injection was low. The sub-Tenon's mode was by far the most effective route of sustained ONH cell transduction

b) Identification of most selective route of administration

Figure 2 is a comparison of histological retinal montages showing the spread or selectivity of the transduction. The sub-Tenon's mode was by far the most effective route of selective ONH cell transduction

The highly selective uptake & transduction of ONH cells with the sub-Tenon's route is well illustrated with the wide-angle in vivo image at 21 days of the 8 μl (highest dose, Group 6) shown in figure 3.

c) Identification of optimal dose of Sub-Tenon's AA V2 for ONH transduction

The lowest doses (1 & 4 μl) of AAV2 showed lower sustained transduction compared to the 8 μl dose, as can be seen in the in vivo images in figure 4. Histological assessment confirmed that the 8 μl dose transduced the ONH, and volumetric reconstructions, showed the majority of cells transduced were in the superficial retinal layer, but cells deeper were also transduced at 21 days. This is illustrated in figure 4.

These results show quite clearly that the sub-Tenon mode of delivery of the AA V2 virus was most effective in transducing ONH cells. Furthermore, the 8 μl dose appeared most successful in achieving a sustained level of transduction. Although predominantly superficial, histological analysis confirmed GFP expression in the multilayered structure of the ONH.

We have deliberately chosen the 21 day time point for our transduction histological timepoints, as our work suggests in the rat OHT model, that peak RGC apoptosis occurs 21 days after surgical induction of elevated IOP. Hence, we would hope that by this stage, good expression of the TGF-β SHIELD in the ONH has already been achieved.

Example 2 Conjunctival Scarring

TGF-β has been implicated in being involved in the pathogenesis and treatment of glaucoma by several different mechanisms: firstly, in trabecular meshwork tissue and aqueous outflow; secondly, and more recently at the optic nerve head (ONH); and finally in the subconjunctival scaring response following glaucoma filtration surgery. [4] Anti-scarring strategies have been increasingly utilized in the surgical treatment of glaucoma. The treatment of this disease is directed towards the reduction of intraocular pressure (the main identifiable risk factor in glaucoma)[31] and includes topical medication, laser and surgical modalities. Of all available therapies, surgery has been shown to be the most effective, being the only method of preventing progressive visual loss. [32, 33] However, it is not always successful due to the occurrence of excessive post-operative scarring. [8, 34] The introduction of wound healing modulators has greatly improved glaucoma surgery results, but unfortunately, their use is limited by severe and potentially blinding complications. [35-37] We have previously identified Transforming Growth Factor-β (TGF-β) as a target for post-operative anti-scarring therapy in glaucoma, using antibodies and antisense oligonucleotides against TGF-β (TGF-β OGN) in the eye. [4, 21 , 38-42] In this part of the study, we have assessed the ability of TGF- β SHIELD™ to inhibit the conjunctival scarring response in an in vivo model we have previously developed. Materials

RVX provided the following:

1. High concentration TGF-β SHIELD (2 x 10¹⁰ particles)

2. Low concentration TGF-β SHIELD (1 x 10¹⁰ particles) 3. AA V2- LacZ control (2 x 10¹ ° particles)

4. AAV2- LacZ control (1 x 10¹⁰ particles)

5. PBS control

Design Animals were randomly assigned to treatment groups as shown below. RVX supplied all agents and the experimenters were "blinded" as the contents of each supplied vial containing the agent.

4 animals /treatment group

5 treatment groups 3 time points for histological analysis at 7, 14 & 30 days after injection Total 60 animals

Methods Conjunctival Scarring

Using our well established model of conjunctival scarring in the mouse eye, we will assess the effects of TGF-β SHIELD in reducing the scarring response after subconjunctival injections. [4, 21, 38-42] We chose 2 doses (low and high concentrations) of TGF-^β SHIELD and both PBS and AAV-delivery vehicle were used as control injections. Subconjunctival injections of either control or treatments were given on Day 0 of the study with animals killed for histological analysis at Days 7, 14 and 30 days. The animals were killed at set time intervals and eyes were enucleated and fixed in 4% fresh paraformaldehyde overnight and embedded whole in paraffin wax. Development of scar tissue was studied in sequential 5 μm thick paraffin sections from enucleated eyes using the following special stains: haematoxylin and eosin (H&E) to assess cellularity, Picrocirius red to demonstrate collagen deposition, aldehyde fuchsin for elastic and elaunin fibres. Sequential sections were assessed for cellularity profile and extracellular matrix deposition by two independent and masked- observers using a grading system previously described. [18, 38, 42] Parameters assessed included: cellularity profile, collagen and elastic fibre deposition. For each treatment group a mean grade per parameter at each time-point (with 95% confidence intervals) was calculated. Analysis was performed using computer software (SPSS for Windows; SPSS Inc.) at individual time points using a one-way analysis of variance (ANOVA). All treatments were compared to control (PBS-carrier). The observed significance levels from multiple comparisons were adjusted using the Bonferroni test with p<0.05 indicating significance, No statistical differences were found in any of the parameters measured between the 2 doses of LacZ control. These two control treatment subgroups were therefore grouped together as a single treatment group in the analysis.

Results Conjunctival Scarring Histological evaluation confirmed the development of a scarring response following injection of phosphate buffered saline (PBS) 27, 38 or the LacZ AA V2 control.

a) Picrocirius Red (see figure 6)

High dose TGF-β SHIELD significantly inhibited the scarring response. Compared to control and LacZ, high dose TGF-β SHIELD treated eyes significantly reducing the amount of subconjunctival picrocirius staining on Day 14, although interestingly this was increased significantly at Day 7. As in our previous anti-TGF-β modulating studies with the mouse model, no effect was seen at 30 days.

b) Cellularity Profile (see figure 7)

No statisitical difference was found between any of the treatment groups in terms of cellularity at any time point.

c) Elastin staining (see figures 8 and 9) Aldehyde fuchsin stains demonstrated elastic fibres with the oxidized version also showing oxytalan fibres, which are representative of the earliest identifiable stage of lastogenesis indicating early local extracellular matrix production and deposition.

The presence of oxytalan fibres showed prolonged increased activity from Day 7 and up to and including Day 30 in the high dose TGF- β SHIELD treatment group. This was statistically significant only at Day 30.

In comparison to oxytalan, the total amount of elastic fibre demonstrated in both TGF- ^β

SHIELD treatment groups was consistently lower than control, although not statistically significant. Summary Conjunctival Scarring

To understand the impact of the results above, it is best first to describe the normal characteristic response seen in the mouse model. As we have previously described, and as seen with our control results here, there is a typical wound healing response seen in this model, where an initial influx (Day 0-2) of granulocytes (neutrophil polymorphonuclear leucocytes) falls to normal levels by day 14, with fibroblast activity remaining elevated up to 30 days. Scar formation and architecture as demonstrated by picrosirius red staining normally shows peak deposition at Day 7. Finally, the aldehyde fuchsin stains which demonstrate elastic fibres we have shown to reach a peak at day 14 in this model, with the oxidized version also showing oxytalan fibres showing peak activity at day 7. The time points chosen for this study were based on results with the TGF- β antisense OGN where efficacy of the OGN were seen at 7 and 14 days. [42] Our studies did not show any significant difference between treatment groups with respect to cellularity. However, the most significant finding in these investigations was the very significant decrease in picrocirius staining found in the high TGF- β SHIELD treatment group at day 14. The changes seen with regard to oxytalan deposition are very interesting. Oxytalan fibres are representatve of the earliest identifiable stage of elastogenesis indicating early local extracellular matrix (ECM) production and deposition. Normally, oxytalan activity should peak before total elastic fibre deposition. The fact that the high TGF- β SHIELD treatment group showed persistent oxytalan activity, and that this reached statistical significance at day 30, suggests that the process of early ECM production was still occurring with little evidence of maturation. In other words, TGF- ^β inhibition had not only delayed the collagen deposition, but also, inhibited the maturation process of elastin fibres. In conclusion, the results of these studies show that the high TGF- β SHIELD treatment is effective in vivo at reducing ocular scarring. We now look forward to assessing this further in a rat model of OHT.

Example 3

Experimental Glaucoma (OHT) Model Our hypothesis for the next part of study was that as TGF-β causes changes in the extracellular matrix at the optic nerve head in glaucoma which leads to axonal compression and retinal ganglion cell apoptosis and loss, it's inhibition should firstly, reduce ECM deposition, limit axonal compression and finally, significantly decrease the level of retinal ganglion cell (RGC) apoptosis and loss. We therefore hoped that the effects of the TGF-β SHIELD™ could next be investigated using our well-established rat glaucoma model, and our unique method of tracking RGC apoptosis in vzvø.[17, 18, 43-46] We chose to use the 4 & 8 μl doses of AA V2 and assess RGC apoptosis in vivo at 3, 6 & 12 weeks after IOP elevation. The sub-Tenon's injection were administered at the of time surgery, and animals were imaged in vivo at 3, 6 & 12 weeks after IOP surgery with histology for confirmation.

Method For the ocular hypertension (OHT) model, [17, 18, 43] the IOP was elevated in the left eye of each animal by injection of 50μl of hypertonic saline solution (1.80 M) into the episcleral vein,[47] using the syringe pump (60 μl/min; UMP2, World Precision Instruments, Sarasota, FL). [18] As evaluated from the previous studies, animals were treated with either 4 or 8 μl of the TGF-β SHIELD™ or AAV-GFP or untreated control, corresponding to viral titres of a) 0.0132 XlO¹² in 4 μl b) 0.0264 xl0¹² in 8 μl AAllll aanniimmaallss rraannddoommllyy i received sub-Tenon injections of TGF-β SHIELD™ or AAV-GFP at the time of IOP elevation.

In vivo cSLO imaging of Retinal Ganglion Cell Apoptosis

Eyes were imaged at 3, 6 and 12 weeks after IOP elevation. Note that we have previously shown that in this OHT model, the time of peak RGC apoptosis occurs at 3 weeks, as we have previously described. [17] Retinal images were collected and a retinal montage was constructed for each eye. The number of apoptotic RGCs labelled by annexin 5 was counted manually by using MetaMorph software (Universal Imaging Corp., West Chester, PA) by observers masked to treatment protocols. The amount of RGC apoptosis was presented by density (number/area) or in comparison to control as a percentage reduction. Mean values were calculated with 95% confidence intervals for the absolute counts. All treatment groups were compared to each other and control using ANOVA.

In vivo analysis of changes in ONH ONH were assessed using both retinal montages [17, 18] and volumetric reconstructions using xl6 magnification. GFP transduction and ONH scleral canal assessment was made using methods previously described by our group.

Results

Effect of TGF-β SHIELD™ at 3 weeks on RGC Apoptosis

3 weeks represents the time of peak apoptosis in this model. At this time point only the 8 μl dose of TGF-β SHIELD™ significantly reduces the level of RGC apoptosis (p<0.05) compared to the control AA V2 group. It also appears more effective at reducing the level of RGC apoptosis compared to the 4 μl dose, although this is not significant. However, it appears that all AA V2 treatments increase the level of RGC apoptosis at this time point. Although this is not significant in terms of the TGF-β SHIELD™ compared to untreated control, there is a significant increase in the level of RGC apoptosis in the AA V2 compared to untreated controls.

Effect of TGF-β SHIELD™ at 6 weeks on RGC Apoptosis

Again, the 8 μl dose of TGF-β SHIELD™ significantly reduces the level of RGC apoptosis (p<0.05) compared to control. Interestingly, at this time point it appears less effective at reducing the level of RGC apoptosis compared to the 4 μl dose, although this is not significant. There is a significant increase in all AA V2 groups increasing the level of RGC apoptosis at this point.

Effect of TGF-β SHIELD™ at 12 weeks on RGC Apoptosis

The results above show a significant (p<0.05) reduction in RGC apoptosis by both the 8 μl and the 4 μl at 12 weeks. Interstingly at this stage, both the untreated and AA v2 controls are similar in terms of levels of RGC apoptosis.

Comparison of 4 μl and 8 μl doses of TGF-β SHIELD™

The only time point showing a significant difference between the viral loads of TGF-β SHIELD™ was at 12 weeks. At this stage the 4 μl treatment appeared to have much greater efficacy.

Anterior and posterior scleral canal opening (ASCLO and PSCLO respectively) diameters were analysed over the study period, using a similar method to that we have previously described. [43] The graph in figure 12 shows the result of the analysis at 12 weeks. No significant difference was found between treatments groups at any of the time points analysed.

Analysis of IOP changes with TGF-β SHIELD™ There was no significant difference between TGF-β SHIELD™ and control over time.

Summary

TGF-^β shield treatment at the ONH appears to inhibit RGC apoptosis induced in our well- established model of chronic elevated IOP, at all time points compared to the AA V2 control. In addition to it being the first time that any therapy has been successfully targeted at the ONH, it shows that TGF- β can be modulated at the optic nerve. Our hypothesis that TGF-β causes changes in the extracellular matrix at the optic nerve head in glaucoma which leads to axonal compression and retinal ganglion cell apoptosis and loss, which its inhibition should reduce, is supported by the findings at 12 weeks in our experimental glaucoma studies. Using our well-established rat glaucoma model, and our unique method of tracking RGC apoptosis in vivo, [17, 18, 43-46] we have previously shown that peak RGC apoptosis occurs 3 weeks after surgical induction of elevated IOP. [17, 28] This is the time-point we have previously chosen to define the neuroprotective efficacy of agents such as MK801 using this same model. [28] An important aspect of this study is the fact that we were seeing significant effects as far down the treatment line as 12 weeks after IOP elevation. This is consistent with our finding that the AA V2 vector had prolonged expression in this mode of administration. Furthermore, it provides evidence that modulation of the ECM at the optic nerve head could be a new method of treatment in glaucoma. We believe the fact that we saw an effect on RGC apoptosis at 3-12 weeks after OHT surgery after a single application of the TGF-β SHIELD is very encouraging. Further, sub-Tenon administration of therapeutic agents is much less invasive than an intravitreal injection. References

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Claims

Claims

1. A method for delivering gene therapy vectors to the optic nerve head, comprising administering a pharmaceutically acceptable composition comprising the gene therapy vector to the sub-Tenon's space.

2. The use of a gene therapy vector in the preparation of a medicament for delivery to the optic nerve head, wherein the medicament is for administration to the sub-Tenon's space.

3. A method for treating glaucoma, comprising delivering gene therapy vectors to the optic nerve head.

4. The method of claim 3, wherein the gene therapy vectors are delivered to the optic nerve head by administration to the sub-Tenon's space.

5. The use of a gene therapy vector in the preparation of a medicament for treatment of glaucoma, wherein the medicament is for delivery to the optic nerve head.

6. The use of claim 5, wherein the medicament is for administration to the sub-Tenon's space.