Thank you for standing by. Welcome to today's conference call. At this time, all participants are in a listen-only mode. After the speaker's presentation, there will be a question- and- answer session. To ask a question during the session, you'll need to press star one one on your telephone. You will then hear an automated message advising your hand is raised. To withdraw your question, please press star one one again. Please be advised that today's conference is being recorded. I would now like to hand the conference over to Michael Kaiser, VP Investor Relations. Please go ahead.
Thank you for joining HOOKIPA's HB-200 data update call. Today's call will contain forward-looking statements. These statements are subject to risks and uncertainties that may cause actual results to differ materially. For a description of these risks and uncertainties, please refer to HOOKIPA's annual report on Form 10-K and quarterly reports on Form 10-Q, as updated periodically, along with other SEC filings. Contents of this call are based on current beliefs of HOOKIPA's management team as of June 4, 2024. The company disclaims any obligation to update statements to reflect events or uncertainties or circumstances after the date of this call. This call is being recorded, and a replay, along with the presentation slides, will be available on the investor relations section of the company's website later today. I will now turn the call over to Jörn Aldag, Chief Executive Officer at HOOKIPA Pharma.
Hello, everyone. Thank you for joining us today. We want to share with you our exciting updated data for our phase II trial of HB-200 in combination with pembrolizumab for the treatment of HPV-16 positive head and neck cancer. The data was presented earlier today at the ASCO annual meeting. More patients, encouraging signs of durability. I will begin with an overview of our pipeline and key advantages for HOOKIPA. Then our Chief Development Officer, Mark Winderlich, will take you through our data for HB-200 first line, as well as our neoadjuvant investigator-led trial, followed by a brief Q&A session. Before we get into the data, I would like to highlight the depth of our arenavirus platform and its capabilities to address multiple indications across different disease areas.
As you will hear, HB-200, our core program for HPV positive head and neck cancer, continues to deliver clinically important and meaningful results for our patients. We are proceeding at full speed to begin enrolling patients in our seamless pivotal phase II/III trial in the fourth quarter of this year. The patient population was chosen and the trial designed to give us a high probability of success and get to market in the shortest possible period of time. Our second oncology program is HB-700 for KRAS mutated lung, colorectal, and pancreatic cancers. This program engineers the arenavirus with the five most prevalent KRAS mutations of these indications into a single therapeutic and has the potential to benefit a broader patient population than single mutation inhibitors. The program just cleared IND with the FDA in April, and we're finalizing the clinical development plans for development within HOOKIPA or in partnership.
Of course, we have two infectious disease programs partnered with Gilead, the world leader in infectious disease. These programs in hepatitis B and HIV are designed to be part of a curative treatment cocktail. We greatly value this partnership and are pleased with how far each program has actually progressed to date. HB-400 is a hepatitis B program, it's fully in Gilead's development, and it's progressing well through clinical phase IB. The next step is Gilead's decision to progress to phase II development. HB-500 is our HIV program, which cleared IND last fall, and we're on track to enroll our first patient imminently, by the end of this month, actually. HOOKIPA is responsible for taking the program through phase IB, at which point Gilead has an exclusive option to proceed to a phase II study.
We have a lot to be excited about at HOOKIPA at this point, and we're well positioned to execute. We are building on our advantage. Our strong data and clinical development plan give us a clear path to registration for our lead program, HB-200. We are addressing a significant unmet need, as Mark will show you, for treatment that is targeted to fight HPV-16 positive head and neck cancers. We and our investigators believe that the unique biology of this disease requires a targeted treatment. By combining two immunotherapies, HB-200 and pembrolizumab, we think that we can deliver a meaningful improvement to survival benefit for patients with HPV-positive disease. Our phase II data for HB-200 in combination with pembrolizumab are convincing and are best in class among HPV-16 targeted therapeutics.
Mark will share the details of our updated data, but as you will see, HB-200 continues to deliver remarkable results for patients in terms of response rates and also durability. And crucially, we have to find a fast path to registration that likely puts us in the position to be first to market in HPV positive head and neck cancer. We have full alignment with our regulators in the U.S. and Europe, and our development team is rapidly progressing our program to the registrational trial. At this time, I will turn over to Mark to take you through the ASCO data of HB-200. Mark?
Thank you, Jörn . As you mentioned, HPV infection has been linked to the increased incidence of head and neck cancer in the U.S., with 70% of oropharynx cancer cases being HPV related, and HPV-16 being the predominant type responsible for 90% of all HPV positive cancers. Clearly, development of pembrolizumab as standard first-line therapy for recurrent metastatic head and neck cancers has been an important paradigm shift for the management of this disease. But pembrolizumab monotherapy still only benefits a small proportion of patients, with objective response rates ranging from 15%-24% across various subgroups. Even in the CPS 20 and above population, pembrolizumab has shown modest PFS with a median of 3.4 months and a 12 months overall survival rate of only 56%.
Adding chemotherapy or EGF receptor targeting cetuximab increased response rates, but without meaningful improvements in progression-free survival or overall survival for the price of increased toxicity. Currently, there are no approved therapies targeting HPV positive disease specifically. The distinct biology profile of HPV positive head and neck cancer, driven by the expression of viral oncoproteins E6 and E7, provides the unique opportunity to augment immunotherapy efficacy with strategies tailored to the HPV biology, and thereby increasing sustainable immunogenic tumor cell death. HB-200 therapy consists of two replicating arenavirus vectors that express the same non-oncogenic HPV viral fusion protein. Alternating IV administration minimizes immune response to the arenaviral backbones, but efficiently induce antigen-specific cytotoxic T cells homing to the HPV-expressing tumors for efficient tumor cell killing.
In the phase I part of our ongoing study, we have previously shown that HB-200 alone induced robust tumor-specific cytotoxic T cells, resulting in tumor shrinkage and response in patients with checkpoint inhibitor pretreated head and neck cancer. Today's data update is for the phase II portion of our ongoing trial with HB-200 plus pembrolizumab in the first line treatment of recurrent or metastatic disease. As of March 29, we have treated 46 patients and a median follow-up time of 7.4 months. Nearly half of the patients are still on treatment, and only five death cases overall have been observed, none of them treatment-related. Disease and patient characteristics of these populations are comparable to those in historical trials of pembrolizumab monotherapy in the metastatic recurrent setting. The combination of HB-200 with pembrolizumab was well tolerated.
The majority of treatment-related adverse events were mild to moderate and in line with the HB-200 or pembro monotherapy data. There was no increase of immune-related adverse events and has not been observed in addition to what is known for pembrolizumab monotherapy. Treatment-related adverse events leading to discontinuation of HB-200 occurred only in two patients, and as said before, no death occurred due to a related adverse event. The most common treatment-related adverse events were mostly low-grade flu-like symptoms, in the majority of the cases, limited to the first treatment cycle, demonstrating that HB-200 induced a strong immune system activation. We continue to see that HB-200 induces high levels of tumor-specific T cells rapidly and sustainably, with increasing polyfunctionality over time, as shown by intracellular cytokine staining, as seen in this little pie chart below the x-axis.
Robust and sustained induction of polyfunctional HPV-16 tumor-specific T cells is the basis of the enhanced antitumor activity that we observe. 38 patients in the efficacy population had a minimum of 4.5 months on study, with at least one post-baseline scan or discontinued treatment earlier for any cause. The objective response rate was 37%, with a complete response rate of 11.4% and a disease control rate of nearly 70%, including long-term stable disease cases. The waterfall plot shows that 57% of all patients had tumor shrinkage. There was a marked higher rate of response and degree of tumor shrinkage observed in the CPS 20 and greater cohort, represented here by the blue bars. This subgroup of patients is representative of the eligible population for our pivotal trial starting soon.
Now we will take a closer look at the CPS 20 and greater population. In this group, efficacy was more pronounced, with an ORR of 53% and an encouraging CR rate of 18%, as compared to pembro monotherapy of approximately 24% ORR and only 8% CR rate in historical trials. The disease control rate was 82%, including long-term stable disease cases. The more pronounced synergy of the combination in the CPS 20 and above subgroup, is supported by a scientific and biological rationale. In this subgroup, the primary tumor cell defense mechanism against increased infiltration of immune cells, has been shown to be PD-L1 expression. HB-200 provides the high number of polyfunctional tumor-specific T-cells, while pembrolizumab ensures that these T-cells stay active in the tumor and do their job.
In the spider plot on the right side, you see that the majority of patients experienced tumor shrinkage with a deepening and durable response over time. As of data cutoff, 67% of the response in the CPS 20 or greater population were still ongoing, and 62% of the total population in CPS 1 or greater. The median duration of response is still maturing, and the longest time on treatment for responders is approaching now the 2-year mark. The improved overall response rate, CR rate, and disease control rate, result into very promising preliminary progression-free survival and overall survival at a median follow-up time of 8.4 months. There have been 9 PFS events in 19 patients observed, and the median PFS is 16 months. Sixteen out of 19 patients are still alive at data cutoff, and the overall survival rate at 9 months is nearly 90%.
We are very encouraged by the PFS and OS data when contextualizing with historical pembrolizumab monotherapy in the CPS 20 and above subgroup. Median PFS has been at 3.4 months, and the 12 months OS rate only of 56% has been observed. A synergistically acting immunotherapy combination forms the basis for a potentially improved survival benefit via increased and sustainable immunogenic tumor cell death. As you may recall from our last call, our pivotal phase II/III trial design and protocol are aligned with the FDA, and this alignment includes the path for potential accelerated approval. We have designed a seamless and adaptive double-blinded, randomized phase II/III trial. Key eligibility criteria are driven by the data that I have just shared with you, and gives us the highest probability of trial success, including the potential for an accelerated approval based on ORR.
In total, 250 patients will be randomized 1:1 to either HB-200 plus pembrolizumab or placebo plus pembrolizumab. Overall response rate is the primary endpoint for the phase II part, with approximately 50% of the study participants, and the intent of submission for a potential accelerated approval. The anticipated analysis time point is 2026. The primary endpoint of the phase III part of the trial is overall survival, and the anticipated analysis time point is 2028 for a potential full approval. We are just now actively qualifying clinical trial sites, and we are on track to enroll our first patient in the fourth quarter of this year. Before I turn over the call to Jörn for summary, it is important to quickly highlight the additional applications of HB-200 in the non-metastatic head and neck cancer setting.
We currently have two investigator-initiated trials, one in the neoadjuvant setting in combination with chemotherapy, and the other one in the adjuvant setting. In the neoadjuvant setting, Dr. Rosenberg from the University of Chicago, presented yesterday at ASCO. The initial findings show HB-200 plus chemotherapy is safe and feasible with HPV-16 specific T-cell responses, and marked reduction in ctHPV DNA was observed. Early efficacy signal with deep response rates of 81% across all dose levels in 21 patients was observed, versus 70% historical control rate for neoadjuvant chemotherapy alone. Higher dose levels of HB-200 were associated with even higher deep response rates. The trial continues to enroll while we define development path in parallel. In addition, Dr. Wong at MSKCC recently launched an IIT in the adjuvant setting, and we anticipate that the first patient enrolled is imminent.
In this trial, patients with detectable HPV-16-related tumor DNA in the blood after treatment for curative intent, are treated with HB-200 monotherapy, with the goal to delay reoccurrence or eradicate the cancer in the patient. As Jörn mentioned earlier, there are many applications of our arenavirus platform, including very closely related applications for HB-200 in the fight against HPV-driven cancers, and we are only just at the beginning. Jörn, back to you.
Hi. Thanks, Mark. Exciting data. We view HB-200 as the first and key step for HOOKIPA in our patient-centric clinical development strategy. A step by which we intend to optimize the probability of success, cost, and time to market. There's an increasing incidence of HPV-driven cancer diagnosis each year. We aim to be the first targeted therapeutic for HPV-driven head and neck cancers. And so we will drive a focused oncology strategy, starting with oropharyngeal head and neck cancers. It represents a sequential opportunity for future expansion. As you see on the bottom of this slide, the potential addressable market of our upcoming registrational trial is meaningful. We believe this market alone presents an opportunity of more than $500 million worldwide for the CPS 20 population that we're running our trial for.
This addressable market grows rapidly and provides additional growth potential beyond the first line setting for oropharyngeal cancers. There is a natural path to expand within the HPV-positive head and neck space, including patients with PD-L1 CPS 1-19, where we saw signals for other head and neck first line treatments and locally advanced disease for both adjuvant and neoadjuvant settings. Mark has shown you an example of what we're doing with academia in this regard already today. From there, HB-200 can become a tailored treatment option for other HPV-positive cancers in multiple organs beyond head and neck. It is estimated that each year there are approximately 100,000 new cases globally that could benefit from an HPV-targeted treatment, such as HB-200. HPV-positive cancer therapeutics have, in our mind, blockbuster potential.
Ultimately, we believe that our arenavirus platform can be applied in different disease areas and for a broad array of antigens. This includes programs such as our KRAS-mutated tumor program I mentioned earlier. We have large aspirations in oncology. In summary, we have seen very encouraging results with the use of HB-200 in combination with pembrolizumab in the first-line recurrent metastatic head and neck cancer setting, with rapid and durable induction of tumor-specific and polyfunctional circulating T cells. We have observed a favorable efficacy and tolerability combination profile, particularly the CPS 20 and above cohort, has shown a compelling objective response rate of 53% and complete response rate of 18%, with encouraging preliminary progression-free and overall survival.
Based on these exciting results, we have alignment with the FDA for a randomized phase II/III pivotal study with the potential to file for accelerated approval based on objective response rates. We have also received PRIME designation from EMA. The collective work of our team has brought us to this point, and we are in position to begin the registrational trial in the fourth quarter of 2024. There is immense opportunity ahead for HOOKIPA, and I'm confident that we have the team set up to execute on our goals, to bring a cancer drug to help patients overcome this horrible disease. With that, I will turn the call over to the operator for Q&A. Thank you.
As a reminder, to ask a question, please press star one one on your telephone and wait for your name to be announced. To withdraw your question, please press star one one again. Please stand by while we compile the Q&A roster. Our first question comes from the line of Brian Abrahams with RBC Capital Markets.
Hi, thanks. It's Brian Abrahams from RBC. First off, congrats on the data. Question, in the abstract, there were several, I think three, unconfirmed responses. I know the data looked pretty consistent or very consistent on the confirmed response front. It looked like one unconfirmed had converted to a confirmed response. I was wondering if you could just comment on the other two, whether we're still waiting to learn more about them, or should we assume they remain unconfirmed? Thanks.
This is Mark speaking. This is Mark speaking. One of them, which we had in the abstract, were five after the data cut off, not confirmed. For the other ones, we are waiting for the scans. Also for those patients, of the 46, which were excluded for the efficacy evaluable population, are on treatment. All of them are on treatment and, we see a new PRs coming, new responses are coming in.
Great. I'll hop back in the queue. Thanks.
Our next question comes from the line of Andrew Berens with Leerink.
Hi, congrats on the results and all the progress. Very impressive durability. Wondering if you have given any thought to testing the drug in combination with an EGFR agent or bispecific in HPV-positive patients with lower levels of PD-1. Now that we know Merus is planning to run their trial, including HPV-positive patients. It was a small sample size, but they do seem to have some activity in the HPV-positive patients. And then can you also tell us what percentage of patients had PD-L1 levels above 50, and if they had better responses to HB-200 than Keytruda? And then lastly, when you were discussing with the FDA on the trial design, was there any discussion about whether you should allow investigators to choose the control arm?
Mark.
Yeah, I will, I will start saying CPS 1-19. So you may have seen that our CPS 1-19 population is actually a 1-11 population so far, with a median CPS score of 2. And still, we see increased response rates and disease control rate compared to what pembrolizumab monotherapy has shown historically. So, first, we, we aim to continue enrolling patients in our ongoing phase II trial to get patients in with a CPS score from 10-19. We also want to have a longer follow-up, because specifically in this population, we see that stable diseases over long- term convert to a response at the fourth, fifth, sixth, or even seventh scan.
So we think that the benefit is developing over time, and we collect further data, and we'll then define the strategy for a registrational path in this patient population, as well. For we think EGF receptor targets or targeting agents, even second generation in HPV positive, is still to be seen. The biology of the disease of the cancer cells is very different in HPV positive. It is not driven by EGF receptor amplification, but by the viral oncogene. To your second question, this was a CPS 20 and above. So the median is at approximately 40 for the CPS 20 and above patient population, and we did not see within the group a correlation of response with higher CPS scores. So the relationship of the synergies seems not to be, so far as we see from the data, not to be linear, but then have an S-shaped form where you get into a plateau from a certain CPS score onwards. And for your third question regarding the FDA and the control arm, I could not 100% understand your question acoustically. Could you repeat it?
The doctors choose the control arm, what regimen they wanted to use, if they wanted to use chemo plus checkpoint, maybe.
Okay, thank you. No, we discussed it with the FDA, and for this, a very homogeneous patient population, oropharyngeal squamous cell carcinoma with a CPS 20 or above, pembrolizumab monotherapy is the clear standard of care. So it was clear that the control arm would be pembrolizumab monotherapy and not pembrolizumab plus chemotherapy.
Our next question comes from the line of Roy Buchanan with Citizens JMP.
Hey, thanks for taking the question. Impressive durability, especially the complete responders. Just one quick one. Just the overall survival curve. How many of the 16 patients are still alive today?
Mark speaking. All of them. So in the whole patient population, 38 patients or even 46, we have only observed five death cases. So all of them are in survival follow-up, and we have only two censorings because of withdrawn consent. Importantly, we looked also at the subsequent therapies for patients who are not on treatment anymore, and they received the standard of care in second line, so basically chemotherapy or chemotherapy again combined with pembrolizumab. So this is why we are very encouraged by this preliminary overall survival data.
Thank you.
Our next question comes to the line of Arthur He with H.C. Wainwright.
Hey, Jörn and team. Congrats on the data. Really impressive on the durability-wise. I had a quick one on the patient for the PD, regarding PD per iRECIST 1.1. Is that patient still remain on the study?
So this was an interesting case where we had, in the majority of the target lesions, a reduction in tumor size, but one lesion increase in tumor size. So this speaks for tumor intrapatient tumor heterogeneity, and the treatment was then stopped.
T hanks.
Our next question comes from the line of Asthika Goonewardene with Truist.
Hey, guys. Thanks for taking my question, and I'll offer my congrats as well, to the impressive, PFS and durability that you're seeing here. I was wondering if you could break out, in your baseline characteristics, what proportion of patients had more bulky tumor? And just if you look- reflecting on the swim, on the spider plot here, it looks like, you know, your, you had some responses, a little bit early on, but it seemed to be, kind of, you got some subsequently and a little bit further down the line as well. So with that in line, in mind, can you talk to us a little bit about, the rate at which-... you'll get patients accrued onto your pivotal trial. Just wondering if there might be some sort of natural selection to get patients who have less bulky disease, onto the study. Thank you.
Thank you. Yeah, for the baseline characteristics, of course, we did subgroup analyses among, I mean, looking for tumor size, metastatic versus locally recurrent, only or other patient or disease characteristics. And we did not see any pronounced difference in terms of ORR or CR rates across the different subgroups, so nothing we could say there. And the tumor size in terms of sum of diameter of the target lesions were as in other trials in historical trials of pembrolizumab monotherapy in this recurrent metastatic setting. And the second question you asked were about the responses and how we anticipate to enroll.
The feasibility of the phase II/III is ongoing, and we also, of course, know from our ongoing phase II trial in which regions we need to go and which sites we are engaging. So we will roll over sites from our ongoing phase II into the pivotal trial, so to start in the U.S. end of this year. And with the feasibility results we have so far, we are very optimistic that we will be able to enroll to have the primary analysis for the phase II in 2026 for overall response rate. But as you know, the incidence of HPV positive head and neck cancer is not evenly distributed across the regions of the world. This is why we do a thorough feasibility of sites, countries, and regions, and select sites accordingly to have the best probability of enrolling as we plan.
Great. Thanks for taking my question.
That concludes today's question- and- answer session. I'd like to turn the call back to Jörn Aldag for closing remarks.
Yeah, thanks for taking the time. We're making great progress in HPV-positive head and neck cancer, and we're delighted that you're interested in the progress that is being made in the field. Thank you very much for being part of this call, and all the best to our next discussion. Bye-bye.
This concludes today's conference call. Thank you for participating. You may now disconnect.