Your biotech analyst here at RBC Capital Markets. Our next presenting company is Pliant Therapeutics, represented by the President and CEO, Bernard Coulie. Bernard, thanks again for being here.
Thank you. Thanks for having us.
Maybe let's kick things off on 095. You guys had updated the dose escalation data recently at the AACR conference. Can you maybe talk a little bit about maybe the program overall and what you guys are seeing with regards to longer follow-up and responses in patients still on treatment that has, I guess, continued to foster your enthusiasm around the program?
Yeah, absolutely. 101095 is a small molecule, twice-daily dosing, oral. It's a integrin blocker, alpha-v beta-8, beta-1, two key integrins in the tumor microenvironment. Alpha-v beta-8 is expressed on both tumor cells as well as inflammatory cells, and alpha-v beta-1 is expressed on CAFs. The idea behind or the hypothesis behind the program is blocking TGF-beta, in terms of converting from latent to active or even blocking the interaction between TGF-beta and its receptor, because TGF-beta is thought to be a key driver of immune exclusion in these tumors, in response to checkpoint inhibitors. The first kind of hypothesis is, like, by blocking the conversion of TGF-beta, we will resensitize refractory tumors. Tumors, I mean, refractory to checkpoint inhibitors.
The initial data set in December, which was a very small phase I-A, 16 patients in total, five different dose cohorts. We started to see from the mid dose on, we started to see interesting responders. We had four out of 13 patients that had a response. One was a complete, two were, three were partial responders. At that time, median duration of response was 15 months. Average tumor reduction in terms of size was around 70%, if I remember well. What was even more interesting was that the design of the study is such that you give 14 days of monotherapy with a small molecule, followed by a re-challenge with an ICI, KEYTRUDA in our case.
What we saw was that after 14 days with just our drug, in the responders only, we saw this surge of interferon gamma. It went up anywhere between three and 12x versus baseline over a very short period of time. The complete responder, which is a cholangiocarcinoma, which went through five lines of therapy and was progressing, actually had the 12x surge of interferon gamma. At AACR, we presented an update of this study. I mean, by the way, the drug is well-tolerated. It's rather, I mean, safe. We didn't see any major side effects except rash in about 40% of patients, which was mild to moderate. The updated AACR that was given by Tim Yap, Doctor Yap at MD Anderson, from MD Anderson . In the meantime, the average duration has increased to 19 months. Actually, the cholangiocarcinoma patient has passed 24 months now.
Wow.
It's two years complete response for a cholangio patient. You know, I think average PFS is less than three months, right? The second patient is a melanoma patient. That patient has passed, I think, 80 weeks now. The third non-small cell was a, turned out, and this was also an update at AACR, was actually a complete responder in the target lesion, but a confirmed partial responder in a non-target bone lesion. Now, we never did a PET login, a PET study to see if that was actually a true met or not. Which is unfortunate, but it's what it is. That patient started to progress after week 58, so that's not a responder anymore. And again, safety, same. Very, very promising data. I think based on that, we decided to start our phase I-B study.
Let's talk about the phase I-B a little bit more, the dose expansion cohort combo with pembrolizumab following the 14-day monotherapy run, and just maybe the rationale for going after, ccRCC, TMB high, tumors, a non-small cell. Just how you guys sort of thought about the optimization of the dosing and the dose levels and indications.
Yeah. Maybe starting with the dose. The dose we're going to use in our phase I-B that's actually ongoing. First patient was announced a couple of weeks ago. In the meantime, we have additional patients that were enrolled. The dose we're going to move forward, at least in this phase I-B, is 1 g twice daily. A 1,000 mg twice daily. That was the dose at which we started to see the effect in our phase I-A. We only had three patients at the lower doses, 250 mg twice daily and 500 mg twice daily. It was a rapid dose escalation. Moving forward, the mid dose from our phase I-A will be the selected dose for the phase I-B.
The rationale behind choosing the different cohorts, non-small cell, out of the three patients that were enrolled in the first part.
Yeah.
Of the study, where they were not non-small cell lung cancer patients, one never got into the combination because it didn't go through DLT period. The two ones that went into a combo, one of which was a complete responder in a target lesion, and the other one was actually at the lowest dose, a primary refractory, had stable disease and never responded to ICIs before. There is kind of a, I would say, hypothesis that these kind of patients may be more susceptible to our approach. That's the reason to use non-small cell. It's both TMB high and TMB, non-TMB high for the non-small cell, ratio of about 60% to 40%. For the second cohort, that's renal cell carcinoma. This is a prototype tumor for us that has a highly inflamed TME.
Okay.
The tumor microenvironment. It could be a prototype for HCC, head and neck. That's the reason to kind of choose that one, because that's where we feel that a TGF beta based approach makes a lot of sense. On top of that, Scholar Rock published actually data with their TGF beta, latent TGF beta stabilizing approach, which is an antibody with an ORR of, I think, 25%, if I remember well, in renal cell carcinoma. There is definitely evidence that TIGIT beta may be relevant for that type of tumor. The third one is TMB high, right?
Yeah.
We saw three out of four responders in our phase I were TMB high patients. We're going for a TMB high cohort as well, which includes melanoma, colorectal, urothelial, endometrial, and of course, biliary tract. Cholangiocarcinoma seems to be.
Yeah
A very interesting one that we want to pursue.
When might we see some initial data from these dose expansion, these indications?
I mean, starting 2027. I mean, it's hard to pinpoint a month because let's see how fast it goes and, you know, if patients stay on treatment. Again, it's 14 days of run-in and monotherapy, and then scans every nine weeks. The re-challenge with the ICI happens after, at day 14. First patient is in, so I hope to see data starting in the, in the spring of 2027.
What do you think are the most important elements for discerning 095's monotherapy contribution to activity? Is it the dose dependence that you're seeing? Is it the interferon gamma spike that you wouldn't otherwise see? Are there, is it too early to benchmark the response rates you're seeing versus what you would expect with pembro alone? I guess, would, what drives the most confidence?
Yeah, I mean, the ORR is to kind of compare that with historical ORR is a little bit tricky.
Yeah.
Because the sample size is so small, and it's a little bit all over the place as it relates to indications, right?
Right
I mean, we have a bar, and we can discuss it. You know, what is the efficacy bar that we want to reach? Coming back to the phase I think the one, maybe two components that I think really provided us the conviction that this, you know, made it convincing that this is kind of really working on its own, I mean, it's triggering the effect, and it's not just a re-challenge of the immune checkpoint inhibitor, is the interferon gamma, to your point. I mean, that's a one-to-one correlation in terms of a surge in interferon gamma and a response. The second one is the durability. I mean, the fact that you have a cholangiocarcinoma patient who has passed 24 months now that was progressing-
Good
Always progressing. That's not what, no.
Yeah. Okay.
That's not what you would expect.
Okay.
I think that those are two components. The overall ORR was 30%. DCR, 60%. Those are very good numbers, but a small sample set.
Yeah.
What we haven't published and haven't publicly disclosed are ctDNA levels. We have those for the four responders, and to say the least, they're very interesting. There may be something there as well, and this is something that we will measure in our phase I-B. Coming back to the phase I-B, coming back to your question, how sure you will you be about the effect of the drug itself? It will be the monotherapy 14 days that will learn us a lot in terms of all the different biomarkers we're going to measure. Of course, we're going to do tumor biopsies as well at start and then couple of weeks into treatment, because that will help us also to understand which patients are responding from a, you know, tumor microenvironment perspective.
Okay. Then maybe just a question or two more on 095, and I want to leave some time for the platform as well.
Yeah.
Could you envision this being used in patients primarily with increased alpha-v beta-8 expression? Or do you think that just the expression of alpha-v beta-8 is sufficiently broad that you wouldn't necessarily be narrowing the eligible population anymore in the
I mean, it's an excellent question. I think the answer will be, let's see what the data, the biopsy data are telling us. Alpha-v beta-8 is constitutively expressed on T cells, on T lymphocytes, on activated T lymphocytes. Probably most patients have alpha-v beta-8 in their tumor microenvironment. The question is, what is the relative contribution of that compartment to the overall effect of our drug? Alpha-v beta-8 is also expressed on tumor cells.
Right.
We will learn much more about that. That is not necessarily correlated.
Yeah
If it's expressed on inflammatory cells, will it be expressed on tumor cells as well? We don't know. There is alpha-v beta-1, which may be an interesting contributor to the overall effect as well.
We know that there are other programs that have been pursued or still being pursued with an antibody against alpha-v beta-8. In some cases, not a lot of result. In one case, of which we know, probably a very, you know, very severe toxicity related to rash. Then we are aware, and it's not in the public domain, that Genentech is moving forward with their alpha-v beta-8 antibody program as well, and that's earlier stage compared to ours.
You guys have been really on the forefront of the integrin pathway for multiple indications. Obviously, things didn't work out in IPF necessarily, but there's been a lot of now advances that you guys are on the cutting edge on in cancer. I know there's also ways you can leverage the platform for elements of drug delivery of siRNAs. Can you talk a little bit about where you guys stand with regards to some of the preclinical studies you're doing to that effect and where you see this being differentiated versus kind of the other targeting delivery systems out there for siRNA?
Over the 10 years of our existence, we have built, I think, an unmatched small molecule library of integrin targets. I mean, targeting, small molecules. Basically, that library is about 15,000 compounds, I think, is completely annotated, so we know exactly the receptor profile of each of those small molecules. Of course, seeing what was happening in the space of delivery, drug delivery, whether it's siRNA or, you know, like ADCs or what have you, integrins are a target that people are pursuing and are looking at. We decided to kind of see if we could do the same with a small molecule approach, because all the other approaches are antibody-based or peptide-based. The advantages of a small molecule, I think, are pretty obvious, but we can go through that.
In any case, what we did was we started basically labeling a whole bunch of small molecules with a siRNA that knocks down a healthy gene, and then just inject it in mice, and then just harvest all the tissues, and then look where do we have knockdown. That's how we started to see the differences between the different profiles and the selectivity of certain compounds and maybe not so selective of other compounds. What we are doing today is moving forward with some of those individual molecules with specific target genes that are relevant for certain indications. Our initial work was done in muscle. It's an easy target. We know what kind of target genes you're going after, and we have comparators. We have benchmarks like Sarepta, for example, or the transferrin receptor antibody approach. We did it in adipocytes.
It works as well. Whether that's an indication we want to pursue, I'm not sure. We see it in kidney, and now we start seeing it. We have done it in lung as well because alpha-v beta-6 is a typical epithelial lung target. Alpha-v beta-1 is a fibroblast target, so that could be a potential target, you know, cell as well. Now we start to also evaluate what is considered as intractable targets or intractable, sorry, tissues that with standard siRNA delivery technologies you cannot reach. We start to explore whether that would make sense for us as well.
What's the status of the preclinical data package now at this point, and what are your latest thoughts about when we might see an update there? Is that something we could see this year, and what would be the initial scope when you do report out some of these findings?
Yeah. The muscle program is the furthest advanced. That's currently in non-human primate testing stage. Looking at PK/PD, local delivery, target gene knockdown, circulating biomarkers, what have you. We haven't disclosed the target in terms of the integrin that we are using or integrins. We haven't disclosed the target gene as it relates to the muscle itself. That will follow.
Yeah.
Most aggressive timeline could be an IND by the end of 2027, early 2028, if that's the one we want to pursue. Of course, again, it's crowded. The other, you know, platform development, tissue-specific platform development, or I would say most of them are mouse stage right now. We anticipate we'll go to non-human primates later this year or early next year. From a data disclosure perspective, we anticipate to disclose data this year. What the scope of that data set will be needs to be determined.
Okay.
Because the question will be, you know, is this just a data set without any further context, or are we going to be a little bit more specific about indications that we want to pursue, et cetera.
Okay.
Right?
You sort of alluded to some of the potential advantages that a small molecule approach might have over a peptide-based approach. I guess, are there any read-throughs that you see from some of the alpha-v beta-6 targeting siRNA data from an FSHD and DM1 that Sarepta and Arrowhead re-reported? Maybe can you talk about where you see any potential advantages for a small molecule muscle targeting approach?
Yeah. I mean, the Sarepta data, I think, show that in their case, an alpha-v beta-6 targeting peptide actually works, right? It does deliver siRNA to the tissue. I mean, although they didn't do a head-to-head, they did show from a tissue concentration perspective that with their approach, even at, if I remember well, the mid dose, they see kind of a four-fold higher concentration of their siRNA. This is in the DUX4 patient population, compared to transferrin receptor antibody approaches that were published by Avidity before. It was a comparison based on historical data, not a, you know, head-to-head comparison. You know, I think it makes sense. They're using a peptide that is targeting alpha-v beta-6.
It's an RGD peptide. The head of the peptide is an RGD sequence, which binds to RGD binding integrins like alpha-v beta-6, but also alpha-v beta-1, beta-5, beta-3, and beta-8. Selectivity could be a challenge, the way to address that is adding more amino acids to the peptide.
Yeah
And trying to kind of make it more selective. The other, it's a bulky protein or a bulky molecule because they add this comes from the Arrowhead technology, they add lipids to it in order to increase its plasma exposure, its half-life. These PK enhancers, as they are called, are meant to increase plasma protein binding in order to prevent renal clearance.
Peptides and siRNA are renally cleared.
Yeah.
Our small molecules are metabolized in the liver. They're not renally cleared and have a high plasma protein binding and long half-life, notably once we go to higher species. We will show the mouse data at some point. Those are non-modified small molecules plus an siRNA with a linker in between. We know that the half-life of our small molecules in mice is anywhere between an hour and two hours. Still, three administrations, and we see months of knockdown.
It seems that exposure may not be the issue, and so our molecules can be much less bulky.
than the Sarepta approach, maybe leading to higher efficiency from a, you know, uptake perspective or an endocytosis perspective. I think it also potentially provides an advantage in terms of endosomal escape. Notably, subcu administration seems to be very feasible. I mean, these are highly soluble molecules, so I think that's I mean, it's an administration, whether that's a key advantage, I don't know. I want to go back to the platform. I mean, it's not just about the muscle versus Sarepta. It's actually about any other tissue-
Yeah
That we can deliver to, you know, with our, with our technology. Whether it's Sarepta or the transferrin approach, which are very non-selective. What we have seen i n mice is uptake in skeletal muscle and nothing in cardiac muscle, nothing in lung, nothing in liver, nothing in fat. Those, you know, we want to confirm that in monkeys as well. It seems that working with these different integrins, you are able to kind of dial in selectivity as you wish, which allows you to go after other target genes.
Right.
The way the transferrin approach is being made selective is by going for selective genes, myostatin, DUX4, that are specific.
Right.
We don't know what all this.
Selectivity you shouldn't need.
You can go after more.
Shouldn't require that.
You know, you can go after specific targets that are expressed somewhere else, you're not going to touch because you're not going to get into that cell. Ultimately, we don't really know what all this accumulation of siRNA in cells I mean, from a, there's not a lot of tox evidence except for transferrin receptor antibody approaches definitely have their safety, you know, safety issues, for sure.
Maybe just in the last few minutes, you guys have undergone such a transformation in the past few years. I guess, what would you, what would be your key takeaways for folks today looking at Pliant now for the next six, 12, 24 months as to what are going to be some of the key de-risking catalysts and maybe the key aspects of maturity of some of these new initiatives that seem to be gaining a lot of steam?
Yeah. I mean, first and foremost, two biggest assets we have is cash and people. I mean, obviously-
Yeah
We restructured the company to a very significant degree. I mean, we're very open about that. We were 170 + when we were in a pivotal IPF trial. We are about 40+ now. There is a significant reduction, but we kept the core development capability, which is something we have been always very, very good at.
Yeah.
We were able to enroll an IPF trial in record time. It was 200, sorry, 360 patients, and get to unfortunate data quickly, which allowed us to preserve cash.
Right.
Right? And so we have a core development team that will is already excelling as it relates to the, the oncology trial, and then we have that integrin platform. I think that's where we see our strength is really kind of we have enough cash, we have people, we can kind of make that pivot successfully. What is for the next 12 months, obviously, the oncology data will tell us a lot. I think it's extremely promising. If we could confirm what we have seen in phase I-A, I think this could be a very interesting asset. I know investors are a bit like, you know, IO again, you know, and a lot of people have been burned. I can tell you strategics do look at this differently.
Notably, the interferon gamma is a signal that everybody is focused on. The platform, right? I mean, this could be a game changer for the company. First, we need to confirm, and it's still two years from the clinic. That's still a lot of work to be done.
Long way.
It's a minimal investment right now because it's existing chemistry and then a linker, and siRNA is literally off the shelf these days.
Yeah.
You have excellent CDMOs that can make it for you. Running these monkey studies, I mean, it's a bit capital intensive, but it's not the same as running a clinical trial. Let's see where we get and then start to kind of identify what we consider as programs that will make us very competitive. I mean, going after Sarepta with another DUX4.
Right
We need to have a clear upside there if we want to do that. There may be other other things that we can go after.
Right.
I mean, catalyst in 2026, very much, you know, potentially these data, the siRNA data, and then 2027 will be catalyst rich because all those, you know, cohorts will be.
Yeah
Almost fully enrolled, and we will start to see a lot of data. I mean, the total number of patients is ultimately up to 106, if I remember well. It's 36 per cohort. 108, sorry. 108 patients in total.
Great. Excellent.
Thank you.
Thanks so much. Congrats on all the progress.
Appreciate you.
Thanks , Bernard. Thanks, everyone.
Thanks so much, Brian.