Conference Transcript - STRO 2026-06-04

Roger Song, Analyst — Jefferies

Welcome, everyone, to Jeffrey's 2026 Global Healthcare Conference. My name is Roger Song, senior, and this covers SmidCat Biotech. It is my great pleasure to introduce our next company, Sutro BioPharm, and then having a fireside chat with the CEO, Jane Chang, and then Jonathan. So, Jane, so why not you give us a state of art for Sutro? We have a lot of things we can talk about, and then the most exciting kind of data readout in my coverage, I would say in the coming weeks and then yeah so yeah so great to be here with you Roger and at

Jane Chang, CEO

Jeffries we are very excited with the momentum that the suture company has been delivering when we made this big pivot last year last March we had committed to three programs getting into the clinic in three years and now we're on track after transforming our business to delivering three programs into the clinic in two years so we're accelerating our pipeline we've reduced and streamlined our operations and we're very excited with our first program already into the clinic it's a tissue factor adc where we get to see our ultra design capabilities of four adcs our technology is very unique it's a platform that can deliver on very differentiated programs because we have the ability to optimize every component of an ADC, including the antibody, the linker, and the payload, and the sites of conjugation and how everything is combined, which is very, very different from conventional ADC companies where they focus on one or two features. And so this is when you can design something to be really meaningfully different. And we have, in a very short amount of time, built a pipeline that is very differentiated as well. It includes two single payload ADCs that go after complex targets, which are, we say they're complex because they're expressed on both normal tissue and cancer tissue, and you need to be able to strike the right balance while also delivering on a very potent payload. In addition, we feel that we can contribute to the future field of the ADCs with the innovation that we have designing our dual payload ADCs. Again, this is what's next, what's the big step next in terms of ADC innovation. Resistance, we believe, to ADCs will be driven not by target but more by the payload class. And so we're already developing and discovering the next generation of payloads as well as combination strategies to deliver in a targeted way.

Roger Song, Analyst — Jefferies

Excellent, Jane. You know, I have to say this. Sutro is my number one covered company as a senior analyst. It's been a long role. I've been working on this for like 10 years. And then, Jay, I give you the quote to how you transform Sutro and then with the new management team as well. So Sutro has a very unique, self-free synthesis kind of platform. I think it's very, very powerful. We all know Vaxxar stories are literally coming from that platform. So it's been a long role. but right now it seems you are cracking the nuts to developing some next gen or if not a third or fourth gen of the ADC with a couple pipelines in the clinic and with tissue factor ADC as the lead. So maybe we focus a little bit more today's conversation on the upcoming data readout mid-year tissue factor ADC. We put out a preview note earlier after talking with you as well. So what should we be focusing? because we want to set the right expectation. It is early days. It's a dose escalation. But also, it seems the messaging is pretty encouraging. You've been talking with the street. This is that you want to widen the therapy window. You want to address the safety issue while maybe you are trying to achieve the endotumor activity even beyond the cervical. So give us some high level, and then we can ask some more questions.

Jane Chang, CEO

Yeah, so our Tissue Factor ADC is designed, it's a beta-glued DART-8 Exatecan payload ADC. How we're designing our ADCs is fundamentally different. We are trying to optimize both for efficacy as well as safety. And I think many ADC companies have moved to the topo payload class as sort of the next generation payload, but they're also designing for safety. They're choosing, like, lower potent Exa-T cans, like a Derex-T can or a Bella-T can, or taking the DAR from DAR-8 down to DAR-6 or DAR-4. When you design only for safety, primarily, you're actually leaving efficacy on the table. Sutro, we've selected the most potent payload of Exa-T cans and keep it at the DAR-8. Even with our dual payloads, we're going up to DAR-10 with PTK-7, and even with the ATR combinations, we're going up to DAR-16 and possibly DAR-24. So we're going in the opposite direction. And the reason we believe we can do that is because we've actually achieved highest non-severe toxic doses at a very high level for even our tissue factor program at 50 milligrams per kilogram, even on a single payload basis. So this is higher than what conventional ADCs have achieved. And so if we can strike the right balance of delivering more payload, more potency, and at the same time delivering more safety, this is how we believe we can maximize or widen that TI, right? And so with tissue factor, we've made a lot of improvements from our first-generation program we had before. We have moved to the more potent exotekin payload, kept it at ADAR. We've improved the linker strategy with a beta-glucuronidase linker that has been modified for our cell-free system. So it's not something that you can cut and paste and put into a CHO-based manufacturing system. We have made our optimization with click chemistry with our non-natural amino acids that is highly stable, but it cleaves more in the tumor and less so outside the tumor. And that leads to a better safety profile, leading to a lot less platform toxicity. In addition to that, our antibodies are made in a cell-free system, so they don't have the cell membrane. They're not glycosylated. They're not sugarized. And so they don't engage with FC gamma receptors that are in the lung or in the eye. And, again, improving the safety of our antibody that we make for the ADC. So, again, we're dialing up the safety, but we're also dialing up the potency. And this is why we believe that we can meaningfully differentiate the benefit to patients with this kind of design features.

Roger Song, Analyst — Jefferies

Okay, right. So you try to achieve both ends. So that's a big mission to achieve, but, you know, you may be able to do that. So maybe on the safety side, so maybe tell us about the dose level you are right now, which is already very impressive. And then how should we think about the safety profile compared to the first-gen tissue factor and maybe also the topo-1 or exotecan at the payload? How are you going to address, you know, kind of a compare benchmark topo-send?

Jane Chang, CEO

Yeah, so compared to the approved tissue factor program, which has a – it's TIBDAC. It's a tissue factor ADC approved in cervical cancer. They have an HNSCD of 3 milligrams per kilogram. The Stroh IV program we're developing for tissue factor has a HNSCD of 50 milligrams per kilogram. We have changed the payload from a tubulin payload to a topo payload. We have optimized our linker strategy from a valsit-val-ala linker to a beta-glucuronidase linker. We have made our antibodies in a cell-free platform, which does not in and of itself engage with FC gamma receptors. And so we know, looking at the BLA for the TIVDAC program, that the antibody alone, this is Tisodamab, actually can contribute to some of the ocular toxicity. And so in terms of enrollment, where we are for the phase one trial, we have already shared that we have cleared and completed dose level three back in February and March. We continue to escalate, and we're ahead of projections in terms of execution. We'll share more later this year, and maybe, Jonathan, you want to share how it's going on the trial?

Jonathan, Analyst — Other

Yeah, thanks. Thanks, Jane. The trial has proceeded faster than we expected. We're ahead of schedule, and I think that's in no small part due to the investigators having their confidence built by a very, very strong preclinical package. Jane's mentioned that the HNSTD was 50 milligrams per kilogram, and to come back to something that Roger mentioned you know about anticipated safety what we didn't see in the GLP tox study were any of the expected toxicities associated with TivDac so while we obviously it will be foolish to ignore the experience of TivDac and not monitor for bleeding eye events etc we actually didn't observe those in the in the GLP tox study and I think the investigators you know read into that that this is a you know a very well-designed drug which is you know has been as well prepared as it's possible to get a new asset into the clinic. And so when their confidence is up, they get enthusiastic about enrolling. So that keeps the study moving at a high pace. And I think the media data readout that Jane will talk about will be compelling, we hope.

Jane Chang, CEO

But I do want to say that these are, tissue factor is expressed in normal tissue. So if you go really high on the drug exposure, you're likely to see that. but again it's the benefit risk ratio that we're looking for and if you're able to really dial up the drug exposure in a much more powerful way and deliver more drug and more potency then you have to evaluate the opportunity I would also say the the momentum that we have in our phase one trial has been very strong and the fact that we're continuing to escalate and we are moving at the pace that we are and had committed to actually getting to data you know mid-year you You know, and getting there, like, we only started this trial in December, so it's only a few months before. And so being able to execute this way can almost suggest that you're not running into the DLTs that's stopping you from escalating, right? So there's definitely momentum and excitement around this program.

Roger Song, Analyst — Jefferies

Yeah, I totally echo that. So as you do the phase one, those escalations, typically those trials are going to wait a year or something to read out, and then you commit it very early on, right? So you say, mid-year, we're going to have data, and it's still kind of confirming that. So that's very encouraging, which, you know, totally agree means you don't have any stopping and then also kind of progress very rapidly. So maybe just stay on that point. So in terms of the mid-year update, how much the robustness of the data we're going to see in terms of the end, those level, tumor type, right? So I think a couple of things that you can give us some color.

Jane Chang, CEO

I think for any dose-finding trial, the primary goal is to see if we have a drug that works and how to understand the data that we're seeing in context, right? So we're going very quickly. Obviously, there's several different dose levels that we're going to study here. And getting to a good look of data so that we could have some good understanding of the safety of the human PK parameters, What is the optimal sort of drug exposure needed in the humans? We have a lot of elegant preclinical work. How does that correlate? And then any early activity that we see across different tumors will be very encouraging for us at this point. Because, again, I think the whole strategy in this tissue factor ADC program is to deliver greater benefit beyond cervical cancer. We know cervical cancer is a high unmet need, but the opportunity may be shrinking given sort of the vaccine and the developments and advancements made there. So if we can, and we've seen some programs actually show some data in other tumor types with this approach. And so it's very encouraging for the field. And I think at this juncture, depending on how high we're able to deliver on the dose, any activity in other tumor types will be very, very encouraging for the program. And also how high we're able to actually get the drug exposure. I think that is also an indication for TI, right? So we're excited to see the data progress.

Roger Song, Analyst — Jefferies

Yeah, and then we know you cleared the dose level 3, February, March, and moving to the level 4. And then you start with 1 milligram per kilogram?

Jane Chang, CEO

We did start with 1 milligram per kilogram. It's interesting. There are other tissue factor programs that have just revealed their data. We know Tibdex started at 0.3 milligram per kilogram. Eva Point's data that was highlighted at ASCO, they started at 0.6. And we started at one milligram per kilogram, which I don't think should be under-recognized, if you will. This is a new platform with a new linker payload system. And we had no questions from the FDA to start at that higher dose, despite tissue factor being expressed on normal tissue.

Roger Song, Analyst — Jefferies

Got it. But you didn't say what's the dose level 2 or 3 or the plan that highest the dose?

Jonathan, Analyst — Other

Jonathan, do you want to take that? As before, no. I tried. I know. That's good, Roger. But I will say it's a pretty solid dose escalation. And, you know, you aim for your top level in dose escalation to be often aspirational. So we're making strong progress.

Roger Song, Analyst — Jefferies

And then in terms of the protocol, it's a 3 plus 3 dose escalation. But also, okay. So tell me, what's the protocol, backfill, and then?

Jonathan, Analyst — Other

Okay. So, I mean, just to cover the dose escalation, it's not a three plus three. It's a Bayesian design-modified TPI, and the significance of that is it gives you a flexibility over enrollment numbers, so, in fact, you can push the numbers up. And the second thing is the FDA have given clear guidance that they approve of backfill cohorts because it allows you to build out your safety and tolerability profile at relevant doses so that you don't get sort of surprised later on by some new event because of insufficient numbers. So, you know, because the way you're going with this, Roger, is how many patients in the mid-year update? Okay, so it's not a 3 plus 3, so that means it's going to be more than 12 patients. But, you know, even our heroic investigators couldn't enroll 100 by mid-year. But it'll be a number somewhere between that very wide range, which I know causes some irritation. But, you know, we can't, again, for competitive reasons, we can't reveal exactly how many patients we're going to have mid-year. But I think, as I said before, Jane wouldn't have said it, that we're going to have a mid-year data release unless we plan to make the data compelling, you know, something that people can buy into.

Roger Song, Analyst — Jefferies

Got it. And then the incident, because we saw, you know, you mentioned a couple of TIFDAQ and then some other, you know, tissue factor, ADC, we can talk about that later. But in terms of dose level, it seems they are getting to two or three level. they kind of become even like approved the dose, the pivot of the dose. So how do you think about, because the potency is a lot higher for O4, how do you think about the therapeutic level? Is this one potentially can be the therapeutic level, or it's kind of later?

Jonathan, Analyst — Other

I mean, the PK from the animal studies told us that we're delivering highly potent drug with very limited, unscheduled release of payload into the circulation. And that is certainly the cornerstone of reducing platform toxicity. And so, again, that comes back to all the design features that Jane mentioned. And so, you know, we anticipate that the platform tox question will be answered early on with Stroh 4. And that, of course, will have a read-through into the whole rest of the program because the beta-glue linker is the sort of, it is, you know, if you like, our secret sauce to some extent. So that's an important feature. So we'll be very much looking forward to sharing PK data in the mid-year data release along with safety. And as Jane said, you know, we're already looking for activity because every patient coming into the dose escalation has to have measurable disease. I will just, before handing it back to Jane and Roger, I will just also add that remember that the data we'll be releasing mid-year is an entirely U.S. study. So you won't have to sort of weigh up, well, what does this mean, translating a China study into the West? This is a study performed in the West, and so the data will be very easily intelligible to the Western investor audience.

Jane Chang, CEO

And just to add here, the one milligram dose that we looked in the preclinical work was a very active dose. But that said, you know, I think we have in our phase one program heavily treated patients, right? So you have to see whether or not that translates into that kind of patient population. So any activity that we see would be very encouraging, even at those low doses.

Roger Song, Analyst — Jefferies

Yeah, so we'll come back to this expectation in terms of antitumor. Like I said very early on, we need to set the right expectation, right? So we can summarize everything we discussed later. And then in terms of the tumor type, we understand it's a phase one dose escalation. Like Jane said, it's heavily pretreated. And then the tissue factor approved in cervical, which probably makes sense for people to understand this co-work. And then you have like seven or six other tumor types. And then how should we think about those tumor types potentially will be aimed more in the trial? Because we see the PDAC, we have some head and neck in the past. And I think TBAC in the early day, I think we look at the phase one. It's kind of a 6, 7 tumor types. So it seems these are all widely expressed. But in your trial, how much you can say at this point in the tumor type distribution?

Jane Chang, CEO

So maybe I'll start and hand it to you, Jonathan, about the kinds of patients we're seeing in the phase 1. I would say that the approved TIB-DAC program achieved in their phase 1 program, if we harken back to what's an apples-to-apples comparison, if you will, not that this is what we see as the benchmark, but this is just a comparator. But when they first started their trial in phase one, they achieved one PR in 27 patients, and that PR was in cervical cancer. Now, it took them two years to get there, and so we're committing to getting to data within six months or a quarter of the time, and we're looking at activity beyond cervical. So it should be very valuable for us to really understand what this program can do. In the trial, we have eight different tumors that we're looking at. Phase 1s tend to be more heavily enrolling on the PANC side of things and pancreatic as well as CRC just because of the limited treatment options they have in standard of care. That said, we'll have representation of all eight of them so far in the Phase 1, and it's just basically how many patients can we really analyze the data with. So I know everyone asks me, what's the benchmark? What's the ORR benchmark? But it's very hard to do when you have one or two patients within a cohort or within the study representing that tumor. So we have to see and understand the data in context of what we're seeing. You know, if we're seeing greater activity with higher dosing and greater exposure, that's a good thing. If we're seeing safety balanced on the dose exposure, that's also a very good thing. If we're seeing anti-tumor activity broadly, that's a good thing as well. So maybe you want to add to that, Jonathan?

Jonathan, Analyst — Other

Yeah, thanks, Jane. I mean, Roger, that basket of indications is wide, and I think that speaks to the fact that one of the problems in the ADC space is not the lack of targets. We have good targets, and tissue factor is an excellent example. All the tumor types in the basket of escalation could have a forward development path if we see signals. So, you know, I think that's, I want to underscore that. And we have got representation in those indications in the escalation study. As Jane said, you know, the heavy lifters in all phase one studies in the U.S. are pancreatic and CRC. But we are seeing the other tumor types as well. So, you know, this is important for us. And the other important thing is that, because people ask is, well, what about the tissue factor expression? We are collecting specimens. You know, it's an eligibility criterion to come into study that you have to have tissue available for analysis. And the reason for that is not that we're looking to make a companion diagnostic. Our premise is that by getting a high-DAR, high-potency payload ADC, that we can go after the lower expressors. And so, you know, we want to show that. And we need to do that by doing, at the back end, expression versus response. So we are collecting tissue, but we're anticipating strong activity at all levels of TF expression.

Roger Song, Analyst — Jefferies

Got it. Yeah, so I think we took a look at the same thing for TIBDAC early trial and then across different tumor types. And, you know, as you said, Jane, if the N is so small, honestly, we should not look at the individual tumor. Rather, it's a broad kind of, you know, kind of a look. and then if you have activity or tumor shrinkage, non-necessary response, then across all the tumor type, that can be encouraging in terms of the antitumor activity.

Jane Chang, CEO

Yeah, I think so. You're looking at directionally what you're seeing in the patient population that you're also looking at, right? We allow for up to 14 lines of therapy. So these patients are very heavily treated. I get it. Folks are focused on an ORR bar from other cohorts. cohorts. And that's easier to do when you have a specific indication and you have like 30 or 40 patients you're looking at in maybe a very specific line of therapy, whether it's second line or third line. But we have potentially up to four or five or six lines of therapy that patients would be treated. So it's very hard to understand what is the true benchmark. That being said, we're being very thoughtful about the data that we're seeing not only in the past with TIBDAC, but also emerging tissue factor programs, and so we will be making sure that we can deliver on a competitive profile. We're looking also on whether, you know, the study, the drug is worth continuing to develop. That is the central question for us, and we have three programs going into the clinic. We have to manage our investments moving forward, and so, so far, we have not seen anything to tell us that it's not something we should do.

Roger Song, Analyst — Jefferies

Excellent. I think that's a perfect kind to wrap up the all four is this is the first look, right? But you also want to make this readout meaningful, which can inform your next step. So what would be considered as an overall profile? You think that's good, investors, and also yourself, and then say, okay, we should move forward, and then what would be the next step? Maybe that's a follow-up.

Jonathan, Analyst — Other

I mean, to amplify Jane's point, you know, when you do a phase one study, until you have the patients in and look at their data, you don't really have their profiles fully worked out. So, you know, we need to sort of pass the data very carefully to understand what we're getting. And, you know, a very obvious point is prior orinatecan exposure, which we've seen, I think, heavily influence the EVO point data. So we need to understand all that, and then we, you know, we need to demonstrate that the PK has performed as we expected it to from the GLP-TOX study. Remember that the antibody that we're using in STRO4 does cross-react with the SINNO, which I think lends weight to the GLP-TOX study, that it will be reflective of where we go in the human. But we need to confirm that, and then we need to, as Jane has alluded to, we need to confirm that we know we have succeeded in widening the therapeutic window. And that's important because always in oncology you treat to tox. You know, if the patient has no tox, then you're always wondering if you've left exposure on the table. You could have given more. You could have got more responses. But if the therapeutic window is wide, everybody gets treated to a dose that is known to have some incidence of tox. But knowing that when you do have to dose reduce, you can dose reduce to a level where you still have activity. So that's one of the benefits of the therapeutic window, is it allows more patients to benefit. Yes, some will get tox, but when you dose-reduce them, they're still getting a meaningful level of drug exposure. So that will be an important concept for us to confirm early on.

Jane Chang, CEO

We have one of the strongest scientific sort of preclinical work for this program. We looked at the PK. We looked at the HNSCD. We have done about 100 PDX models where we look at robust samples of PDX, not just, you know, models that are sensitive for a specific payload or whatnot. We're looking, we're taking a very scientific approach to this evaluation of this program. So far, the data tells is very encouraging for us, and we've even benchmarked our PDX to the competition. And we see things that are very correlative in the clinic. Now, we're excited to get to data so that we can actually correlate our early preclinical work to the clinical data. And if this does work, this is probably one of the most exciting things that we can be doing, because this methodology that we've introduced can actually de-risk every program in our pipeline. And this is very valuable because I know when folks go to different conferences, there's 300 posters on a new ADC. How do you tell the signal from the noise? You have to take a very scientific, realistic approach on what a drug can do. And when you look at the parameters of objective PK, when you look at the HNSCD, which we have been very transparent on all of our data, and you do the kind of PDX modeling where we look at a robust sample, but we give one dose of a clinically relevant dose as opposed to 15 milligrams or 20 milligrams, which can show that any drug works in a PDX model, we're not trying to fool ourselves. And so really we are excited to see whether we can actually translate this into the clinic, and it will be powerful for not only Stroh 4 but Stroh 6 and 227.

Roger Song, Analyst — Jefferies

excellent already i think uh we talked enough about all four we just look forward to the data i think uh you will deliver uh what you want to achieve and you already told us so far nothing really prevents you to continue the development and i think uh we uh we feel your confidence okay uh and then maybe just the last minute in terms of you know uh financially where's sutra at and then you also alluded earlier so you have a a slew of the the pipeline based on the same platform right i think you know how much more and you want to tell and then use them in l2

Jane Chang, CEO

so with our recent raise of 110 million earlier this year that now affords us to actually study all three programs stroke four stroke six and two to seven and getting into the clinic and getting to poc this is very important and valuable for us having multiple programs getting into the clinic to validate the science and the technology. Prior to the raise, we were really looking at stroke four. All eyes are on stroke four for everything, but now we have the money and the funding to do that, and we have the cash out to Q2 of 2028, and so this affords us to do great

Roger Song, Analyst — Jefferies

Excellent. Thank you, Jane. Thank you, everyone. listening and watching.