Greetings, and welcome to the Rigel Pharmaceuticals Financial Conference Call for the First Quarter of 2023. At this time, all participants are in a listen-only mode. A brief question-and-answer session will follow the formal presentation. As a reminder, this conference is being recorded. It is now my pleasure to introduce our first speaker, Ray Furey, Rigel's Executive Vice President, General Counsel, and Corporate Secretary. Thank you, Mr. Furey, you may begin.

Hello. Welcome to our first quarter and 2023 financial results and business update conference call. The financial press release for the first quarter of 2023 was issued a short while ago and can be viewed along with the slides for this presentation in the News and Events section of the Investor Relations site on rigel.com. As a reminder, during today's call, we may make forward-looking statements regarding our financial outlook and our plans and timing for regulatory and product development. These statements are subject to risks and uncertainties that may cause actual results to differ from those forecasted. A description of these risks can be found in our most recent Annual Report on Form 10-K for the year ended December 31, 2022, and subsequent filings with the SEC including our Q1 quarterly report on Form 10-Q on file with the SEC. Any forward-looking statements are made only as of today's date, and we undertake no obligation to update these forward-looking statements to reflect subsequent events or circumstances. At this time, I would like to turn the call over to our President and Chief Executive Officer, Raul Rodriguez. Raul?

Thank you, Ray, and thank you everyone for joining today. Also with me today are Dave Santos, our Chief Commercial Officer; and Dean Schorno, our Chief Financial Officer. Now beginning on Slide 5, we are pleased with our strong start to 2023 based on our first quarter, which was marked by significant progress on our commercial business. This positions us well for continued growth in the remainder of 2023 and beyond. Our first approved product, TAVALISSE and ITP had the highest number of bottles shipped to patients in clinics in a quarter since launch in a meaningful quarter-over-quarter sales growth. Despite the typical Q1 challenges such as those associated with reimbursement, we were able to provide continued momentum for TAVALISSE, which we believe is a testament to our commercial team's commitment to patients with ITP. We are also pleased to see the continued expansion of TAVALISSE in patients worldwide, most recently with the launch of TAVALISSE in Japan by our partner Kissei, congratulations to them. In addition to TAVALISSE, we are executing on our key launched initiatives for REZLIDHIA in relapsed or refractory AML. Our commercial team has been driving awareness with key physician groups and will continue to do so with a particular focus on AML specialists at key academic institutions. Beyond our commercial focus, we're looking to expand our hematology-oncology business further through our own internal development-stage programs, as well as in-licensing opportunities, similar to our approach with REZLIDHIA. I will provide further updates on the recent progress on our strategy in these efforts later on in this presentation. With that, I'll turn the call over to Dave for an overview of the quarter. Dave?

Thank you, Raul. Now I'd like to take a few minutes to discuss our early progress with REZLIDHIA in the first three months of launch and then transition to our continued growth of TAVALISSE during our record Q1. On Slide 7, you will see our FDA-approved indication for REZLIDHIA, which is for adult patients with relapsed refractory acute myeloid leukemia with a susceptible IDH1 mutation as detected by an FDA-approved test. Moving to Slide 8, I would like to briefly review our view of the currently eligible patient population for REZLIDHIA. The American Cancer Society estimates that more than 20,000 patients will be diagnosed with AML in 2023. And of those patients, our research showed that whether patients are treated with intensive therapy or not most are refractory to treatment or relapse within two years. Specifically, 6% to 9% of patients have the IDH1 mutation, and we believe we have a near-term opportunity to impact the lives of around 1,000 new mutant IDH1 patients in the relapsed refractory setting each year. Slide 9 depicts our first three months of progress on our journey towards that near-term opportunity to bring REZLIDHIA to those 1,000 mutant IDH1 relapsed/refractory AML patients. We shipped a total of 111 bottles of REZLIDHIA to patients in clinics since late December, with 109 of those bottles shipped in Q1. This represents new and refill bottles to an estimated 32 patients across 29 unique accounts or prescribers. Considering approximately a quarter of those 1,000 mutant IDH1 relapsed refractory patients were available in Q1, we believe REZLIDHIA was used in more than 10% of our target patient population last quarter. During the first quarter, we sold an additional 113 bottles to our distribution network, resulting in Q1 2023 net sales of $1.5 million. Since our product became available on December 22nd, we have sold 177 bottles of REZLIDHIA resulting in $2.3 million in launch-to-date net product sales. Moving to Slide 10, our team has continued to make excellent progress on our three priorities of driving awareness, maximizing access, and optimizing the REZLIDHIA experience across both academic and community leukemia treaters. First, on the left, we continue to drive awareness among the more than 1,000 leukemia treaters by strengthening our medical evidence, broadening our KOL support, and refining our materials and messaging. The medical evidence with REZLIDHIA is strongly supported by both the NCCN guidelines recommendation in relapsed refractory disease with the IDH1 mutation, as well as the recent publication of our phase two pivotal data in blood advances. Our KOL support has also been broadening through different scientific forums where leukemia treatments are discussed and physician awareness and appreciation of REZLIDHIA’s clinical data will further be supported with last month's launch of our Speakers Bureau. We have already planned several promotional speaker programs for Q2 and beyond. And importantly, along with this medical evidence and KOL support, our marketing materials and messaging continue to be refined. In fact, we've just launched our Transform Your Expectations campaign to HCPs and our sales force has already been trained to appropriately differentiate our product through the delivery of our compelling efficacy and safety messages in every interaction with their customers. So we now have a full suite of materials and resources to deliver the message, identify appropriate patients, and support physicians and patients as they begin REZLIDHIA. In maximizing access for clinicians and patients, we made great progress in Q1. Our RIGEL ONECARE Hub processes patient enrollments as quickly as possible to ensure our limited pharmacy network can provide timely shipments for patients. We have confirmed published coverage for over 90% of Medicare lives and coverage parity to other relapsed/refractory targeted agents in the majority of National Commercial payer accounts. We continue to deliver our access messages to clinicians, and we particularly encourage them to enroll their patients in RIGEL ONECARE to maximize responsiveness for both patients and clinicians who want to try REZLIDHIA. Lastly, on the right, we have made solid progress in optimizing the REZLIDHIA experience across both academic and community leukemia treaters. Through Q1, three-quarters of REZLIDHIA bottles were ordered through our direct channel by 21 unique accounts that are mostly academic institutions. More than half our bottles were direct shipments to academic institutions and 22% were shipped to community accounts. Overall about two-thirds of our REZLIDHIA business so far is in the academic setting, and community usage makes up the other third. This is a solid start on our journey of optimizing experience across the community treaters in both the academic and community settings. We will continue to focus on driving awareness in both segments of our business to continue to expand the number of prescribers and ordering accounts. Moving to slide 11. After our experience during the first full quarter of launch, we believe now, more than ever, that REZLIDHIA has the potential to address many key patient and HCP needs in relapsed/refractory AML. It is a promising new treatment targeting mutant IDH1 that has shown impressive durable responses in patients who have failed previous therapies. And as more clinicians review the demographics of our relapsed/refractory patient population in our pivotal cohort and put that together with the compelling efficacy of overall response in nearly half of patients, duration of CRCRH of 25.9 months, and an estimated 18 months survival rate for CRCRH of 78%, they increasingly see the value of an agent like REZLIDHIA in their treatment armamentarium. Combining that efficacy with a well-characterized safety profile without the requirement for cardiac monitoring becomes even more compelling to adopt REZLIDHIA in their mutant IDH1 relapsed/refractory AML patients. Overall, we continue to see exciting potential to become a market-leading treatment in mutant IDH1, relapsed/refractory AML and are looking forward to continuing to execute the launch plan. My thanks to the entire team for all their efforts in Q1 with REZLIDHIA and I look forward to providing you additional updates as we move forward in our launch. Now onto growing sales of TAVALISSE and ITP. I have a few brief comments on our continued momentum with TAVALISSE in Q1. On Slide 13, you will see our TAVALISSE FDA-approved indication, which is for adult patients with chronic immune thrombocytopenia or CITP who have had an insufficient response to a previous treatment. Moving to Slide 14, I'm very excited to announce that we achieved another new quarterly high in Q1, shipping 2,256 bottles to patients in clinics, representing 23% growth over Q1 of 2022. This continued robust growth was again driven by strength in new patients starting TAVALISSE. Despite the typical headwinds during Q1, with coverage in reimbursement for all such specialty drugs, we are off to a solid start with TAVALISSE. We have grown bottles shipped to patients in clinics another 3% over the record quarter we had in Q4 2022. For Q1, we achieved net sales of $22.3 million, $6.1 million more than the same quarter last year, representing a 38% year-over-year increase. We are incredibly pleased with how we ended 2022 and are starting 2023 with continued strong year-over-year growth in ITP sales. We will continue to focus on targeted clinicians to identify appropriate patients who can benefit from TAVALISSE to grow our new patient starts beyond the record levels we saw in 2022. I am grateful for the dedication and great collaborative work demonstrated every day across our entire team to continue our ITP growth with TAVALISSE, while successfully launching REZLIDHIA. Finally, on Slide 15, an update of our global expansion of TAVALISSE. Most recently, in April, our partner Kissei announced the launch of TAVALISSE for the treatment of chronic ITP in Japan. We remain committed to continuing to impact CITP patients around the globe with continued expansion of TAVALISSE's commercial footprint through our partners. Thanks for your attention. And I will now turn the call back over to Raul to provide a brief update on our development progress. Raul?

Thank you, Dave. I will briefly summarize our pipeline efforts. On to Slide 17, you can see an overview of our ongoing programs; we are focused on growing our heme/onc business, starting with our internal development programs. Our ongoing Phase 1b Study of R289 in patients with lower-risk MDS continues to progress well. And notably, we have completed enrollment in the first dose group and are currently enrolling the second cohort. We also believe fostamatinib and olutasidenib have potential in other diseases beyond their approved indications. We are currently evaluating several options. In addition, we are actively looking at new in-license opportunities to further bolster our heme/onc business. More opportunistically, our partner Eli Lilly is advancing R552, a RIPK1 inhibitor towards a phase 2a study in rheumatoid arthritis and we look forward to that study starting this quarter. Moving on to Slide 18. We are keenly focused on evaluating fostamatinib and olutasidenib in additional indications beyond their approved indications. As part of this process, we are engaged in several discussions with KOLs and with regulators across multiple indications, as well as conducting market research to help inform our plans going forward. We look forward to providing you additional updates on these initiatives later on in 2023. Regarding our business development efforts relating to in-licensing new assets, we are continually evaluating assets that are synergistic with our existing heme/onc business infrastructure, and that are complementary or adjacent to our already approved products. We are focused on programs that are in late-stage clinical development in review for potential approval or in early stages of launch. We believe that our development capabilities and commercial infrastructure can grow our business with internal programs, as well as being the commercial partner of choice for in-license heme/onc opportunities. That concludes the development summary, and I'll turn the call over to Dean.

Thank you, Raul. I'm on Slide number 20. For the first quarter of 2023, we shipped 2,281 bottles of TAVALISSE to our specialty distributors resulting in $31.4 million of gross product sales. 2,256 bottles of TAVALISSE were shipped to patients at clinics, while 25 bottles increased the levels remaining in our distribution channels at the end of the quarter. For the first quarter of 2023, we shipped 113 bottles of REZLIDHIA to our specialty distributors resulting in $1.8 million of gross product sales; 109 bottles of REZLIDHIA were shipped to patients at clinics while four bottles increased the levels remaining in our distribution channels at the end of the quarter. We reported net product sales in TAVALISSE of $22.3 million in the first quarter of 2023, a 38% increase compared to the same period in 2022. We reported net product sales from REZLIDHIA of $1.5 million in the first quarter of 2023. Our net product sales from TAVALISSE and REZLIDHIA were recorded net of estimated discounts, chargebacks, rebates, returns, co-pay assistance and other allowances of $9.5 million. For the first quarter of 2023, our gross-to-net adjustment for TAVALISSE and REZLIDHIA was approximately 29% and 20% of gross product sales respectively. Before we move on from net product sales, let me review our expectations for the second quarter of 2023. We're pleased with the strength of our business and expect to see continued growth in total net product sales as bottles shipped to patients and clinics continue to grow in ITP as we successfully continue our launch of REZLIDHIA. Incrementally, we currently expect the gross-to-net adjustment in the second quarter of 2023 to be approximately 30% for TAVALISSE and approximately 20% to 22% for REZLIDHIA. As is typical with a newly launched product, our gross-to-net adjustment is dependent in part on our distribution channel mix. We will continue to provide updates as our launch phase progresses. On to the next slide, in addition to net product sales, our contract revenues from collaborations were $2.3 million in the first quarter of 2023. Contract revenues and collaborations consisted of $1.6 million in revenue from Grifols related to the delivery of drug supplies and $700,000 in royalty revenue. Moving on to cost and expenses, our cost of product sales was approximately $977,000 for the first quarter of 2023. Our cost of product sales for the quarter were inclusive of a 15% royalty on our REZLIDHIA to net product sales and amortization of intangible assets. Total cost and expenses were $38.8 million, compared to $43 million in the same period for 2022. The decrease in cost and expenses was primarily due to decreased research and development costs related to the Phase 3 clinical trial of fostamatinib for warm autoimmune hemolytic anemias, the Phase 3 clinical trial of fostamatinib in high-risk hospitalized patients with COVID-19 and the IRAK1/4 inhibitor program. Lastly, we ended the quarter with cash, cash equivalents, and short-term investments of $58.7 million. Incrementally in March of this year, we accessed an additional $20 million term loan through our credit facility with MidCap Financial Trust. With that, I'd like to turn the call back over to Raul. Raul?

Thank you, Dean. As we reviewed on this call, we had an exceptional first quarter and a very strong start to the year. We look forward to continuing to drive momentum in TAVALISSE sales in ITP both in the US and globally with our partners. While executing on the launch of REZLIDHIA in relapsed/refractory AML and identifying ex-US collaborators for this product, for the remainder of ‘23, we look forward to keeping you updated on R289 Phase 1b study and our evaluation of new potential opportunities for both fostamatinib and olutasidenib, as well as our partnered programs in our ongoing business development initiatives. So with that, thank you for your interest in our progress in the first quarter. And we will now open the call to your questions. Operator?

Our first question comes from Eun Yang with Jefferies. Please go ahead with your question.

Thank you. So a question on the partnered program with Eli Lilly, with the RIPK1 inhibitor. So, initially, I think you mentioned Lilly was interested in psoriasis, but now they are going into rheumatoid arthritis. So can you kind of comment on why the partner changed the indication there? And I understand that Lilly has the rights to CNS indications. Do you know when they might be going into CNS indications such as ALS or multiple sclerosis? Thank you.

Eun, thank you for your question. I can answer that. Lilly has always been interested in the broad applications of the RIP1 inhibitor program across immune indications including RA, psoriasis and others. So it's never been a single focus of one indication and always with the idea of going after more than one hopefully multiple areas. In psoriasis and RA, we're always in that mix. I think their decision to go forward in RA makes a lot of sense. The opportunity is very good there. The need is great, especially as you know some setbacks with other mechanisms that have occurred. And so, I think it's a very exciting opportunity for them and they were clearly excited by it and are prioritizing RA. That's not to say that they won't pursue other indications in sequence, though. It just hasn't been revealed when they might start those. But we're looking forward to the RA trial starting. It's a good robust trial. An area, like I said, a good medical need. And in addition, because there are so many of these trials, you can compare cross trials to a degree and get a judgment on how the product might perform in other areas. So, we're looking forward to their starting that trial very shortly. This is very important. And you're absolutely right on the second question. CNS, Lilly has rights to the CNS program. We've delivered to them a basket of RIP kinase inhibitors that crossed the barrier. And they're deciding to move forward with one or multiple of those into various CNS indications. We're not able to disclose what their priorities are in those areas, but we will in the future.

Thank you. And I have just one more follow-up. So, in the first quarter, the cash you burned was about, low-double-digit million dollars. So, how do you see your quarterly cash burn going forward? Probably question to Dean. Thank you.

Hi, Eun. So we ended the quarter with $58.7 million of cash, and we noted in our last call that achieving cash flow breakeven was a priority for the business and that we're comfortable with it. Our cash position at year-end, as we just reported the results for Q1, is viewed in change as a result of these results. So we continue to be pleased with our progress towards breakeven and we will continue to move in that direction.

So, when do you aim to become breakeven?

We haven't provided top-line guidance which would enable us to crisply answer that question. On our last quarterly call, we kind of walked through some mechanics of our view of the growth in revenues, as well as the $160 million of operating expense and the reduction in operating expense from 2022. So we see a path towards breakeven. We haven't been precise, again, because of the lack of guidance that we've provided on the top line.

Thank you.

Thank you, Eun.

Our next question comes from the line of Yigal Nochomovitz with Citi. Please proceed with your question.

Hi, team. This is Carly on for Yigal. Thanks so much for taking our questions. First, on TAVALISSE, wondering if you can elaborate on any specific drivers behind the sequential growth you saw in the first quarter? And if you can just give an update on the progress with penetrating the earlier lines of ITP therapy. That would great. Thank you.

Thank you, Carly. I'll ask Dave to comment on that.

Sure. Great question, Carly. We were very pleased, of course, with our TAVALISSE growth in Q1. We had the highest new patient starts in any Q1 that we've had since launch. And so that's really what’s continuing to drive our growth. And what's driving that it's, we're continuing to get that message out there to as many clinicians as possible. Our sales force is really doing a terrific job of targeting ITP prescribers out there. Whether virtual, live, or email follow-up, they're doing it all and activity is helping. I think the additional kind of boost we got in terms of access with a newly approved product like REZLIDHIA; even though many of the clinicians they call on because we're calling on over 6,000 targets for ITP don't treat AML, it gives them the opportunity to tell them about REZLIDHIA, but also reinforces that TAVALISSE message. So I think that's exactly what happened. And we're just quite pleased with the performance in Q1.

Thanks. That’s helpful. And then just one follow-up. Wanted to ask about where you stand with respect to partnering REZLIDHIA ex-US? And if the strategy there will be to find one global partner for all ex-U.S. rights? Or if you would do maybe a series of deals with regional players like you did with TAVALISSE?

Thank you for that. I could try to answer that. So, as you may know, we received global rights with REZLIDHIA when we in-licensed it. Obviously, our commercial interest ourselves in the U.S. is what's paramount and where we've launched the product. But outside of the US, there is a very good opportunity for REZLIDHIA for the same reason, same application in relapsed/refractory AML. So, we're in discussions with a variety of partners. Some more PAN country, some more specific to some territories that have interest in REZLIDHIA. The discussions are ongoing in terms of what the financial terms of course. But I think importantly here, there is so much opportunity with this product that we'd like to have the partner contribute clinically, too. And clinically in terms of maybe replicating what we've shown here already and providing additional data to help position the product even better or possible clinical trials in areas beyond our approved indication of relapsed/refractory AML. So those discussions are part of the process because we'd like to have a partner that is truly a partner. And that we can work with in order to coordinate how we expand the understanding and that’s the value of this product globally in the US as well.

Very helpful. Thank you for taking our questions.

Our next question comes from the line of Allison Bratzel with Piper Sandler. Please proceed with your questions.

Hi. Good afternoon guys. Thanks for taking my questions. First, just on the REZLIDHIA prescriber base, I think I heard you mention about 29 prescribers to-date for REZLIDHIA. So I guess, did I hear that right? And what should we be thinking about as a reasonable target for prescriber breadth during the first year of launch? And then, I think you also had mentioned that two-thirds of users has been in the academic setting, one-third in the community. Is that in line with your expectations? Or could you just frame how you expect that to evolve over the course of the year?

Sure. Dave?

Sure. Great question, Allison. I'll start with your last question or last piece first in terms of what we expected. I would say that we are very pleased with just three months and about a week of having REZLIDHIA available. We're getting what we think is very good traction in the mutant IDH1 relapsed/refractory space. As I said in my prepared comments, we estimate that the bottles shipped to patients in clinics, along with the incidents of newly diagnosed mutant IDH1 patients in the relapsed setting, we're capturing more than 10% of eligible patients. So, we do expect that as awareness continues to grow, we will continue to increase our patient numbers. And of course, then the carryover of refills should really begin to kick in and impact the demand growth. All that said, I am really proud of the team for the way they've constantly looked at our business and any opportunities to accelerate growth, and they did exactly that in Q1 and came up with a solution to accelerate our REZLIDHIA growth in key leukemia treatment centers. I think this is critical to your question about academic centers. We want to do that while maintaining our current growth trajectory with TAVALISSE. So we made the decision to create a specialized institutional team that will focus on key leukemia treaters and primarily academic accounts. The great thing about this is we were able to redeploy the open territories we had to support it, and it resulted in us having about 49 representatives, and we now have 49 representatives who will continue to have both TAVALISSE and REZLIDHIA in their territories and eight new institutional representatives who will focus on REZLIDHIA in key leukemia centers across the country. So that's a total of 57 sales representatives. So with a net add of two positions, it gives us a much more focused presence in these important leukemia centers critical for growth. As you did hear correctly, we're seeing about two-thirds of our sales coming from the academic setting, and we think this focus with this institutional team will clearly create accelerated growth there, which will also have a downstream effect in the community. I hope that answers all your questions, Allison. And if you have follow-up studies just let me know.

Yeah, no, that's helpful. And then, maybe just one more for you guys on ITP and on TAVALISSE as kind of a follow-up on a prior question. I'm just curious kind of what you see as the key factors in sustaining the nice momentum in new patient starts longer-term? Just I am curious if you could talk to your sense that the biggest remaining growth levers you have to pull in ITP just in the out-years. Any color there would be helpful. Thanks.

Yeah, I mean, we are starting a number of new patients on TAVALISSE, Allison, as you've heard. There is plenty of opportunity to continue growing those new patients on TAVALISSE because every day patients fail other therapies or need a new therapy. And I think that's really the importance of it. As I said before, we've got 6,000 some targets for TAVALISSE. So, we still have a long way to go and making sure all of those clinicians give TAVALISSE a try, especially in a second line or earlier line patient. So that's going to continue our growth. I mean, that's why we really think the institutional team made a lot of sense to us. We don't want to disrupt that getting that awareness message out to our targets for TAVALISSE.

One of the things that we have seen post-pandemic is just more opening of various centers and being receptive. I think patients for a couple of years there were less constant in their houses and now are much more open to considering that there is a better therapy out there that I'd like to avail myself there. We want to make sure that TAVALISSE is a part of that consideration. Because if doctors are aware of our data, they tend to write substantially more, and obviously if they're not aware of our data, they don't write very much at all. So, our goal is simple: to tell a concise coherent story to those doctors so they consider our product. I mean, generally, we do pretty well when we do that. So I think that's what we're looking forward to continuing to raise awareness of this product and our data supporting it.

Got it. Thank you.

Our next question comes from Kristen Kluska with Cantor Fitzgerald. Please go ahead with your question.

Hi, everyone. This is Rick on for Kristen. Thank you for taking our questions. Maybe first, can you talk a little bit about the potential opportunity for olutasidenib in the maintenance setting, as you mentioned on the pipeline expansion slide knowing that physicians often try to get AML patients to bone marrow transplant. Do you have a sense of what percentage of IDH1 positive patients undergo transplant followed by some form of maintenance therapy?

Dave, do you want to take a stab at that and then I’ll add some commentary?

Yeah. Great question, Rick. When we're speaking about maintenance therapy here, we're talking about maintaining a response in a patient who would have gone through, let's say, venetoclax aside from a regimen, or some other regimen. We're not particularly talking about patients who have been to transplant. Because obviously that, when you do intensive therapy with the aim of getting patients to transplant, we think it's about 40% of the market. But of that, probably another 30% end up getting treatment like venetoclax, just because it's an easier kind of outpatient treatment. So the actual number of patients getting intensive therapy is, I think, continuing to actually go down, and it's probably now less than 30% of the market. When you consider the challenges of getting a match, being able to garner a complete response in induction therapy, all of those things, it ends up being a relatively small number of patients going to transplant. To us, that's not where the market is in maintain response after transplant. We've looked at that, we think there's a greater opportunity in those patients who are receiving outpatient therapies like venetoclax who might need to be maintained in their response. I hope that makes sense.

Yes, I've got one more for you if we may. You also talked about the pivotal phase 2 olutasidenib data published in blood advances. Can you talk a little bit about how having this publication in hand is influencing the awareness in addition to, of course, the data on the label when you were going in and talking to these physicians?

Sure, Rick. Happy to take that one, as well. That's a great question, and I'm thrilled to be able to answer because when that publication came out, first of all, it did increase awareness among hematologists who treat leukemia—it was important to them. More importantly for us, the marketing team did a fantastic job creating a visual aid just around that publication. When you look at their new core visual aid, it has now been rolled out with our new campaign, Transform Your Expectations. We really talked about a number of key messages that were in that publication, which are important to get across. Number one is that almost half the patients responded, like I said in my prepared remarks. Previously, we have been focused on the 35% CRCRH rate with those patients. But really when you add in other responders, you get the 48% overall response rate. So that was a key piece that we've now been able to really talk about a lot. In addition to that, other than aside from our duration of response, that publication also contained in it that estimated 18 months survival rate for CRCRH responders of 78%. That is a clear differentiator for REZLIDHIA and it does definitely ring true to leukemia treaters, particularly in the relapse setting when they are just not used to that. I mean, you're talking about median survival in many relapsed/refractory studies of less than four months. So, to hear that 78% of those CRCRH responders are alive at 18 months—that’s a very important message for us. Those two things really helped us to get that efficacy message out there and truly differentiate REZLIDHIA. But definitely that publication helped us a lot. And that just came out as you know, this quarter, or in the first quarter.

Great. Okay, thank you for taking our questions.

Our next question comes from the line of Kalpit Patel with B. Riley. Please proceed with your questions.

Yeah, hey, good afternoon. Thanks for taking my questions. Maybe one starting for REZLIDHIA. Is there any additional color on the prescribing behavior for selecting REZLIDHIA versus tips hobo in the real world? And maybe how is that choice being made for the 29 prescribers that started REZLIDHIA?

That's a great question, Kalpit. I wish I could be more precise. As you can see in our slides, much of our business is being directly shipped to accounts. So we don't have that prescriber insight that we would have if they're filled through the specialty pharmacy network. Our team goes back and follows up. But I can't really say what are the drivers specifically for those who prescribed it, for using it, other than they really have looked at the data. They believe it's compelling and they decide they're going to start a patient on REZLIDHIA. We have had one institution already started more than actually three patients on REZLIDHIA in the relapse setting and they have made a conscientious decision based on reviewing the data that it will be their therapy of choice. I think it's still early. We'd love to provide more specifics on why people are choosing it. But all I could say now is that anecdotal evidence is clinicians see the value of a long duration of response. Of course, when they respond, a high percentage of patients survive for a long period of time, so that's why they're choosing it.

But more to come, I think it’s very early. It's hard to be specific at this point. We're just getting data in and evaluating it.

Okay. And are you seeing—again, this might be early—but are you seeing any combination based maybe off-label uses with azacitidine and then to your earlier setting or do you not have the data for that?

We don't have data for what they've used it with. It’s—and we would only have that for those patients who go through our RIGEL ONECARE Hub. For others, we just get the diagnosis of AML. So, we don't have if clinicians are using it with HMAs, it’s specifically azacitidine. But we suspect that that probably is going on out there. It's just difficult for us to see in any of our data.

Okay, okay. Got it. And then one last question on fostamatinib for chronic graft-versus-host disease. We have been hearing on our end that there's additional interest from at least the KOL community for this program. So, I'm curious if there is any progress on that and whether you have decided if this might be a 2023 event for that opportunity?

Yeah, very good question and thank you for your interest. We're very interested in GVHD. We're looking at that area very closely. As I said earlier, we are speaking with KOLs in the area, doing some market research, speaking with regulators, as well because we'd like to have a nice package when we come to you and say here's what we want to do for this indication or that indication, of which GVHD is one of those. I look forward to later this year, coming back to you with specifics on what we want to do across these indications. We could share that with you at that point in much more detail. But we are doing a fair amount of work in this area, and we think it's pretty exciting.

Okay, fantastic. Thank you very much.

There are no further questions in the queue. I would like to hand the call back to Mr. Rodriguez for closing remarks.

So, thank you, everyone. I'd like to thank you for joining the call and your interest in Rigel. I would like to also thank our employees for their continued commitment to improving the lives of patients. We look forward to updating you on future calls. This quarter was, I think, a fantastic quarter, a great start to the year. The rest of the year we have equally exciting things to update you on across a range of different products and indications. So, I very much look forward to doing that in the not too distant future. So, thank you very much.

Ladies and gentlemen, this does conclude today's teleconference. Thank you for your participation. You may disconnect your lines at this time and have a wonderful day.