JCO at 2025 ASH: Pirtobrutinib in Untreated CLL

JCO Editor-in-Chief Dr. Jonathan Friedberg is joined by colleagues Dr. Jennifer Woyach, Dr. Wojciech Jurczak, and Dr. Matthew Davids to discuss simultaneous publications presented at ASH 2025 on pertibrutinib, a new upfront treatment option for patients with chronic lymphocytic leukemia.

TRANSCRIPT

The disclosures for guests on this podcast can be found in the show notes.

Dr. Jonathan Friedberg: I’m Jonathan Friedberg, editor of Journal of Clinical Oncology, and welcome to JCO After Hours, where we are covering two manuscripts that were presented at the American Society of Hematology meeting 2025 in Orlando, Florida. I am delighted to be joined by colleagues on this call to discuss these pivotal manuscripts which cover the topic of pirtobrutinib, a new upfront treatment option for patients with chronic lymphocytic leukemia.

I will first just introduce our guests, Dr. Woyach.

Dr. Jennifer Woyach: Hi, my name is Jennifer Woyach. I am from the Ohio State University.

Dr. Wojciech Jurczak: Hello, I am Wojciech Jurczak, working at the National Research Institute of Oncology in Krakow, Poland.

Dr. Matthew Davids: Hi, I am Matthew Davids from Dana-Farber Cancer Institute in Boston.

Dr. Jonathan Friedberg: We are going to start by just learning a little bit about these two trials that were both large, randomized phase 3 studies that I think answered some definitive questions. We will start with your study, Jennifer. If you could just describe the design of your study and the patient population.

Dr. Jennifer Woyach: Absolutely. So this is the BRUIN CLL-314 study, and this is a phase 3 randomized trial of pirtobrutinib versus ibrutinib in patients with CLL or SLL who had not previously been treated with a covalent BTK inhibitor. The patients were both treatment-naive and relapsed/refractory, about one-third of the patients treatment-naive, the rest relapsed/refractory, and they were stratified based upon 17p deletion and the number of prior lines of therapy.

The primary objective was looking at non-inferiority of overall response rate over the entire treated population as well as the relapsed/refractory patient population. Key secondary objectives included progression-free survival in the intention-to-treat and the smaller relapsed/refractory and treatment-naive populations.

Dr. Jonathan Friedberg: And just comment a little bit on the risk of the patients.

Dr. Jennifer Woyach: This study was fairly typical of this cohort of patients. Within the relapsed/refractory patient population, there was a median of one prior line of therapy in each of the groups, up to nine prior lines of therapy in the patients included on the study. For the overall cohort, about two-thirds of the patients were IGHV unmutated, about 15% had 17p deletion, 30% had TP53 mutations, and about 35% to 40% had a complex karyotype, which is three or more abnormalities.

Dr. Jonathan Friedberg: And what were your findings?

Dr. Jennifer Woyach: Regarding the primary outcome, which is the focus of the publication, we did find that pirtobrutinib was indeed non-inferior and actually superior to ibrutinib for overall response rate throughout the entire patient population and in both the relapsed/refractory and treatment-naive cohorts. PFS is a little bit immature at this time but is trending towards also being significantly better in pirtobrutinib-treated patients compared with ibrutinib-treated patients. Probably most significantly, we found this to be the case in the treatment-naive cohort where there was a striking trend to an advantage of pirtobrutinib versus ibrutinib.

Dr. Jonathan Friedberg: And the follow-up that you have on that progression-free survival?

Dr. Jennifer Woyach: So we have about 18 months follow-up on progression-free survival.

Dr. Jonathan Friedberg: The second study, Wojciech, can you just go through the design and patient population that you treated?

Dr. Wojciech Jurczak: Thank you, Dr. Friedberg, for this question. So the BRUIN CLL-313 study was, in fact, the first phase 3 study with pirtobrutinib in exclusively untreated CLL patients. It was a randomized study where we challenged pirtobrutinib versus bendamustine-rituximab. At the time we designed the protocol, bendamustine-rituximab was an option as a standard of care, and Bruton tyrosine kinase monotherapy was used far more commonly than nowadays.

The primary target of the study was progression-free survival. We took all untreated patients except for those with 17p deletions. Therefore, it is a good representation for intermediate risk. We had about 60% of the population, 56 to be precise, which was unmutated, evenly distributed into two treatment arms. 17p deleted cases were excluded, but we had about 7% and 8% of TP53 mutated patients as well as about 11% and 7%, respectively, in the pirtobrutinib and bendamustine-rituximab arm of patients with complex karyotype.

The progression-free survival was in favor of pirtobrutinib and was assessed by an independent review committee. What is important is that the progression-free survival of the bendamustine-rituximab arm was actually similar to the other studies addressing the same questions, like the comparison with ibrutinib in the ALLIANCE study or zanubrutinib in the SEQUOIA study. What was different was the hazard ratio. In our study, it was 0.20. It was one of the longest effect sizes noted in the frontline BTK study. It represented an 80% reduction in progression-free survival or death. If we compare it to ibrutinib or zanubrutinib, it was 0.39 and 0.42 respectively.

Presumably, this great effect contributed towards a trend of overall survival difference. Although survival data are not mature enough, there is a clear trend represented by three patients we lost in the pirtobrutinib arm versus 10 patients lost in the bendamustine-rituximab arm. This trend in overall survival is becoming statistically significant despite the fact that there was a possibility of crossover, and effectively 52.9 patients, which means 18 out of 34 patients relapsing in the bendamustine-rituximab arm, were treated by pirtobrutinib.

Dr. Jonathan Friedberg: I am going to turn it over to Matt. The question is: why study pirtobrutinib in this patient population? And then with these two studies, how do you find the patients that were treated, are they representative of people who you see? And do you see this maybe being approved and more widely available?

Dr. Matthew Davids: I think in terms of the first question, why study this in a frontline population, we have seen very impressive data with pirtobrutinib in a very difficult-to-treat population of CLL patients. This was from the original BRUIN phase 1/2 study where most of the patients had at least two or three lines of therapy, often both a covalent BTK inhibitor and the BCL2 inhibitor venetoclax, and yet they were still responding to pirtobrutinib. The drug was also very well tolerated in that early phase experience. And actually, we have seen phase 3 data from the BRUIN 321 study comparing pirtobrutinib to bendamustine and rituximab in a relapse population as well. So I think that really motivated these studies to look at pirtobrutinib as a first therapy. You know, often in other cancers of course, we want to use our best therapy first, and I think these studies are an initial step at looking at that.

In terms of the second question around the patient population, these are pretty representative patient populations, I would say, for most frontline CLL studies. We see patients who are a bit younger and fitter than sort of the general population of CLL patients who are treated in clinical practice, and I think that is true here as well. Median age in the sort of mid-60s here is a bit younger than the typical patients we are treating in practice. But that is not different from other CLL frontline studies that we have seen recently, so I think it makes it a little bit easier as we kind of think across studies to feel comfortable that these are relatively similar populations.

Dr. Jonathan Friedberg: How do you see this either getting regulatory approval or potentially being used compared to current standard of care options?

Dr. Matthew Davids: So my understanding is that both of these trials were designed with registrational intent in the frontline setting, and they are both positive studies. That is certainly very encouraging in terms of the potential for an approval here. We have seen in terms of the FDA recently some concerns around the proportion of patients who are coming from North America, and my understanding is that is relatively low on these two studies. But nonetheless, the datasets are very impressive, and so I think it is certainly supportive of regulatory approval for frontline pirtobrutinib.

Dr. Jonathan Friedberg: I will ask Jennifer a question. The control arm in your study was ibrutinib, and I think many in the audience may recognize that newer, second-generation BTK inhibitors like acalabrutinib and zanubrutinib are more frequently used now if monotherapy is decided. How do you respond to that, and how would you put your results in your pirtobrutinib arm in context with what has been observed with those agents?

Dr. Jennifer Woyach: Yeah, that is a great question. Even though in the United States we are predominantly using acalabrutinib or zanubrutinib when choosing a monotherapy BTK inhibitor, this is actually not the case throughout the entire world where ibrutinib is still used very frequently. The head-to-head studies of both acalabrutinib and zanubrutinib compared to ibrutinib have shown us pretty well what the safety profile and efficacy profile of the second-generation BTK inhibitors is.

So even though we do not have a head-to-head study of acalabrutinib or zanubrutinib versus pirtobrutinib, I think, given the entirety of data that we have with all of the covalent BTK inhibitors, I think we can safely look at the pirtobrutinib arm here, how the ibrutinib arm compares or performs in context with those other clinical trials. And though we really can not say anything about pirtobrutinib versus acalabrutinib or zanubrutinib, I think we can still get a good idea of what might be the clinical scenarios in which you might want to choose pirtobrutinib.

Dr. Jonathan Friedberg: And Wojciech, do you agree with that? Obviously, I think you have acknowledged that chemoimmunotherapy is rarely used anymore as part of upfront treatment for CLL. So, I guess a similar question. If you were to put the pirtobrutinib result in your study in context with, I guess, more contemporary type controls, would you agree that it is competitive?

Dr. Wojciech Jurczak: Well, I think that that was the last study ever where bendamustine-rituximab was used as a comparator arm. So we should notice that smashing difference. Because if we look at the progression-free survival at two years, we have 93.4% in pirtobrutinib arm versus 70.7% in bendamustine-rituximab arm. Bendamustine-rituximab arm did the same as in the other trials, like ALLIANCE or SEQUOIA. Pirtobrutinib did exceptionally well, as pirto is not just the very best BTK inhibitor overcoming the resistance, but perhaps even more important for the first line, it is very well tolerated and is a very selective drug.

Now, if we look at treatment-related adverse events, the discontinuation rate, they were hardly ever seen. If we compared the adverse events in exposure-adjusted incidence, literally all adverse events were two or three times higher in bendamustine-rituximab arm except for the bleeding tendency, which however was predominantly in CTCAE grade 1 and 2 with just 0.7% of grade 3 hemorrhage. Therefore, I think that we should actually put the best and the safest drugs upfront if we may, and pirtobrutinib is, or should be, the first choice if we choose monotherapy.

Now, I understand that we are not presenting you the data of pirtobrutinib in combination with anti-CD20 or with BCL2 inhibitors, but that is to come.

Dr. Jonathan Friedberg: Matt, how would you envision, were regulatory approval granted and this were an option, using this in the upfront patient population? Is there anybody who you would preferentially use this or start on this treatment? Or would this be something that you would tend to reserve for second line?

Dr. Matthew Davids: So I would say that in general for most of my patients who would want to start with a continuous BTK inhibitor, I would still use a covalent BTK inhibitor, and I say that for a couple of reasons despite the very promising data from these studies. The first is that the follow-up for both of these phase 3 trials is still quite short, in the range of a median 18 to 24 months. And we know that CLL is a marathon, not a sprint, and these patients are going to probably be living for a very long time. And we do have much longer follow-up from the covalent BTK inhibitors, median of 10-year follow-up with ibrutinib and five to six years with zanubrutinib and acalabrutinib respectively. And you know, I do not think that the pirtobrutinib is going to fall off a cliff after two years, but on the other hand, I think there is a lot of value to long-term data in this disease, and that is why I think for most of my patients I would stick with covalent BTK inhibitors.

But the other important factor that we need to consider is patients who are younger and may have many different CLL treatments over the years. We have to be very careful, I think, about how we sequence these drugs. We know right now that we can start with covalent BTK inhibitors and then subsequently patients will respond well to the non-covalent inhibitor pirtobrutinib in later lines of therapy. But right now we do not have prospective data the other way around. So how will the patients on these studies who progress on pirtobrutinib respond to covalent BTK inhibitors? We do not know yet. There have not been a lot of progression events, which is great, but we would like to see some data in that respect to feel more comfortable with that sequence.

Now, I do think that particularly for older patients and those who have significant cardiovascular comorbidities, if they wanted to go on a continuous BTK inhibitor, I do think these data really strongly support using pirtobrutinib as the BTK inhibitor of choice in that population. In particular, the cardiovascular risks with pirtobrutinib seem to be quite low. I was very struck in the comparison with BR that the rate of AFib was equivalent between the two arms of the study. And that is really the first time we have seen that with any of these BTK inhibitors, no elevated risk of AFib in a randomized study. I think that is the population where it will get the most traction first, is the upfront, sort of older patient with significant cardiovascular comorbidities. And as the data from these studies mature, I think that we will start to see more widespread use of pirtobrutinib in the frontline setting.

Dr. Jonathan Friedberg: Jennifer, I am just curious if you have any personal experience or heard anecdotally about after progression on pirtobrutinib the use of other BTK inhibitors and whether there is a growing experience there.

Dr. Jennifer Woyach: I do not think that there is much clinical experience, you know, as Matt alluded to, it certainly has not been tested yet. There has been some data in relapsed CLL suggesting that in people who have resistance mutations to covalent BTK inhibitors after treatment with pirtobrutinib, sometimes those mutations go away. I think most of us are concerned that they are probably not actually gone but maybe in compartments that we just have not sampled, suggesting that sort of approach where you might sequence a covalent inhibitor after a non-covalent in somebody who had already been resistant probably would not work that well.

But, you know, in this setting where people had never been exposed to a covalent BTK inhibitor before, we really have no idea what the resistance patterns are going to be like. We assume they will be the same as what we have seen in relapsed CLL, but I think we just need some longer follow-up to know for sure.

Dr. Wojciech Jurczak: If I may confront Dr. Davids about the use of covalent BTK inhibitors upfront, well, I think that we should abandon the idea of using the first and the second and the third generation, at least if we don’t have medical lines. If we endlessly block the same pathway, it is not going to be effective. So if pirtobrutinib gets approval in first, second line, we do not necessarily have to use it in the first line. I am not here in a position to defend that we should treat patients with pirtobrutinib upfront and not BCL2 time-limited regimen.

However, the way I look at CLL patients when choosing therapy is not just how should I treat them now, but what would be the best regimen in 5, 10 years if I have to re-treat them. And in some instances, the idea may be that in this setting we would like to have a BTK inhibitor upfront to have a BCL2 inhibitor later to make it time-limited. Although I understand and I agree with Matthew that if we have an elderly, fragile population, then the charm of having a drug taken once a day in a tablet with literally few cardiovascular adverse events might be an option.

Dr. Jonathan Friedberg: And I will give Matt the last word whether he wants to respond to that, and also just as a forward-looking issue, I know both investigators have implied that there will be future studies looking at combinations with pirtobrutinib, and if you have any sense as to what you would be looking for there.

Dr. Matthew Davids: The field really is heading toward time-limited therapy for most patients, I would say. There is a bit of a discrepancy right now in the field between sort of what we are doing in academic practice and what is done sort of more widely in community practice. And so right now we are going to see evolving datasets comparing these approaches. We are already seeing data now from the CLL17 study with ibrutinib comparing continuous to time-limited venetoclax-based therapy, and we are seeing similar efficacy benefits from these time-limited therapies without the need for continuous treatment. And so that is where I think some of the future studies with pirtobrutinib combining it with venetoclax and other partners are so important. Fortunately, several of these studies are already ongoing, including a phase 3 trial called CLL18, which is looking at pirtobrutinib with venetoclax, comparing that to venetoclax and obinutuzumab. So I am optimistic that we are going to be developing these very robust datasets where we can actually use pirtobrutinib in the frontline setting as a time-limited therapy as a component of a multi-drug regimen. So far, those early data are very promising.

Dr. Wojciech Jurczak: Perhaps last but not least, in a single center we have treated over 300 patients with pirtobrutinib. So eventually some of them relapsed. And I must say that our experience on BCL2 inhibitors, not just venetoclax but including sonrotoclax, are appealingly good. Therefore, by using pirtobrutinib even earlier, we do not block the efficacy of other compounds.

Dr. Jonathan Friedberg: All right.

Well, I want to thank all of our speakers. I also want to congratulate our two guests who presented these very influential papers at the ASH Annual Meeting, and chose to publish them in JCO, so we thank you for that, and Dr. Davids for your commentary - really appreciated.

That is this episode of JCO After Hours. Thank you for your attention.

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.

 

Disclosures

Dr. Wojciech Jurczak

Consulting or Advisory Role: BeiGene, Lilly, Abbvie/Genentech, Takeda, Roche, AstraZeneca

Research Funding: Roche, Takeda, Janssen-Cilag, BeiGene, AstraZeneca, Lilly, Abbvie/Genentech

Dr. Jennifer Woyach

Consulting or Advisory Role: Pharmacyclics, Janssen, AstraZeneca, Beigene, Loxo, Newave Pharmaceutical, Genentech, Abbvie, Merck

Research Funding: Company name: Janssen, Schrodinger, beone, Abbvie, Merck, Loxo/Lilly

Dr. Matthew Davids

Honoraria: Curio Science, Aptitude Health, Bio Ascend, PlatformQ Health, Plexus

Consulting or Advisory Role: Genentech, Janssen, Abbvie, AstraZeneca, Adaptive Biotechnologies, Ascentage Pharma, BeiGene, Lilly, Bristol-Myers Squibb, Genmab, Merck, MEI Pharma, Nuvalent, Inc., Galapagos NV, Schroedinger

Research Funding: Ascentage Pharma, Novartis, MEI Pharma, AstraZeneca