Good morning, and welcome to the enGene Therapeutics LEGEND Pivotal Cohort update. At this time, all attendees are in a listen-only mode, and a question-and-answer session will follow the formal presentations. As a reminder, this call is being recorded, and a replay will be made available on the enGene website following the conclusion of the event. I'd now like to turn the call over to Lauren Hofstra, Executive Director of Investor Relations at enGene Therapeutics. Please go ahead, Lauren.
Thank you. Good morning, and thanks, everyone, for joining our call to discuss the data we press-released this morning from the pivotal cohort of our ongoing phase II LEGEND trial of detalimogene voraplasmid or detalimogene in high-risk BCG-unresponsive NMIBC patients with carcinoma in situ. The company recently posted a slide deck on its website, which we'll refer to during this call. These slides are available on the Events and Presentation section of our website. Joining me on the call this morning are Ron Cooper, Chief Executive Officer, Hussein Sweis, Chief Medical Officer, and Amy Pott, Chief Global Commercialization Officer, and Ryan Dodds, our Chief Financial Officer. Before we begin, I would like to remind you that during our prepared remarks and Q&A session to follow, we may make forward-looking statements for purposes of U.S. Canadian security laws.
These statements include, but are not limited to, our current expectation regarding the potential benefits of detalimogene, timing of clinical data, timing of regulatory submission, and the prospects for regulatory approval of detalimogene. They involve risks, uncertainties, and assumptions that are difficult to predict and may not prove to be accurate. Results may vary. These statements should be considered only in conjunction with the information in our filings for Canadian and American securities regulators, including our Risk Factors section of our annual report on Form 10-K. At this time, I'll turn the call over to Ron Cooper, enGene's President and CEO. Ron?
Great. Thank you, Lauren, thanks to all of you for joining the call. Our primary focus today will be to review the latest data from LEGEND's Pivotal Cohort 1, an overview which was press-released this morning and will be presented during a plenary session at the American Urological Association annual meeting next Friday, May 15th. As most of you are aware, we announced that we had completed enrollment of 125 patients in Cohort 1 last year and provided a preliminary data update. It focused on detalimogene's excellent tolerability, ease of use, and the improvements seen in complete response rates from 62 of 94 patients enrolled following a protocol amendment implemented in the fourth quarter of 2024. Data from this update demonstrated an improvement in any time three- and six-month CR rates compared to the pre-protocol amendment patients.
As of the November 2025 update, there were 32 patients enrolled under the amended protocol who had not yet reached their first disease assessment. In today's data update, you will see that these patients did not respond as well as the initial 62 patients. Preliminary analysis did not show a material difference seen across patient characteristics during subgroup analysis. Following the November 2025 update, the overall reinduction success rate was lower, and fewer patients opted to undergo reinduction. Work is already underway to conduct a deeper review of the data. Now, that being said, detalimogene's current CR at any time, our primary endpoint, and the Kaplan-Meier estimated 12-month CR rate are currently tracking within range of approved products. The data are not yet fully mature, and the durability picture is incomplete.
Given the compelling tolerability profile and ease-of-use benefits for busy urologists, we plan to await longer-term durability data for all of Cohort 1 in the second half of the year and continue our ongoing discussion with the FDA regarding both our statistical analysis plans and plans for potential BLA filing. As Amy will touch on shortly, our ongoing market research continues to show that there's both a desire and a need from urologists and patients alike to have additional bladder-sparing options that are tolerable, easy to use, and reduce the overall burden for patients. I'll now turn the call over to Dr. Hussein Sweis, our Chief Medical Officer, to discuss our preliminary data in greater detail. Hussein?
Thank you, Ron. Beginning here on slide four, we thought that it's beneficial to give you an overview of exactly where we are in LEGEND at this point in time. As Ron noted, the data we are outlining today is still preliminary and follow-up is ongoing. As you can see from the CONSORT diagram, we enrolled 125 patients, with 124 having completed the three-month assessment. This diagram illustrates patients at different stages of the ongoing study, with a number of patients still awaiting nine- and 12-month assessments. Slide five is an overview of Cohort 1's patient demographics and disease characteristics. The median age was 71 years. Just over 80% of the population was male, and the median number of BCG doses received prior to enrollment was 12.
As highlighted on the slide, our patient population as a whole has a number of high-risk characteristics. Almost 40% had CIS plus papillary disease, and 25% received prior therapy other than BCG. While the median number of NMIBC recurrences was two, some patients had recurred as many as 11 times prior to enrollment. On slide six, I'll cover a topic we believe to be very important when treating high risk NMIBC, which is tolerability. Detalimogene's favorable safety and tolerability profile has remained consistent throughout our trial, with 55% of patients experiencing a treatment-related adverse event, most of which were mild, Grade 1 to 2, localized and resolved quickly. The most frequent TRAEs were fatigue, dysuria, pollakiuria, micturition urgency, and bladder spasm. Only six patients had a Grade 3 or greater treatment-related adverse event, all of which resolved.
The tolerability profile is best illustrated in the low treatment discontinuation rate due to TRAEs of 2.4% and the similarly low treatment interruption rate due to TRAEs, which was also 2.4%. We believe tolerability plays an important role as providers and patients assess their treatment options. BCG, as well as other agents, can be highly irritating to the bladder, and toxicity can be cumulative over time. On slide seven, I will cover efficacy. The following table is representative of Cohort 1's population in its entirety. With one of the 125 patients dropping out prior to the first post-baseline assessment, we have a total of 124 evaluable patients at the April 21st data cutoff. Complete response at any time was 54% and 43% at the six-month evaluation.
Of the 52 patients who were responders at six months, at the nine-month assessment, 37 of 44 evaluable patients were in CR, with nine patients pending their evaluation. At the 12-month disease assessment, we had 13 of 22 evaluable patients in CR, with 11 patients pending their 12-month assessment. While you can see that we have provided complete response rates at nine and 12 months of 33% and 13% respectively, these datasets are still immature and thus we have also provided the respective Kaplan-Meier estimates. We plan to provide an update on these longer-term CR rates in the second half of this year. I will remind you that this is a data analysis at point in time, and it will evolve.
For example, there is a patient that at the nine-month assessment had a non-CR according to the database, but has since been confirmed and updated by the investigator to be in complete response. As you can see on slide eight, the 32 patients who had not yet undergone their first disease assessment as of November 2025 Cohort 1 update had an anytime CR rate of 39% and 32% at six months. This is lower than the anytime CR rate and the six-month CR rate that previously reported in both the pre-amendment and post-amendment subpopulations that have been previously reported. This also results in a marginal overall difference between our pre and post-amendment subpopulations.
There were no discernible differences between demographics or disease characteristics of this subgroup of 32 patients from those previously enrolled, and we are undertaking further analysis to see if we can determine a reason for the lower response rates seen in this population. We designed detalimogene to meet the unique needs of community urologists and are continually looking for ways to improve efficacy and increase convenience. On slide 10, I'd like to discuss the use of bladder wash to potentially improve efficacy and reduce dwell time. Our proprietary sugar or DDX, is designed to penetrate the mucosal layer and transfect the urothelium. A surfactant bladder rinse can disrupt the mucosal barrier and further increase DDX penetration and transfection. Other products have used surfactants to increase the magnitude and duration of transgene expression.
On slide 11, we have now data from multiple preclinical models which show that a five-minute bladder rinse with polidocanol, an approved sclerosing agent, achieved a 10-fold increase in IL-12 expression over a two-week period, shortened dwell time, and improved efficacy. Given the strong preclinical data, you will see here on slide 12 an overview of a new cohort we recently added to LEGEND incorporating this bladder rinse. We now have 20 trial sites activated and screening is underway to enroll up to approximately 80 patients. While the dosing frequency of detalimogene given at weeks one, two, five, and six will remain the same, you can see that the total overall dwell time has been reduced from 60 minutes to 30 minutes, reducing the burden on patients to hold treatment in their bladders, which can often be challenging given reduced bladder capacity and elasticity due to aging and disease.
In summary, while these data are still preliminary, detalimogene continues to demonstrate favorable tolerability and clinical activity in a heavily pretreated high-risk patient population, with disease progression being rare. While we acknowledge that the patients assessed following our October 2025 data analysis had lower CR rates, we await expected top-line data in the second half of this year and plan to conduct a thorough analysis and discuss our findings with the FDA. In the meantime, we're also underway with enrollment of our surfactant bladder rinse cohort, and we plan to provide an update on expected timelines for enrollment and data once we are able.
I'll now turn the call over to Amy Pott, our Chief Global Commercialization Officer, to discuss some more of the insights we have uncovered from our ongoing market research. Amy?
Thanks, Hussein. Our commercial team have been conducting in-depth market research, the results of which have been confirmed and built upon our key assumptions for the HR-NMIBC market. First, on slide 14, while we previously confirmed our thesis that the vast majority, over 80%, are being seen in community settings, which include small private practices, large urology group practices or LUGPAs and health systems and hospitals. What we are now seeing in our survey data are the stark differences in resources and abilities to manage patient flow and treatment effectively. The typical urologist in a small private practice manages an average of 12 NMIBC patients, compared to just six by an academic. Yet academic centers have a patient-to-procedure room ratio of 10 to one, compared to 24 to one for a small private practice and 19 to one at LUGPAs .
These smaller practices are overwhelmed with patient load, have fewer resources to manage these patients, resulting in high opportunity costs for clinician time and facility use. On slide 15, we surveyed 100 urologists across practice settings, the results of which indicate that less than half of urologists across all settings are prescribing novel branded therapies. As noted, some urologists practicing in smaller settings will prescribe and treat patients with novel products, are often forced to refer patients to local hospitals or other providers in order to administer therapies that require more infrastructure than available to them at their practices. In turn, this means that the urologist is unable to benefit from potential buy-and-bill revenue. On slide 16, you can see that two of the key reasons for limited use of these new therapies include the difficult logistics and acquisition costs.
On slide 17, detalimogene is uniquely suited to solve the challenges for community urologists. For busy resource-constrained practices, this could open up a new opportunity to recognize optimal access and reimbursement, such as buy-and-bill. With that, I'll turn the call back over to Ron.
Great. Thanks, Amy, and thanks, Hussein. I'd like to close by making a few points here on slide 18. As Hussein mentioned, our plans are to complete the pivotal core, enroll the study incorporating surfactant bladder rinse, and engage with the FDA with the final pivotal core results. One way to think about that engagement is to draw upon efficacy and durability points of recently approved products. For example, you can see that our CR at any time of 54%, Kaplan-Meier estimated 12-month landmark CR rate of 25%, and median duration response of 8.7 months are aligned with Adstiladrin. The current 12-month duration response KM estimate is 25%, with a 95% confidence interval of 11%-41%. Again, longer-term data remain immature at this point and are subject to change with additional analysis and time.
The emerging profile of adalimumab is starting to become clearer. The tolerability profile remains attractive, with most of the AEs being mild and predominantly associated with catheterization. Our updated data demonstrates efficacy, but it is at the lower end of our expectation. It is preliminary and will evolve as we complete the study. Based on the results of our preclinical models, we believe that a surfactant bladder rinse combined with adalimumab could improve efficacy and reduce dwell time. This study is enrolling, and we look forward to sharing the data. What's clear from these recent market research and survey insights is that community urologists have the fewest resources, their adoption of the newer agents remains low, and that there is a place for a product that does not have burdensome logistics and can be easily acquired.
As the only non-viral gene therapy, detalimogene has the advantage of being stored for years in a regular freezer and for months in an office refrigerator. We've recently completed all of our at-scale FDA validation manufacturing batches and anticipate having the lowest cost of goods across NMIBC immunotherapies. Detalimogene could meet an important need for the busiest community urologists if ultimately approved. Thank you for joining the call today to discuss this preliminary analysis. We're looking forward to the plenary session at the upcoming AUA meeting and engaging with the medical community. Operator, I'd like to now open the call for questions.
Great. Thanks, Ron. Yes. At this time, we'll be conducting a question-and-answer session with our speakers. Please hold for a brief moment while we pull for questions. Our first question comes from Maury Raycroft at Jefferies. Please go ahead, Maury.
Great. Thank you. Thanks for taking my questions. Maybe just starting off, wondering if you'd talk more about the path forward from here and how we should think about next steps for FDA engagement. Can you also remind us how you view FDA's latest thinking on the potential for a single arm study for registration and whether they've commented on a specific efficacy bar?
Maury, thanks very much. I'll take both of those questions. Let me take the second question first, right? I think from a single arm perspective, remember that the FDA in this category issued draft guidance in 2018 and in 2024 reiterated that draft guidance. Since that time, you know, our product has been approved in this pathway. This pathway is not an accelerated approval, it is a full approval. It's different from some of the other, you know, issues that have occurred with accelerated pathways. We believe this pathway is, you know, intact. Of course, you know, we've had a lot of dialogue with the FDA given that we have RMAT status and CDRP which are, you know, unique, right, and real honors for us.
If I look at our engagement with the FDA, they have been very much engaged with us. I think we feel that the path is strong. As in regards to engagement with the FDA, you know, we have had a, you know, a number of engagements with the FDA, particularly because we have this RMAT status and CDRP. We've been having a good dialogue around our manufacturing, you know, given that we have finished our PPQ batches or the FDA validation batches. That is ongoing. As it relates to the data, you know, our plan is to continue our dialogue and the statistical analysis plan. We're back and forth with the FDA on that, and we'll finalize that over time.
Once this data set matures, the cohort one data set is fully mature, you know, we'll engage with the dialogue with the FDA. Thanks for the questions, Maury.
Okay. Presumably that engagement would probably be later this year then. Is that kind of the second half?
Yeah, exactly.
Part of the second half plan.
It'll be part of the second half.
Okay. Then maybe just a question on the heterogeneity in response that you're seeing. Appreciating that it's still early data, do you have any visibility into what may be driving the differences observed amongst the newly assessed patients? Presumably it seems like you think it could be something related to expression. Do you have any evidence indicating this?
Yeah. As I mentioned during the presentation, we did a preliminary subgroup analysis looking into the key disease characteristics and demographics. We did not so far identify any factor that could have contributed to the worst outcomes for patients in the last in the last group of patients, the 32 that we referred to. That work is still ongoing. It's still preliminary what we have reported so far. As we learn more, we will inform.
Got it. Okay. Thanks for taking my questions.
Thanks for the questions, Maury. Our next question comes from Mani Foroohar at Leerink Partners. Please go ahead, Mani.
Hey, thanks. A question. How do we think about when we're gonna get more data on further follow-up from this cohort, including, your own investigation into potential drivers of a differential CR rate? Secondarily, on what time horizon will we expect to see a little bit more information on the impact of surfactant bladder wash?
Yeah. You know, thanks, Manny, for the question. You know, as we said before, this is a preliminary data cut. You know, the data is still immature. We'll be waiting for the data to fully mature. We expect that in the second half of this year. We'll update the market our plan is update the market once that data is available. As it relates to the surfactant bladder wash, you know, this is a concept that we've been working on for many years. We're pretty excited about the potential of a simple bladder wash. It needs some time to actually select the right bladder wash. We're really pleased to be up and going with 20 sites. You know, screening is occurring.
Once we have a better handle on where we are with enrollment, we'll then update the market as you know we expect data.
Okay, that's helpful. As a, as a quick follow-up, on Maury's earlier question around engagement with the FDA, would it be reasonable for us to expect further, a further update from you guys on timing of your ongoing engagement with the agency? Or is that something that wouldn't happen until after a fulsome and complete data from LEGEND, later on this year?
Yeah. I think the better way to think about it is after we've completed the LEGEND pivotal cohort, you know, that's when we'll be able to give more color on that.
Okay. Thank you.
Thanks for the questions, Mani. Our next question comes from Jeff Stantial at Wells Fargo. Please go ahead, Jeff.
Hey, this is Jeff on for Yanan. Thanks for taking the questions. Just thinking about approvability based on precedent. The Adalimumab trial I don't think allows reinduction. Is a 12-month CR rate of 25% in a trial with reinduction in the protocol sufficient? Have you had that type of conversation with the FDA in the past?
Well, I'm not sure I'm tracking you 100% here, Jeff, but, you know, the reality is these products are all sort of individual approaches. We have an individual discussion, you know, with the FDA, they know that, you know, our therapy is a different therapy, right? When you think about reinduction, some products, there's an intense period, and then you reinduce. You know, our medicine is almost like a continuous medicine, like every quarter for a year, and that is actually similar to [XELJANZ], right? I think we feel pretty comfortable that, you know, our trial approach, how we provide the medicine to patients is in concert with what the FDA expects.
Okay. Then, did you analyze the, any time of six-month CRA for the pre and post patients similar to what you did in the November readout, or will you share that at AUA?
What we analyzed is ultimately as a result, now that we have presented the totality of the data, we looked specifically at the last batch of patients and where we saw the lower CR rates. Now if you look at the results, the difference between the pre and post amendment as we have presented back in November last year is no longer as significant because the complete post-amendment population is no longer a population of 62 patients, but now 94 patients that includes the last batch of patients. That difference is no longer as significant as we had initially seen, which was, as you know, based on smaller sample sizes as well.
Okay, got it. Thanks for the color.
Thanks for the questions, Jeff. Our next question comes from Allison Bratzel at Piper Sandler. Please go ahead, Allison.
Hey, good morning, guys. One for me, on safety. Could you just expand on the Grade 3 and higher, treatment-related AEs you observed? I think one of the footnotes talked about a Grade 4 ALT elevation, so just wondering if you could expand on that. Then, secondarily, Ron, I think I heard you say that fewer patients elected to undergo reinduction in this latest data cut. Could you just expand on that and, you know, do you have any sense, why that is and if that explains much of the difference, compared to the October data cut? Thank you.
Allie, you know, thanks for those questions. Let me take the second question first, and then Hussein can take the first question. The way that detalimogene is administered after three months, if you are a CR or a non-CR, you're supposed to be dosed at the six-month timeframe. Obviously, those patients that are CRs and get dosed at the six-month timeframe can go on from there. If you are a non-CR, you are supposed to, according to protocol, be redosed, right? We can't force patients to do that, right? There were a number of patients who elected to leave the study instead. Now that is a protocol. That's against the protocol. We would have preferred that they continued on.
You know, again, you know, this is subject to what people want to do, and so we can't control that. Hussein for the first question.
In terms of the Grade 3 Treatment-Related Adverse Events, we had a total of six , which is out of 125 patients. About 5% of patients had Grade 3 TRAEs. Of these, only one had a Grade 4 TRAE, which as you mentioned, was the elevated ALT, which is a liver enzyme. As you may know, Treatment-Related Adverse Event is a subjective assessment provided by the investigator, based on what they think. Oftentimes there could be lab abnormality. Ultimately, this is a lab abnormality which the investigator, you know, associated, thought it could potentially be because of detalimogene. We, as a sponsor, do not necessarily believe this is the case, but obviously we reflect the data as the investigator has entered in the database.
It may change down the line if the investigator changes their assessment. What we can say is that it has resolved, and it did not lead to discontinuation. We feel very confident about the safety profile of detalimogene, and we don't think that these limited Grade 3 TRAEs are problematic.
Great. Thanks for the questions, Allison. Our next question comes from Michael Schmidt at Guggenheim. Please go ahead, Michael.
Hey, guys. Good morning. Thanks for taking my questions. Maybe just going back to the regulatory question. You know, I think you know, it sounds like there's obviously recent precedent and strong belief that the single arm study regulatory path is still open for NMIBC. What about the efficacy bar? When I look at recent approvals, studies, single arm studies were designed to exclude a 20% CR, so the lower bound of the 95% confidence and a lot of which you obviously clear in the study. My question is, do you think that CR bar is still applicable today given that, you know, there has been new approvals in the space? How should we think about the bar for duration of response from a regulatory perspective?
Thanks for the questions, you know, Michael. You know, I don't wanna speak for the FTI, right? You know, let's, you know, let's think about how the FDA thinks about these things. First of all, you know, they think about these submissions in unique, discrete datasets, right? It's manufacturer by manufacturer. Detalimogene is the only non-viral approach that is being developed, you know, for this space. The first responsibility for the FDA is around safety, right? I think that, I think we've demonstrated a pretty compelling safety profile with detalimogene. You see that manifest in the very low rates of treatment discontinuations and the very low rates of treatment interruptions. That's the first hurdle. The second hurdle is in regards to efficacy.
There again, you know, the FDA does not give you know, any efficacy bars. Again, it's in the context of this filing and not in others. I shared with you some data that shows that, you know, we're in line at this time frame, you know, with other approved agents. In fact, you know, this will change over time, right? As we finish the other study. The third thing that the FDA looks at is at manufacturing, right? From a manufacturing perspective, you know, can you do this consistently? Is the product safe? How is it handled? Et cetera, et cetera. As I indicated earlier, we've completed our PPQ batches or the FDA validation batches.
We've had a good dialogue with the FDA, and so we feel pretty good about that. You know, it would be inappropriate for me to speculate about the FDA in terms of, you know, approvability, but I think hopefully I've given you some context, and we will have a dialogue with them later this year.
Okay. Maybe just following up on your sort of market research, work, you know, if approved, obviously with this profile and all the features of the product, you know, how do you think this could slot into the treatment paradigm relative to other available therapies in NMIBC?
Thank you for that question. You know, I think the market research and our survey data has indicated that, you know, urologists managing the most number of patients have the fewest resources. In general, you know, we've seen low uptake of new therapies with these urologists, but we know they'd like to incorporate novel therapies into their practice. I think given detalimogene's ease of use, tolerability, our low rate of progression seen to date, it could be a useful tool in their kit, you know, with which to offer a bladder sparing option to patients. As detalimogene offers the urologist the opportunity to offer a bladder sparing option, they will know how quickly it works. Given the tolerability profile and the low risk of progression that we've seen to date, it should have a minimal negative impact on patients.
We believe it slides easily into practice flow without consuming those additional resources. We believe there's a place for detalimogene.
Thank you.
Thanks for the questions, Michael. Our next question comes from Judah Frommer at Morgan Stanley. Please go ahead, Judah.
Hey, guys. This is Nick on for Judah. Can you hear me okay?
We can hear perfectly, Nick. Thank you for joining us.
Great. Yeah, thank you. Thank you so much for taking our question. Just on the protocol amendments, we've talked a bit about the reinduction data, but, can you help us with any potential impacts you might be seeing from the other amendments? Did you see any positive effect from that, confirmation, that requirement to get a biopsy confirmation before discontinuation? Apologies if I missed that in the prepared remarks.
No worry. Maybe going back to the protocol amendment. Ultimately, back in November, this was a hypothesis that we felt, you know, could justify and explain reasonably why we were seeing a difference between the pre-amendment population and the post-amendment population based on the smaller sample size and limited follow-up that we presented back in November. But as mentioned, now that we have a larger database with more patients and longer follow-up, those differences between the pre-amendment and post-amendment are marginal. We don't know as of now what the reason is for the difference in that last batch of patients. But in the totality, that difference has not materialized as we had initially anticipated.
That being said, we do believe that the changes that were made in that protocol amendments were clinically relevant. As they're supposed to improve and they have improved the patient selection to make sure that they are aligned with the AUA guidelines. Have we seen that difference based on the comparison of pre and post-amendment? At this point, based on the totality of the data that we have, we're not seeing that.
Gotcha.
As I mentioned also before, we're still at the beginning of this activity, and we will be conducting further and more detailed analyses, and we will update you once we have more information.
That's helpful. Thank you. Maybe just one more on the SAP plan. I think you had planned to just engage with the FDA on which patients might be included in the final efficacy evaluable population. Can you just share latest thinking on that? Did kind of the latest data change anything in that regard?
Nick, I'll take that question. You know, look, you know, when you are fully enrolled in a study, it's normal to start engaging with the FDA on your statistical analysis plan. This is a back-and-forth process. We have submitted our proposal to them and they will come back with us with something. We will do sensitivity in subgroups. It's a dynamic process. I think at the end, though, we will expect a number of patients to be censored from the 125. We do not know what that is as yet. That will change the denominator and will have an impact, you know, on our efficacy rates.
Got it. Thanks for taking the question.
Thanks Nick.
Yes, thanks for the questions, Nick. Our next question comes from Sean McCutcheon at Raymond James. Please go ahead, Sean.
Hi, guys. Thanks for the questions. Can you speak to the conversion rate from three to six months and whether you think perhaps a higher dosing intensity, similar to what we've seen for other programs in a true reinduction versus continued therapy, you know, would have made a difference? Could you provide any commentary on proportion of T1 patients in the population enrolled post October 2025? Thanks.
From a reinduction rate perspective, as mentioned, we saw that six patients were successfully reinduced. If you compare this with what we have disclosed back in November, we had four patients that were successfully reinduced. In total, the total number of patients that were successfully reinduced is at 14%, which is lower than what we had originally anticipated. Now as to what the reason for this is, we are yet to analyze and study this further. For sure, and this is independent of this outcome, we have constantly been working on continuous improvement of detalimogene and finding ways to make this product even more attractive.
This includes the surfactant bladder rinse, which as I've shown in the preclinical data, introducing the bladder rinse does increase the transfection efficiency and the expression of biofilm. We do believe that this could be a very attractive addition to detalimogene and could improve the efficacy as a result of the surfactant addition. More to learn about this, but we believe we have potential things that could optimize detalimogene further.
Great. Thanks for the question, Sean. Our next question comes from Chiara Montironi at Kempen. Please go ahead, Chiara. Chiara, you might be on mute.
Sorry. Here I am. Hi, team. Thank you for taking my question. I have two, if I may. The first one is how much the pre-amendment data weighted on the durability metrics that you are reporting. Basically, how many of these patients with long-term assessment derived from the pre-protocol amendment cohorts? The second one is around the timelines for the BLA. How does the surfactant study, how should we expect the surfactant study will impact the timelines for the BLA? Thank you.
Thanks, Chiara, for joining us. Let me take that second question first, and then Hussein will take the 1st question. The surfactant bladder rinse studies are independent of the BLA filing. Our plans are to complete cohort 1, mature, today this is a preliminary look at the data. There's still much more data to come over time. Mature the data and have a discussion around filing detalimogene on the basis of cohort 1. We would see the surfactant bladder rinse work as formal lifecycle management opportunity. We're pretty excited. We think that, looking at our preclinical models, that this can help to boost efficacy, but also you make it even more convenient for the patients and for the practice.
We're looking forward to enrolling that study and sharing that data with you at a later time. Hussein?
To answer your question, Chiara, on durability, I think the first thing is just to emphasize that durability data that we have so far is still preliminary. This is also reflected in the confidence interval that we shared for the Kaplan-Meier estimate, which has a upper boundary that goes into 40% approximately. The other piece to compare between the pre-amendment and post-amendment patients, obviously the pre-amendment population, which, and that amendment was from 2024, that data is mature. As we have disclosed back in November of last year, those patients from a durability perspective, did not perform as we had hoped, with a 12-month CR rate, which were lower than those of approved products.
That being said, the we still at this point, if we look at the totality of the data, have about 21 patients where that are still ongoing. 19 of these 21 patients have a CR at nine months or at six months, and they're still pending their next assessment. We also have two patients who are who are being reinduced and are pending their six-month assessment. The longer term durability for the post-amendment population is still preliminary and still outstanding, and there's more to learn about this. We look forward to seeing that data that will further characterize the efficacy and durability results of detalimogene.
Yeah, thank you very much. If I can just ask for more clarity. The data that you're reporting on durability will be together, right? Both pre and post together.
That is correct. You know, given Hussein's comments now that, you know, the post-amendment patients are so much larger than the pre-amendment. You know, they now represent a smaller population. We're now at a point where.
Yeah.
We put them all together.
Yeah. Yeah. Thank you.
Thanks for the questions, Chiara. Our next question comes from Andres Maldonado at H.C. Wainwright. Please go ahead, Andres.
Hi, guys. Thank you so much for asking me and taking my questions. Just two quick ones from us. Ron, you had commented that, you know, the use of a surfactant was always kind of something that you guys had thought about. Can you just talk a little bit more about the historical data that supported perhaps the initial decision, you know, to move forward without a surfactant rinse? I guess in that same regard, would you expect there to be a more amenable maybe tumor morphology or certain type of tumor geometry that would be more susceptible to this surfactant treatment versus So comment on, you know, if it's more effective in CIS given than from surface versus Ta versus T1.
A secondary just side note, would be great if you guys could talk about a little bit more, you know, beyond the baseline differences, you are assessing in terms of, you know, outside of the basic demographics, you know, is there any other kind of demographic that could really drive the narrative here about why the data kind of has such a large delta? I mean, can the data gap be closed by, you know, having looking into site level effects, you know, maybe unique urine cytology, some kind of inflammatory markers? Thank you very much.
All right. Well, thank you for those questions, Andres. We're going to have to put you on the team with us to help us with this data analysis. You know, first of all, you know, to your questions around the surfactant bladder rinse, right? You know, the original design principle for detalimogene was to have the simplest product, you know, for both urologists and patients. Based on our phase I data, I think we felt pretty good about where, you know, where our efficacy and tolerability set. We always have intended to think of ways we could make detalimogene even more efficacious and convenient. While we were conducting the phase I portion of the LEGEND, preclinical work evaluating various surfactant bladder rinses, you know, was initiated.
Frankly, we and our advisors became excited by the potential of drastically reducing the total time and thereby improving the patient and practice experience. A number of different surfactant rinses were evaluated, and that took some time prior to selecting, you know, polidocanol. Hopefully that gives you know, a little bit of color. To your second question, you know, I'm teasing you a little bit, Andres, that's exactly what we're doing. You know, the examples that you were giving, you know, we're now, you know, the data is still pretty fresh. We had a preliminary look at things, all the things you talked about and more what we're gonna dig into, you know, in the coming period.
Thanks very much.
Thanks for the question, Andres. Our next question comes from Silvan Tuerkcan at JMP. Please go ahead, Sylvain.
Hey, good morning, thanks for taking my questions. Maybe just kind of along the similar line of questioning here, maybe around the statistics of the data that you presented today. Those Kaplan-Meier estimates, obviously there's a big focus on 12 months here, they I guess they're blended from we got those pre-protocol patients that kind of weigh on the tail, maybe pull it down. Then the important post-protocol patients are kind of split in this group that respond and didn't respond, a lot of them in the 6 months.
At the six-month rate, like what, did you do any back on the envelope calculations on what are the odds that the difference in the six months rate between the cut in the post protocol that we've seen before and that we are seeing later or after the cut-off is significantly lower, one, that that's noise versus some systemic issue that went on at the sites. Thank you.
Thanks, Silvan. No, we have not done that. That's part of the work that's ongoing. Like I said, the data just recently cut, right? Now, you know, our teams are really digging into all those questions that you know, that you just, you know, that you just articulated.
The bladder, the rinse, these 80 new patients, would any of those be available for the next data cut or is that still very early?
Yeah, it's hard for us to say. I'm actually really proud of the team. You know, we have 20 set of sites up and going and sites are coming on board. There's a lot of interest, you know, within the community. We have to see how, you know, screen and enrollment goes before we have a sense of, you know, what data we'll have at one time. We're looking forward to providing an update on that.
Great. Okay. Thank you.
Thanks, Silvan.
Yes, thanks, Silvan, for the questions. This concludes today's Q&A session. I'll now turn it back over to you, Ron, for closing remarks.
Great. You know, thank you very much, operator. As I said earlier, the emerging profile of detalimogene is starting to become clearer. Let's take it from the perspective of a busy community urologist. The first challenge facing the urologist is to convince usually an older man in their 70s on other medications with comorbidities that after BCG failure, to use another medicine. Detalimogene's tolerability profile and lower number of administrations are attractive. Next, the urologist will want to know quickly if the product is working and if it doesn't work, do they have other options? With the rapid onset of efficacy, over 90% of the responders getting an effect within the first 90 days and a very low rate of progression to muscle invasive or more advanced diseases are attractive characteristics of detalimogene.
The next challenge is to convince the practice administrator to be able to use a higher cost medication. With regular refrigeration and freezer storage, no need for special equipment or personnel, and the possibility of implementing buy-and-bill.