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Atara Biotherapeutics Inc (NASDAQ:ATRA)
Q3 2019 Earnings Call
Nov 8, 2019, 2:00 a.m. ET

Contents:

  • Prepared Remarks
  • Questions and Answers
  • Call Participants

Prepared Remarks:

Operator

Ladies and gentlemen, thank you for standing by, and welcome to the Atara Biotherapeutics Q3 2019 Financial Results Call. [Operator Instructions] After the speakers' presentation, there will be a question-and-answer session. [Operator Instructions]

I'd now like to hand the conference over to your speaker today Dr. John Craighead, Vice President of Investor Relations and Corporate Communications of Atara Biotherapeutics. Please go ahead, sir.

John Craighead -- Vice President, Investor Relations & Corporate Communications

Thank you, operator. Good morning, everyone, and welcome to Atara's third quarter 2019 conference call. On today's call, we plan to discuss our third quarter financial results, as well as recent clinical, operational, and strategic progress.

Earlier this morning, we issued a press release providing an overview of the company's third quarter 2019. This press release as well as an updated investor presentation are available in the Investors & Media section of atarabio.com.

I am joined on today's call by Dr. Pascal Touchon, President and Chief Executive Officer; Utpal Koppikar, Chief Financial Officer; and Dr. AJ Joshi, Chief Medical Officer. We will begin with prepared comments from Pascal, and then open the call for your questions.

We'd like to remind listeners that the company's management will be making forward-looking statements. Actual results could differ materially from those stated or implied by our forward-looking statements due to risks and uncertainties associated with the company's business. These forward-looking statements are qualified in their entirety by the cautionary statements contained in today's press release and the company's SEC filings. These statements are made as of today's date, and the company undertakes no obligation to update these statements.

Now, I'd like to turn the call over to Atara's President and Chief Executive Officer, Pascal Touchon. Pascal?

Pascal Touchon -- President & Chief Executive Officer

Thank you, John, and thank you everyone for joining us this morning.

Before we begin our discussion on our recent progress, I want to reinforce how proud I am of the advances we've made toward a vision of delivering an off-the-shelf, allogeneic T-cell immunotherapy to every patient in need at anytime. We know that life depend on us achieving this vision, and our team is strongly motivated every day to deliver meaningful results for patients and the company.

During today's call, we'll provide context surrounding our new strategic priorities, recent clinical and operational progress and upcoming milestones.

First, I would like to update you on Atara's strategic objective and priority, following the extensive review of technologies, assets, resources, and organization, that I have conducted during my first months as CEO. Objective, moving forward is to become the leading off-the-shelf, allogeneic T-cell immunotherapy company, transforming the life of patients with cancer, autoimmune and viral diseases.

We are planning to accomplish this objective over the next three years, by executing resolutely on four strategic priorities. First and foremost, file and launch tabelecleucel or tab-cel for patients with relapsed/refractory EBV positive PTLD in the U.S. and Europe, as well as develop tab-cel for other indications. Second, achieve clinical proof-of-concept with ATA188 or allogeneic MS specific EBV T-cell immunotherapy. Third, advance mesothelin programs with autologous ATA2271 and allogeneic ATA3271. And fourth, develop ATA3219 or allogeneic CD19 CAR T to clinical proof-of-concept in B-cell malignancies. In parallel, we will continue to leverage the capabilities and expertise of external partners for all autologous CAR T immunotherapy development.

Starting with tab-cel, we are very pleased to share exciting long-term outcome data for a multicenter expanded access program following acceptance of an abstract for presentation at ASH 2019. I would like particularly to highlight the long-term outcomes in a subgroup of 22 stem cell and solid organ transplant patients, with relapsed/refractory EBV positive PTLD treated with tab-cel. We would likely have been eligible for our ongoing Phase 3 study. These results demonstrate tab-cel was generally well tolerated with overall response rate of 55% in HCT and 82% in SOT patients. Estimated two-year overall survival was 79% for HCT and 81% for SOT.

With such a larger number of patients and longer duration follow up, these data are consistent with previous studies showing a well-tolerated safety profile, high response rates and durable overall survival of two-years. This will reinforce our clinical development and regulatory strategy for patients with relapsed/refractory EBV positive PTLD. These new data also confirm that tab-cel is potentially the transformative off-the-shelf, allogeneic T-cell immunotherapy with compelling value for patient, physician, and payors in this often deadly ultra-rare cancer.

Turning to our pivotal clinical development program for tab-cel, we remain on track to initiate a tab-cel BLA submission for patients with EBV positive PTLD in the second half of 2020. We know our 35 sites available for enrollment in the U.S. and Australia, and plan to continue to open additional sites of transplant centers in the U.S. and Canada over the coming months.

We also plan to file a clinical trial application or CTA in several European countries by the end of this year and to open study sites there next year. Meanwhile, we are engaged in discussions with the EMA and the outcome of these discussions will determine the timing of the tab-cel EU conditional marketing authorization application for patients with EBV positive PTLD.

Our BLA submission guidance takes into account the recruitment constraints inherent in our pivotal study, due to the nature of PTLD as an ultra-rare and rapidly progressing disease. Our Phase 3 study are also only open at about 10% of transplant sites in the U.S. And there are a number of competing although less advanced clinical trials. Since July, we have upgraded the way we are addressing these constraints.

And importantly, we believe these development constraints should have limited impact on the tab-cel business case for PTLD. Indeed, the value to individual patients will be high with such a potentially transformative T-cell immunotherapy. Also tab-cel could be delivered within three days of order to any center to an appropriate patients' needs.

And if tab-cel becomes the first approved treatment for PTLD, it would likely be supported by patients and physicians based on proven efficacy and safety. The potential U.S. market size for this first tab-cel indication is several hundred patients per year. Taken together with the potential tab-cel opportunity in Europe, we believe there is a strong and profitable business case for Atara to commercialize tab-cel in the relapsed/refractory EBV positive PTLD in these geographies.

We're also advancing studies in potential additional indication for tab-cel. We continue to enroll patients in our Phase 1/2 clinical study of tab-cel in combination with anti-PD-1 therapy in patients with platinum-resistant or recurrent EBV-associated NPC. We also expect to start enrollment in a Phase 2 multi-cohort study targeting other EBV positive cancers in the second half of 2020 to continue expanding the value proposition of tab-cel. Overall, these value studies show the potential opportunity for tab-cel as an ultra-rare disease pipeline in a product.

Now turning to our second priority, ATA188. We reported encouraging data at ECTRIMS in September in patients living with progressive MS. Recently, we reviewed the six-month follow-up data of our cohort 3 dose. Based on this data, we are pleased to share that we have selected this cohort 3 dose to initiate the Phase 1b portion of the study. The decision to initiate the Phase 1b was based on achieving in cohort 3 our pre-determined criteria of a continued well-tolerated safety profile and at least 50% of patients experiencing clinical improvement based on the multi-scale assessment defined at ECTRIMS, with improving patients coming from more than one clinical study site. Recognizing these are early data and incorporating input from external experts, we believe these results merit the acceleration of ATA188 development for progressive MS patients who have limited treatment options and in whom continuous decline is expected.

In addition, enrollment in the fourth and final planned Phase 1 dose escalation cohort is complete. Six months data from cohort 4 will be mature in April 2020. We plan to present then all cohort data in detail at an appropriate congress in 2020.

Following such encouraging ATA188 results, and in line with our strategic focus on allogeneic T-cell therapy, we have decided not to move forward with the Phase 2 study for ATA190 or autologous product in MS. This decision will allow us to focus our resources on ATA188 to ensure efficient study execution, as well as reduce autologous operating complexity and associated manufacturing cost. We continue to evaluate strategic options for ATA190.

Our third strategic priority is around the mesothelin CAR T programs, ATA2271 and ATA3271. ATA2271 is an autologous CAR T for mesothelin-associated solid tumors for which an IND is planned in 2020. ATA2271 will enter the clinic first, while we work to advance development of ATA3271, our allogeneic mesothelin-targeted CAR T, leveraging our EBV T-cell platform. Both of these programs have great potential, due to the incorporation of novel 1XX co-stimulatory domain and a PD-1 dominant negative receptor.

Finally, Atara's fourth strategic priority is ATA3219. Our internal allogeneic CD19 CAR T. This asset is currently in pre-clinical study, and will later be bought to IND with the goal to demonstrate clinical proof-of-concept for our EBV CAR T platform. Here we intend to show that allogeneic EBV CAR Ts are safe, expand in vivo, traffic to tumor sites, perceive sufficiently to obtain high response rate and durability of responses.

Turning to a few operational updates. Facility commissioning and qualification activities to support clinical development at our Operations and Manufacturing facility, ATOM, are complete. Commercial production qualification activities are progressing well and aligned with our commercial strategy.

Additionally, we will be expected by a new CEO of Operation [Phonetic] maximizing Atara's operational efficiency. I am now in a process of adapting my leadership team to our new strategic priorities. This effort includes active searches for a new Global Head of Research and Development, a Head of Commercial and a General Counsel.

Before opening the call to questions, I would like to comment on our third quarter 2019 financial results. We ended the quarter with cash balance of $282.9 million, reflecting proceeds from our recent secondary follow-on financing. We continue to expect to have cash to fund ongoing operations into 2021.

I would like now to turn the call back over to the operator, so we can go ahead and take your questions. Operator?

Questions and Answers:

Operator

Thank you. [Operator Instructions] And our first question comes from Anupam Rama from JP Morgan. Your line is now open.

Anupam Rama -- JP Morgan -- Analyst

Hey, Paz, thanks for taking my question, and congrats on all the progress. You know in the past, we've talked about in PPMS, they need to follow patients long-term to truly kind of understand the emerging clinical profile of ATA188. What are you seeing at the six-month time point in cohort 3 dose that's really giving you the confidence to move forward here, given the 12-month, 18-month time points are not available? Thanks so much.

Pascal Touchon -- President & Chief Executive Officer

Thank you, Anupam, for your question. I will start, and maybe AJ will chime in there. So, clearly, we have predetermined criteria for moving forward to the Phase 1b. These Phase 1a study as you know is built as a one-year study, with different time points for assessment of the clinical evaluation of the patients there. So we have reached that particular situation with cohort 3 dose having data of six months that shows that not only we have this well accepted safety profile, but we have also these clinical improvement in at least 50% of the patients coming from more than one site.

And when we have these results in the hands, we believe these results merit acceleration of our decision to move to the 1b, while we of course pursuing the 1a, and we will have more mature data on these different cohorts, particularly cohort 4, for which we don't have yet the six months data.

AJ, do you want to comment on that?

AJ Joshi -- Chief Medical Officer

Sure. And, you know, Anupam, just recalling the criteria that we use, we specifically set those criteria up to try to find early signals, because your point, it does take a longer time frame to really have some of those -- some of the EDSS and other style endpoints. So again this approach specifically looked for early signals. Now based on the approach, when we talk about 50% having clinical improvement, the bar was relatively high, because there were seven different scales we use and we required an improvement on two separate scales at consecutive time points.

So that means, we measured at three months and six months. Those are our time points. You'd have to have improvement on two scales at each of those time points for the patients. And, you know, when we discussed that with [Indecipherable] we thought that was a relatively high bar for us to hit. And then we also said, you know what, it's an open-label study. We want to make sure that these improvements are happening at more than one site. So these -- the 50% target that we hit was 50% improvers, plus it was at two different sites. So the intent was to set a high bar, using this kind of early signal detection and that's what gives us the confidence, because it was a high bar and we did have that early detection.

Pascal Touchon -- President & Chief Executive Officer

Yes. And as we say, there will be additional details to be shown as appropriate at scientific congress in 2020.

Anupam Rama -- JP Morgan -- Analyst

Great. Thank you so much, and congrats on all the progress.

Pascal Touchon -- President & Chief Executive Officer

Thank you, Anupam.

AJ Joshi -- Chief Medical Officer

Thank you.

Operator

Thank you. [Operator Instructions] And our next question comes from John Newman from Canaccord. Your line is now open.

Christopher Liu -- Canaccord -- Analyst

Hi. Thanks for taking my question. This is Chris on the phone for John. So I just wanted to ask if we could get any additional color on enrollment? And you've also mentioned opening more clinical sites in Canada and the U.S. Just wondering what that timeline would look like, and how many sites you guys were thinking about?

Pascal Touchon -- President & Chief Executive Officer

Thank you for your question, Chris. In terms of enrollment, the enrollment is progressing as planned to be aligned with our guidance for initiating the BLA submission in the second half of 2020. As we mentioned earlier on, part of the challenge in recruiting more patients in this study is the need to expand on other sites, because today we are only in about 10% of transplant sites in the U.S.

So this is done in two way. In the U.S., we are continuously increasing the number of sites. This takes the necessary time for these sites to be open and running. And then we have obtained in July the approval from the Canadian authorities to start opening sites in Canada, and that's why we are now moving into Canada. We had already opened five in the past in Australia. And then the next stage will really be Europe, where we are going to file a CTA in several European countries by the end of the year, to be able to open site next year once the usual process of review of the CTA has gone through [Phonetic] in these specific countries.

Christopher Liu -- Canaccord -- Analyst

Got it. Thank you very much.

Pascal Touchon -- President & Chief Executive Officer

You are welcome.

Operator

Thank you. And our next question comes from Salim Syed from Mizuho Securities. Your line is now open.

Salim Syed -- Mizuho Securities -- Analyst

Hey, guys. Thanks so much for taking my question, and congrats on the progress. Just a couple from me. So when you were thinking about cohort 3 and making the decision to either move cohort 3 forward or waiting for cohort 4, was there a reason why you decided not to wait for cohort 4 here, specifically, theoretically or with actual data?

And then also just on ATA190, when you say, you're not developing at this time and you're validating strategic options, could you just give us a little more color? Does that mean you're planning to sell the product or are you holding on to it? Do you no longer think that it's part -- can address a different part of the commercial market? Thanks so much.

Pascal Touchon -- President & Chief Executive Officer

Thanks, Salim, for your good questions. Maybe AJ, you can start with the first one, and I'll take the second one.

AJ Joshi -- Chief Medical Officer

Sure. So it's a good question, Salim. I think the -- when we had our pre-determined criteria for go/no-go, as I mentioned earlier, it's a relatively higher bar. To some extent, actually some of our thought leaders didn't think we would hit that, they thought we will be kind of in the middle zone. And we hit it pretty nicely with cohort 3. And the decision was that, you know what, the cohort 3 dose looks good, and because there's such a high unmet need here for these patients, because remember, this is a baseline declined population and we should expect a decline everywhere, right. And the measures that we use should pick those things up.

And even despite that concept, we have those three patients have clinical improvement. So it made sense to move forward with the cohort 3 dose. But we've also left ourselves some optionality, because as we get the data -- and the six month data will mature for the cohort 4 dose in the April time frame. As we get those data in, if we're seeing a signal that suggests we need to actually take a look at cohort 4, we've already set up a plan to adapt our protocol to allow for that dose to be evaluated as well. So for us, we feel like we have a good dose now. We may have a better dose and we leave ourselves with options to go for both. But no sense in holding back, given the high -- given the high unmet medical need here.

Pascal Touchon -- President & Chief Executive Officer

And your second question, Salim. I mean, clearly, with these two assets, ATA190 and ATA188, they were about at the same stage of development. I would even say that ATA188 was a bit more advanced being in these program of 1a followed by 1b. We were ready to start a Phase 2 for ATA190, as we had explained in the past.

But having these encouraging results, we say let's focus on the allogeneic T-cell therapy there, because clearly for this type of disease, chronic disease, where we're going to bring for the first time ever, we believe, a T-cell therapy, allogenic offers significant opportunities compared with autologous there. And we don't see what autologous could bring right now in terms of advantages, but we also want to focus our resources on delivering rapidly some clear proof-of-concept from the Phase 1b in a double-blind, randomized, placebo-controlled ways.

So we will keep the ATA190 in our portfolio and review strategic options there, other ideas that we are considering right now, but we want really to focus and to execute resolutely on these development, because the Phase 1b is truly the key element of value creation for the company and for patients, once we have these results, and more we can accelerate based on proper achievements of predetermined criteria and with the support of external expert, the better for the patient and for the company.

Salim Syed -- Mizuho Securities -- Analyst

Great. Thanks so much, guys.

Pascal Touchon -- President & Chief Executive Officer

Is that fine? [Phonetic]

Salim Syed -- Mizuho Securities -- Analyst

Yes. That's perfect. Thanks so much, Pascal. Thanks so much, guys.

Operator

Thank you. And our next question comes from Phil Nadeau from Cowen & Company. Your line is now open.

Phil Nadeau -- Cowen & Company -- Analyst

Good morning. Thanks for taking my questions. A few on tab-cel. I guess first a follow-up to an earlier question. You mentioned that you're in 10% of U.S. centers now. I guess the question is, why is it just 10% of U.S. centers trial has been open for, I think, close to two years. So what has been the hold up in getting more sites on board in the U.S.?

Pascal Touchon -- President & Chief Executive Officer

I think, AJ, do you want to answer that?

AJ Joshi -- Chief Medical Officer

Yes. I think it's -- when you -- I wouldn't necessarily call it a hold up. We are at -- we are kind of focused in on the centers that we feel like are going to be the best geographically suited and the ones that are going to be seeing the most patients. Then, we have a kind of a secondary structure that for the centers where we're not in, we've actually hired a fairly decently sized Medical Science Liaison team to reach out to those additional centers, where if there are patients being found at those centers, we're able to refer them into those top -- those -- the 35 or so that we have now.

So it's -- there is really never an intend to -- there is over 300 transplant centers in the country, there is not an intend to be at 300 transplant centers. It's really to try to zone in and optimize the centers that we're at now. It doesn't mean, we're not going to continue. We are continuing to add centers, but we've really never try to get to, you know, whatever, 200 centers there. The goal would be to be at the top centers to refer patients in, when they are found from the other centers. And then of course the geographic expansion through Canada and Europe will be the next key part of it.

Pascal Touchon -- President & Chief Executive Officer

And I would feel that, since July, we have also had additional MSL to continue to increase awareness and interaction with HCT transplant centers. And we're also starting to use artificial intelligence technology to evaluate claims data to identify potential patients suitable for enrollment. So we have upgraded our efforts there. So it's not only the number of centers, it's all the efforts we've done and accelerated since July to be able to recruit in line with our guidance.

Phil Nadeau -- Cowen & Company -- Analyst

Okay. That makes sense. And then second is on the U.S. filing guidance, you mentioned the filing will be initiated in the second half of 2020. What modules will be filed first and do you have a sense or some guidance for when the filing will be completed?

Pascal Touchon -- President & Chief Executive Officer

So as we said last time, these filings will be based -- these initialization of filing will be based on an interim analysis, that has been pre-specified in our protocol. So that's why we're mentioning this word of initiation of a BLA filing there. And at this stage there is some very specific request from the FDA in terms of follow-up of the patients. And I think we shared that with you last time that the FDA is asking for a six months follow-up -- following response. So response usually is being identified at two months after the first infusion. So two months, plus six months or eight months of follow-up from the last patient being enrolled there. So that's an important aspect to take into account.

Our guidance has been clear that we will be able to initiate this BLA filing in the second half of 2020 based on one hand, on the interim analysis, for part of the total population, on the other hand of course on all the CMC and other aspect that is needed for the filing. And this is on track, on schedule, there is absolutely no issue there. It's really the limiting factor for the timing, it's really the recruitment and enrollment of patient and achieving a predetermined, pre-specified number of patients for the interim analysis there.

Phil Nadeau -- Cowen & Company -- Analyst

So when will PDUFA date be decided -- given to you by the FDA. Will it be upon the initiation of the filing or do you have to get that six-month follow-up data in first?

Pascal Touchon -- President & Chief Executive Officer

This is truly a review process, because as expected we will go to a pre-BLA meeting with the FDA and discuss with them how they see our data so far and what is the best possible way to move forward for these patients. I would like to say that the FDA has been very constructive in our discussions so far. So we're very optimistic there that we will find the best possible way to bring these transformative therapy to U.S. patients, if indeed the results are at the level we believe they could be.

Phil Nadeau -- Cowen & Company -- Analyst

Great. And one last question from me, just on the EU. Can you give us an update on the issues that you continue to discuss with the regulators? And any guidance for when you get clarity from the EMA and what will be necessary for a European filing?

Pascal Touchon -- President & Chief Executive Officer

We're not going to give a guidance on timing. I would say, we are really discussing with them. We are, as you know, in the PRIME system in the EU, which is a system that for transformative therapies levels also some interactive dialog with PRIME repertoire [Phonetic] that is designated by the EMA. And this dialog is constructive dialog and the importance there is to agree specifically on the SOT, because that's where we challenge following alignment with the FDA that produce protocol in terms of joining the [Indecipherable] and we want to make sure that these type of change is fully supported by the EMA for the PRIME system of interaction with the EMA. So we will inform you when we make progress there, and when we have a clear view on when we believe we can file in Europe for conditional approval.

Phil Nadeau -- Cowen & Company -- Analyst

Perfect. Thanks for taking my questions.

Operator

Thank you. And our next question comes from Tony Butler from ROTH Capital. Your line is now open.

Tony Butler -- ROTH Capital -- Analyst

Thank you very much. AJ, you made reference to -- in 188 to an earlier question that early signals gave you confidence to move forward in the Phase 1b portion of the study. What I'm about to ask you is more theoretical and clearly not known. But the question is, do you have -- do those early signals tell you something about the duration that a patient may see on therapy? And second, with that stated, do you think that EDSS actually that -- as the patient progresses on study, that their EDSS scores actually improve beyond that initial signal. So the question is more about what happens in the future, if you have a view?

And then my second question, if I may. Pascal, could you maybe provide us with some of the criteria you think about, when you're looking at ahead of R&D? And how you might think about those criteria, when you want to hire that person? I appreciate the time.

Pascal Touchon -- President & Chief Executive Officer

Sure. So if you might imagine getting into the future is always going to be a little bit difficult. And certainly when you -- maybe just to give you an overall perspective, because when you think about clinical improvement, this is what we're really talking about now. There is very few -- people have not really thought about clinical improvement MS. There is very few companies, very few products and programs that ever looked at that. So the one that have looked at it have anticipated, that yes, over time, you would see some kinds of improvements in a variety of disability measures. So when they looked, they haven't look just at EDSS, they looked at a variety of disability measures. Sometimes separately, sometimes as composites.

So as you -- if you think about, OK, we would look at our product in a similar fashion. If you're looking for improvement, you would look for something like that. So maybe that's the best way I can answer it. Obviously, we're going to have 12-month data that's going to continue to mature over time. So we'll be presenting that style of 12-month data in 2020. So we'll have a cleaner view on it. So we won't be just guessing into the future. But that's the best I can do in terms of expectations. I hope that answers the question.

Tony Butler -- ROTH Capital -- Analyst

I appreciate it.

AJ Joshi -- Chief Medical Officer

One other point actually, sorry, I would like to say. Sorry, Pascal, is that we are -- for the Phase 1a portion of the study, we are continuing an open-label extension. So we will be having annual dosing and that we will also get some additional long-term information on this entire group of Phase 1a 24 patients.

Pascal Touchon -- President & Chief Executive Officer

That's exactly the point I wanted to add. On the 1a, we will continue and we will continue to inform us and physician and experts about the durability of response there.

Tony Butler -- ROTH Capital -- Analyst

Thank you, sir.

Pascal Touchon -- President & Chief Executive Officer

So now, Tony, to your second question there, I think clearly, we have -- I have in mind and we have in mind the ideal profile. And that's what we are looking for, is to try to be as close as possible from that ideal profile. By that, I mean, a clear scientist physician ideally an MD, PhD was -- is knowledgeable about cell therapy was been a clinician in oncology, ideally a transplanter as well. We also have developed product, particularly in oncology to the finished cost in terms of getting FDA approval and EMA approval. And someone who has worked in both large company and biotech companies, and has been a true leader in bringing project forward and excellent execution and operational execution there in bringing product toward to the finish line.

So that's really what we have in mind. It's -- I've been starting to meet with potential candidates, and there is a lot of excitement for these type of individuals in a sense that the scientific basis of our platform, the technology that we have at our disposal now for the various collaboration. The way we've develop these technologies, but also the quality of the team is amazing at Atara. And that's something that we would like to insist upon, that we are benefiting and I'm benefiting myself from what I would call a very strong bench of experienced leaders with CMO, Head of Clinical Development, AJ Joshi, with us today. We have our Head of Regulatory Affairs, Renu Vaish; and our Head of Preclinical and Translational Research, Blake Aftab. So very strong batch, very capable leaders, very knowledgeable and experienced people there, that are supporting value development.

We also benefit from direct support to our pipeline and technologies, not only from Chris Haqq, our former CSO, who is continuing in an advisory role with the company, but with key academic experts in the field, Michel Sadelain and Prasad Adusumilli, Richard O'Reilly from MSK on our different programs there; Marco Davila from Moffitt, Rajiv Khanna from QIMR. So we are really strongly supported by these experts, while taking active part in our discussion related to our science and technology. And we add to that also some key advisors especially in MS, where we are working with key experts of the field, not only from Australia, but from U.S. and more and more from Europe as well. I hope I answered your question.

Tony Butler -- ROTH Capital -- Analyst

Yes, sir. You did. Thank you, Pascal.

Operator

Thank you. And our next question comes from Salveen Richter from Goldman Sachs. Your line is now open.

Salveen Richter -- Goldman Sachs -- Analyst

Good morning. Thanks for taking my questions. Two from me. I guess, Pascal, one is a strategic question here. As you look to creating your CAR T -- your allogeneic CAR T pipeline, just a question as to why you would go into the CD19 space, just given the crowded nature there versus maybe going after some other targets apart from mesothelin?

And then a second question, just following up on what Phil said, you know what gives you the confidence just given that you have only 10% of transplant sites in the U.S. open for EBV program that you can hit this second half '20 BLA submission?

Pascal Touchon -- President & Chief Executive Officer

Thank you for your questions. So I'll start with the first one. There is one slide in our new investors deck that I recommend you maybe to have a look to Slide 40; 4-0. And that's trying to explain how we see the different assets with the different CAR T that we have right now. We have clearly a need to accelerate the clinical stage development of ATA2271 or mesothelin autologous CAR T. And as you know, we are also actively developing at the preclinical stage or allogeneic version of the mesothelin CAR T ATA3271.

Now the reason we are pursuing the development of the CD19 allogeneic EBV based CAR T ATA3219 is really because, we can grow there faster to get to the clinical stage, where we can compare what we will get there with currently approved product in that space, which are autologous, and also some clinical result that starts to appear with some other allogeneic type of platform there. We strongly believe that all EBV based allogeneic T-cell as CAR T could lead to not only a very safe and well tolerated way to treat these patients, but the level of expansion, trafficking and persistence that is needed to have a significant level of response and durable response there.

Persistence is one of the key aspect I believe there, and I think that has been one of the change of many of the allogeneic type of platform. We have data, as you know for more tab-cel experience that shows that the cells are persisting in different type of patients and are persisting long enough to have durable remission there.

We would like to show the same with the CD19 construct and that we believe will be the definite proof-of-concept, and not only we have a feasible platform for allogeneic CAR T, but we have a better platform for allogeneic CAR T that any other platform that exist right now. So, again, that's why we (technical difficulty) think in that program, it's really to have proof-of-concept that will support all of -- all the efforts in terms of allogeneic CAR T, and ability to do so in a rapid way, and to do so in a particular type of disease, B-cell malignancies, where the existing data from autologous and some other early data from other allogeneic platform will help us to be able to compare the type of research we get, and hopefully as we believe, to show how we could be superior to our approaches there. I hope, I answered your question on that one.

Salveen Richter -- Goldman Sachs -- Analyst

Yes.

Pascal Touchon -- President & Chief Executive Officer

And on the number of sites, as we say, we are in about 10% of the site. But as you can imagine from what we say, the increased number of sites in the U.S., in Canada, then later on Europe, all of these will play a significant role in terms of enrolling and recruiting new patients in that pivotal study. We are of course benefiting here from the work that has been done. So the guidance we are giving for the second half of 2020 is based on the reasonable enrollment rates in line with what we're seeing right now.

So that's something is important. It's a reasonable estimate in terms of what we're seeing right now. Any increase in number of sites is going to help us to continue the work to be able to be in line with our guidance, which is our objective. We want to be able to execute, as expected, and we need to deliver as expected, what we would like to do for patients and for our shareholders.

Salveen Richter -- Goldman Sachs -- Analyst

Thank you.

Operator

Thank you. And our next question comes from Ben Burnett from Stifel. Your line is now open.

Ben Burnett -- Stifel -- Analyst

Great. Thanks so much. Congrats on the progress. I have a question about the tab-cel expanded access program. I guess specifically the stem cell transplant group that you reported on yesterday, I think the ORR, it was reported yesterday was 55%, which is a bit lower than our previous analysis of 80%. Obviously, there are more patients, but I was wondering if there is any notable differences between the new -- the six new patients that enrolled into the EAP and were included in this analysis versus the original, I think five, just in terms of disease severity or baseline characteristics?

Pascal Touchon -- President & Chief Executive Officer

Thank you, Ben, for your question. AJ, do you want to take that one?

AJ Joshi -- Chief Medical Officer

Yes. I wouldn't say that there is a significant difference. As you see in the abstract, the HCT patients in general, did have kind of an intermediate to high risk. A higher proportion of them were intermediate to high risk relative to the SOT group. So they were generally a bit sicker patients, but honestly, it's a small number of patients. So I wouldn't -- at least from our read, I wouldn't over read that. I think the key point for us has been that, these data are pretty consistent with almost everything we've presented. We've generally had a 50% to -- a little bit over 80% ORR across all of the different study populations we've reported on. So for me it's still a fairly consists deal.

Pascal Touchon -- President & Chief Executive Officer

And I think the -- also the durability of response is something that is very important there. The fact that we have the 79% to 81%, by the way, on the full population there is extremely encouraging there, in terms of overall survival at two years.

Ben Burnett -- Stifel -- Analyst

Great. That's helpful. Okay. And then if I could just ask one more, maybe just a follow-up on Salveen's question. Could you just maybe articulate a little bit more on the strategy with regards to the mesothelin assets? So 2271 is autologous. So I guess is there a planned shift away from this asset at some point to focus on 3271? Thanks so much.

Pascal Touchon -- President & Chief Executive Officer

Thank you for your question. Here we have, as we said, our priority is on both assets. We want to go to the clinic with 2271. We believe it's going to offer superiority potentially to the first generation, due to the integration of this 1XX co-stimulatory domain, which is going to have an impact, we believe from preclinical data for mesothelin on persistence. And a more physiologic way of addressing the target there from the activation of the T-cell of CAR T. And I think also the PD-1 DNR, with its intrinsic ability to address the immunosuppressive environment that the CAR T is encountering in these type of disease there.

So we're very confident on these autologous CAR T, going to the clinic next year, and the idea is to pursue that. So we start with first in human, clarifying the dose and moving into hopefully proof-of-concept. And then, if we could accelerate to a pivotal study, we will do so. So that's really our aim is to accelerate not only moving to the clinic, but ideally moving through a product that could be approved there.

Now the allogeneic version is beyond in terms of timing for good reasons, and we are pursuing that and accelerating that because ultimately, we believe that having an allogeneic CAR T that is able to offer at least the same efficacy and safety and some significant advantages in terms of the delivery to patients within three days from our inventory, as well as of course cost of goods will be significant in terms of what we can achieve in that particular space. But clearly ATA2271 is a priority for us to move as fast as possible to the clinic through proof-of-concept and ideally to some type of pivotal study.

Ben Burnett -- Stifel -- Analyst

Got it. That's helpful. Okay. Thanks, and congrats again on the progress.

Pascal Touchon -- President & Chief Executive Officer

Thank you.

Operator

Thank you. And our next question comes from Maury Raycroft from Jefferies. Your line is now open.

Maury Raycroft -- Jefferies -- Analyst

Hi everyone. Good morning, and thanks for taking my questions. So I just had a question on the early access and single patient use program for tab-cel. I'm just wondering if you could provide an update on how many patients you treated with tab-cel in those programs? And then, are you acquiring specific data from these patients? And do you plan on providing an update on those patients at some point? Or could you provide a general update on the patients now?

Pascal Touchon -- President & Chief Executive Officer

Sure. So in terms of kind of the total number of patients across all groups, we're probably not going to be giving exact numbers there. What I will tell you though is, a couple of different things about this -- for example, this 201 expanded access program. So you talked about, are we going to be providing data on some of the other patients. Yes. So at a future congress, we do plan on talking about some of the other populations that we're seeing. I think the important thing to understand off of the 201 data that's not PTLD patients that we've got, is that those are data that we've utilized to plan for our multi-cohort study, the 205 study that we've talked about, because it's the information that we've gained in that 201 study, that's actually given us the necessary requirements to figure out how we want to do the 205. So the data that we've gotten is useful and we will be presenting that at some future point.

Maury Raycroft -- Jefferies -- Analyst

Great. Thanks for taking my question.

Operator

Thank you. And that concludes our question-and-answer session for today. I'd like to turn the conference back to Pascal Touchon for closing remarks.

Pascal Touchon -- President & Chief Executive Officer

Thank you everyone on the call today. It has been a great pleasure talking with you. We look forward to finishing the year very strong and hope to see many of you in Orlando at ASH. Have a very nice day. Bye.

Operator

[Operator Closing Remarks]

Duration: 47 minutes

Call participants:

John Craighead -- Vice President, Investor Relations & Corporate Communications

Pascal Touchon -- President & Chief Executive Officer

AJ Joshi -- Chief Medical Officer

Anupam Rama -- JP Morgan -- Analyst

Christopher Liu -- Canaccord -- Analyst

Salim Syed -- Mizuho Securities -- Analyst

Phil Nadeau -- Cowen & Company -- Analyst

Tony Butler -- ROTH Capital -- Analyst

Salveen Richter -- Goldman Sachs -- Analyst

Ben Burnett -- Stifel -- Analyst

Maury Raycroft -- Jefferies -- Analyst

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