Foundational Issues Related to Immunotherapy and Melanoma

Transcription

1 Transcript Details This is a transcript of a continuing medical education (CME) activity accessible on the ReachMD network. Additional media formats for the activity and full activity details (including sponsor and supporter, disclosures, and instructions for claiming credit) are available by visiting: Released: 12/29/2015 Valid until: 12/29/2016 Time needed to complete: 15 Minutes ReachMD info@reachmd.com (866) Foundational Issues Related to Immunotherapy and Melanoma ANNOUNCER OPEN: Welcome to Project Oncology on ReachMD. This segment, entitled Foundational Issues Related to Immunotherapy and Melanoma is provided by Prova Education. Prior to beginning the activity, please be sure to review the faculty and commercial support disclosure statements as well as the Learning Objectives. Or if you re listening to this as a podcast, go to this activity on ReachMD.com forward slash Project Oncology on your computer, smart phone or tablet device. Dr. Flaherty: Hello, this is Keith Flaherty from the Massachusetts General Hospital Cancer Center in Boston, Massachusetts. It's my pleasure to present this data on Foundational Issues Related to Immunotherapy and Melanoma ReachMD Page 1 of 8

2 I'd first like to review some of the biology that is responsible for the revolution in terms of understanding the immune system, how it is that cancer cells can evade the immune system, and the basis for the therapeutic successes that have been observed in the past few years, particularly pertinent to patients with melanoma. Shown here are the data and some of the mechanisms that we think are really critical to how it is that T- cell activation and inactivation have really come to the fore in terms of our new understanding about how it is that immune cells can recognize cancer and how their function can be impeded. Most importantly, and shown here on the left-hand side of the slide, are 2 of the negative regulators of immune cell function, so-called CTLA4 and PD-1. These are natural breaks on immune cell and particular T-cell activation, T- cells being the branch of the immune system that we know can recognize cancer cells and even destroy them. Antibodies that block these breaks have been developed, and as I'll review in terms of the clinical data, have been successfully applied and really do constitute the foundation in terms of major therapeutic inroads for this patient population. As you can see on the right-hand side of this slide, though, our understanding has become quite deep in terms of other negative regulators of immune cell function as well as positive regulators, and antibodies that block some of the negative regulators and other antibodies that activate some of the activators are currently in clinical trials, beyond the scope of today's discussion, but do constitute a very promising future wave that we hope will build on the foundation of what's been accomplished so far. I'd like to turn to the topic of metastatic melanoma, which is where most of our knowledge has been gained in terms of the application of these novel immune therapies. The first pivotal trial that really shed light on the potential impact of this new therapeutic approach of immune checkpoint antibody therapy is this MDX study. It was a randomized Phase III trial in patients who had previously treated metastatic melanoma, having failed conventional chemotherapy treatment, and patients were randomized in this trial to receive the CTLA4 blocking antibody ipilimumab alone, in combination with an investigational gp100 peptide vaccine, or peptide vaccine alone. You can see that it was a skewed randomization with the majority of patients being randomized to the combination arm per design of the study. Overall survival was the primary endpoint, and notably, the ipilimumab dose was 3 mg/kg. You can see here that the overall survival impact of ipilimumab, either given alone or in combination with peptide vaccine, was clearly demonstrated with intermediate and particularly longer-term follow-up. For patients who were followed 2 years and beyond, you can see evidence of a plateau in terms of prolonged survival being maintained following initial evidence of disease control and benefit. And this was clearly superior to the peptide vaccine alone control arm. This was the evidence that supported initial FDA approval of this 2016 ReachMD Page 2 of 8

3 treatment. This is an approach that's not without its potential toxicities, and as this slide shows, autoimmune toxicity promulgated by this type of blocking strategy for CTLA4, again a negative regulator of immune cell function normally, when you block it, you activate the immune cells, not only tumor-recognizing immune cells but even some preexisting immune cells that can recognize normal tissues. And we've learned through multiple clinical trials, and as summarized here, that the most common tissue sites involved with autoimmune toxicity are skin, intestine, liver and endocrine glands. And you can see them categorized here, and this slide presents the rate of severe toxicity, grade 3 or grade 4. This is a severity of toxicity that would typically promote the use of corticosteroids to reverse these toxicities to prevent a potentially fatal outcome that's been observed, thankfully in a very small fraction of patients, but you can see here at the bottom of this slide was observed in the context of this Phase III trial. We've also learned over time that the time course in terms of onset and resolution of these toxicities is somewhat different depending on the tissue site. As this data nicely summarizes, skin toxicity in particular emerges relatively early in the course of treatment but can also be the first to resolve. Intestinal toxicity producing diarrhea or frank colitis is most commonly observed as the next wave, and liver and endocrine toxicity, typically somewhat more delayed in onset and also in resolution. Shown here is a time course for hypophysitis, and depicted here is the notion of an ongoing problem, and much of that relates to the fact that some of the endocrine toxicities, including hypophysitis, can be irreversible in the sense that the gland, the endocrine gland, can be damaged and even destroyed in some patients requiring chronic endocrine therapy to replace the lost function. Other toxicities, though, will resolve and even resolve back to baseline with a relatively time-limited course of corticosteroid treatment, generally 4 weeks for patients who have severe toxicity. The aggregate data from all ipilimumab clinical trials is summarized here with more than 4,800 patients treated on Phase II and Phase III trials; and now with long-term follow-up data available for many of these patients, we see this characteristic overall survival curve with the so-called tail of the curve describing in this case a 20% subpopulation of patients who seem to survive not only to 2 and 3 years but beyond for patients who have up to 10 year follow-up. In fact, we know that responses and disease control can be long-lasting out to those time points as well, giving a sense that patients can pass a point of no return in terms of maintenance of remission or disease control with this type of therapy. Whether this same outcome will be observed with the next generation of immune therapies that have come following CTLA4-blocking antibodies, we'll see, but this is certainly the beacon that suggests that 2016 ReachMD Page 3 of 8

4 very long-term clinical benefit can be manifested with this approach. As I suggested previously, PD-1 is another known negative regulator of immune cell function, the biology being a little more complicated than CTLA4 in that there is 1 PD-1 receptor expressed on T-cells but 2 different ligands, PD-L1 and PD-L2, which are normally expressed on other immune cells including dendritic cells, as shown in this figure, or their expression can be co-opted by tumor cells. In other words, tumor cells can express the ligand for PD-1 and directly inhibit effector T-cell function in the tumor microenvironment. And this is the biology that is the basis for the antibodies that have been developed to block PD-L1 interactions in particular. The pivotal data that has shown how promising this approach can be is alluded to here. In the so-called KEYNOTE-002 trial, patients received pembrolizumab, one of the PD-1 blocking antibodies, at 1 of 2 doses, or could have received investigator choice chemotherapy in the control arm. If patients had a BRAF mutation, they must have received a BRAF inhibitor-based treatment approach previously, and all patients were required to have had ipilimumab. So, this is a patient population who were refractory to the therapies we know could improve survival at the time this trial was conducted, and the investigation or choice options, as shown on this slide, were the conventional chemotherapy drugs that had previously served as control arms in clinical trials in years past, even in the frontline setting. So, in this treatment refractory population, progression-free survival was the primary endpoint, and that data is shown here, clearly improved with pembrolizumab at either of the 2 mg/kg dose or the 10 mg/kg dose compared to chemotherapy; in fact, nearly identical outcome with those 2 dose groups, and it's partly on the basis of this data that the FDA approved pembrolizumab in this treatment refractory population at a dose of 2 mg/kg. You can see here that responses can be observed as well as disease control, disease control rate estimated here at the 6-month and 9-month time point, clearly superior to chemotherapy by all points of comparison. We also have a sense with longer-term follow-up that this can be long-lasting. This trial was relatively immature at the time of its initial presentation. And you can see here that the median follow-up time was, in fact, less than a year by the time of this initial report. Response rate is summarized here, complete and partial responses with the FDA-approved 2 mg/kg dose every 3 weeks, adding up to about 20% roughly in this treatment refractory population; but the vast majority of these responses were ongoing at the time of initial report. And again, these we know with additional data sets, can be quite long-lasting. Autoimmune toxicity is again a concern with this type of approach, but you see here that any grade of autoimmune toxicity or severe are lower in likelihood compared to CTLA4 antibody therapy. This is a 2016 ReachMD Page 4 of 8

5 patient population who's previously received that type of approach, and yet, you see this quite favorable toxicity profile, so the same pattern, same types of tissues that are involved with autoimmune toxicity, but overall lower rate. Nivolumab, another one of the PD-1 blocking antibodies, has also been evaluated in a definitive Phase III trial here in the treatment-naïve setting. Patients were required to be BRAF wild type because patients with a BRAF mutation would have a BRAF inhibitor approach available to them. Patients were randomized in a one-to-one fashion to receive nivolumab or dacarbazine, and this was a placebocontrolled study. Overall survival was the primary endpoint, and the conventional secondary endpoints are shown. Looking at overall survival, here with follow-up times of about 1 year, you see a stark difference in outcome with nivolumab conferring an early and intermediate benefit in terms of overall survival compared to conventional chemotherapy. This trial was definitively positive for this endpoint, ultimately supporting regulatory approval for nivolumab for metastatic melanoma. Progression-free survival, a secondary endpoint, was also markedly improved; and you'll note that in this treatment-naïve setting, the outcomes, in fact, do appear superior to the treatment refractory data previously shown for pembrolizumab, but we have treatment refractory data for nivolumab as well that would suggest incrementally better effect in terms of both disease control and overall survival experience for cohorts of patients who are treatment naïve. Objective response data is summarized here. You can see compared to chemotherapy this is certainly quite an active approach. You have a fraction of patients with complete responses, most with partial responses, and overall, about 60% of patients with some degree of tumor regression on PD-1 blocking antibody monotherapy. The durability of response is quite significant, and shown on this slide you see that patients who have had an objective response to nivolumab who are included in this figure, the vast majority of them maintain response up through the time of reporting of this data set. We know that some patients can develop resistance after initial response to therapy, but as you can see here, typically, patients maintain their response beyond the timeframe shown, 6 to 12 months for many of the patients shown. Emerging and interesting data to keep an eye on in the melanoma field is the relationship of outcome to PD-L1 expression on the tumor, and this has been scored in this clinical trial showing, in fact, that patients who had PD-L1 expression on their tumor seemed to do particularly well on PD-1 blocking antibody therapy; but it is also true the patients who were PD-L1 negative do better on this agent than conventional chemotherapy. So, when stratifying the clinical trial results by that factor, yes, you see an 2016 ReachMD Page 5 of 8

6 improvement in outcome by focusing on PD-L1 expression, but patients who are PD-L1 negative clearly conferring benefit compared to chemotherapy. Very interesting data is emerging supporting the idea that beyond just PD-L1 expression, we might be able to capture benefit from this type of approach by looking at other immunologic markers. Here are various markers, CD8 that marks T-cells in the tumor, PD-L1, as noted previously, and Granzyme B, a marker of activation of T-cells, all suggesting that we might be able to derive a bit of a signature approach to identify those patients most likely to respond to this treatment. Moving to the very interesting concept of combination therapy, CTLA4/PD-1 combination therapy has been studied now in 2 randomized trials. Shown here is the design for the so-called 067 trial, a large clinical trial, more than 900 patients randomized to receive either the combination of nivolumab with ipilimumab, nivolumab alone or ipilimumab alone. This is a treatment-naïve patient population. You can see progression-free survival was clearly improved with the combination therapy versus PD-1 monotherapy, nivolumab, or ipilimumab monotherapy. The trial was designed to show superiority compared to ipilimumab as the control and clearly a positive study by that measure. When looking at these data by PD-L1 expression on the tumor, you see here that the vast majority of the benefits seem to be conferred in the population who were PD-L1 low expressing in terms of incremental benefit of the combination over either PD-1 monotherapy or CTLA4 monotherapy, but not a basis for excluding patients from this treatment. As the FDA has just recently approved this combination, right now it is for an otherwise unselected patient population. Looking at tumor regression data, you see again the combination looks superior, certainly to CTLA4 antibody therapy as the control, but even more promising in terms of the rate of partial response on patients receiving combination compared to PD-1 monotherapy. Toxicity is an important point to keep an eye on. There are more autoimmune toxicity events with the combination, substantially more, in fact. You see here that with the combination, any grade of autoimmune toxicity is notably higher, as is the rate of grade 3/4 autoimmune toxicity. So, this may be an approach that one has to consider differently depending on the baseline characteristics of the patient, comorbidities, etc. I'd like to quickly comment on the adjuvant therapy data, which is just only emerging now for ipilimumab. We have a placebo-controlled trial that was conducted in the EORTC, 950 patients randomized to ipilimumab or placebo, relatively high-risk Stage III population in this trial. Recurrence-free survival was the primary endpoint, and the first analysis of this data suggests a benefit 2016 ReachMD Page 6 of 8

7 comparing ipilimumab to placebo with a 25% reduction in risk of relapse, as measured by hazard ratio here of This is a promising early result, but we have no overall survival data yet from this trial, and therefore, it's considered a bit premature to draw conclusions regarding the potential benefit of this approach in the adjuvant setting. Notably, 10 mg/kg was the dose administered in this trial. And when you look at the toxicity that was experienced in the study, there's a notably higher rate of grade 3/4 toxicity in this trial compared to most of the 3 mg/kg trials conducted in the metastatic setting. We do have data for 10 mg/kg in the metastatic setting to know that it also does confer a higher adverse event profile compared to 3 mg/kg, but this adjuvant data would suggest even higher risk of adverse events in this population, so still preliminary findings and not yet ready for clinical adoption in most people's view. There were treatment-related deaths on this trial, and that's an important caveat when considering the need for overall survival data in an adjuvant context such as this when we have this agent available to us in the metastatic setting. We don't yet know that it should be deployed in the adjuvant setting. So, in conclusion, ipilimumab was the first-in-class immune checkpoint antibody showing a survival advantage. Coming quickly behind that are the PD-1/PD-L1 antibodies that appear to be even better in direct head-to-head comparison. We have evidence of improved survival with this class of therapies, better progression-free survival and response rates compared to CTLA4 monotherapy. Combination CTLA4/PD-1 blockade looks like there may be at least additive efficacy, but unfortunately, evidence of toxicity that raises some concerns as well, and so I think we're going to need to see more data from this combination data set to support an impact on overall survival before we would all be able to comfortably conclude that this is a treatment option for all patients that should be offered in favor of single-agent therapy. The adjuvant role of this approach is still unproven, and we aim to produce more follow-up data from the recently completed trials, but we have ongoing trials now as well with PD-1 monotherapy, and we look forward in the years to come to see more evidence to support the potential use in that setting. With that I'd like to thank you for your attention, and I hope that this summary has given you some insight into the really revolutionary impact of this treatment approach in metastatic melanoma in particular. Thanks for your attention. ANNOUNCER CLOSE: You have been listening to Project Oncology on ReachMD. This segment, entitled Foundational Issues Related to Immunotherapy and Melanoma was provided by Prova Education ReachMD Page 7 of 8

8 To earn your CME credit, please take the post-test and activity evaluation by clicking on the post-test button below. Or if you re listening to this as a podcast, go to ReachMD.com forward slash Project Oncology ReachMD Page 8 of 8