사이톰X(CTMX) 2026년 3분기 실적 발표 콘퍼런스콜: 바르세타-M 임상 2027년 상반기 목표

핵심 요약

• 사이톰엑스는 2026년 3분기 말 기준 3억 4,800만 달러의 현금, 현금성 자산 및 투자자산을 기록해, 2026년 6월 30일의 3억 3,000만 달러에서 증가했다. 분기 말 잔액에는 3,700만 달러가 포함되어 있으며, 이는 리제네론이 2개의 추가 협력 타깃을 선정한 데 따른 것이다.
• 3분기 매출은 170만 달러로, 600만 달러였던 전년 동기 대비 감소했으며, 이는 주로 2026년 2분기 아스텔라스와의 협력이 종료된 데 기인한다.
• 영업비용은 2,520만 달러로, 2,170만 달러에서 증가했으며 이는 인력 관련 비용 및 컨설팅 지출 증가를 반영한다.
• 경영진은 현재의 현금 보유액으로 2028년 하반기까지 운영 자금을 충당할 수 있을 것으로 예상하며, 여기에는 바르세타-M의 첫 잠재적 허가용 임상시험 진입 계획이 포함된다.
• 사이톰엑스는 2027년 1월에 바르세타-M 임상 1상에 대한 통합 업데이트를 발표할 예정이며, 여기에는 첫 전체생존기간 데이터와 용량 선정 정보, 잠재적 허가용 임상 전략이 포함된다.
• 회사는 전이성 대장암에서 바르세타-M의 첫 잠재적 허가용 임상시험을 2027년 상반기에 시작하는 것을 목표로 하고 있다. 경영진은 무작위 배정 연구에서 전체생존기간이 1차 평가변수가 될 것으로 예상한다.

주요 재무 데이터

사업 및 운영 성과

바르세타-M 단독요법

바르세타-M은 사이톰엑스의 프로바디(ProBody) 플랫폼을 기반으로 한 EpCAM 표적 Topo1 항체-약물 접합체(ADC)다. 회사는 이 약물을 전이성 대장암 치료제로 우선 개발 중이며, 현재 임상 개발 단계에 있는 유일한 EpCAM 표적 ADC라고 설명했다.

단독요법 임상 1상 시험에는 용량 증량, 확장 및 최적화 코호트에 걸쳐 100명 이상의 환자가 등록되었다. 참가자 대부분은 이전에 전이성 질환에 대해 최소 3차례의 치료를 받은 상태였다.

용량 최적화 시험은 위장관 이상반응을 관리하기 위해 보정 이상체중 기반 용량 설정과 선제적 예방 요법을 적용하여 3주 간격 8.6mg/kg 및 10mg/kg 투여를 평가하고 있다. 사이톰엑스는 2027년 1월 업데이트를 통해 통합된 유효성 및 안전성 결과, 첫 전체생존기간 분석, 용량 선정을 뒷받침하는 데이터를 발표할 계획이다.

대장암 병용요법 개발

바르세타-M과 베바시주맙 병용 임상 1상은 후기 대장암 환자를 대상으로 등록을 계속 진행 중이다. 초기 임상 데이터는 연구 진행 상황에 따라 2027년 상반기에 발표될 것으로 예상된다.

사이톰엑스는 또한 2026년 말까지 바르세타-M과 베바시주맙, 5-플루오로우라실, 류코보린 병용요법을 평가하는 새로운 임상 1/2상을 시작하기 위해 차질 없이 일정을 추진하고 있다. 임상 1상은 용량 탐색을 위해 말기 환자를 대상으로 시작될 예정이며, 용량 탐색이 성공하면 임상 2상에서 2차 대장암 환자를 대상으로 진행된다. 이 전략은 이리노테칸을 바르세타-M으로 대체하는 방식이다.

기타 고형암으로의 적응증 확장

회사는 비선별 위암 및 위식도접합부암뿐만 아니라 EpCAM 선별 췌장관선암과 담도암에 대한 임상 1상 코호트를 시작했다. 사이톰엑스는 후기 개발 옵션을 결정하기 전에 항종양 활성과 안전성을 평가하기 위해 우선 암종당 약 20명의 환자를 등록할 계획이다.

CX-801

면역관문억제제 불응성 흑색종 환자를 대상으로 마스킹 인터페론 알파-2b 후보물질 CX-801의 단독요법 및 키트루다 병용요법 임상 1상 등록이 계속 진행 중이다. 사이톰엑스는 2027년 상반기에 흑색종 초기 임상 데이터를 발표할 것으로 예상한다.

경영진 가이던스

경영진은 보유 현금으로 2028년 하반기까지 운영이 가능할 것으로 전망했다. 회사는 이러한 현금 여력이 바르세타-M의 잠재적 허가용 임상시험 진입, 초기 치료 차수 대장암 대상 병용요법 평가, 기타 EpCAM 발현 위장관 종양으로의 확장 등 핵심 개발 우선순위를 지원한다고 밝혔다.

사이톰엑스는 바르세타-M의 첫 잠재적 허가용 임상시험을 2027년 상반기에 시작하는 것을 목표로 하고 있다. 최종 환자군, 대조군 및 투여 용량은 규제기관의 피드백을 개발 계획에 반영하면서 계속 평가하고 있다.

위험 요인 및 주요 관전 포인트

• 위장관 독성: 3등급 설사는 적극적으로 관리 중인 주요 이상반응이다. 사이톰엑스는 앞서 용량 최적화 환자 초기 20명을 대상으로 2개월간 동등 기간 추적 관찰을 진행한 결과 발생률이 10%로 나타났으며, 이는 동일 기간 추적된 증량 및 확장 코호트 환자의 30% 이상에 비해 낮은 수준이었다고 밝혔다.
• 용량 최적화: 경영진의 목표는 3등급 설사 발생률을 20% 이하로 관리하는 것이다. 보고된 발생 기간 중앙값은 약 5주이며, 회사에 따르면 해당 독성은 누적되는 양상을 보이지 않았다.
• 병용요법 내약성: 사이톰엑스는 바르세타-M과 5-플루오로우라실을 병용 투여할 때 위장관 독성을 면밀히 관찰할 예정이다. 경영진은 무진행생존기간과 전체생존기간을 위해 용량 강도를 유지하는 것이 중요할 수 있다고 언급했다.
• 허가용 임상 설계: 회사는 3차 이상 환자군과 적절한 대조군, 최종 용량을 여전히 평가 중이다. 경영진은 베바시주맙 치료 경험이 있는 환경에서 론서프와 베바시주맙 병용요법이 보고한 약 9개월의 전체생존기간을 고려 중인 중요 벤치마크로 언급했다.
• 경쟁 개발 현황: 경영진은 Trop-2, M7088, CDH17 ADC 프로그램을 대장암 분야의 경쟁 접근법으로 지목하며, 바르세타-M 개발 가속화에 집중하겠다는 방침을 재확인했다.

애널리스트 질의응답(Q&A) 하이라이트

• 1월 업데이트 시점: 경영진은 2026년 말에서 일정을 조정한 덕분에 안전성과 유효성에 대한 추가 추적 관찰, 보다 성숙한 무진행생존기간 및 전체생존기간 데이터 확보, 규제 당국과의 협의가 가능해졌다고 밝혔다.
• 잠재적 중추 임상시험: 사이톰엑스는 첫 허가용 임상시험이 전체생존기간을 1차 평가변수로 하는 무작위 배정 연구가 될 것으로 예상한다. 치료 차수, 대조군 및 선정된 투여 용량에 대한 세부 사항은 1월 업데이트에서 공개될 예정이다.
• 초기 치료 차수 전략: 베바시주맙 및 화학요법 병용 연구의 임상 1상 부분은 말기 환자를 대상으로 시작될 가능성이 높다. 임상 2상 부분은 성공적인 용량 탐색을 거친 후 2차 치료 대장암 환자를 대상으로 진행될 예정이다.
• 안전성 차별화: 경영진은 바르세타-M이 다른 Topo1 ADC 대비 혈액학적 독성 발생률이 낮게 관찰되었다는 점을 강조하면서도, 위장관 독성이 여전히 모니터링과 완화가 필요한 주요 영역임을 인정했다.
• 보정 이상체중 기반 용량 설정: 최적화 코호트의 모든 환자는 보정 이상체중 알고리즘을 사용해 투여 용량을 산출했다. 회사는 허가용 요법을 결정하기 전에 시간 경과에 따른 절대 용량과 용량 강도를 분석할 계획이다.

실적 발표 콘퍼런스콜 전문

전체 실적 발표 컨퍼런스 콜 녹취록

경영진 발표

Operator

CytomX's Chief Financial Officer. Please go ahead.

Chris Ogden

Thank you. Good afternoon and thank you for joining us. Before we begin, I would like to remind everyone that during this call, we'll be making forward-looking statements. Because forward-looking statements relate to the future, they're 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. Except as required by law, 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 filed our quarterly report on Form 10-Q for 3Q '26 and issued a press release with a summary of our third quarter 2026 financial results and business highlights.

We encourage everyone to read today's filing and press release. 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'll then conclude with a Q&A session. With that, I'll turn the call over to Sean.

Sean McCarthy

Thanks, Chris, and good afternoon, everyone. We're very pleased to be here today to provide an update on our third quarter developments and what continues to be a highly productive year for CytomX as we advance our lead program, Varseta-M, towards its first potential registrational study in the first half of 2027. Varseta-M is an EpCAM-targeting Topo1 antibody-drug conjugate with strong potential in colorectal cancer and potentially other solid tumors. Importantly, to our knowledge, Varseta-M is first-in-class as the only EpCAM-directed ADC in clinical development. Varseta-M has been intentionally designed and uniquely enabled by our ProBody platform, creating a significant opportunity for differentiation and long-term value creation. Strategically, we are initially developing Varseta-M in metastatic colorectal cancer as the lead indication. Our sense of urgency for Varseta-M is driven by the significant unmet need in colorectal cancer, which is the second leading cause of cancer death in the United States and worldwide.

Varseta-M is on the leading edge of ADC innovation in CRC and has the potential to be 1 of the first monotherapy ADCs to market for the treatment of this very challenging cancer type. In terms of commercial potential, there are an estimated 35,000 addressable patients in the United States with third-line or later CRC. Given the anti-cancer activity we have reported previously across an unselected late-stage patient population and the limited clinical benefit of existing therapies for these patients, we see considerable opportunity for Varseta-M.

Based on Varseta-M's unique profile, we are actively advancing our development program across 3 strategic areas of priority. First, we aim to move our Varseta-M monotherapy into a registrational study in the first half of next year, enabling a potential first approval and meaningful market opportunity in metastatic CRC. Second, we continue our development of Varseta-M in combinations, including with Bevacizumab and with earlier line chemotherapy regimens with the goal of replacing current standard of care. And third, we have started to evaluate Varseta-M's pan-tumor potential across multiple EpCAM-expressing cancers, initially in additional gastrointestinal indications.

The monotherapy Varseta-M Phase 1 study has enrolled more than 100 patients across dose escalation, expansion, and optimization cohorts. As previously reported, patients enrolled in the Phase 1 study have been heavily pretreated, with most patients having received 3 or more prior treatments in the metastatic setting. In March, we reported encouraging progression-free survival at doses of 8.6 and 10 mg/kg that exceeded current standard of care. We also shared our increasing understanding of the safety profile of Varseta-M, particularly how to lower and manage rates of high-grade diarrhea. This initial experience with Varseta-M in very late-line patients will provide us with a highly relevant dataset to enable monotherapy dose selection and inform the potential first registrational study design.

Most recently, we have been highly focused on dose optimization, evaluating 2 doses, 8.6 and 10 mg/kg given every 3 weeks with adjusted ideal body weight dosing and upfront prophylaxis to manage gastrointestinal adverse events. We anticipate providing an integrated update in January across the Phase 1 study, including our potential registrational strategy and the data that underpin our plans. It's important to note here that we expect this next update to provide the first look at overall survival for Varseta-M, which we anticipate will be the primary endpoint in our initial registrational study. We look forward to providing this next update in the near term.

Now moving on to the Varseta-M combination development program. Our ongoing Phase 1 study evaluating Varseta-M in combination with Bevacizumab continues to enroll late-line CRC patients to assess dose and safety. We view this combination as a foundational first step in evaluating Varseta-M's potential in earlier line CRC. Subject to data from the ongoing Phase 1 study, we anticipate moving to earlier line CRC patients in the future evaluation of this combination, and we anticipate reporting initial clinical data from the Bevacizumab combination in the first half of 2027.

To also enable the use of Varseta-M in earlier lines of CRC therapy, we remain on track to initiate a study evaluating Varseta-M in combination with Bevacizumab, 5-fluorouracil, and Leucovorin by the end of the year. This study will be a new Phase 1/2 trial that would enroll second-line CRC patients once Phase 1 dose finding is successfully completed. We believe these Varseta-M combination studies have the potential to inform future development options and look forward to providing initial updates starting next year.

Now moving to the development of Varseta-M outside of CRC, our strategy is to develop and ultimately commercialize Varseta-M across multiple EpCAM-expressing solid tumors. And we have recently initiated Phase 1 cohorts in gastrointestinal indications with substantial unmet need and that we view as highly complementary to CRC from a commercial perspective. We have initiated cohorts in unselected gastric and gastroesophageal junction cancer as well as EpCAM-selected pancreatic ductal adenocarcinoma and EpCAM-selected biliary tract cancer. Each of these EpCAM-expressing tumor types currently have limited treatment options in later-line settings and may present expedited development pathways for Varseta-M upon clinical proof of concept. Our initial plan is to enroll approximately 20 patients per tumor type to evaluate Varseta-M's anti-tumor activity and safety before assessing later phase development options. Having focused Varseta-M exclusively in CRC for the first 2 years of development, we're very excited to now be evaluating Varseta-M's broader clinical potential.

Now turning to CX-801, our masked interferon alpha-2b program being evaluated in checkpoint refractory melanoma. We see CX-801 as an exciting and broad opportunity to reprogram the immune responsiveness of solid tumors. And we continue to enroll the ongoing Phase 1 study evaluating CX-801 as a monotherapy and in combination with Keytruda. Enrollment in the monotherapy cohort of our Phase 1 study continues, having exceeded dose levels of the approved dose of unmasked interferon alpha-2b. Initial biomarker data for CX-801 monotherapy presented previously have reinforced our mechanism of action hypothesis for CX-801 in combination with Keytruda. We continue to enroll in the combination cohort, and we look forward to sharing initial clinical data from the Phase 1 study in melanoma in the first half of 2027.

With those updates, let me now transition the call back to Chris.

Chris Ogden

Thank you, Sean. As Sean highlighted, we are making important progress across the Varseta-M program, including potentially moving towards later-stage development. As we progress the broadening Varseta-M development program, we have continued to maintain an efficient and flexible cost structure, enabling us to pursue the opportunities Sean described earlier. To that end, with our current balance sheet, we project cash runway into the second half of 2028. Importantly, our runway funds our key value creation priorities that Sean outlined, including advancing Varseta-M into its first potential registrational study, pursuing combination development to move Varseta-M into earlier lines of CRC, and then expanding into multiple other EpCAM-expressing gastrointestinal tumors.

With that, I'll now walk through our third quarter financial results. As of September 30, 2026, we ended the quarter with $348 million in cash, cash equivalents, and investments versus $330 million in cash as of June 30, 2026. The cash balance as of September 30, 2026 includes $37 million received from Regeneron following its selection of 2 additional targets under the recently expanded collaboration.

Looking at revenue and operating expenses for the quarter, total revenue was $1.7 million, compared to $6 million in the third quarter of 2025. The decrease in revenue was primarily attributed to the conclusion of the Astellas collaboration in the second quarter of 2026. Operating expenses for the third quarter were $25.2 million compared to $21.7 million in the third quarter of 2025. Research and development expenses were $16.5 million during the third quarter, representing an increase of $1.2 million versus the third quarter of 2025, primarily due to increased personnel-related costs and partially offset by lower Varseta-M spending due to the timing of manufacturing activities. General and administrative expenses increased by $2.3 million during the 3-month period ending September 30, 2026 to $8.7 million compared to $6.4 million for the corresponding period in 2025. Increased G&A expenses were primarily driven by personnel-related expenses and higher consulting spend.

As we move towards 2027, we will continue to be disciplined in capital allocation in order to progress the most compelling Varseta-M development priorities, and realize the broader value creation potential for CytomX stakeholders. With that, operator, let's go ahead and open up the call for Q&A.

Operator

[Operator Instructions]

Our first question comes from the line of Paul Jeng with Guggenheim.

질의응답

Paul Jeng

So I guess my first question is, can you expand a little bit about the Bev chemo combo study that's getting underway this quarter? Anything about the target enrollment number, and will this exclusively enroll second-line patients from the outset? And then, on the patients themselves, are you focusing more on patients coming off a FOLFOX-based frontline regimen, or do you otherwise plan to stratify by any key baseline characteristics? And then I have a follow-up.

Sean McCarthy

Great, thanks for the questions there, and we're really excited about the progress overall with the program and particularly moving further into the second line downstream with Varseta-M into the combination setting. And as we pointed out, the gaining of experience with Varseta-M in combination initially with Bev, which is ongoing, and soon to start with Bev plus chemotherapy, is a really important component of the program.

We do anticipate initially in the first part, the Phase 1 part of the study, that we'll enroll most likely late-stage patients as we dose range and gain initial experience of the combination strategy. And then as we open up further down the road, the Phase 2 part of the study, that would enroll second-line patients. And that's really all the detail that we're ready to give at this moment in time.

Paul Jeng

So then my second question is just would be great to get your current perspective on the broader landscape of ADCs in colorectal. Now there's a few competitors in Phase 3 as well as some recent data from emerging targets at ESMO. So how are you currently thinking about the positioning of Varseta-M given many of these are all using Topo1 payloads? Thank you.

Sean McCarthy

Yes, it's actually really exciting to see the field evolving in the way it is. I think we can say now quite clearly that antibody-drug conjugates are coming to colorectal cancer patients. It's been a long time coming, and this is just a really exciting development for the field overall, and of course, for the patients who are waiting and in desperate need for these innovative therapies. I want to really emphasize, in addition, of course, that our drug, Varseta-M, is the only EpCAM-targeting ADC. We are first-in-class on this target. We think that's a direct reflection of our proprietary masking technology. We've really been able to do something that no one else has been able to do.

We think that puts us in a strong position from a differentiation standpoint over time. And with regard to the other programs, yes, there are several to watch, and we're keeping a very close eye on them: the Trop-2 ADC, the Merck Serono program, M7088, and then more recently, I think as you're alluding to, including at ESMO, a number of CDH17 ADCs that have shown some encouraging, we think preliminary, data. We believe we've got to keep up a very competitive asset here, and it really underscores and fuels our urgency to move Varseta-M forward as rapidly as we can.

Operator

Our next question comes from the line of Etzer Darout with Barclays.

Etzer Darout

Just curious about the OS update in January for the first 73 or so patients. If you could maybe comment on when you think about third-line versus line setting versus pursuing a faster fourth-line setting. Is there a threshold relative to the roughly 9-month OS benchmark in Bev-experienced patients receiving Lonsurf plus Bev that you're looking at to decide whether you're going to go after maybe a third-line versus a fourth-line indication, knowing that the fourth line would probably get through the market faster? How are you thinking about that, and then I have a follow-up?

Sean McCarthy

Thanks, that's a great question, and you quite rightly point out the 9-month there or thereabouts OS that has been reported for Bev-Lonsurf in the post-Bev setting per the SUNLIGHT trial. That is an important number we are looking at relative to other components of standard of care in the third line, third line plus. And we continue to evaluate these options as we look towards potentially initiating this first registrational study in the first half of next year. We're continuing to look at these 2 options in terms of how we increasingly think about third line plus as the place to go.

And really the key questions for us are, what will be in this first pivotal study, what will the patient population be, what's the appropriate comparator in that patient population? Because I want to remind you that in the third line plus setting, although Bev-Lonsurf is, of course, thought of as the dominant therapy in the third line, treatment of third line patients and later is actually quite fragmented. And we see, as we really lock in on this study design, we think there's a number of ways to go to capture a significant portion of the third line plus market with a number of different designs. So more to come on that, and your question also does allow me to restate what I said in my prepared remarks, which is that we do anticipate that in this first registrational study, the OS will be our primary endpoint in a randomized study.

Etzer Darout

Great, thank you for that. And then for the January update now, is that primarily a planned conference timing and data maturation? Just wondered if you could comment on that in terms of now the data being in January of next year.

Sean McCarthy

We haven't specified the forum at this time. That will come in due course.

Operator

Our next question comes from the line of Edward Tenthoff with Piper Sandler.

Edward Tenthoff

I wanted to ask, with respect to the Avastin chemo arm study that you're going to start, in which it looks like you're replacing oxaliplatin, what safety endpoints are you going to be evaluating there to see whether or not the combination with Varseta-M is better tolerated? And maybe you can remind me how large that study would be. Thank you very much.

Sean McCarthy

Hi, Ted. Thanks for the questions. So the strategy in the Bev chemo combo will be to replace irinotecan with the ADC, so of course the Topo1 ADC really having been designed with that as 1 of the goals in mind. That's a very important part of the strategy. In terms of the safety profile, of course, this work is all about initially evaluating the combinability of Varseta-M with these other agents. And 1 of the things that we think could be very attractive about the Varseta-M safety profile that we've learned a lot about so far is the quite remarkably low rate of hematologic toxicity we see with Varseta-M relative to other Topo1 ADCs in development in CRC and elsewhere. So we think that certainly is an advantage.

I'd say the area that we'll be paying closest attention to would be the GI toxicity. We know that we have a certain rate of Grade 3 diarrhea with Varseta-M, something that we're continuing to learn a lot about and getting an increasing handle on, but that is something that we'll be watching very carefully in combination, particularly with 5-FU. But I would also say that, of course, irinotecan, since we're switching out irinotecan for Varseta-M, irinotecan itself has been known since the early days of its development to have its own rate of Grade 3 diarrhea. So we're switching Varseta-M for irinotecan, which I think could work in our favor. But we really need to do the work to evaluate the combinability.

Edward Tenthoff

Yes, makes sense. And would you be implementing the ideal body weight dosing and diarrhea mitigation in those studies, just as you have with monotherapy of Varseta-M?

Sean McCarthy

I think that's most likely, yes. Since we're still in the late stages, but we are coming to the later stages and I think soon a conclusion from our dose optimization work that we've been doing across the 8.6 and 10 mg/kg AIBW schedules, Q3 week schedules. So until we really pin that down, hard to say for sure, but I think it's not unlikely that we would be using AIBW moving forward in those additional combination studies.

Edward Tenthoff

Yes, makes sense. Thanks. Keep up the important work.

Sean McCarthy

Thanks, I appreciate the support.

Operator

Our next question comes from the line of Anupam Rama with J.P. Morgan.

Anupam Rama

This is Brooke on for Anupam. What drove the shift of the monotherapy update from year-end '26 to January? Is it more patient follow-up or waiting on FDA feedback? Thank you.

Sean McCarthy

Yes, as dose optimization has continued, we've really wanted to allow time for sufficient follow-up to assess safety and efficacy and also allow for the full engagement and feedback from regulatory authorities. We are looking forward to the update in January.

Operator

Our next question comes from the line of Roger Song with Jefferies.

Nabeel Nissar

This is Nabeel on for Roger. A couple from us. I guess regarding GI durability, it's encouraging to see the 10% Grade 3 in the 2 months as we get longer follow-up. I was just curious how you're thinking on time of onset, duration, and recurrence. And then as we go into second line, you mentioned earlier with 5-fluorouracil, we know that that may add some toxicity. We know that, as you mentioned, irinotecan is already used in second line. But what's the target for the GI toxicity that we're looking for?

Sean McCarthy

Yes, thanks, Nabeel. Great questions. And as I mentioned earlier, we're continuing to learn a lot about the safety profile of Varseta-M. And we did, as you also rightly point out, in March this year, report our initial experience in dose optimization, showing that after 2 months of matched follow-up with the patients in dose optimization cohorts, the first 20 patients in dose optimization cohorts across the 2 doses of 8.6 and 10 mg/kg, a rate of Grade 3 diarrhea of 10% relative to more than 30% in the time-matched patients from escalation and expansion. So an encouraging start.

I think we've been pretty consistent in talking about our goal for Grade 3 diarrhea based on work that we've done talking to oncologists and other market research that we've done, that we would like to manage the rate of Grade 3 diarrhea to 20% or below. We think that that is a more than acceptable rate in this disease. Obviously, we want to do the best we can in terms of leveraging the prophylaxis strategy, which in the March update was certainly showing a very good start.

Just a little bit more detail. Let me go into a bit more detail, since you mentioned time to onset, we've reported previously that time to onset for Grade 3 diarrhea with Varseta-M at these doses is about 5 weeks. And we've reported that it does not appear to be cumulative. We've also spent a lot of time over the last few months looking not just at the grade, but also digging deeper into the patient experience in terms of what is the amount of time that a patient spends in Grade 3 and what is the burden overall. And that's something that we'll have more to say about over time.

And the reason I point that out is that, of course, the goal of managing really this 1 significant AE that we have to think about with Varseta-M. The safety profile of Varseta-M overall we think is highly attractive, but our goal in managing the high-grade diarrhea is, of course, to maximize dose intensity. And we do anticipate that dose intensity will be an important determinant of efficacy, particularly in regards to PFS and OS over time. So ongoing work, and we continue to learn more all the time, and we'll look forward to providing the update in January. Thanks for the questions.

Nabeel Nissar

Yes, thank you, Sean. If I could ask a follow-up.

Sean McCarthy

Yes, go ahead, Nabeel, please.

Nabeel Nissar

So kind of taking a step back, we see the ESMO updates, encouraging to see more progress being done here. Curious if we take a step back and look at just the target itself, EpCAM, compared to targeting CEACAM5, both are glycoproteins. Can you comment on the rate of shedding compared to CEACAM5 for EpCAM? We know that CEACAM5 is more readily shed into the bloodstream. And do you think that in that regard, EpCAM has a more favorable target profile?

Sean McCarthy

Well, we do see EpCAM, I would say, compared to CEACAM5 being somewhat more highly and broadly expressed, although CEACAM5 is an abundant and broadly expressed target, which the data that I've seen is not so far from patients that have been selected for target expression, but we do continue to like EpCAM quite a bit as a target. In terms of shedding, I don't really have anything to say there in terms of comparison across the targets. And it's not, to be honest, something that we've spent a lot of time thinking about, but maybe we'll come back to you on that.

Operator

Our next question comes from the line of Olivia Brayer with Cantor Fitzgerald.

Olivia Brayer

I wanted to follow up on the January timeline or timing. Can you disclose what follow-up threshold you guys are looking to achieve, especially as you think about safety follow-up, but also thinking through survival and is this more about accruing events over time? I guess I'm trying to understand whether it's more about the dose expansion population or the 40-patient dose optimization cohort.

Sean McCarthy

Yes, hi, Olivia. So we've, I think, again, been pretty consistent here for a while now in terms of our goals and strategy for data disclosures. If we go back, I guess, a year or a year and a half, when we were approaching the data coming out from escalation and expansion, we communicated that we would share those updates, which we did in March this year, when we had an initial sense of progression-free survival on a dose-by-dose basis. With regard to the optimization data, similar guidance that we want to be able to share PFS from the optimization cohorts in the context of the first look at OS from escalation and expansion. So the January update, as I mentioned earlier on, is simply to allow sufficient time to give as robust an update as we think is appropriate.

Olivia Brayer

Helpful. And then, Sean, on the optimization cohort, how are you guys thinking about breaking out efficacy between patients who received an AIBW-adjusted dose and those who didn't? And I'm not sure if you can share this number, but any sense of what proportion of those 40 patients actually required a meaningful dose adjustment?

Sean McCarthy

Well, every patient's dose would have been calculated using the AIBW algorithm. I think it's a good question, but I would reframe it a little bit in terms of ultimately what's the dose, well, of course, what's the absolute dose that a patient receives and what's the dose intensity achieved over time? And that's the type of data that we're going to be analyzing and that we will be sharing in due course.

Olivia Brayer

Okay, understood. Looking forward to it. Thank you very much.

Sean McCarthy

You're welcome.

Operator

Our next question comes from the line of Kalpit Patel with Wolfe Research.

Unknown Speaker

This is Nikki on for Kalpit. I wanted to ask if, as you gain additional experience with the optimized dosing regimen, would you be able to give us any granularity on what that selected dose might be for the Phase 3 or what you're leaning towards? Thank you so much.

Sean McCarthy

Yes, thanks for the question. Can't provide any additional color at this moment in time, but that will be an important component of the update in January.

Operator

Thank you. I'm not showing any further questions in the queue. I would now like to turn it back over to Dr. Sean McCarthy, Chairman and CEO, for closing remarks.

Sean McCarthy

Thank you, and thanks, everyone, for listening in today. We continue to be highly encouraged by the progress we're making here at CytomX with Varseta-M, with CX-801, and more broadly with our ProBody therapeutic platform. We're excited about the breadth of opportunities in front of us as we drive toward the end of the year and rapidly, as it seems, into 2027. So thank you all for your time today.

Operator

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

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