Q4 2023 Xencor Inc Earnings Call
Participants
Charles Liles; IR; Xencor, Inc.
Bassil Dahiyat; President & CEO; Xencor, Inc.
Nancy Valente; EVP & Chief Development Officer; Xencor, Inc.
Dane Leone; SVP, Corporate Strategy; Xencor, Inc.
Dylan Drakes; Analyst; Leerink Partners LLC
Etzer Darout; Analyst; BMO Capital Markets
Kaveri Pohlman; Analyst; BTIG
Brian Cheng; Analyst; JP Morgan
Tara Bancroft; Analyst; Cowen and Company, LLC
Presentation
Operator
Good afternoon and thank you for standing by. Welcome to Xencor's fourth-quarter and year-end 2023 conference call. (Operator Instructions) Please be advised that today's conference is being recorded at the company's request.
Now I would like to turn the call over to your speaker today, Charles Liles, Head of Corporate Communications and Investor Relations. The floor is yours.
Charles Liles
Thank you and good afternoon. Earlier today, we issued a press release which outlines the topics we plan to discuss today is available at www.xencor.com. Providing comments on the call are Bassil Dahiyat, President and Chief Executive Officer; Nancy Valente, Chief Development Officer; and Dane Leone, Senior Vice President, Corporate Strategy. After the prepared remarks and presentation, we will then open up the call for your questions. And we will then be joined by John Desjarlais, Chief Scientific Officer; and John Kuch, Chief Financial Officer.
Slides that we are using today should be visible here on the webcast that we've made available for download on the events and presentations page of our website. Before we begin, I would like to remind you that during the course of the conference call, Xencor management may make forward-looking statements, including statements regarding the company's future financial and operating results, future market conditions, plans and objectives of management, future operations, the company's partnering efforts, capital requirements, future product offerings and research and development programs.
These forward-looking statements are not historical facts, but rather are based on our current expectations and beliefs and are based on information currently available to us. The outcome of the events described in these forward-looking statements are subject to known and unknown risks, uncertainties and other factors that could cause actual results to differ materially from the results anticipated by these forward-looking statements, including but not limited to those factors contained in the Risk Factors section of our most recently filed annual report on Form 10-K. With that, I'll pass the call over to Bassil.
Bassil Dahiyat
Thanks, Charles, and welcome, everyone. Today we'll cover a few business highlights from 2023. briefly review our clinical pipeline, and provide a data update of vudalimab and prostate cancer. You can refer to our press release for more information about the last quarter and full year. We've focused our pipeline and discovery work on our T-cell engagers because of growing validation for their potential in solid tumors.
Supporting this is the continued advance of vudalimab in prostate cancer, we'll provide an update today and the start of a trial in front-line lung cancer for vudalimab. And we've decided to reduce our investment in our cytokine drug candidate as part of this focusing.
Our partnerships and licenses played a significant role for us last year. First, with validating data for our XmAb 2+1 CD3 platform from our partner, Amgen, with their Xaluritamig data in prostate cancer and two Phase 1 programs started in our CD28 bispecific collaboration with J&J. And we significantly strengthened our balance sheet with a partial monetization of our Ultomiris and Minjuvi royalties. As a result of that and robust milestone and royalty revenues, we ended 2023 with $697 million and expect runway into 2027.
Now, onto our pipeline. The focus of our clinical pipeline is bispecific T-cell engagers for solid tumors, an area with rapidly growing promise. Solid tumors have been challenging for antibody in cell therapies, but recent data, some of which will review momentarily, suggests that CD3 and CD28 bispecifics can play a role as therapies in a range of solid tumors.
Key programs for us addressing this opportunity are XmAb819 and ENPP3 by CD3 XmAb bispecific for renal cell carcinoma and XmAb808, a B7-H3 by CD28 XmAb bispecific in prostate and other cancers. Both are advancing a dose escalation in Phase 1. And right behind them is XmAb541, a CLDN6 by CD3 bispecific that we expect to start Phase 1 the first half of this year.
For vudalimab, we initiated a new study. Its first frontline study in non-small cell lung cancer based both on our Phase 1 data in lung cancer and external data suggesting potential advantages against stent checkpoint therapy in this setting. And we've made progress with our metastatic castration-resistant prostate cancer studies, both in combination with chemo and monotherapy and work with encouraging monotherapy data we're going to present in a moment. Finally, we're wrapping up our Phase 1 work next quarter for both XmAb564 and 662, taking the PK/PD and safety data in hand to establish initial product profiles and moderating the field for further validation of these cytokines before we do any additional development.
Underpinning our T-cell engagers are XmAb-bispecific technology. It lets us address the solid tumor opportunity by engineering our antibodies with the format and affinities designed to give tumor selectivity in the context of each tumor targets, particular expression levels in tissue distributions. Solid tumor targets in particular need a customized approach because they're distributed more broadly than human tumor targets, which have already been successfully addressed by CD3 bispecifics in lymphoma and myeloma.
Our plug-and-play antibody modules let us do this work rapidly. And as a result, we've got a growing pipeline of molecules with our 2+1 design, which is particularly helpful with selectivity for solid tumors. And here is the first clinical proof of concept for our XmAb 2+1 CD3 format, Xaluritamig, which targets STEAP1.
Our partner, Amgen, presented very promising efficacy and tolerability data at ESMO last October in late-line prostate cancer, usually considered a cold tumor for immunotherapy. This target was challenging due to the limited accessible binding regions outside the cell membrane and non tumor expression. So we're very encouraged to see this early data for the molecule in 2+1 format.
Amgen's announced they are nearing completion of the Phase 1 study and are planning additional studies in earlier lines of therapy, so we'll be eagerly awaiting their updates. Now, our own lead XmAb 2+1 CD3 bispecific is XmAb819, targeting ENPP3 in renal cell carcinoma. We chose ENPP3 as a target because it has exactly the kind of expression profile we want for a CD3 solid tumor target, much higher expression on tumor than normal tissues and nearly uniformly high expression on clear cell renal cell carcinoma. Plus, it has potential for use in select patients in a range of other tumors.
Also, we think renal cell carcinoma has a need for new mechanisms beyond checkpoint inhibitors and TKIs and a directly cytotoxic antibody could be well-positioned. 819 design gives us selectivity we wanted in vitro, and we're continuing to advance in dose escalation with both IV and subcutaneous dosing and expect to make significant progress this year toward target dose levels.
I'll shift now to XmAb808, our new T-cell engager mechanism CD28 targeting. The goal here is to activate T cells via the signal two pathway, which powerfully amplifies and sustained T-cell responses. We designed 808 bispecific format and affinities to try to drive this activation in a tumor-specific way by requiring sufficient binding to its tumor antigen, B7-H3 to turn on CD28 signaling. A key part of our approach is a lower potency CD28 binding domain that we think could give us control of CD28 signaling and improved tolerability.
We picked B7-H3 because it offers high expression across a range of tumor types creating an opportunity to potentially treat multiple cancers in combination with either checkpoint inhibitors or CD3 bispecifics. CD28 targeting has generated a lot of interest among clinicians and across the industry in the current Phase 1 study and combination with pembrolizumab is progressing well in escalation.
Now, our latest CD3 bispecific is set to enter the clinic imminently. XmAb541 targets CLDN6, which is highly expressed on the majority of ovarian cancers and also in several other tumor types. Those have a very promising expression profile. It is a selectivity design challenge because there are multiple closely homologous CLDNs.
We think we addressed it with careful bindings main engineering and our 2+1 format. XmAb541 INDs opened and we expect to be in patients the first half of this year. We're planning to apply lessons learned for solid tumor CD3 dosing from both internal and external programs to move the study quickly. Now, I'm going to turn it over to Nancy for the vudalimab update.
Nancy Valente
Thanks, Bassil. I'm excited about the encouraging new data we have just shared from the prostate cancer monotherapy cohort. We could go to the next slide. This cohort is part of the overall vudalimab program, which consists of four studies. Based on the outcome of the Phase 1 study, we moved into two tumor-specific expansions initially, the study 717-04 in metastatic castrate resistant prostate cancer in combination with standard of care chemo and other agents and study 717-05 that included patients with gynecologic malignancies and a monotherapy metastatic castrate resistant prostate cancer cohort, which I'm going to further describe.
The next slide. The prostate monotherapy cohort required patients to have RECIST measurable disease, including visceral sites and lymph node, and the patients had to have progressed after all other appropriate therapy. vudalimab was given every three weeks based as a flat dose, based on our PK analysis of earlier studies. You can see that this study enrolled a heavily pretreated patient population that had exhausted available standard of care therapies with a median of four prior therapies. 100% received prior anti-androgen therapy, although one received prior chemotherapy and 86% were ECOG 1 performance status.
As noted, the study protocol required patients with measurable disease at baseline, which is why we see a high rate of visceral metastases and high median baseline PSA. Reduction in target lesions and disease control are encouraging for such a heavily pretreated patient population as you can see on the right with a RECIST response rate of 35% and a disease control rate of 50%. And the spider plot shows we have several lasting responses and one patient with stable disease past 48 weeks.
The PSA reduction was also seen in three patients, giving a deep PSA 90 rate of 25% and a fourth patient with nearly a 50% PSA who is still on study. To describe one especially poor prognostic patient who responded well to vudalimab, this patient had three liver mets, a total disease burden of 12 centimeters and a PSA at baseline of 180 nanograms per ml and achieved a confirmed PR of PSA90 was in response for over 22 weeks.
The treatment emergent adverse events highlights the tolerability has been generally well managed by dose modifications with only two treatment discontinuations. Unfortunately, there has been one case of Grade 3 immune-mediated hepatitis. The patients treatment course, was complex, and this is the only known Grade 5 immune-mediated hepatitis event in over 240 patients that we've treated with vudalimab today.
Reviewing specific immune-related adverse events, generally, the events are what we'd expect with checkpoint inhibitor therapy. The rate of grade three events that you can see on the right were generally limited and specific to several patients. Overall, we are encouraged by the tolerability profile of the Q3 week flat dosing schedule with vudalimab.
In summary, we have observed encouraging single agent activity in heavily pretreated patient population. This is consistent with the data from the Phase 1 study in prostate cancer, where we had patients with 6 and 10 months duration of response. Vudalimab's safety profile is consistent with other checkpoint inhibitors, and we observe limited treatment discontinuations. Now I will turn this over to Dane to share comparative data to place these results in context.
Dane Leone
Thanks, Nancy. As you can see on the next slide, these emerging data support us enrolling more patients into the monotherapy cohort. We put the data into the context of the broader novel therapeutic landscape under development. It really is clear why we and our investigators during our discussion at ASCO GU were so encouraged about continuing this study.
When you compare the baseline characteristics of our patients versus our peer studies, vudalimab monotherapy cohort is among the most heavily pretreated and has the most advanced disease upon enrollment as shown by nearly all having ECOG 1 and all having measurable disease. Comparatively, only the Xaluritamig dose escalation study has enrolled similar patients that are very late-line and poor performance status.
Despite the remarkably advanced patient population, patients treated with vudalimab have comparable resist response rate versus the peer studies in this table and experienced deep PSA90 responses. Importantly, we think that resist response and deep PSA response are required for translating into effective durability of response and ultimately survival outcomes for these patients.
Regarding tolerability, using the Q3 week flat dose schedule of vudalimab has supported a manageable safety profile compared to our peers. Overall, considering the early nature of the vudalimab monotherapy cohort, we are encouraged by the clinical benefit for these advanced prostate cancer patients that have been treated well beyond current standard of care, and we look forward to evaluating a larger cohort of patients by year end.
Now on the next slide, beyond prostate cancer, we are executing on the start of our frontline non-small cell lung cancer study of vudalimab plus chemotherapy. And we are excited that the study is underway with the first patient dosed in the fourth quarter of last year. And with that, I'll turn back to Bassil for a view of our corporate goals for 2024.
Charles Liles
Thanks, Dane. Here's a look at our priorities for 2024. We're starting with a strong balance sheet. And as you can see, we're looking forward to this year, really bringing the focus to our solid tumor bispecifics pipeline where we have a lot going on for our CD3 CD28 T-cell engagers and for vudalimab. Of course, we're doing discovery work on additional CD3 CD28 bispecifics, and we'll select our next IND candidate later this year. Operator, we'll now open this call to questions.
Question and Answer Session
Operator
(Operator Instructions) Jonathan Chang, Leerink Partners.
Dylan Drakes
Hey, guys. This is Dylan Drakes on for Jonathan. Thanks for taking our question. First of all, would you be able to comment on how investors should be thinking about when they might be able to see initial clinical data from the ENPP3 study?
Bassil Dahiyat
Sure. I'll take that one. So we're not commenting on data just yet. And what we're trying to do is characterize with a sufficient patient number and follow up that outlines of the effective dose level as we pull together a dosing regime. These are CD3 bispecifics. So you want to have that -- you want to have your priming it step up this. We made great progress and we really hope that this year we'll have a lot more knowledge about it. And then when we get close to having the decision to disclose, we will tell you. So we're not guiding anything there yet.
Dylan Drakes
Great. Thanks. And if I could just sneak in one more. You guys at this stage, very well compared to the table there. But looking ahead to the go-forward vision for both mono and combination with vudalimab approaches. How do you guys set the bar?
Bassil Dahiyat
Yes. I guess maybe the mono first. Nancy, and Dane, you guys want to take that? What's the bar for advance comparables?
Dane Leone
Yeah. Sure. Great question. When we look at the patients that we've enrolled into the monotherapy cohort and we'll continue to enroll, these are patients that are as late-line as you can get and have exhausted every standard of care therapy available to them. As such, what we've really decided to do in gauging the signal that we'll have, as we hopefully get a cohort of 20 to 30 patients enrolled over the course of this year, is look at some of the contemporary studies where cabazitaxel has been used as a control arm.
And in those studies, namely the control arm for therapy or the very recently reported part two CheckMate 650, you've seen a resist response rate for cabazitaxel in that 11% to 24% range and a PSA 50 response rate of 24% to 37%. This is why we're quite encouraged with what we're seeing in the cohort now with clinical activity of adalimumab monotherapy and hopefully with a larger cohort, more follow up, we can then try and extrapolate what would be needed in terms of survival outcomes.
And cabazitaxel for reference is generally come out around eight months for radiographic progression-free survival. And right now, based on some of the durability, seems like we're pretty in pretty good shape.
Dylan Drakes
And then for the combo cohort, I guess we've got different baselines there to look at?
Bassil Dahiyat
Yeah, in the combination cohort with docetaxel, you really have to think about what docetaxel might be able to do and what would be post androgen receptor inhibitor exposure for these patients. And again, the landscape will continue to change with Pluvicto. But historically, if you're looking at the TAX 327 study, you'd be looking at PSA 50 response range of 40% to 50% and a fairly low resist response rate of somewhere around 10%. That said, the survival curves are a bit better for that line and that setting with docetaxel monotherapy. But that's kind of what you have to think about when you're doing the combination study with docetaxel at this point.
Dylan Drakes
Perfect. Thanks so much. I appreciate it.
Operator
Etzer Darout, BMO Capital Markets.
Etzer Darout
Great. Thanks for taking a question. I guess on maybe on the safety profile of belimumab, if there's any anything you can or will incorporate into the study to maybe mitigate this autoimmune hepatitis? Is this something that is just you need to this patient or if there are other things going on that you need to understand? And then also XmAb564, just wondered the decision to pause that. Was that data driven or whatever other contributing factors? If you could comment on that supposing that you have any. Thank you.
Bassil Dahiyat
Sure. So I'll talk -- going through the XmAb564, then maybe Nancy can take the question on vudalimab safety profile. So for 564, is really driven by our as much as anything by our decision to focus on our T-cell engages, our resources, our capital, and our people. And looking at how the class cytokine generally and IL2 T regs driving cytokine in particular has evolved. there's still, I think, a lot of outstanding data coming in the next year from other companies about efficacy, about how much potential does this class have.
And with our study having progressed and giving us a reasonable look at our PK/PD and safety, we think that that's the time to conserve resources and wait and see how the field evolves. We're well positioned to to ramp up again, but it's about focus now. And for 2024, pipeline focus is the key for Xencor. So it was really more just strategy driven. With that maybe, Nancy, you want to touch on the question on vudalimab?
Nancy Valente
Yeah. So I'll go back to the patient with the hepatitis death. And that's the only immune-related hepatitis death we've seen across our program with more than 240 patients treated, both in the monotherapy and combination setting. The patient had responded to therapy, but did have other treatment emergent adverse events before that, including diabetes mellitus and diabetic ketoacidosis, thyroiditis, hyperkalemia, lipase increase. So a bit of a complex course here.
We have looked across the entire program, and we don't see anything concerning relating hepatitis. As far as the protocol and the investigators, we have emphasize to the investigators to be watchful for this and communicate it with them. Protocol does include the NCCN guidelines for treatment, and it's also consistent with ASCO guidelines and other Society guidelines like the gastric GEA guidelines for monitoring and treatment. And so we do include screening a baseline for any diseases that might contribute to hepatitis, and we have frequent laboratory monitoring.
Etzer Darout
Great. Thank you for the color.
Operator
Gregory Renza, RBC Capital Markets.
Hi and thank you so much for taking our questions. This is support for Greg. Just to confirm if this monotherapy data was from a particular molecular subtype. I think that was how did the trial used to be characterized? And if I may, secondarily, from the data comparison table, I think the PSA90 look competitive, but PSA50 looks a little lower. Just curious if you have any positives on why the data looked that way?
Bassil Dahiyat
So I'll touch on the specifics of the trial in the population. So I think just to be careful, there's two studies ongoing that will we're starting prostate cancer with vudalimab. The monotherapy study. the one we discussed today is not subdivided by molecular subtype, it's people with clinically defined high-risk disease, which includes extra pelvic and visceral metastases. So that's a population that's independent of molecular subtype in that regard.
The other study, our combination with chemo study, that study is subdivided by molecular subtype. That's a different study. We didn't discuss data for that one today. We're enrolling still accrued patients and more follow-up, and we hope to have a lot more clarity later in the year on that program. And also, I guess first half of next year really bring it all together.
So that -- I just want to make sure that this is not from the molecular subtype dividing study. Maybe on the comparison table, Dane, you want to answer that one on the PSAs?
Dane Leone
Yahs, sure. That's a great question. We looked at quite extensively once we had this data cut and we're able to review the data with our investigators during ASCO GU. What seems to be is somewhat of an artifact of taking patients that are required to have measurable disease at baseline versus other studies that also include bone only. And as you can see on that table, most of our peer studies outside, maybe one with a similar mechanism of action, is more of a mixed patient population. And what we see in those studies is you will get more PSA 50s that don't necessarily correlate to a resist response as some of those patients do not have measurable disease at baseline.
In our cohort, to really get clinical benefit, those patients will need either a resist response or PSA 90. So I think there's two things there. One is PSA 50 for patients that are this advanced in their disease course, are relevant for survival outcomes, very debatable on. But what is definitely needed is those resist responses and PSA 90s.
Operator
Kaveri Pohlman, BTIG.
Kaveri Pohlman
Yeah, good evening. Thanks for taking my questions. My questions are mostly on vudalimab So first, on the safety profile, can you tell us how the safety profile looks in comparison with IPI-NIVO combination and how you are thinking about the dose that will be used going forward?
And my second question is also for the go-no-go decision. How many patients you plan to enroll in monotherapy in combination cohort for that? And is efficacy the only factor you're considering to make these decisions? And the last one is also from the same trial, any color you can provide on how many patients had bone disease and were there any responses observed in those patients? Thank you.
Bassil Dahiyat
Hey, thanks. Great. So that's a set of questions. I think maybe the one that's more just generically descriptive is your first one. Vudalimab safety versus IPI-NIVO, which is a broad kind of amorphous question, but we'll take a crack at it. And what our dose going forward is, Nancy, do you want to jump in on that one?
Nancy Valente
So overall, what we've seen so far is a safety profile that looks similar to other checkpoint inhibitors. So we haven't seen anything that says that this is markedly different in some way that wouldn't be unfavorable to the product. But I guess I could say that overall, I mean, there's a lot of data out there on IPI single monotherapy checkpoint inhibitors as well as combinations. So broadly, we're similar to that. Do you want to --?
Bassil Dahiyat
Yeah. On the dose going forward, noted in our lung cancer study, the newest study we started as well as in the monotherapy prostate study, which was which was the second newest, we have switched to a Q3 week schedule using flat doses. And I think that's given us a good feeling that the Q3 week might have some benefits over the Q2 week weight-based dosing.
With regard to IPI NIVO, even though we've got over 240 patients now, it's still hard to parse out those subtle differences. We don't see the kind of colitis that often bedeviled IPI therapy at high doses. And note, we're giving much higher doses of our drug than the current sort of IPI regime of 1 milligram per kilogram. So I think that's maybe the best we can say comparatively across such a range of studies and whatnot, but generally very checkpoint like.
And then on your second question, go-no-go number of patients that we hope to have for both the combo and mono, so by first half next year, we're looking at on the order of roughly 30 patients in each of those settings, the chemo study and in particular in the the main cohort, which is our no targetable mutations cohort, which is our now docetaxel combo. And then on our monotherapy study as well. So in that, we're aiming for 20 patients. Hopefully, we'll get pretty close to that and be able to make decisions.
Dane Leone
I think it would be helpful. Maybe, Nancy, you could just explain the difference between measurable disease, not measurable disease at baseline because I think that might be helpful for everyone.
Nancy Valente
Sure. Measurable disease, it has very basically two dimensions. And it's got to be a metastatic site in an organ or a measurable lymph node bigger than a normal lymph node. Non measurable would typically be bone-only disease or if a patient had bone-only disease. Our patients had measurable disease, and they could have also had bone disease on top of that. I can tell you two of the four responders had bone disease in addition to their other measurable disease. So we have seen responses in patients who had bony disease.
Kaveri Pohlman
Got it. That's what I wanted to know. Thank you. Thanks for the color.
Operator
Brian Cheng, JP Morgan.
Brian Cheng
Hey, guys. Thanks for taking my questions today. Maybe a first one is just on the three confirmed responders. I think just kind of piggybacking on what was the question prior to this. What was the background of the three confirmed responders? Can you just kind of give us how many lines they have and give us a sense of what their historical responses or to prior ARR or even see that they had -- some patients had, yes, radiation. So just curious like what are the responses like and I have a follow-up. Thank you.
Bassil Dahiyat
Yeah. Nancy, you could take that, all the details. I'd say they were really, really heavily pretreated in rough shape when we got them.
Nancy Valente
They had to be progressing through prior therapies. They had to have at least two prior therapies. I'm looking at the background. And they have anywhere from 3 to like 7 prior therapies, including the XRT. Sorry, I'm just looking at --
Bassil Dahiyat
Yes, that's a lot of detail, Brian. So we're (technical difficulty) up our notes.
Nancy Valente
Yeah. So one patient had three prior therapies, not including any radiation. Second patient had three prior therapies. The third patient had six prior therapies. So none of these are with radiation or counting that. And the last patient had two prior therapies. They all included docetaxel or one included carboplatin. Two had prior radiotherapy. Let me just see. I can't really comment on their prior responses. Can they be at an upcoming presentation, we could drill down into each individual patient.
Charles Liles
Yes, but suffice to say that they've seen a lot of prior therapy, Brian.
Brian Cheng
Okay. And then on a follow-up here. As you're looking at this data and I think the last time we saw the combo data, maybe back in to see, I think back in 2022, how should we think about the low hanging fruit piece? What is the lowest hanging subset of the mCRPC patients that investors should think of when it comes to vudalimab. And is that high-risk, is that genetically defined? How do you think about the low hanging fruit either with combo or monotherapy? Thanks.
Dane Leone
Yes, I think it's a great question that we're obviously going to have a fuller answer to as we get these cohorts enrolled over the course of this year and can really look for a reliable signal, hopefully and 30 patients per cohort for a monotherapy and for the combination. But the way we're thinking about it now is we just had an update on part 2of CheckMate 650 at ASCO, do you where IPI-NIVO was tried in every foreseeable combination relative to cabazitaxel?
The emergent signal that we have in the small end right now is better than anything that was achieved in that study in a comparable patient population post taxane patients. So that's step one. We think we have something differentiated that hasn't been done with an IO therapy before in this heavily pretreated patients, even going back to the table that we have looking across all of our peer studies.
And then step two is more of a question. I think you're asking of how we see the treatment landscape evolving. As everyone knows, Pluvicto is probably going to be used more and more. They had a good 2023 of commercial uptake in the United States. And so that has to be on our minds as we look through future development. But the interesting point here is the toxicity profile of vudalimab is nonoverlapping with Pluvicto. So that's one.
And secondly, there's emerging evidence presented and published late last year that treatment with Pluvicto might actually sensitize the tumor microenvironment to checkpoint targeted therapy. And this all has to be proven out in the clinic with in larger studies. And step one for us is still declining what we think the clinical profile is of vudalimab monotherapy for these have we treated them as patients with measurable disease.
But once we understand that, I think there's a number of options how to move forward in an intelligent manner for development of this drug. So we're excited for what we're seeing. Again, early days here, so we don't want to get over our skis. But we'll look for a confirmation of the signal as we move throughout the year.
Operator
Alec Stranahan, Bank of America.
Hey, guys. Thanks for taking the question. This is John. I'm on for Alex. Just a first quick question. I think this was briefly mentioned before, but just wanted to check, I didn't catch everything. But won't it be like a good benchmark or like a comparator for us to look at in comparison to the vudalimab monotherapy data presented today? That's my first question.
Second question on the quality of life data, when can we expect to see some color regarding that if you're keeping track of it? And could you maybe provide some - shed some light on what you're currently observing in the clinic in terms of quality of life and some patient reported outcomes. Thanks.
Dane Leone
That question is really a question of when we have a totality of a cohort in discussion with our clinical investigators. It is that clinical experience overall for these patients, something that we should move forward. So does that affect the totality of data? We don't know at this point, right? We want to see hopefully 30 patients in each of these cohorts. The monotherapy cohort in the dose type of combination cohort and to have that conversation with our clinical investigators.
So it's a great question, and that's really what we're hoping to answer. In terms of the first part of the question, that's why we provided the data table in the slides because each of these studies that we're looking at, our peer studies are exciting, right? We're excited about Xaluritamig and the clinical response there, but they're also limited in terms of their size and their scope and the comparability of the patients that were enrolled. S
o we don't want to make apples and oranges comparisons of novel agents for the treatment of these prostate cancer patients right now. But I think what we could say is a number of these programs, Xaluritamig is undeniable. And hopefully, our vudalimab monotherapy program as well seem to be surpassing what you could probably expect for late-line chemotherapy from contemporary studies as we mentioned, the cabazitaxel response rates and the CheckMate 650 study and the therapies study.
And then once you get to earlier lines, of therapy. I think it is a toxicity profile. And again, if it does seem that Pluvicto is sensitizing the tumor microenvironment for IO therapy, we have a therapy that does not have overlapping heme tox and could be an interesting idea to explore down the road.
Thanks for the color.
Operator
Tara Bancroft, TD Cowen.
Tara Bancroft
Hi, good afternoon. So my question is more of a general question. So are there any other combos besides chemo that you're considering or really excited about that could increase the robustness of this data? And then specifically referring to the chemo combo, how do you think safety will look in that combination. Is there any update that you can provide on how that's going now in the 1704 study? Thanks.
Dane Leone
So I guess on the first, other combos other than chemo, we think chemo is a very important one in this setting because it is the predominantly used therapy post androgen still. I think it's really interesting to imagine post Pluvicto treatment, maybe not in concert, given the intriguing immune priming activity that Pluvicto perhaps has from some small studies recently published, I think, at UCSF.
So I think those are the two top things on our mind now. But I think in the future, as we see our CD28 technology evolve, our XmAb808 program is, of course, aimed partially at least at prostate, maybe even predominantly at the moment. And as that would evolves in combo with pembro, we're certainly keeping our eye on how to maybe use that with vudalimab if the stars align, right? So that's maybe the other other big one that we're thinking of.
The future might hold combinations with CD3 bispecifics with molecules like for vudalimab. I think that's something people are looking at. They're just starting to happen in the clinic now. I'm aware of some CD3 solid tumor molecules that are being tested with checkpoints. That's maybe a little bit further off in the future, though.
And then I guess your second question was on, what can we say about safety from the ongoing 04 study, given that we're not sharing specific data? So maybe Nancy, do you want to comment?
Nancy Valente
Yeah, absolutely. So maybe I can share also that since we last presented data, we amended the combination protocol in prostate cancer to remove the carboplatin, all, but the aggressive variant. And we're really focused on the taxane, specifically docetaxel is first-line chemotherapy. And so far, based on feedback from investigators, we seem to be seeing better tolerability with these new regimens and the prior one.
Bassil Dahiyat
Operator, we have any other questions?
Operator
No, that looks like that's all.
Bassil Dahiyat
Right. Well, thanks, everybody, for joining us today and have a wonderful evening. We look forward to our next update.
Operator
Thank you for participating in today's conference. This does conclude the program. You may now disconnect.
