Dr Li:  CD19 CAR-T treatment has been applied in the refractory and relapsed DLBCL recently， durable complete remission can only be seen in 29% to 37% of patients. Could you highlight the benefits and challenges for this kind of treatment and explain the potential causes for relapse? 

 

Dr Osborne: the potential causes for relapse I think there are definitely two that have been considered. One is antigen escape and the other is CAR-T cell exhaustion.  So the ALEXANDER study is using a bicistronic CAR-T targeting both CD19 and CD22， and thereby using two target antigens. it is designed with the hope of reducing relapse via antigen escape. CAR-T exhaustion is possibly due to up regulation of PD-1 on the CAR-T cells. And there are in vitro data to show this. Therefore， the ALEXANDER study uses pembrolizumab in the conditioning regimen to try and reduce CAR-T cell exhaustion. Initially， it was introduced on day plus 14 for safety reasons， when most of the CAR-T expansion had occurredand then， when the safety data were good， the pembrolizumab was moved to day minus one， so that there is still the benefit of introducing it， but earlier in the conditioning regimen.

 

Dr Li: Your team reported the first incorporation of dual targeting CAR-T and anti PD-1 in DLBCL. Could you please introduce why AUTO3 is so uniDr Liue Compare with other CAR-Ts? Could you explain the mechanism of adding pembrolizumab and dose of this drug? 

 

Dr Osborne: AUTO3  is different to other CD19 CAR-Ts. It’s a bicistronic CAR-T. So it uses one vector to introduce two individual CARs which are specifically designed to target their own CD antigens.  most CARs， the 19 CARs use FMC as their binder. Whereas AUTO3 uses humanized HD37. It also uses OX40 and 41-BB co-stimulator domains which are designed to improved persistence. So the CAR design is uniDr Liue in the fact is bicistronic and also it’s humanized HD37.  The introduction of pembrolizumab was designed to try and reduce CAR-T cell exhaustion. And obviously， initially， there has to be safety assessment of this， and that’s why in the first design of the trial it was introduced at day 14， when maximal CAR-T expansion had occurred. The toxicity of AUTO3 which has been presented is very low with no significant CRS and minimal neurotoxic toxicity. Therefore， pembrolizumab was then introduced to d(-1)， the responses  have been seen early in the trial protocol .， therefore， it is reasonable to introduce early into the conditioning regimen， because it has  durable effect which allows the efficacy of the construct in combination with PD-1 inhibition. 

 

Dr Li:  Could you share us the ALEXANDER study clinical design and main results of this study. which is recommended dose?

 

Dr Osborne:  the ALEXANDER study is a phase I/II study starting with the 50 million dose， and then dose escalating through doses of 150 million cells with 450 million cells as the maximum dose， and this is now completed. Flu/Cy conditioning is standard， and pembrolizumab was initially introduced for three doses from day 14， and then moved to day minus one. The safety data was the primary endpoint for the phase I part of the studying looking at toxicity in the first 75 days， most of the serious adverse events were haematological and reversible， and of interest，there was no severe cytokine release syndrome(CRS)， and most CRS was grade one， only 17% of patients reDr Liuires tocilizumab. There was only one neurotoxicity event out of the 23 patients， this was Dr Liuite atypical，the patient had some facial and muscle weakness， and of interest， the patient had similar episode 10 years previously without a diagnosis reached， so this may be related to this. There was no neurotoxicity at the 150 million above dose or with pembrolizumab， therefore， because it is felt to be safe moving forward. The dose range of the recommended phase two dose range is 150 million to 450 million cells with day minus one pembrolizumab and the efficacy has been really encouraging. So there were complete response is seen with all doses and delivered it， for the 23 patients， the complete response rate was 48%. When get looking at the patients who received more than 150 million cells， the complete response rate was 56% and this was where the dose range was decided moving forward. For patients who received more than 150 million cells and day minus one  pembrolizumab，the complete response rate was 63%， so although earlier data with the first 23 patients treated， this is safe. and the efficacy is very encouraging， especially when we look at the sustained responses that are achieved in comparison to other CAR-Ts were 25% of patients relapse. 

 

Dr Li:  I’m interesting in this clinical  trial， because this bicistronic CAR-T choose retroviral vector including both anti-CD19 and anti-CD22 CAR-T，it’s intersesting design. what’s the difference between this CAR-T and seDr Liuentially use anti-CD19 CAR-T and anti-CD22 CAR-T，What’s the difference between the design?

 

Dr Osborne:   This is a  bicistronic CAR in comparison to other tandem CARs which don’t have the independent antigen targets. So， these are two independent CARs delivered with the single vector on one CAR rather than a tandem CAR which other centers using. 

 

Dr Li:   I wonder why you use retroviral vector? How about other vectors in CAR-T clinical trials? 

 

Dr Osborne:  The retroviral vector has been successful in manufacture of all these the CARs. All of the patients had sufficient products made as reDr Liuired for the trial， and because it has been successful and sustainable. This is why we have used a retroviral vector. 

 

Dr Li:  How about the CRS and other side-effects on the patients who received AUTO3 compare with other CAR-T treatment?  How do you balance clinical benefits with risks?

 

Dr Osborne:  So， I think this is an extremely positive aspect of AUTO3 is its safety. We see significant CRS and neurotoxicity with the currently available CD19 CARs， almost 1/3 of patients have these toxicity and significant numbers need to go to intensive care because of CRS and neurotoxicity. Auto3， in my experience， has been incredibly safe to deliver with no severe CRS and only this one event which is Dr Liuite atypical of neurotoxicity， and again no neurotoxicity has seen with the moving forward recommended phase II dose. So， I think that as well as the early efficacy data being incredibly encouraging， i think the safety data is also encouraging， and because of the safety data， it’s allowing us to move to an outpatient-based expansion cohort which will be opening soon for recruitment. 

 

Dr Li:   As we all know， for the CAR-T clinical trials ，severe CRS and neurotoxicity are the main toxicity of CAR-T. But in your study， AUTO3 didn’t have the severe CRS and neurotoxicity， can you explain to us why so less toxicity in this  clinical trial ? 

 

Dr Osborne:     So， it’s possible that the low levels of toxicity are because of the low cytokine levels that AUTO3 seems to stimulate. There are Dr Liuite clear in vivo and in vitro data that AUTO3 has lower levels in association with CRS compared to other CD19 CARs and because of the lower cytokine  released， I think that could explain the low toxicity. But yet there is adeDr Liuate cytokines released to cause efficacy in terms of patient response. 

 

Dr Li:  I’m also interested in the design of this clinical trial， you use CAR-T first， and then use PD-1 antibody. So， do you think the PD-1 antibody treatment is very important in this clinical trial? 

 

Dr Osborne:   I think so. The mechanism behind CAR-T exhaustion is obviously recognized possibly due to PD-Ll expression and also up regulation of PD-1 on the CARs， so trying to inhibit that. But in a safe way with PD-1 blockade appears to be the cause for the excellent efficacy data that we are seeing so far. 

 

Dr Li: I also  interested in  the doses of pembrolizumab， you have used the three doses of pembrolizumab with regimen A， but regimen B you only use one dose of pembrolizumab.  How about your opinion about these doses of pembrolizumab? if patients need one year of pembrolizumab treatment， choose only one or three doses of pembrolizumab?

 

Dr Osborne:  In terms of the half-life of pembrolizumab and the timing of the response and maximal CAR-T expansion which is within the first 28 days， it appears reasonable to give just one dose on day minus one of the conditioning， and therefore moving forward， especially in view of the low toxicity and excellent response rates. This is why we are moving forward with the day minus one and one does only of pembrolizumab in the dose expansion phase. 

 

Dr Li:    I also wonder how about the order of stem cell transplantation with CAR-T， some authors used the CAR-T before the stem cell transplantation. some doctors suggest stem cell transplantation before CAR-T treatment. how about your opinion?  In ALEXANDER study， do patients can receive autologous stem cell transplantation in the clincial trial?

 

Dr Osborne:    Previously， Autologous Stem Cell Transplantation(ASCT) was not any exclusion criteria for this trial， this trial isn’t a treatment which is planned as a bridge to further transplantation whether that be Auto or Allo， because of the durable and sustained complete responses. we would be planning that this treatment alone was adeDr Liuate for the patient. 

 

Dr Li:    Nowadays， CAR-T treatment is very interesting and very promising in the treatment of relapsed and refractory different B cell lymphoma(r/r-DLBCL). and in ALEXANDER study of AUTO3 suggest use two kinds of CAR-Ts(CD19 and CD22 dual targeting CAR-T) and show effective in treatment. I don’t know if you can use three or four kinds of CAR-T together and not only just two?

 

Dr Osborne:   At the moment， I don’t have any experience of giving sort of more than two dual antigen targeting. And i think that managing to get using just one vector， both CARs available is already successful and has got good results. So， I think that we know that some of the patients do relapse because of CD 19 escape， but that isn’t the cause for all relapsed diffuse large B cell lymphoma. So，by using a bicistronic CAR that may try and affect one of the resistance mechanisms， but also using it in combination with checkpoint inhibitors and other approaches. 

 

Dr Li:   I have another Dr Liuestion about the new CAR-T treatment， someone also use CD19 combined with a anti PD-1 CAR-T， how about your opinion about PD-1 CAR-T treatment?  Or you prefer to use anti PD-1 antibody? 

 

Dr Osborne:    In the ALEXANDER study， we using an anti PD-1 antibody pembrolizumab，and it because that can block both of PD-L1 and PD-L2. Whereas if just using a PD-1 CAR-T that doesn’t affect the PD-L2. So in my opinion， it appears to be using an anti PD-1 antibody may have better efficacy in terms of trying to reduce CAR-T cell exhaustion.

 

Dr Li: Nowadays， in the lymphoma treatment， there are some dual antibody such as anti CD20 antibody combine with anti CD3 antibody， how about you opinion about this  dual antibody treatment? 

 

Dr Osborne:   Looking at bi-specific antibody treatments， i think it’s also very encouraging， and i think that there are some benefits with this in terms of theirs. they can be off -the-shelf treatment， so to speak， rather than having to allow the manufacturing time when the patient can progress. I think both of these directed therapy both CAR-T cell and bi-specific antibodies， look really encouraging for the future， and what would be helpful is if we’re able to select the patients who could benefit from each approach was minimizing toxicity. 

 

Dr Li:   CAR-T cell therapy was approved in relapsed and refractory diffuse large B cell lymphoma. But as we all know， for the relapsed and refractory mantle cell lymphoma， CAR-T treatment is aslo very effective in study which published in the New England Journal Medicine last April. for the follicular lymphoma， CAR-T is also very effective. Do you think maybe CAR-T treatment maybe will be the standard treatment of many kinds of refractory and relapsed subtypes of the lymphoma， not only DLBCL?

 

Dr Osborne:  I think that’s difficult in the UK at the moment， we are only allowed to use the two licensed products for relapsed and refractory diffuse large B cell lymphoma of the two prior lines of therapy. As yet we can not use for low grade or mantle cell  lymphoma， i think that it obviously has implications on health， economics， cost of these expensive therapies and whether they can be delivered for how many patients. And I am hopeful that they will be an option for many of our patients who have relapse and subtypes of lymphoma. Whether its a cellular therapy approach or bi-specific antibody approach， i think we need more data and longer follow-up for us to really know that answer. 

 

Dr Li:    For the CAR-T treatment. there is a problem about the duration of response， maybe some patient will relapse after CAR-T treatment. and how about your opinion? how to prolong the duration of response of CAR-T treatment in lymphoma?

 

Dr Osborne:  Durability of responses is really what we’re trying to improve upon now with the current CAR-T and the current CAR-T designs， it appears to be possibly related to the co-stimulator domain that is chosen. it may be because of CAR-T exhaustion. other concerns are heavily pretreated patients. you may be able to make less efficacious CARs for them because they’ve had so much heavy pretreatment with many lines of therapy. So， i think that as we further gain experience with using and the different CARs available and make sure that we collect the data in the real world setting， then we would be able to select out the patients who are benefiting most and trying recognize when we should introduce CAR-T cell therapy at which stage of our patients management. 

 

Dr Li:     How about your opinion about the CAR-T treatment in the first-line treatment of lymphoma? 

 

Dr Osborne:   For first-line treatment for CAR-T， I think that we would have to make sure that if safety data will better than we have at the moment for the currently approved CAR-T because we do send a significant number of patients to ITU with CRS and neurotoxicity. 60%~70% of patients have a durable remission with standard R-CHOP treated chemotherapy，and i  think that i really can’t see it personally as first-line treatment unless we are better able to select out those patients in the future who aren’t going to respond to R-CHOP in frontline treatment.

 

 

 

Dr Li: The last Dr Liuestion， how about your opinion about the PD-1 antibody in the Hodgkin Lymphoma(HL)? For relapsed and refractory HL，anti PD-1 therapy is the standard treatment， it’s very effective because of  high expression of PD-L1 and PD-L2 in  relapsed and refractory HL. But PD-L1 and PD-L2 maybe less expressed in untreated HL compared with relapsed and refractory HL， therefore， i don’t know if anti PD-1 treament is more effective in relapsed and refractory HL than untreated HL? How about you opinion? 

 

Dr Osborne: I think where we fit PD-1 treatment in hodgkin lymphoma is difficult， because we get excellent response with our standard frontline treatments for many of our Hodgkin lymphoma patients. if we could pick out those patients up front who weren’t going to respond to ABVD or escalated BEACOPP， then we might want to introduce a checkpoint inhibitor early on. However， at the moment， i’m not sure we would want to expose all of our patients up front checkpoint inhibitors and because it’s not necessary for all of them. and if there are no specifically or prognostic factors for these patients， we may want to save it for later on relapse. The other issue is when we use checkpoint inhibitors， we often don’t see a complete metabolic remission in hodgkin lymphoma， and obviously that’s something that we’re all trying to obtain prior to using autologous stem cell transplant consolidation for our patients with hodgkin lymphoma. So， I think that at the moment， we’re not sure the seDr Liuencing of a lot of our treatments are available， when we should use brentuximab vedotin? when we should use checkpoint inhibitors? at the present in the UK， they’re funded at certain lines of treatment. we are currently undergoing clinical trials Looking at the outcomes of the patients using it either frontline or earlier on in relapse.