How to Overcome Primary Resistance in MSs Tumors

Dr. Mohamed Salem, Dr. Myriam Chalabi, and Dr. Andrea Cercek discuss pivotal neoadjuvant immunotherapy clinical trials for patients with MSI-H/dMMR colorectal cancer, focusing on the development of active therapies in the neoadjuvant setting—where patients are treated without surgery, radiation, or chemotherapy—and the importance of patient selection in finding the right target and treatment to improve outcomes.

TRANSCRIPT

Dr. Mohamed Salem: Hello, and welcome to the ASCO Daily News Podcast. I'm your guest host today, Dr. Mohamed Salem. I'm a GI oncologist at the Levine Cancer Institute at Atrium Health. Today, we will be discussing very promising advancements in the neoadjuvant immunotherapy for patients with MSI-H/dMMR colorectal cancer. And I'm very delighted to welcome two world-renowned oncologists whose research has tremendously helped shape the treatment landscape of colorectal cancer. Dr. Myriam Chalabi is a GI medical oncologist at the Netherlands Cancer Institute, and Dr. Andrea Cercek is a medical oncologist at Memorial Sloan Kettering in the United States.

Our full disclosures are available in the transcript of this episode, and disclosures relating to all episodes of the podcast are available on our transcripts at asco.org/DNpod.

Dr. Chalabi and Dr. Cercek, welcome to the ASCO Daily News Podcast.

Dr. Myriam Chalabi: Thank you for having me.

Dr. Andrea Cercek: Thank you very much for having me.

Dr. Mohamed Salem: It's a pleasure to have two world-renowned stars like you. Thank you for taking the time. So, before we start going deep into the topic, obviously, now we are seeing emerging data in CRC using immunotherapy as the neoadjuvant approach, which actually can reduce or even eliminate some of the other treatment modalities and potentially save patients from toxicities. Both of you led what I think are landmark studies in this field. I wanted to give you the chance to tell our audience about your studies and why you think they're important. Dr. Cercek?

Dr. Andrea Cercek: Sure. Thank you so much. So, our study was a neoadjuvant study in early-stage, locally advanced rectal cancer with tumors that were mismatch repair-deficient or MSI-H. And rectal cancer normally is treated with chemotherapy, chemoradiation, and surgery. And the goal of the trial was to utilize PD-1 blockade alone in this subpopulation and evaluate the response. Patients received six months of dostarlimab, which is a PD-1 blocking agent, and then were evaluated for response. If there was no residual disease, they were able to avoid radiation and surgery. And what we've seen thus far in the presentation at GI ASCO in 2022 was that all patients who received six months of dostarlimab had a clinical complete response, so no residual tumor, and were able to avoid chemotherapy, radiation, and surgery and are on observation. And the study is ongoing and actively accruing patients.

Dr. Mohamed Salem: All of us were very excited seeing that presentation at ASCO. And when we came back to the clinic everyone was talking about it, including patients, obviously. Thank you for this, Dr. Cercek.

Dr. Chalabi, you also led a similar study that was actually presented in ESMO in 2022. Can you please give us, like, a brief description of that trial?

Dr. Myriam Chalabi: Yeah, sure. So, this is the NICHE trial, and actually the NICHE trial has been ongoing for quite some time now. We recently presented a larger NICHE-2 study, but basically– so what we started out by doing in NICHE is giving patients what we considered back then a window of opportunity study. We treated patients with MMR-deficient tumors, which I'll be focusing on for now, with two cycles of nivolumab and one single cycle of low-dose ipilimumab. And patients all undergo surgery within six weeks of registration within the study.

And back in 2020, we published the first data of NICHE-1 showing 100% pathologic responses with 60% pathologic complete responses and decided that this should definitely be a treatment that we need to explore in a larger group of patients. And that's where NICHE-2 was born, which we presented at ESMO last year, where we treated over 100 patients with this neoadjuvant approach of two cycles nivolumab, one single cycle ipilimumab, showing 99% pathologic responses, including 95% major pathologic responses and 67% pathologic complete responses. And this was all within five and a half weeks of the first treatment with immunotherapy, so a very short treatment duration with dual checkpoint blockade.

Dr. Mohamed Salem: Amazing results, too. And I know you had a standing ovation when you presented the outcome of the study. And again, congratulations to you, your investigator, and also all the patients participated.

Dr. Myriam Chalabi: Thank you so much.

Dr. Mohamed Salem: I guess the first question that comes to my mind - we have two trials, obviously, now we're moving from one size fits all to precision therapy, like getting actually the right treatment for the right patient. But in the NICHE study, it was a checkpoint inhibitor, and the rectal study was a single agent. I want to start with you, Dr. Chalabi. In your opinion, when should we use single agent or double blockade immunotherapy?

Dr. Myriam Chalabi: That is a great question. I'm going to start off by saying that I don't know the exact answer. I don't think we know that answer. And Dr. Cercek is going to share also her thoughts on this because we're seeing, of course, fantastic responses with monotherapy as well in Dr. Cercek's study. And we've also seen that in a study by Dr. Overman with monotherapy. So that may suffice in some patients, although what we're seeing is that you need to treat patients longer, probably to achieve that response, at least clinically. And I think that is the difference with dual checkpoint blockade, that we're giving in NICHE where we're seeing these very deep responses in just under six weeks' time.

So, I think it may be more of a question of how long we want to treat patients for to achieve the endpoint that we're aiming for. And, of course, there may be, at some point, patients that need dual checkpoint blockade, but so far, we're seeing great responses in both of our studies. So I think we need more patients, more data to see whether we're going to see non-responders. And hopefully, the studies that are ongoing in the metastatic disease setting will give us at least a little bit of insight into what the differences are in response to mono and dual checkpoint blockade and whether we can tell which patients might benefit more from the combination. But I think there's still a lot of work to be done in that field.

Dr. Mohamed Salem: I totally agree. Dr. Cercek, same question to you. What do you think?

Dr. Andrea Cercek: Dr. Chalabi answered beautifully and very comprehensively. I agree completely with what she said. It's hard to argue with the responses that we're seeing with PD-1 blockade alone. But then again, dual checkpoint inhibitors in the NICHE study with just one month of therapy had phenomenal responses as well. So I think it's a question of duration of therapy and, really importantly, what we're trying to achieve. If our goal is organ preservation, then perhaps longer duration is better. The question then becomes, can we do, should we do longer duration with dual checkpoint inhibitors versus single agent? So I think, as she concluded, I couldn't agree more that we just need more information, we need more work to do, basically to answer this question for our patients.

Dr. Mohamed Salem: More to come and more studies, which is fascinating. So, Dr. Chalabi, you created actually a new term on Twitter called 'Chalabi Plot'. It was amazing to see such a response. But we're curious, among those patients who achieved complete response so far, did you see any relapse?

Dr. Myriam Chalabi: Short answer, no. we're waiting, of course on the disease-free survival data, the three-year DFS data for NICHE-2, and we hope to have that by the end of this year, beginning of next year. But as of now, we showed that data, and so far, we haven't seen any recurrences in, actually, any of the patients treated in NICHE-2.

Dr. Mohamed Salem: Fantastic. Dr. Cercek. So I think your slide -- I remember clearly from the ASCO presentation -- was all complete response, every single patient. Same question, did you see any relapse so far?

Dr. Andrea Cercek: So far, no, we have not.

Dr. Mohamed Salem: Amazing. So, Dr. Cercek, as you know, and obviously, this is metastatic disease, but in KEYNOTE-177, as you know, about 30% of patients with MSI-high tumors did not respond to checkpoint inhibitors. So that makes some of us feel nervous about using checkpoint inhibitors alone in colorectal cancer, even with MSI-high status. I was curious if you can comment on this and if there is a way we can perhaps sort out who actually is likely to respond and who is likely not going to respond.

Dr. Andrea Cercek: I think that's a really important question and an excellent point. And we believe that the difference lies in the fact that in KEYNOTE-177, the patients had metastatic disease, whereas in our neoadjuvant studies that we're discussing, they have early-stage disease. And whether that has to do with the tumor differences, young tumors versus older tumors once they become metastatic, or the microenvironment, remains to be determined. But certainly, there is this pattern of incredible responses with checkpoint inhibitors in early-stage dMMR tumors. And in KEYNOTE-177, as you mentioned, about 30% of patients progressed. And I think we don't know why that is. We are seeing this, about a third of progressors repeatedly in the metastatic setting with checkpoint inhibitors. And so perhaps there is a population. But whether this is driven by genomics or something else, we don't know.

Dr. Mohamed Salem: Great. So, along the same lines, especially rectal cancer, obviously, because surgical resection is a key component in the treatment paradigm, do you feel patients who achieve pathological complete response should still go under surgical resection or should go under the 'watch and wait' approach?

Dr. Andrea Cercek: In general, I'm a fan of organ preservation. I think in rectal cancer, the reasons are obvious. It's a challenging surgery. It's very toxic to the patients. It changes their lives forever. In survivorship, 30% of them require a permanent colostomy because of the location of the tumor. So there, the field of rectal cancer, in general, is moving towards non-operative management, even in the MSI-proficient patients, by trying to optimize therapy to increase clinical complete responses and therefore omit surgery. So that's the difference with rectal cancer.

In colon cancer, it's a different discussion. I think for many patients, surgery is very straightforward. It's a hemicolectomy. It doesn't alter lifestyle in survivorship, so it's not as morbid as it is in rectal cancer. Of course, I think if a patient is older with MSI-deficient tumor perhaps can undergo surgery, then clinical complete responses become critical because then we can monitor them after just checkpoint blockade, and they don't need surgery.

The challenge there, and I would love to hear Dr. Chalabi's comments on this, too, is just that imaging is challenging. We have a hard time in colon cancer determining whether someone has a clinical complete response or not. It seems to be very different than in rectal cancer, where with endoscopy and with the rectal MRI, we really can't tell whether the tumor is still present or not. This remains a challenge in colon cancer.

Dr. Mohamed Salem: Dr. Chalabi, I would like to hear your thoughts and also how you practice in Europe. I don't know if it's the same like here in US or different.

Dr. Myriam Chalabi: I completely agree with Dr. Cercek. Well, if we look at the rectal cancer patients, I think this is fantastic. That even though this is a small population achieving this high clinical complete response rate, not having to operate or even give any chemotherapy or radiation therapy to these patients, it is extremely important both in the short term but also in terms of long-term complications and morbidity.

When it comes to the colon cancer responses that we're seeing in NICHE, those are all pathologic responses, of course. And we have been evaluating also preoperatively using scans to see whether we can assess these complete responses based on imaging. That doesn't seem to be the case. We do see responses in all patients, so we see these are all very large bulky tumors that we're treating in NICHE-2. And we do see responses in almost all of these patients, but it's not close to complete responses, definitely not in all of the complete responders that we're seeing. So that makes it difficult.

And the question is, what if we would be waiting or treating longer because these bulky tumors need more time to disappear or to be cleared before you're going to see it on the imaging? So that is a question that I don't have an answer to just yet. We may be getting some more data on that with the currently ongoing trials. And as Dr. Cercek pointed out, the endoscopies when you have a right-sided colon tumor are different than doing just a sigmoidoscopy for a rectal tumor.

So, we actually do have one patient who hasn't undergone surgery, and that is actually a patient with an MMR-proficient tumor within the NICHE trial who had a complete response. And that patient has a sigmoidal tumor, and he actually had toxicities which prevented him from undergoing timely surgery and now has a complete response after two years, both endoscopically and on imaging. So, he hasn't undergone surgery, and that is a great example of how we may be doing this in the future. It's an interesting case within the trial to follow and see how we can do it in the future.

Dr. Mohamed Salem: That's fascinating news. So, was it MMR-proficient?

Dr. Myriam Chalabi: Yes, this is an MMR-proficient tumor.

Dr. Mohamed Salem Wow. Any particular biomarkers that you think he or she had to predict that?

Dr. Myriam Chalabi: We have treated more patients with MMR-proficient tumors. We have 31 patients, and we have seen actually responses in 9 out of 31 patients in the MMR-proficient tumors with the same combination of two doses of nivolumab and one of ipilimumab. We previously published on half of the cohort approximately on what the possible predictive biomarkers of response could be, and that was a costimulation for CD8 and PD-1. So PD-1 positive CD8 T cells. And we're currently doing the same work for the rest of the cohort. So hopefully, we'll be able to show that soon and see whether this still stands for the completed MMR-proficient cohort. But definitely also very exciting data for the MMR-proficient.

Dr. Mohamed Salem: So, this is actually a very good segue to my next question because I know all of us are looking for this. Like, obviously, we're seeing a fascinating response in those patients with MSI-high tumors, but majority of colorectal cancer, as you know, they actually have MSS-proficient tumors. Any thoughts about how we can overcome the primary resistance for this tumor to checkpoint inhibitors? So let me start with you, Dr. Cercek.

Dr. Andrea Cercek: I'm very much looking forward to Dr. Chalabi's data on this because, honestly, we have not seen such amazing responses to immunotherapy in MSS tumors. The initial studies were complete flatline, no responses at all. And here, she just described a patient that had a complete response to just a month of checkpoint inhibitors. So that's phenomenal, and hopefully, we'll learn from the responders.

We believe that there is a subpopulation of MSS colorectal cancer that is more immune sensitive, immune hot, whichever term you like to use. And it's just a matter of appropriately identifying those patients. And personally, I think the answer lies in the neoadjuvant setting in early tumors where they're treatment-naive, not exposed to chemo, not exposed to radiation, younger, have their innate microenvironment. And so, I think it's likely a combination of the above. But obviously, the ultimate goal is to find out who those patients are and then potentially treat them just like this with immunotherapy. And that would be another nice chunk of the pie where we could utilize immunotherapy for our patients.

Dr. Mohamed Salem: Very true. Dr. Chalabi, especially with your experience and just showing there is a chance for those people to respond, what are your thoughts about how we can overcome this primary resistance?

Dr. Myriam Chalabi: It's great to be here with Dr. Cercek because, obviously, we have very similar interests but it's also good to see that we think the same way because I completely agree with what she just said in terms of neoadjuvant. I think that was one of the most important things that we did here, giving this neoadjuvant treatment in non-metastatic tumors. It's probably a very important driver in the responses that we're seeing. So, we've been seeing data now a bit more in the metastatic disease setting where MSS tumors seem to be responding to new generations of checkpoint blockade. And the question is how those would do in the neoadjuvant setting that would be even different than what we're seeing now. But there's definitely some proof of MSS tumors that can respond to immunotherapy.

The question on how to overcome the primary resistance, I think that question is for us: Who are the patients with primary resistant tumors and why are they primarily resistant? And then we can think about how to change that and how to change them into the tumors that are responding. I think these types of data will be key to understand more and know; hopefully, even you said, in the metastatic disease setting, to make these tumors more pliable in response to immunotherapy.

Dr. Mohamed Salem: I agree. So, both of you are leading us toward how to choose the right patient with the right target for the right treatment. That's an amazing journey you're taking all of us on.

So, Dr. Cercek, I have to admit that with your data, it created some problems for us in the clinic because all patients the following day came in asking for immunotherapy. We had a hard time trying to explain that maybe this is not the right treatment for them or, like, not the right platform. But I wanted to ask you, if we'll have a patient tomorrow in the clinic with localized rectal cancer and happen to have an MSI-high tumor, what would be your recommendation in terms of how to approach that patient?

Dr. Andrea Cercek: I think, ideally, you would discuss clinical trials with the patient. We have opened the study now to not just rectal cancer but colon cancer and, in fact, all solid tumors that are mismatch repair-deficient. So I think at this time, the patients really should be treated on a clinical trial. As we learn more, in particular, until we are more comfortable assessing for a clinical complete response and follow-up. I think the surveillance piece will be critically important. In rectal cancer, it's well established, but it's not in the other tumor types. So my recommendation would be to enroll the patient on a trial.

Dr. Mohamed Salem: Just to add to that too, obviously, as you know, there is now the cooperative group trial that's looking at that option and we obviously encourage all centers to participate and open that study to have this option for our patients. Dr. Chalabi, so what do you guys do in Europe for these patients?

Dr. Myriam Chalabi: In Europe, it's a very different situation. I would have answered this question differently by saying, well, we don't have that option of treating patients outside of clinical trials. So basically, we have to make sure that we have clinical trials for these patients. And that's something that we've had for colon cancer patients. That is still the case. And we're getting rectal cancer trials also for patients with MMR deficient tumors and have those also for MMR proficient tumors. For us and I agree completely that we should be treating patients within clinical trials, we don't have another option. But still, even if we did, I think it's important to create data within clinical trials to be able to ultimately also show why this should be standard of care and how we can make it standard of care. Because if you're not accumulating that data, then it's going to become very difficult if accrual is lacking. Now, we treat patients either with standard-of-care treatments, but usually, we try to find something within clinical trials.

Dr. Mohamed Salem: I totally agree. And as we always say, the standard of care should be a clinical trial participation. So, I must say, both of you, Dr. Cercek and Dr. Chalabi, you made 2022 a very exciting year for us in GI cancers. You really changed the way we look at how to treat these patients and give them a huge chance of, I would say, actually cure and obviously organ preservation. So, I'm very curious to know what you are both are working on now and what we should expect in 2023 and 2024.

Dr. Andrea Cercek: So, for me, the study is ongoing, as I mentioned, and we've expanded to all mismatch repair-deficient solid tumors with the same approach of six months of dostarlimab and then the option of nonoperative management. And I think that it'll be important for us to learn in terms of responses on the luminal versus some of the other tumor types, like, for example, pancreas cancer, where we don't see these robust responses in the metastatic setting, that will be important to do. We're doing some correlative analysis, as Dr. Chalabi described as well in our patients.

And then, I'm interested in optimizing neoadjuvant approaches to minimize therapy in rectal cancer specifically. So, we have a study now for HER-2 amplified RAS wild-type patients with locally advanced rectal cancer with a similar approach of utilizing HER-2 targeted therapy first and then in combination with chemotherapy. In our case, it's a combination of trastuzumab and tucatinib and then chemotherapy with CAPOX and assessing for response and potential omission of radiation and surgery depending on responders. So, I'm very excited that study is open and actively accruing, and hopefully, we can get similar responses that we did in the MSI population with PD-1 blockade.

Dr. Mohamed Salem: Is that only available at MSK?

Dr. Andrea Cercek: It is at this time. However, we will likely be expanding, so if there's any interest, let me know.

Dr. Mohamed Salem: Great. I'm sure many centers will be. Great. What about you, Dr. Chalabi? Any sneak peek in the future?

Dr. Myriam Chalabi: So many sneak peeks, where to begin? I think it's very exciting to be working in this space at this time, and we're very lucky to be in it. So, for NICHE, we're actually accruing now in new cohorts for both MMR-deficient and MMR-proficient tumors. For the patients with MMR-deficient tumors, we're actually testing a new combination of nivolumab plus relatlimab, so anti-LAG-3 plus anti-PD1. And we're testing the same co-formulation in patients with pMMR tumors. In addition to another cohort for the pMMR tumors with nivolumab, all within this window of opportunity, as we did previously in NICHE, and to see if we're going to see more responses if these are going to be different tumors than the ones responding to nivolumab and ipilimumab.

And for the MMR deficient tumors, we're treating longer with this combination now. So, we're operating after eight weeks instead of six weeks. We're giving two cycles, four weekly cycles, to see whether we can even improve the PCR rates, even though this is, of course, a different combination treatment. So, very exciting times for NICHE, and we'll have the readout for the DFS at the end of this year, so that's also very exciting.

And then, well, it's similar to Dr. Cercek. So again, we're on the same page when it comes to these neoadjuvant treatments. We have actually an ongoing trial for neoadjuvant treatment of patients with MMR proficient rectal cancers, and that is using a combination of radiation therapy followed by a combination of atezolizumab or anti-PDL1 with Bevacizumab with the aim of organ sparing approach in these patients. And we actually presented stage 1 of this trial as a poster at ASCO GI, showing that we achieved 56% complete or near complete responses clinically at 12 weeks. And after at least a year of follow-up for all patients, we have 50% organ preservation. So those are very exciting data as well.

Also, in the MMR proficient tumors, I'm very excited to hear about the HER-2-positive tumors and Dr. Cercek's study. So there's definitely a lot going on that we hope to share as soon as the data are available.

Dr. Mohamed Salem: We'll be looking forward to your next presentation and seeing that. So again, most of your work showed us that we really have to choose the right patient with the right target for the right treatment to achieve the best possible outcome. So we're getting short on time here. But before we conclude, ASCO Daily News Podcast has a huge audience of oncologists, I wanted to give you the chance to share anything you'd like to share with our audience today before we finish. Dr. Cercek?

Dr. Andrea Cercek: I believe this is an incredibly exciting time in colorectal cancer. I think it's finally our turn, which feels really nice, and obviously, we have a lot more work that needs to be done. But my personal belief is to keep trying to chip away at the pie and identify responders and keep working to have better-targeted drugs and better treatment options that will improve responses and improve outcomes for our patients. But I certainly believe that we are well on our way there, and it's very exciting.

Dr. Mohamed Salem: I totally agree. Dr. Chalabi, any thoughts?

Dr. Myriam Chalabi: I think after 2022 and the data that we've been showing, I think it's important to– and I think by now, maybe it's not even necessary anymore to say it– but I think it's important to really look at the tumors and look at these MMR proteins or MSI, and to make sure that you're treating the patient in the right way, and to consider that. Before, it wasn't as important in the neoadjuvant setting or these localized tumors, but now it's becoming essential.

And I think if you would have looked five years ago and you would say, yeah, these MSI tumors are important to find, it's a very small proportion of patients, in rectal cancer even lower than in colon cancer. But still, it has such a huge impact on what you're doing in these patients and your chances of cure. So I think that would be my most important giveaway to test for MMR deficiency before deciding on a treatment for your patients. And we're working on trials with neoadjuvant immunotherapy. Also in other tumor types, Dr. Cercek is also doing the same. I think those will be very important also outside of the GI field to see whether this approach works for a much larger patient population, despite the low incidence.

Dr. Andrea Cercek: Dr. Chalabi just made a critical point that that is most important is to remember that we do have biomarkers in colorectal cancer that, in the neoadjuvant setting and in the metastatic setting, especially MSI, that we need to test for. And then, just to add from a clinical perspective, in rectal cancer, the large majority of patients that have mismatch-repair deficient or MSI tumors actually have Lynch syndrome. So really, if you identify a patient that's mismatch-repair deficient or MSI-high anywhere, but especially in the rectum, they absolutely should get germline testing.

Dr. Mohamed Salem: I echo that and second that. And Dr. Cercek, thank you, and I know you did a lot of work in colorectal cancer in the younger adult population, too, so I think you've had a huge impact on that area too.

I would like to thank both of you again for being here today, but more for the great work you and your teams are doing to advance the field. It's really a very exciting time in GI cancers now, and thank you so much for your work and for sharing your insights with us today on the ASCO Daily News Podcast.

Dr. Myriam Chalabi: Thank you so much for having me. It's been great.

Dr. Andrea Cercek: Thank you for having me.

Dr. Mohamed Salem: Of course, and thanks to our listeners for your time today. If you value the insights that you hear on the ASCO Daily News Podcast, please take a moment to rate, review, and subscribe wherever you get your podcasts. Thank you very much.

Disclaimer:

The purpose of this podcast is to educate and to inform. This is not a substitute for professional medical care and is not intended for use in the diagnosis or treatment of individual conditions. Guests on this podcast express their own opinions, experience, and conclusions. Guest statements on the podcast do not express the opinions of ASCO. The mention of any product, service, organization, activity, or therapy should not be construed as an ASCO endorsement.

Find out more about today's speakers:

Dr. Mohamed Salem

@SalemGIOncDoc

Dr. Myriam Chalabi

@MyriamChalabi

Dr. Andrea Cercek

@AndreaCercek

Learn about other key advances in GI Oncology:

SWOG 1815, PARADIGM, and Other Advances at GI23

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Disclosures:

Dr. Mohamed Salem:

Consulting or Advisory Role: Taiho Pharmaceutical, Exelixis, Bristol-Myers Squibb, Exelixis, QED Therapeutics, Novartis, Pfizer, Daiichi Sankyo/Astra Zeneca

Speakers' Bureau: Genentech/Roche, Taiho Pharmaceutical, Daiichi Sankyo/Astra Zeneca, BMS, Merck

Dr. Myriam Chalabi:

Consulting or Advisory Role: MSD, Bristol-Myers Squibb/Celegne, Numab

Research Funding (Institution): Bristol-Myers Squibb, Roche/Genentech, MSD

Travel, Accommodations, Expenses: Roche/Genentech, Bristol-Myers Squibb

Dr. Andrea Cercek:

Consulting or Advisory Role: Bayer, GSK, Incyte, Merck, Janssen, Seattle Genetics, G1 Therapeutics

Research Funding (Institution): Seattle Genetics, GSK, Rgenix