Mersana Therapeutics, Inc. (0M40.F) Earnings Call Transcript & Summary

Good morning, and welcome to the Mersana Therapeutics Conference Call to Review Interim XMT-1536 Phase I Dose Expansion Data in Ovarian Cancer. [Operator Instructions] I would now like to turn the call over to Sarah Carmody, Executive Director, Investor Relations and Corporate Communications. Please proceed.

Good morning, and welcome to our call. Earlier this morning, we issued a press release providing updated interim data on the ovarian cancer cohort of the expansion portion of our Phase I study of XMT-1536. This release as well as the slides we will present today are available on the Investors & Media section of our website at www.mersana.com. A replay of today's call will also be made available. After our prepared remarks, we will open the call for Q&A. Before we begin, I'd like to mention that our call will contain forward-looking statements within the meaning of federal securities laws. These are not statements of historical facts and are based on management's beliefs and assumptions and on the information currently available. They are subject to risks and uncertainties that could cause the actual results and the implementation of the company's plans to vary materially, including the risk that our early encouraging preclinical results for XMT-1536 and XMT-1592 are not necessarily predictive of the results of our ongoing or future discovery programs or clinical studies, that the development and identification of the company's product candidates and new platforms will take longer and/or cost more than planned and that our clinical trials will not be completed on schedule, if at all. These risks are discussed in the company's SEC filings, including, without limitation, the company's annual report on Form 10-K filed on February 28, 2020, the company's Form 10-Q filed on May 8, 2020, and subsequent filings. In addition, while we expect the COVID-19 pandemic might adversely affect the company's preclinical and clinical development efforts, business observations and financial results, the extent of impact on the company's operations and the value of the market for our company's common stock will depend on future developments that are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration of the pandemic, travel restrictions, quarantines, physical distancing and business closure requirements in the U.S. and in other countries and the effectiveness of actions taken globally to contain and treat the disease. Except as required by law, the company assumes no obligation to update these forward-looking statements publicly, even if new information becomes available in the future. With that, I'll turn the call over to Anna Protopapas, Mersana's President and Chief Executive Officer.

Thank you, Sarah. Good morning, everyone, and thank you for joining us. Today, we are pleased to provide an incremental data update on the ovarian cancer cohort of our expansion portion of the XMT-1536 Phase I study, for which data was released as an e-poster this morning as part of the virtual ESMO meeting. Remember that we presented an initial data from the expansion portion of the study at ASCO in May of this year. Today's update includes data from 47 ovarian cancer patients, 29 of which were evaluable for RECIST response as of the cutoff date of August 18. This compares to the 27 ovarian cancer patients we disclosed at ASCO, of which 20 patients were RECIST response evaluable. We're very pleased to be joined by Dr. Erika Hamilton, Director of the Breast Cancer and Gynecological Cancer Research Program from the Sarah Cannon Research Institute at Tennessee Oncology, an expert and leader in her field. On today's call, Dr. Hamilton will walk us through this data, and then I will discuss our next steps for this important program. Before I turn the call over to Dr. Hamilton, I would like to remind you of the characteristics of XMT-1536 and its target, NaPi2b. XMT-1536 leverages Mersana's proprietary and highly differentiated Dolaflexin platform. Dolaflexin ADCs are designed to have 2 unique features aimed at improving both efficacy and tolerability. First, this ADC has approximately 10 payload molecules per antibody with excellent drug-like properties, including a long half-life, linear PK and very low free payload in circulation. Secondly, XMT-1536 utilizes our DolaLock payload, a proprietary oral study payloads with unique pharmacology that allows for controlled bystander killing. Additionally, the highly potent metabolite of the released payload is not a PGP substrate, thereby avoiding a major mechanism of resistance in cancer. These features are designed with objective of delivering improved efficacy and tolerability. And the data disclosed at ASCO and in today's update support this differentiation. XMT-1536 targets NaPi2b, a sodium-dependent phosphate transporter, broadly expressed in ovarian cancer and lung adenocarcinoma, but with limited expression in healthy tissue. This makes it a great target for an ADC. In preclinical studies, highlights of which are shown in this graph, we have demonstrated a strong relationship between outcome and H-score, a measure of biomarker expression. We have developed a proprietary robust assay to measure H-score in clinical trials and are in the process of validating with a commercially available companion diagnostic with anticipation of potential patient selection strategies in the upcoming registration-enabling study. We are continuing to see an emerging trend between NaPi2b expression and patient outcomes in the Phase I study. But as we have always said, the total expansion cohort data will be needed to make a definitive decision on patient selection. Turning to Slide 5. I'd like to briefly review the interim results from the ongoing dose expansion portion of Phase I study of XMT-1536 which we presented at ASCO in May. XMT-1536 showed a favorable safety profile and was generally well tolerated without the toxicities observed with other ADC platforms, such as severe neutropenia, peripheral neuropathy or ocular toxicity, consistent with previously presented dose escalation data. XMT-1536 showed a favorable activity in late-stage ovarian cancer patients. In the 20 evaluable patients with platinum-resistant ovarian cancer, we observed 2 complete responses and 5 partial responses. Complete responses are very rare in this late-stage patient population. The objective response rate was 35% and the disease control rate was 80%. Moreover, both patients with confirmed complete responses had prior treatment with the bevacizumab and PARP inhibitors. As a reminder, a previous NaPi2b-targeted ADC was studied before the introduction of bevacizumab and PARP into the treatment paradigm. Patients today are different. They have a higher unmet medical need and have failed more therapies when they become platinum-resistant. I will let Dr. Hamilton get into the details of today's disclosure. But overall, we're very excited that XMT-1536 continues to show a favorable safety tolerability profile and a very consistent level of activity in ovarian cancer patients with limited treatment options and poor prognosis, which I will review in the next slide. As a reminder, unmet medical need is significant in ovarian cancer with platinum therapy remaining the backbone of treatment in earlier stages of the disease. Recently, bevacizumab and PARP inhibitors have been introduced and are being increasingly used in earlier lines of therapy. Unfortunately, patients inevitably become resistant to platinum therapy and having previously received bevacizumab or PARP, at that point, their options are limited to single-agent chemotherapy, such as pegylated doxorubicin and topotecan. In patients with 1-3 prior regimens, these agents have limited efficacy with response rates in the 4% to 12% and PFS of 3 to 4 months and a median overall survival of less than a year. This is the population we're evaluating in this expansion study and for which we have already exceeded the standard of care response rate in both the dose escalation and expansion portions of the study. With that, I will turn the call over to Dr. Hamilton to review this updated interim data.

Thank you, Anna. Good morning, everyone. I am very pleased to be able to join you today to provide an interim update on the ovarian cancer cohort of the expansion portion of the XMT-1536 Phase I study. These data were also released earlier this morning as an e-poster at the European Society of Medical Oncology Virtual Congress. Before I begin, I'd like to thank my coauthors and the investigators named on this slide for their work on advancing this promising investigational therapy for patients with ovarian cancer, a population with continued significant unmet medical need. I'll start with a brief reminder of the expansion study design. While 2 cohorts are being enrolled into this expansion study, namely ovarian cancer and non-small cell lung cancer adenocarcinoma, we will focus today on the ovarian cancer cohort. The ovarian cancer cohort includes patients with high-grade platinum-resistant serous ovarian cancer with 1 to 3 prior lines of therapy, or, in some cases, 4 prior lines of therapy regardless of platinum status. Patients with 4 prior lines of therapy may not have had platinum as a recent prior line due to toxicity or intolerability and hence might not fit exactly into the definition of platinum resistant, but are very difficult to treat and have a similar prognosis to patients with platinum-resistant ovarian cancer by the traditional definition. Doses of 36 milligrams per meter squared and 43 milligrams per meter squared administered intravenously every 4 weeks are presented here today. Patients began enrolling at 36 milligrams per meter squared in August of 2019 and then the study was amended to enroll patients at the 43 milligrams per meter squared dose in December of 2019. All patients enrolled in the study since this amendment have been dosed at 43 milligrams per meter squared, the maximum tolerated dose determined in the dose escalation portion of the study. Patients are not selected for NaPi2b expression. However, archived tissue and fresh tissue biopsies when medically feasible are collected for retrospective assessment of NaPi2b expression. This slide outlines the patient demographics and disease characteristics as of the data cut-off of August 18, 2020. 47 patients with ovarian cancer were included in the analysis with a median age of 69 years. The majority were ECOG 1 status, ambulatory but with physical limitations from their disease. The majority of patients with ovarian cancer had 1 to 3 prior lines of therapy and were platinum resistant or refractory to their most recent line of platinum-containing chemotherapy. The majority of patients had received prior bevacizumab and/or a PARP inhibitor. This is a population with a very significant unmet need, having failed all available therapy and with unfortunately an expected median overall survival of less than 1 year. 13% of patients harbor mutations in BRCA1 or 2, consistent with the published literature. As I mentioned, NaPi2b expression is being evaluated by IHC in the archived and, where available, in fresh tumor tissue. And correlation between biomarker expression and clinical response is being explored as part of a companion diagnostic development. These data have been bifurcated between lower and higher NaPi2b expression based on the lowest NaPi2b expression level at which a response was observed in dose escalation. This is consistent with the previous disclosure of expansion data at ASCO. Expression levels are not yet available for all patients, but note that the majority of patients in the study are categorized as higher NaPi2b. We will define the threshold once we have completed the data set. Turning to safety. The safety profile is consistent with data previously presented at ASCO. XMT-1536 was generally well tolerated without the severe toxicities observed with other antibody drug conjugate platforms, such as neutropenia, peripheral neuropathy or ocular toxicity. The most frequently reported treatment-related adverse event included generally Grade 1 and 2 fatigue, nausea, decreased appetite, vomiting and transient AST elevation, which recovers by the next dose. No changes in bilirubin or Hy's law cases have been observed, and the transient AST elevations are easily monitorable with standard lab tests peaking on day 8 and recovering by the next dose. 23% of patients experienced a dose reduction, delay and/or discontinuation due to a treatment-related adverse event. As you will see in the coming slides, despite dose reductions, some of the responders achieved or deepened their response while on a reduced dose of 30 or even 20 milligrams per meter square. As an oncologist being able to dose reduce and retain clinical activity is an important feature of XMT-1536 for patients living with metastatic cancer. A total of 17 SAEs have been reported in 11 patients with ovarian cancer, 2 were deemed to be treatment related, including grade 2 pneumonitis, previously reported at ASCO and grade 3 vomiting. With the exception of the 2 patients with abdominal pain and the patient with grade 3 vomiting, these SAEs were previously disclosed at ASCO. We have also now treated well over 100 patients in the Phase I study and continue to be very encouraged by the overall safety profile of XMT-1536. Turning now from safety to efficacy data. These data continue to show that XMT-1536 is an active drug in ovarian cancer. Of the 47 patients with ovarian cancer, 29 were evaluable for RECIST response with at least 1 scan. Given the accelerating speed of recruitment, we have 15 patients that are not evaluable because they did not yet have RECIST assessment at the time of the data cut. In the 29 evaluable patients with ovarian cancer, we observed 2 complete responses, as was reported at ASCO, and 8 partial responses. This is an increase from the 5 partial responses observed at ASCO. The objective response rate is 34% and the disease control rate is 79%, consistent with the data reported at ASCO. Importantly, complete responses are very uncommon in this disease setting. As a reminder, both patients with confirmed complete responses had prior treatment with bevacizumab and PARP inhibitors. Responses have been observed in platinum-resistant and in platinum-refractory ovarian cancer, and the majority of responders had received prior treatment with either bevacizumab, PARP or both. Response was observed within 2 cycles of treatment in 70% of the patients and within 4 cycles of treatment in 100% of the patients. These data continue to demonstrate promising activity and the potential of XMT-1536 to provide a meaningful clinical benefit for patients with platinum-resistant ovarian cancer, particularly in the most difficult-to-treat patients with few other options. We bifurcated the data into higher and lower NaPi2b expression, as we had done at the previous 2 disclosures, for consistency purposes. We will define the patient selection strategy once we have completed the data set. Although the overall response rate is robust even in an unselected population, as you will see in subsequent slides, a patient selection strategy has the potential to improve patient outcomes not only in terms of the likelihood of response but also in terms of the depth, time on study and quality of response. The waterfall plot shows the changes in tumor dimensions of target lesions for the patients as characterized by NaPi2b expression and those where expression is not yet determined. The emerging profile of XMT-1536 continues to show important activity with deep responses. In addition, the majority of the stable disease patients did achieve tumor shrinkage. On the spider plot, we observed multiple patients who have shown deepening response over time, including several patients with stable disease who experienced tumor shrinkage in their target lesions. The swimmers plot is broken out by higher, lower and not yet determined NaPi2b expression. The data for the higher NaPi2b expressing population is not mature as 50% of patients remain on study and several have not yet received RECIST assessment. Importantly, 1 of the 2 complete response observed in 2 patients with platinum-resistant ovarian cancer disclosed at ASCO, 1 patient remains ongoing on study at 42 weeks. Interestingly, the other CR patient, who came off study around week 19 for tolerability and logistics related to moving out of state due to COVID-19, was still in CR when rescanned at week 28 without any additional intervening therapy. 1 patient had come off study after 1 cycle and had an unconfirmed partial response at the time of the ASCO data cut, remained off study for 3.5 months and progressed before reinitiating XMT-1536. She was not yet evaluable for response at the time of this data cut. The Kaplan-Meier duration of response curve on Slide 16 shows that these data are not yet mature. The median has not yet been reached and is based on a small number of patients. While early, these data demonstrate the potential role of the NaPi2b biomarker in identifying patients that can most benefit from XMT-1536. Before I conclude, I'd like to provide 1 patient case study, which happens to be a patient of mine. This is a 61-year-old woman with platinum-resistant, high-grade serous ovarian cancer, previously treated with chemotherapy, bevacizumab and maintenance therapy with a PARP inhibitor. She was initially treated with XMT-1536 at 43 milligrams per meter squared, and toxicities were managed with dose reductions, and she continues on study at a dose of 20 milligram per meter square. Despite dose reductions, we observed deepening responses over time. A tumor reduction of 29% was observed at cycle 2 with a confirmed partial response with a tumor reduction of 50% observed at cycle 4. The patient remains on study at 31 weeks. The observation of responses that appear to deepen over time is an encouraging sign. In conclusion, XMT-1536 continues to show a favorable safety profile with no severe neutropenia, peripheral neuropathy or ocular toxicity. Encouraging antitumor activity continues to be observed in patients with ovarian cancer with an overall response rate of 34% and a disease control rate of 79%. The median duration of response has not yet been reached in patients with higher NaPi2b expression. Responses are observed in those failing platinum and previously treated with bevacizumab and PARP inhibitor. Remember that current standard of care in the platinum-resistant ovarian cancer setting is single-agent chemotherapy, and multiple contemporary studies have demonstrated the performance of the standard is a response rate between 4% to 12% and a median progression-free survival of 3 to 4 months and a median overall survival of less than 1 year. In addition, it is very uncommon to see complete responses in this ovarian cancer patient population or responses that are observed to deepen over time. These data further support the continued development of XMT-1536 for the treatment of platinum-resistant ovarian cancer with poor prognosis and very limited options. Lastly, the FDA just recently granted XMT-1536 Fast Track Designation, further underscoring the high unmet medical need for a treatment for patients with platinum-resistant ovarian cancer. Finally, I would like to thank the patients, their families and caregivers taking part in this study and acknowledge my coinvestigators and the research staff, for which this study would not be possible. XMT-1536 continues to show exciting potential for my ovarian cancer patients. And I look forward to working with the Mersana team as we advance the study toward important registration-enabling studies. I will now turn the call back to Anna.

Thank you, Dr. Hamilton. We remain very excited about the continued safety and activity profile of XMT-1536 and believe this data further supports the continued development of XMT-1536 and its potential to provide a meaningful clinical benefit to these patients with very limited options. I would like to thank Dr. Hamilton and the other investigators for their continued support and enthusiasm for advancing XMT-1536 as well as the many patients and their families who have participated in this study. Now let me discuss our next steps for XMT-1536. Although we've already exceeded our enrollment goals for XMT-1536 in ovarian cancer, we will continue to strengthen our data set and plan to enroll patients in the ongoing expansion study through the remainder of the year. We're also planning to meet with the FDA around the end of 2020 to gain their feedback. We believe based on the high unmet medical need, discussions with KOLs and regulatory experts as well as based on precedence that there is an accelerated approval path in platinum-resistant ovarian cancer. In addition to our preparations for the FDA discussion and the registration-enabling study and companion diagnostics, we're also developing our longer-term development plan and life cycle management plan for XMT-1536. Operationally, we are expanding the number of sites in the U.S. as well as in Europe, Canada and Australia. We plan to provide a comprehensive update on XMT-1536 in ovarian cancer around the end of the year, given the significantly larger number of patients and longer follow-up expected, the FDA interactions regarding the registration part and the long-term life cycle management plan. Lastly, I would like to summarize our goals and milestones for the remainder of the year beyond XMT-1536. For XMT-1592, our Dolasynthen ADC targeting NaPi2b, we achieved our goal of initiating patient dosing in the dose escalation portion of the Phase I study, and we'll continue to work to achieve rapid dose escalation throughout the remainder of the year. We also continue to make great progress in advancing through exciting pipeline development candidates. We believe we're on track to disclose our B7-H4 and our first select ADC development candidate with the supporting data in the second half of this year. We will continue to maintain a strong organization with top-caliber talent and leverage strategic partnership as appropriate to build value. It has been a transformational year so far. The remainder of the year could prove to be just as transforming as we work to execute these important milestones and make further progress towards achieving our vision of significantly advancing the ADC field for the benefit of patients. We will now open the call for questions. In addition to Dr. Hamilton, we're also joined by the Mersana executive team. Operator?

[Operator Instructions] Our first question comes from Jonathan Chang with SVB Leerink.

First question for Dr. Hamilton. What are the benchmarks for duration of response in this ovarian cancer setting? And what are the duration of response -- what duration of response do you view as a meaningful in this setting?

Yes. So I'll start by saying progression-free survival or duration of response is not generally viewed as a meaningful parameter in a single-arm study. The FDA will mainly focus on response rate. But of course, duration of response is something that would be part of this context in the same way that safety or biomarker or depth and kinetics of response would be considered. I think that if we can reach at least 4 months duration of response, we are in a good place, particularly in light of the state of the standard of care and expected overall survival of less than a year. So to explain this, really, the ovarian cancer expansion cohort is recruiting platinum-resistant patients with no more than 3 lines of therapy and in some circumstances, patients could have more lines of therapy regardless of platinum status. The standard of care for these patients is single-agent chemotherapy, either Doxil or topotecan. Doxil or topotecan really has a 4% to 12% response rate and a progression-free survival of 3 to 4 months with median overall survival of less than a year. So to demonstrate superiority, one would need to exceed that response rate. As an oncologist treating these patients, I would look for a response rate of approximately 25%, and I would consider this clinically meaningful. These data suggest that we're above this response rate in both the dose escalation and the dose expansion portion of the study.

Got it. And second question, also for you, Dr. Hamilton. How would you compare the safety profile of XMT-1536 to other ovarian cancer drugs in development, particularly other ADCs in development?

Yes. So as an oncologist, we particularly like ADCs, the ability to target the cancer cell while leaving many of the other normal cells in the body alone. I think probably the drug that has had most data out there in ovarian cancer population that's an ADC was lifastuzumab, Genentech's drug. These studies certainly provided early encouraging data, establishing proof-of-concept for the target as an intervention point for an ADC. Genentech, unfortunately, did see neuropathy and neutropenia which were dose-limiting. This was particularly an issue in combination with carboplatin, which may have limited the life cycle opportunities for lifastuzumab to move into earlier lines of therapy. And in contrast, XMT-1536 has a differentiated profile without severe neuropathy or neutropenia with high response rates and quality responses and a good diagnostic to help us identify the patients that would best respond.

Our next question comes from Mike Ulz with Baird.

Congrats on the data. Just a quick question for you, Anna. You mentioned meeting with the FDA around year-end. Just curious if you think that will happen prior to your update? And do you think you'll be in a position to maybe give some clarity on feedback in terms of the path forward at that sort of year-end update?

We do plan to have the year-end update after we've met with the FDA. And what we'd like to do at that year-end update is provide a more complete and mature readout of the expansion cohort. Remember, we had 47 patients as of the date of the data cutoff for this disclosure. So we will have not only more patients that will be recruited to the expansion cohort in the intervening next few months, but we'll also have more mature data on these patients. And we also want to be able to lay out the path to registration based on FDA feedback and our own plans as well as our plans, we're currently putting in place for life cycle management. So that further disclosure around the end of the year should be a very comprehensive disclosure on XMT-1536.

Got you. That's helpful. And then maybe just on the biomarker data, just given the update, I know you're waiting for more data around year-end to sort of figure out the cutoff, but maybe just talk about your level of confidence in the biomarker. And then I noticed also -- yes, go ahead.

Go ahead, sorry.

And then I just noticed there was 1 or 2 PRs that weren't typed yet. Is that just a timing issue? Or will you maybe not be able to get the biomarker status for those?

It's a timing issue. At the time of the data cutoff, we didn't have the data, but this is an ongoing trial. So it's not -- it's a timing issue. As for the biomarker, we've always said that we're going to look at the complete data set before making decisions about patient selection. We are seeing a correlation between the level of expression and the pattern of expression of the antigen. And we're seeing a correlation with response, but also the quality of response, the depth, the duration. And we're going to look at the complete data set before we define and articulate what our patient selection strategy will be in the registration study. That being said, the activity level of this seen in the total population is quite robust and well over the threshold we believe would be required for approval. So we feel we're in a good position there, and we're learning a lot about the role of the biomarker with every additional patient we're treating in the expansion cohort.

Our next question comes from Tom Shrader with BTIG.

Congratulations on another nice update. Can you let us know the major reason for dose reduction? And can you characterize the fatigue relative to something like a PARP inhibitor, which I think has a lot of fatigue?

Erika, that's a good question for you.

Yes. I think that the reasons for dose reductions really have been multifactorial. The main reason for patients coming off drug has been progressive disease. Only 2 patients out of the 47 ovarian cancer patients so far treated have discontinued for treatment-related adverse events. Some have been dose reduced for side effects, some have been dose reduced for AST, some have been dose reduced for fatigue, but it's not 1 predominant factor.

Okay. And to my eye, the 36 mg dose looks pretty good. Are the dose reductions meaningfully different in that arm? So -- and is that a real effect or is it just small numbers?

Yes. I think that it's hard to say because there are small numbers. There are small numbers of patients that have been dose reduced. The safety profile at 43 milligrams per meter squared is certainly very similar to that at 36 milligrams per meter squared without severe neutropenia, neuropathy or ocular toxicity. And the activity profile also appears to be similar, which is a very positive sign because it gives physicians options in reducing the dose to manage tolerability for patients.

Our next question comes from Boris Peaker with Cowen.

I'd like to add my congratulations as well on the data. My first question is on the fresh biopsy. I'm just curious of all the patients treated, how many were you able to obtain a fresh biopsy from? And what were you able to learn from fresh biopsy versus archival biopsy?

So Boris, I don't have the answer to your first question, but we can get that in terms of what percentage of patients we have both archival and fresh tissue. I think the -- overall, we're seeing a fairly good concordance between the fresh and the archival issue.

Great. And my second question is, if we look at all the patients treated, I think you mentioned 100 or over 100 on the drug. I'm just curious, or maybe even broader, of all the patients screened, based on your current high definition for NaPi2b, what fraction of patients fall into that category?

It's about 2/3 of the patient population that falls into that category.

[Operator Instructions] Our next question comes from Jessica Fye with JPMorgan.

Maybe just following up on, I think it was Mike's question, related to defining patient selection. How much follow-up do you think you will need to establish this? And how important is getting a beat on durability as an input in that decision? Is that something you'll be able to make a call on when you get to the December follow-up? Or is that something that could extend into the spring?

We believe we have -- we will have a very strong and comprehensive data set by the end of the year. Remember just that we have 47 patients as of the earlier part of August. We continue to recruit. Those 47 patients will have another 3 or 4 months of follow-up by the end of the year. That's in addition to the 29 we already -- this is the 29 we already reported on, and the additional, I guess, 18 that get us to 47, and then the additional patients we will recruit beyond that. We think it will be a comprehensive data set.

Okay. Great. And I might have not caught this on the poster, but is one of the new PRs, the conversion from the prior unconfirmed CR, you talked about with the ASCO update?

Actually, that's a patient of Dr. Hamilton, and that is the case. That's the one case she presented the 29% that then became 50%.

Okay. Great. And last one is duration of response for the overall population, I know you said it wasn't reached for the high expressors and the poster has some comments on individual low expressors. But what about overall, is there anything you can say about that?

Look, the numbers are very small. The numbers are too small to really say much. We do see the trend on the quality and depth with higher expression. And I think what we need is additional patients and additional responses in order to have really look at the duration of response in a way that's much more meaningful with much narrow in confidence intervals.

Our next question comes from David Nierengarten with Wedbush Securities.

Just a quick one. Has there been any differences? And it's probably too small numbers, but any differences in number of prior treatments or any particular prior treatment like bevacizumab leading to different outcomes with 1536?

That's a great question. We continue to look at that. In our responses versus previous treatment paradigms, we have not seen any differences. And as we've said on the call and at the time of the ASCO disclosure, 2 complete responses we saw were patients that had exhausted platinum, bevacizumab and PARP inhibitors.

Thank you. And I'm currently showing no further questions at this time. I'd like to turn the call back over to Anna Protopapas for closing remarks.

Thank you. Thank you all for listening on the call. We appreciate your continued support. We want to thank Dr. Hamilton and all the other investigators and patients and their families that are continuing to help us advance this promising therapy. Have a good day.

Ladies and gentlemen, this concludes today's conference call. Thank you for participating. You may now disconnect.