Researchers show CTL019 cells proliferate and persist

SAN FRANCISCO—Two goals for cell therapy with chimeric antigen receptor (CAR) T cells are significant levels of in vivo proliferation and persistence after the cells are infused.

Researchers at the University of Pennsylvania, working with CTL019 cells, are beginning to see both of these phenomena in children with relapsed, refractory acute lymphoblastic leukemia (ALL).

Stephan Grupp, MD, PhD, described these results at the 2014 ASH Annual Meeting (abstract 380).*

CTL019 is a second-generation chimeric protein engineered using a single-chain variable fragment of an antibody that targets CD19 on B cells. It is combined with the intracellular signaling domains 4-1BB and CD3 zeta and expanded ex vivo with anti-CD3/anti-CD28.

“We take T cells from the patient—this is an individualized or personalized product,” Dr Grupp explained. “We transfect the T cells with a virus, and, in our case, we are using a lentiviral vector. This permanently modifies the T cells.”

“And this allows the expression of the CAR protein in the T cells, which then drives the interaction between the T cell and the cancer cell, hopefully killing the cancer cell but also, and I think this is extraordinarily important, allowing for T-cell activation and significant proliferation.”

More than 130 patients have been treated with CTL019, including patients with CLL whose results were reported at the 2014 ASCO Annual Meeting.

Updated results

At ASH, Dr Grupp provided an update on the 39 children with relapsed, refractory ALL treated with CTL019.  He and his colleagues previously reported results in children and adults with ALL in NEJM.

Thirty-six patients (92%) achieved complete remission within a month after infusion. Ten patients relapsed, of whom 5 were CD19⁺ and 5 were CD19^-.

Dr Grupp explained that CD19⁺ relapses represent waning T cells, and CD19^- relapses represent true antigen escape. The latter patients still have CTL019 cells.

Patients were followed for a median of 6 months, ranging from 6 weeks to 31 months. And 15 patients have been followed for more than 1 year.

The patient followed for 31 months “represents the first patient treated who remains in remission with no further therapy,” Dr Grupp said.

Three patients went on to have a stem cell transplant, and 2 had other treatments. One patient had a donor-lymphocyte infusion, and 1 patient who developed myelodysplastic syndrome received treatment for that condition.

“And I think this is a key point,” Dr Grupp noted. “[I]t was a possibility to consider not continuing with a second, third, or, in one case, a fourth transplant.”

Another important point is disease burden, he said. Patients with more than 50% bone marrow blasts at the time of their T-cell infusion had a similar response rate (82%) to those patients who had a lower disease burden of 5% blasts or more (88%). Relapse occurred in all levels of disease burden in a small number of patients.

To date, there has been no graft-vs-host disease.

In terms of efficacy, there appeared to be no significant difference if the patient had received a transplant before CAR therapy or not. Eighty-nine percent of patients who had received an allogeneic transplant responded, compared to 100% who had not had a transplant.

Persistence and proliferation

“Q-PCR detection of CAR cells shows enormous proliferation,” Dr Grupp said. “We have an extraordinary amount of expansion of these cells that’s nearly universal.”

Specifically, the researchers saw 100,000- to 110,000-fold expansions of CAR-positive cells.

Two-thirds of patients have circulating CAR cells 6 months out from their CTL019 infusion. And a group of patients have kept their CAR cells for longer than 12 months. In the group that loses their cells more quickly, CD19⁺ recurrence is overrepresented, Dr Grupp noted.

Event-free survival is 70% at 6 months, and 76% of patients had a 6-month duration of response.

Toxicity

Cytokine release syndrome (CRS) is a “significant toxicity,” Dr Grupp said, but investigators are beginning to understand some correlates that impact treatment.

Patients with extraordinary levels of the cytokine interleukin-6 (IL-6)—those who require blood pressure or respiratory support—have significantly more severe CRS than those with lower IL-6 levels (P<0.001). Responding patients have high IL-6 levels as well, but patients with severe CRS have very high levels.

The effector cytokine IFNγ, which may be required for the T-cell response, is also elevated in patients with severe CRS compared to those without CRS (P<0.001).

“The thing that I think we’ve really learned from these patients is the impact of disease burden,” Dr Grupp said.

Patients with high disease burden—those with more than 50% bone marrow blasts—have a high likelihood of developing severe CRS. Patients with less burden—fewer than 50% blasts—have a low likelihood.

Dr Grupp pointed out that only 2 patients with more than 50% blasts did not have severe CRS, and they did not respond to therapy.

“This is highly significant and quite predictive for our patients,” he said, adding that CRS is quite controllable via IL-6 blockade with tocilizumab.

B-cell aplasia is “inevitable” as long as these patients have their CAR T cells, Dr Grupp noted. Patients require IVIg replacement therapy for the entire period.

Macrophage activation syndrome, the flip side of CRS, is also a concern, and neurotoxicity, consisting of confusion and aphasia, occurred in a small number of patients and required no therapy.

Given these results, the investigators believe that CTL019 cells may be able to provide long-term response without subsequent therapy.

CTL019 recently received breakthrough therapy designation from the US Food and Drug Administration.

CTL019 was invented at The University of Pennsylvania but has been licensed to Novartis. Several researchers involved in this study reported research funding and/or consultancy payments from Novartis, and 2 researchers are employed by the company.

*Data in the presentation differ from the abstract.

SAN FRANCISCO—Two goals for cell therapy with chimeric antigen receptor (CAR) T cells are significant levels of in vivo proliferation and persistence after the cells are infused.

Researchers at the University of Pennsylvania, working with CTL019 cells, are beginning to see both of these phenomena in children with relapsed, refractory acute lymphoblastic leukemia (ALL).

Stephan Grupp, MD, PhD, described these results at the 2014 ASH Annual Meeting (abstract 380).*

CTL019 is a second-generation chimeric protein engineered using a single-chain variable fragment of an antibody that targets CD19 on B cells. It is combined with the intracellular signaling domains 4-1BB and CD3 zeta and expanded ex vivo with anti-CD3/anti-CD28.

“We take T cells from the patient—this is an individualized or personalized product,” Dr Grupp explained. “We transfect the T cells with a virus, and, in our case, we are using a lentiviral vector. This permanently modifies the T cells.”

“And this allows the expression of the CAR protein in the T cells, which then drives the interaction between the T cell and the cancer cell, hopefully killing the cancer cell but also, and I think this is extraordinarily important, allowing for T-cell activation and significant proliferation.”

More than 130 patients have been treated with CTL019, including patients with CLL whose results were reported at the 2014 ASCO Annual Meeting.

Updated results

At ASH, Dr Grupp provided an update on the 39 children with relapsed, refractory ALL treated with CTL019.  He and his colleagues previously reported results in children and adults with ALL in NEJM.

Thirty-six patients (92%) achieved complete remission within a month after infusion. Ten patients relapsed, of whom 5 were CD19⁺ and 5 were CD19^-.

Dr Grupp explained that CD19⁺ relapses represent waning T cells, and CD19^- relapses represent true antigen escape. The latter patients still have CTL019 cells.

Patients were followed for a median of 6 months, ranging from 6 weeks to 31 months. And 15 patients have been followed for more than 1 year.

The patient followed for 31 months “represents the first patient treated who remains in remission with no further therapy,” Dr Grupp said.

Three patients went on to have a stem cell transplant, and 2 had other treatments. One patient had a donor-lymphocyte infusion, and 1 patient who developed myelodysplastic syndrome received treatment for that condition.

“And I think this is a key point,” Dr Grupp noted. “[I]t was a possibility to consider not continuing with a second, third, or, in one case, a fourth transplant.”

Another important point is disease burden, he said. Patients with more than 50% bone marrow blasts at the time of their T-cell infusion had a similar response rate (82%) to those patients who had a lower disease burden of 5% blasts or more (88%). Relapse occurred in all levels of disease burden in a small number of patients.

To date, there has been no graft-vs-host disease.

In terms of efficacy, there appeared to be no significant difference if the patient had received a transplant before CAR therapy or not. Eighty-nine percent of patients who had received an allogeneic transplant responded, compared to 100% who had not had a transplant.

Persistence and proliferation

“Q-PCR detection of CAR cells shows enormous proliferation,” Dr Grupp said. “We have an extraordinary amount of expansion of these cells that’s nearly universal.”

Specifically, the researchers saw 100,000- to 110,000-fold expansions of CAR-positive cells.

Two-thirds of patients have circulating CAR cells 6 months out from their CTL019 infusion. And a group of patients have kept their CAR cells for longer than 12 months. In the group that loses their cells more quickly, CD19⁺ recurrence is overrepresented, Dr Grupp noted.

Event-free survival is 70% at 6 months, and 76% of patients had a 6-month duration of response.

Toxicity

Cytokine release syndrome (CRS) is a “significant toxicity,” Dr Grupp said, but investigators are beginning to understand some correlates that impact treatment.

Patients with extraordinary levels of the cytokine interleukin-6 (IL-6)—those who require blood pressure or respiratory support—have significantly more severe CRS than those with lower IL-6 levels (P<0.001). Responding patients have high IL-6 levels as well, but patients with severe CRS have very high levels.

The effector cytokine IFNγ, which may be required for the T-cell response, is also elevated in patients with severe CRS compared to those without CRS (P<0.001).

“The thing that I think we’ve really learned from these patients is the impact of disease burden,” Dr Grupp said.

Patients with high disease burden—those with more than 50% bone marrow blasts—have a high likelihood of developing severe CRS. Patients with less burden—fewer than 50% blasts—have a low likelihood.

Dr Grupp pointed out that only 2 patients with more than 50% blasts did not have severe CRS, and they did not respond to therapy.

“This is highly significant and quite predictive for our patients,” he said, adding that CRS is quite controllable via IL-6 blockade with tocilizumab.

B-cell aplasia is “inevitable” as long as these patients have their CAR T cells, Dr Grupp noted. Patients require IVIg replacement therapy for the entire period.

Macrophage activation syndrome, the flip side of CRS, is also a concern, and neurotoxicity, consisting of confusion and aphasia, occurred in a small number of patients and required no therapy.

Given these results, the investigators believe that CTL019 cells may be able to provide long-term response without subsequent therapy.

CTL019 recently received breakthrough therapy designation from the US Food and Drug Administration.

CTL019 was invented at The University of Pennsylvania but has been licensed to Novartis. Several researchers involved in this study reported research funding and/or consultancy payments from Novartis, and 2 researchers are employed by the company.

*Data in the presentation differ from the abstract.

SAN FRANCISCO—Two goals for cell therapy with chimeric antigen receptor (CAR) T cells are significant levels of in vivo proliferation and persistence after the cells are infused.

Researchers at the University of Pennsylvania, working with CTL019 cells, are beginning to see both of these phenomena in children with relapsed, refractory acute lymphoblastic leukemia (ALL).

Stephan Grupp, MD, PhD, described these results at the 2014 ASH Annual Meeting (abstract 380).*

CTL019 is a second-generation chimeric protein engineered using a single-chain variable fragment of an antibody that targets CD19 on B cells. It is combined with the intracellular signaling domains 4-1BB and CD3 zeta and expanded ex vivo with anti-CD3/anti-CD28.

“We take T cells from the patient—this is an individualized or personalized product,” Dr Grupp explained. “We transfect the T cells with a virus, and, in our case, we are using a lentiviral vector. This permanently modifies the T cells.”

“And this allows the expression of the CAR protein in the T cells, which then drives the interaction between the T cell and the cancer cell, hopefully killing the cancer cell but also, and I think this is extraordinarily important, allowing for T-cell activation and significant proliferation.”

More than 130 patients have been treated with CTL019, including patients with CLL whose results were reported at the 2014 ASCO Annual Meeting.

Updated results

At ASH, Dr Grupp provided an update on the 39 children with relapsed, refractory ALL treated with CTL019.  He and his colleagues previously reported results in children and adults with ALL in NEJM.

Thirty-six patients (92%) achieved complete remission within a month after infusion. Ten patients relapsed, of whom 5 were CD19⁺ and 5 were CD19^-.

Dr Grupp explained that CD19⁺ relapses represent waning T cells, and CD19^- relapses represent true antigen escape. The latter patients still have CTL019 cells.

Patients were followed for a median of 6 months, ranging from 6 weeks to 31 months. And 15 patients have been followed for more than 1 year.

The patient followed for 31 months “represents the first patient treated who remains in remission with no further therapy,” Dr Grupp said.

Three patients went on to have a stem cell transplant, and 2 had other treatments. One patient had a donor-lymphocyte infusion, and 1 patient who developed myelodysplastic syndrome received treatment for that condition.

“And I think this is a key point,” Dr Grupp noted. “[I]t was a possibility to consider not continuing with a second, third, or, in one case, a fourth transplant.”

Another important point is disease burden, he said. Patients with more than 50% bone marrow blasts at the time of their T-cell infusion had a similar response rate (82%) to those patients who had a lower disease burden of 5% blasts or more (88%). Relapse occurred in all levels of disease burden in a small number of patients.

To date, there has been no graft-vs-host disease.

In terms of efficacy, there appeared to be no significant difference if the patient had received a transplant before CAR therapy or not. Eighty-nine percent of patients who had received an allogeneic transplant responded, compared to 100% who had not had a transplant.

Persistence and proliferation

“Q-PCR detection of CAR cells shows enormous proliferation,” Dr Grupp said. “We have an extraordinary amount of expansion of these cells that’s nearly universal.”

Specifically, the researchers saw 100,000- to 110,000-fold expansions of CAR-positive cells.

Two-thirds of patients have circulating CAR cells 6 months out from their CTL019 infusion. And a group of patients have kept their CAR cells for longer than 12 months. In the group that loses their cells more quickly, CD19⁺ recurrence is overrepresented, Dr Grupp noted.

Event-free survival is 70% at 6 months, and 76% of patients had a 6-month duration of response.

Toxicity

Cytokine release syndrome (CRS) is a “significant toxicity,” Dr Grupp said, but investigators are beginning to understand some correlates that impact treatment.

Patients with extraordinary levels of the cytokine interleukin-6 (IL-6)—those who require blood pressure or respiratory support—have significantly more severe CRS than those with lower IL-6 levels (P<0.001). Responding patients have high IL-6 levels as well, but patients with severe CRS have very high levels.

The effector cytokine IFNγ, which may be required for the T-cell response, is also elevated in patients with severe CRS compared to those without CRS (P<0.001).

“The thing that I think we’ve really learned from these patients is the impact of disease burden,” Dr Grupp said.

Patients with high disease burden—those with more than 50% bone marrow blasts—have a high likelihood of developing severe CRS. Patients with less burden—fewer than 50% blasts—have a low likelihood.

Dr Grupp pointed out that only 2 patients with more than 50% blasts did not have severe CRS, and they did not respond to therapy.

“This is highly significant and quite predictive for our patients,” he said, adding that CRS is quite controllable via IL-6 blockade with tocilizumab.

B-cell aplasia is “inevitable” as long as these patients have their CAR T cells, Dr Grupp noted. Patients require IVIg replacement therapy for the entire period.

Macrophage activation syndrome, the flip side of CRS, is also a concern, and neurotoxicity, consisting of confusion and aphasia, occurred in a small number of patients and required no therapy.

Given these results, the investigators believe that CTL019 cells may be able to provide long-term response without subsequent therapy.

CTL019 recently received breakthrough therapy designation from the US Food and Drug Administration.

CTL019 was invented at The University of Pennsylvania but has been licensed to Novartis. Several researchers involved in this study reported research funding and/or consultancy payments from Novartis, and 2 researchers are employed by the company.

*Data in the presentation differ from the abstract.