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Neil Kumar

Thanks to everyone on the line for the time, and welcome to our first earnings call. We're grateful to open up another dimension of our dialogue with our investor partners. You collectively allowed us to deliver for the patients we serve, and we look forward to your feedback on how to continually improve our discussion in this setting.
Today, we know the star of the show is the Attruby launch. And the good news is that the brand is delivering for patients and the business. $36.7 million in revenue this past quarter suggest that clinicians and patients resonating with our differentiated clinical efficacy, safety, and accessibility.
We continue to educate on our therapeutic impact, which comes as early as three months with a 42% relative risk reduction on cardiovascular hospitalization and mortality at 30 months, including a 50% reduction in cardiovascular hospitalization at that same time point.
All these best-in-class point estimates are available at the lowest price point in the marketplace. There is much to like there and we're aware that there is much work yet to be done. You'll hear about some of that work today as it pertains both to commercial tactics and further development work.
We add to Attruby good news to continued progress across our pipeline of three additional blockbuster products. Our trials in Limb-Girdle muscular dystrophy type 2I, achondroplasia, and ADH1 remain on track with low dropout rates, frequent data collection and positive site audits, all in preparation for an efficient NDA submission should the data be positive.
Furthermore, key additional markets are being opened up. Our hypochondroplasia trial enrolled with incredible speed, and we now have first patient in there. Our work with Encaleret in the hypoparathyroid setting positions it well for a registrational trial to successful could pave the way for the first oral compelling solution in that space.
Before we move to the discussion into further specifics regarding the business and since this is our first time hosting this type of call, I wanted to briefly address how we measure the performance of our business on an ongoing basis. It's nice that this quarter was a success, but there will be harder quarters, I am sure. And through it all, you should expect for us to communicate consistently and in terms of net gains or losses in NPV.
For instance, in this last quarter, our NPV increased by 9%, given changes in the following variables: number one, the time factor of money, especially given the late stage of our portfolio; number two, a higher-than-anticipated revenue driven by a faster uptake of Attruby than we anticipated and likely a slightly higher peak year share by volume than our market research had projected; third is the success of our small study in HP and other sponsors setbacks in the space of oral HP medicines; fourth, the early enrollment of our run-in of our hypochondroplasia study, moving our timelines in for that program; and fifth, a slight decrease in our model cost of capital given our recent convertible offering. There were NPV drags, most prominently including tariffs. However, these have a close to negligible effect at less than 1% of our overall NPV.
Stepping back from NPV and as a reminder, our overall objective here at BridgeBio is simple, to maximize the positive change we can have in terms of quality-adjusted life years for the patients that we serve as quickly as possible. We do so by creating as many meaningful medicine as quickly as possible within three constraints.
The first is that each program must have beautiful science, which in our vernacular means a high POTS driven by understanding of mechanism of disease optimally paired with a therapeutic mechanism of action that targets a well-described genetic condition at its source.
These types of programs historically have a three to four times higher probability of technical success than all-comer drug R&D efforts. Over time, in many programs, this elevated probability of technical success moves us from being a speculative lottery ticket to being something akin to an engineering company.
The second constraint is that we strive for each medicine that we make to be first-in-class or best-in-class. Determining best-in-class can be tricky in the absence of double-blind head-to-heads, but we approach this news as a straightforward basin approach.
For instance, in TTR, if faced with this vision as to what drug to use, a logical person would first interrogate the salient endpoint, death and hospitalization at a common time point. In this case, at 30 months, a relative risk reduction of 42% is a better point estimate as compared with any of the other products in this marketplace. You would then ask, how quickly does each drug take action. And you would find that the three-month beginning of separation between placebo and active is the earliest point estimate of timing of impact in this field. So logically, Attruby is at worst, no worse than other medicines.
You would then look at safety. Here, you would find a little difference between small molecules, but would observe that they do not have the safety signals some knockdowns have, vitamin A deficit, which, by the way, turns knockdowns into a once-daily pill regimen, injection site reactions, the absence of impact on [Afib] whereas both small molecules had meaningful reductions there, the imbalance of cardiac SAEs is observed in the IMPATRO study and the as of yet unexplained imbalance in death on the revusiran trial.
You couple that with the overall finding that across multiple studies, TTR is a cross-species conserved protein at ever higher levels of TTR lead to ever longer lives and less disease over time. So logically, small molecule stabilization from these data is the safest approach.
Finally, the [logician] might look at price only to discover that Attruby has the lowest price point. We believe given all of that, the choice is clear. We apply similar reasoning in other competitors' faces like achondroplasia.
Our final constraint is that each program we work on should be NPV positive to ensure firm level sustainability. We use all available levers during the R&D stage to optimize NPV, including time, cost, cost of capital, and probability of technical success. The better our model is generating economic value from projects, the further we can push into markets where others cannot extract adequate value in addition to being a better owner of obviously NPV-positive projects.
The fact that we will spend well under $100 million per program to get each one of our potential blockbusters from the preclinical stage through proof of concept, sets us up well for future growth that is economically attractive.
Okay. So that's our overall objective function with its intended constraints. You heard the first and most important frame that we used to think about the business, which is NPV. There are other frameworks that we also use to look at the business: understanding the business by stage and capability, research, development and commercial; understanding the business in the context of the overall ecosystem; and understanding the business program by program.
Using the buy stage framework first, and as I mentioned earlier, we are pleased with the ongoing progress of our commercial launch and the building of a sustainable competitive advantage there, which means, of course, that our group is able to extract more profit from the asset than another would be able to. I've also touched already on our ongoing development wins.
On Discovery, our bread and butter, we continue to advance programs in genetic dilated cardiomyopathy and ADPKD. We also hold significant stakes in BridgeBio Oncology Therapeutics and GondolaBio. In the latter, we expect Phase 3 data in our EPP program later this year, and we expect to generate up to six development candidates in 2025.
From an ecosystem framing, the substrate from making genetic medicines remains incredible. We see that in the progress Gondola is making and more broadly with the depth of genetic disease starting points being produced and accessible at low price points.
Finally, at a program level, Matt will have more to say about our commercial launch of Attruby. Our goal there, as a reminder, is $4.3 billion in peak year sales or about 30% of a $15 billion marketplace. That gets delivered against approximately $380 million of spend on the brand per year.
Almost 25% of current spend is on further research development activities like ACT-EARLY, which we think can continue to improve our medicines positioning and its ability to help patients in later years. The product of this spend also includes salient results like our variant data, where we obtained a hazard ratio of 0.41 with a p-value of less than 0.02 in the sickest of patients. And new work we are doing regarding Afib, which is an emerging marker of disease progression, the first results of which we plan to present at ESC later this year.
For infigratinib, a first-in-class oral FGFR3 inhibitor in development for both achondroplasia and hypochondroplasia, the pivotal PROPEL 3 Phase 3 is fully enrolled, and we expect last participant last visit by the end of this year. We have also reached regulatory alignment with the FDA on our clinical development plan for infigratinib in children with achondroplasia from ages zero to three, and we expect to initiate clinical development in this important age range by the end of the year. Excitingly, we have also enrolled the run-in for our Phase 2 hypochondroplasia trial well ahead of benchmarks.
For Encaleret, a negative allosteric modulator of the calcium sensing receptor, our Phase 3 CALIBRATE study is fully enrolled. We expect last patient last visit and top-line results in the second half of this year. In parallel, Encaleret is also being studied in hypoparathyroidism, and we announced today positive POC data for Encaleret in key expansion indication. Preliminary evidence in the ongoing POC study has demonstrated that 78% of the first nine study participants were able to achieve normal blood and urine calcium levels within five days of Encaleret administration.
Moving to BBP-418, an oral first-in-class disease-modifying therapy in Phase 3 development for treatment of individuals living with Limb-Girdle muscular dystrophy type 2I. We have fully enrolled FORTIFY, a Phase 3 registrational placebo-controlled study, evaluating the safety and efficacy of BBP-418. The study includes a planned interim analysis of 12 months focused on assessing a surrogate endpoint biomarker, glycosylated alpha-dystroglycan to support accelerated approval in the United States. We anticipate top-line readout from that Phase 3 interim analysis second half of this year as well.
Finally, BBP-812 is an AAV9 gene therapy in development for Canavan disease, an ultrarare neurodegenerative disease that usually leads to death in the first two decades of life. Here, we are pursuing an accelerated approval approach using a single seamless registrational trial to bring this potential therapy to children with Canavan as quickly as possible. A meeting this month with the FDA reinforce the validity of our approach, which centers around the use of urine NAA in tandem with other clinical measures and the suggested BLA filing that we have laid out by end of 2026.
While this is not a very prevalent disease, we believe it's a great example of our model, targeting the disease at its source and operating leanly to enable us to go after a well-validated condition in an NPV positive manner.
Okay. That's the final framing. To wrap up my comments, BridgeBio is executing well and importantly possessed of a tremendously strong foundation for the future. Number one, an unmatched collection of late-stage genetic disease businesses with favorable economic prospects; number two, a cadre of outstanding managers that are dedicated to their specific assets business and to BridgeBio; number three, a diversity of stakes, including wholly owned assets and significant stakes in GondolaBio and BridgeBio Oncology Therapeutics; number four, first choice ranking with many academics, one seeking a partner to discover and develop new medicines; and number five, a culture that is distinctive for most biotechs I have seen and that is decentralized independent thinking and live the value that every minute count for the patients we serve.
We're excited to work with you, our investors, to continue to build this company and to keep you up to date on our progress for patients.
With that, I'll hand it over to Matt to walk through Attruby's commercial performance in more detail.

Matthew Outten

Thanks, Neil. To add to your comments, the launch of Attruby is off to a strong and encouraging start. Let me walk through some of the highlights in terms of what we are seeing out in the marketplace and what we think is driving the rapid momentum we've built in just a few short months.
The first highlight is the early uptake across all major prescriber and patient segments. As shared in our press release, 2,072 unique patients have received a prescription for Attruby through April 25, and 756 unique healthcare providers have written at least one prescription. This early adoption spans all physician segments, including large academic centers, regional amyloid clinics, high-volume heart failure specialists, and community cardiologists.
Importantly, we're seeing Attruby across the full spectrum of patients, wild type and variant, newly diagnosed as well as switches from partial stabilizers. The fact that these different patient types are all gaining timely access and that prescribers are already writing for multiple patients gives us confidence that we're building a strong foundation for Attruby.
So let's discuss what is driving the uptake. It comes down to strong clinical endpoints paired with our transparent patient-first support programs. Starting with the clinical data, Attruby is the only therapy for ATTR-CM that has demonstrated a separation from placebo as early as three months.
No other medicine has demonstrated that and it's not just about efficacy. Attruby also positively impacts KCCQ scores, which directly correlate with better quality of life for patients. That's resonating deeply with physicians who want to make a meaningful impact on their patients' daily lives and patients who want to keep their functional activity levels.
Second, let's look at hospitalization rates. Attruby is the only ATTR-CM therapy to demonstrate 50% relative risk reduction in cardiovascular hospitalization rates. This includes a statistically significant reduction in composite of mortality and hospitalization in the varying ATTR-CM population, a subgroup widely regarded as among the most difficult to treat. This was highlighted in the recent variant subgroup data presented at ACC.
And third, affordability. Attruby is the most cost-effective therapy in ATTR-CM available, 10% less expensive than tafamidis and 50% less expensive than vutrisiran.
It's not just about the [whack] price though. Attruby has a free trial program for all patients regardless of insurance status and lifetime free drug for patients who participated in our pivotal trials. That matters to physicians, patients, and payers, especially when coupled with the three-month onset of treatment effect and 50% reduction in cardiovascular hospitalization at 30 months. No other ATTR-CM therapy checks all of these boxes.
BridgeBio has a commercial model that is different and it's working. Attruby will be followed by three additional commercial launches in 2026 and '27. What really differentiates BridgeBio though is how we bring products to market. There are no convoluted value-based contracts, no vague promises of future rebates contingent on volume thresholds. What we offer is simple, transparent, and built around the people who matter most, patients and their care teams. And we're hearing from the field that this clarity paired with strong clinical data is helping accelerate adoption.
And once an HCP decides to prescribe Attruby, we make it easy to get the medication to patients. Patients can receive a treatment within 48 hours. We have two world-class specialty pharmacies in the Attruby network and also allow physicians to fill prescriptions in their own in-house pharmacies. All of this investment is paid off. We are gaining share in the crucial first-line setting, and our conversion to paid rate and time to pay prescription is well ahead of industry benchmarks.
Looking towards the future, our focus heading into the rest of the year is as follows: continue marching towards our long-term goal of [30%] to 40% share of the ATTR-CM market, and increased share in the critical first-line setting, which is a leading indicator of launch success. While these early signs are encouraging and they reflect not just the strength of the product, but the preparation and the commitment of the broader BridgeBio team, we are also excited about what's ahead and remain focused on reaching as many patients as possible as quickly as possible.
With that, I'll turn it over to Tom for a review of the financials.

Thomas Trimarchi

Thank you, Matt, and good afternoon, everyone. Q1 2025 marked BridgeBio's first full quarter of net product revenue from the Attruby US commercial launch, major milestones for the company and a significant step forward in our evolution into a fully integrated genetic medicine business.
I'll now walk through the financial highlights for the first quarter of 2025. Please note that our commentary on today's call will focus on GAAP financial measures, unless otherwise indicated. Total revenues were $116.6 million for Q1 2025 and consists of Attruby net product revenue and license and services revenue. Attruby net product revenue was $36.7 million, driven by strong demand across all major prescribers and patient segments. License and services revenue was $79.9 million in the quarter, primarily driven by the recognition of the $75 million regulatory milestone related to Beyonttra's EU approval. Also in Q1, we received Beyonttra approval in Japan, for which we expect to recognize a $30 million milestone in the second quarter.
Total operating expenses for the first quarter of 2025 were $218.4 million (sic - see press release, "$221 million") compared to $210.2 million (sic - see press release, "$210.8 million") in the same period last year. This increase reflects our continued investment in the Attruby brand and our advancing late-stage pipeline. Included in our total operating expenses was $29.4 million of stock-based compensation expense compared to $28.9 million in the first quarter of 2024. Looking forward, we expect only modest growth in quarterly operating expenses for the remainder of the year with an offset to total cash burn provided by Attruby sales in the US and Beyonttra ex US.
R&D expense for the first quarter of 2025 was $111.4 million compared to $141 million in the same period last year. This decrease was largely due to the strategic carve-out of our oncology business and early-stage research programs allowing us to focus resources on the Attruby launch and late-stage pipeline. SG&A expense for the first quarter of 2025 was $106.4 million compared to $65.8 million in the same period last year. This increase was driven by the full scale commercial rollout of Attruby, including field team deployment, payer engagement, and patient support infrastructure.
Restructuring expense for the first quarter of 2025 was $0.6 million compared to $3.4 million in the same period last year. We ended the quarter with $540.6 million in cash and cash equivalents, which does not include $105 million in regulatory milestone payments anticipated in Q2 for ex US approvals of Beyonttra.
We believe we are well financed for the continued execution of the Attruby launch and deliver on key milestones from the pipeline this year. We look forward to sharing additional commercial updates throughout the year and the top line data from our three Phase 3 programs over next year with ADH1 and LGMD2I in the second half of 2025, achondroplasia in early 2026.
With that, I'll turn the call back to Chinmay.

Chinmay Shukla

Thank you, Neil, Matt, and Tom. I'll now hand it back to the moderator to open the line for questions. (Event Instructions)

Question and Answer Session

Operator

(Operator Instructions) Salim Syed, Mizuho.

Salim Syed

Great. Congrats on the quarter guys and congrats also on your first earnings call. Maybe just one for Neil or Matt here. Obviously, the quarter came in healthier than I think people had thought going into the print. And I appreciate the commentary that you provided, Matt, on some of the dynamics there. But any sort of granularity you can provide on the tailwind and which you really deem that's working well for you here? Thank you.

Neil Kumar

Yeah, maybe I'll kick it off. Thanks, Salim. It's probably too early for some of the higher cost commercial tactics that we've invested in to show ROI right now. So hearteningly, I think a lot of the demand we're seeing to date really is a product, number one, of the differentiated clinical efficacy we have, as a reminder, and you know this the earliest separation and it's a point estimate that we've seen in the field at three months, 42% relative risk reduction against ACM and CVH in 30 months. Again, the best point estimate we've seen at 30 months, coupled with that 50% reduction in hospitalization, which turns out to be a huge leading full measure for patients who both want to live longer, but also live healthier. So I'd say that's point number one.
Point number two, as you saw as well from the Pfizer call this morning, continued market growth, right? We're one-fifth diagnosed in this space, some 50,000 or so patients diagnosed. We think there's 250,000 to 300,000 in the US alone. And so physician education, coupled with there being a variety of therapeutic interventions now available, I think, is driving that growth. So that, I think, is another tailwind.
And then the third is the access programs that Matt talked about. The team, I think, has done a terrific job of ensuring that patients when they are prescribed Attruby can get the medicine and stay on the medicine as long as they need to. So those would be the three salient drivers.
I'd say the final thing there's a little bit of what a physician described to us the other day is Karma. Obviously, we're the only sponsor in this space that gave free drug for life for their trial participants. Unfortunately, others decided not to. We're also the only sponsor in the space running a primary prevention study, which I think many physicians view as the ultimate in trying to catch patients in this mass action condition as early as possible to do as much as we can for conditions.
So those types of things, I think, over a long period of time, will stand us in good stead as a sponsor here in a competitive space.
I don't know, Matt, if you'd add anything?

Matthew Outten

No, I think in this -- the people, we've spent a lot of time putting the team together both internal field to make it as easy as we can for both prescribers and for patients. And I think you're seeing the good results of that.

Salim Syed

Great, thanks guys. Congrats again.

Operator

Tyler Van Buren, TD Cowen.

Tyler Van Buren

Hey, guys. Congrats on the stellar Attruby result as well and the ongoing progress of the pipeline. So again, the $37 million of the Attruby sales far exceeded expectations. So when you say that the paid conversion rate is well ahead, can you help quantify that? Was the time to pay quicker than a month for some patients? And how much stocking was there in the quarter?

Chinmay Shukla

Yeah. Hi Tyler, great to hear from you. I'm going to pass it on to Matt to comment more on conversion.

Matthew Outten

Yeah, thanks for the question. We're really happy with how conversion is tracking, and that's for both free trial to paid and also commercial prescriptions to paid. Everything regarding conversion is consistent or better than historical launches that we've studied.
I will just point out Attruby trial acts like a normal prescription, HCP writes it, the pharmacy processes it and the patient gets it. And we designed our network specifically with conversion in mind, and that's what makes the access so easy. Our goal remains the same, 30% to 40% peak share. It takes up three to six years usually to hit. We're hoping we can do that a little bit faster.
In regards to your channel and inventory question, I mentioned we do have a limited distribution network that allows for very frequent ordering and it allows our customers, our distributors to have just-in-time inventory. So there's no need for them to really hold large quantities. And so typically, I would say that this small group of distributors holds about one to two weeks of inventory.

Thomas Trimarchi

Hi Tyler, this is Tom. Let me just put a finer point on the inventory question. As I mentioned in the prepared remarks, the sales in the quarter were primarily driven by demand. So we've seen only a minor impact on inventory on total sales in the quarter. So really demand-driven here.

Chinmay Shukla

Yeah. Thanks, Tyler. I know you had another question. So happy to answer more about this or go to your next question.

Operator

Mani Foroohar, Leerink Partners.

Mani Foroohar

Hey, guys. Congrats on the quarter. Clearly blew out expectations despite having shown pretty good scripts repeatedly. And I want to dive in on the script numbers. I'm looking at the incremental scripts on a weekly basis through that first update on January 10, or in the 60s per week? And then through the update you gave on an incremental basis on February 17, that was running north of 100 scripts a week.
And again, running through from 12 and [four] weeks into launch and 22 weeks in the launch, i.e., from February 17 to April 25, you're still running at about 100, 109 script per week as reported.
I know it's just math and then a lot of nuance that goes into script reporting. Could you give us a sense of what the tariff on velocity of new patient scripts that you're seeing right now? And sort of what is that -- so what is the kind of direction of travel out there? And I have a follow-up question.

Matthew Outten

Great. I can take that. Thank you for the question. I mean I think starting out, the thesis really -- again, it remains unchanged. TPL levels go up with Attruby and it's the only year complete stabilizer on the market.
When we sort of take that thesis and then dive into, okay, well, what's happening and then how do we think that's going to impact things going forward? But on the over month growth rate in the treatment-naïve section has been very strong, and that's been across all segments. So this is in the large centers, this is in the community. That's across all types of patients, variant wild-type, there hasn't been a sort of one area or another that's done better. We've sort of seen this across the board.
And so then when we look at sort of the two groups, we have the treatment-naïve patients, that's our focus. And that will continue, we believe, to grow over time as it has been. Then you have the switch patients. Of course, when we launched, we had 100% of the switch share because we were the only option you could switch to as new -- now with new entrants in the market, that's going to evolve over time because they are now more choices. And so I think the data and how we report will evolve over time as well based on that. But that's kind of where we are and how we see it moving forward.

Mani Foroohar

Great. That's helpful. And I have sort of a non-TTR question to everyone's surprised. When you think about Limb-Girdle data coming later on this year, which, obviously, we've been discussing a number of calls. This is not the first time you guys have brought it up.
We talked about it at my conference [a couple years] running, about the filability of that data set or whether a later dataset in the same study will be required. Do any of the changes of FDA concern you around your ability to file on a biomarker? Do you think you have to show a distinct level of clear clinical improvement on a non-biomarker/functional basis? Where are we in terms of the viability of that biomarker for Limb-Girdle?

Neil Kumar

Yeah. I can take that. Mani, we haven't met with the agency of late on the LGMD2I program, but we have had some close to 10 meetings now over the course of the last month as it pertains to either pipeline at Gondola or a pipeline here at Bridge, probably the latest meeting was in and around the Canavan program.
And I have seen nothing but, I would say, a positive inclination toward trying to get first-in-class medicines that target path a mechanism like our drug for LGMD2I onto the marketplace as quickly as possible to benefit the children that are suffering from these conditions. And so I don't think the rather clear guidance that we've gotten from the agency to date in and around filability, around glycosylation of ADG is going to change. I really don't.
I have been on the record saying I think it's going to be a problem if we go the right way and hit our primary endpoint on ADG, but we go the wrong way on all clinical measures. Obviously, I don't think that's going to be the case based on what we observed in Phase 2, which was albeit an open-label study against natural history where we saw improvements in measures of ambulation and other clinical outcomes.
So I do believe these things will move toward the positive or at least a few will move toward the positive, obviously, modified North Star, North Star which is historically but the gold standard in these conditions. It's all noise over the course of the first 12 months. So what is the point estimate goes one way or the other. I think natural history has made that very clear. And that is why we're running the confirmatory trial.
This is effectively a nesting trial design that goes on for another 2.5 years post the readout later this year.
So I mean, long story short, we continue to believe that is going to be an approvable endpoint in terms of ADG glycosylation increase.

Operator

Tyler Van Buren, TD Cowen.

Tyler Van Buren

I just had a second question that I meant to ask. But just the ADH1 and Limb-Girdle Phase 3 is reading out during the second half of the year, clearly level high probability success. So can you -- it would be great to hear you elaborate on why investors should be excited about and more importantly, focus on those opportunities beyond the ongoing Attruby launch. What do you think the magnitude of those opportunities could be?

Neil Kumar

Yeah, good question, Tyler. As I was suggesting, we continue to be heartened by both the clinical operational positioning of LGMD2I, ADH1 and our achondroplasia trials as well as the potential to help a broad swath of patients. And I think from an investor standpoint, one asked to consider the sheer size of these marketplaces, LGMD2I as we've discussed, some 7,000 to 8,000 patients between the US and EU. That's a substantial market size as compared to any of the other muscular dystrophy programs that you see out there at the price points that are attended in the space.
And with ADH1, a rather much more prevalent condition, maybe 10,000 to 12,000 patients in the United States alone as suggested by statistical genetics methodology, some 4,000 or so already identified to date, that's going to be really a program associated with the market build and finding new patients. And we've already shown that we can do that in some of the sequencing efforts we've undertaken within the non-surgical [hypopara] community where we're reliably finding something like 20% to 25% of patients actually harbor the gain of function mutations in the calcium sensing receptor.
So I think two very exciting commercial opportunities, two very exciting opportunities for first-in-class medicines for patients there. And then I don't think I need to belabor the achondroplasia hypothesis where we feel we have an exciting oral best-in-class, potentially best-in-class option that could provide differential safety differential legacy because it targets this well-described condition at its source, driving differential both changes in growth and then also importantly, impact on parameters that this community care is a great deal about like proportionality and the like. And you know the size of that market from the (inaudible) launch that's ongoing. So I think all three very exciting opportunities.

Operator

Biren Amin, [Equity Research Health].

Biren Amin

Congrats on the quarter and really good launch out of the gate. I guess my question is what's resonating with health care professionals as it relates to the Attruby launch? And what are the biggest hurdles that you're seeing for adoption?
And then maybe a second question, what was the gross to net for the quarter? And any impact that you've seen from the Part D redesign?

Chinmay Shukla

Hi Biren, thanks for the question. I'm going to pass it on to Matt to discuss the HCP piece, and then I'll throw it to Tom to discuss the [question on that] piece.

Matthew Outten

Yeah, thanks. And I guess, there's sort of two parts to this. The feedback from the physician segment has been positive as we've discussed. Our messaging around, we call it, the [342.50], but that ability to separate as early as three months and getting results around the hospitalization all-cause mortality that we've described.
Physicians want to see drug work really fast, and they want to be able to tie it to hard outcomes. Of course, patients do, too. So this is what gives people confidence. And so those messages have been resonating extremely well and I think that's resulted in physician trying Attruby, but then also then repeating it, right? Those are the reasons that you sort of try a medication and then when you see how well people are doing on it, then that encourages you to try it again. So we've seen a lot of repeat prescribers across a lot of the different segments as well.
And I don't think our expectations were otherwise are going to change anytime soon. We have very strong data package, and we also have very strong programs to help patients get on the medication once that prescription has been written.
And then I'll pass it to Neil to add on.

Neil Kumar

Yeah, maybe I'll just elaborate on that for a second before I throw it over to Tom. I think the ever-increasing availability of data like most recently, Biren, I think we've talked about the variant data. The fact that you could achieve a hazard ratio of 0.41 with statistical significance in that relatively small subpopulation. And as someone mentioned earlier, the sickest of subpopulations continues to reinforce that differential levels of stabilization can lead to ever better outcomes. And we're starting to find that that's resonating.
We've got a bevy of Serum TTR associated literature coming out suggesting that ever higher levels of Serum TTR correlate with ever lower levels of downstream hospitalization and mortality. The connecting of the dots between ever better stabilization and all of these downstream outcomes, I think, is what's starting to resonate with the physician community on top of what Matt suggested the backbone, which is the 342.50.
Tom, do you want to talk about [GKN]?

Thomas Trimarchi

Yes, sure. On gross to net, specifically. So as we said before, the way to think about this is the floor is going to be the mandatory IRA rebate of 20%. And on top of that, you're going to add something like you'd see in other categories for contracting is not really happening as that's what we're seeing here. I would say, given where we are in launch early innings, we should expect some variability here quarter on quarter.
This quarter, gross to net trended slightly favorable versus what we were expecting. We also saw a slightly lower use of our first month free program versus what we were expecting, and we saw slightly lower use of our patient assistance program and what we're expecting.
All these three things together actually converge and cause slightly better net revenue per unit than what we were expecting, but we expect all of this to normalize throughout the course of the year.

Chinmay Shukla

Just to add that the results are reflective of strong underlying demand for Attruby and execution of our commercial team. And as Matt mentioned, not a lot of inventory or anything like that.

Operator

Cory Kasimov, Evercore.

Cory Kasimov

So it's great to see Attruby's off to such an impressive start, and you kind of alluded to this in a prior response, but now that you're in the market for over a quarter. How are you thinking about new patient starts for the category going forward? I know previously, you've talked about numbers like 2,000 to 3,000 restarts per quarter, but that's already looking pretty conservative. So any kind of new color there would be appreciated.

Neil Kumar

Yeah. Cory, thanks for the question. I think you're kind of thinking about it like we're thinking about it. It does seem to keep going up every quarter. And if you look historically, that's different. I think it is ramping a bit faster, but that also makes sense because you're getting new products in the market. So the more companies that launch a product into a space that creates a higher share of voice.
And I think that gets people educated either to go get screened or for physicians to think to themselves, I mean, if you're a cardiologist and you have [test pet] patients, and you're not thinking to yourself, hey, some of these must be ATTR-CM patients. All of these companies are discussing and educating, talking about it, it gets people looking. And if you look, you find it, it's -- it's not that uncommon.
Most cardiologists have some patients that need to be treated. So I think that we don't see that stopping anytime soon. the market could easily be a $20 billion market, and we're not there yet. So there's still a lot of patients who are out there who have not been diagnosed but I think you're going to see continued high numbers of people being diagnosed now with that interest is just continuing to grow.

Chinmay Shukla

Yeah. And Cory, just to add one last thing. A lot of the new diagnosis is coming from the high-volume heart failure clinics that Matt mentioned in his marks. And obviously, an oral small module stabilizer is a great fit for those patients.

Operator

Greg Harrison, Scotiabank.

Greg Harrison

Congrats on the huge start to the launch. So in our initial modeling conversations with you guys, our takeaway was that your expectation was for initial uptake to primarily or almost exclusively from newly diagnosed patients. But to get to the revenue number you've reported, you have to get most of them by our math. So assuming that's not the case, is this a function of much larger market growth than you expected? Or are you getting a large percentage or maybe even most of your patients as tafamidis switches. And if that's the case, how do you expect this trend to evolve from here?

Chinmay Shukla

Hi, Greg. Thank you so much for the question. So I think as we have said consistently, our focus at launch has been the treatment-naïve market. Very early on, we got a few more switch patients than we expected, but that started to normalize. Focus continues to be new treatment naive patients, and I think Matt mentioned in his remarks that there we are seeing consistent monthly growth gradually.
In terms of what's driving the number, I think it's sort of all of the above, right? I think it's a little bit of the market growth, obviously, strong demand and strong conversion. Maybe I'll throw it on to Matt, and he can talk a little bit more about the factors driving conversion and the market size.

Matthew Outten

Yeah. No, I think you hit it well, Chinmay. I don't know that I would add that much. It's a little tricky when you try to figure out who a switch patient is. They can -- they look like a new patient most of the time. So I think it's a little -- be a little careful trying to determine who's the switch and who's new.
Our focus is on the newly diagnosed. We do see switch patients come in, and sometimes we can tell that they're a switch patient. Other times, it's not clear. But I think as you think about the rest of '25 moving into '26, I think the market continues to grow. It's been growing double digits now for quite a long time. And this past quarter, one of the best we've seen.
I would not expect that to disappear anytime soon. There will be switch patients who want Attruby, and there will be a lot of newly diagnosed patients that want Attruby for all the reasons we've discussed, whether it's the data itself, the programs we offer. I think we're very optimistic about all of that.

Operator

Paul Choi, Goldman Sachs.

Paul Choi

Congratulations on knocking it out of the park in your first quarter here on the launch. I want to shift gears for a minute, maybe just ask a policy question, which is to think about as Attruby growth and scale over the coming years here or this year and next year as well as we start to get sales from Europe [from Bayer] and on Beyonttra and AstraZeneca in Japan. Could you maybe just help us think through where your IP is on most out at is sort of the tariff implications and just sort of the royalty streams that you'll be getting from your ex US partners and just sort of how that ultimately affects your margin and your sort of profitability profile? Any color there or directional guidance would be helpful. Thanks.

Thomas Trimarchi

Hey, Paul, thanks for the question. This is Tom. Yes so as Neil indicated in his prepared remarks, we're fortunate to have very little impact from the tariff discussions that are ongoing. We've done a pretty deep dive on this. As you know, the pharmaceutical has been exempt from the reciprocal tariffs but we also looked at the [AEP or IPA] and what's been said in public around the potential 232 tariffs affecting the industry.
When we put all that together, based on our supply chain, we see a very, very minor impact. That's because Attruby made here in the USA. And then we're, of course, an American company, and we have all our IP domicile here in the US. So overall, very minor impact to the business.
I'm not sure I understood the question on the royalties and how that relates, but that's off the top line revenue number. So obviously, we're getting money coming to us as before. Any implication on tariffs that would be on their end, but maybe I didn't understand the question.

Paul Choi

No, that makes sense on the ex US business.

Operator

Anupam Rama, JPMorgan.

Anupam Rama

Congrats on the quarter with Attruby. I wanted to just pop in with a very quick pipeline question, so you shared some data today on the chronic hypoparathyroidism indication. So what gets you excited about this opportunity, particularly you talked about, Neil, from an NPV perspective. How does that all fit in?

Chinmay Shukla

Thanks for the question. We're going to drive it to Neil to talk about the NPV, and then Ananth can talk more about the data and our exciting plans for the Phase 3 in HP.

Neil Kumar

Yeah. I mean, from an NPV standpoint, I think you know that this isn't an exciting extension population, quite a bit larger than ADH1 itself with actually a pretty reasonable price point as well given where [Ascend] has ended up pricing their medicines. So there's a variety of different ways for us to take advantage of the opportunity now that many of the oral competitors have fallen by the wayside.
I'm going to actually pass it over to Ananth to talk a little bit about the exciting data that we just posted.

Ananth Sridhar

Great question. Thanks for your interest in this program. We -- so as you mentioned, we reported data from the first nine participants with postsurgical hypoparathyroidism that were treated with Encaleret, normalized blood and urine calcium concomitantly in 78 of these participants and serves to be important oral option for these patients seeking to resolve calcium homeostasis. So we think that this could be a treatment changing or paradigm-changing treatment and we will advance development towards registration for this program.
And in terms of the NPV or the market opportunity, like Neil mentioned, this is about a seven to eight times larger marketplace than the ADH1 market alone. So it could grow and expand the presence of Encaleret as we continue to investigate molecule.

Operator

Ellie Merle, UBS.

Ellie Merle

Congrats on the quarter. Curious what you're seeing so far in terms of commercial trans since Amvuttra's approval, you have a few good experience now with this so far. So I mean, I guess, specifically, was the rate of new unique patient prescriptions consistent with what you saw in February and March? Should you see an increase by April in the broader prescriber base? Or have you maybe seen a dip in the rates of the new [eugenic] patients starts as with the launch of a competitor?
And any sort of high-level commentary on how you're thinking about positioning? Are there certain segments where you see potential greater uptake or advantages in terms of your use?

Matthew Outten

Sure. This is Matt. Thank you. So the second half of your question, the audio was a little garbled. So let me answer the first one, and then if you want to repeat the second one, happy to address that as well.
Your first one regarding Amvuttra, there's definitely a place for lots of choices in this market. And I think as a company, we're obviously happy when patients have additional choices in terms of where Amvuttra is going to be placed, they seem to be earmarked for mixed phenotype at the moment, that's probably 10% of the overall market. Their variant data wasn't stat sig and they're very expensive. So it's twice as expensive as Attruby right now. And they have to compete, obviously, with our 340.25, which has been pretty successful.
So I don't know whether that's going to land for them. I think they have to figure out their pricing. If you're going to charge double, you need to have better results and I think you can ask them to talk about that. I'm sure that they'll have opinions on that. Right now, it's early, but we're not seeing a lot of uptake outside of the mixed phenotype.

Ellie Merle

Got it. And then just maybe this was a part of the question that broke off. I mean, if you can't hear me. But just in terms of the rate of unique patient prescriptions, I guess, have you seen any change in that since the approval of Amvuttra. So for instance, if you saw a dip in the rate of new unique patient prescriptions in April or as saying now that you have a broader prescriber base, you've seen a similar rate in new patient prescriptions or even higher? Thanks.

Matthew Outten

Yeah. So the April data, I probably wouldn't be able to comment on -- I mean, they were sort of about two weeks in Q1 and now we picked up some data. We see some of the same stuff that you guys see. The trouble is even -- it's buy and bill. And so they're trying to convince a community physician to put out over $100,000 per injection, the vitamin A part is cheap.
So from a cost perspective, that's fine, you still have to take that every day. But that out of pocket for the doctor, they have to cash flow that. So they have to put that money out and then they have to wait to get reimbursed.
Well, if you start stacking up a lot of patients, that's a lot of money, and it gets pretty expensive. So we haven't seen it yet. It doesn't necessarily mean it is or isn't happening. I think you'd have to ask them. Maybe they can do what we did and throw out some early numbers on what the first month of launch looks like.

Operator

Jason Zemansky, Bank of America.

Jason Zemansky

Great. Congratulations on the quarter and thanks for taking our questions. I wanted to return to the question of segment growth for Attruby, if I may. It sounds like you expect the contribution from switches to slow at some point. But what does that look like over the near term? I mean, do you have a sense of how quickly you may be going through a bolus of, I don't know, refractory patients versus those, as you mentioned, are looking for a stronger stabilizer because they believe in the better outcomes over time?

Chinmay Shukla

Hey, Jason. Thanks for the question. I think that high level, I can say a couple of things and then Matt going to add more details. But as we have said all along, we're not seeing any bolus or anything like that. I do think that the focus of our launch is treatment naive and where we're seeing consistent monthly share growth, and we expect that to continue.
We had 100% share in the switch population and obviously, that's going to evolve now that there's a competitor. So that's sort of how we're thinking about it. Obviously, it's very early to say, and we look forward to seeing how the next quarter goes.

Matthew Outten

Yeah. And I'll just add. I mean, I agree. We didn't see a bolus. I mentioned earlier, it's a little tricky to absolutely know if someone is a switch or a newly diagnosed. We don't spend a lot of time sort of thinking about it from that perspective. If patients want to get Attruby, we try to make sure they can get it for whoever they are newly diagnosed or switch.
In terms of what that looks like over time, I think that's hard to predict. You can take the number of patients on tafamidis. You can add on a progression rate of whatever you think is correct. And then kind of model that out over time. I think that's probably the best approach if any.

Operator

There are no further questions at this time, and that concludes our Q&A for today. I will now hand the call back over to the company. Please go ahead.

Chinmay Shukla

Thanks, everyone, for your questions today. We appreciate your interest in BridgeBio and look forward to updating you again next quarter.

Operator

This concludes our conference for today. We thank you for participating and ask that you please disconnect your lines.