The Challenges of Drug Delivery for Retinal Diseases - Episode 12
An overview of delivery systems under investigation for retinal disorders and implications for future use.
Albert Augustin, MD: We will move forward and speak a bit about some investigational delivery systems. Let’s start with the…system, which is a suprachoroidal administration device being investigated for triamcinolone acetonide. Dr Korobelnik, can you say a little bit about the results from phase 3 and the treatment strategy in general?
Jean-Franҫois Korobelnik, MD: Yes, there are 2 good points about this option. No. 1, it is a steroid; we are very familiar with steroids. No. 2, it is not in the vitreous cavity, it is suprachoroidal. We probably do not expose the patients to the risk of intraocular infection; these are very positive. It seems that the drug can still go through the retina and be very effective. Of course, we are concerned about the fact that the drug may go through the anterior segment and induce elevated intraocular pressure. Phase 3 trials are, as far as I know, ongoing, and we will look at those results very carefully, both on efficacy and safety. I think it’s interesting; it is something really new that may be an option and a true competitor compared to intraocular steroids.
Albert Augustin, MD: Yes, thank you. At least the way of administration is much easier than in former times where we had to use a catheter. It is quite easy in terms of the surgical approach, so let’s wait and see. Again, the portal delivery system [PDS], just a few more words on this. The FDA application can be expected soon and further countries in the next year or so. Dr Peto, can you speak a little about the ranibizumab port delivery system? We expect that it will deliver the drug for about 6 months; it should be at least equal to injections. Maybe a few words on the ongoing studies?
Tunde Peto, MD: The results are very promising, and that is why we’re expecting reasonably soon that it might be available. It is a refillable system; we will be able to use the same port to give the patient the next dose of the drug, instead of an injection. And every 6 months we would potentially have to see the patients. If we do use this in diabetes, we must think about what happens to the retina and potentially the anterior segment for neovascularization in between. We’ve got to make sure we have relatively good protocols for not [seeing] any patients in between. Because those patients who have had a lot of injections are very used to coming regularly. They might struggle with not being seen as much even if they will enjoy the freedom from the eye clinics. We are looking forward to this delivery system, and we’re looking forward to injecting must less than we do now.
Jean-Franҫois Korobelnik, MD: If I may make a short comment on the PDS; it is very promising. I agree Tunde, however, there is a problem as you said earlier, that it is a surgical procedure to put the reservoir in. You need a vitreoretinal [VR] surgeon, and you need an operating room. VR surgeons are very busy, and operating rooms are very busy; it is going to be a challenge. I cannot imagine implanting reservoirs in many patients. This very practical first step to put the reservoir in the eye is going to be problematic in many places.
Tunde Peto, MD, PhD: I completely agree; that is why I said that we got partly what we wished for, and then we have new challenges we need to overcome. It will be suitable for a subset of patients who cannot get there regularly, and who are struggling with the injections. But I agree, we do not have enough vitreoretinal surgeons to do the operations.
Albert J. Augustin, MD: That is due to them all being busy with injections, and so on. In [previous] times it was much easier. In the interest of time, we will move forward. I would like to have a few words on sunitinib. This is a vascular endothelial growth factor inhibitor applied by means of a microparticle depot. Phase 2A is already completed, macular edema secondary to RVO [retinal vein occlusion]. For phase 2B, we have interim results available, which are also at least a little promising. Dr Korobelnik, can you say a few words on this?
Jean-Franҫois Korobelnik, MD: I do not have personal experience with this new way to deliver drugs. I think that a lot of companies are exploring a way to answer our problem, which is increasing durability of both steroids and VEGF inhibitors. We are looking for long duration, so anything that can help provide a longer duration is fine. I am very careful with phase 1, phase 2A and 2B results. We need to look really in detail at the protocols in the results to be sure that it is promising. Also, investors will have to look at the results before going to phase 3. However, I do not have personal experience with that.
Albert J. Augustin, MD: Dr Peto, do you know a little more about the competitor for Ozurdex, [intravitreal dexamethasone], which is also biodegradable, for patients with macular edema due to vein occlusion or diabetes? The safety and proof of concept study is completed. Do you know a little more that you would like to share with us?
Tunde Peto, MD, PhD: This is the first time that retinal vein occlusion has come up today, and this is a very common problem for the elderly population. However, we also see it in younger people as well. In the UK, we can only give a lot of the steroid products to patients who are pseudophakic. It will be interesting to see if some of these new biodegradable and erodible products might be useful for those who are slightly younger and who might be phakic as well. This would be a new way of looking at it, because you do not have the vessel that takes the drug there, and it would completely erode away. Repeated injections might be less of an issue, and you might have less of a problem as to what to do after 2, 3, or 4 injections if it is an ongoing problem.
Transcript edited for clarity.