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Operator
Good day and thank you for standing by. Welcome to the Bycara Therapeutics fourth quarter and full year 2025 earnings call. (Operator Instructions) I would like to hand the conference over to your speaker today, Rachel Frank. Please go ahead.
Rachel Frank - Investor Relations
Thank you, and good morning, everyone. It's a pleasure to welcome you to Vicara Therapeutics' fourth quarter and full-year 2025 earnings call. Earlier this morning, we issued a press release highlighting results from the quarter and recent business progress. You can access the press release as well as the slides that we'll be reviewing today by going to the Investors section of our company website.
Before we begin, please note that this call will include forward-looking statements under the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Please refer to our most recent SEC filings for important risk factors that could cause our actual performance and results to materially differ from those expressed or implied in these forward-looking statements. Any forward-looking statement made on this call represents our views only as of today, and we disclaim any obligation to update any forward-looking statements.
Joining us on the call today are Claire Mazumdar, Chief Executive Officer; Ryan Cohlhepp, President and Chief Operating Officer; and Ivan Hyep, Chief Financial Officer. I'll now turn the call over to Claire.
Claire Mazumdar - Chief Executive Officer
Good morning, and welcome to Bycara Therapeutics' inaugural quarterly earnings call. I'm Claire Mazumdar, Chief Executive Officer.
Today marks an important milestone for our company as we begin this tradition of regular communication with investors, analysts, and stakeholders to provide transparent updates on our business progress and strategic direction via the quarterly earnings call process.
We're implementing these quarterly calls as part of our commitment to maintain an open dialogue with the Street and ensuring you have consistent visibility into our execution against key milestones and strategic objectives.
Before I jump into our Q4 2025 highlights and recent progress, let me provide a brief background for those who are newer to our story.
Bicara Therapeutics is a clinical-stage biotech company pioneering bifunctional antibodies for targeted tumor modulation.
Founded in 2020, we built a global team of over 100 employees headquartered in Boston with a clear focus on advancing our lead asset, Fisera-Fys-Alpha, or Fisera, a potentially. First-in-class bifunctional EGFR-directed antibody combined with the TGF-beta ligand trap.
Our innovative approach combines tumor targeting with tumor modulation, where one arm localizes to the tumor while the other serves as a modulator, designed to deliver superior efficacy, improve safety, and enhance durability directly at the tumor site.
Visera specifically addresses a key challenge in solid tumor treatment by enabling immune cell penetration into tumors, reducing fibrosis and immunosuppression while reversing TGF-beta-driven resistance mechanisms, ultimately designed to drive the deep, durable responses that may translate into better outcomes and survival for patients.
Over the past several months, there have been significant shifts in how the competitive landscape and frontline recurrent and metastatic head and neck cancer is evolving. Our recent clinical data and regulatory progress clearly positioned Phycerra as the potential best and first-in-class asset with a differentiated clinical profile on both long-term outcomes and tolerability.
Looking back at the progress we've made since October 2025, I'm energized by the exceptional momentum we've built across our pipeline and operations.
Over the past several months, we've achieved multiple critical inflection points that fundamentally strengthen our position as we advance Phicerra toward a pivotal study interim analysis in the middle of next year.
First, Bisera received Breakthrough Therapy Designation (BTD) in combination with pembrolizumab for the first-line treatment of patients with metastatic or with unresectable HPV-negative recurrent head and neck squamous cell carcinoma.
This designation from the FDA underscores the growing recognition of HPV-negative head and neck cancer as a distinct clinical indication within head and neck cancer, one with particularly poor outcomes, limited therapeutic options, and that represents the vast majority of patients.
Second, we presented two additional Phase 1B clinical data sets across clinically active doses of Physera that demonstrated consistent overall response rates, further validating Physera's unique dual mechanism targeting both eGFR and TGF data, and de-risking the OR endpoint in our pivotal study interim analysis.
Third, building on this robust data set, we selected 1,500 milligrams as our optimal biological dose and have successfully moved into the Phase III portion of our pivotal Fortify HNO1 study, for which we expect an interim analysis in the middle of next year.
This represents a major strategic advancement that brings us significantly closer to our goal of delivering a potential best and first-in-class treatment option for patients living with HPV-negative head and neck cancer.
Fourth, we recently announced plans to develop Vysera with the loading and every three-week maintenance dose, a strategic commercial decision based upon updated clinical, translational, and pharmacokinetic data that we believe will enable additional optionality for patients and providers choosing treatments with Vysera.
Lastly, to support this accelerated trajectory and pull forward investment in our early commercial and medical build, we successfully completed an oversubscribed public offering, strengthening our balance sheet and providing the capital foundation necessary to execute this next chapter of our business with confidence.
With that, I'll turn it to Ryan to provide a bit more detail on our recent clinical updates and business progress.
Ryan Cohlhepp - President, Chief Operating Officer, Director
Thank you, Claire, and good morning, everyone.
We've now reported clinical experience in approximately 90 patients across three Phase 1B cohorts, evaluating Pisera in combination with pimbrolizumab and frontline recurrent metastatic HPV-negative head and neck squamous cell carcinoma.
Our 1,500-milligram every-week data is the most mature with two years of follow-up and demonstrates deep, durable responses that lead to median duration of response and median overall survival of 21.7 and 21.3 months, respectively, nearly tripling the median overall survival observed with the standard of care of pembrolizumab and HPV-negative patients.
Like last year and just last month, we presented two additional cohorts. In December of 2025 at ESMO Asia, we presented data from our 750 milligram every week cohort, which helped to ultimately inform 1,500 milligrams every week as the optimal biologic dose for our ongoing pivotal Phase III Fortify HNO1 trial.
And just last month at the multidisciplinary Head and Neck Cancer Symposium, we presented data from a higher but less frequent dose.
Fisera in combination with pembrolizumab, 2000 milligrams every two weeks, from which we announced our plan to develop a less frequent loading and maintenance dosing option. Our aim is to gain alignment with the FDA on this approach and initiate that study in parallel to the pivotal study to allow to have data from that regimen in hand upon potential U.S. Approval.
Clinically, tumor shrinkage is seen at all doses that trends deeper with higher exposure. The 1,500-milligram cohort showed deeper median depth of response versus 750 milligrams, and the exploratory 2,000-milligram, every two-week cohort produced consistently high proportions of deep responders with greater than 80% shrinkage and complete response rates.
Our translational data shows consistent TGF-beta inhibition across all Pysera doses, confirming the mechanism that drives tumor penetration and immune activation. Importantly, inhibition is strongest with a 1,500-milligram weekly dose and less frequent 2,000-milligram regimen.
We believe this TGF-beta-driven depth of response is the defining hallmark of Pysera and a clear differentiator versus EGFR-directed therapies, which do not target TGF-beta.
This mechanism is especially meaningful in HPV-negative disease, a setting with poor outcomes and limited innovation where deeper, more durable responses are urgently needed for patients. We remain confident that this biology will continue to translate into clinically differentiated, long-term outcomes for these patients.
Importantly, PYCERA's deep responses are paired with sustained durability without any trade-off.
The median duration of response approaches 22 months, more than three times longer than the 6.7 months median duration of response reported with pembrolizumab plus chemotherapy.
Our 2000 milligram every two-week cohort similarly delivered multiple deep responses persisting beyond 20 months, underscoring the consistency of benefit across dosing schedules.
Crucially for patients, providers, and payers, Pisera maintains this level of durability, even with less frequent dosing.
This positions Pisera favorably in a market moving toward treatment regimens that reduce clinic burden, improve quality of life, and support long-term adherence. We believe...
This performance reflects Fisera's tumor-penetrating mechanism, enabling depth and durability that translate into meaningful long-term outcomes while supporting a more flexible, patient-centric dosing paradigm.
We're often asked whether deep depth of response translates to long-term outcomes.
As we first showed at ASCO last year, there's a clear distinction in duration of response, progression-free survival, and overall survival among HPV-negative head and neck cancer patients who have had deep responses versus those that do not.
This data is what drives our belief that deep responses that are the hallmark of PYCERA's clinical profile drive outsized durability and long-term benefit.
Importantly, other investigational agents also need to demonstrate the deep and durable responses to meaningfully improve long-term clinical outcomes.
As our recent financing highlights, we have strong conviction in Ficerra's clinical data and its differentiated profile compared to other investigational agents in the head and neck space.
And we are continuing to bolster our commercial and medical investment in preparation for a potential U.S. Launch, including hiring of the Chief Commercial Officer this year.
Red and nut cancer is a significant and fast-growing global market, projected to reach more than $5 billion in global sales in the 2030s. HPV-negative patients represent the heavy majority of patients in a frontline recurrent metastatic setting, and HPV status is known by the time the disease recurs or metastasizes, which means that HPV testing will not be a barrier to care.
There are roughly 50,000 annually incident patients across major markets, including approximately 18,000 in the U.S., where we planned our initial launch.
With Pisera, we have the potential to significantly expand an already significant HPV-negative head and neck cancer market. Pisera's clinical data show us that we further expand that market in two ways. First, by growing the number of patients who are responding to therapy, as seen with the PACCA, Pisera provides a two to three times greater overall response rate. And second, by growing the duration of response as seen by Pisera's two to three-fold improvement over standard of care median duration of response.
We are pioneering. A new treatment paradigm for HPV-negative head and neck cancer with a tailored therapy engineered to overcome the unique biology of this disease and achieve deep, durable, and clinically significant benefit while sparing the use of chemotherapy to further improve quality of life for patients.
With this knowledge in hand, we are eager to further invest in our pre-launch activities across commercial and medical.
Including additional evidence generation strategies that may further expand the market opportunity beyond that being studied in our pivotal trial.
Recent competitive updates have only strengthened our conviction. The Fisera may have the best chemosparing regimen that actually addresses both the EGFR and TGF-beta inhibition underlying biology of HPV-negative head and neck cancer to improve long-term outcomes for patients.
We are preparing to launch in an environment where, based upon evolving regulatory and clinical development commentary across our competitors' set, we have the opportunity to set the tone for what the therapeutic bar looks like for significantly improving unmet medical need in this space.
As we head into the second quarter, we look forward to providing long-term follow-up data from across our Phase Ib studies of Pycera in combination with pembrolizumab and frontline recurrent metastatic HPV-negative head and neck cancer. The Phase Ib 1,500 milligram every week data presented at ASCO 2025 were mature with a median duration of response of 21.7 months and a median overall survival of 21.3 months. In this update, we are looking for a better understanding of that IO tail at. Extended duration of follow-up, as well as the additional maturity on key endpoints from the 750 milligram every week and a 2000 milligram every two-week datasets.
No other investigational agent targeting EGFR in the head and neck cancer space have shown durability of outcomes out this far, a key differentiating factor for Precera that resonates deeply with clinicians.
With that, I'll turn it to Ivan to review the financials.
Ivan Hyep - Chief Financial Officer
Thanks, Ryan. Earlier this morning, we reported detailed fourth quarter and full-year 2025 financial results in our press release, and I'll summarize a few highlights here. Our total operating expenses for 2025 increased compared to the fourth quarter and full-year 2024, driven by clinical operations and development expenses, including increased manufacturing and process development costs associated with our ongoing pivotal Fortify HN01 study.
We also saw an increase in personnel-related costs, including. Stock-based compensation as we grew our workforce throughout the year, primarily in support of clinical operations and development functions.
We anticipate an increase in operating expenses for 2026, driven by increased investment in clinical operations, particularly for the pivotal Fortify HN01 study, the interim analysis for which is expected in mid-'27, as well as an increase in SG&A and head-on expenditures as we invest in early commercial and medical infrastructure to support the potential. Launch of Fisera.
We entered 2026 with $414.8 million in cash equivalents, and marketable securities. In the first quarter, we raised an additional $161.8 million in net proceeds via an oversubscribed public offering, which further strengthens our balance sheet, and we maintain cash runway guidance into the first half of 2029.
This additional capital will allow us to support a planned regulatory filing for Fisera.
Further invest and build in our medical and commercial infrastructure ahead of a potential U.S. Approval and launch.
Further accelerate the development of Physera in head and neck cancer, including a less frequent dosing schedule.
Fund manufacturing costs for Physera for ongoing and anticipated drug development efforts.
Fund early signal-finding activities to support further indication expansion for Physera and fund other general corporate purposes.
Our existing cash as of year-end and this additional recent cash infusion puts us in a position to be able to drive smart growth for Fisera as we enter a period of discipline but increased investment to drive future clinical and commercial success.
With that, I'll now turn the call back over to the operator for questions.
Operator.
Operator
Thank you,(Operator Instructions)
Tyler Van Buren with TD Cowen.
Tyler Van Buren - Analyst
Hey, guys. Good morning. Thanks for taking the questions. Can you provide more color on the patient demand and willingness to participate in pivotal 4-5 study that you're seeing in both the US and in ex-US sites? And as a follow-up or kind of related.
Ryan Cohlhepp - President, Chief Operating Officer, Director
Question, do you have a sense of how many patients you might need to enroll in a separate study of the less frequent dosing regimen to achieve registration?
Rachel Frank - Investor Relations
Thank you for your question, Tyler. So, there are two questions. One was around momentum around patient enrollment in the Fortify HN01 study. And then the other was, approximately how many patients do we plan to enroll in the parallel bridging study for the loading and maintenance dose? I'll answer the second first and speak to the fact that we're looking for regulatory alignment, and we'll provide far more clarity to the study in more detail. Once we have that regulatory alignment. But the approximate size is anywhere between 150 to 200 patients, is our current estimate.
The first question was around enrollment of the 4 to 5 study. What I can say is that we continue to build significant momentum in that study, as we have both received a breakthrough designation, as well as moving from the Phase II to the Phase III portion, and going now to the 2 to 1 randomization of 1,500 milligrams weekly, randomized. 1 to pembro monotherapy. We've seen great momentum also ex-U.S., in particular in European sites, Asian Pacific sites, as well as South America, with a significant momentum in areas where we know that there's a high prevalence of smoking. I will pass it over to Tanya to give additional details to the Fortify agenda 1 momentum.
Hi, thanks. This is Tanya Green, Chief Development Officer. So, yeah, as Claire said, we have really strong momentum for the Phase III study in terms of enrollment. As is publicly available, we have 129 active sites right now. And this team remains highly focused in executing the study to achieve substantial enrollment by the end of this year, which will keep us on track to have our interim analysis by mid-2027.
Operator
Thank you. Eric Schmidt with Cantor Fitzgerald.
Eric Schmidt - Analyst
Well, good morning, and thanks for all the question and congrats on all the recent progress. Questions on the colorectal cancer update that we might see in the second-half of the year. Could you just give us a sense for the stuff with that update in terms of patients, dosing.
And in particular, what type of benchmarks you think you'd hope to be able to provide in order to demonstrate proof of concept?
Thank you.
Ryan Cohlhepp - President, Chief Operating Officer, Director
Hi, Eric.
Thank you for the question. In terms of our CRC update, as we've indicated, we looked to have data in the second-half of this year on those cohorts. In terms of the total number of patients that we planned to present, I think that's still somewhat variable based upon enrollment.
But consistent with our previous updates, we're always looking for data sets, probably no less than 20 patients per cohort.
I think that certainly, even as recent, we've seen the treatment landscape evolve and we're mindful of that with recent data that's been out.
I'd say what we're the two cohorts that we are currently exploring seeking signals in are third line.
As that's a highly.
Challenging population. And again, we've got both a cohort in monotherapy as well as one in combination with pembrolizumab at the 1,500 milligram weekly dose. So again, I think we continue to look at that data for signal-seeking purposes and determine whether there's a path forward in CRC, particularly as we look to see about the opportunity to move into earlier lines of therapy in colorectal cancer, using those signals to determine whether there's something there to invest further.
Rachel Frank - Investor Relations
Thank you.
Operator
Stephen Wiley with Stifel. Your line is open.
Stephen Willey - Equity Analyst
Yeah, good morning. Thanks for taking the questions.
I guess with the understanding that you're going to be providing the kind of pooled expansion cohort data in a few months.
Just curious if the patients in the 750-meg once-weekly cohort were given the opportunity to uptitrate to the 1,500-meg dose, given the, I guess, the relative deficiency in depth of response?
Rachel Frank - Investor Relations
Great questions, Steve. So, what we'll be presenting at ASCO is likely an update from three separate cohorts, the three-year follow-up, median follow-up for the 1,500-milligram dose weekly, the 750-milligram weekly dose, it was about a 30-patient cohort with at least 18 months of follow-up, and same for the 2,000-milligram every two-week cohort, an additional 30 patients with about an 18 months of follow-up. So, in that particular cohort, to your question, the 750. We did not increase the dose afterwards. These were patients that were maintained at the 750-milligram dose throughout their course of treatment, and we will be providing an update to PFS and duration of response from those cohorts that will continue to speak to the depth and durability profile that we see across our cohorts.
If you're a question regarding the pivotal study in Fortify Agenda 1, I do believe that we were able to cross over the patients enrolled at this lower dose. And so, if they remained on treatment, they did cross over to the 1,500-milligram dose in the pivotal study.
Thank you for your question.
Operator
And then maybe just a quick follow-up. I know there's been kind of some. Background discussion about having interest in the pre-metastatic setting, whether it's neoadjuvant and adjuvant. And just wondering kind of where you are on that now, and does the pursuit of this new loading maintenance strategy and the need to generate maybe a couple hundred patients' worth of data change, perhaps, the plans to pursue by therapists in the pre-metastatic setting? Thanks.
Rachel Frank - Investor Relations
No, I think to that question, we do believe that the locally advanced setting of head and neck has always been a large opportunity. And given the signal we've seen in the recurrent and metastatic setting, there's a strong biology to move into earlier lines of head and neck cancer. And we do believe it is also becoming a more competitive landscape as well. So we have begun initial signal sequence studies in those areas and hope to provide updates as we move forward in more detail. But we do think it is a very important opportunity that could potentially triple the market opportunity compared to recurrent and metastatic setting.
Ryan Cohlhepp - President, Chief Operating Officer, Director
Yeah, Steve, I'd say that in fact, our evolution of the dosing paradigm, I think, further supports and reinforces our ability to go into those earlier lines and head and neck cancer. And from an overall operational execution perspective, part of the key driver of our last financing was to be able to fund that.
Alternative dosing schedule as well as, continued investment in earlier areas of head and neck cancer.
Operator
Very helpful. Thanks for taking the questions.
Judith Frommer, Morgan Stanley
Judah Frommer - Analyst
Yeah, hi, guys. Thanks for taking the questions. Maybe just can you help us with an update on how many centers you're in with Fortify HN01, what overlaps are with pitocemtumab trials, and kind of what that does from a potential market share capture perspective for you, the likelihood based on investigator response for investigators at your centers to stick with.
With Ficera in the case of an approval. And then just secondarily, maybe just help us with that cash runway guidance being maintained despite the raise, what was not contemplated in the previous guide that is in there now that will eat up some of the cash that was raised to maintain that guidance. Thanks.
Rachel Frank - Investor Relations
Sounds great, and so I'll pass over the first part of the question to Tanya Green, our Development Officer, to speak to the sites and the study, and then to Ivanhire, our CFO, forecast starting.
Hi, yes, thanks for the question. So, in terms of sites, we have 129 sites that are open globally.
And in terms of the competitive overlap with the other studies, we do believe that there are some sites that overlap, but we have seen great, momentum at all of our sites in terms of patients, so that we don't see that being a consideration.
Ivan Hyep - Chief Financial Officer
And Judith, thanks for the question. In terms of use of proceeds for this recent financing, we heavily focused on alternative dosing, pre-launch activities, and investment in both commercial and regulatory. And so for us, we didn't feel that we needed to change guidance there, as it allows us to kind of build up instead of just extending runway.
Thanks.
Operator
One moment for our next question.
Our next question comes from Kelsey Goodwin with PSC. Your line is open.
Kelsey Goodwin - Analyst
Oh, hey, good morning. Thanks for taking my question.
Maybe again, just on Fortify and the enrollment, how should we think about the ultimate split of enrollment across geography? And is this similar to other trials in this setting?
And then second, in terms of the bridging trial design, I guess, do you have a sense of when you might be able to provide more color for the street? Thanks so much.
Ryan Cohlhepp - President, Chief Operating Officer, Director
Great, Kelsey.
Thank you for the question. In terms of geographical distribution on the trial, I'd say what we anticipated is it will be very similar a lot, some of the recent, trials, Keynote 48 in particular.
I think what we had anticipated and continue to see in our own enrollment is very consistent with some of those historical trials.
In terms of the alternative dosing, again, as Claire had mentioned, we intend to get regulatory input on that trial and do expect to be able to provide greater clarity later this year.
Operator
Thank you.
Our next question comes from Reni Benjamin, Citizens
Reni Benjamin - Analyst
Hey, Greg, you guys. Thanks for taking the questions and congrats on the progress. Just sticking with Fortify, can you maybe just help quantify a little bit as to what you mean by substantial enrollment? And as we think about the number of patients required for the ORR interim versus kind of the final OS, can you give us a sense as to. As to how that might look. And then just kind of related, since this would be used for accelerated approval, can you give us some thoughts on how you're thinking about more of a global filing as well for FISARA?
Thank you.
Rachel Frank - Investor Relations
Great question. So to your question around substantial enrollment, that is really predicated. On what the FDA is looking for at the time in terms of a seamless phase 2/3 design. What the FDA wants to ensure is that we are close to fully enrolled in the total confirmatory study, so as not to introduce bias at the time of granting an accelerated approval. So substantial is a key adjective for very meaningful enrollment to ensure we're not introducing additional bias into the confirmatory study. To that question, we do believe that in the United. States.
With the FDA, we are on a path to potential accelerated approval predicated on a response rate endpoint from an interim analysis that will also look at durability of response, as well as qualitative overall survival. The study will continue for full confirmatory approval on an overall survival endpoint. Today, we believe that ex-US, a full overall survival endpoint is needed. To predicate a global approval.
Thank you for your question.
Operator
Thanks for taking the questions.
One moment for our next question.
Our next question comes from Jeet Mukherjee with BTIG. Your line is open.
Jeet Mukherjee - Equity Analyst
Great.
Thanks for taking the question. Two from me. Could you speak to the rationale and reasons for confidence on the loading and once every three-week. Maintenance strategy when it was a 2,000-meg once every two-week regimen that showed a notable response and depth of response. And the second question was just related to the colorectal cancer update.
Could you confirm if the patient enrollment criteria allows for liver mets?
Thank you.
Ryan Cohlhepp - President, Chief Operating Officer, Director
Thanks for the question. So on the alternative dosing, we have gotten comfortable with our proposed strategy there. Looking at the.
Compilation of all of our data sets. I think this is where really having the 750 milligram weekly, the 1,500 weekly, and then the 2000 every two weeks has given us the ability to do extensive exposure response modeling across those data sets.
I think a couple of key notes in terms of the data, one of the things that we know when we look at the patients in our 1B data is that 1,500 milligram weekly dose, we're getting very rapid responses at 1.4. Months that we're getting responses. The vast majority of patients will have achieved the response within 12 weeks. And at that same time, most of them will have hit their maximal depth of response by the 12-week time.
And so that gives us the confidence in why we want to initiate with a weekly dosing phase and then be able to transition to extend that interval out to every three weeks.
Again, what we'll look to do is to match. The pharmacokinetic profile from both an exposure as well as a c-trough perspective to the 750 milligram weekly, which, again, we know, as you saw on that data set that we presented last year, you see really good response rates. You see really good activity, even in the 750. I think one of the things to remember here, if you recall our data, that depth of response, we're seeing more than 80% of our patients get an 80% or greater induction in their tumor. So you think they're at that 12-week mark, you've got significantly less tumor. In the patients at the 12-week mark, which gives us confidence in our ability to extend out that interval, maintain a very durable response, and give the patients the ability to have a more convenient administration schedule.
For your CRC question, the inclusion criteria does allow for liver metastases. And, in fact, the **** canal data that we have presented previously.
Really shows our ability and Pichera's ability to resolve liver metastases in that population. So it is something that we think to be a unique differentiating perspective of our molecule, and so we did allow liver mets.
Operator
Thank you.
Eva Fortia, Wells Fargo
Eva Fortia - Analyst
Good morning. Thanks for taking our question. A quick one from us.
We've seen all the three different dose cohorts with Pembro, a similar response rate or even higher in some cohorts with CPS 119 compared to CPS 20 or higher. And so, is there anything about the biology that could explain this? And if this holds in the Phase 3, could you comment on the potential implications from a commercial standpoint? Thanks.
Great question, Ava. So, to your question, it is known that, in particular, in HPV-negative head and neck cancer, there are both higher levels of EGFR and TGF-beta. That makes these tumors typically more immunosuppressive or treatment-resistant than their HPV-positive counterparts. In particular, in fact, HPV-negative tumors tend to have a slight skewing for CPS low or the CPS 1 to 19. And, in fact, it's in. Patient population that Pembro has worse response rates across the board.
And so seeing very strong response rates in the CPS 1 to 19 really speaks to the underlying biology of being able to target both EGFR and TGF beta, which is why we believe we're able to target these very immunosuppressive tumors. In fact, we do think that it's always going to be a differentiating aspect or molecule compared to other EGFR inhibitors that are currently being tested that have not seen the outside. Impact in the CPS flow. And in fact, we do believe that, especially given we are going after a chemo-sparing regimen, being able to go after these 1 to 19 will allow us to have a dominant share in what accounts for approximately 50% of the total head and neck market, but slightly skewed even higher in the HPV negative. In fact, to your question, you may remember that we also have a cohort open in the CPS zero cohort that we're trying to. Disclose at a later time point that also speaks to this underlying biology. All right, thanks.
Operator
Richard Law, Goldman Sachs
Richard Law - Analyst
Hi, everyone. This is Juan Usman on for Rich. Thanks for taking our question. Just one from us. How are you thinking about when online the study for the interim analysis for accelerator approval? Will it be based on an overall survival rate?
To your question, this is a fully double-blinded study. We will not be unblinding the study as it needs to continue for overall survival. At the time of our pre-specified statistical analysis, based off of the number of patients for overall response rates, durability, and qualitative overall survival, the IDMC will look at that data.
But as management, we will not be unblinded to the data.
Thank you for your question.
Operator
And I'm not showing any further questions this time. I'd like to turn the call back over to Claire.
Claire Mazumdar - Chief Executive Officer
Thanks, everyone, for joining us for our first quarterly earnings call and for your support of Bycara Therapeutics. There's never been a better time to be following our story, and we look forward to speaking with you all again soon.
Thank you, and have a good day.
Operator
Well, ladies and gentlemen, this does conclude today's presentation. We thank you for your participation. You may now disconnect and have a wonderful day.