Okay. I will be making forward-looking statements today, and I refer you to our regulatory filings for details of those. So, Compass is based in Boston. We're a monoclonal antibody discovery and development company, and we currently have three drugs in the clinic: two bispecific antibodies and a monoclonal antibody. Our lead program, which we call CTX009, is a DLL4 VEGF-A bispecific antibody, and we had a very high response rate in patients with biliary tract cancer in a phase II study that led to the design of a randomized trial to potentially support a U.S. license application. And I'll talk more about those data in a couple of minutes. We're very lucky. We're very well-funded. We ended Q3 with $135 million in cash, which is cash runway into 2027, and we have, you know, a really great list of institutional holders.
This slide is a summary of our current pipeline. The presentation is then divided by drug. Our lead drug, again, that we call 009, is a DLL4 VEGF-A bispecific antibody. We're currently in a randomized trial in patients with biliary tract cancer, and again, I'll talk more about the data that supported the design of that study. We recently completed a phase II study in patients with colorectal cancer, where we saw monotherapy responses in patients treated in the third and fourth-line setting, and I'll talk more about our plans for next steps in colorectal cancer. Our second program is a drug we call 471. That's a monoclonal antibody agonist of the target CD137, also known as 4-1BB. We recently completed a post-checkpoint inhibitor basket study, and we saw really incredible responses in that study, and I'll show an example of one of those.
We had five confirmed responses in the post-PD-1 patient population, which is, I think, one of the highest response rates in that patient population that has been seen. And recently, at the SITC meeting in Houston, we presented data indicating that we may have identified a biomarker of response. I'll show that data today and talk about how we plan to use that. Our third drug in the clinic is a really interesting drug. It's a PD-1/PD-L1 bispecific antibody, to our knowledge, the only one in that class right now. That drug came out of a screen for synergy with PD-1 blockade. As I mentioned, that drug is in the middle of dose escalation phase I now, and I'll talk more about that drug in a couple of minutes. And finally, in terms of our preclinical research, obviously, this group, this audience knows the field of VEGF-IO bispecifics quite well.
We've been working on that field for about 18 months or so, and in the coming year, we expect to nominate a development candidate and bring our fourth drug into the clinic, so let's talk more about CTX009. Again, a DLL4 VEGF-A bispecific antibody. DLL4 is the cell surface ligand for NOTCH1. Both of these pathways, DLL4 and VEGF, are involved in angiogenesis in the tumor microenvironment, so this bispecific is a next-generation angiogenesis inhibitor, so in phase I studies of this drug, we had a set of signals of activity in patients with gastric cancer, colorectal cancer, and importantly, biliary tract cancer. In a small Phase Ib study, we had a couple of responses in patients with advanced biliary tract cancer that was quite unexpected.
That study, of course, was an all-comer study, but that observation was so important that it led us to the design of a phase II study, and here is that design. So, these are all patients with advanced biliary tract cancers who had received either one or two prior lines of therapy. So, this is a mixed second and third-line patient population. All patients received 009 IV biweekly in combination with the chemotherapy drug paclitaxel. We picked paclitaxel because we had observed responses in that Phase Ib study that I recently mentioned. So, this study was designed to confirm the observation from the Phase Ib study, and we saw something really, frankly, quite extraordinary here. So, in 24 patients, we had nine confirmed partial responses for an overall response rate intent to treat, mind you, of 37.5%.
The three-drug chemotherapy combination FOLFOX in this patient population has a 5% response rate. So, this was an extremely unusual observation. Color-coded here by anatomic subtype, so we had at least one confirmed response in all of the anatomic subtypes of biliary tract cancer. And just to sort of state the obvious here, every patient is below the line. So, this is an extremely unusual-looking waterfall in that every patient who was treated had some measurable decline in their linear tumor burden. A couple of other observations from that study. Again, the response rate, median progression-free survival 9.4 months, median overall survival 12.5 months. I'll put that into context a couple of slides from now. A really solid median duration of response of just under seven months.
And one interesting observation from this study: in the top right here, among the nine confirmed responses that we observed, seven of those nine were observed in patients treated in the second-line setting, and that observation informed the design of our randomized trial. On the safety side, in every study that we've done, hypertension is the most common drug-related adverse event, which is on mechanism for VEGF blockade. We see virtually identical levels of hypertension that you see with Avastin. So, this is the study that we are currently running. So, after we shared those data with U.S. regulators, we iterated on a design of this study, and here's where we are today. We're running a study which is a two-to-one randomization of 009 with paclitaxel versus paclitaxel alone. Overall response rate is the primary endpoint of this study.
This study is 90% powered to detect a difference in response rate of 33% versus 10% in the control arm. Progression-free survival and overall survival are the key secondary endpoints in this study, and we are positioning this regimen of 009 plus paclitaxel to become second-line standard of care in this disease. Here are a set of regimens that are used in this patient population. Front-line patients get two different chemotherapy drugs, cisplatin and gemcitabine, in combination with a checkpoint inhibitor, either durvalumab or pembrolizumab. Those regimens in the front-line setting have response rates in the 27%-28% range, progression-free survival in the six-seven-month range, and overall survival just more than a year. A small randomized study that was done in patients in the second-line setting compared the three-drug combination FOLFOX, 5-FU, leucovorin, and oxaliplatin with BSC, best supportive care. Those patients received nothing in the control arm.
5% response rate to FOLFOX, 0.9-month improvement in median overall survival. Our study in a mixed second and third-line population, 37.5% response rate, PFS and OS, comparable to what you see with the three-drug regimens in the front-line setting. So, an unequivocal signal of efficacy that we are now testing in our randomized trial. So, we are positioning this regimen to become the consensus second-line standard of care in this disease, and this disease is quite common. It is far more common than you might think. The claims aggregator Komodo Health did an analysis of U.S. claims data in 2021 and 2022, and they found there were approximately 23,000 patients annually, new patients, in the United States alone. Again, that was 2021-2022 data. We are currently working with Komodo, and we know that the 2023 number is significantly higher than this.
And after a patient receives front-line therapy with chemotherapy plus a checkpoint inhibitor, unfortunately, there's no consensus second-line standard of care, and only about 15% of patients are eligible to receive a targeted therapy such as an FGFR2 inhibitor, an IDH1 inhibitor, or a HER2 targeted agent. So, doing some fairly simple math here, making some assumptions about the fraction of patients that would get to second-line therapy, fraction of patients who might be eligible for a targeted therapy, we believe there are more than 15,000 patients annually in the United States alone that could get this regimen. And any sort of simple assumptions about pricing, our analysts, our covering analysts, have some assumptions about pricing if you're interested. And time on drug, this is well north of a $1 billion market annually in the United States alone.
So, we're now preparing potentially for commercialization of this drug, and our next steps on the development side, on the far left, interestingly, in our current randomized second-line study, MD Anderson was the second largest enroller in that study, and they've come to us with a proposal to do an investigator-sponsored study where they're adding 009 to the front-line regimen of gemcitabine, cisplatin, and durvalumab. So, that's a very interesting development. That study is ready to go, probably enrolling the first patient in the next month or two. Completing our randomized trial, again, a top-line readout from that study by the end of Q1 of the coming year, so we're within about four months from a readout from this randomized trial, which will then guide us to our commercialization preparation.
I didn't have a lot of time to talk about this today, but we're looking at biopsy specimens from a recently run phase II study in patients with colorectal cancer, looking at DLL4 status of those patients' tumors to prepare for a potential second-line study where we combine 009 with chemotherapy in patients with DLL4 positive colorectal cancer. Ultimately, our goal here, of course, is to replace Avastin with 009 in all of the Avastin indications, and this will be one of the first steps toward achieving that goal in patients with colorectal cancer. So, in the last couple of minutes, I'll talk about our two other drugs in the clinic. 471, again, a CD137 agonist antibody that was both affinity and epitope optimized for binding and activating this target. We completed a phase I study, and then we did a Post-PD-1 basket study.
The post-PD-1 patient population today is probably one of the most challenging populations, frankly, in medical oncology. We enrolled patients with 17 different tumor types. We saw several responses in melanoma. We had three out of 11 patients treated for a 28% response rate post-PD-1. We had one out of four patients with mesothelioma, and we have a really remarkable response in a patient with small cell lung cancer. Here are CT scans for this patient. Just to orient you, patient lying on their back, black is air in the lungs, gray and white are tissues. This patient had metastatic small cell lung cancer, received front-line therapy with chemotherapy plus a checkpoint inhibitor, atezolizumab, was on that regimen for about four months and progressed, meaning their tumor became larger. Second-line nivolumab, the PD-1 inhibitor, was on that regimen for about two months and progressed.
In October of 2020, this patient began therapy with CTX471. PR that deepened and was incredibly durable, month 32. This patient was on drug for more than three years. Some conversations with the investigators, we got a PET scan on this patient, and the patient was completely tracer negative. So, this patient is a PET negative complete response. When looking at this patient's biopsy, we discovered that this patient's biopsy specimen was covered with NCAM, CD56, which led us to investigate other biopsy specimens for CD56 expression, and we found that the patients who did well with the drug were all CD56 positive. Patients whose tumors were CD56 negative did not do well. So, a really interesting observation. Does this make any sense? So, CD56 is its own receptor and ligand. So, CD56 negative tumors cannot attract NK cells into the tumor microenvironment.
CD56-positive cells attract NK cells where CD137 is upregulated and it can be activated by 471. So, a really interesting observation that we're going to test in a basket study. Patients with NCAM-positive tumors, which is a marker of neuroendocrine differentiation, is seen in a whole set of different tumors, including prostate cancer among others, and it is a substantial patient population in the U.S. looking to begin a basket study in the NCAM-positive patient population to begin in the middle of the coming year. And then finally, we developed a technology at Compass to screen for synergy and bispecific antibodies. We call that technology StitchMabs. We asked an incredibly simple question: in a bispecific antibody, what is the best combination partner for PD-1 blockade? And we discovered that it was actually PD-L1 blockade.
Dual receptor ligand blockade in a bispecific antibody is between 100 and 1,000-fold more potent than either antibody alone. But fascinatingly, it's not just dual ligand receptor blockade. The bispecific induces cleavage of PD-1 off the surface of effector T cells. It's a really unique mechanism of action. It is superior to known PD-1 or PD-L1 blockers in preclinical studies, and we're now doing a phase I study. This is a standard dose escalation study looking at patients with melanoma, non-small cell lung cancer, head and neck, Hodgkin's lymphoma, and triple negative breast cancer. We're in the middle of that phase I study now, moving to the third dosing cohort. This is my last slide. So, 2025, I think, is going to be a very important year for us.
We're going to get a readout from our randomized biliary tract cancer study by the end of Q1, beginning two additional clinical trials, nominating our fourth drug in the clinic, and a readout from our 8371 phase I study. So, I'll thank you very much for your time. I think we have a couple of minutes for questions. We don't. Okay. Thank you.