Thank you. Good afternoon, and thank you for joining us.

Before we begin, I would like to remind everyone that during this call, we will be making forward-looking statements. Because forward-looking statements relate to the future, they are subject to inherent uncertainties and risks that are difficult to predict, and many of which are outside of our control.

Important risks and uncertainties are set forth in our most recent public filings with the SEC at sec.gov. We undertake no obligation to update any forward-looking statements, whether as a result of new information, future developments, or otherwise.

Earlier this afternoon, we issued a press release that includes a summary of our first quarter 2026 financial results and highlights recent progress at CytomX. We encourage everyone to read today's press release and the associated materials, which have been filed with the SEC.

Additionally, the press release, recording of this call, and our SEC filings can be found under the Investors and News section of our website. With me on the call today is Dr.

Sean McCarthy, CytomX's Chief Executive Officer and Chairman. Sean will provide an update on our pipeline and company progress before I cover the financials for the quarter.

We will then conclude with a Q&A session. With that, I will now turn the call over to Sean.

Thanks, Chris, and good afternoon, everyone. We're very pleased to be here today to provide an update on our first quarter developments and guidance for what's continuing to be a transformational year for CytomX.

2026 is off to a very exciting start, driven by our excellent clinical progress with varsetamab in late-line colorectal cancer. Varsetamab is a first-in-class EpCAM-targeting antibody-drug conjugate, or ADC, that was uniquely designed and enabled by our proprietary Probody therapeutic masking platform.

Varsetamab is the only EpCAM-directed ADC in clinical development to our knowledge, affording us a strong lead and a powerful competitive advantage. EpCAM is one of the most abundant solid tumor surface antigens, and CytomX' breakthrough in unlocking EpCAM as an ADC target positions varsetamab as a company-building asset over the near and long term.

We see multiple layers of value creation potential for CytomX through the advancement of varsetamab. In colorectal cancer, which I'll now refer to as CRC, our goal is for varsetamab to become a core component of the standard of care, including in earlier-line therapy.

Metastatic CRC remains one of the largest areas of unmet need in oncology today, which really underscores the urgency we feel at CytomX to progress varsetamab towards the market as rapidly as possible. Commercially, in the late-line setting alone, this represents a multi-billion dollar market.

In addition to the very substantial opportunity in CRC, we also plan to capitalize on our leadership in EpCAM targeting by developing varsetamab in other cancers, and ultimately as a pan-tumor therapy. Varsetamab has the long-term potential to positively impact the lives of so many people with cancer, and we are focused on executing with urgency to rapidly progress this potential therapy to regulatory approval.

CytomX has made a very strong start in the clinic with varsetamab. In our most recent Phase 1 data update in March this year, we shared updated efficacy data in late-line metastatic CRC showing a confirmed overall response rate between 20% and 32% and approximately 7 months of median progression-free survival.

These data position varsetamab as a potentially transformative step forward in the treatment of metastatic CRC, where currently available therapies offer overall response rates only in the low single digits and just a few months of PFS. Varsetamab is working exactly as designed, and it's unlocking the true potential of EpCAM for the first time.

With varsetamab, CytomX is bringing the power of the ADC class to colorectal cancer. I want to really underscore here that we've achieved something very significant with our Probody platform technology.

In our view, and based on our preclinical data and efforts of others over many years, we believe we can say with confidence that a conventional, unmasked ADC targeting EpCAM would have no chance of achieving dose levels that deliver meaningful anticancer activity due to severe on-target toxicities. In contrast, with varsetamab, we have achieved remarkable anticancer activity in one of the hardest-to-treat cancer types.

We firmly believe we have done the hardest experiment first by focusing initially in CRC, and that the best is yet to come. In terms of key near-term objectives for varsetamab, we are currently in dose optimization with the goal of advancing into a registrational study in late-line CRC in the first half of 2027.

Today, we're very pleased to share that we have completed enrollment in the ongoing dose optimization cohorts with 40 total patients now enrolled across the 8.6 and 10 mg/kg doses, taking total enrollment across the Phase 1 study to 113 patients. We remain well on track for an update before the end of this year as we work towards prioritizing one of these two doses of this highly active drug candidate for our first pivotal study.

In evaluating the potential registrational study dose, we're focused on optimizing the risk-benefit of varsetamab, building on the significant learnings in the dose escalation, expansion, and optimization phases. Regarding varsetamab safety, we have been highly encouraged by the preliminary results we shared in March from dose optimization that showed that updated patient management strategies have the potential to substantially reduce the rate of high-grade diarrhea we saw earlier in Phase 1 development.

This is the principal adverse event of interest with varsetamab, and it's something we feel confident we can get an increasingly well-developed understanding of as we move forward through the optimization cohorts and beyond. Typically, patients respond very well to management, and our overall discontinuation rates are low, accounting for the impressive progression-free survival data we have shared to date.

In terms of our next clinical communication, we expect to provide an overall Phase 1 data update, including safety and efficacy from the monotherapy dose optimization, in the second half of this year. We expect these data, along with FDA interactions in 2026, to inform varsetamab monotherapy dose selection and the first registrational study design.

Our primary goal with varsetamab is initially to develop in the late line, where we see this drug candidate as highly differentiated and, frankly, as offering a highly impactful new option for CRC patients. Over time, our vision for varsetamab in CRC is to replace systemic irinotecan in the treatment paradigm, and potentially to displace chemotherapy entirely.

Accordingly, and in parallel to its development as a monotherapy in CRC, we are aggressively advancing varsetamab into combination studies to enable earlier-line utilization. Strategically, we see an enormous opportunity for varsetamab in early-line CRC.

To access this opportunity, we have initiated a combination with bevacizumab as a first step to moving varsetamab into earlier-line therapy. Anti-VEGF antibodies, including bevacizumab, are extensively utilized in early- and late-line CRC treatment, this will be a foundational combination.

Varsetamab doses assessed in combination with bevacizumab will include both every two weeks and every four weeks schedules to align dosing with the approved 5 mg/kg every two weeks schedule standardly used in the clinic today. We expect initial clinical data for this combination by the first half of 2027.

We're also accelerating plans to study varsetamab in combination with chemotherapy, and we plan to begin a Phase 1/2 chemotherapy combination study in the second half of 2026, evaluating varsetamab in combination with bevacizumab, 5-fluorouracil, and leucovorin, with the potential to advance into the first and second lines. In addition to our work in colorectal cancer, we are on track to begin Phase 1 expansion cohorts in additional EpCAM-expressing indications in the second half of 2026.

We look forward to providing an update on the initial non-CRC indications later this year with the goal of generating clinical data supporting varsetamab's ultimate pan-tumor potential. Turning now to CX-801, our masked interferon alfa-2b program, which is currently in Phase 1 development for advanced checkpoint-refractory melanoma.

Our vision here is for CX-801 to become a new centerpiece for combination cancer immunotherapy as we harness and redirect the power of this cytokine to reprogram and activate antitumor immunity. We initially see CX-801 as well positioned to address the high unmet need in PD-1-refractory melanoma, where response rates to approved standard of care remain in the single-digit percentages with limited treatment options available or in clinical development.

Interferon alfa-2b is a potent cytokine that has validated clinical activity in melanoma and other cancers, and our initial translational data from Phase 1 suggest that CX-801's mechanism of action is working as designed in the tumor microenvironment. Importantly, our data shared at SITC in 2025 are highly supportive of our strategy for combining with the checkpoint inhibitor KEYTRUDA.

Our ongoing CX-801 Phase 1 monotherapy dose escalation study has advanced to the fourth dose level, which exceeds the approved clinical dose of unmasked interferon alfa-2b. CX-801 has been well tolerated to date, suggesting that our masking strategy is broadening the therapeutic window as designed.

Combination dose escalation with KEYTRUDA is also progressing very well and is now actively enrolling in the third dose level. Overall, we view CX-801 as very well positioned to address a significant unmet need in advanced melanoma, and we look forward to sharing initial clinical data by the end of this year.

With that, I'll now transition back to Chris.

Thank you, Sean. Reinforcing Sean's earlier sentiment, we kicked off 2026 from a position of strength, not only with varsetamab's encouraging data, but with the financing completed in March, a strong balance sheet that enables us to continue to execute against the significant value creation potential of varsetamab and the Probody platform.

CytomX is in a strong financial position with projected cash runway to at least the second half of 2028 and the potential to achieve multiple milestones. Of note, our runway guidance does not include any supplemental milestones from existing collaborations or any new business development.

Importantly, we expect our current cash position will enable us to advance varsetamab into a registrational study in late-line CRC, also deliver safety and efficacy data for varsetamab in combination with bevacizumab, as well as varsetamab data in combination with chemotherapy, and deliver initial clinical data for varsetamab in indications beyond CRC. Based on these opportunities, which have the potential to yield significant long-term commercial potential, we expect our capital allocation to be highly focused on varsetamab over the near to medium term.

With that, I will now walk through our first quarter financial results. As of March 31st, 2026, we ended the quarter with $346.7 million in cash, cash equivalents, and investments versus $137.1 million in cash as of December 31st, 2025.

Looking at revenue and operating expenses for the quarter, total revenue was $10.3 million compared to $50.9 million in the first quarter of 2025. The decrease in revenue was primarily attributed to the completion of obligations in 2025 under collaborations with Bristol Myers Squibb and Amgen.

Operating expenses for the first quarter were $29.8 million compared to $28.3 million in the first quarter of 2025. R&D expenses were $19.2 million during the first quarter, representing an increase of $0.4 million versus the first quarter of 2025, primarily due to increased manufacturing activities for varsetamab, partially offset by $1.8 million in restructuring expense incurred in the first quarter of 2025.

G&A expenses increased by $1.1 million during the three months ended March 31st, 2026 to $10.6 million compared to $9.4 million for the corresponding period in 2025, which included $1.1 million of one-time restructuring expenses. As we move throughout the remainder of 2026, we will continue to be disciplined in our capital allocation and advancing the highest varsetamab priorities for patients and CytomX stakeholders.

With that, I'll turn the call back to Sean for closing remarks.

Thanks, Chris, and thanks everyone for joining us today. We're very proud of the remarkable progress we've made with varsetamab, and we're now in the privileged position of bringing the transformative potential of an EpCAM-directed antibody-drug conjugate to colorectal cancer patients.

We look forward to providing additional updates as the year progresses and as the development program for varsetamab broadens substantially. We also remain focused on the advancement of the clinical program for CX-801 with the initial goal of delivering a more effective treatment option for patients with advanced melanoma.

Before I conclude today's call, I want to sincerely thank and recognize the patients who join our studies, their families, our clinical investigators, and our dedicated CytomX team. With that, operator, let's go ahead and open up the call for Q&A.

thanks for taking the question. For varsetamab, can you just talk a little bit about the scope of the clinical update you'll have in the second half?

Will some or most of the dose optimization cohort patients have sufficient follow-up for PFS? Do you plan to break down responses by subgroups such as third-line versus fourth-line plus of therapy?

Then how are you thinking about initial disclosures of overall survival from this study? Thanks so much.

Thanks, Paul, for the questions. We are expecting that the update in the second half will be fairly substantial.

As we've mentioned today, we've now enrolled 113 patients across the dose escalation, expansion, and now optimization phases of the study. This is a very rich data set that is emerging for our first evaluation of varsetamab in CRC patients.

In terms of the update, it will be across the entire study. It will include data from the full 40-patient optimization phase.

We expect to have reasonable follow-up in terms of safety and efficacy for the optimization patients, including I would think an initial estimate of PFS. As you'll recall, last year, our guidance as we came through the second half of 2025 was that we wanted to communicate data this year when it was mature and meaningful, and that continues to be the case and continues to be our philosophy.

In terms of subgroups, yeah, we'll certainly communicate the demographics of the patient population that we're enrolling. We do expect it to look quite similar to the patient population that we enrolled in the escalation and expansion phases.

I want to emphasize that one of the really differentiating and distinguishing features of varsetamab as a drug for colorectal cancer is that we can treat every patient. We're not selecting patients.

We don't need to select patients. This really is a drug for all-comer late-line CRC, and we see this as potentially a huge competitive advantage as we move the drug towards the market.

In terms of the third component of your question and overall survival, yes, we absolutely anticipate having or providing, if you like, a first look at OS in this update in the second half of the year.

Great, thank you very much.

Great. Thanks so very much and really excited for more data looking in the back half.

I just had a one quick clarification question on the 1/2 chemo combo. Will that be triplets, will you have Avastin, or I guess quadruple with the two chemos, and will that include Avastin?

Do you need any of the Avastin combo data to start that chemo combo trial? I just want to make sure I understand that correctly.

Yeah. Hi, Ted.

Thanks for the questions. Taking the first question first, in terms of the nature of the combination, yeah, we absolutely will want to evaluate the varsetamab plus chemo plus bev combination.

We will want to look at that. Right now, we don't see the data from the ongoing varsetamab plus bev as gating necessarily to starting that work in the second half.

We do of course see that bev combination work, the varsetamab-bev combination is going to be really important to further down the road, considering from a registrational study perspective the design of that study if indeed we do at some future point decide to compare varsetamab plus bev against other comparator arms. We do plan to look at that triplet in the chemo combination later this year.

Yeah. Then, that's really helpful.

Then when it comes to the new EpCAM-positive tumors, I'm really excited to hear what your thinking is. Maybe you can share with us now kind of what goes into some of that prioritization, because there's a lot of different places you could go.

Thanks.

Yes, there are so many places we could go because EpCAM is such a broadly expressed cancer target on so many solid tumors. We do have a lot of opportunities to work through and prioritize.

It's not lost on us, of course, or really anybody else that there's quite a number of, if you like, adjacent GI tumors that could make a lot of sense to evaluate with varsetamab. There are also many others.

Something that we continue to work through and prioritize, and we will communicate more specificity on exactly what we're planning to do in the second half.

Great. I'm looking forward to it and more data.

Keep up the great work.

Thanks, Ted. Our next question will come from the line

Hey, guys. This is Joyce on for Anupam.

Thanks so much for taking our question. I think previously you had said you were targeting mid-year FDA interactions to start discussing the pivotal trial design.

To what extent is reaching alignment on the trial design ultimately gated on seeing your dose optimization update later this year? I assume you can start having those conversations with FDA now with your initial data in hand.

Just how should we think about the update later this year in terms of solidifying a registrational strategy? Thanks.

Thanks. Great question.

Really important question, and I'll start by saying that we're just really excited to have this dialogue with FDA as we progress through the year. We anticipate multiple interactions, and we do expect that the data from the optimization cohorts will be central to those conversations in relation to dose selection for the first pivotal study.

That's of course a large part of the reason we're doing these additional two N=20 cohorts at the 8.6 and 10 mg/kg doses is to generate data to satisfy Project Optimus and you have as highly productive a conversation with FDA as we can. Yes, that data will be important, and that's why we're guiding that really towards the end of the year or by the end of the year, the next comprehensive update that we plan to provide will not only include, of course, data across the 113-patient Phase 1 study, but will also include guidance as to where we're going next in terms of design of the first pivotal study, what the patient population is, what the comparator arm is, and of course, what the dose is.

Hey, thank you, team, for taking our questions. Congrats on the progress.

This is Nabil on for Roger. Maybe one for me first.

Just on the 8.6 versus 10 mg/kg, just a little bit curious if you could maybe give some color on the dose decision logic, because we saw the headline ORR 32% versus 20%. What is the framework that you guys would apply to finally locking on a dose?

Is it related to tolerability at this point, because we noticed in the exposure-response model, it looks like there's pretty similar efficacy, are you weighing depth and durability? Are you weighing safety more?

Thank you.

Thanks, Nabil. Obviously there's a lot in that question in terms of the work that we are doing in real time and will be continuing to do as we move through the year to lock in on the go-forward dose.

First thing I'll say is we think we've got two great choices here in terms of the 8.6 and 10 mg/kg doses, both of which, as you'll recall, we're currently evaluating on an adjusted ideal body weight basis in the context of the dose optimization cohort. We're going to learn a lot as the year goes by as to the performance of these two doses, of course, in terms of efficacy, also in terms of safety.

On efficacy specifically, as we've been discussing for quite some time now, at least our base case for our first registrational study, we do anticipate that overall survival will be our primary endpoint. That, of course, means that ORR is really an important metric here for how the drug is performing, and this drug is performing extraordinarily well, as you said, 20% ORR at 8.6, 32% at 10 mpk.

That is remarkable activity. We also have remarkable progression-free survival of 7 months as reported on March 16th, and we are very keen to see how that translates into OS as the data matures, with OS, of course, as I just mentioned, being our most likely primary in the go-forward pivotal study.

We'll see how these two doses deliver in terms of all of these different metrics, and we'll choose accordingly.

Glad to see that as well. Thank you.

You're welcome.

Hi, good afternoon, and thank you for the questions. For that second half data disclosure, can I just clarify that you guys plan to break out tolerability and efficacy for those 40 patients specifically in the optimization cohort?

If so, will we still get PFS and potentially even an early look at some OS data from those patients specifically? Then from a timing perspective, top line second half of this year, does that mean you'll likely follow it up with a presentation at a medical conference sometime in early 2027?

Then I've got one quick follow-up on the new formulation with bev.

Thanks, Olivia. Obviously, the 40-patient optimization cohorts is of high interest to us and others, and so we absolutely plan to report the full safety picture, which we gave an early look at in the March 16th disclosure.

We gave an early look at the first two months of experience, which was very encouraging. We plan to give a similar look for the full 40 patients by the end of the year, together with efficacy.

As I've already mentioned, PFS would certainly be a goal there to have PFS for those 40 patients. I think OS is going to be too early.

We're just, as we reported today, we've completed enrollment, but that's been relatively recent, I think OS is going to be immature. We do anticipate having OS from the escalation and expansion phases, which I think will be particularly telling, because remember that in those patients, those first escalation and expansion patients, we had not optimized our adverse event management plan, but we were still able to deliver 7 months of PFS, and we're optimistic that we'll have an encouraging OS number as we get to report that later in the year.

In terms of venue for data updates, we do think a medical meeting this year is on the cards. Certainly as we move into 2027, additional medical meetings, we're of course keeping our options open.

Very helpful. Then for the combination with bev, is there anything you guys can tell us at this point about the formulation work that you've done to get varsetamab administered as an every two and four-week dosing schedule instead of every three weeks?

Or is there any data that you'll be sharing there at some point?

There's no real formulation work that needs to be done. It's simply an adjustment of the schedule from Q3W to Q2W and then accordingly to Q4W.

As I just mentioned on the call, that's to match the established clinical use of bev in the FOLFOX/FOLFIRI setting on a two-week schedule. There's no additional formulation.

It's simply a question of adjusting the frequency of dosing to match the use of bevacizumab in the marketplace today.

Thanks, Sean. Appreciate it.

You're welcome.

Hey, guys, thanks for the question. Just kind of curious how you're seeing the emerging competitive profile here of varsetamab versus the other ADCs that are also in development, [present TCT?]

being one of them, and then I guess more importantly, do you think this is a winner-takes-all, zero-sum game here with the Topo-1 based ADCs or do you think different patients might get different ADCs depending on certain health status, etc.? Thanks.

Thanks, Matt. We certainly don't see this as winner-takes-all by any means, and I think that would be a very unusual scenario for an oncology drug in this class in an area of unmet need like this.

Our thinking is very different on that question. With regard to varsetamab, we have a first-in-class anti-EpCAM antibody-drug conjugate, and again, I really can't emphasize how important it is to realize that we've done something really, really I'll use the word special with our technology to unlock the potential of EpCAM for the first time with our Probody therapeutic platform.

Secondly, we really do believe that varsetamab has the potential to be the best-in-class ADC for colorectal cancer. This drug is highly active.

It's highly active in terms of its response rate. It's highly active in terms of its progression-free survival, and we'll see what it can deliver in terms of overall survival as we move forward.

This is a very active drug, and we believe does have the potential to be best-in-class. We're going all out with this drug to get it to the market as quickly as we can.

We think it's highly competitive, and we think there's a ton of value to build in our company with this drug, most importantly, an enormous amount of benefit to bring to these patients.

Thanks.

Hi, thank you for taking my question. This is Yangzi sitting in for Mitchell.

I was wondering, with the enrollment now complete in the 40-patient dose optimization cohort, can you give any update on whether Grade 3 or higher diarrhea in the optimized adjusted ideal body weight plus prophylaxis population is still tracking closer to that initial 10% rate that was seen in the first 20 patients, or whether it's moved closer to something like the historical 25% to 30% range at the 8.6 and 10 mg/kg as follow-up has occurred?

No new data today. That data will be coming.

Obviously, we're highly encouraged by the initial data we presented on March 16th from the first couple months of follow-up of the first 20 patients enrolled into the optimization cohorts with a rate of Grade 3 diarrhea of 10%. I think we commented at the time, and I think we've been very consistent about this over the last few months, that our objective is, of course, to manage the rate of Grade 3 to the best of our ability with this updated AE management strategy that includes upfront use of loperamide and budesonide.

It appears to be performing very well as of that first data update, and we're encouraged to see additional data now from the full 40 patients. That data will be shared later in the year.

Our goal overall is to manage the Grade 3s into the 10% to 20% range. That we think is really the target, and that's based on our own research.

It's based on a lot of conversations we've had and quite honestly, a lot of work that's been published and presented by others over the last six or so months. We feel we're very much on track, as I said in my prepared remarks, to get a strong handle on that particular aspect of the varsetamab program.

I see. Thanks.

Curious also, for an optimized regimen, how standardized is this prophylaxis practice? Do you see any implementation friction that could matter in a community oncology setting if, for example, varsetamab moves earlier in late-line CRC?

We really don't. The upfront work that we're doing right now with these optimization cohorts is absolutely intended to pin down a prophylaxis strategy that will be readily translated into the community setting as we move into our first pivotal study, and of course, as we bring the drug to the market.

It's a good question. It's an important question, and it's one that we've asked ourselves, and that is, again, just to restate, a big part of why we're doing this upfront optimization work right now.

Right now, we don't see any challenges with the translation, if you like, of this updated AE management plan into a larger number of sites, and ultimately, into the commercial marketplace.

Thank you so much, and looking forward to the next update.

You're welcome. Thank you.

Thank you, and again, I'd just like to thank everyone for joining us today. We're very excited about our progress here.

I hope that comes across, and we really look forward to providing additional updates as the year as the year progresses.