Bispecific Anti-CD20, Anti-CD19 CAR T Cells Inspire Hope for CAR-Naïve NHL in Phase 1

Nirav N. Shah, MD

Through a first-in-human clinical trial of a bispecific anti-CD19 and anti-CD20 chimeric antigen receptor (CAR) T-cell therapy, investigators demonstrated the feasibility of this approach as treatment of adult patients with B-cell non-Hodgkin lymphoma (NHL). The study was a phase 1 dose-escalation and expansion study (NCT03019055), which aimed to explore the safety and feasibility of 4-1BB-CD 3ζ LV20.19 CAR T cells.

The doses ranged from 2.5 x 105 per kg to a dose of 2.5 x 106 per kg, which was selected as the expansion dose. Overall, the target dose was met in all CAR-naïve patients, as well as 22 patients who received treatment on protocol. For this study, the goal of cell manufacturing in a 14-day set was to infuse non-cryopreserved CAR T cells, which is not typically the case for CAR T-cell therapy.

LV20.19 CAR T-cell therapy appeared safe in this study. Grade 3/4 cytokine release syndrome (CRS) observed in 1 patient (5%), and grade 3/4 neurotoxicity was seen in 3 patients (14%).

Overall, 18 patients achieved a response at day 28 for an objective response rate (ORR) of 82%, which included 14 patients (64%) who had a complete response and 4 (18%) with a partial response. Among those who received the 2.5 x 106 per kg dose, the ORR was 100%, with 92% complete responses and 8% partial responses.

In an interview with Targeted Oncology, Nirav N. Shah, MD, associate professor, Medical College of Wisconsin, discussed the findings from the phase 1 study of a CAR T-cell therapy dual targeting CD19 and CD20 as treatment of patients with B-cell lymphomas.

TARGETED ONCOLOGY: What was the rationale that supported this study?

Shah: The rationale for the trial was that for single targeted CAR T cells, a mechanism of resistance is that tumors can downregulate CD19 to escape the CAR T-cells. The hypothesis of this trial was that dual targeting of more than one B-cell antigen can possibly overcome that as a mechanism of resistance. CD20 is the traditional target in B-cell lymphoma. We've been targeting CD20, going back to the year 2000 with a drug called rituximab [Rituxan]. It's a very natural combination, using the data we know from CD19-targeted CARs, and the efficacy we knowfrom rituximab, obinutuzumab (name), and all the other drugs that target CD20 to combine those. Our collaborators published a preclinical paper several years ago now looking at these different vector formulations and found that the 2019 combination that we then used for this clinical trial could potentially help limit that single antigen downregulation mechanism of resistance.

TARGETED ONCOLOGY: Could you elaborate more on the population of patients included in this study?

Shah: The patient population we looked at were all relapsed/refractory B-cell NHLs including CLL CLL. Patients had to be refractory to 2 or more lines of therapy, so these are patients with limited options. When we started the trial in 2017, CAR T-cell therapy was not even widely available yet like it is now. It was an opportunity for those with chemotherapy-refractory disease to be able to join a CAR T-cell trial that we hope can improve on the current standard of care.

TARGETED ONCOLOGY: How was this study designed?

Shah: This study is a phase 1 trial, and it was one of the first dual targeted anti-CD20/anti-CD19 CARs, to my knowledge, that had ever been administered to a person when we dosed our first patient back in October of 2017, about 3 years ago now. It was a safety study, and so we looked at different doses. We started at a low dose of 2.5 x 105 per kg, and then escalated to our target dose of 2.5 x 106 cells per kg,. Fortunately, we didn't see much toxicity. Our rates of CRS and neurotoxicity were quite low. After our first 6 patients, we were able to get right to the target dose level. When we got to the target dose level, we saw that we had a high response rate.

The other thing that was unique about our trial in our methodology we used for manufacturing in house. Our program invested in a new technology called the CliniMACS Prodigy device. This device allows for point of care manufacturing, and by doing point of care manufacturing, we're able to collect the cells fresh, put them right of the device, and administer them fresh without having to perform a mandated cryopreservation step of freezing them down and thawing them.

We had several interesting findings in this report, and again, we had multiple histologies, including diffuse large B-cell, mantle cell, follicular, but when we got to that 2 and a half million dose, and if we were able to give the patients a fresh infusion, which was 12 of those patients, the ORR was 100%. The progression-free survival was very promising as well in that cohort, with more than half the patients remaining in remission at the time that we published the paper. Again, that's a subset analysis of the whole patient population, but these data were encouraging enough that with our partners at Miltenyi, this will be going to a phase 2 clinical trial to try and show whether or not it is efficacious at the level that we saw on our initial trial.

The other interesting thing that we found is that when we looked at patients who relapsed, we biopsied all of them, and we didn't find that anyone who lost CD19 expression. This is hypothesis-proving again, with a limited number of patients. I'll throw in the caveat that for the patients who fail this therapy, it may not be due to loss of CD19, but other mechanisms, perhaps loss of persistence or other immunomodulatory ways that the tumor can evade CAR T-cell therapy, and so we thought these were interesting findings that came out of our trial.

TARGETED ONCOLOGY: What are the implications of these findings?

Shah: Single targeted CAR T-cells are one of the most exciting things to happen in the hematologic malignancy space. However, for patients with B-cell NHL, specifically DLBCL, most patients will either fail to respond or relapse after treatment. We know that the long-term progression free survival is about 30% to 40% and so the question is, how can we improve upon that number? What we saw in our phase 1 clinical trial is that at the target dose level, we had a very high ORR. Many of those responses are durable, and perhaps through dual targeting, we can mitigate loss of CD19 as a mechanism of resistance. Will this CAR be the cure all be all for all types of cancer? Probably not, because cancer is very smart, and it can find a way to escape. However, we are optimistic that perhaps this next-generation in CAR T-cell therapy is potentially an advancement on the currently available single targeted CARs by targeting both CD19 and CD20, well-known well-defined antigens on patients with B-cell NHL.

TARGETED ONCOLOGY: What are the next steps for this research now?

Shah: The first study was an investigator-initiated trial at our center, so this phase 2 will be an industry-sponsored trial because they have the breadth to run multicenter trials. This is going to be a multicenter trial within the United States, specifically looking at this drug at the 2 and a half by 10 to the 6 cells per kilogram dose in a patient population with aggressive B-cell NHL.

TARGETED ONCOLOGY: How do you see this treatment landscape evolving over the next couple years?

Shah: At the end of the day, the planned phase 2 trial will determine that the efficacy of the treatment so ultimately we need the data. The phase 2 trial will be an opportunity to figure out whether or not our data are reproducible in a larger patient population and across institutions. This was an initial project that we did it within our own institution, so I think once that data is out there, we'll get a better sense of the response rates. Will we have more patients achieve a long-term remission? If we do, then perhaps we've moved the needle, and this could be hopefully another therapy available to our patients.

TARGETED ONCOLOGY: What challenges still remain in this space that we need to address?

Shah: The biggest challenge is that the majority of patients on our trial are CAR-naive. We did mention a little bit about a subset of patients that we tried to treat who had previously received a CD19 CAR, and in that patient population, our response rate was lower at about 20% to 30%. It goes to show the challenges of treating people who have relapsed after CAR T, and I think that's an unmet need in the field. It's an area that requires further investigation. We saw some efficacy, but again, not as good as the patients who were CAR-naive, meaning receiving CAR T-cell therapy for the first time. That's probably a huge area of investigation that needs to be looked at, and I know that we are among other groups, specifically trying to better understand what the right approach is to treat people who have failed prior CAR T-cell therapy.

TARGETED ONCOLOGY: What are your key takeaways from this?

Shah: The key takeaways are that our trial showed that a bispecific CAR targeting CD20 and CD19 is safe. That was the main goal of the phase 1 study, and you can see that within our report. We had low rates of CRS and neurotoxicity. Nobody died as a result of the this bispecific CAR T-cell therapy which is important. Second, we saw an exciting and promising efficacy signal, specifically for a fresh or non-cryopreserved infusion at the goal dose of 2.5x10^6 cells/kg. Third, when the treatment didn't work or didn't fail, we didn't find that it was due to a loss of CD19, suggesting that dual targeting can be a way to overcome that mechanism of resistance. Again, we need more patients, and we need a larger trial. We are planning on doing those things in the imminent future.

_Reference

_{Shah NN, Johnson BD, Schneider D, et al. Bispecific anti-CD20, anti-CD19 CAR T cells for relapsed b cell malignancies: a phase 1 dose escalation and expansion trial. Nat Med. 2020:26, 1569-1575. doi: 10.1038/s41591-020-1081-3}