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Operator
Good morning, and welcome to Oncolytics Biotech's Second Quarter 2023 Conference Call. (Operator Instructions) Please be advised that this call is being recorded at the company's request. And I would like to turn the call over to Jon Patton, Director of Investor Relations and Communications. Please go ahead.
Jon Patton - Director of IR & Communication
Thank you, operator, and good morning, everyone. Earlier this morning, Oncolytics issued a press release providing recent operational highlights and financial results for the second quarter of 2023. A replay of today's call will be available on the Events and Presentations section of the Oncolytics website approximately 2 hours after its completion.
After remarks from company management, we will open the call for Q&A. As a reminder, various remarks made during this call contain certain forward-looking statements relating to the company's business prospects and the development and commercialization of pelareorep, including statements containing the company's focus, strategy and objectives, the company's belief as to the potential and mode of action of pelareorep as a cancer therapeutic.
The company's plans regarding Precision Promise and the anticipated timing of entering into a definitive agreement in connection therewith. Company's plans and expectations regarding potential registrational studies, the company's business development plans and strategies and other statements related to anticipated developments in the company's business.
These statements are based on management's current expectations and beliefs and are subject to a number of factors which involve known and unknown risk, delays, uncertainties and other factors not under the company's control that may cause actual results performance or achievements of the company to be materially different from the results, performance or expectations implied by these forward-looking statements.
Any forward-looking statement in which Oncolytics expresses an expectation or belief as to future results such expectations or beliefs are expressed in good faith and are believed to have a reasonable basis, but there can be no assurance that these statements or expectation or belief will be achieved.
These factors include results of current or pending clinical trials, risks associated with intellectual property protection, financial projections, actions by regulatory agencies and those other factors detailed in the company's filings with SEDAR and the SEC.
Oncolytics does not undertake any obligation to update these forward-looking statements, except as required by applicable laws. On our call today, we'll hear from Oncolytics' Chief Executive Officer, Dr. Matt Coffey; Chief Medical Officer, Dr. Thomas Heineman; Global Head of Business Development, Andrew de Guttadauro; and Chief Financial Officer, Kirk Look. I'll now hand the call off to Matt to give a few highlights from this past quarter. Matt?
Matthew C. Coffey - President, CEO & Director
Thank you, John. and welcome to all who have joined us this morning. We are excited by the continued progress of our current programs for pelareorep, or Pela, we'll refer to it in pancreatic and breast cancer that are accelerated towards registrational studies. In June, at the ASCO Annual Meeting, we presented results from our HR-positive/HER2-negative metastatic breast cancer program. Data from the randomized BRACELET-1 trial showed a 50% improvement in progression-free survival and a nearly threefold increase in confirmed overall response rate for Pela in combination with paclitaxel versus paclitaxel alone. This impressive data readout validated earlier Phase II results from IND 213 which showed a statistically significant near doubling of median overall survival in HR-positive/HER2-negative metastatic breast cancer patients. Meaning this program is now Phase III ready.
The company will now prioritize progressing swiftly to our registrational trial of pela-paclitaxel combination therapy in HR-positive/HER2-negative metastatic breast cancer. Our second registration program in pancreatic cancer has generated compelling data and is clearly attracting attention among at leaders in the community. This is evidenced by Pela being selected as a new investigational treatment in Precision Promise an innovative, adaptive Phase III clinical trial designed to accelerate registration pathways for pancreatic cancer therapies and expected to reduce Phase III costs by about 50% compared to a traditional trial. The study is successful, is expected to support approval of Pela in combination with a checkpoint inhibitor and the chemotherapeutic agents, gemcitabine and nab-paclitaxel for the treatment of first-line metastatic pancreatic ductal adenocarcinoma. Pela's inclusion and Precision Promise is supported by prior pancreatic cancer clinical data that suggests it synergizes with checkpoint inhibition and chemotherapy. As a reminder, our Phase I/II GOBLET study data has almost tripled the average historical objective response rate by combining Pela with nab-paclitaxel, gemcitabine and atezolizumab in first-line advanced pancreatic cancer.
However, in total, we have data from over 120 pancreatic cancer patients we have treated across multiple studies with and without chemotherapy and checkpoint inhibitors, which Tom will discuss a bit later. Our plan for this indication is to finalize agreements with the Precision Promise team by the fourth quarter of this year, and we expect to open the investigational treatment of Pela, a checkpoint inhibitor, gemcitabine and nab-paclitaxel in early 2024.
At the end of July, we announced a USD 15 million equity offering, which closed last week and was led by a health care-focused institutional investor. Our HR-positive/HER2-negative metastatic breast cancer and metastatic pancreatic cancer programs both represent meaningful registration opportunities, and this additional funding further strengthens our position to advance Pela into registrational trials. We plan to provide guidance on the registration-enabling pathway for both of these programs later this year. Now I will turn the call over to Tom and Andrew for a more detailed discussion of our clinical programs and business development efforts. We will start with you, Tom.
Thomas C. Heineman - Chief Medical Officer
Thanks, Matt. I'll begin my section by summarizing and highlighting the key data from our two pillar programs. As Matt mentioned, we are thrilled with the readout from our randomized BRACELET-1 trial of Pela combined with paclitaxel in HR-positive/HER2-negative metastatic breast cancer. These data show that Pela combination therapy led to a robust improvement in progression-free survival with a hazard ratio of 0.29 and a nearly threefold increase in the confirmed overall response rate. This will emphasize a hazard ratio of 0.9 and means the combination of Pela and paclitaxel reduced the risk of disease progression by 71% compared to paclitaxel monotherapy.
We hosted a key opinion leader webinar on June 5 to provide expert perspectives on these results and what they mean for our HR-positive/HER2-negative breast cancer programs next steps. If you miss the webinar and are interested in a more detailed discussion of the BRACELET-1 results, we encourage you to watch the replay that is available in the Events and Presentations section of our company website. As a reminder, BRACELET-1 is a randomized Phase II trial that enrolled a total of 48 HR-positive/HER2-negative metastatic breast cancer patients into three groups: the control group that received paclitaxel monotherapy, a group that received the combination of paclitaxel and Pela and a third group that received paclitaxel, Pela and the checkpoint inhibitor avelumab.
The BRACELET-1 primary endpoint was overall response rate at week 16 with additional endpoints of progression-free survival, safety and tolerability and immune biomarker evaluation. The BRACELET-1 primary endpoint of overall response rate at week 16 increased from 20% in the paclitaxel monotherapy arm to 31% in the paclitaxel Pela combination arm. The benefit of adding Pela to paclitaxel became even more apparent as the data matured, with a 37.5% confirmed overall response rate in the pelapaclitaxel combination arm compared to only 13% for paclitaxel monotherapy. Adding avelumab to paclitaxel did not improve anticancer activity, which reinforces our decision to focus on the pelapaclitaxel doublet as we move forward to our registrational study.
BRACELET-1 also includes an endpoint of progression-free survival, which has been used to support approvals of oncology drugs, including in breast cancer. We observed a robust increase in progression-free survival in the pela plus paclitaxel cohort compared to the control arm. Median progression-free survival was 6.3 months in the paclitaxel monotherapy group and increased by more than 50% to 9.5 months in the Pela-paclitaxel combination group for a hazard ratio of 0.29 as of a March 2023 data cutoff.
While the study was not designed for statistical comparisons, the progression-free survival benefit in the Pela plus paclitaxel arm did, in fact, reach statistical significance. The addition of avelumab to the Pela-paclitaxel combination did not add clinical benefit. In fact, the avelumab combination behaves similarly to paclitaxel monotherapy suggesting that the addition of avelumab actually nullified the beneficial effects of Pela.
The question of why adding avelumab may have reversed the beneficial effects of the pelarerep-paclitaxel combination therapy was discussed during our key opinion leader webinar on June 5. Briefly, avelumab is unique among licensed checkpoint inhibitors in its ability to bind Fc receptors, including those on immune cells. This may have led to the eradication of potentially protective pela induced immune responses. Translational data from the BRACELET-1 study support this hypothesis. It is important to note that overall survival results from BRACELET-1 have not been reported yet as multiple patients continue to be followed for survival.
BRACELET-1 is the second randomized Phase II study in which Pela, combined with paclitaxel provided clinical benefit in patients with metastatic breast cancer. Specifically, these data support the findings from the earlier IND 213 study in which Pela plus paclitaxel demonstrated a statistically significant near doubling of median overall survival in HR-positive/HER2-negative metastatic breast cancer patients. These two trials taken together, provide a strong foundation for a registrational study with dual primary endpoints of overall survival and progression-free survival. Incorporating progression-free survival as an endpoint offers the potential to deliver a key data readout substantially earlier than would be possible with a single primary endpoint of overall survival. Based on the findings from IND 213 and  BRACELET-1, we can now confidently move to a registrational study in HR-positive/HER2-negative metastatic breast cancer.
Next, I'd like to switch to a discussion of our pancreatic cancer program. Our Phase I/II GOBLET trial in which patients are treated with Pela plus Roche's checkpoint inhibitor atezolizumab is evaluating multiple gastrointestinal cancers and continues to make encouraging progress towards key milestones, especially in the pancreatic cancer cohort, which forms our pipeline's second core pillar.
As Matt mentioned, we are very excited that Pela combination therapy has been selected by a panel of pancreatic cancer experts as a new investigational treatment arm in the pivotal Precision Promise Phase III platform trial. The Precision Promise trial is designed to accelerate the development of promising new therapies for metastatic pancreatic cancer. The trial was designed with guidance from the FDA and optimizes the number of participants needed to generate licensure-enabling data. This, along with operational efficiencies, can accelerate late-stage development by up to 2 years compared to traditional registrational trials. The inclusion of Pela-based combination therapy in the Precision Promise trial is based on data from our prior pancreatic cancer clinical studies that support Pela's ability to synergize with checkpoint inhibition and chemotherapy to benefit patients with metastatic pancreatic cancer.
Prior data include preliminary results from our Phase I/II GOBLET study that showed a 69% objective response rate in first-line advanced or metastatic pancreatic cancer patients treated with Pela combined with atezolizumab and standard of care chemotherapy, gemcitabine and nab-paclitaxel. This compares to an average of about 25% objective response rate observed in historical trials in metastatic pancreatic cancer.
While the GOBLET study is our most recent pancreatic cancer trial, we also have data from several prior studies in this disease and have treated over 120 pancreatic cancer patients with Pela-based combination therapies. The previous studies laid the foundation for the GOBLET study as they suggested that Pela-based combination therapies could provide favorable outcomes in pancreatic cancer patients. These included improved overall survival as well as potentially beneficial immunologic effects, including the stimulation of adaptive immune responses and an influx of CD8 positive T cells into the tumors.
Looking forward, we anticipate providing updated data from the GOBLET pancreatic cancer cohort as well as updates from the advanced anal and metastatic colorectal cancer cohorts in the second half of the year. We will also provide additional guidance on the path towards registration in pancreatic cancer later this year. Rounding out our recent clinical news at ASCO this year, we also presented additional preclinical analysis pertaining to Pela's ability to improve CAR T cell therapy in solid tumors.
These studies were conducted at the Mayo Clinic in collaboration with Dr. Richard Vile, and followed a publication in Science Translational Medicine last year that reported Pela's ability to synergistically enhance CAR T cell efficacy in murine cancer models.
Specifically, Pela has shown the potential to enable CAR-T therapy to effectively treat solid tumors by addressing the most challenging roadblocks for this type of therapy, including reducing antigen escape, improving T cell perseverance, overcoming the challenging solid tumor microenvironment and notably, demonstrating that AppellaBoost can enhance efficacy, including cures in 80% of murine solid tumor cases. And with that, Andrew will now speak about our business development efforts. Andrew?
Andrew R. de Guttadauro - Global Head of Business Development & President of Oncolytics Biotech (U.S.) Inc
Thank you, Tom, and good morning, everyone. From a BD perspective, the top line data readout from our BRACELET-1 trial was the featured headline of the quarter. As the BRACELET-1 data mature and we integrate data that we've already generated from IND 213 and AWARE-1, we'll be able to better leverage the full suite of immunotherapeutic effects of Pela in breast cancer.
As we move towards registration, we plan to pursue the most advantageous global clinical and commercialization partnership. We have already established several relationships with leading biopharma companies like Pfizer, Roche, Merck Serono and others. This initial interest came from our previously reported IND 213 study, which demonstrated a statistically significant near doubling of median overall survival in HR-positive/HER2-negative metastatic breast cancer patients, the same population that was treated in BRACELET-1. Having seen the BRACELET-1 study data made public in June at ASCO, additional biopharma companies have come forward, and we have just begun meaningful discussions with certain potential new collaborators.
While it is too soon to speculate on a potential deal at this juncture, it has been encouraging to have an uptick in interest from the biopharma community. We plan to foster these relationships to generate competitive tension between potential partners to ensure we reach the optimal deal for the future of Pela and our shareholders at the right time.
On the pancreatic cancer front, we reported interim data from the GOBLET study in November of last year, and we announced we received Fast Track designation from the FDA in December. The effect of these news events are still being felt in the Precision Promise announcement Tom discussed. What some people may not realize is the vetting process for pelareorep to be included in the Precision Promise platform trial was quite rigorous. We had meetings and presentations with multiple pancreatic cancer top U.S. key opinion leaders over the course of several months where they reviewed the GOBLET data, but also multiple historical pancreatic cancer studies that in aggregate have included over 120 pelareorep patients.
We were very pleased to have been selected for this Phase III opportunity, and we look forward to a productive relationship to bring better treatment options to pancreatic cancer patients. We also continue to be excited by the preclinical CAR-T results presented at ASCO and in Science Translational Medicine. CAR-T therapies generated more than $1 billion in sales last year and a subset of cancer patients with hematological malignancies. The potential for pellets to enable CAR-T therapies in solid tumor indications represents an opportunity for us to expand what is an already large market and solid tumors are the vast majority of the cancers diagnosed each year.
Our strategy is to engage potential partners with the goal of out-licensing pellets development as an enabling technology for CAR T therapies, which would allow us to participate in the lucrative upside potential CAR-T commercial opportunity with minimal risk and a continued focus on our current core clinical programs in breast and pancreatic cancer. The impressive and growing safety database for Pela, combined with numerous leading anticancer agents without causing unacceptable toxicities has been exhibited across many combinations and indications. This supports the case for continued development of Pela as an immunotherapy backbone that can enhance the efficacy of other agents and continues to be a strong selling point in our conversations with potential partners who are interested in harnessing its immunologic effects to maximize the commercial impact of their own drugs and therapeutic candidates. Next, I'll hand it to Kirk to discuss our recent financial results. Kirk?
Kirk J. Look - CFO
Thank you, Andrew. I'm pleased to report that Oncolytics continues to improve its financial position. As Matt mentioned at the start of our call, we successfully raised USD 15 million through a public offering led by a health care-focused institutional investor. These funds, along with our existing resources allow us to move forward with the definitive agreements for the Precision Promise study and obtain the necessary regulatory approval to start enrollment. With the ASCO BRACELET-1 data in hand, we can continue to move forward with the regulatory process seeking FDA advice and guidance on a registrational study in HR-positive/HER2-negative metastatic breast cancer.
As of June 30, 2023, we had $24.4 million in cash, cash equivalents and marketable securities compared to $32.1 million as of December 31, 2022. After the close of our recently announced public offering, our pro forma cash balance stands at $42.7 million and our anticipated financial runway now extends towards the end of 2024.
Our general and administrative expenses for the second quarter of 2023 were $3.5 million compared to $2.8 million for the same period last year. Now the increase is primarily due to higher investor relations activities and a rise in costs associated with our Annual General Meeting. Research and development expenses for the second quarter of 2023 were $3.7 million compared to $3.2 million for the same period last year. The increase coming from higher manufacturing and personnel-related expenses, partly offset by lower BRACELET-1 study costs.
Now the net loss for the second quarter of 2023 was $7.4 million compared to $5.1 million in the second quarter of 2022. This equates to a net loss of $0.12 per share for the second quarter of '23 and $0.09 per share for the second quarter of 2022. This completes my financial review and brings us to Matt's closing remarks. Matt?
Matthew C. Coffey - President, CEO & Director
Thanks, Kirk. Now before moving to the Q&A, I'll provide a brief recap of all the exciting milestones we expect to achieve by the end of the year. We plan to provide updates at ESMO in the second half of the year from GOBLET patients in our first-line pancreatic cancer cohort and third-line metastatic colorectal cancer cohort. We also anticipate providing additional guidance on the registrational pathway for both of our core programs in pancreatic cancer and HR-positive/HER2-negative metastatic breast cancer. The BRACELET-1 overall survival data continues to mature, so we'll provide an update on that time line once we can provide a reasonable expectation. As always, I would like to express my gratitude for all the contributions from our collaborators, talented employees, dedicated investigators, the patients participating in our studies and, of course, all of our investors. We'll now open the call up for questions. Operator?
Operator
(Operator Instructions) And your first question will be from Patrick Trucchio at HCWinright.
Patrick Ralph Trucchio - MD of Equity Research & Senior Healthcare Analyst
Congrats on all the progress. I guess just a couple of questions from me. The first is, can you talk a little bit about the pace of enrollment in the Precision Promise program and specifically, how much influence will you have on the conduct of this program. And how is it expected to accelerate the registrational pathway for pelareorep? And then secondly, also regarding this program, what would you expect to be necessary to lead to an accelerated approval pathway in pancreatic? And when might you have that first data cut from the program?
Matthew C. Coffey - President, CEO & Director
Patrick. That's a great question. Tom and Andrew are probably closest to this all. Tom talked to the regulatory acceleration and the benefits of working in this. And I think Andrew might want to weigh in a little bit on what their presumed time lines are based on the enrollment assumptions that they've made public. Tom, do you want to kick us off a little bit?
Thomas C. Heineman - Chief Medical Officer
Sure. So the -- yes, so the benefits of working with Precision Promise, where there are several benefits in addition to the cost considerations. One of the benefits is that the Precision Promise protocol is already a well-established study that has been vetted by and discussed at length with the FDA. And so we have already a very solid -- we know that we're entering a study with a very solid clinical program, a very solid clinical pathway.
The study is already working with well-established and in fact, many of the best academic sites in the U.S. so that we have a whole access to a large number of pancreatic cancer experts, and they're all very experienced, not only in pancreatic cancer, but in with this particular study. And so there is a very solid group of partners with whom we will be working right away, which will not only enhance the enrollment, but also provide us with individuals with whom we can work, who can help us make sure that everything is going smoothly with the study and deal with any issues that might arise during the study. And from a regulatory perspective, as I said, this study was developed and discussed already with the FDA.
And so if everything goes smoothly, and we come out the other end with the anticipated positive results, then there should be a clear path towards a BLA submission directly from the results of the study without having to do additional studies subsequently. So that's some of the benefits of working with them in addition to the operational benefits, which are working with sites, as I said, who are very experienced already since the study is up and running, we do not -- we can save time because we will not have to do things like initiate sites and get everyone familiar with the protocol. So I think that there are obvious operational efficiencies in addition to the regulatory benefits and the access to the strong experts in the field.
Matthew C. Coffey - President, CEO & Director
That's the number of sites and the anticipated enrollment, I think we're targeting, what, 18 months after the time of initiation for that first read.
Andrew R. de Guttadauro - Global Head of Business Development & President of Oncolytics Biotech (U.S.) Inc
Yes, about that. We expect we'll sign the agreement in the next couple of months, hopefully, somewhere around there. And then it's about 17 months to get to go/no-go analysis. So figure around the first half of 2025, we'd have that initial read, Patrick, because of the fact that -- and this is much faster than if we had to start this organically, as Tom was saying, where you have to start every site. In terms of number of sites, they are at 28 sites, what's unique about the site is they're all brand name top sites with some of the most famous pancreatic KOLs in the industry. So you're talking about places like MD Anderson, Memorial Sloan Kettering and the like. So they can recruit fast because that's where patients are referred to for something as intractable as pancreatic. So they've given us their projections. We're pretty positive that we can get to that go/no-go decision around the first half of 2025. Assuming everything moves forward as planned with the execution of the definitive agreements and other paperwork that needs to be put in place, and that's already ongoing as we speak.
Patrick Ralph Trucchio - MD of Equity Research & Senior Healthcare Analyst
Right. Got it. That's really helpful. And I'm wondering if you can discuss further some of the preclinical research collaboration evaluating pela plus CAR-T combination. And when you might have further details to present?
Andrew R. de Guttadauro - Global Head of Business Development & President of Oncolytics Biotech (U.S.) Inc
That's a great question. So we do have companies we've been public about without naming whom who are testing our pelareorep with their CAR-Ts because we believe that largely, for instance, with PD-1 L1, we work pretty well with all of them with the exception of one that had the Fc portion discrepancy. That's not the case with CAR-Ts. CAR Ts, as you know, are very particular, both to the antigen, their constructs, how they're made and what they target. And so we really have to go one by one with companies that are interested and have our Pela tested with their construct. So far, the results have been promising. But I don't know yet when those will be presented because a lot of that is really in the hands. It's dependent on the type of agreement and how willing the company may be to share those results publicly quickly, especially if it confers a potential advantage in moving forward. But certainly, before anything moves into the clinic, they would have to sign a definitive licensing agreement with us to allow them to do that work. And so at that point, we would make something more public for sure.
Operator
Thank you. Next question will be from Soumit Roy at Jones Research.
Soumit Roy - Director & Healthcare Analyst
Congratulations on all the progress. On the breast cancer front, trying to understand how stringent was the enrollment criteria for the HER2-negatives. Do you think there were some HER2 to lows were considered prior to reemergence of HER2 to low to be actually effective against HER2 therapies. So trying to understand if how stringent was the enrollment criteria? And what went right in fact, with your 15,16 patients on each arm trial that is giving you the confidence that in the registration trial, you want to have that kind of enrollment criteria that would continue the success?
Matthew C. Coffey - President, CEO & Director
Tom, do you want to jump in and talk about sort of the evolving HER2 status and what that means potentially going forward and why we're so confident that this study is replicating what we're seeing with IND 213.
Thomas C. Heineman - Chief Medical Officer
Sure. So when this study was enrolled, of course, the concept of HER2 low as a marker for specific therapy was not in play yet, right? The antibody drug conjugates had not been approved. So patients -- so we do -- so we are -- I'm quite sure that in this study, both we enrolled both HER2 negative and HER2 low patients, as would have been expected in a study like this. But the reason that we're confident that the data from this study provide a basis for moving forward is that in this population, these are patients who had failed standard of care hormonal therapy, including CDK4/6 patients.
So this is a population that is very typical of patients who with metastatic breast cancer who are now ready for chemotherapy. And in this population, we saw a very strong objective response rate and PFS benefit. And so going forward, these patients are still going to exist in the real world even with the advent of the antibody-drug conjugates because some patients, as you know, will not be eligible for antibody drug conjugates, and they will need options.
But even perhaps more importantly, there are going to be patients who receive antibody drug conjugates who then fail those because as good as say or they are not cures. So once patients are treated with antibody drug conjugates and then progress, they will also need treatment options, and we believe that the pela based combination will be a very potentially beneficial treatment for both patients who are antibody drug conjugate in (inaudible) and those who ultimately fail antibody drug conjugate therapy.
Soumit Roy - Director & Healthcare Analyst
So for the registration trial, how would you set up the enrollment criteria? Would you make it strictly as HER2-negative or you would be more amenable to depending on the physicians' choice if they are ready.
Thomas C. Heineman - Chief Medical Officer
Well, I think -- I mean, this is a matter for ongoing discussion, including ultimately with the FDA. But I think we can pretty confidently say that there is a medical -- a population with a substantial medical need that we can define in the Phase III population, right? So whether the exact details need to be worked out, but it's likely to include, for example, patients who have failed antibody drug conjugate therapy plus or minus perhaps those patients who are ineligible for antibody drug conjugate. So there are plenty of patients out there who are going to need options. And I don't think we'll have any trouble to finding a population in Phase III that can address that need.
Soumit Roy - Director & Healthcare Analyst
Understandable. And just one last question. When should we expect the update on the registration trial for breast cancer? Is it more like end of the year? And the second is -- third is the pancreatic cancer trial, do we know the primary endpoint? Is it the PFS or the OS?
Thomas C. Heineman - Chief Medical Officer
Yes. I mean for the pancreatic cancer trial, the -- it will be overall survival, right, as is typical customary in pancreatic cancer studies. Perhaps I'll let Matt comment on the update of the breast cancer.
Matthew C. Coffey - President, CEO & Director
So we're letting the OS actually develop just to make sure that we have the likelihood of a dual endpoint. We're still actually tracing or tracking patients who are just receiving paclitaxel plus pela. So we haven't even got us the full PFS actually on that, which is fascinating because arm-1, we didn't even get anyone out to like 12 months, and we know we have patients out at cycle 22, 23 now. What we sort of suspect will happen is we're in discussion with a number of groups, as Tom alluded to, we think it's probably easiest to capture this population in the post [EDAC]. So people would go from a CDK4/6 to a first-line EDAC . That we're just seeing people get on to first-line EDAC now. We do anticipate after San Antonio, there will be more of these patients. So we're thinking about a sufficient pool of patients will be available mid next year.
In terms of regulatory filings, we'll be reaching out to the agency this year. So we're hoping for the ability to provide some regulatory guidance late this year, early next half as the OS matures. But some of this, of course, is just scheduling with the FDA and of course, the parties we're talking to who have vested interested in the EDAC would obviously like us to not cannibalize those sales, but rather be accretive to them by just tracking the same patients that are going to be able to receive the HR lows. And presumably, soon, as I'm sure you know at ASCO, the true HR-negative patients, there's literature now saying you can test a patient and have them be negative tested again and they'll be slightly positive. So the whole concept around what is an HR-negative patient, I think, is in flux. So I think by doing our regulatory filings this year, we'll have more color around what the true nature of the patient population is. But as Tom said, there's no shortage of these patients. So we're very confident we'll get to a definable patient population that the stakeholders and the FDA can agree with.
Operator
(Operator Instructions) And your next question will be from John Newman at Canaccord.
John Lawrence Newman - Principal & Senior Healthcare Analyst
So Matt, I just had a kind of a follow-up question on the ADCs. How do you think about pelareorep excuse me, being used long term with ADCs. Do you kind of -- do you see a pathway here where perhaps you get your initial approval in combination with chemotherapy, but then you're able to perhaps investigate a combination with ADCs. And if so, is there a specific subset of patients that you think might be more attractive for that combination?
Matthew C. Coffey - President, CEO & Director
Yes. No, absolutely. To the first part of your question, what we would look to do is go after 8 failures who are still taxing naive. So similar to the patient population that we treated on BRACELET, in terms that they would be taxing naive. We don't think that [EDACS] are especially immunosuppressive. They're actually deemed to be quite -- I don't want to say mild, but mild in terms in comparison to chemotherapy.
So, we don't think this would be something that would diminish the immunological response. In terms of ultimately combining with EDACS , we are very interested in that possibility -- what we know of our agent is anything that causes the cellular stress does lead to susceptibility, especially in the context of not being immunosuppressive, that has always been a concern of the company that would be using too high chemotherapy that you would blunt the immunological response to this. What we are seeing is the product does seem to work better in patients that have better immunological status or basically just saying it works better in patients who aren't as heavily pretreated.
So we do think that there is a role for combining this with EDACS . That would be part of our life cycle management and it is something that stakeholders have actively asked us to pursue. So it is obviously an area of interest for us.
Operator
And at this time, gentlemen, it appears that we have no other questions. Please proceed with any closing remarks.
Matthew C. Coffey - President, CEO & Director
Well, thank you, operator, and thanks to all who joined our call today. Have a great day. Thanks very much.
Operator
Thank you, sir. Ladies and gentlemen, this does indeed conclude your conference call for today. Once again, thank you for attending. And at this time, we do ask that you please disconnect your lines.