Editas Medicine Inc (EDIT) 2021 Q3 法說會逐字稿

Good morning, and welcome to the Editas Medicine Third Quarter 2021 Conference Call. (Operator Instructions) Please be advised this call is being recorded at the company's request.

I would now like to turn the call over to Ron Moldaver, Investor Relations at Editas Medicine.

Thank you, Melissa. Good morning, everyone, and welcome to our third quarter 2021 conference call. Earlier this morning, we issued a press release providing our financial results and recent corporate updates. A replay of today's call will be available on the Investors section of our website approximately 2 hours after its completion. After our prepared remarks, we will open the call for Q&A.

As a reminder, various remarks that we make during this call about the company's future expectations, plans and prospects constitute forward-looking statements for purposes of the safe harbor provisions under the Private Securities Litigation Reform Act of 1995. Actual results may differ materially from those indicated by these forward-looking statements as a result of various important factors, including those discussed in the Risk Factors section of our most recent annual report on Form 10-K, which is on file with the SEC and is updated by our subsequent filings. In addition, any forward-looking statements represent our views only as of today and should not be relied upon as representing our views as of any subsequent date. Except as required by law, we specifically disclaim any obligation to update or revise any forward-looking statement even if our views change.

Now I will turn the call over to our Chief Executive Officer, Jim Mullen.

Thanks, Ron, and good morning, everyone. I'm joined today by several members of the Editas executive team, including Mark Shearman, our Chief Scientific Officer; Lisa Michaels, our Chief Medical Officer; and Michelle Robertson, our Chief Financial Officer.

I want to start off by providing some highlights from the third quarter, including some important milestones for Editas. In our first-ever clinical data readout, we announced positive initial data from our ongoing Phase I/II BRILLIANCE trial of EDIT-101 for the treatment of LCA10, including clinical evidence of gene editing and potential early clinical benefit. We are dosing patients in the adult high-dose cohort and enrolling patients in the first of 2 pediatric cohorts of that trial.

The RUBY study of EDIT-301 for sickle cell disease is enrolling patients, and we expect to begin dosing in the first half of 2022. The pre-IND work for EDIT-301 in transfusion-dependent beta-thalassemia is progressing, and we remain on track to file the NDA -- the IND before year-end. And in our cell therapy platform, Bristol-Myers Squibb opted into a fourth alpha-beta T cell program this quarter, further advancing our successful collaboration. We presented data on our SLEEK technology platform, demonstrating high efficiency, multi-transgene knock-in in multiple cell types, which we believe can enable improved CAR-T and CAR NK cell therapies for solid tumors. At the upcoming SITC and ASH conferences, we will present data showing improved tumor killing ability through multiplex gene editing using SLEEK in our iNK program.

And finally, we've appointed Emma Reeve and Bernadette Connaughton to our Board of Directors. Both Emma and Bernadette are highly accomplished biopharma executives, and we look forward to their contributions to Editas.

This quarter showcased the critical advancement for our clinical programs. The initial safety and efficacy data for the BRILLIANCE trial was an important milestone for patients with LCA10 and marked a key step in Editas' mission of providing life-changing gene editing medicines to patients. These early data provide proof of concept for our in vivo gene editing platform and help strengthen our foundational technology with the clinical evidence to progress our broader pipeline. We made excellent progress this year with our programs and platform technologies, and we continue an aggressive pace to deliver against our long-term objectives.

With that, let me turn the call over to Lisa to review our clinical programs.

Thank you, Jim. I'll start with a recap of our recent data for the BRILLIANCE trial for EDIT-101 for the treatment of LCA10. To give some quick background, CEP290-associated retinal degeneration or LCA10 is a rare inherited disorder affecting about 3 out of every 100,000 children; is autosomal recessive, which means that to be impactful, the person has to inherit 2 copies of the defective gene, one from each parent. Now if you can repair at least one of these copies, you can potentially treat the disease.

Despite being rare, it is the most common cause of early onset inherited retinal degeneration. The loss of vision is caused by early loss of photoreceptors in the eye. Patients are usually diagnosed during infancy and early childhood, with the majority of vision loss occurring in the first decade. However, even in adults, there remains a small area of preserved anatomy in the central part of the retina, and this provides the opportunity for gene correction. When Editas first started the EDIT-101 program, this was the very first time that any company had attempted gene editing in the human body. And as a result, the BRILLIANCE trial was designed primarily as a safety study with the purpose of identifying the highest tolerated dose for subsequent study.

At September's retinal degeneration symposium, we shared safety data on 2 patients treated at the first and the lowest dose cohort and the 4 patients treated in middle-dose cohort as of the data cutoff date in August 4. All observed adverse events were mild to moderate. A majority of these reported events were directly attributable to the surgical procedure. Importantly, no detectable immune responses against the Cas enzyme were observed. This is great news, and results are comparable for the 2 dose cohorts.

Our nonclinical data suggests that we would expect a greater number of photoreceptors to be effectively edited at each consecutive dose level. The safety observed has allowed us confidence to start treating the subjects in the highest planned dose cohort and has allowed us to start enrolling the pediatric dose cohort into the mid-dose pediatric cohort. We expect that EDIT-101 will have a differentiated safety profile as it is administered as a single onetime injection directly to the part of the retina where the photoreceptors are preserved. Targeted approach treats not only those cells -- treats only those cells, sorry, thereby limiting any potential effects on the structures of the eye.

Although the primary endpoint of the study is safety, there are multiple exploratory endpoints that are focused on efficacy. Preliminary findings were presented for the 5 patients who had at least 3 months follow-up after treatment. This included the 2 patients in the low-dose cohort and 3 in the mid-dose cohorts. The 3-month mark was selected as the earliest time point where we might expect to be able to pick up some sign of editing for several reasons. Based on the injection procedure, there needs to be time for the retina to heal and for maximal editing to occur. It may also take additional time for the dysfunctional CEP290 protein to be replaced by the newly generated functional protein. 3 months is really when the clock starts, and it may take longer for the brain to respond to the new signals.

One of the challenges of treating an ocular disease is that we don't have a direct way of measuring how much of the normal CEP290 protein is being made in the eye or have a direct way to determine how many cells were edited. So we're dependent on surrogate measures of efficacy such as full-field light sensitivity threshold testing, best corrected visual acuity, an improvement in an individual's ability to navigate standardized navigation courses with varying levels of difficulty. At least one positive change in any of these measures will suggest that a biologic effect has occurred on how the treated photoreceptors in the eye registered light.

For this reason, we were very pleased to document meaningful changes from baseline in one or more measures in the 2 mid-dose subjects in whom we have the longest follow-up. The changes prove biological activity. Most excitingly, in at least one subject in the mid-dose cohort, there is a clinically meaningful change in best corrected visual acuity and a real change in her ability to maneuver through obstacles at different levels of light. These are approvable clinical endpoints. As for the other patients treated in the mid-dose cohort, it may have been too easy to draw a conclusion -- it may have been too early, I'm sorry, to draw conclusions, which is why we continue to follow them. In the meantime, we are eager to see whether the study can produce similar or stronger responses in the subjects who are now being treated in the high-dose group.

We've been very pleased with the safety we have observed so far and in the initial signals that effective editing has occurred. This is illustrated by clinically meaningful changes into the dose cohort and in those subjects with the longest follow-up. Consequently, BRILLIANCE study is moving forward. We continue to progress the high dose and -- the adult high-dose and the pediatric mid-dose cohorts and expect to complete dosing of these 2 cohorts in the first half of next year.

Now turning to our ex vivo programs, specifically EDIT-301 for sickle cell disease and transfusion-dependent beta-thalassemia. We believe that EDIT-301 has the potential to be a leading gene-editing medicine based on its highly efficient editing and specificity, which we expect to result in optimized safety and efficacy by demonstrating robust and sustained fetal hemoglobin or hemoglobin F expression with both short- and long-term safety. We aim to have a differentiated medicine to treat sickle cell disease and beta-thalassemia that will hopefully lead to longer lifespans and better quality of life for these patients.

We're currently enrolling patients in the RUBY study for the treatment of sickle cell disease. In this program, we are using our engineered Cas12a enzyme to target a region in the beta-globin locus. We believe this to be a potentially safer target for gene editing because several different mutations or polymorphisms that are not associated with human disease occur at the site. More specifically, the Editas approach mimics naturally occurring mutations associated with a condition called hereditary persistence of fetal hemoglobin, which we know prevent sickling.

We've demonstrated excellent preclinical data that supports the benefits of editing the beta-globin locus and our Cas12a enzyme, and we're also very excited to be advancing the program to the clinic. As mentioned, patient screening and enrollment is moving forward for EDIT-301 in sickle cell disease. We have patients who are currently undergoing cell harvesting cycles as a requisite to editing their own stem cells, and we look forward to dosing the first patient in the first half of next year.

On EDIT-301 for transfusion-dependent beta-thalassemia, we're going to be presenting data at the American Society of Hematology conference next month. Preclinical data will demonstrate that edited CD34 cells showed significant improvement in erythroid maturation and health, along with increased total hemoglobin content. This reinforces our belief that our therapeutic strategy has great potential for beta-thalassemia in addition to sickle cell disease. We remain on track to file our investigational new drug application for EDIT-301 in beta-thalassemia by year-end.

And with that, I'd like to turn things over to Mark to run through our pipeline and our gene-editing technologies.

Thank you, Lisa. I'll start out with an important advance in our editing platform that we call SLEEK, which we presented at the Cold Spring Harbor conference in August. We are really excited about this proprietary technology. SLEEK is short for SeLection by Essential-gene Exon Knock-in. It's a technology that was developed at Editas utilizing the ASCas12a nuclease to selectively and with high efficiency integrate transgenes into a specific locus. Essentially, the technique allows us to get high-efficiency knock-in with a number of different cell types while also ensuring robust transgene expression. We've published data on iPSCs, T cells and NK cells and believe the knock-in rates are the highest in the gene editing field across these cell types.

In addition to the high editing efficiency from AsCas12a, we utilize a selection process where only those cells that have been successfully edited survive so rates of transgene expression in the final cell population are extremely high. Furthermore, we can fine-tune the expression levels of transgene cargoes by knocking in at different essential genes, which could be an important attribute of next-generation cell therapy medicines.

We think this is a really powerful technology that is far superior to other modes of integration that we've seen published. And we've deployed this in our INK program as well as in our collaboration on the alpha-beta T cell program with Bristol-Myers Squibb. It's something that we've been working on for some time that can open up a lot of possibilities for more effective and safer cell therapies.

Also related to our platform, we recently presented at the TIDES Oligonucleotide and Peptide Therapeutics Conference about the advantages of our AsCas12a nuclease. Additionally, we described some of our process and analytical chemistry capabilities for guide RNA synthesis. With the completion of our Boulder, Colorado GMP manufacturing facility, we remain confident that our in-house guide RNA development will translate into high fidelity and quality manufacturing for our next-generation enzymes.

Our iPSC program utilizes both the ASCas12a nuclease and the SLEEK technology. One important goal is to customize an iNK cell which addresses some of the current limitations of this class of therapy, specifically around persistence. We're using a combination of knockout and knock-in technologies to introduce a series of edits. For example, we've knocked out TGF-beta receptor 2 to overcome resistance and CISH to improve persistence. At the upcoming SITC and ASH conferences, we'll be presenting additional data indicating some of our knock-in and knockout strategies. We're building on a number of different strengths that we have to produce a customized iNK cell that we believe will be superior across multiple tumor cell killing mechanisms as well as persistence and potentially also targeting, which reinforces our view that it's an exciting allogeneic approach for a potential wide range of solid tumors.

On the knock-in side of the equation, at the upcoming SITC conference, we'll present data demonstrating that using SLEEK knock-in genes of CD16 expression greatly improved serial tumor killing, thereby enhancing antibody-dependent cell-mediated cytotoxicity of iNK cells. This is important data as it provides evidence for the potential of our iNK program as it advances towards the clinic.

At ASH, we'll also demonstrate that the double knockout in iNK cells at both CISH and TGF-beta receptor 2 genes that I mentioned earlier promotes high levels of cytotoxicity and enhanced in vivo tumor killing in preclinical models compared to unedited iNK cells. Furthermore, we'll show that cryopreservation of these cells had no impact on their tumor killing abilities, which is an important property for an eventual off-the-shelf cell-based medicine.

We also believe this to be a much safer approach to developing next-generation cell therapies because through our iPSC clone selection process, we specifically avoid potential cell abnormalities. After gene editing iPSCs, we screen and select single clones that are fully characterized, including detailed sequencing and cytogenetic analysis. By doing this, we eliminate clones with chromosomal abnormality. The selected edited clones only contain the desired allelic edits, ensuring a pure final population of iPSCs.

These clones have highly characterized genomes and allow us to create a master cell bank that is stable and infinitely renewable, from which we differentiate the edited iPSCs into edited iNK cells. The iNK cells will be fully characterized and analyzed with a well-developed analytical assay panel to confirm the genomic profile. This process and the preclinical data thus far may address some critical barriers to allogeneic NK cell therapy for solid tumors, and we're eager to move this program towards the clinic.

And lastly, in our partnered cell therapy program, we're excited that Bristol-Myers Squibb has opted into a fourth alpha-beta T cell program as part of our ongoing collaboration. Over the last year, one of these programs has progressed to development candidate status. This has been a very productive collaboration, and we look forward to future progress.

With that, I'd like to turn it over to Michelle to review our financial results.

Thank you, Mark, and good morning, everyone. I'd like to refer you to our press release issued earlier today for a summary of our financial results for the third quarter. I'll take this opportunity to briefly review a few items. Revenue for the first 9 months of this year was $13.1 million compared to $79 million for the same period last year. During 2020, we recognized $71 million in revenue in connection with our agreement with Allergan, $63 million of which was earned during the third quarter of 2020 as a result of recognizing the remaining deferred revenue balance associated with this agreement when we regained control of our ocular program last summer.

Comparing the first 9 months of this year to last year, total operating expenses increased by approximately $16 million. This is related to an increase in stock-based compensation of $18 million, $9 million in success payments due under certain of our institutional licenses as well as an increase in expenses to support our clinical programs. These increases were offset by a $3.4 million tax credit reported as a gain in operating expense during the period and a decrease of $9.5 million in in-profit R&D that was reported in 2020 in connection with the Allergan transaction as well as 2020 in-license expenses that did not recur in 2021.

Comparing the third quarter of 2021 to the same period last year, total operating expenses decreased by approximately $8 million. This is primarily related to expenses recorded in 2020 in connection with the Allergan transaction that totaled approximately $9 million as well as expenses that we incurred in 2020 in connection with an in-licensing agreement. During the third quarter of 2021, the company had an increase of $4 million in stock-based compensation compared to the same period last year, which is fully offset by decreases in legal patent fees and the tax credit that was reported as a gain in operating expenses during the quarter.

Editas continues to have a strong balance sheet and cash position as of September 30 of $657 million compared to $698 million at the end of Q2. This capital will allow us to continue to progress on our clinical program and further develop our pipeline as well as our internal manufacturing capabilities. We anticipate that this cash -- current cash position will fund our operations well into 2023.

With that, I will hand it back to Jim.

Thank you, Michelle. This has been a strong quarter for Editas. We presented the first clinical data for the company, validating our in vivo gene editing platform. We made substantial progress in our other pipeline programs moving towards the clinic. We've made fundamental advances in our platform technologies, including our best-in-class engineered ASCas12a enzyme and our innovative SLEEK platform to deliver what we believe to be unprecedented gene editing knock-in rates.

We built our manufacturing capabilities to support our multiple clinical programs. We brought together a world-class leadership team that is capable of executing on the tremendous opportunities we have for our technological platform, and we have the financial resources to deliver on these opportunities. I believe there's never been such an opportunity to deliver innovative new genomic medicines to patients. That is at the heart of everything we do and what motivates us to push forward on our programs and technological innovation.

We thank you all for your interest and support. And with that, we'll open it up to questions and answers.

(Operator Instructions) Our first question comes from the line of Cory Kasimov with JPMorgan.

This is Thomas on for Cory. I guess maybe just on 101, can you talk about how we should be thinking about the cadence of potential updates from here, including longer-term follow-up from the adult low- and mid-dose cohorts and then also data from the new cohorts? I'm curious specifically if you can comment on what kind of duration of follow-up you'll be looking for to share these data updates.

So I'm going to keep it fairly short and to the point, I think. One of the important things for us this year in terms of being able to share data was the fact that it had been such a long period of time from when the study has started, and we thought it was important for us to be able to communicate an update on the trial. We were very happy with the safety that we observed as well as the clinical signs suggesting that editing had occurred.

I think in terms of our next planned update, that's going to be primarily data driven. The trial is continuing to enroll both with pediatric and the high-dose adult cohort. And the timing of delivery will be [dependent] upon our ability to give longer-term safety data on the mid-dose cohort as well as some preliminary efficacy data in the high dose cohort, at which point we'd like to have at least 3 months data on all the patients in that cohort before we move forward.

Our next question comes from the line of Joon Lee with Truist Securities.

This is Mehdi for Joon. My question is related to EDIT-301. And specifically, we want to know what kind of specific experiments you did to define the inversion or deletion rate in the locus and if you have compared that to the same rate if you would have done that with Cas9 and so on.

Yes. I'll take that. So we did a lot of experimental work preclinically to define the on-target edit. To your point, this included extensive sequencing. We had known ahead of time that the activity was pretty much limited upon target editing as opposed to any off-target editing. And so we found, across both normal as well as sickle and CDP cell, the profile was very consistent, which appears to be a property of the combination of the guides and AsCas12a. We do not have comparable data sets with Cas9 and Cas12a. We focused on the AsCas12a, which given what we're trying to achieve with this approach, which is to disrupt the binding of BCL11A, this was the most appropriate nuclease to do that.

Our next question comes from the line of Phil Nadeau with Cowen & Company.

I guess one on 101 to start. Which patient population do you think is most appropriate for future development in pivotal studies? Would you move forward in both pediatric and adult patients? Or would pediatric patients be more appropriate given their disease state?

So at this point in time, there's no reason to consider not going forward with both adult and pediatric patients. So far, we are seeing some clinically meaningful endpoints in the adults. And in the pediatric patients, it's expected that we should be able to get at least as good a benefit, if not more. So I don't see a reason to limit the patient population at this point.

Got it. And one follow-up question on chromosomal abnormalities. You mentioned what you do to assay for them in iPSC program itself. What are you doing in, say, the 301 program? Do you feel like you have to change your release assays given what was seen by another gene editing company recently? Or do you feel that your assays would pick it up in all the programs?

I think the short answer is no. We have no intention to really change the assays that we've applied to this program. We've very thoroughly analyzed the changes at the editing site. And as we've expressed, we have no evidence of any chromosomal abnormalities created by this editing event.

Our next question comes from the line of Yanan Zhu with Wells Fargo.

So first, on BRILLIANCE, I'm wondering if you could -- I know you just talked about a time line for data. Is there a possibility to see data by the end of this year? And also, in terms of the endpoint on OCT changes as an evidence for gene editing, do you think -- at what time point do you think it may be possible to see OCT change?

So I guess to the first question is the patients are basically seen every 3 months after they passed the safety at the very beginning of the trial. So that does limit the intervals and the periods of time we're able to give updates. The second one is related to OCT. One of the challenges with these patients, especially very early on, is that they have significant nystagmus, so it's very difficult for their eyes to remain still enough for the OCT imaging. And to be able to measure those changes, you need to be able to have landmarks in the eye that you can compare it to. We are following OCT moving forward in these patients as best as we're technically able to do so.

Got it. Follow-up on the iNK program. Do you think -- in the first iteration of the candidate, would we -- would you implement some kind of IL-15 receptor ligand engineering for persistence?

So I'll take that. So I think based on the track that other people have taken, that would be a logical approach. I think you'll have to wait for the details which we will present at the ASH conference on that.

Our next question comes from the line of Dae Gon Ha with Stifel.

First question is for Mark. As we look into BRILLIANCE, the pediatric going into the mid-dose and eventually maybe higher, I just wanted to get your take on one of the gene therapy companies that recently reported that basically tested the same dose as the adults. Adults were safe but pediatrics started showing some inflammation after about a 1-month mark. So can you talk to the AAV safety as it pertains to pediatrics using the same dose? I know it's immune privilege, but any thoughts on that? And I've got a follow-up.

Yes. Thanks for the question. I think right now, it's too soon to determine if this -- the finding that you're referencing will be recapitulated across other gene therapy programs. I think right now, we're focused on continuing enrollment, particularly in the adult high dose as well as initiating the pediatric dose, and we're doing that in a very careful stepwise manner. And we'll track the tolerability of the vector in this patient population. I think that's all I can say right now.

Great. And then the other question is on EDIT-301 with RUBY. One of your colleagues here in Cambridge just announced this morning they cleared the IND for an ex vivo also targeting HBG1 and 2 promoter region. So maybe can you talk a little bit about what you can do strategically on the protocol side to perhaps accelerate patient enrollment as well as get that patient treatment going in that earlier part of first half potentially versus a latter half?

So I don't know that we can necessarily accelerate because the treatment of the first patient is safety driven and basically being able to show that they have had meaningful engraftment from the treatment. What I can tell you, however, is that we do have multiple patients in the pipeline with the intention that once we achieve that safety mark, we'd like to be able to start enrolling patients much more rapidly.

Our next question comes from the line of Jay Olson with Oppenheimer.

Can you talk about the time line and gating factors for EDIT-102 to enter the clinic? And anything that you've learned from EDIT-101 that can be applied to that program?

So we haven't given any specific guidance on EDIT-102 other than that we are continuing to iterate and improve upon the editing efficiency for that program and that it's our intention to present the results of those improvements at scientific conferences in the coming year.

Okay. And then maybe as a follow-up for EDIT-301 in sickle cell disease. I think you said the target enrollment is 40. How long do you think it will take to enroll 40 patients? And do you know how long you will need to follow those patients before filing?

So basically, this is the -- it's a well-trodden path. So what we're doing is not necessarily any different than what our competitors have been doing in the same exact space. But in general, the primary goal of getting to these patients is first to be able to demonstrate grafting. As I've already mentioned, the plan is basically be able to start moving more patients in tandem and in parallel moving forward. And at the moment, we're not having any issues related to enrollment. It's actually quite strong.

Our next question comes from the line of Luca Issi with RBC Capital Markets.

Congrats on the progress. I have 2: one on BRILLIANCE; and one on strategy, a little bit bigger picture. So maybe on BRILLIANCE, I think the data at RD showed a serum neutralizing antibody against AAV5 in the 10^4, 10^5 level. So wondering if you can expand a bit more on what gives you confidence that such levels are low enough that do not prevent you from either redosing or dosing the fellow eye.

And then maybe bigger picture on strategy. We've obviously seen one of your competitors breaking up the company, spinning off the oncology pipeline in a new company and focusing on rare genetic diseases. Wondering what was your take on that decision and if that is something that you're contemplating.

Yes. Thanks for the question. I'll address the first part on neutralizing antibodies. Certainly, the levels we've seen do not give us any concern about, one, correlation with any other immune response; and two, no issue with potential redosing in the same eye or even dosing of the second eye. That's based on an fairly extensive non-human primate series of studies that have been published. So yes, we're not concerned. That is a pretty typical profile.

Yes. And this is Jim. I'll take the second one. So as you know, we already have a nice collaboration going that's, I would say, gaining momentum with BMS on the T cell side of oncology. And as I have said previously, and I think we've been fairly public about it, on the iNK, we are certainly going to entertain another collaboration or an expansion of a collaboration we do have. So I do think it's an area where a collaboration with an established oncology player is important for success. And so we'll continue to pursue that.

Actually -- this is Mark. I want to correct something I said earlier. The IL-15 data is actually going to be at SITC, not ASH. So you don't have to wait until December.

Our next question comes from the line of Joel Beatty with Baird.

I just wanted to -- alpha-beta T cell program partnered with BMS, could you discuss what they based their decision on to opt into a fourth program? And then can you also discuss the time lines for those programs in general for advancing in development?

Could you just repeat the first part? I didn't catch the question.

Yes. The first part is just what did BMS base their decision on to opt into a fourth program. What kind of data did they look at?

Yes. So they looked at good data. We're not at liberty to disclose the details of the programs with them. Or -- obviously, we don't have complete visibility into their time line or their decision-making around those programs.

Our next question comes from the line of Gena Wang with Barclays.

I have maybe 2 parts of a question regarding translocation. First, just wondering if you can remind us the translocation or chromosomal abnormality rate for the EDIT-101.

And then secondly, you do have a few approaches with multiplexing. I don't know that they will lead to some translocation. So just wondering -- I know you did mention that you do have a very deep sequencing to identify these. So just wondering, what is the process in place to monitor translocation? And what would be the cutoff for the drug product in terms of product release?

So the processes we have in place are actually pretty extensive in addition to multiple different approaches to sequencing at the expected intended edited site to determine that the profile of the edit, which includes indels, deletions, reversions, transections and -- resections, I should say, and so on. The rate of those that we've determined frequently is very, very low, a fraction of a percent. We have not seen anything in any of the in vitro genotoxicity assay or in vivo mouse study that would indicate any potential for malignancy or cell abnormality to date. And then, as I mentioned in the script, for the iNK program with the induced pluripotent stem cell editing, we select a single cell clone which has the exact edits that we want across multiple different constructs on both alleles, and we'll only progress forward a clone that has those and nothing else.

Our next question comes from the line of Rick Bienkowski with SVB Leerink.

Congrats on all the progress. Looking forward to the poster at SITC later this week. I have a follow-up from Dae Gon's question on the pace of dosing for EDIT-301. Could you say exactly how long the observational period for safety and engraftment is after the first patient is dosed in the trial? And are there any other mechanisms built into the trial protocol that could limit the pace of dosing after that first observational period is complete?

So basically, in alignment with regulatory guidance, first patient needs to engraft. That can take place anywhere between 6 weeks to 3 months depending upon the course of the events as well as the second patient basically showing reproducibility of the process. After that, we have the ability to start enrolling more patients in parallel.

Great. And is there anything else built into the trial protocol after that initial period that could limit dosing?

As soon as we've been able to establish reproducibility of the process as well as the patients' abilities to recover and show that they have a meaningful endpoint, we go. Yes.

Our next question comes from the line of Madhu Kumar with Goldman Sachs.

So thinking about the high-dose EDIT-101 data in BRILLIANCE. What do you think you need to see in terms of the kind of visual function endpoints that you -- compared to what you've seen so far in the low and mid-dose that would kind of get you really excited for pursuing the high dose into a registrational trial?

I'm already excited because we actually had really great outcomes in one of our patients, first patient in the mid-dose cohort. She's the one that we actually have the longest follow-up on at the moment, and it's very clear that her improvements did seem to get better with the subsequent follow-up. So I think it's too early to be able to make any real conclusions regarding efficacy of the mid-dose cohort, and that will depend upon the continued follow-up of the patients in that group.

We do expect there to be enhanced -- with each additional concentration applied over the area of fovea, we're fully expecting to have more photoreceptors effectively edited. So as a consequence, we are just -- as long as everything remains safe as it has so far to date and we continue to see the type of changes that we saw in the mid-dose cohort, we're actually excited to expect that we would have a product.

Okay. So then just to make sure I understand it from that. If the high-dose profile shows the efficacy profile seen to date in the mid-dose cohort, that would be kind of sufficient for you to pursue that into registrational development?

Certainly. That's the goal.

This concludes our Q&A session and thus concludes our call today. We thank you for your interest and participation. You may now disconnect your lines.