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Study Update 2023

Dec 18, 2023

Richard Aranda
CMO, Gossamer Bio

Good morning, ladies and gentlemen, and welcome to the Gossamer Bio TORREY OLE Update. I will now turn the call over to Bryan Giraudo.

Bryan Giraudo
CFO and COO, Gossamer Bio

Thank you, operator, and good morning. Thank you all for joining us as we go through this exciting update on the TORREY OLE data. Please note that certain information discussed on the call today is covered under the safe harbor provision of the Private Securities Litigation Reform Act. We caution listeners that during this call, Gossamer management will be making forward-looking statements. Actual results may differ materially from those stated or implied by these forward-looking statements due to the risks and uncertainties associated with the company's business. These looking statements are qualified by the statements contained in Gossamer's news releases and SEC filings, including in the annual report on Form 10-K and subsequent filings. This conference call also contains time-sensitive information that may be accurate for only a limited period of time.

Gossamer Bio undertakes no obligation to revise or update any forward-looking statements to reflect events or circumstances after the date of this conference call. Now, I'd like to turn it over to our Chairman, CEO, and Co-Founder, Faheem Hasnain. Faheem?

Faheem Hasnain
Chairman and CEO, Gossamer Bio

Yeah, thanks, Bryan. Hi, everyone, and thanks to all of you for joining us today to discuss the latest seralutinib clinical data from the ongoing TORREY open label extension study. Now, I have the honor of being joined today by my Gossamer colleagues, including Dr. Richard Aranda, our Chief Medical Officer; Dr. Rob Rescigno, our seralutinib Development Lead; Bryan Giraudo, who you've just heard from, our CFO and COO; and Bob Smith, our Chief Commercial Officer, who just recently joined us from Merck, where he was instrumental in leading the preparations for the sotatercept launch. We're just over a year removed from the disclosure of top-line data from the TORREY study, which motivated us to initiate the current PROSERA registrational Phase 3 study. Now, what struck us when.

was the concordance of the data with PVR, measures of right heart health via echo, improvements in biomarkers such as NT-proBNP, and functional improvements, especially in patients with more severe disease at baseline, all demonstrating the positive impact of seralutinib treatment. And equally important, these efficacy measures were complemented by a favorable safety and tolerability profile. So our enthusiasm for seralutinib has really only grown since then as we've discussed our results with the PAH community, including clinicians, patients, and their caregivers, and learned more about our data, including what we've observed in our open label extension study, where we continue to see long-term improvements in hemodynamics and six-minute walk distance in what is otherwise a progressive, fatal disease. We're excited to share this update with you today, and we hope you share in that excitement and that of the PAH community by the time we finish our call.

But first, I wanna talk about some key hires Gossamer has made to pivotal positions in the organization in the last few weeks. We recently announced the appointment of Dr. John Quisel to our board of directors. Dr. Quisel is the CEO of Disc Medicine, but prior to that, he was the Chief Business Officer of Acceleron. Dr. Quisel led the initiative to reacquire rights for sotatercept in PAH from BMS. And as many of you know, this ultimately led to the acquisition of Acceleron by Merck for over $11 billion in 2021. Dr. Quisel has a wealth of knowledge and experience in PAH that will be invaluable, and we're honored that he decided to join Gossamer in its mission to advance seralutinib to the treatment of PAH. Additionally, we're very excited to announce the arrival of Bob Smith as our Chief Commercial Officer.

Bob's experience as a commercial executive in PAH, marketing and sales is unrivaled. Speaking of Merck's acquisition of Acceleron and sotatercept, as I mentioned at the start, Bob was at Merck as the U.S. sotatercept national sales lead, leading preparations for the drug's highly anticipated commercial launch. Previously, Bob was the Senior Vice President of Sales and an executive leadership team member at Actelion, where he spent more than 11 years in various senior commercial leadership roles. As the principal sales leader, Bob managed all U.S. operations, including the launch of two blockbuster PAH drugs, Opsumit and Uptravi. These successful launches eventually paved the way for Johnson & Johnson to purchase Actelion and its PAH portfolios for $30 billion in 2017.

Bob's a fantastic addition to the Gossamer team, and it's truly a testament to the excitement of seralutinib in the PAH community that we continue to attract world-class talent to help us develop and bring seralutinib to the market. Now, with that, I'll now hand the call over to Dr. Richard Aranda, who will give you a quick reminder of what we observed in the TORREY study and how it informed the PROSERA Phase 3 design before we dive into the open label update. Richard?

Richard Aranda
CMO, Gossamer Bio

Thanks, Faheem. I would like to take a moment to review this slide, which illustrates the totality of the measures and dimensions of data generated to date on seralutinib's clinical effects. As you can see, we have generated and presented data on the efficacy of seralutinib on pulmonary vascular hemodynamics, right heart dimensions and function, improving six-minute walk distance as a measure of functional capacity in the more severe patients, and a possible measure of vascular reverse remodeling by measuring pulmonary vascular blood volume distribution by CT scan imaging. Just to comment on the CT image data, which showed increased vessel appearance compared to baseline in treated subjects versus placebo. This has been visually compelling to the clinical community and has demonstrated the potential role of seralutinib as a reverse remodeling therapy for PAH.

Last, but certainly not least, we have been very pleased with seralutinib's safety and tolerability profile. The data clearly support the intended safety profile of seralutinib as a rationally designed molecule to minimize many of the TKI liabilities through more selective kinase specificity, limited systemic exposure, and the inhaled route of administration through a dry powder inhaler. Now, to add to this list, we have the open-label extension experience out to 72 weeks, which extends our understanding of seralutinib's longer-term safety and efficacy profile. Before reviewing the open-label extension data, I want to turn to the PROSERA study, for which we are currently activating sites globally and enrolling patients. As a reminder, this study is a multinational, randomized, double-blind, placebo-controlled phase 3 clinical trial evaluating the efficacy and safety of inhaled seralutinib for the treatment of PAH. Participants are randomized one-to-one to receive 90 milligrams seralutinib BID or placebo.

The total sample size is 350 patients, with the primary endpoint of change from baseline and six-minute walk distance at week 24. A key secondary endpoint is time to clinical worsening. We also plan to have an open-label extension. The PROSERA study has incorporated key design elements learned from the results of the phase 2 TORREY study. First, to optimize for a treatment effect on the primary endpoint of six-minute walk distance in functional Class II and III patients, we are enriching for a sicker population than what was studied in TORREY by having inclusion criteria incorporating the REVEAL Lite 2 risk score and NT-proBNP. Second, we will extend and confirm the findings from our phase 2 FluidDA substudy in a larger cohort of patients by incorporating CT imaging at select PROSERA sites.

As previously mentioned, we were able to show that seralutinib resulted in a statistically significant improvement in the pulmonary vascular blood volume distribution, consistent with a reverse remodeling effect. We believe that this imaging approach could provide differentiating insights into a therapy, such as seralutinib, which targets the underlying disease process in PAH. Lastly, we are in the process of exploring the possibility of including Japan in our phase 3 program. Recently, the PMDA has provided guidance that a PK bridging study may no longer be required as a prerequisite step prior to incorporating Japanese patients in a global trial for rare disease indications. The intent is to facilitate the more rapid development and eventual regulatory approval for much-needed therapies for serious rare diseases. Given this change, we are actively pursuing including Japan in our phase 3 program, which could support approval in Japan.

Japan is the second-largest market for PAH medicines behind the United States. Now I will hand it over to Rob Rescigno, our clinical development lead for the program, to discuss the latest seralutinib open-label extension findings. Rob?

Robert Roscigno
SVP of Clinical Development, Gossamer Bio

Thanks, Richard. Good morning, everyone. I'll start with a brief overview of the design of the open-label extension and dataset we'll be reviewing. While the main objective of open-label extension studies is to gather additional information on the safety and tolerability with longer exposure, we specifically designed the TORREY OLE to also obtain hemodynamic data by right heart cath at week 72. This provided us with the opportunity to obtain data on a centrally read, objective hemodynamic measure at three time points: pre-baseline, week 24, and week 72. As of the data cut for this interim update, we will be summarizing the PVR data on a total of 52 subjects, consisting of 27 subjects who continued seralutinib and 25 subjects who switched from placebo to seralutinib. For those subjects that entered into the OLE, we will also share an interim update on six-minute walk results.

including an analysis of the data using the REVEAL Lite 2 risk score, given the enhanced efficacy observed in this patient population in TORREY and the enrichment strategy we are employing in PROSERA. Lastly, we will provide a summary of the emerging OLE safety profile. While we are excited to share this interim OLE update, we are saving some measures, including NT-proBNP, to present with the totality of the data next year at a major medical meeting, which will also give the opportunity for ongoing patients to reach week 72. So what have we observed to date? I'll highlight several of the key findings before diving into the data. First, we are excited to say that we continue to see a deepening of PVR improvement at week 72 in many of the patients.

While we were immensely pleased with the results seen after 24 weeks, we are thrilled to see that the drug has continued to show a durability of response beyond the blinded period, not just a maintenance effect. Additionally, with regards to our primary endpoint in Phase 3, we see continued improvement in 6-minute walk distance, both from baseline and from week 24. This response occurs across the overall population, and it is driven by the patients we are enriching for in the Phase 3. Those with REVEAL Lite 2 risk score greater than or equal to 5, who continue to see an enhanced effect while on seralutinib. Also importantly, seralutinib safety and tolerability profile continues to impress, which is in stark contrast to the experience with oral imatinib in the IMPRES OLE study, during which they observed some of their most challenging adverse events, including 6 brain bleeds.

The treatment-emergent adverse events from our open-label extension study are consistent with what was observed in the blinded portion of the TORREY study and have generally been mild and manageable. We even have one patient from our Phase 1b study who has remained on seralutinib for over three years. Remember, all currently approved therapies are vasodilators, and while these therapies help patients, longer-term data has not shown treatment durability. Additional therapies are required. What we are seeing today in these data supports the differentiated mechanism of seralutinib. So this slide summarizes the results of the 27 subjects in the OLE study that were initially randomized to seralutinib and continued to receive seralutinib in the OLE. A continued seralutinib group received active drug for a total of 72 weeks. Both Functional Class II and III patients were represented with a median baseline PVR of 620 dynes.

Consistent with the PVR reductions in the double-blind period, at week 24, there was a median reduction of 89 dynes. At week 72, there are several notable features of the OLE PVR data. First, there was a greater numeric median reduction in PVR of 149 dynes. Second, between weeks 24 and 72, there are an increase in proportion of subjects achieving greater percent reductions in PVR, with several patients achieving a 30% or greater reduction and even some patients achieving a reduction of 50% or more. Finally, we see these improvements in both Functional Class II and III patients. These OLE data are consistent with a therapeutic profile of a deepening response with longer time on treatment.

We believe this reflects the antiproliferative and anti-inflammatory mechanism of action of seralutinib, and it may be related to its reverse remodeling potential, as supported by our FluidDA CT imaging data. This next slide summarizes the results of the 25 subjects who received placebo during the double-blind period and switched to seralutinib at week 24. Both Functional Class II and III patients were also represented in this group. We saw a reduction in PVR as expected after 48 weeks on active drug, and the majority of patients, 72%, or 18 of 25, had improved PVRs from their baseline at week 72. In these placebo cross subjects, the magnitude of effect was less than what was observed in those subjects that received seralutinib during the double-blind and OLE.

This may be reflective of a known phenomenon documented in the PAH literature, describing a diminished magnitude of effect in placebo subjects who then receive active drug. Alternatively, greater reductions in PVR may still be observed with longer seralutinib treatment. Looking at six-minute walk data, we also see a continued trend of improved functional capacity at week 72. As mentioned earlier, in addition to the changes observed in the overall population, we are breaking out the effects seen in those with elevated risk at baseline, defined as those with a REVEAL Lite 2 score of 5 or greater. The top panel shows the results in for the continued seralutinib group. The overall population, represented by the light blue line, had an average improvement of 16 meters at week 24.

Those with elevated risk at baseline, represented by the orange line, showed an increased benefit at week 24, with a 42-meter improvement. At week 72, the overall population of continued seralutinib patients saw their mean change in 6-minute walk distance increase to 31 meters, doubling the effect from the blinded portion of the study. The elevated risk group saw their mean 6-minute walk change increase to 50 meters at week 72. The bottom panel shows the results for those patients switching from placebo to seralutinib. The change in 6-minute walk at week 24 from baseline was relatively flat in both groups. But once on therapy, their 6-minute walk distance increased, and as expected, the elevated risk group showed enhanced benefit.

Overall, these data are consistent with the continued improvement in PVR, and we are happy to see an enhanced effect in those patients with elevated risk, as those are the patients which we are enriching for in our phase 3 PROSERA study. On this slide, you can see the top treatment-emergent adverse events observed in the OLE population. Cough, which was the most frequently reported adverse event in the TORREY study and in line with other inhaled therapies, has diminished in the OLE as patients acclimate to both the drug and dry powder inhaler. The vast majority of patients are able to titrate up to and maintain the 90 milligram BID target dose. We believe our safety and tolerability profile is extremely attractive, especially in contrast to other PAH therapies. Importantly, we have observed to date, no additional major safety findings in the open-label extension period.

Given imatinib's precedent experience in the IMPRES study OLE, we interpret these findings as incredibly encouraging. Now, I will turn it over to our newest colleague, Bob Smith, Gossamer's Chief Commercial Officer, to discuss the PAH commercial market and the implications of seralutinib's potential profile further. Bob?

Bob Smith
Chief Commercial Officer, Gossamer Bio

Thank you, Rob, and hello, everyone. It's a pleasure to be here with you today. As Rob said, my name is Bob Smith. I am Gossamer's Chief Commercial Officer, and today I'm excited to talk to you about seralutinib and the role we hope it will play in the treatment of PAH. Now, to set the stage, it is important to remind everyone about the current treatment landscape in PAH. As you can see on this slide, as you're aware, and as Rob referenced, the currently approved therapies are vasodilators and work on three different pathways, which we're all familiar with, endothelin, nitric oxide, and prostacyclin.

Upfront combination therapy with ERAs and PDE5s, as demonstrated in the AMBITION study, is the standard of care in PAH for newly diagnosed patients that are low or in intermediate risk based on the three-strata model risk assessment, that's been published in guidelines. Depending on follow-up clinical assessment, physicians generally add or substitute therapies to find each individual patient's right therapeutic regimen. Physicians are quick to escalate therapy to target the third or prostacyclin pathway, since PAH is aggressive, progressive, fatal, and has a deteriorating quality of life. It is important to acknowledge the challenges associated with current therapies, particularly the third-line therapy, again, the therapeutics targeting the prostacyclin pathway. These therapies have shown clinical benefit but are complex to dose and may cause dose-limiting side effects.

The delivery systems for prostacyclins, such as the need for an infusion pump and permanent tunneled catheter, or dealing with subcutaneous infusion site inflammation and pain, present additional difficulties. And while the Tyvaso dry powder inhaler is another much-needed treatment, four times daily administration is far from ideal for a patient who is already juggling multiple medications. Likewise, lugging a nebulizer around, such as used with the original inhaled Tyvaso, is not an option for a lot of patients. For those patients who opt for oral prostanoids, side effects can be problematic. Common side effects include a lot of GI problems, such as nausea, vomiting, and diarrhea. There's headache associated. Nervousness, anxiety, jaw pain, leg pain, and flushing are common prostanoid side effects. Adverse events are frequently severe enough to prevent patients from reaching an efficacious dose during uptitration, and medication discontinuation is common.

These challenges underscore the need for continued innovation and development of new therapies that can improve patient outcomes while minimizing side effects and enhancing tolerability. Contrast that to the data you've seen here today from seralutinib. Seralutinib has the potential to address these common challenges in the practical application of PAH patient care. Seralutinib is convenient, requiring twice-a-day dosing, excuse me, and it uses an existing, currently on the market, 2-inch dry powder inhaler device, which easily slips into a pocket or a purse. And patients are generally able to titrate up to 90 milligrams twice a day without issue. Couple this convenience and tolerability with an attractive safety profile, deepening of response with long-term usage, and a novel mechanism of action. What you get is a potential blockbuster PAH therapy that is differentiated and has the potential to be added early to the current standard of care.

This is exactly why I was so excited to join the Gossamer team. We have the opportunity to change the treatment paradigm in PAH with a therapeutic that we believe can change patients' lives. Thank you, and now I'd like to hand the call back to Faheem. Faheem?

Faheem Hasnain
Chairman and CEO, Gossamer Bio

Yeah, thanks, Bob, and thank you to everyone who joined us here today. As you can tell, we're very excited about the prospect of seralutinib to treat patients with pulmonary hypertension. At this point in time, operator, please go ahead and open the call to Q&A.

Operator

Absolutely. At this time, ladies and gentlemen, please press star one on your telephone keypad if you would like to ask a question. That is star one on your telephone keypad if you would like to ask a question, and I'll allow just a moment for the queue. Great, thanks, everyone in queue. I'm going to go with our first. Looks like Yasmeen Rahimi, your line is now open.

Lauren Timmons
Managing Director Senior Research Analyst Biotechnology, Piper Sandler

Hey, team, this is Lauren Timmons on for Yas. Congrats on the data. Really exciting to see. The first question we want to ask is around the first OLE cohort back in July compared with this updated one. Could you talk a little bit about how the data compares between the two cohorts? Thanks.

Faheem Hasnain
Chairman and CEO, Gossamer Bio

Sure. Richard, Rob, do you want to handle that?

Richard Aranda
CMO, Gossamer Bio

Yeah, I can start off. Well, the first cohort, if you recall, we presented, I believe it was around 30, 32 or so patients, and that was the cohort by PVR measures, was less severe. As you recall, the first cohort was really enrolled, you know, at the time of the pandemic, I mean, the whole study was, there was the Delta variant in between the enrollment of the first and second cohort. So the second cohort tended to be a little bit more severe patients than the first cohort.

I think at the end of the day, because we included both Functional Class II and III patients, and we were able to demonstrate that the reduction in PVR can be demonstrated both in what we would consider the less severe Functional Class II, as well as the more severe Functional Class III.

Lauren Timmons
Managing Director Senior Research Analyst Biotechnology, Piper Sandler

Okay. Thanks, guys.

Bob Smith
Chief Commercial Officer, Gossamer Bio

I'd also add that again, you had a significant delta in the baseline baseline pre delta versus post delta. And that was also demonstrated by not only a greater impact on PVR, but also if you compare and contrast the six-minute walk totals when you combine both data sets, you see a deepening of effect there as well. So again, while we were very, very pleased to see the significant impact on that first cohort, a healthier patient population, as expected, we were able to see even more movement with more sick patients, which we think portends well for the PROSERA phase 3 study.

Lauren Timmons
Managing Director Senior Research Analyst Biotechnology, Piper Sandler

Perfect. Thank you so much for the color.

Operator

All right, next up, we have Joseph Schwartz. Joseph, your line is now open.

Joseph Schwartz
Managing Director and Senior Equity Research Analyst, Leerink Partners

Great. Thanks very much for the update and for taking the question. I was wondering first if you could talk about whether you envision seralutinib will be used mostly as an incremental add-on to background therapy, or will it be swapped in for something that might be swapped out in many cases? Did background therapy change at all for any patients in the TORREY OLE, and are you controlling for that sort of behavior in PROSERA?

Faheem Hasnain
Chairman and CEO, Gossamer Bio

Yeah. Thanks, Bob. Thanks, Joe. Bob, do you want to take a crack at that? And Richard, maybe you can comment on the background med piece?

Bob Smith
Chief Commercial Officer, Gossamer Bio

Yeah. In terms of positioning, I can do that. And as you know, in the studies, seralutinib was added to standard of care background therapy, be it PDE5, ERA and/or prostacyclin agents. And speaking and talking to many of the PH experts out there, it appears that seralutinib will be positioned in most cases, particularly for kind of that low intermediate patient population, risk population, as an add-on to the PDE5 and ERA, earlier in the treatment paradigm, due to you know the unique mechanism and the ability of the reverse remodeling. So that's where we expect the positioning, at least the feedback as I've talked to these KOL over the past several months to position seralutinib in the treatment paradigm.

Richard, if you want to address the study.

Richard Aranda
CMO, Gossamer Bio

Yeah. So, Joe, during the open-label extension, we did have a couple of patients that adjusted some of their background therapies, but other than that, there was no additional PH medications added that accounts for the deepening response.

Faheem Hasnain
Chairman and CEO, Gossamer Bio

I'll add, Joe, you know, by the time we get to market with seralutinib, there's gonna be a significant number of patients that are looking for the next treatment. Obviously, sotatercept will come in ahead. There'll be a number of patients that will respond quite well, but studies show that it'll probably be around the 30% mark. So there's gonna be a significant number of patients that are warehoused waiting for another agent, because none of these things are cures.

And then from there, we would suspect that not only will a significant portion of patients want to try this and be added onto their therapy, which might give the opportunity to push out prostacyclins a little bit longer, but over time, agents like seralutinib, being a reverse remodeling agent, physicians are gonna want to try these agents early to prevent longer term progression. And then for the patients that are further evolved in their disease, they're also going to want to use them to reduce the risk of mortality. Again, none of these agents are cures. This is a progressive disease. So we fundamentally think that kind of patients on both sides of the spectrum are gonna be really reaching for, for agents like, seralutinib and sotatercept, quite frankly, to try to prolong their, their and, and push out the progression.

Joseph Schwartz
Managing Director and Senior Equity Research Analyst, Leerink Partners

Thank you. My next question is on Japan. When will you know whether you can include patients from there in PROSERA, and how could that impact the enrollment rate and market opportunity for seralutinib?

Bryan Giraudo
CFO and COO, Gossamer Bio

Yeah, I'll take that, Joe. It's Bryan.

Faheem Hasnain
Chairman and CEO, Gossamer Bio

Go ahead, Bryan.

Bryan Giraudo
CFO and COO, Gossamer Bio

Yeah, we're in discussions right now with PMDA. We hope to have an update by the end of the first quarter. You know, in reality, it will not be too much of an accelerant on enrollment as much as it will be a very significant economic opportunity for Gossamer and for seralutinib. The PAH market in Japan is just around in dollars, so quite significant, and some of the therapies actually have parity, if not premium pricing, to what is achieved in the United States. So more to come. This update from the PMDA is about six weeks dated, so we're in the middle of it right now.

Joseph Schwartz
Managing Director and Senior Equity Research Analyst, Leerink Partners

Thanks a lot. Congrats on the continued progress.

Bob Smith
Chief Commercial Officer, Gossamer Bio

Thanks, Joe.

Faheem Hasnain
Chairman and CEO, Gossamer Bio

Thanks. Thanks, Joe.

Operator

All right, moving on to the next question. We have Andreas Argyrides, Argyrides. Sorry, Andreas, I'm probably pronouncing that wrong, but your line is now open.

Andreas Argyrides
Senior Equity Research Analyst Biotechnology, Wedbush Securities

Yeah, no worries. Thank you. Good morning, guys. Thanks for taking our question. Solid update here. A couple from us. So first, what are your targeted timelines for full enrollment of PROSERA? And then how are you. And the second question is: how are you thinking of, or how are you working with the FDA to get disease modification on the label? And then for Bob, congrats on your new role. Question for you: how are you thinking about the uptake for seralutinib, given the clean safety profile versus other agents? Thanks.

Faheem Hasnain
Chairman and CEO, Gossamer Bio

So, enrollment timeline, we have been and have continued to guide to what would have been an 18-month enrollment timeline, which would take us to top-line data, the back end of 2025. So that's, you can expect us to be talking about that data, the top line, say, two years from now. Richard, you wanna handle the second question?

Richard Aranda
CMO, Gossamer Bio

Yeah, so, the disease modification, we're continuing to have ongoing dialogue around that with the FDA. It's something that, you know, is a little bit more requiring additional thought around which data and how we can use our CT imaging. So we anticipate that dialogue to be an ongoing process throughout even the first quarter of next year.

Bob Smith
Chief Commercial Officer, Gossamer Bio

Yeah, and Andreas, I'll take the other part. First of all, thank you. I appreciate the well wishes. In terms of the uptake, particularly as the safety profile of seralutinib continues to play out, I expect rather rapid uptake. As Faheem mentioned, there is this notion of warehousing anytime a new therapy is coming out, right? You have in a progressive disease, you have many patients that are currently are dual or triple therapy, that have basically run out of options. And we'll see that continue to build, you know, over the next several months, about the time seralutinib will come to the market. So I would, you typically see this bolus in the first three to six months of PAH therapy launch.

I would fully expect that with seralutinib, and based on the efficacy and the tolerability as we're seeing now in the data, again, I would expect it to, you know, be positioned earlier in the treatment paradigm to help with that reverse remodeling. Not only alone, but I think at that point in time, in combination with sotatercept, where there's a lot of interest there. So I give you a nice opportunity for seralutinib, pretty much right out of the gates.

Andreas Argyrides
Senior Equity Research Analyst Biotechnology, Wedbush Securities

Okay, thanks, guys. Appreciate the color there, and congrats on all the progress. Thank you.

Bob Smith
Chief Commercial Officer, Gossamer Bio

Thank you.

Operator

All right. At this time, we have one more question in queue. I'd just like to remind participants, you can press star one on your telephone keypad if you would like to get a question in. So far, our final question in queue is coming from Vamil Divan. Your line is now open.

Speaker 10

Hi, team. This is Daniel on for Vamil. Thanks for taking my question. So I was wondering if maybe you can go into, in further detail onto the response seen in the placebo crossover group as compared to the seralutinib continued group, with maybe any potential differences seen in the baseline characteristics, differences in background therapy or anything there of note? And my second question would be, if there's any plan to maybe share some additional patient-specific analysis in the future. There appears to be some patients that have some pretty dramatic responses, so, any additional color there would be helpful. Thank you.

Bob Smith
Chief Commercial Officer, Gossamer Bio

Yeah. I can just give you a little bit more color around the placebo patients. You know, fundamentally, at baseline, they were generally balanced between the active and placebo arms in terms of PVR and six-minute walk. So those that entered into the open label, they did tend to have a little higher PVR than the seralutinib group that also went into the open label. Other than that, there wasn't very much any difference around background medications or any other features. So I, you know, the. As Rob was mentioning, the effect that we observed was less than those that continued on seralutinib, but there did not seem to be any background characteristics that accounted for that difference.

And then I think to the second question about individual patient data, you know, we do have a lot more information. We are saving that for a major medical meeting. We're targeting quite a splash at the American Thoracic Society meeting because it'll be in our hometown of San Diego. So more to come on that front, but obviously, to your point, we are thrilled to have seen somewhat appear to be super responders in the data. And certainly when we take that experience and really the totality of what we've seen, hemodynamics as well as six-minute walk, I think we can say that the enthusiasm in the clinical community for those who have dug into the data is quite high, and we look forward to really having quite a splash at ATS.

Faheem Hasnain
Chairman and CEO, Gossamer Bio

I'll add one more thing-

Speaker 10

Great.

Faheem Hasnain
Chairman and CEO, Gossamer Bio

I'll add one more thing to your question. That is that, typically, this is what we see when we have drug-to-drug patients versus, placebo-to-drug, that the, the patients who are on placebo in a study that go into an open label extension, it typically takes them longer to catch up, given the nature of the progressive disease, the fact that the disease doesn't get well managed while on placebo, even though that they're on background therapy. And then when they get switched over to drug, you see, you see a definite lag, which speaks to, the importance of early treatment, as I had mentioned earlier, to prevent that longer-term disability.

Speaker 10

Okay, great. Yeah, thank you very much, and thanks again for taking my questions.

Operator

At this time, there are no further questions in queue.

Faheem Hasnain
Chairman and CEO, Gossamer Bio

Okay. Well, listen, on behalf of the Gossamer team, we'd like to thank all of you for joining in and listening in to the call. Obviously, questions come up at any time. You know how to get a hold of us. In the meantime, we're super exciting about the PROSERA study, and we look forward to advancing this therapeutic to hopefully making a huge difference for patients with PAH. So thanks, everybody.

Operator

All right, ladies and gentlemen, this does conclude your call. You may now disconnect your lines, and thank you again for joining us today.

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