Gossamer Bio, Inc.

Good afternoon, ladies and gentlemen, and welcome to the Gossamer Bio Q1 2025 earnings call. I will now turn the program over to Brian Girardo, Chief Financial Officer and Chief Operating Officer.

Thank you, Operator, and thank you all for joining us this afternoon. I am joined on today's call by Faheem Hasne, Gossamer's Founder, Chairman, and Chief Executive Officer, Dr. Richard Aranda, Chief Medical Officer, Karen Peterson, Executive Vice President, Regulatory Affairs, and Bob Smith, Chief Commercial Officer. Earlier this afternoon, Gossamer Bio issued a press release announcing its first quarter 2025 financial results and provided a corporate update. Please note that certain information discussed on the call today is covered under the same provision of the Private Securities Litigation Reform Act. We caution listeners that during the 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 risks and uncertainties associated with the company's business. These forward-looking statements are qualified by statements contained in Gossamer's news releases, SEC filings, including the annual report on Form 10-K and subsequent filings. This conference call also contains time-sensitive information that may be accurate only for 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 Fahim.

Thank you, Brian. Good afternoon, everyone, and welcome to our first quarter 2025 earnings call. We're very excited to provide an update on the significant progress and momentum with serolutinib, which is an investigational treatment for pulmonary hypertension, including pulmonary arterial hypertension, or PAH, and pulmonary hypertension-associated interstitial lung disease, or PHILD. So over the past year and a half, we at Gossamer have dedicated immense time, effort, and hard work to enroll our pivotal PAH study, the Phase III ProSERA study. In particular, I want to recognize the efforts of our global clinical operations, development, and field medical team quite literally have been working across the globe around the clock to get us to this point. Today, I'm incredibly proud to announce that we have achieved a significant milestone in the ProSERA study with a closure of new patient screening. And while nearing completion of enrollment is a significant achievement in and of itself, what really matters is enrolling the correct patient population to best position ProSERA for a successful outcome. In this case, that successful outcome is a demonstration of a significant treatment effect in six minute walk distance at 24 weeks. Now with this context in mind, we're thrilled to report that the baseline characteristics of the patients enrolled thus far are precisely what we had targeted. And we are more optimistic than ever about the likelihood of achieving positive results. But I'll dive more deeply into that in a moment. Now, this year, we've experienced great momentum in rolling the study, as growing appreciation of the 72-week Torrey open-label extension data from patients and physicians sparked strong interest in the Procera study. Given this late additional surge of interest, the Procera study has a substantial number of patients currently in screening. And when those potential patients are added to the already 343 patients already enrolled or scheduled to randomize, there are more patients to complete full enrollment by early June. We owe the PAH community a great deal of gratitude for entrusting us, and we will honor that trust by allowing every patient in screening the opportunity to enroll in the Procera study if they qualify. While we expect to complete the blinded portion of the study, including the 24-week, six-minute walk distance primary endpoint by the fourth quarter of this year, We anticipate announcing top-line results in February 2026. This timeline ensures that we can lock the database and thoroughly clean, analyze, and adjudicate the substantial data collected in this robust 48-week double-blind study without sacrificing data quality or operational excellence. Let's now review in detail the baseline characteristics of those enrolled in ProSERA and how this patient population helps set up serolutinib for success. Now, the learnings from the Phase 2 Torrey study helped us to identify specific patient characteristics that would likely respond favorably to serolutinib. By carefully selecting patients with impaired six-minute walk distance and elevated risk at baseline through use of the Reveal Light 2 risk score and other criteria, We aim to enroll a population where a greater magnitude of effect could be seen on the six-minute walk distance at 24 weeks, which is the primary endpoint, thereby increasing the likelihood of success of ProSERA. I am happy to say that given the baseline characteristics that we've seen thus far, the eligibility criteria was successful in enrolling the exact intended patient population. Let's take a closer look at the baseline characteristics. Those that are currently available to us are the first 324 patients enrolled in the ProSara study as of May 12th, 25. It's important to remember that this 324 patient number is distinct from the previously mentioned 343 patients, which includes additional patients that randomize after the May 12th date and patients that are scheduled to be randomized. To start, we find that the average six-minute walk distance is approximately 376 meters, much lower than the toric baseline, where six-minute walk distance averaged 408 meters. For comparison, the Phase III stellar study of cetatricep had a baseline six-minute walk of 401 meters. Second, our mean NT-PRO-BMP, which is an important biomarker of heart failure, is 906 nanograms per liter in Procera, which denotes a materially more severe population than the TORI study, where the mean NT pro-BMP levels were only 628 nanograms per liter. For additional reference, Cetatricep stellar phase III had a baseline mean NT pro-BMP of 1,121 nanogram per liter, nearly double what we enrolled in TORI, and much more similar to what we are seeing in the baseline characteristics of ProSERA. Third, let's address the functional class. Consistent with other precedent positive PAH trials, in our phase two TORI study, serolutinib demonstrated a larger magnitude of effect in the functional class three patients. But a functional class imbalance in the treatment arm versus the placebo arm created what we believe was a major limiting factor in the magnitude of effects seen on the six-minute walk distance in that study. While the placebo arm was 52% functional class III, the serolutinib arm only had 32% of its patients classified as functional class III at baseline in the TORA study. In contrast, 74% of the patients currently enrolled in our ProSERA study are categorized as functional class III at baseline. a significantly larger portion than in Torrey. We will also have a higher proportion than the Stellar study, which mandated that at least 50% of its patients be functional class III and ended up enrolling 51% of these class III patients. And to prevent an imbalance, we have incorporated a stratification factor for functional class to ensure a balanced population between the arms. Why are we spending so much time walking through these baseline characteristics? Well, in short, study after study in PAH has shown us that patients who are sicker at baseline, those with more room to improve, tend to have better outcomes, particularly on the six-minute walk distance in a 24-week study. We saw this in Torrey. where patients with higher baseline reveal risk scores and those with functional class III disease had a much more dramatic improvement in their six-minute walk and their PBR. It was also seen in both the phase II and phase III studies of Cetatercept where functional class III patients had better outcomes than the functional class II patients. Even going back to the pivotal studies of Tyveso and oral imatinib in pH, the pattern holds the same. Procera was designed to enroll more of these patients to increase the study's probability of success. Our team has executed against this goal while maintaining the commercial applicability of the study's findings to a broader population of PAH patients. We believe that the baseline characteristics in Procera represent a population of both functional class II and III that is consistent with contemporary studies in PAH, evaluating six-minute walk at 24 weeks. Because of all this, we believe that we are closer than ever to potentially providing patients with a first-in-class new treatment for PAH that addresses the underlying disease. And with that progress in mind, let's now shift our focus to the exciting prospects ahead for serolibinib. But before I hand it over to Richard to discuss P-H-I-L-D, I want to take a quick moment to thank our partner, the Chiesi Group. Their partnership has enabled serolidinib to immediately enter a global registration on phase three study in P-H-I-L-D. This was one of the key rationale for our joint development and commercialization agreement. They are a world leader in relevant disease areas such as respiratory, cardiometabolic, and rare disease. And we feel proud and highly validated that Chiesi sees the same vision for serolibnib as we do. And more than that, they are a committed partner and proponents of this trailblazing clinical development plan in PHILD. And with that, I'll hand it over to Richard for discussion of PHILD and the Phase III Seronata Study. Richard?