Greetings, and welcome to X4 Pharmaceuticals third quarter 2022 conference call. At this time, all participants are in a listen only mode. A question answer session will follow the formal presentation. As a reminder, this conference call is being recorded. It is now my pleasure to introduce your host, Dan Ferry from LifeSci Advisors. Please begin.

Thank you, operator. And good morning, everyone. Presenting on today's call will be X4's Chief Executive Officer Dr. Paula Ragan and Chief Medical Officer Diego Cadavid. We will also hear briefly from the company's new Chief Commercial Officer Mark Baldry and company board member and incoming interim Chief Medical Officer Dr. Murray Stewart. Following prepared remarks, we will open the call to your questions and will be joined by Chief Financial Officer Adam Mostafa, Chief Scientific Officer Art Taveras, and Chief Operating Officer Mary DiBiase. As a reminder on today's call, the company will be making forward-looking statements regarding regulatory and product development plans as well as research activities. These statements are subject to risks and uncertainties that may cause actual results to differ from those forecasted. Description of these risks can be found in X4's most recent filings with the SEC, including this quarter's 10Q, which is expected to be filed after market close today. I'd now like to turn the call over to X4's President and CEO Dr. Paula Ragan. Paula?

Thanks, Dan. And thank you everyone, for joining us on the call this morning. As we shared in the press release this morning, and as Dan just mentioned, Diego will be transitioning out of his role as Chief Medical Officer and becoming a senior medical consultant to X4. And our board member, Dr. Murray Stewart, former Chief Medical Officer of GSK and Rhythm Pharmaceuticals, will be joining X4 as interim CMO. At the end of today's call, Murray will say a few words of introduction. As we welcome new team members, we are extremely excited to share the progress that we've been making as we sharpen our focus of the company with a mission to develop therapeutics to treat the broad patient population with chronic neutropenic disorders, including our first potential indication of WHIM syndrome and where we believe there's a significant need for an oral efficacious therapy with low treatment burden and good tolerability. With no oral therapeutic approved for approximately 50,000 chronic neutropenia patients in the US, we believe that mavericksphore [ph], if approved, could represent a new opportunity to transform the treatment landscape and create a new standard of care. Today, the focus of the call will be to provide updates on mavericksphore's progress in our global pivotal phase three trial in WHIM syndrome and to highlight how we are getting appropriately prepared to ramp into commercial launch. Mavericksphore is being studied in an ongoing phase three for the treatment of WHIM syndrome, which is a population of people with severe neutropenia as well as other immune system deficiencies. WHIM syndrome is considered a combined immunodeficiency because patients with WHIM not only have profoundly low neutrophil counts, but also low Lymphocyte and monocyte counts, and sometimes low antibody production, which is referred to as Hypogammaglobulinemia. We believe…

Thank you, Paula. I'll now briefly review the study design of our four WHIM global registrational trial, assessing mavericksphore as a potential treatment of WHIM syndrome. As Paula mentioned, the design is a randomized placebo control and double blinded study. We completed enrollment in Q3 of last year over enrolling the trial with 31 patients from 12 countries. We have now completed the last patient last visit for the placebo controlled 52 week period and are diligently working towards database lock. The status inclusion criteria required that all patients enrolled had a confirmed absolute neutral field count or agency less than or equal to 400 cells per microliter during screening. For the 31 patients enrolled in the trial, the average pretreatment agency was 220 cells per microliter, an indication of the severity of current neutropenia that characterizes WHIM syndrome. Recall that an ANC less than 500 cells per microliter is considered severe neutropenia, indicating that this population was severely neutropenic as they entered the study. Importantly, almost half of the patients enrolled were pediatric between 12 and 17 years of age, which supports the potential for us to receive a rare pediatric disease priority review voucher or PRV upon approval of mavericksphore of significant potential value to the company. At the end of the placebo control portion of the study, all participants were eligible to roll over into the open label extension or OLE study. Notably, more than 90 percent of eligible participants elected to continue on and receive mavericksphore treatment in the OLE. We are continue to collect data from this ongoing portion of the trial. Safety from the trial has been monitored regularly by a data safety monitoring board, which has endorsed the continuation of the study without any protocol modifications due to safety of all [tolerability]. As…

Thank you, Diego. We believe mavericksphore is well positioned to make history by being the first treatment specifically developed for the treatment of WHIM Syndrome. Based on our discussions with the agency, we expect our label to be focused on those aged 12 and older diagnosed with WHIM syndrome. It has been an ongoing commitment of X4 to support education, awareness, and ultimately the diagnosis of WHIM syndrome in the medical and patient communities. As previously described, the diagnosis of WHIM requires a clinical assessment consistent with one or more of the various phenotypes of the W, H, I and M in a setting of combined immunodeficiency that is neutropenia, lymphopenia, monocytopenia and or Hypogammaglobulinemia, and can potentially include bone marrow examinations, as well as genetic testing assessments and family history information. We've been investing in a breadth of activities to support the clinical and patient community as outlined here, and I'd like to highlight a few more recent efforts. We've begun collaborating with a bone marrow pathology expert with the potential to establish a Myelokathexis Center of Excellence. In the future, we envision such a center could be a place where physicians can send bone marrow samples for a second opinion, to be analyzed by those experienced with myelokathexis to aid in a potential diagnosis of WHIM syndrome. Additionally, we have hired a patient education liaison, a medically trained professional who can compliantly engage directly with patients and their families to support the potential for genetic testing amongst individuals or kindred members within the same family. And finally, we are excited to support the International Patient Organization for Primary Immunodeficiencies, or IPOPI, in establishing a global registry for people with WHIM syndrome. By bringing together those working across a breadth of existing immunodeficiencies, including a patient foundation, patient community…

Thank you, Paula. I'm really pleased to be here, and I'm looking forward to digging in. This is such an exciting time at X4, and as you've just outlined, a great opportunity for me to help support free commercial efforts and hopefully the commercial launch of mavericksphore and its first indication. I spent much of my career focused on launching innovative therapeutics that were able to transform the lives of patients around the world who are living with rare diseases. And I've joined X4 because I can clearly see the potential of mavericksphore to not only become the first therapy for people with WHIM syndrome, but also to become a new standard of care for those with chronic neutropenic disorders who face considerable challenges with currently available therapies. So, I'm really looking forward to working with you and the whole X4 team.

As are we, Mark. Thanks. Next slide, please. As you would expect, preparing the product, the market and the company for commercialization to ensure mavericksphore treatment reaches patients with WHIM syndrome is well underway in anticipation of the phase three data and leading up to planned 2024 launch if approved. Here, I want to share some additional ongoing activities and near-term planning and highlight several spokes to building the commercial wheel and getting it rolling. I've already mentioned the team of people we have in place out in the field, PDLs and PELs, and in the home office. In this pre commercial phase, and under Mark Baldry's leadership, we intend to rate build the commercial team as we enter into the next phase of preparation. These customer facing people are actively engaged with healthcare professionals, patients and patient communities to raise awareness of WHIM, educate on recognizing and diagnosing the disease, and communicating the potential of mavericksphore through medical channels. We have also conducted primary payer research with U.S. and European payers to understand the issues and opportunities to gain market access. We've begun to identify the capabilities we need to build and define the full spectrum of healthcare value that Mavericks may demonstrate and ensure access for patients. On the manufacturing front, registration batches have been completed. The key requirements, core components and partnerships are well underway to ensure a stable and efficient commercial supply chain and specialty distribution network. And lastly, from a marketing standpoint, we have secured conditional approval of a brand name with the FDA, an exciting step for mavericksphore. Additionally, we have conducted early healthcare professional market research focused on targeting the physicians most likely to have a WHIM or a potential WHIM patient, introduced tools available to the patient and HCPs on disease awareness,…

Thanks, Paula. I'm really pleased I'm able to support X4 at this time and look forward to working with the whole X4 team as we're poised to unblind the phase three data and advance as quickly as possible to an NDA submission. Having been part of the [export] [story] for several years now, I'm really excited to help the company bring an important new treatment option to patients.

Thank you, Murray. And with that, why don't we now open the call up for your questions. Operator?

[Operator Instructions] The first question is from Stephen Willey with Stifel. Please go ahead.

Thanks for taking the questions and appreciate the update and the overview ahead of data. I know that it was mentioned, I guess, the average ANC count of patients pretreatment. Do you happen to know also what proportion of patients pretreatment were severely lymphopaenic as well in terms of what the average ALC was?

I think my understanding is they are quite severely lymphoenic as well. The actual number, I think, is escaping us at this moment, but I believe we published in an abstract back in April some of the details. So, we're happy to take that offline with you and make sure you get that information.

No, that's fine. I can dig that up. and then have you been able to see just the blinded infection rate that's been observed in the trial to date? Just curious as to whether or not that's information that you're privy to, and I guess whether or not that's kind of tracking to expectations?

So we are able to look at overall blinded safety related events, which, of course, infections are one of them. I'll refer to Diego to provide any more context on that.

This is something that the team has monitored, as Paula said. And, yeah, we have seen infection events. Of course, we're completely blinded. We have a very rigorous process of central adjudication, and they are actually working out to finish that, and that will poise the trial to help us. You know, it's one of the metrics of clinical benefit that we are tracking, obviously, among several of others. But, yes, I think we've seen a good number of infections that we believe is consistent with what we expect now that the pandemic impact has been somehow mitigated.

And then just, lastly, maybe a little bit of a bigger picture question, but I know that you're kind of now talking about the addressable patient opportunity as being, I guess, in the 50,000 range. I know that you had previously indicated or estimated that the proportion of patients, I think, in the US, who were on chronic GCSF was maybe somewhere in the 2,500 range. How do you think about the disconnect between those two numbers? How do you close that gap in chronic neutropenia specifically? And then how does that 50,000 number factor into your thoughts around this initial mavericksphore price set?

Yes, a couple of things. Steve, thank you for highlighting that disconnect. So, the 2,500 number that we threw out previously was really based on registry data. So, of course, it doesn't really capture the average utility out in what I would call the commercial setting, number one. And it's very difficult. So GCSF has used intermittently in many patients. So how you define chronic, semi chronic is another challenge for us as we consider the number of patients on G, and also to highlight, only about half of them can tolerate it based on our patient surveys. Of course, we don't even know what we're not capturing underneath that approach as well. So, I hear you on the disconnect. I'm actually not worried about the overall market size for folks with chronic neutropenia. It's a massively underserved market with a treatment that is incredibly painful to take on a daily basis. So, we think there's certainly a lot of opportunity. To further uncover these patients who really need something new.

And then just how that factors into how you're currently thinking about a pricing decision on mavericksphore with the understanding that you're still a ways away from having to make that decision?

I mean, I think we've done enough price sensitivities even around WHIM to appreciate that even numbers in the 10s of thousands are relatively consistent with ultra-orphan pricing around WHIM. You know, there's examples of this in the field already with the vertex CF molecules certainly getting into the 10s of thousands of patients that they serve and commanding the price points of that particular treatment. So, I don't think there's really a sort of deep consideration that we need to make as we think about the broader kind of neutropenia markets.

The next question is from Eva Privitera with Cowen. Please go ahead.

Hi, thanks for taking our questions, and congrats on all the progress. Can you remind us of the powering assumptions for this war [ph] WHIM trial? Are there any updated assumptions, given the high enrollment numbers?

As we said during the call, we use the changing the TAT ANC observed in the context of the phase two trial for powering the phase three trial. So, based on the increasing the target ANC that we observed in phase two, of course there was a range, but we took that into consideration and concluded that to have at least 90 percent power, we needed around 18 patients minimum. As you heard, we ended up enrolling 31. We have excellent retention. So that's why we said earlier that right now we believe our power on the primary endpoint is greater than 95 percent, and the same goes for the top secondary endpoint. As well as that, it's really important to show that we are impacting not only neutral fields, but also Lymphocytes, because that goes to the core of this disease.

And what's the latest estimate on the prevalence of WHIM? Based on all the research you've done, are there any updates on new genetic variants or anything?

No, I mean, we continue to feel very comfortable with guiding to 1,000 or higher with WHIM syndrome. It's actually fascinating, some of the publications that will be coming out or have come out around additional genes even beyond CXCR4, such as CXCR2. So, we think we're just at the very beginning, our physicians are incredibly excited about potentially supporting their approach to diagnosis, of which, obviously, genetics is a component. And we'll keep you updated as we refine that any further.

The next question is from Mayank Mamtani with B. Riley Securities. Please go ahead.

Thanks for taking our questions, and look forward to working with you. Just maybe first question, as I was comparing between the baseline characteristics for phase two and phase three, beyond having now a pediatric cohort, which you didn't have. Could you just give us a little bit more color on the clinical presentation of the patients that you have here in phase three versus the phase two? And just remind us, what presentation was required for all patients and baseline? And also, if you excluded any prior exposure to credit support or if you permitted any ongoing treatment for GCSF in the study, if you could remind that, that would be great.

I'm just going to a repeat your question back to you. I hope I got this right here. I think your fundamental question sounds like what's different or similar or different between your patient populations, between phase two and phase three, since we've included pediatrics in there. So, Diego can highlight that. And then I think the second element of that was around GCSF use and how was it addressed in the phase three. So, Diego, I'll turn it over to you for those two phase step questions.

So regarding the first question. So, phase two and phase three populations are actually quite similar in the sense that they're all required to have WHIM syndrome. All of them actually had a CXCR4 mutation. The pretreatment agency counts actually were almost identical. The main difference is that we open up phase three to pediatric 12 to 17, while phase two was only adults. You ask what type of clinical phenotype. As Paula mentioned earlier, WHIM comes in different ways. So, we did not restrict by whether they have the W or all four letters. They had to be clinically diagnosed with WHIM, genetically confirmed, and they had to have severe neutropenia, which they all had. So we feel that phase three pretty much follows phase two. You also ask about GCSF. GCSF is used mostly intermittently, it's not well tolerated. So, we only allow the use of GCSF as rescue therapy in WHIM phase three. And it's something that really the doctors don't like much. So essentially, we have mostly a mavericksphore placebo trial, randomized, fully blinded, very high quality that we're very proud of.

And just Diego, you might want to comment on the approach that we took to make sure we weren't confounding neutrophil counts with TAT ANC and GCSF use.

If somebody received GCSF as rescue [ph] therapy, we postponed the timing of the TAT ANC assessments to avoid the compounding.

And maybe just to clarify, any prior exposure to mavericksphore, and also thinking because there was one patient on your phase two, which had early rash, he had -- so would you include that also?

We did not enroll anyone in phase two who had been previously exposed to mavericksphore. And in terms of rashes or dermatology safety signals, we really have not seen much of that. I mean, we're blinded, but based on blinded assessment, we have not seen much.

Nor did we exclude anybody for that basis as well.

And then my follow up on the steps forward after the top line data. Could you just lay out between the December top line data and then the early filing of, excuse me, the NDA filing in early second half. What are sort of the activities that you'd undertake on the WHIM side, and then if there is any overlap you also talked to the regulators about chronic neutropenia negation with multi dose durability data becoming available there. Could you just kind of help connect the dots there, how the interactions progressed on these two fronts?

So, it sounds - you're trying to kind of piece together the various kind of evolutions of WHIM and CN and regulatory. So, we'll try to lay those out clearly. So, the phase three data will come in Q4. On average, it takes about six months to file an NDA, give or take. So that's where we're putting it in the early part of second half of 2023. We're in excellent shape there in terms of just moving it forward and, of course, working with the agency as closely as needed. The important thing around chronic neutropenia, of course, is the amended protocol has been completed. We're moving forward with operationalizing that, which always takes a couple of months of these sites. So, we think we'll have some early data in the extension study around durability in CM. Of course, the WHIM phase three will have a lot of durability data, given its one-year dosing course. So that totality of data will be useful as we go in to approach the FDA regarding a chronic neutropenia registration trial. So the timing isn't finely tuned, but we believe WHIM plus CM data plus regulatory conversations should be happening in the first half of next year to prepare us to then, of course, file the NDA on WHIM, and shortly thereafter complete that registration clarity and kick off advancing a CN phase three trial, subsequent to the NDA.

Great. Thanks for taking my questions, and it's been great, working with you, Diego. All the best for your next adventure.

The next question is from Trevor Allred with Oppenheimer. Please go ahead.

I just want to ask a question on Walden Strums. Any updates here on potential partnerships that might be developing? Thanks.

We'll come back and update as we make progress. We continue to focus on upcoming WHIM data and the [excitement] on [prog] neutropenia.

Anything else?

The next question is from RK with H.C. Wainwright, please go ahead.

And most of my questions have been asked. But I just want to have an idea of what sort of data would be presented at the top line announcement this quarter? And what else needs to get done in terms of analysis between now and your filing? I'm trying to get a sense, trying to figure out if there will be additional updates before you file the DLA.

So as you can appreciate, top line is typically the primary endpoint plus safety. However, we're adding our first key secondary endpoint in there to specifically highlight the unique approach of mavericksphore, the targeted therapy for all the combined immunodeficiency effects of WHIM syndrome. So we're looking forward to sharing a little bit more than usual. In terms of the totality of the data of the entire trial, of course, that's incredibly important to preserve for publication rights. So, we do think that we'll be having an update at a relevant medical conference via a publication, and we'll try to provide more guidance when we have clarity on that. And then, of course, I'll be rolling into our NDA submission early in the second half of next year.

And then as you stated in late summer that you're focusing on the chronic neutropenia and diseases at this point. When would be the next update on the chronic neutropenia study itself? And do you think we'll get additional clarity after we get through the four WHIM study or, you know, will there be any updates on those studies?

So we plan for additional data updates on the CN trial in the first half of next year. Again, we'll try to provide clarity under what format or possibly a medical conference. But it's an exciting trial to me moving forward quickly with and as we generate some interesting data under that, we'll take a cut and share it. Most importantly, I think for us, we really want to work with the agency, so it's really about the totality of data to support our regulatory conversations. We're all very bullish on moving this forward as quickly as we can to a CN registration trial. So, stay tuned and we'll look forward to providing those updates in the first half of next year.

And I know it's an exciting quarter, so good luck with everything.

Thank you. It is very exciting.

This concludes the question-and-answer session. I would like to turn the conference back over to Paula Ragan for any closing remarks.

Thank you so much for joining today. I did want to make one additional comment since it's now past 09:00 A.M. As you probably know, ASH 2022 abstracts were just published, and we're very happy to announce that our abstract on our phase one B chronic neutropenia study has been accepted for an oral presentation at this year's meeting. In addition, we've had several additional abstracts accepted for poster presentation, and these include two on chronic neutropenia, one on U.S. prevalence, and then the other on the voice of the patient, and one additional on the morphology of myelokathexis and WHIM syndrome. So, a very productive ASH for us. We look forward to seeing some of you in New Orleans in December. And with that, we're concluded, and I hope everyone has a wonderful day. Thank you.

This concludes today's conference call. You may disconnect your lines. Thank you for participating and have a pleasant day.