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Good day, and welcome to the Travere Therapeutics First Quarter 2024 Financial Results and Corporate Update Conference Call. Today's call is being recorded. At this time, I would like to turn the conference call over to the Manager of Investor Relations, Anne Crotteau. Please go ahead, Anne.

Thank you, Rachel. Good afternoon, and welcome to Travere Therapeutics First Quarter 2024 Financial Results and Corporate Update Call. Thank you all for joining. Today's call will be led by our President and Chief Executive Officer, Dr. Eric Dube. Eric will be joined in the prepared remarks by Dr. Jula Inrig, our Chief Medical Officer; Peter Heerma, our Chief Commercial Officer; and Chris Cline, our Chief Financial Officer; Dr. Bill Rote, Senior Vice President of Research and Development, will join us for the Q&A session. Before we begin, I would like to remind everyone that statements made during this call regarding matters that are not historical facts are forward-looking statements within the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Forward-looking statements are not guarantees of performance. They involve known and unknown risks, uncertainties and assumptions that may cause actual results, performance and achievements to differ materially from those expressed or implied by the statement. Please see the forward-looking statement disclaimer on the company's press release issued earlier today as well as the Risk Factors section in our Forms 10-Q and 10-K filed with the SEC. In addition, any forward-looking statements represent our views only as of the date such statements are made, May 6, 2024, and Travere specifically disclaims any obligation to update such statements to reflect future information, events or circumstances. With that, let me now turn the call over to Eric. Eric?

Thank you, Anne, and good afternoon, everyone. This year, our organization is focused on executing on the key priorities that will drive sustainable growth for Travere in 2024 and the years ahead. I am pleased to report that we made significant progress on all fronts. Our commercial launch of FILSPARI in the U.S. is continuing to reach new highs. We successfully achieved multiple regulatory milestones with FILSPARI, and the first patients were dosed in the pivotal HARMONY study of pegtibatinase. I'll begin with the FILSPARI launch in the U.S. Following a strong close to 2023, our team continued to elevate performance in quarter 1. Importantly, this was demonstrated across all key aspects of the launch: increased patient demand, new and repeat prescribers, faster time to reimbursement, and broader payer access. We continue to have the highest demand amongst recent rare renal benchmarks, and we achieved 35% growth in revenue over last quarter despite the typical new year headwinds with gross to net adjustments. Notably, we are seeing this strength continue in the second quarter. This reflects strong execution by our commercial team but also the underlying demand for a superior foundational treatment. Peter will provide further detail on the quarter 1 performance and our outlook shortly. To start 2024, our regulatory team achieved important milestones in our journey to deliver FILSPARI to more patients globally. Today, we are very pleased to report that our submission to convert FILSPARI from accelerated approval to full approval has been granted priority review by the FDA. This marks a critical step forward for full approval, which we expect would include a label enabling us to reach a broader set of patients living with IgA nephropathy in the U.S. Outside of the U.S., our partners made important progress with the recent conditional marketing authorization, or CMA, of FILSPARI for IgAN in Europe and submission of an IND for a Phase III trial in IgAN patients in Japan. Jula will provide further detail on our regulatory engagements and milestones for the rest of the year. We also made good progress on our pegtibatinase program, which provides an opportunity for significant growth for Travere beyond FILSPARI. This program is the only late-stage development candidate for HCU and the only medicine in development for HCU that has the potential to be disease-modifying. With successful efforts, we anticipate that pegtibatinase could become a new treatment standard in the market that we expect to grow well beyond $1 billion. We initiated the Phase III HARMONY study at the end of last year, and we are pleased to have dosed our first patients in the study. Overall, we remain on track to report Phase III top line results in 2026. Now let me turn the call over to Jula for her update. Jula?

Good afternoon. I'll start with IgA nephropathy where our medical activities for 2024 are focused on ensuring we achieve full approval of FILSPARI and providing the education and support to enable FILSPARI to replace RAS inhibitors as foundational care. It is important to remember that patients living with IgA nephropathy face a high lifetime risk of kidney failure, and the time to meeting kidney replacement therapy is even shorter for those with persistent proteinuria. IgAN is caused by overactivation in both the kidneys and the immune system. As a result, clinicians have historically focused on 2 complementary ways of treating IgA nephropathy: first, with foundational care directly addressing the overactivity in the kidney, which has been the role RAS inhibitors have played; and second, addressing systemic inflammation with steroids for select patients. We are at an exciting juncture where we are seeing improvements in the options addressing both of these approaches independently, and the future will include using both of these in tandem in more effective ways. This is critical as there is no single medicine approved or in development that will arrest the progression or effects of IgA nephropathy. We are most excited about the evolution of the treatment paradigm because FILSPARI is the only medicine that is in position to replace the foundational role of RAS inhibitors. This is because FILSPARI is the only approved non-immunosuppressive medicine for IgAN that directly targets kidney injury, known as Hit 4, and protects the kidney from further structural damage. And most importantly, FILSPARI is the only treatment that has been evaluated head-to-head against RAS inhibitors, specifically irbesartan, and shown clear superiority in proteinuria reduction along with clinically meaningful long-term kidney function preservation. Everything else has been added on top of RAS inhibitors and/or is targeting elsewhere in the disease cascade but, unfortunately, not comparing directly to what works on that similar pathway. As we move ahead, we believe nephrologists will use FILSPARI as a foundational kidney targeted therapy and then add upstream immune-mediated medications as needed. Perhaps not surprisingly, we are continuously hearing from nephrologists, as they are gaining more experience with FILSPARI, that they are making the choice to utilize FILSPARI as foundational care for their eligible IgAN patients. And this is further validated by increasing recommendations in treatment guidelines and algorithms to replace RAS inhibitor therapy with FILSPARI in patients who remain at risk for progression. We also continue to generate additional supportive data. At the recent World Congress of Nephrology meeting, we presented new data describing subgroup analyses from the PROTECT study, demonstrating that treatment with FILSPARI had a clinically meaningful benefit on long-term kidney function preservation at 2 years across a broad range of baseline proteinuria subgroups. This signifies that FILSPARI can have a positive impact in a wide range of proteinuria levels, and we believe it is supportive for potentially broadening our label at full approval. We also presented data from our SPARTAN study, examining newly diagnosed RAS inhibitor-naive patients, which showed an 80% reduction in proteinuria and stable eGFR out to 36 weeks, some of the most impressive IgAN data to date. These results show that if you treat IgAN patients early enough with FILSPARI, we stabilize eGFR and can get 2/3 of patients into complete remission. Additionally, we presented data that showed adding SGLT2 inhibitors to FILSPARI is safe and can further reduce proteinuria. Collectively, these results are supportive of earlier and broader use, and we look forward to providing longer-term results at upcoming congresses. As the IgAN treatment paradigm continues to evolve, we also hear from thought leaders and hold the belief ourselves that the field is moving towards earlier diagnosis and treatment of patients earlier in their disease. This is widely anticipated to be recognized in the upcoming KDIGO guideline revision. This will support intervening earlier with foundational care and, following full approval, provide a good opportunity for us to further educate on the lifetime risk for these patients. They don't have time to wait as every day they are losing kidney function. Now turning to our key regulatory milestones to start the year. As Eric highlighted earlier, we were very pleased to receive Priority Review for our sNDA with an assigned PDUFA target action date of September 5 of this year. Additionally, the FDA has communicated that they do not plan to have an advisory committee meeting to discuss the application. We look forward to continuing to work with FDA throughout the review process, including engaging on the REMS for liver monitoring. We are also pleased with the recent European Commission decision to grant conditional marketing authorization to FILSPARI in Europe. It is important to note that FILSPARI is the only medicine for IgA nephropathy to receive a CMA for patients with proteinuria greater than 1 gram per day or greater than 0.75 grams per gram. The next step in Europe is transitioning to full approval, and we are presently supporting the submission preparation process in partnership with CSL Vifor. We also recently announced that our partner in Japan, Renalys, has made progress with an IND submission and advancing their study to support ultimate approval in Japan and other Asia Pacific regions. I'll provide a brief update on FSGS. Our efforts in FSGS continue in the background, and we remain hopeful that we will be able to identify a path forward for an additional indication for FILSPARI. In parallel with our efforts, PARASOL, which is a public-private partnership with NephCure, the FDA, EMA and academia, is bringing together FSGS data sets from around the world to help define the relationship between proteinuria, eGFR and kidney outcomes. Their goal is to align on an end point that would support approval of new therapies for FSGS patients, and they plan to present their data at ASN in late October. We will continue to compile our data and reengage with FDA at the appropriate time once the PARASOL work is near to completion. Now let me discuss our HCU program in Phase III development. We continue to be very excited about our potential to deliver pegtibatinase as the first disease-modifying therapy for HCU. We recently engaged with HCU thought leaders and patient advocates at adboards and medical conferences, and there is significant enthusiasm about the potential for pegtibatinase to positively change the lives of people living with HCU. The available treatment options do not address the underlying cause of HCU nor do they help patients address the risk of thrombotic events or address the need for low protein diets. These often require drinking medical formula to help achieve adequate nutritional intake and can negatively impact many social aspects of daily life. We believe that pegtibatinase, as the only therapy directly targeting the key enzyme defect in HCU, can change that if approved. We are pleased to have achieved the first patients dosed in the pivotal HARMONY study. As we've discussed, we are metering enrollment in the earlier stages as we ensure we have high-quality adherence to our protocol and continue to scale our supply for the duration of the program and commercial use. So far, we're getting positive feedback from our sites, and we continue to anticipate top line data in 2026. This quarter, we will also begin to transition patients from our Phase I/II COMPOSE trial on to our open-label ENSEMBLE study. This will allow for eligible COMPOSE patients to enter into our protein tolerance or diet modification sub-study and start generating data for this important exploratory end point. In summary, we are pleased with the progress in each of our programs, which is a testament to the talented team at Travere who are passionate about working to deliver life-changing therapies for people living with rare diseases. Let me now turn it over to Peter for a commercial update. Peter?

Thank you, Jula, and good afternoon, everyone. 2024 is going to be an exciting year for FILSPARI as we are building upon a solid foundation that was created in 2023. And I'm pleased to report that we started the year with strong performance in the first quarter. We continue to see strong enrolling demand from physicians and their patients. This is evidenced by the continuous increase in both breadth and depth of prescribers during the quarter. Notably, we have now had more than 2,000 nephrologists who have enrolled and certified in the FILSPARI REMS program. Most of these physicians have already started prescribing FILSPARI and have witnessed a real innovation of endothelin and angiotensin benefits their patients in a meaningful way, and this number continues to grow with signals that demand is expected to remain broad. This growing prescriber base and persistent demand resulted in a continuation of growth in new patient start forms to 511 in the first quarter. We have now seen sequential growth in patient start forms for the first 5 quarters of launch and exceeded the 500-patient start forms faster than any of our benchmark comparisons in rare nephrology. From a payer perspective, approximately 95% of the U.S. patients have a pathway for reimbursement of FILSPARI. We continue to be pleased with the quality of the authorization criteria, which are largely in line with label language and guideline recommendations. I'm pleased that this early in the launch, we have achieved such a high level of progress. And the pace of transitioning demand into paid shipments continuously improve. The enhancements we made in the second half of last year are working, and we now see that about 80% of the patients that are prescribed FILSPARI are enrolling in the REMS program within 14 days of patient start forms received. And our quarterly number of new paid shipments continues to decline. Our collective efforts led to $19.8 million in revenue and sales for the first quarter. We are pleased as we continue increasing the revenue, especially in the first quarter of the year where we experienced elevated gross to net adjustments as is typical to start the new year. The strong start in 2024 adds to our confidence in driving significant growth for FILSPARI this year and our goal of outperforming the benchmark metrics for the second year of launch. In addition to the consistent patient start form growth, we have also maintained a high growth rate in revenue since the initial launch quarter compared to benchmarks. And of note, the strong sales trend has continued through the second quarter so far. This adds confidence to our belief that we will drive continued revenue growth quarter-over-quarter as we move to some of the key inflection points later this year that can further accelerate our growth. To this end, we anticipate FILSPARI will be included in the upgraded KDIGO guidelines, which are expected to be available for public review in the coming months. Additionally, based on the increasing body of evidence that proteinuria is directly toxic to the kidney and, therefore, a prominent risk marker of progression towards kidney failure, we anticipate a more ambitious proteinuria target in the guidelines. This will further increase the urgency to treat patients earlier and more aggressively. Upon potential full approval in September, we anticipate an expanded label, which would provide greater support for physicians to prescribe FILSPARI to a broader patient population. This could be particularly well-timed as nephrologists digest the KDIGO guideline and begin to diagnose and treat their patients earlier. We also expect that the additional clinical evidence that Jula highlighted earlier will ultimately provide additional support for physicians to treat earlier with FILSPARI and to use it potentially in combinations with other available medicines for patients that may need more aggressive treatments. These milestones will support our ambition to make FILSPARI the foundational treatment option for IgA nephropathy patients with the potential for novel complementary modalities, if approved, to be added on top in the future. As for THIOLA and THIOLA EC, these medicines remain steady, contributing approximately $20 million in net dollar sales in the first quarter while encountering the difficult gross to net resets at the beginning of the year. As previously reported, we saw a generic approval earlier this year and are continuing to evaluate how the market may evolve as a result. Let me close out by reiterating that I'm really pleased with the execution of our fantastic commercial team and the clearly positive results in the first quarter of the year. All their efforts have resulted in a strong foundation for growth, leading towards anticipated full approval later this year and the continued confidence that FILSPARI has the potential to become a blockbuster therapy. Let me now turn the call to Chris for the financial update. Chris?

Thank you, Peter, and good afternoon, everyone. We started the year with strong operational performance illustrated by the continued growth of FILSPARI and reduced operating expenses. For the first quarter of 2024, net product sales were $40 million compared to $24.2 million for the same period in 2023. The increase is attributable to growth in net product sales from the ongoing launch of FILSPARI and IgA nephropathy. During the quarter, we also recognized $1.4 million of license and collaboration revenue, which resulted to $41.4 million in total revenue reported for the period compared to $30.9 million in the same period in 2023. Research and development expenses for the first quarter of 2024 were $49.4 million compared to $58.2 million for the same period in 2023. On a non-GAAP adjusted basis, R&D expenses were $45.8 million for the first quarter of 2024 compared to $51.3 million for the same period in 2023. Selling, general and administrative expenses for the first quarter of 2024 were $64.2 million compared to $66 million for the same period in 2023. On a non-GAAP adjusted basis, SG&A expenses were $48.2 million for the first quarter of 2024 compared to $49.5 million for the same period in 2023. The approximate 11% decline in non-GAAP R&D and SG&A expenses compared to last quarter is largely attributable to the restructuring enacted in December and reduced clinical expense as the Phase III studies advance towards completion. Total other income, net, for the first quarter of 2024 was $3.5 million compared to $0.9 million in the same period in 2023. The difference is largely attributable to an increase in interest income during the period. Net loss including from discontinued operations for the first quarter of 2024 was $136.1 million or $1.76 per basic share compared to a net loss of $86.3 million or $1.27 per basic share for the same period in 2023. On a non-GAAP adjusted basis, net loss including from discontinued operations for the first quarter of 2024 was $116.2 million or $1.51 per basic share compared to a net loss of $62.9 million or $0.92 per basic share for the same period in 2023. To begin the year, we achieved a number of milestones with our programs that will result in corresponding milestone payments. During the first quarter, we recognized a onetime in-process research and development, or our IPR&D, expense of $65 million. This was triggered by achieving the first patient dosed in the Phase III HARMONY study and is expected to be paid in the second quarter of this year. With the recent conditional approval of FILSPARI in Europe, we expect to receive a $17.5 million milestone payment from CSL Vifor upon conversion of the CMA to full approval, and we also anticipate receiving an additional milestone payment in 2025 upon achievement of market access milestones in certain countries. Also related to the CMA approval, we expect to pay Ligand Pharmaceuticals a onetime milestone payment of $5.75 million in the second quarter of this year. As of March 31, 2024, the company had cash, cash equivalents and marketable securities of $441 million. Cash used during the first quarter included approximately $61 million of nonrecurring items related to the strategic reorganization announced in December, delivery of inventory, corporate performance payout and pass-through receivables to Mirum Pharmaceuticals as a result of the bile acid products transaction last year. Importantly, we anticipate operating cash used to decline meaningfully through the balance of 2024. With our current strong cash balance, expected significant growth in FILSPARI, continued expense management and anticipated incoming future milestone payments, we continue to expect that our balance sheet can support current operations until 2028. I'll now turn the call back over to Eric for his closing comments. Eric?

Thank you, Chris. We are in a differentiated position to drive value and growth. We are executing very well on the commercial launch of FILSPARI, which is targeting to outperform benchmark launches in year 2 and continue to grow significantly in the years ahead. FILSPARI also has the potential for a second indication for FSGS, which would be the only approved medicine for a rapidly progressing kidney disorder with little else in development. And we are advancing pegtibatinase, an innovative enzyme replacement therapy in a Phase III program that could deliver the only disease-modifying therapy for a devastating rare condition, affecting an estimated addressable population of 7,000 to 10,000 patients worldwide. With these opportunities to create significant value, we are acutely focused on executing in 2024. We have started the year by achieving all of the milestones anticipated thus far, and we expect to continue that trend through the balance of 2024. Now let me turn the call back over to Anne to open up the lines for Q&A. Anne?

Thank you, Eric. Rachel, we can now open the line up for Q&A.

[Operator Instructions] We will now take the first question from the line of Anupam Rama with JPMorgan.

Can you hear me?

Yes, Anupam.

Congrats on all the progress on the quarter. I just had a quick question. For FILSPARI, can you talk about any sort of seasonal headwinds you saw in the quarter from reauthorizations or otherwise that we should be considering?

Yes. Thank you for the question. And certainly, that's something that we would typically expect at the beginning of the year. Peter, why don't I turn that over to you to share some of the dynamics that we would see in quarter 1.

Yes, certainly. And thanks, Anupam, for that question. So overall, I would say we have very strong performance across the board, both from a demand perspective as well as from a payer and pull-through perspective. I think the only seasonality that I could speak to is the gross to net, as you would expect, in the beginning of the year. You have an impact of gross to net that has to do with the reauthorization process, the insurance plans, important rebates, co-pay buydowns. But it's typical for all products, and I think that's typical for FILSPARI. We have seen it also with our legacy product. So no, overall, I will say there is strong performance in Q1.

Our next question comes from the line of Tyler Van Buren with TD Cowen.

Great to see the results. So the last couple of quarters, patient start forms increased by like around 15 to 20 forms quarter-over-quarter. And now we've seen an increase of over 50 quarter-over-quarter for Q1. So just curious to hear you elaborate on that specifically. What's changed or improved? Is it simply just a better REMS enrollment as mentioned? Or what are other factors leading to the increase in the patient start forms?

Tyler, thanks so much for the question. I'll turn this one also over to Peter.

Yes. Thanks for the question, Tyler. You're right. I mean, we saw a strong demand in the first quarter. And what I would say is at ASN last November, when we presented the PROTECT full 2-year data set, we really built the momentum for FILSPARI. And I think that also resulted into an inflection in demand, and that trend basically continued in Q1. So we saw like 511 new patient start forms in the first quarter versus like 459 in Q4 last year. And this trend includes both the breadth of prescribers as well as depth of prescription. And I think most importantly is that also, the majority of the thought leaders are now prescribing FILSPARI.

Your next question comes from the line of Joseph Schwartz with Leerink Partners.

Congrats on the Priority Review designation for the FILSPARI IgAN sNDA. I'm wondering if you can provide some more color on the data package that you submitted to the FDA to support the sNDA, specifically how much safety data from the real world or clinical trials was submitted. And how are you feeling about the potential for the REMS to be adjusted based on additional data that you submitted?

Joe, thanks for the questions. I will turn this one over to Jula to answer.

Thanks for the question, Joe. So we did submit the safety data from the 2-year PROTECT trial, and we will give a 4-month safety update as is typical, which will be a compilation of our safety data. And you specifically asked about the REMS, and I'll just reiterate that we have seen no cases of drug-induced liver injury throughout the program. We also have additional commercial safety data that we periodically report and have continued to provide to the FDA as just part of our regular safety reporting. And we haven't seen anything concerning or different than what we've seen from a safety perspective in our clinical trials. And as you can imagine, we'll be engaging with the FDA through the review process for any potential modifications or changes to the liver monitoring REMS, and we'll provide an update when the sNDA is complete.

Our next question comes from the line of Carter Gould with Barclays.

Congrats on the progress of FILSPARI. But maybe to flip it up a little bit and switch to HCU, you talked about sort of metering enrollment. Is there a certain number of patients or a time line before that could be lifted? And I guess, along the same lines, you also spoke on manufacturing. Can you just kind of bring us up to speed on sort of the efforts there to ramp on that side of things?

Sure. Thanks, Carter. I will turn this over to Jula to provide a bit more detail.

Certainly. Thanks. So I mean we have a very exciting trial design to be able to show a difference in total homocysteine and then also look at a reduction in diet. The trial design, as you may recall, we have a 10-week screening period, and that is to help with diet stabilization and to standard that to optimize our chance of success, to get things standardized before the patients get in the trial. So we have that 10 weeks and then a 26-week double-blind period. Now you recall, we've announced that we have about 70 patients in 50 sites. We do want each of our sites to be educated, upskilled and trained on some of the unique aspects and unique tools that we are providing as part of this. And so again, we are doing it slower in the beginning, but we are going to have data, as we've said, top line data, in 2026. That has not changed. That's part of our assumptions. And then I'll comment a little bit about CMC. So as is typical in rare disease, when you go try to move fast from Phase I to Phase III, you're often doing your CMC work in parallel. And we're trying to upskill so that we're ready for that, where we support the full study as well as commercialization.

Next question comes from the line of Jason

Perfect. Congratulations on the progress. I wanted to circle back and follow-up on FILSPARI here. Just curious what you were hearing from specifically new prescribers regarding their experiences, especially now that discussion over PROTECT sort of continues to build. I guess what I'm trying to drive at here is where does near-term momentum take you in terms of further acceleration of script growth for the rest of the year. And then what happens following potential full approval in September?

Yes. Jason, thanks so much for the question, and welcome to working with us at Travere. So I'll hand it over to Peter to give a little bit more detail. Before I do, I do want to reiterate something that Peter mentioned in his prepared remarks, in that, the dynamics that we're seeing across the board with the FILSPARI launch give us great confidence that we will see very strong revenue growth this year and onward, particularly this year, quarter-over-quarter revenue growth. And I think it certainly is, in large part, due to new physicians identifying patients. Peter, why don't you share a little bit more about what you're hearing from new prescribers and how you see the growth moving forward.

Yes. Very good. Thank you, Jason, for that question. I would say, overall, from new prescribers, what we are hearing is the same consistency of strong proteinuria reduction of about 50%, consistent to what we saw in the PROTECT study. I think that by itself also is the best evidence for continued prescription and further depth of prescription. So as we're looking forward for the rest of the year, I think we have some inflection points that I called out in the prepared remarks. I think one is the full approval that we know now with a PDUFA of September 5 but also the new KDIGO guidelines. I think that allows for continued growth. And I'm expecting that we will see continuing growth for the remainder of the year in patient start forms. But we also know that there may be variability quarter-over-quarter from a patient start form perspective. I would say from a revenue perspective, I'm confident that we will continue to have quarter-over-quarter growth for the remainder of the year.

Next question comes from the line of Maury Raycroft with Jefferies.

Congrats on the progress. I was going to ask one on FSGS. Just wondering what additional analyses are you conducting to discuss with regulators this year for a potential path forward? And can you clarify if you're engaging with the PARASOL Group 2 and have insight into what they're doing? Or is PARASOL independent? And just for the sequence of events, will you wait to see what PARASOL shows at ASN and try to get an FDA meeting scheduled by year-end? Or I guess, how could these events play out this year with FSGS?

Maury, thanks for the question. And Jula, would you like to answer those?

Yes. So we're continuing to analyze our data in totality and also comparisons to external data sets. We haven't fully defined all the analyses that we're doing. But our work is in parallel with PARASOL. We are invited to the PARASOL group. There is a meeting that's public that we're going to be meeting in person in, actually, next month to look at the data sets and look at the end point. So we will have insights into what the end points they're looking at to be able to then also look at our data as well. And so our time line is that we're working in parallel with our data as well as what they are working on to define the end point with a plan really to reengage, I would say, at the end of this year, early next year, after they have publicly announced what those end points should look like and what they should be.

Got it. And then after you reengage with the PARASOL group, then you would request a formal meeting with FDA?

Yes. We're working and we're hearing what they're working on. We're also analyzing our data in parallel. After they publicly announce with that end point, that would be the time line at which we would be reengaging for potential filing.

Your next question comes from the line of Tim Lugo with William Blair.

This is Lachlan on for Tim. I was wondering if you can talk about the conversion rate you're seeing from the patient start forms to actually getting on drug, both the time it takes but also what kind of attrition there is there. And to the extent there is attrition, what are the sort of sticking points where you might be losing some patients?

Yes. Lachlan, thanks for the questions. I'll hand this one over to Peter to provide a bit more detail on the launch dynamics.

Yes, thanks, Lachlan. I would say, since we implemented additional patient education initiatives in the second half of the year, we have seen continuing improvement in our fulfillment process. And one of the leading messages that I was talking about in the prepared remarks is the percentage of patients got certified to the REMS program after receiving their patient start form. And as I mentioned, we have now about 80% of the patients that are prescribed with FILSPARI that enrolled in REMS within 14 days of patient start form received. I would say we are very pleased with the continuing efficiencies that we are seeing, including payer approvals for FILSPARI, and I'll reiterate as well within rare disease benchmarks, and that we have confidence that we will continue to see revenue growth quarter-over-quarter for the remainder of the year.

Yes. And Lachlan, maybe one thing that I'll add that we've talked about in the past, that Peter has mentioned, is the high rate of compliance and persistence once a patient is on therapy. We continue to see that, which I think is an important aspect of this launch and what gives us great confidence that we will continue, as we add more patients, that the growth rate and revenue will continue to be strong as we move forward.

Your next question comes from the line of Yigal Nochomovitz with Citigroup.

Congrats on the progress. I may have missed it, but did you comment on out of the 511 start forms, what fraction of those 511 are on commercial drug at this point?

Yigal, we've not provided those details in terms of number of patients. At this point in the launch, we'll continue to provide those rates of PSFs as well as revenue and access as we see those as the core components of launch performance in the first part of the launch. I think what we certainly are seeing is a continued progress in terms of the number of patients that are treated as we move forward, as outlined by Peter. Peter, is there anything more that you'd like to add?

No. I think you covered it all, Eric.

Your next question comes from the line of Mohit Bansal with Wells Fargo.

This is Reid on for Mohit Bansal. My first question here is just on the KDIGO guidelines. Could we see an improvement for FILSPARI in the guidelines ahead of that September 5 PDUFA date?

Jula, I'll turn that one over to you.

We anticipate the KDIGO guidelines to be out soon. That is what we're hearing. And with regards to how that could help with FILSPARI, I would say that it's twofold. We anticipate that the KDIGO guidelines will suggest that patients who remain at risk for progression despite RAS inhibitors would be considered to switch to FILSPARI, so just further reinforcing the foundational role that FILSPARI should play. As we know, most patients have been on a RAS inhibitor, many predating their diagnosis, and FILSPARI is superior to RAS inhibitors at lowering proteinuria, as we demonstrated in a Phase III head-to-head trial. The other aspect that goes beyond that is that we anticipate the KDIGO guidelines will lower the proteinuria treatment target. That means that even more patients will need better treatment, which FILSPARI clearly offers.

Your next question comes from the line of Vamil Divan with Guggenheim Securities.

I just had one I was going to ask, but maybe to follow up on the prior comment you made around the compliance and persistence. And I think you said you're having a high rate of compliance and persistence. I'm just wondering if you can quantify that a little bit more for us in terms of what percentage of patients are still on therapy, maybe 3 months or 6 months after starting. And then my main question was really just around the types of patients that are getting treated now. If you can provide a little more visibility on that in terms of what percentage are going through SGLT2s before they might start something like FILSPARI, what percentage maybe have used Tarpeyo or are using it before Tarpeyo. Also, I think previously, you talked a little bit about the use in the community setting versus academic physicians, if you can provide any sort of update there in terms of just where these prescriptions are coming from and what sorts of patients are being prescribed the product.

Vamil, thanks for the questions. Peter, I will have you cover these.

Yes. There were a lot of questions, I believe, in the question, so let me try to decipher them. To start with the last one, I think one of the questions was like are patients coming from community or academia. Well, there's a dynamic rise in IgA nephropathy. You need to cover a broad range of persistence to really get to all the addressable patient population. And that is mainly because the vast majority of these patients reside in community centers. So that's where the majority of the patients come from. Another question was regarding what is the patient profile. It is overall a younger patient population. And therefore, we also see it reflected in the patients that are in FILSPARI, basically, patients in their 40s, predominantly male. And then I think also from a coverage perspective, I think this is relevant, about 70% of the patients have commercial coverage that also speaks to the consumer patient population. Then I think another part of the question was co-medication and SGLT2. Well, we have a significant amount of patients that also receive SGLT2 inhibitors. I think that is kind of becoming the gold standard. Physicians are generally seeking for like a non-immunosuppressive treatment option. And I think the novel standard of care moving forward is really FILSPARI that includes that RAS inhibitors as well as endothelin but also adding SGLT2. So that is something that we are seeing in practice. And then I think the last question, what you started with, was compliance and persistence. We haven't spelled it out. But the compliance rates are very high compared to what we would typically see in chronic use treatments, in cardiovascular disease, or oncology. So high compliance rates, but we haven't specified that specific number at certain amount of time. I hope I covered all your questions on this one.

Thanks, Peter. Yes, thank you. Maybe just a little bit of context from what we're hearing consistently from patients. Once they start therapy, they have a very positive experience. they appreciate the level of support that our patient services provide. But perhaps even more important, they are seeing a very consistent reduction in their proteinuria. Oftentimes, these patients who are at high risk of progression struggle to see reductions in proteinuria that are meaningful with other therapies. And so they're very pleased to see those reductions with FILSPARI that oftentimes happen very quickly after initiating which we believe is a core part of that compliance rate. Of course, it's a very easy once-a-day oral therapy non-immunosuppressant, all things that we know are important to patients, and we believe that's going to be a core part of building a very robust base of business upon which to grow over time.

Your next question comes from the line of Alex Thomson with Stifel.

I guess a little bit more on sort of the broader commercial dynamics. Could you provide a little bit of context around any inventory or pricing dynamics, headwinds or tailwinds in the quarter?

Sure. Alex. Thanks for the question. Peter, I'll hand that one over to you.

Yes. I would say from an inventory perspective, I don't think we see any difference, better than what you would expect in the second year of launch. I don't think there's too much to speak to on that one. And then I'm missing the other components. You talked about pricing dynamics. Other than the gross to net, this challenge that we have is a little higher in the first quarter of every year, and that's along the industry guideline, and it's typical for FILSPARI. I don't think we have seen any particular dynamic about price in that perspective.

Our next question comes from the line of Laura Chico with Wedbush Securities.

I have one kind of a longer-term outlook for FILSPARI. Japanese competitor recently completed enrollment in their Phase III IgAN study, and we obviously have some other targeted agents moving forward. But as you mentioned, FILSPARI will likely be in the KDIGO updated guidelines. So I guess I'm trying to understand here in this kind of '25, '26 and beyond period, how are you still thinking about FILSPARI utilization as the treatment landscape is changing, particularly if there is a pull forward in diagnosis and earlier treatment?

Yes, Laura, thanks for the question. This is one where we're particularly excited about the long-term outlook for FILSPARI given that it is in a very unique position within the treatment landscape and how it works in the treatment of IgA nephropathy. I'll ask Jula to provide a bit more detail on that.

Yes. Thanks, Laura. I think it's really great to see innovation for a disease that's had very little innovation for many years. And additionally, I think it's exciting to see a potential replacement for the historical role that steroids have played. And I think that's a lot of what we're going to be utilizing these add-on treatments in the future. But I would say, first and foremost, as I said in my comments, you've got to address the activation and injury in the kidney that is present at diagnosis and needs to be treated long term. And that's what FILSPARI offers. Also, as Peter said, they're going to continue other supportive foundational medications because this is a lifelong disease, and that might be an SGLT2 inhibitor for CKD but essentially FILSPARI replacing the role of RAS inhibitors. And that's really aligned with what the KOLs are saying, the guidelines are saying, is that you've got a treatment that's compared head-to-head to historical foundational treatment and FILSPARI is superior to that. And then you can potentially add on additional medications. Just like we've added on steroids historically to RAS inhibitors, you can add on a B cell or a complement inhibitor on top of the foundational role that's FILSPARI.

Your next question comes from the line of Ed Arce with H.C. Wainwright.

Congrats on the strong quarter of progress. Three questions for me. Hopefully, this doesn't get too long. Main one is really about what seems likely coming out of KDIGO and then your PDUFA date on the 5th of September. Given there's no cases of DILI and the REMS monitoring could be softened, likely with proteinuria as in the EU, and given the KDIGO guidelines are looking that way, all of this points to a much more accepting label going forward. And so the question really is, if those do come to pass, what would be your view on the potential for an acceleration further from the growth rates that you're seeing so far? And then just a couple of quick questions on the model. First, around THIOLA, I think the decrease this quarter was largely impacted by the generic entry earlier this year. I just wanted to confirm that that's your view. And then lastly, the $65 million in process R&D, I think you said that was due to the first patient enrolled in the HCU study. I just wanted to confirm that.

All right. Ed, thanks so much. So first question, I will hand over to Peter. So Peter, how do we see KDIGO and the labeling driving growth as we move forward?

Yes, I would say it allows for a broadening of the addressable patient population. Right now, the U.S. label states patients that are at risk of rapid progression is a general proteinuria target of 1.5. I'm expecting that would go down in our label when we have the full approval. But then I think additionally, to your point on KDIGO, and Jula was alluding to this earlier, we are anticipating a more aggressive treatment target with regards to proteinuria. I think that also allows for a broadening of the patient population. And we have mentioned earlier, like the evolving landscape, we have more entrants that may come into the market. It is really a marketing development, I would say. There's more confirmatory biopsies, more early on. And I think that allows for a greater continued growth opportunity for us playing in the IgAN field.

Thank you, Peter. So Chris, I'll hand these over to you. So can you explain the THIOLA generic dynamics on revenue as well as the $65 million anticipated payment?

Thanks for the question, Ed. On the first one, THIOLA, that's not actually related to activities in relation to the generic entry at this point. What we see right now is the typical gross to net adjustments in the first quarter of the year that we've seen in historical years. So that's really the driving difference in Q4 to Q1, and we would anticipate that, that level is similar as it has in years past. And then on the second one, Ed, you have it right that the $65 million IPR&D expense this quarter is related to the first patient dosed in the Phase III HARMONY study of pegtibatinase.

Our next question comes from the line of Allison Bratzel with Piper Sandler.

Congrats on a nice quarter. You mentioned the recent SPARTAN study update in newly diagnosed IgAN patients. I'm just hoping you could talk about KOL and nephrologist reaction to that. And just is it your sense that docs need to see any additional clinical data to really catalyze or drive widespread earlier-line use of FILSPARI?

Yes. So Allison, maybe I'll just comment on one thing that Peter mentioned on this call as well as on our prior call, we're very pleased to see that the majority of thought leaders within the U.S. are currently prescribing FILSPARI to patients with IgAN in their practice. And I think that, that gives a great confidence in the overall profile. Jula, why don't you talk a little bit more about the potential impact of the reaction that you're hearing to the SPARTAN results to date.

Thanks for the question. I think it's very exciting to see the data that we are generating across our program, which is not just SPARTAN, which is earlier treatment, but also combination treatment. And that supports that we believe that FILSPARI should be foundational care and also that patients should be treated earlier in their disease. I think people are very excited about what we've put out around sparsentan that it's newly diagnosed, patients who have not been treated earlier in their disease course, even slightly lower ranges of proteinuria, higher eGFR. And that if you treat early, that you can get patients 2/3 into complete remission, stable eGFR, nearly 80% reduction in proteinuria. People are very excited about this data, and we're going to continue to publish more. We've done 36 weeks, we'll have 1 year data and further data as well as biopsy data. But it really places and reiterate that FILSPARI isn't just targeting damage that's already occurred and helping with the remodel, but it can help prevent the damage that occurs as you have IgA nephropathy deposition because we are treating very early in the disease. And it shouldn't be spared for patients who just have advanced stage kidney disease. So a lot of encouragement around that and excitement as more data comes out later this year around it.

Ladies and gentlemen, this concludes the question-and-answer session of today's conference call. I'll hand the call back over to Anne.

Great. Thank you, everyone, for joining us for our first quarter 2024 financial results call. We look forward to providing additional updates on our progress. Have a great rest of your day.