My name's Keith Alexander, and I'm the CFO of ExpreS2ion Biotech. Today, I'll introduce ES2B-C001, our anti-HER2 therapeutic breast cancer vaccine that's designed for durable immune control. I'll spend some time disclosing the biologic rationale, some early preclinical data that we'd like to highlight, as well as our early clinical data that we've been able to show so far. Then finally, I'll wrap up by disclosing our 12-18 month plan that we have going forward. We're a public company, so any forward-looking comments that I might make are, of course, related to uncertainties. What is clear is we have a clear strategic plan based on the data that we receive. We have an experienced management team, and we have a clear strategy going forward with milestones. Starting with HER2 expressing breast cancer, there have been tremendous advances in therapy for that in the recent history, including with ADCs.
There still remains a durability gap, and for later-line patients, progression is expected. Between having the problem that progression is expected because the durability of current treatments does not last forever, that brain metastases can occur as the tumor is spread through the central nervous system, and then finally, that the treatment regime is quite burdensome. Therefore, there's a question about the incremental benefit of patients in this setting. Therefore, we think there's an opportunity for something new to add to the current lines of therapy. With that in mind, I'd like to introduce ES2B-C001, which is our VLP-based multi-epitope HER2 immunotherapy. The way it works is that we place the full HER2 extracellular domain on the outside of a VLP capsid. What does that mean?
We're presenting the full HER2 extracellular domain, including all four subdomains, so that we have an induced polyclonal antibody response across multiple epitopes. That's different from the current therapies which target just one epitope, or sometimes they combine two drugs to target two. By doing that, we expect to have a longer duration of response and to break tolerance to therapies that are only targeting one of the four subdomains. This approach, combining our ExpreS2 antigens with VLP platform, has been used in multiple clinical therapies, including a phase III human study with over 4,000 patients where the primary endpoint was met. Furthermore, VLPs have been used in successful cancer vaccines in the past, including HPV vaccines, Cervarix and GARDASIL, which are clearly established globally in the human population. In summary, our therapy is designed to complement the existing HER2 therapies that are being used.
It's scalable, it's off-the-shelf, and it's a recombinant production that supports potential cost efficiency. How do we position within the current treatment paradigm? What we would like to do is have our therapy be used alongside the standard of care. That means alongside antibody-drug conjugates, monoclonal antibodies, and tyrosine kinase inhibitors across all lines of care, and of course, starting with the metastatic setting. What we're trying to do is enhance the long-term durability for the patients in combination with those therapies. Furthermore, we want to try to stop progression through the central nervous system to the brain, for example. We have seen preclinical data that suggests that that will work. Of course, that needs to be established in the clinical setting as well. Let's talk a little bit about data.
We, of course, have a broad preclinical data package, so what I am doing today is just showing you a highlight. What we are showing here is a mice model where the mice are injected with tumor cells, and we see the progression of those tumor cells over time. The control is the black line here, and what we see is that the tumors will grow. When treated with our vaccine, with or without adjuvant, the growth is much less. With adjuvant, it is actually stopped completely in the preclinical setting. Furthermore, we have tested this with mice who have a tolerance to the current standard of care to monoclonal antibodies. What we show was that we are able to hinder progression of tumor growth in those resistant models as well. Of course, these are all animal models, and clinical evidence needs to be established.
Based on this, we thought that we had a good data package to go into the clinic. Let us talk a little bit about the clinical data we have so far. Right now, we are doing a phase I-A exploratory study. It is in a limited number of patients with heterogeneous background therapies. So far, what we are seeing is encouraging. We see that our treatment is generating a specific antibody response to our treatment that we know is from our treatment and not from other ones that they are receiving. It is significant, it increases, and then it is durable. It has been staying over time. More specifically, that is what I am presenting in this chart here. This is a geometric mean titer of vaccine-induced anti-HER2 lambda light chain titers. We see the increase in the titer over time.
After about five, six visits, we are seeing a high baseline level, and we see that it is durable. Eight visits here is corresponding to six months, which is as far as our most advanced patients in the trial are. What we aim to do is present more visits over time, up to one year, potentially beyond that in the phase I-A, and hopefully we see a very consistent signal. What is important to note is, of course, this antibody response, but also there have been no safety signals of concern so far. That is where we are on the data. When we combine these two, we think we are seeing things that we like to see so far. Of course, we have much more preclinical data, so if you have interest in that, I am happy to present that on a one-on-one basis later on.
Our clinical data is available on a patient-by-patient basis, which we can discuss in a one-on-one setting. Let us talk now about our plan over the next 12 to 18 months. The next year, we expect to see data maturation. In the first half of this year, we should have more immunogenicity data and safety data based on our phase I-A study. In the second half, we will have more immunogenicity data and safety data as well. We aim to have a recommended phase II dose. Then finally, we might have some efficacy data as well. I will talk about that in a moment. With all that data package in mind, we can have a clear phase II plan, and there we need to have clear decision points.
If we see clear immunogenicity that lasts and is durable, and no safety signals of concern, and a clear recommended phase II dose based on biologic activity based from the dosage, then we can say that we have something that we can take into phase II. How do we do that? There are three options, and they are to be evaluated based on what we see. We can do it ourselves, subject to funding, of course. We could partner, or we could see that we need more data. Those are the three options that we have down the road. I mentioned before that in the phase I study, we may have some efficacy data. What could that look like? It might be that we see some kind of development with metastases. Potentially, they go away. It could be progression-free survival.
It could be some of the other classical clinical signals that you look for in a phase I study. All of these would be considered supportive of our case, but not definitive. Of course, we need to have a much larger patient pool, which we would get from a phase II study. Finally, I would just like to wrap up with a brief comment about our company. We are one operating company with two value pillars. The first pillar is the one that I just mentioned, and this is our primary value driver, the ES2B-C001 HER2 VLP first-in-class active immune therapy targeting HER2. We have defined phase II decision points for the next 12 to 18 months, and we have designed this to be used in combination with the standard of care.
The next is our ExpreS2 protein expression platform, which has been used to produce over 500 proteins and with a high success rate. It has been used for biologics, for vaccines, for diagnostics, and it has been clinically validated for late-stage clinical manufacturing. I would also like to highlight that our platform has been used in a phase III trial with over 4,000 patients, and it met the primary endpoint. This program was discontinued due to variant evolution and commercial milestones. The final thing I would like to highlight is that we have a 34% ownership stake in a company called AdaptVac, which we co-developed in 2017 with researchers from the University of Copenhagen. That is where the VLP sits, and we have used the VLP in combination with our ExpreS2 antigens in multiple clinical platforms programs.
They are an independent operating company with their own oncology and infectious disease pipeline, and we see our 34% stake as offering strategic and financial optionality. With that, I will take any questions, which I am also happy to take one-on-one afterwards.