JCO Article Insights: Back to the Drawing Board: Overcoming Resistance to PD-1 Blockade

In this episode of JCO Article Insights, Rohit Singh interviews Dr. Ticiana Leal on the editorial, "Back to the Drawing Board: Overcoming Resistance to PD-1 Blockade."

TRANSCRIPT

The guests' disclosures can be found in the transcript.

Dr. Rohit Singh: Hello and welcome to JCO’s Article Insights. I am your host Rohit Singh and today we will be discussing the JCO article, “Back to the Drawing Board: Overcoming Resistance to PD-1 Blockade.” And we are joined by the senior author of the article, Dr. Ticiana Leal. Dr. Leal is an Associate Professor in the Department of Hematology and Medical Oncology at Emory University School of Medicine, and she serves as director of Thoracic Medical Thoracic Oncology Medical Program and Multidisciplinary Thoracic Oncology Leader at the Winship Cancer Institute. She also served as a member of the Board of Directors at the Georgia Society of Clinical Oncology. 

Dr. Leal, welcome to our podcast and thank you for joining us.

Dr. Ticiana Leal: Thank you, Rohit. Thank you for this interesting opportunity to discuss our editorial. My co-authors and I are very glad to be here today. So, Dr. Jennifer Carlisle and Dr. Liu were co-authors with me on this editorial.

Dr. Rohit Singh: It's a really good article. And just for our audiences, the article again, titled “Back to the Drawing Board: Overcoming Resistance to PD-1 Blockade,” it discusses the challenges and the potential strategies for overcoming resistance to immune checkbox inhibitors in patients with non-small cell lung cancer. In this article, Dr. Leal and colleagues talk about the second line of drug when the patient developed disease progression while immunotherapy and they develop resistance and their definitions and what to do. 

So, to Dr. Leal, can you please explain the mechanisms of primary and acquired resistance to immune check prohibitors in non-small cell lung cancer? I also saw in your article you proposed the definition of immunotherapy resistance in solid tumors, distinguishing between primary resistance and acquired resistance. So, if you can please share your thoughts and explain their mechanism.

Dr. Ticiana Leal: So primary resistance and acquired resistance are related to tumor intrinsic and tumor extrinsic factors. And this is mainly clinically defined as of now according to previous response patterns and timing of occurrence, and these definitions can be heterogeneous, and we certainly think that biologically they can be very different. And it can be different according to prior therapy, whether patients got immunotherapy as PD-1, PD-L1 inhibitor alone or combination strategy with CTLA-4, or the combination with chemotherapy. But the patterns of resistance can be very different and can be based on defects and antigen presentation. It can also be due to tumor microenvironment immunosuppressive effects, and there are also additional inhibitory checkpoints that can be involved. 

The definition in terms of when to call it primary or acquired resistance at this point has really been based on consensus guidelines by SITC, by Esmo, as well as our group Lung-MAP has developed clinical trials in this space. Specifically, through Lung-MAP, we've defined and incorporated the definition of acquired resistance as patients who have had prior exposure of 84 days or greater and then have had progression of their disease. 

Dr. Rohit Singh: I can see why it is so challenging to come up with a standard definition for immune checkpoint resistance and I think incorporating these definitions and predictive biomarkers for clinical trial design is going to be more important going forward. Your article talks about CONTACT-01 study, so can you please discuss the CONTACT-01 study and how the shifting treatment paradigm in the first-time study impacted it and at the same time also discuss the potential implication of the differential outcome observed between the men and women in the CONTACT-01 study.

Dr. Ticiana Leal: CONTACT-01 was a much-awaited study. The authors, Dr. Neal et al, looked at a very important question in the area of immunotherapy resistance. So, CONTACT-01 was a randomized phase three global study that investigated the combination of cabozantinib plus atezolizumab versus docetaxel in patients previously treated with chemotherapy and immunotherapy. And as background, cabozantinib is an inhibitor of multiple receptor tyrosine kinases including VEGFR-2, MET, RET and TAM family kinases. Preclinically, cabozantinib could lead to immuno permissive tumor microenvironment and so it was rational to combine it with a PD-1 inhibitor. In early results of a phase 1B expanded cohort of COSMIC-021 showed really promising results of this combination which led to the rationale of CONTACT-01. In this study, however, patients that were included had different prior treatment sequences. They could have had prior immunotherapy alone followed by chemo or the opposite, or they could have had prior immunotherapy and then upon progression gotten a combination of immunotherapy plus chemotherapy. That to say that immunotherapy rechallenge is something that people are doing in clinical practice given the unmet need and the desire to overcome immunotherapy resistance. But perhaps that also includes a more resistant population of patients, and these patients certainly could have had heterogeneous mechanisms of resistance which could have impacted these results.  

The study did not meet the primary endpoint of overall survival. We saw a median overall survival of 10.7 months with the combination of atezo plus cabo and 10.5 months with docetaxel alone. In terms of the differences between sex that we saw in the CONTACT-01 study, just to go back in terms of the preclinical studies that have been done, there have been some preclinical studies that demonstrated that perhaps there may be some biological differences in models of different genders in mice. However, in the clinical setting, there have been, I think, contradicting results. A meta-analysis showed that perhaps women derive less benefit than men. Other studies have shown that perhaps women have more adverse events to immunotherapy. In this study specifically, only about 20% of the patients enrolled were women and the majority actually had non squamous histology. And we saw here less benefit for immunotherapy in women. But again, I think the numbers here are quite small. This is an exploratory analysis and I do think it highlights though the importance of making sure that we include populations and have higher rates of accrual, not only in women, but in other representative populations. In this study, only about 1% of the patients were black.

Dr. Rohit Singh: Yeah. Thank you so much for highlighting those disparities. I think it's very important to make sure that we have proper representation of all the groups in our trials. I think based on just coming off the VEGF inhibitors, I think the Lung-MAP trial S1800A, showed a significant improvement in median OS with the combination of pembrolizumab and ramucirumab compared to standard of care. Do you envision any future commission therapies targeting the VEGF pathway with immune prohibitors in non-small cell lung cancer? 

Dr. Ticiana Leal: I definitely think that targeting VEGF with multikinase TKIs based on the studies that we have seen, several now randomized phase 3 studies showing that this strategy is ineffective. So, this has been quite disappointing. But we've now seen the results of CONTACT-01, that we're just discussing here, but also other studies, including SAPPHIRE, which was also a randomized phase 3 that investigated nivolumab plus another VEGF multikinase TKI, sitravatinib. And then we also saw LEAP-008, which was a negative study investigating lenvatinib plus pembrolizumab. There still is a question though, whether you can target the VEGF pathway inhibition with a monoclonal antibody, so that's ramucirumab targeting VEGFR-2 plus ICI, and whether that can actually be an effective strategy. In our Lung-MAP trial, the S1800A, this study was a randomized phase 2. Here we used the definition of acquired resistance of patients receiving prior immune checkpoint inhibitor for a minimum of 84 days, and they were randomized to the combination of pembrolizumab plus ramucirumab versus investigator’s choice of standard of care, which did include docetaxel, ramucirumab, docetaxel gemcitabine and methotrexate. This was a positive study. It led to significant improvement in median overall survival and there weren't any significant safety signals here. And we're waiting for another confirmatory study called the Pragmatica-Lung study. 

Dr. Rohit Singh: Yeah, I did have one patient who raced through pembro, and I utilized this combination and was able to get some responses. 

You mentioned Pragmatica-Lung trial. Can you provide more information about the ongoing Pragmatica-Lung trial and its potential impact on the treatment paradigm?

Dr. Ticiana Leal: Yeah, the Pragmatica-Lung trial is an ongoing study, S2302. This is an effort that is ongoing. Dr. Karen Reckamp is the chair of this study. And this is a study that actually has a very, I think, modern study design. The term Pragmatica, this is an effort that is supported by the NCI to really propose a clinical trial design that is pragmatic to promote diversity and inclusion in clinical trials. The aim of this trial specifically is to validate what we saw in terms of overall survival in S1800A. So, in this study, patients with previously treated advanced non-small cell lung cancer are randomized 1:1 to the combination of pembrolizumab plus ramucirumab versus standard of care for patients previously treated with immunotherapy and chemotherapy for stage 4 recurrent non-small cell lung cancer. Primary endpoint here is overall survival. And I think this kind of highlights what we were talking about in terms of empowering investigators to treat patients in a clinical trial more so like a real-world setting. And I think this can be paradigm changing and decrease barriers to enrollment and also include now the real-world population that we see in clinical practice.

Dr. Rohit Singh: Yeah, changing gears a little bit. I think your article also mentioned other agents that have been tested in ICI resistance settings, like lenvatinib-sitra. However, those trials results have been disappointing. What are the possible reasons behind those dose point results with multikinase inhibitors? 

Dr. Ticiana Leal: We saw some really interesting, promising overall survival results with these combinations in phase two setting. In the phase 1B expansion with CONTACT-01, we saw prolonged overall survival that we thought would be promising enough to investigate in a phase 3. Ultimately, I don't know because there weren't any biomarkers that we could really tease out what was going on. Again, to highlight that both in LEAP-008 as well as CONTACT-01, there was no definition of immunotherapy resistance, which could have impacted, and we did choose the definition for SAPPHIRE, that patients had to have acquired resistance and immunotherapy had to be the most recent prior therapy. Ultimately, one potential reason for why these are not effective could be that this targeting with a multikinase TKI with multiple targets is ineffective, and you really have to target VEGF more precisely, which is the case here of ramucirumab, which targets VEGFR-2, and whether there are differences between a TKI and a monoclonal antibody may also impact the outcomes here. 

Dr. Rohit Singh: You mentioned biomarkers. Do you think, are there any other potential biomarkers beyond PDL-1 or human mutation burden expression that can help us predict the response image checkpoint, especially in non-small cell lung cancer?

Dr. Ticiana Leal: I think that's a great question. I definitely think that more effort needs to be dedicated, and of course, there are multiple efforts in this direction. One of the challenges, obviously, has been to obtain tissue to do this biomarker testing in clinical trials. When you look at CONTACT-01, they did PDL-1 expression, but this was all based on archival tissue and it was all based on standard of care, local testing. So, a lot of heterogeneity there, and certainly using PDL-1 at baseline from initial diagnosis for a second line trial may have significant flaws there. Ultimately, right now, for clinical practice, there isn't anything that's ready for prime time. But certainly, it sounds like, based on what we're seeing, that combining biomarkers is more likely to improve the accuracy. And I think a single biomarker alone is probably going to have insufficient predictive capacity. It'd be great to be able to better comprehensively characterize an individual's tumor, to individualize immunotherapy strategies in this relapse setting. 

Dr. Rohit Singh: Yeah, definitely. We need more, better biomarkers. Coming to your point of heterogeneity, PD-L1. I myself had a patient, when we got PDL expressions from one site, they gave us one to 49%. However, for the testing, I sent the patient to a further lab at outset and PDL turned out to be 80%. But that was from a different site because of the bio sets only. Yeah, to your point, it's very heterogeneous and definitely we need to be more cautious interpreting those. 

In that trial, in CONTACT-01, we have, through the patient who have oncogenetic lung cancer. Are there any plans to explore the role of immune checkpoint in oncogenetic lung cancer, especially like non-EGFR, non ALK? I know those are the ones that we have seen in multiple studies that don't respond but are other oncogenetic lung cancer is getting more and more target treatments coming out for non-small lung cancer?

Dr. Ticiana Leal: Yeah. So, for patients with driver mutations, the paradigm has been well established that if there is a driver mutation, the patient should receive the appropriate targeted therapy. Immunotherapy as monotherapy has been ineffective in a lot of the patients with driver mutations beyond EGFR and ALK, certainly RET and HER2, ROS1, or other driver mutations that we believe that immunotherapy alone is ineffective. However, we are seeing some interesting ongoing clinical trials, or completed clinical trials investigating immunotherapy in patients with driver mutations. Going back to the EGFR population, we recently saw the results of HARMONi-A, which investigated ivonescimab, which is a bispecific antibody hitting PD-1, and VEGF, that in combination with chemotherapy, improved progression free survival in patients with EGFR mutated, non-squamous, non-small cell lung cancer with progression on prior TKI treatment. So, I think it is still an area of active investigation, and I do think that ongoing trials, perhaps with different PD-1, PD-L1 combination strategies such as bispecifics may be interesting but does require investigation.

Dr. Rohit Singh: Yeah, definitely. It looks like combination therapy is going to be the most likely answer coming forward with more research, we're able to figure out the best possible treatment in this subgroup of patients. Considering the current challenges and ongoing research efforts, how do you see the field of non-small cell treatment evolving in coming years?

Dr. Ticiana Leal: This is an interesting and important question. I think it's been really exciting to be working in thoracic oncology research. We have seen that these research efforts have led to advancement in the field. I think we need to continue to partner and collaborate with institutions, partner with industry, and also with patients and patient advocates to design clinical trials that are really going to focus on the needs of our patients in clinical trials. The gap in the second line and beyond after immunotherapy failure is a significant one. So, I do think that the challenges are to continue to develop biomarkers, to really understand who will benefit from immunotherapy strategies, who benefits from combinations, and most importantly, who does nothing. I think biomarkers are going to be something that we need to continue to incorporate in clinical trials, and I do think that there's a lot of room for hope and promise in the field. We've seen some interesting results with antibody drug conjugates and the combinations there may also be of interest. And then other important strategies, we're looking at T Cell engagers and different drugs with different mechanism of actions, including CAR T and vaccines. So beyond immune checkpoint inhibitors, I think we have different classes of drugs that may lead to different treatment strategies for patients in second line and beyond. 

Dr. Rohit Singh: Yeah, certainly we have seen such extensive development in lung cancer. However, there's still a lot to be done as you just mentioned. 

Thank you so much Dr. Leal for your time and great insights discussing your article with us.

Dr. Ticiana Leal: Thank you.

Dr. Rohit Singh: Thank you for listening to JCO Article Insights. Don't forget to give us a rating or review and be sure to subscribe so you never miss an episode. You'll find all ASCO shows at asco.org/podcast.

  

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Dr. Leal Disclosures

Consulting or Advisory Role
Company name: Novocure
Company name: Amgen
Company name: Roche
Company name: AstraZeneca
Company name: Regeneron
Company name: Novocure
Company name: Takeda
Company name: Jazz Pharmaceuticals
Company name: Catalyst Pharmaceuticals
Company name: Pfizer
Company name: Janssen
Company name: Genentech
Company name: Novartis
Company name: Sanofi
Company name: BMS GmbH & Co. KG
Company name: Abbvie
Company name: OncoC4

Research Funding
Company name: Pfizer
Company name: Daiichi Sankyo/Astra Zeneca

Travel, Accommodations, Expenses
Company name: Regeneron
Company name: Sanofi