SUB-urothelial DUrvalumab InjEction-1 (SUBDUE-1) - A Clinical Trial for the Novel Administration of Immunotherapy for Bladder Cancer- Dickon Hayne

March 8, 2021

Several solid tumors, including bladder cancer, can demonstrate good responses to systemic immuno-oncology agents, however, the efficacy of IO agents in localized bladder carcinoma remains less clear, although numerous trials are underway.

In this conversation, Ashish Kamat, MD, MBBS, and Dickon Hayne, MD, MBBS, highlight one such immuno-oncology agent, durvalumab, an antibody against the immune checkpoint protein programmed cell death ligand 1 (PD-L1) in the SUBDUE-1 trial. Sub-urothelial durvalumab injection-1 (SUBDUE-1): A novel approach to immunotherapy for bladder cancer. SUBDUE-1 is the first report of sub-urothelial injection of durvalumab prior to cystectomy, designed as a dose-finding phase Ib trial and funded by the Australian and New Zealand Urogenital and Prostate Cancer Trials Group (ANZUP).

Biographies:

Dickon Hayne, MD, MBBS, Professor of Urology at The University of Western Australia Head of Urology Fiona Stanley Hospital

Ashish Kamat, MD, MBBS, Professor, Department of Urology, Division of Surgery, University of Texas MD Anderson Cancer Center, President, International Bladder Cancer Group (IBCG), Houston, Texas


Read the Full Video Transcript

Ashish Kamat: Hello, and welcome to UroToday's Bladder Cancer Center of Excellence. I'm Ashish Kamat, professor of urologic oncology at MD Anderson Cancer Center in Houston, Texas. And it's my pleasure today to welcome Professor Hayne, all the way from Australia.

Professor Hayne is joining us. He is a professor of urology at UWA and is the head of urology for the South Metropolitan Health Service in Western Australia. He also chairs the bladder urothelium penile subgroup of ANZUP and at the recent GU ASCO he had, or his group had, a presentation called SUBDUE-1, which is a novel approach to immunotherapy for bladder cancer.

Professor Hayne, everyone was really listening with rapture to the presentation, and we thought this would be a perfect abstract presentation for you to bring us and present to our audience, sort of as an off the cuff, or off the regular track discussion. So with that, I'll hand the stage over to you.

Dickon Hayne: Thank you very much, Ashish. So I am going to talk about sub-urothelial durvalumab injection, a novel approach to immunotherapy for bladder cancer.

So in the background, we know that immuno-oncological agents are effective systemically against several solid tumors, and particularly, we are interested in the metastatic urothelial setting where there has been lots of efficacy. But we haven't really had much evidence for the use of IOs in localized bladder cancer in high-risk, non-muscle-invasive bladder cancer, but there is some evidence of some efficacy of systemic pembrolizumab with early data from the KEYNOTE-057 study. And there are some intravesical IO trials in progress, though we don't really have any results to date.

Of course, the urothelium is an impenetrable beast, and these large molecules, they are antibodies. They are very large molecules. I think that is quite unlikely that they will penetrate the urothelium, but interested to see if there's any success there.

Sub-urothelial administration is not reported, and it does have several potential benefits as an alternative treatment option for a very important bladder cancer space, the high-risk non-muscle-invasive bladder cancer space.

There are maybe reduced immunological side effects and costs, compared to systemic IOs. And it's also a mode of administration that urologists are particularly used to, and they are really the ones who manage the non-muscle invasive bladder cancer setting. And we routinely administer drugs in this way, such as botox for an overactive bladder.

So the aims of this study are quite simple, to develop a protocol for the sub-urothelial administration of the durvalumab, assess safety and tolerability, and identify a dose for future phase II studies. We also want to try and examine the potential immunological effects of its sub-urothelial administration, by looking at the distribution and quantity of tumor-infiltrating lymphocytes, and tumor-activated macrophages, in pre-and post-administration biopsies.

So in terms of the methods of the study, it's a dose-finding phase 1b trial. We are including all patients scheduled for cystectomy, who have either refused or were unsuitable, for neoadjuvant chemotherapy. Because this is a first-in-human study, we thought it best to select patients who are due to have the bladder removed, ultimately. So some patients have muscle-invasive, and some have heart risk, there's no non-muscle invasive disease.

The intervention is cystoscopy under GA, and it has to be at least two weeks prior to the scheduled cystectomy, so an extra cystoscopy. And then, pre-injection biopsies are taken from around the bladder and followed by the sub-urothelial injection of the durvalumab . It is a three by three dose-escalation study design, with three doses selected at 25 milligrams, 75 milligrams, and then 150 milligrams, with a plan to do three at each dose range, and then repeat the 150 milligram, if the study proceeds to that dosing level.

The immune therapeutic agent is diluted in normal saline and simply given in [inaudible] throughout the bladder, using a 5Fr bonee needle, down a rigid cystoscope.

Prior to this actual radical cystectomy, some post-injection biopsies are taken to try and obtain light for light tissue. Also, of course, the whole cystectomy specimen is available.

In terms of outcomes, we're looking for adverse events, both local and systemic. Patient-reported outcome measures, including AUA symptom score, and also doing a cystitis score to try and pick up any bladder side effects that might be caused by the administration of the agent. And then also looking at the immune cell comparison between TILs and TAMs on the pre-and post-injection biopsies. Obviously, we'll have the T0 and lymph node status on the patients, so obviously, it was a very small study. And also any visible change in residual tumor burden. So we have cystoscopic maps of the bladder before we do the durvalumab injection, and we can compare that with the post-injection mapping. We will also be able to look at PD1, PD-L1, some serum cytokines, and immune mediators.

This study is registered with the Australian Clinical Trials Registry, and it's funded by an ANZUP Below the Belt grant. We already have ethical approval, and in fact, we've now recruited six of the planned 12 patients, and have planned the next patient, and the study will be up to the maximum dose in the study design. We hope to complete it by Q2 2022. Thank you.

Ashish Kamat: So thank you very much for that presentation, Dickon. It's interesting.  When you were thinking of the study design and the installation of large molecules across the bladder, and the thought came up with the injection in some mucosal, was that proceeded by any animal studies, or did you go straight into human subjects?

Dickon Hayne: We went straight into human subjects. Obviously, these agents are safe in high doses intravenously, and there's a plethora of data about the range of side effects. It's a human antibody, so anti-animal studies may not be that relevant, using a human antibody. And in terms of the actual administration technique of putting drugs, one mil blebs under the bladder, it's a very un-morbid thing to do. So it was decided that there wasn't, there was no need, and little use would be obtained, from doing animal studies first. So yeah, there's no animal data with a sub-urothelial injection that I'm aware of. Well, I'm certain there isn't.

Ashish Kamat: And then, with this window of opportunity study, or phase zero study, in patients undergoing radical cystectomy, it does offer us, and in this case, your team, a huge amount of tissue that you could be looking at, right? So you have the biopsy or the TURBT, then you have your injection, and then at the cystectomy, you would be able to essentially look at all the immune correlates. But as far as the dosing schedule and the duration of treatments concerned, is there any thought based on what you've seen so far, or an expansion, to more dosing of the drug, to allow you to actually see some anti-tumor effect?

Dickon Hayne: Yeah. It's an absolutely fair question, Ashish. I mean, we don't know yet. We haven't in terms of analyzing, and I certainly couldn't talk about it at this point, in terms of analyzing, whether there is even a demonstrable immune-mediated response that we can see. The main point of this study is to prove that it is safe and effective. And again, the reason we chose for all, we weren't, of course, it was unknown whether injecting these agents in the bladder would cause extremely unpleasant, or other concerning bladder side effects, in which case it probably would be abandoned as an option.

There was a great deal of discussion about the dosing, where to start, and which dose levels to pick. And that was debated amongst most of the medical oncologists and ANZUP, I think, I had a hand in that discussion. And we went for these dosings based on estimates of the concentration you may get in the bladder, compared to a systemic concentration. But you're right, it is difficult to know where would be the right place to start. And for the purposes of phase IIs, if there is no serious injection-related morbidity, or immune-related side effects, at the 150-milligram dose, then that's probably, well, that will be the dose that we take to further phase II studies. But there may have been others, of course, which there may need to be other dose findings or other work that is done down the track. It's really a proof of principle. Is it something that we can do? Is it safe? And are we seeing any immune effects when we do it?

Ashish Kamat: Okay, great. I'm sure you're aware of the different studies that are ongoing, both at the pharmaceutical and investigator level, to reformulate some of these IO agents, and see if we can actually get them installed intravascularly. As you mentioned, obviously, they're antibodies, and the formulation, and the diluent, and so on and so forth, would need to be fine-tuned. But assuming that the injection obviously gives you a higher dose of the agent in the wall of the bladder itself, do you then foresee, and again, we will just assume your study is positive in a good way, do you then foresee this as a replacement for cystectomy in patients that have the invasive disease, or is this a new adjuvant paradigm that you are looking to pursue?

Dickon Hayne: No. So just to clarify, my personal opinion is that this will have a role in the high-risk non-muscle invasive bladder cancer setting, as a strategy to avoid the need for cystectomy. Now, that's only a proposition at this stage, but I doubt that this will be a useful therapy for muscle-invasive disease requiring cystectomy. And I think it is likely that it would be something that could be applied in the BCG resistant, or the BCG unresponsive setting, as an alternative to cystectomy, possibly in addition to other agents intravesically, possibly in addition to BCG or other immune therapies. So I think it's really only a very baby first step in this area, to see whether this is actually going to be a therapeutic option at all.

Ashish Kamat: Okay. And again, you said you had accrued five of the 12 patients already. Is that correct?

Dickon Hayne: Six, actually. Six.

Ashish Kamat: Six. I'm sorry. I was just going to ask you if you've already performed, or if they have undergone radical cystectomy already, have you noticed any unusual findings during the surgery itself?

Dickon Hayne: No, not at all. No. There hasn't been any, nothing about the cystectomy. So also, they have another cystoscopy immediately prior to the cystectomy, in order to see. So if there was an obvious change, like if all the bladder tumor had magically melted away with a durvalumab injection, then we can see that cystoscopically, and certainly, that hasn't happened. We haven't looked in any bladder and thought, "Well, there's obviously no disease here now.", and I wouldn't really have expected that. But we have that, we have those cystoscopic maps to see if there is any change in the look of the urothelium. But of course, yes, we've got the whole bladder specimen to examine. And we also can go back to the original TURBT specimens that were taken prior to the enrollment in the study. So there is a lot of tissue and a lot of work to potentially look at.

In some of the patients... I don't really want to talk anecdotally, because it's a small study about whether we might have seen some exciting immune changes within some biopsies in some patients. It certainly hasn't been, analyzed that data, or looked at in any formal way at this point, and we were keen to wait until the end of the study before we do that. The study is not really, it's a small phase 1. It is really looking at the possibility, is this safe? Is it safe to do this? And if it is safe to do it, then we will be looking at further studies down the track.

Ashish Kamat: Absolutely. You said that your personal bias is to see if this could be used as a treatment for patients who have non-muscle invasive disease, BCG unresponsive, or maybe even in earlier phases. Have you considered how you might be ultimately targeting these tumors? So in other words, in patients that have CIS, for example, would you pretty much just inject it all into different areas of the bladder, using Blue Light or whatever, or would you just focus on the actual papillary tumors, and inject them at the base of the resection?

Dickon Hayne: Okay. Again, it's another good question. The idea of 25 one mil sites is, the main experience was giving us sort of bladder wide distribution of the drug is with botox. And with botox, the doses sometimes change, depending on the severity of symptoms and the clinical indication, but it is basically 20. Most people use 20 mils of injection around the bladder as an approximate coverage, and you can access most areas of the bladder fairly easily. The reason we went for 25, as in botox, you do not include the trigone as a bladder. It is a bit of an arbitrary amount, but we wanted to ensure that there was some coverage across the bladder.

Now you are not going to be able to evenly distribute the drug perfectly across the bladder. So unless the immune therapeutic effect is more widely distributed than just the injection site, then it may not work very well. I think no one knows whether or not that will be the case at all.

Ashish Kamat: Right. Right.

Dickon Hayne: But just on that point, in terms of actually administering it, and the practicalities of it, you can administer botox down a flexible cystoscope under local anesthetic. So it is quite possible that the repeated, and I suspect it would need to be repeated, immune therapeutic drug injection could be done, even in an outpatient setting under local anesthetic, because it is very well tolerated with down effects for cystoscope, or maybe some light sedation. So it's not a major procedure, even if you had to give the dosing repeatedly, which I would imagine would be the case. And you probably, if you were going to think of a schedule, then you would try and fit the schedule around the cystoscopic examination that should occur in a patient during the course of, for example, immune therapy of BCG for high-risk non-muscle-invasive bladder cancer. So you'd have, those patients would have at least four cystoscopies in their first year of treatment to check for occurrence. And if you were repeated dosing, an agent like this, those would be good time spots to do that.

Ashish Kamat: Yeah. Again, I want to commend you for embarking on this innovative way of delivering IO therapy into the bladder.

Dickon, this has been a wonderful discussion. There are obviously so many more questions I have for you, but in the interest of time, maybe I could just ask you to share with our audience your closing thoughts.

Dickon Hayne: Systemic immune therapeutic agents for a non-invasive, or localized disease, is quite a paradigm shift. And certainly, these agents at high dose systemically have significant risks and side effects. If there was a more localized way of delivering these agents that have been so efficacious in other treatment settings, then that would be highly desirable. So of course this is a very, very early stage in this path, but hopefully, it may be something for the future.

Ashish Kamat: I agree with you there, fingers crossed.

So again, thank you so much for taking the time to be part of this important educational activity. Stay safe and stay well.

Dickon Hayne: Thanks very much, Ashish.
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