Earnings call transcript: Mersana Therapeutics reports Q1 2025 loss, stock up 6.14%

Mersana Therapeutics (NASDAQ:MRSN) reported its first-quarter 2025 earnings, revealing a net loss of $24.1 million, which aligns with analysts’ expectations of an EPS of -0.19. Despite the revenue falling short of forecasts, the stock rose by 6.14% in premarket trading, closing at $0.38. According to InvestingPro data, the company maintains a strong liquidity position with more cash than debt on its balance sheet, though it’s currently trading below its Fair Value. The company is focusing on its breast cancer treatment pipeline, which could be a factor in the positive market reaction.

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Key Takeaways

• Mersana reported a net loss of $24.1 million, matching EPS forecasts.
• Revenue was $2.75 million, missing the $6.05 million forecast.
• Stock price increased by 6.14% in premarket trading.
• Strategic restructuring and workforce reduction announced.
• Focus remains on expanding breast cancer treatment pipeline.

Company Performance

Mersana Therapeutics continues to navigate challenging financial waters, with a net loss of $24.1 million in Q1 2025, up from a $19.3 million loss in the same period last year. InvestingPro analysis shows the company’s Financial Health Score stands at 1.93 (Fair), with particularly concerning metrics in profitability and cash flow. The company’s focus on its breast cancer treatment pipeline, specifically the EMILY program, highlights a strategic shift towards areas with high unmet medical needs. This pivot is underscored by a strategic restructuring that includes a workforce reduction, aimed at extending the cash runway while maintaining a current ratio of 2.19x.

Financial Highlights

• Revenue: $2.75 million, down from $9.2 million in Q1 2024
• Earnings per share: -0.19, meeting analyst expectations
• Cash and cash equivalents: $102.3 million
• Net cash used in operations: $29.3 million

Earnings vs. Forecast

Mersana’s earnings per share of -0.19 met analyst expectations, while revenue fell short at $2.75 million compared to the $6.05 million forecast. This revenue miss represents a significant deviation from expectations, potentially due to decreased collaboration revenue.

Market Reaction

Despite the revenue miss, Mersana’s stock rose by 6.14% to $0.38 in premarket trading. This positive movement may reflect investor optimism about the company’s strategic focus on its breast cancer pipeline and cost-cutting measures. InvestingPro data reveals a significant ~13% return over the last week, though the stock has declined over 85% in the past year. The stock remains above its 52-week low of $0.259 but well below its high of $2.83.

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Outlook & Guidance

Mersana has extended its expected cash runway into mid-2026, providing a stable financial foundation for ongoing development. The company plans to share initial clinical expansion data in the second half of 2025, with potential for a randomized Phase 3 trial focusing on progression-free and overall survival endpoints.

Executive Commentary

"We remain excited about Mersana’s prospects," stated Dr. Marty Huber, CEO, highlighting the potential of the company’s breast cancer treatment pipeline. Another executive noted, "We view this as a very positive development for patients and for the size of the opportunity that we’re pursuing."

Risks and Challenges

• Revenue shortfall: Continued underperformance in revenue could strain financial resources.
• Clinical trial risks: Success of the EMILY program is not guaranteed, posing a risk to future growth.
• Competitive pressure: Other companies targeting the same patient population could impact market share.
• Workforce reduction: Could affect operational efficiency and morale.

Q&A

During the earnings call, analysts focused on dosing strategies and the rationale behind the company’s B7H4 expression cutoff for patient selection. Questions also addressed the potential for randomized clinical trials and the expansion cohort focus on breast cancer, indicating a high level of interest in Mersana’s strategic direction.

Full transcript - Mersana Therapeutics Inc (MRSN) Q1 2025:

Conference Operator: Good morning, and welcome to the Mersana Therapeutics First Quarter twenty twenty five Conference Call. Currently, all participants are in a listen only mode. There will be a question and answer session at the end of this call. I would now like to turn the call over to Mr. Jason Fredett, Senior Vice President, Investor Relations and Corporate Communications.

Please proceed, sir.

Jason Fredett, Senior Vice President, Investor Relations and Corporate Communications, Mersana Therapeutics: Thank you, operator, and good morning, everyone. Before we begin, please note that this call will contain forward looking statements within the meaning of federal securities laws. These statements may include, but are not limited to, those related to the potential clinical benefits of our product candidates and platforms, our clinical trial progress and design addressable market opportunities anticipated clinical milestones and data presentations and cash runway. Each of these forward looking statements is subject to risks and uncertainties that could cause actual results to differ materially from those in such statements. These risks and uncertainties are discussed in our annual report on Form 10 ks filed with the Securities and Exchange Commission on 03/03/2025, and in subsequent SEC filings.

Our filings are available at sec.gov and on our website, mersana.com. Except as required by law, we assume no obligation to update forward looking statements publicly even if new information becomes available in the future. On today’s call, we have Mersana’s Chief Executive Officer, Doctor. Marty Huber and our Chief Operating Officer and Chief Financial Officer, Brian Deschitner. With that, let me turn the call over to Marty to begin the discussion.

Dr. Marty Huber, Chief Executive Officer, Mersana Therapeutics: Thank you, Jason, and good morning, everyone. Let’s begin by touching on last week’s announcement of Mersana’s strategic restructuring and reprioritization plan. This plan includes several cost savings initiatives. Among them are the reduction of about 55 of our workforce across functions, the elimination of our internal pipeline development efforts, a reduction of other research activities, and a narrowing of our clinical development work with Emily to focus on breast cancer. We will continue supporting phase one dose escalation work for XMT-two thousand and fifty six and our ongoing collaborations.

Our main objective, however, was to extend our cash runway into mid-twenty twenty six to give us the opportunity to generate important objective response rate and durability data for Emily from both of our ongoing phase one dose expansion cohorts. Many of our colleagues learned last week that they will be departing Mersana today, and others will be leaving in the near term. I would like to take a moment to thank them for all they have contributed to our programs and our patient centric culture. Now let’s move on to a very timely topic. Early this morning at the ESMO Breast Cancer twenty twenty five Congress in Munich, Doctor.

Erica Hamilton, who heads up breast cancer research at the Sarah Cannon Research Institute, presented updated clinical data for EMILI, our dolisinthin B7 H4 ADC. The presentation primarily focused on preliminary time to event data from patients with triple negative breast cancer, or TNBC, who are enrolled in our dose escalation and backfill cohorts. Safety and tolerability data in this population remained consistent with those previously reported, with no new safety signals. Now, before getting into the clinical activity data, it may be helpful to share a little context upfront. First, it’s worth noting that research has shown B7 H4 expression is a negative prognostic factor in various cancers, including in TNBC.

In other words, clinical outcomes in patients with higher B7 H4 expression are generally worse than those for patients with lower expression. Additionally, it is helpful to know what the performance is for today’s standard of care in late line TNBC, namely single agent chemotherapy. A key reference for this is ASCENT, Trudelby’s registrational trial in relapsed and refractory TNBC. In that trial, patients receiving chemotherapy achieved an objective response rate, or ORR, of only five percent. The median progression free survival, or PFS, was about seven weeks, and median overall survival, or OS, was about seven months.

Those data were from patients who were naive to Topo-one ADCs. Ultimately, we believe that this is the type of time to event data that a new agent would need to beat in a potential randomized pivotal trial in post TOPO-one TNBC for full approval. And given these low bars, we believe such a randomized trial would not take much longer than a single arm trial. With that, let’s briefly recap the clinical activity data presented this morning. The presentation focused on our valuable patients with TNBC who received intermediate doses of EMILY ranging from about thirty eight milligrams per meter squared up to about sixty seven milligrams per meter squared.

Importantly, more than eighty percent of these TNBC patients had received a prior TOPA one hundred C. Among those patients with B7 H4 low tumors who received four or fewer prior lines of treatment, the ORR was zero percent. The median PFS was six point four weeks, and the median OS was five point seven months. But among those patients with what we have initially characterized as B7 H4 high tumors, who received four or fewer prior lines of therapy, the ORR was twenty nine percent. The median PFS was sixteen weeks and the median OS had not yet been reached as of the data cutoff of March 8.

As a reminder, our current dose expansion cohorts are only enrolling TNBC patients who receive four fewer prior lines of therapy, including at least one prior Topo-one hundred eighty C. While some patients with B7 H4 low tumor expression are being enrolled, our primary focus is on the B7 H4 high TNBC population. And so, while the sample size from dose escalation and backfill is small, today’s presentation sheds further light on why we continue to believe EMILY could represent a meaningful improvement over today’s standard of care for patients with post Topo one TNBC. The ESMO breast presentation also contained an update on clinical activity observed across all tumor types in dose escalation and backfill cohorts as of that data cutoff of March 8. ’8 of ’20 ’6 evaluable patients with B7 H4 high tumor expression who received intermediate doses of EMILY achieved a confirmed response for an ORR of 31%.

This is an increase from the twenty three percent ORR that was reported based upon our December 2024 data cutoff. Further details are contained in the ESMO breast presentation, which can be accessed on the publication sections of our website at mersana.com. We will be sharing some additional clinical data from dose escalation and backfill cohorts across all tumor types based on that March 8 beta cutoff in an oral presentation at ASCO in a couple weeks. So where do we stand with our expansion work with Emily? Well, we’re making great progress.

Again, in expansion, we are focusing on patients with TNBC who have received one to four prior lines of therapy, including at least one prior topo-one ADC. Enrollment in our initial expansion cohort that is receiving sixty seven point four milligrams per meter square dose of EMILY every four weeks has advanced rapidly in twenty twenty five. As a reminder, we amended our clinical trial protocol in the first quarter of this year with the goal of mitigating proteinuria related dose delays we had seen at higher doses of EMILY. These proteinuria management guidelines have now been adopted at our clinical sites. I’m also happy to share that we recently initiated and have progressed patient enrollment in our second TNBC expansion cohort.

These patients are receiving a starting dose of forty four point five milligrams per meter squared of EMILY on days one and eight of the first four week cycle, followed by eighty milligrams per meter squared every four weeks. We chose this regimen for a few reasons. First, all four of the evaluable b seven h four high patients who received the forty four point five milligram per meter squared day one day eight dose every four weeks in dose escalation and backfill cohorts achieved tumor reductions of at least thirty percent. Second, we believe our recent protocol amendment will enable us to maintain dose intensity and tolerability for our eighty milligram per meter squared Q4 dose. And third, our PK work showed that exposures for this regimen are distinct versus our sixty seven milligram per meter squared every four week dose, which we believe may be helpful in the spirit of Project Optimus.

As we continue advancing our work and expansion, we are also witnessing a series of developments that could significantly expand the post TOPO-one patient pool. Up until now, in the breast cancer space, TOPO-one ADCs have only been approved for relapsed and refractory patients. But in recent months, there have been multiple positive Phase three readouts for topos in the frontline setting. Focusing specifically on the TNBC, as we’ve noted before, global TNBC revenues for Trodelvy in 2025 are projected to exceed $1,000,000,000 Just a few weeks ago, positive top line results were shared from ASCENT-four, a clinical trial for the combination of Trodelvy and Keytruda in frontline TNBC. This readout may enable Trodelvy to become the new standard of care for first line PD L1 positive TNBC.

And with results from the phase three ASCENT-three trial in PD L1 negative patients also expected in the weeks ahead, we believe the post TOPO-one TNBC patient population could expand substantially. In summary, we remain excited about Mersana’s prospects. We’re making great progress with expansion enrollment and we are looking forward to sharing initial clinical data from expansion in the second half of this year. With that, let’s turn the call over to Brian for our financial review.

Brian Deschitner, Chief Operating Officer and Chief Financial Officer, Mersana Therapeutics: Thank you, Marty. Beginning with our balance sheet, we ended the first quarter of twenty twenty five with 102,300,000 in cash and cash equivalents. Due in part to the restructuring and reprioritization plan we announced last week, we expect that our capital resources will enable us to support our current operating plan commitments into mid-twenty twenty six. Please note that our cash runway guidance does not assume any future milestone payments that we may earn from our current collaborations or proceeds that we may realize from future collaborations. Net cash used in operating activities for the first quarter of twenty twenty five was $29,300,000 Turning to our income statement, collaboration revenue for the first quarter of twenty twenty five was $2,800,000 compared to $9,200,000 for the same period in 2024.

The year over year change was primarily related to reduced revenue recognized under our collaboration and license agreements with J and J and Merck KJA. Research and development expenses for the first quarter of twenty twenty five were $18,300,000 compared to $18,700,000 for the same period in 2024. For the most recent quarter, approximately $1,400,000 of this spending was related to non cash stock based compensation. The year over year change was primarily related to our lower headcount and related employee compensation costs, partially offset by an increase in costs related to MLE clinical development activities. General and administrative expenses for the first quarter of twenty twenty five declined to $8,900,000 compared to $11,600,000 during the same period in 2024.

Approximately $1,300,000 in non cash stock based compensation expenses were included in G and A for the most recent quarter. The year over year decline was primarily related to a reduction in consulting and professional services fees, as well as the company’s lower headcount and related employee compensation costs. And finally, Mersana’s net loss for the first quarter of twenty twenty five was $24,100,000 compared to a net loss of $19,300,000 for the same period in 2024. That concludes our business update. Operator, would you please open the call to questions from the audience?

Conference Operator: Thank you. We will now begin the question and answer session. And the first question will come from Tara Bancroft with TD Cowen. Please go ahead.

Tara Bancroft, Analyst, TD Cowen: Hi, good morning and thanks for taking the questions. I was hoping you could expand a little bit more even qualitatively on the high dose, especially regarding safety and the updated protocol. I know you mentioned that the PK profiles were pretty distinct, I’d love to hear more about that. And if an update here will be included in the ASCO update at all? Thanks so much.

Unnamed Speaker, Company Representative, Mersana Therapeutics: Thanks, Tara. Well, just last one first. This is part of the second dose level, the four thousand four hundred forty five is part of expansion. And just to be clear, the data we are sharing at ASCO is based on escalation and backfill only. There is not going to be expansion data at ASCO.

So these data would not be included in that presentation. With regards to the rationale, I think I’m going to work backwards to the PK. One of the things you want to look for when you study a second dose is make sure that from an exposure point of view, it’s a discrete dose level and it’s not overlapping. In other words, it needs to be a meaningfully higher dose. Because if you think about the Project OPTIMASP project, if you have two doses that are eighty percent of the patients are overlapping in exposure, it’s really not a second dose.

So we were looking for a dose that is meaningfully higher than sixty seven Q4. So the dose we’re putting forward at forty four point five day one day eight followed by eighty is a meaningfully higher exposure than you achieved with sixty seven. And then the final part of why we believe it’s doable is when we evaluated our data, one of the observations we found is the forty four point five day one day eight was the most effective dose in ensuring a tumor reduction at week six. So it clearly had I mean, I said four out of four patients who were B7 H4 high with measurable tumors of baseline who got that dose, we fixed. The problem we had with forty four point five, was the proteinuria also resulted in patients interrupting treatment.

So now we believe with the proteinuria mitigation efforts in place that we will be able to maintain it. Now the question then is, well, why did you go from a day one, day eight to then an eighty? Well, an eighty is also a meaningfully higher exposure. But fundamentally, you do run into a problem of trying to do a day one, day eight and maintaining that every cycle just gets to be challenging. Whereas 80 every four weeks gives you an exposure in the ballpark of 45 day one day eight.

But it’s a much when we talk to our investigators, there was a lot of negative feedback about trying to maintain a day one, day eight schedule on an ongoing basis. But we did think it’s worth it trying to get it in for that or getting it in for that first cycle because that really is our best shot at efficacy.

Tara Bancroft, Analyst, TD Cowen: Okay, great. Thank you so much.

Conference Operator: The next question will come from Charles Xu with LifeSci Capital. Please go ahead.

Charles Xu, Analyst, LifeSci Capital: Hey, good morning everyone. Thanks for taking the questions. Congrats on the progress and nice to see some of these response rates ticking upwards a bit. I have a question regarding maybe some of the ASCENT-three and ASCENT four studies either having already read out or about to read out. How might these assuming ASCENT three is also successful like a change standard of care and impact if at all your clinical development plans in the post topo setting?

And really what I’m getting at here is would you expect any sort of like different patient based on characteristics or outcomes based on whether or not they get this new standard of care versus getting the priorcurrent standard of care? Thank you.

Unnamed Speaker, Company Representative, Mersana Therapeutics: Charles, maybe I’ll take that one. As you know, our expansion cohort is exclusively looking at post TOPO-one TNBC. And so I think while we certainly have activity, we’ve shown this in the January data disclosure in non TOPO pretreated patients, in The U. S. And in Western Europe, the penetration of these topo delivering ADCs has been very, very rapid into the recurrent setting as Marty noted in his remarks.

I think what this provides the opportunity for is the earlier those agents are used, the more and more patients fall into this post TOPO-one category. And we know that very uniquely, we retain activity in that space. In fact, we’ve been deliberately studying that space because it’s one of the highest unmet needs in breast cancer. What do you do once you induce resistance phenotype in a patient post TOPO-one? It’s a serious question for many of the physicians.

We have been uniquely in the space for B784 recruiting those types of patients to ask that hard question. And so we view this as a very positive development for patients and for the size of the opportunity that we’re pursuing.

Charles Xu, Analyst, LifeSci Capital: Got it. Great. Thank you.

Conference Operator: The next question will come from Michael Schmidt with Guggenheim. Please go ahead.

Michael Schmidt, Analyst, Guggenheim: Hey, good morning. Thanks for taking my questions. Yes, maybe just a couple of follow ups. Again, nice to see these additional two responses in the intermediate dose. Could you just comment on what types of patients those were?

Were those two TNBC patients or perhaps some of the other histology? And then, just curious if you could provide some qualitative perhaps comments on the impact of some of the protocol amendments that you’ve implemented to manage some of the proteinuria and prophylaxis. How has that sort of what was the experience with that so far? And has that indeed resulted in perhaps lowering proteinuria or delays on these treatment holes? And then lastly, could you just give us a sense of enrollment at the sixty seven milligram cohort and how that’s been progressing and how substantial this update in the second half later this year will be?

Thanks so much.

Unnamed Speaker, Company Representative, Mersana Therapeutics: I’m going start work backwards. So on the 67 enrollment, we’re not giving further guidance. I think what we suffice it to say, we’ve seen sufficient enrollment that we felt comfortable issuing a new guidance. We kind of since we kind of run out of guidance for the year because we’d actually achieved all the stuff we said we were going do. So we decided that when we looked at our enrollment, we have enough patients that we felt confident we would have a data set.

And one of the questions we want to do is make sure we have a data set that had enough durability because that’s as you all recall from our initial data set that was one of the questions. So I think as far we’re not giving actual sample sizes yet, but I think the fact that we’ve switched from 67 to the second dose should indicate we’re doing fine on enrollment. And I think for any of you who happen to get up at two a. M. And listen to Erica’s call and our people on the ground in Munich have been telling us the investigator enthusiasm has been high and we’re seeing that in the enrollment.

So I think this niche of post Topo now, we’ve clearly become if you have this trial available for your patients, you’re putting your patients on it. So this is so that’s why I think we’re comfortable putting out the new guidance for second half. With regards to the proteinuria, once again we’re not giving any data yet. And I think probably a couple of things that are important to understand about that is the mitigations that we’re doing we do not anticipate them ever taking proteinuria to zero. So we want to be very clear.

Our expectation is you’re still going to see an AE of proteinuria in these patients. What this is about is managing consequences of avoiding the development of serum hypoalbuminemia changes in creatinine. And I think we’re at the point now we’re confident enough in our mitigation efforts that we are comfortable opening the expansion at the new dose and regimen. We will I mean at some when we share the data on this dose in the second half then we can get into more details of exactly what that looks like. And the first question was the thirty one percent ORR.

Tumor types. Yes, those both were ACC1s. But as far as the more details of that, we in our upcoming ASCO presentation, whereas ESMO kind of covered the focused on TNBC, Erica is going to focus on the other tumor types, including these thirty one percent at the ASCO presentation. And a few more things that we can’t disclose yet on that data set.

Michael Schmidt, Analyst, Guggenheim: All right. Thank you.

Conference Operator: Our next question will come from Jonathan Chang with Leerink Partners. Please go ahead.

Jonathan Chang, Analyst, Leerink Partners: Hi, guys. Good morning. Thanks for taking my questions. First question, are there additional dosing regimens that could be further evaluated beyond dose A and B in the expansion or have you settled on these two dose cohorts? And second question, can you help set expectations on the upcoming ASCO presentation?

What

Unnamed Speaker, Company Representative, Mersana Therapeutics: could

Jonathan Chang, Analyst, Leerink Partners: we learn at ASCO relative to the disclosure today? Thank you.

Unnamed Speaker, Company Representative, Mersana Therapeutics: First of all, with regards to the doses, these are the two doses that we are taking into expansion. We do not anticipate any others. Obviously, we always we’re data driven if we learn something new from the data. But the go forward plan is that it would be either of these two doses. And in fact that’s one of the reasons we kind of scheduled on this kind of loading then switch to ADQ4 because we believe doing the loading for one cycle and then switching to ADQ4 is a viable dose and schedule to take forward assuming the data supports it.

But we do not we’ve obviously looked at other doses and schedules as part of our backfill. But at this point in time, we don’t have any plans to take any of those forward. And with regards to the ASCO presentation, I think really probably knowing that companies have gotten in trouble for violating embargo, we don’t I mean, this is our first oral presentation as a company. And the last thing I would hate to do is see the guy who lost it because I blew an embargo. But I think we can be very clear on to set expectations.

This is the backfill and escalation data. There is not going to be expansion data at ASCO.

Jonathan Chang, Analyst, Leerink Partners: Understood. Thanks for taking my questions.

Conference Operator: The next question will come from Colleen Cousy with Baird. Please go ahead.

Tara Bancroft, Analyst, TD Cowen: Hi, good morning. Congrats on all the progress and thanks for taking our questions. Marty, think you mentioned something about a randomized Phase three taking not much longer than a single arm. So could you just provide a little bit more color on what you’re thinking on a potential pivotal study? And I have a follow-up please.

Unnamed Speaker, Company Representative, Mersana Therapeutics: I mean, a lot of people ask those questions of, is your response rate going to be high enough for an accelerated approval? And I think one of the things we’re looking we think that’s actually kind of irrelevant question. Because fundamentally, if you could do a randomized trial in a similar timeframe as a non randomized trial, that’s always the better way to go. And there’s I’ll give you three reasons to that. One is from a regulatory point of view and now you have to think beyond The U.

S. On a global basis, a randomized trial you can file anywhere. A lot of companies have discovered you do these accelerated approval strategies with a single arm trial and then you can’t go anywhere else. And then you’re kind of stuck waiting for a randomized trial. The second point is you still end up having to do the randomized confirmatory trial.

And if that randomized confirmatory trial is not well underway or near complete, you can get in trouble of not getting an approval because you haven’t progressed your confirmatory trial. And that’s a point where the agency has gotten very, very sticky. They really, really want to know that the definition of well underway is getting they basically want to know your trial is going to read out before they approve you. And then the other area where it comes in and this is one of the things we were very pleased with sharing at ESMO is things like if you look at diseases like TNBC, post topo especially, where patients are progressing in six weeks and dying in six months or less is what’s important for physicians is to understand not only the response rate, but stable disease as well. In TNBC post topo, a patient who doesn’t progress in eighteen weeks is deriving a meaningful benefit from the treatment because we know the natural history of that patient is they progress in six weeks.

And then finally, you can actually in a randomized trial in TNBC, by the time you finish enrollment, you’ll probably already have enough endpoints for PFS. So you could basically complete your enrollment and almost turn around and look at your PFS endpoint the next day. And then your survival endpoint is literally coming in within months of that. So we think there’s an opportunity with a randomized trial to avoid a confirmatory trial and get OS data even if it’s a secondary endpoint rapidly. And then once you have that data set, we think that makes it all this churn you’re seeing at the FDA about are they going to accept randomized trials or do they want placebo controlled or all that nonsense just goes away if you run a randomized trial because you’re walking in with what everybody would agree is the gold standard of trials.

Tara Bancroft, Analyst, TD Cowen: Got it. That’s super helpful.

Unnamed Speaker, Company Representative, Mersana Therapeutics: Obviously, all this and just to be clear, we have not had a formal regulatory advice on this. But on that point, I think I would be shocked if the FDA wouldn’t accept a randomized trial with PFS and OS as your endpoints.

Tara Bancroft, Analyst, TD Cowen: Got it. Okay. Super helpful. And then in that context, can you just talk about the cutoff for B7 H4 expression? And how much additional work needs to

Jason Fredett, Senior Vice President, Investor Relations and Corporate Communications, Mersana Therapeutics0: be done before you feel like

Tara Bancroft, Analyst, TD Cowen: you can totally confirm that?

Unnamed Speaker, Company Representative, Mersana Therapeutics: We’re doing that work in expansion. There were when you switch to a pre commercial assay, there were a few tweaks in the assay between escalation of backfill and expansion. So in expansion, it is possible that the TPS score comes out to be a slightly different place. But I think what’s important to understand is even if the TPS score shifts a little bit, we still fully anticipate that forty percent to fifty percent of patients are going to be positive. So the actual score may change a little bit, but we would be surprised

Unnamed Speaker, Company Representative, Mersana Therapeutics: if the percent of patients who are positive dramatically changed. And that’s probably an important point as you think about the competitive landscape because people have different specifications around their research assays. The specification doesn’t matter so much, sustaining conditions, sustaining time, the temperature. What you’re looking for in B784 is about 4050% of the population. And so regardless of what how someone describes the conditions of their assay, they’re likely identifying the same patients.

Jason Fredett, Senior Vice President, Investor Relations and Corporate Communications, Mersana Therapeutics0: Got it. That’s great. Thanks for taking our questions.

Conference Operator: Your next question will come from Andy Hussain with William Blair. Please go ahead.

Jonathan Chang, Analyst, Leerink Partners: Thanks for taking our questions.

Conference Operator: Two quick ones from us.

Jonathan Chang, Analyst, Leerink Partners: One is about the post topo dynamic. I think at the conference, Doctor. Taleny presented almost 200 patients worth of data showing similar PFS for the intermediate or after an intermediary chemo for TOPA ADC rechallenge. And so that I guess to from my perspective, suggesting a resistant phenotype is more longer term. I’m curious about your take on that data.

And then secondarily, in the January update for the triple negative cohort, there were three patients with treatment ongoing. I’m just curious about the status of these three patients for the March update. Thank you.

Unnamed Speaker, Company Representative, Mersana Therapeutics: With regard to your first question, I mean, I’m not in Munich. I’m in I stayed behind because of the restructuring and the earnings. So I cannot I want to be careful commenting on our presentation, which I did not see. So I’ll have to go back and look at that. We did have people on the ground.

I’ll have to we’ll find out from them. With regards to the details of the ongoing status, I think I would defer that, as I said, to the ASCO, we will be giving an update the March update for all patients at the ASCO presentation. And I really don’t want to front run that.

Conference Operator: The next question will come from Asika Goonewardene with Truist. Please go ahead.

Jason Fredett, Senior Vice President, Investor Relations and Corporate Communications, Mersana Therapeutics0: Hi, this is Karina for Arstica. Thanks for taking my question. I had a follow-up on the B7 H4 expression. What proportion of patients have B7 H4 expression greater than 70? In your previous presentation, you had forty out of one hundred and thirty patients.

So should we assume around roughly thirty percent of the population?

Unnamed Speaker, Company Representative, Mersana Therapeutics: I think we for TNBC, we’re comfortable that a number will be somewhere between forty percent and fifty percent of the population.

Jason Fredett, Senior Vice President, Investor Relations and Corporate Communications, Mersana Therapeutics0: Okay. So forty percent to fifty percent. And then also regarding proteinuria medication strategies for the ACE inhibitor prophylaxis, is that initiated only once the patient exhibit signs of proteinuria or at a specific threshold?

Unnamed Speaker, Company Representative, Mersana Therapeutics: In the new amendment that has now been adopted at most of the sites, you are encouraged to start that prophylactically prior I mean basically at the initiation of treatment unless the patient has a contraindication for the ACE or ARM.

Jason Fredett, Senior Vice President, Investor Relations and Corporate Communications, Mersana Therapeutics0: Okay. Thank you so much.

Conference Operator: Our next question will come from Jeet Mukherjee with BTIG. Please go ahead.

Jason Fredett, Senior Vice President, Investor Relations and Corporate Communications, Mersana Therapeutics1: Hey, good morning and thanks for taking the question. Maybe two quick questions from me. With the sixty seven point four mg and forty four point five mg doses now moving forward in expansion, what would you ultimately want to see from a target product profile perspective to justify moving forty four point five over the other dose, and into pivotal studies? And just in terms of the expansion update later this year, will it be strictly in TNBC patients? Or could we also expect to see, say, ovarian or endometrial patients for that update?

Thanks. Sure.

Unnamed Speaker, Company Representative, Mersana Therapeutics: With regards to your first question, I mean, with if the efficacy for the higher dose is not meaningfully better than 67Q4, 67Q4 is the dose we would take forward because it’s just the proteinuria is much less of an issue there and it’s just a fairly straightforward and easy regimen to do. The intent of the higher dose intensity upfront is getting patients into response faster, which is important in a very aggressive disease like TNBC, especially these late line post topo patients. What with regards to the your other question was sorry, blanking. Just in terms

Jason Fredett, Senior Vice President, Investor Relations and Corporate Communications, Mersana Therapeutics1: of the expectation. Yes.

Unnamed Speaker, Company Representative, Mersana Therapeutics: And actually this is I’m glad you asked that because this is one of the areas I think we probably didn’t the impact of restructuring when people are saying what did we stop doing as part of this. One of the things that we are not doing is we originally had planned to be starting multiple expansions across multiple tumor types. And so one of the reasons we can get by with a smaller organization is it’s going to be a very breast cancer focused expansion program. So the ovarian and endometrial data that we have already in back fill and escalation that will be at the ASCO presentation, but there will not be in 2025 new expansion data beyond breast cancer. And that is just an unfortunate consequence of extending cash runway.

But we still want to look at those two indications. It’s just we had to prioritize at this point in time. Thank you.

Conference Operator: This concludes our question and answer session. I would like to turn the conference back over to Doctor. Marty Huber for any closing remarks. Please go ahead, sir.

Unnamed Speaker, Company Representative, Mersana Therapeutics: Thank you, operator, and thanks everyone for dialing in. We’ll look forward to seeing many of you in Chicago and ASCO in a couple of weeks. That concludes our call. Thank you.

Conference Operator: The conference has now concluded. Thank you for attending today’s presentation. You may now disconnect.

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