Q&A: Peter Kaiser explains the ongoing SOL-1 and SOL-R study of OTX-TKI

Peter Kaiser, MD, from Ocular Therapeutix introduces OTX-TKI (Axpaxli), a novel tyrosine kinase inhibitor delivered through a proprietary hydrogel platform. This innovative treatment for wet macular degeneration offers a unique approach with slow drug release lasting up to 9 months. The company is conducting two phase 3 clinical studies, SOL-1 and SOL-R, to evaluate the drug's efficacy compared to alfibercept, with the goal of providing a more convenient and potentially superior treatment option for patients.

Note: The following conversation has been lightly edited for clarity.

Hattie Hayes, Ophthalmology Times: Can you share an update on the clinical trials of OTX-TKI?

Peter Kaiser, MD: Here at EURETINA, we talked about our product, which is called OTX-TKI or Axpaxli. What is that? For those of you who don't know what that is, it's a combination of axitinib, which is a tyrosine kinase inhibitor. So what a tyrosine kinase inhibitor does is it blocks the downstream activation of VEGF receptors, all 3 VEGF receptors. It's a pan-VEGF inhibitor, and it's placed into our proprietary hydrogel platform. So what does that do? It allows the drug to be released slowly with zero-order kinetics. Starts right away and lasts up to 9 months.

And so we're using this in 2 phase 3 clinical studies, the SOL-1 study and the SOL-R study. There are 2 different studies. So in the past, companies have done 2 identical phase 3 clinical studies, and here at Ocular Therapeutix, we said, what can we do to do things differently? Get the FDA approval that we want, but also give us commercially relevant information, as well as information that physicians would want to use [this product], to decide when will they use our product or not?

OT: What is the SOL-1 study evaluating?

Kaiser: So the SOL-1 study is a superiority study. It's our first study. It will read out in the first quarter of next year [2026]. We're looking at patients who are treatment-naive wet macular degeneration. They get a single injection of Axpaxli versus Eylea, and then they're followed for 9 months, when the primary outcome is at 9 months. So we'll have the results of that study shortly. The nice thing about a superiority study is that allows us, hopefully, to be able to do something different than all the previous studies, which are non-inferiority studies, which, if you're not inferior, that means you're the same as Eylea, and this case, we're trying to prove superiority. So that will give us pricing advantages. It'll also give us the lack of step therapy. A lot of insurance companies in the United States require step therapy.

OT: How does this differ from the SOL-R study?

Kaiser: The SOL-R study is a different study. It's a non-inferiority study, and in this study, we are looking at Axpaxli delivered every 6 months, versus Eylea delivered every 8 weeks. So because of that, we could look at how we do versus other non-inferiority studies that were done in the past. It allows us to look at acute 6-month dosing. The nice thing about that, our drug lasts 9 months. So if we treat every 6 months, the goal would be to have a fixed dosing, where almost all the patients could remain on a fixed dosing. In the past, when someone says a drug lasts 12 weeks or 16 weeks, that means almost half of them don't last that long, and that's the problem. We hope to have the majority of patients stay at 6-month intervals. So that's why we're testing that in the SOL-R study. SOL-R study will read out about a year after the SOL-1 study, roughly. Those two programs that we use for our registration.

OT: What is unique about OTX-TKI's sustained release model?

Kaiser: We have 2 FDA approved products that are of long duration. Port delivery system and the Neurotech [Pharmaceuticals] device, which was just recently approved for MacTel. Those require surgical procedures. So Axpaxli is a single injection delivered through a 25 gauge needle. So it's an in office intravitreal injection. The nice thing about our polymer is it disappears at 9 months, so at the end, there's a release of the free drug. So if you see the polymer in the eye, you know it's still there. That's in contrast to the polymers that we have in the past. So for instance, if you look at Ozurdex, the polymer in that drug lasts longer than the drug, so you may see the implant still in the eye, but the drug has long been gone. We didn't want that because it's very difficult for a retina specialist to know then, when do I need to re-dose a patient. with Axpaxli, if you see it, it's still releasing. It's still active. As it disappears, the drug disappears. Now you know it's time to re-inject.

OT: What should ophthalmologists know about TKIs?

Kaiser: So when we talk about tyrosine kinase inhibitors, there's a lot of companies in this space, which is wonderful because it's been so successful in oncology, and there are a lot of FDA-approved products in oncology, but in ophthalmology, we have no FDA-approved products that are tyrosine kinase inhibitors. People are testing eye drops. They're testing it systemically. We're testing it with our proprietary hydrogel platform. The whole goal of that is, we think that local delivery of the tyrosine kinase inhibitor is really what's required to manage patients with macular degeneration as well as diabetes, so by putting it in the eye, but allowing it to release for anywhere from 6 to 12 months, really is a sweet spot for what retina specialists want.