Xencor Inc Q4 FY2023 Earnings Call

Good afternoon, and thank you for standing by. Welcome to Xencor's Fourth Quarter and Year End 2023 Conference Call. At this time, all participants are in a listen-only mode. After the speakers' presentation, there will be a question-and-answer session. 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.

Thank you, and good afternoon. Earlier today, we issued a press release, which outlines the topics we plan to discuss today. It's 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 and we've made available for download on the Events & 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.

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 on vudalimab in prostate cancer. You can refer to our press release for more information about the last quarter and full year. We 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, where we'll provide an update today, and the start of a trial in front-line lung cancer for vudalimab. We have decided to reduce our investment in our cytokine drug candidates as part of this focus. 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 second, Phase 1 programs started in our CD28 bispecific collaboration with J&J. We significantly strengthened our balance sheet with a partial monetization of our Ultomiris and Monjuvi royalties. As a result of that and robust milestone in 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 and cell therapies. But recent data, some of which we'll review momentarily, suggests that CD3 and CD28 bispecifics could play a role as therapies in a range of solid tumors. Key programs for us addressing this opportunity are XmAb819, an ENPP3 x CD3 XmAb bispecific for renal cell carcinoma, and XmAb808, a B7-H3 x CD28 XmAb bispecific in prostate and other cancers. Both are advancing in dose escalation in Phase 1, and right behind them is XmAb541, a CLDN6 x CD3 bispecific that we expect to start Phase 1 in the first half of this year. For vudalimab, we initiated a new study, its first front-line study, in non-small cell lung cancer, based both on our Phase 1 data in lung cancer and external data suggesting potential advantages against standard checkpoint therapy in this setting. We have made progress with our metastatic castration-resistant prostate cancer studies, both in combination with chemo and monotherapy, 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 XmAbs 564 and 662, taking the PK, PD, and safety data in hand to establish initial product profiles and monitoring the field for further validation of these cytokines before we do any additional development work. Underpinning our T-cell engagers is our XmAb bispecific technology. It lets us address the solid tumor opportunity by engineering our antibodies with a format and affinities designed to give tumor selectivity in the context of each tumor target's particular expression levels and tissue distributions. Solid tumor targets, in particular, need a customized approach because they're distributed more broadly than heme 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. 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 the 2+1 format. Amgen has 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 and 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. Additionally, we believe renal cell carcinoma has a need for new mechanisms beyond checkpoint inhibitors and TKIs, and a directly cytotoxic antibody could be well positioned. 819's design gives us the 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 2 pathway, which powerfully amplifies and sustains T-cell responses. We designed 808's 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 in combination with pembrolizumab, which is progressing well in escalation. 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 on several other tumor types. Though it has 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 binding domain engineering and our 2+1 format. XmAb541 binding is open and we expect to be in patients in 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.

Thanks, Bassil. I'm excited about the encouraging new data we have to share from the prostate cancer monotherapy cohort. If 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 with RECIST measurable disease, including visceral sites or lymph nodes, and the patients had to have progressed after all other appropriate therapy. Vudalimab was given every three weeks 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 antiandrogen therapy, all but 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%. The spider plot shows we have several lasting responses and one patient with stable disease past 48 weeks. Deep PSA reduction was also seen in three patients giving a PSA90 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 metastases, a total disease burden of 12 centimeters and PSA at baseline of 180 nanograms per milliliter, and achieved a confirmed partial response, a PSA90, and was in response for over 22 weeks. The treatment-emergent adverse events highlight that tolerability has been generally well managed by dose modifications with only two treatment discontinuations. Unfortunately, there has been one case of Grade 5 immune-related hepatitis. The patient's 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 to date. Reviewing specific immune-related adverse events, generally, the events are what we'd expect with checkpoint inhibitor therapy. The rate of Grade 3 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 six and 10-month duration of response. Vudalimab's safety profile is consistent with other checkpoint inhibitors, and we observed limited treatment discontinuations. Now, I will turn this over to Dane to share comparative data to place these results in context.

Thanks, Nancy. As you can see on the next slide, these emerging data support us enrolling more patients into the monotherapy cohort. When you 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 the study. When you compare the baseline characteristics of our patients versus our peer studies, the 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 in poor performance status. Despite the remarkably advanced patient population, patients treated with vudalimab have comparable RECIST response rate versus the peer studies in this table and experience deep PSA90 responses. Importantly, we think that RECIST 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 dose in the fourth quarter of last year. And with that, I'll turn back to Bassil for a review of our corporate goals for 2024.

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 and CD28 T-cell engagers and for vudalimab. Of course, we're doing discovery work on additional CD3 and CD28 bispecifics, and we'll select our next IND candidate later this year. Operator, we'll now open this call to questions.

Thank you. At this time, we will now conduct the question-and-answer session. Our first question comes from Jonathan Chang of Leerink Partners. The floor is now yours.

Hi, guys. This is Dylan Drake on for Jonathan. Thanks for taking our questions. First of all, would you be able to comment on how investors should be thinking about when we might be able to see initial clinical data from the ENPP3 study?

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 the sort of outlines of the effective dose level as we pull together a dosing regime. These are CD3 bispecifics, so you want to have your priming and step-up doses. We've 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.

Great. Thanks. And if I could just sneak in one more? You guys set the stage pretty well with your comparative table there. But looking ahead to the go-forward decisions for both the mono and combination vudalimab approaches, how would you guys set the bar?

Yes. I guess maybe the mono first. I mean, Nancy, Dane, you guys want to take that? What's the bar for advanced comparables?

Yeah, sure. Great question. When we look at the patients that we've enrolled into the monotherapy cohort, 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 engaging 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. In those studies, namely the control arm for therapy or the very recently reported part two of CheckMate 650, you've seen a RECIST response rate for cabazitaxel in that 11% to 24% range, and a PSA50 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 vudalimab 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, has generally come out around eight months for a radiographic progression-free survival. And right now, based on some of the durability, seems like we're in pretty good shape.

Now, then for the combo cohort, I guess we've got different baselines there to look at.

Yeah. In the combination cohort with Docetaxel, you really have to think about what Docetaxel might be able to do in 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 a PSA50 response range of 40% to 50% and a fairly low RECIST response rate of somewhere around 10%. That said, the survival curves are a bit better for that line in that setting with Docetaxel monotherapy. But that's kind of what you have to think about when you're doing a combination study with Docetaxel at this point.

Perfect. Thanks so much. I appreciate it.

Thank you. One moment, please. Our next question comes from the line of Etzer Darout from BMO Capital Markets.

Great. Thanks for taking the question. I guess maybe on the safety profile of vudalimab, if there's anything you can or will incorporate into the study to maybe kind of mitigate this autoimmune hepatitis? Is this something that is just unique to this patient or are there other things sort of going on that you need to understand? And then, also on XmAb564, just wondered about the decision to sort of pause that, was that data-driven or whatever other contributing factors, if you could comment on that to pausing that study? Thank you.

Sure. I'll start with XmAb564. Then Nancy can address the question regarding the vudalimab safety profile. For XmAb564, our decision to concentrate on our T-cell engagers, including our resources, capital, and personnel, has been a significant factor. We are focusing on how the class of cytokines, especially IL-2 Treg driving cytokines, has developed. There is still a lot of important data expected to come in over the next year from other companies related to efficacy and the potential of this class. As our study has progressed and provided insights into our pharmacokinetics, pharmacodynamics, and safety, we believe it's the right time to reassess our resources and observe how the field develops. We are poised to ramp up efforts again, but right now, our focus is essential. For 2024, pipeline focus is crucial for Xencor. This decision was primarily driven by our strategy. Now, Nancy, would you like to comment on the vudalimab question?

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, and 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 to hepatitis. As far as the protocol and the investigators, we have emphasized to the investigators to be watchful for this and communicated with them. The protocol does include the NCCN guidelines for treatment, and it's also consistent with ASCO guidelines and other society guidelines like the gastric GI guidelines for monitoring and treatment. We do include screening at baseline for any diseases that might contribute to hepatitis, and we have frequent laboratory monitoring.

Great. Thank you for the color.

Sure.

Thanks, Etzer.

Thank you for the question. One moment, please. Our next question comes from Gregory Renza of RBC Capital Markets. The floor is yours.

Hi. Thank you so much for taking our question. This is Kurt for Greg. Just to confirm if this monotherapy data was from a particular molecular subtype since I think that was how the trial used to be characterized? And if I may, secondarily, from the data comparison table, I think the PSA90 looks competitive but PSA50 looks a little lower. Just curious if you have any hypothesis on why the data looks that way. Thank you.

So, I'll touch on the specifics of the trial and the population. Just to be careful, there are two studies ongoing now where we're studying 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 still enrolling patients, and with more follow-up, we hope to have a lot more clarity later in the year on that program. Also, in the first half of next year, we hope to bring it all together. So, 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?

Yeah, sure. That's a great question that we looked at quite extensively once we had this data cut and were able to review the data with our investigators during ASCO GU. What seems to be somewhat of an artifact of taking patients that are required to have measurable disease at baseline versus other studies that also include bone only. As you can see on that table, most of our peer studies outside maybe one with a similar mechanism of action are more of a mixed patient population. What we see in those studies is you get more PSA50s that don't necessarily correlate to a RECIST response, as some of those patients do not have measurable disease at baseline. In our cohort, to get clinical benefit, those patients will need either a RECIST response or a PSA90. So, I think there's two things there. One is PSA50 for patients that are this advanced in their disease course is relevant for survival outcomes, very debatable. But what is definitely needed is those RECIST responses and PSA90s.

Thank you.

Thank you. One moment, please. Our next question comes from the line of Kaveri Pohlman from BTIG. The floor is yours.

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 are you thinking about the dose that will be used going forward? My second question is also for the go/no-go decision. How many patients do you plan to enroll in monotherapy and combination cohorts for that? And is efficacy the only factor you're considering to make these decisions? Lastly, 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.

Hey. Thanks, Kaveri. 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?

Overall, we have observed that the safety profile appears to be similar to other checkpoint inhibitors. We haven't identified anything that indicates significant differences that would negatively impact the product. There is extensive data available regarding IPI single monotherapy checkpoint inhibitors and their combinations, and broadly, we align with that. Would you like to add anything?

In our lung cancer study and the monotherapy prostate study, we have switched to a Q3 week schedule using flat doses. This approach seems promising as it may provide advantages over the Q2 week weight-based dosing. Regarding IPI/NIVO, despite having over 240 patients, it remains challenging to identify subtle differences. We do not observe the significant colitis often seen with high doses of IPI therapy. Our drug is administered at much higher doses than the standard IPI regimen of 1 milligram per kilogram. This is probably the best comparison we can offer across various studies, but overall, the results are quite consistent with checkpoint inhibitors. As for the target number of patients for both the combination and monotherapy by the first half of next year, we are aiming for around 30 patients in each setting. Specifically, for the chemo study, which includes our main cohort without targetable mutations, we are focusing on the Docetaxel combination and aim for 20 patients in our monotherapy study as well. We hope to reach these numbers to facilitate decision-making.

I think it would be helpful, maybe, Nancy, you could just explain the difference between measurable disease and non-measurable disease at baseline, because I think that might be helpful for everyone.

Sure. Measurable disease basically means it has very basic 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 but could also have had bone disease on top of that. I can tell you that 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.

Got it. Yeah, that's what I wanted to know. Thank you. Thanks for the color.

Thank you. One moment, please. Our next question comes from the line of Brian Cheng from JPMorgan. The floor is yours.

Thank you, Bassil and everyone for taking my questions today. My first question is about the three confirmed responders. Building on the previous question, could you provide some background on these responders? How many treatment lines have they undergone, and what have their historical responses been to prior AR treatments? I noticed that some patients received radiation, so I'm curious about their responses. I have a follow-up as well. Thank you.

Yeah. I mean, Nancy, you could take that. You know all the details. I'd say they were really heavily pretreated in rough shape when we got them.

They had to have progressed through at least two prior therapies, and the background shows they had between three to seven prior therapies, including radiation. One patient had three prior therapies excluding radiation, another patient had three, the third had six, and the last one had two, none of which included radiation. All patients had received Docetaxel, one received Carboplatin, and two had prior radiotherapy. I can't make firm predictions about their previous responses, but perhaps in a future presentation, we could examine the details for each patient individually.

Yeah. But suffice to say, they'd seen a lot of prior therapy, Brian.

Okay. As you analyze this data, I believe the last time we reviewed the combination data was in 2022. How should we approach the low-hanging fruit aspect? What specific subset of mCRPC patients should investors focus on in relation to vudalimab? Is it those at high risk or those with specific genetic profiles? How do you perceive the low-hanging fruit regarding either the combination treatment or monotherapy? Thank you.

Yeah. 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 in 30 patients per cohort for monotherapy and for the combination. The way we're thinking about it now is we just had an update on part two of CheckMate 650 at ASCO GU, where IPI/NIVO was tried in every foreseeable combination relative to Cabazitaxel. The emergent signal that we have in a 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 these 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. So that has to be on our minds as we look through future development. The interesting point here is the toxicity profile of vudalimab is non-overlapping with PLUVICTO. So that's one thing. 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. This all has to be proven out in the clinic within larger studies. Step one for us is still defining what we think the clinical profile is of vudalimab monotherapy for these heavily treated metastatic 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 the development of this drug. We're excited about what we're seeing. Again, it's early days here, so we don't want to get over our skis. But we'll look for a confirmation of this signal as we move throughout the year.

Great. Thank you, guys.

Thank you for your question. One moment, please. Our next question comes from the line of Alec Stranahan from Bank of America. The floor is yours.

Thank you for taking my question. This is for Alec. I have a quick question. I believe this was mentioned earlier, but I wanted to clarify. What would be a good benchmark or comparison for the vudalimab monotherapy data discussed today? That's my first question. For my second question regarding quality-of-life data, when can we expect more information about that? Can you provide any insights into what you're currently observing in the clinic regarding quality-of-life and patient-reported outcomes? Thank you.

Yeah. We're not collecting, sorry, Dane, do you want to address both questions or...

I believe that question really depends on when we have a complete summary of a cohort discussed with our clinical investigators. We need to determine if the overall clinical experience for these patients suggests we should proceed. At this moment, we don’t have all the data we need. Ideally, we want to see around 30 patients in both the monotherapy cohort and the Docetaxel combination cohort before having that discussion with our clinical investigators. That's a significant question we're aiming to address. Regarding the first part of the question, we provided the data table and the slides for context. Each study we're examining is part of peer reviews and we find them exciting. We're particularly enthusiastic about Xaluritamig and its clinical response, but we recognize there are limitations regarding their size, scope, and the similarity of the patient populations involved. We want to avoid making comparisons between different novel agents for treating these prostate cancer patients at this stage. What we can state is that several of these programs, particularly Xaluritamig, appear to be exceeding expectations for late-line chemotherapy based on contemporary studies, such as the Cabazitaxel response rates and the CheckMate 650 study. As we move into earlier lines of therapy, we believe the toxicity profile becomes critical. If PLUVICTO is indeed making the tumor microenvironment more receptive to immuno-oncology therapy, we may have a treatment option that does not share overlapping toxicities, presenting an intriguing avenue to explore in the future.

All right. Thanks for the color.

Thank you for your question. One moment, please. Our next question comes from the line of Tara Bancroft from TD Cowen. The line is now yours.

Hi. Good afternoon. So, my question is more of a general question. Are there any other combos besides chemo that you're considering or really excited about that could increase the robustness of this data? In 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 17-04 study? Thanks.

So I guess on the first one, 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 has from some small studies recently published and they got a UCSF. So, I think those are the two top things on our mind now. But 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. As that one evolves in combo with Pembro, we're certainly keeping an eye on how to maybe use that with vudalimab if the stars align, right? So that's maybe the other big one that we're thinking of. The future might hold combinations with CD3 bispecifics with molecules like vudalimab. I think that's something people are looking at, or 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 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?

Yeah, absolutely. So maybe I can share also that since we last presented data, we amended the protocol, the combination protocol in prostate cancer to remove the carboplatin in all but the aggressive variant. We're really focused on the taxane, specifically Docetaxel, as first-line chemotherapy. So far, based on feedback from investigators, we seem to be seeing better tolerability with these new regimens than the prior one.

Operator, do we have any other questions?

No. That looks like that's clear.

Great. Well, thanks, everybody, for joining us today, and have a wonderful evening. We look forward to our next update.

Thank you for your participation in today's conference. This does conclude the program. You may now disconnect.