CHICAGO—Chimeric antigen receptor (CAR) T cells combined with ibrutinib enhance T-cell function and can induce complete remission (CR) in patients with chronic lymphocytic leukemia (CLL), researchers report.
Many CLL patients receive ibrutinib treatment, which is well tolerated, but few patients achieve CR.
Immunotherapy with anti-CD19 CAR T cells has induced CR in 25% – 45% of patients with CLL, Saar Gill, MD, of the University of Pennsylvania in Philadelphia, told Hematology Times, and these CRs tend to be durable.
So investigators conducted a pilot trial in 10 patients to test whether combining anti-CD19 CAR T cells with ibrutinib would enhance the CR rate.
Dr Gill reported the findings of the pilot trial at the ASCO 2017 Annual Meeting (abstract 7509).
The patients must have failed at least 1 regimen before ibrutinib, unless they had del(17)(p13.1) or a TP53 mutation.
T cells were lentivirally transduced to express a CAR that included humanized anti-CD19.
Patients were lymphodepleted 1 week before infusion, and ibrutinib was continued throughout the trial.
After a median follow-up of 6 months, 8 of the 9 evaluable patients show absence of CLL in the bone marrow by flow cytometry or minimal residual disease (MRD) negative, and all remain in marrow CR at last follow-up, Dr Gill said.
Radiologic responses are less clear-cut and may require longer follow-up.
“All but 1 patient achieved MRD with deep sequencing. We have deep response in the bone marrow,” Dr Gill said. He also noted that the treatment was well tolerated.
Cytokine release syndrome (CRS) developed in 9 patients: grade 1 in 2 patients, grade 2 in 6 patients, and grade 3 in 1 patient. One patient developed grade 4 tumor lysis syndrome. Treatment of CRS with the IL-6 receptor antagonist tocilizumab was not required.
There was modest residual splenomegaly in 3 of 5 patients, and adenopathy resolved in 4 of 6 patients, with progression in 1 patient.
Ibrutinib reduced CRS apparently by blocking cytokine production by T cells, said Dr Gill, adding, “The combination led to improved efficacy without increased toxicity.”
Ibrutinib may make CAR T-cell therapy more feasible.
Patients who receive ibrutinib for 6 months have a better T-cell response.
“This opens up future discussions of bringing CAR T-cell therapy earlier into CLL treatment,” said Dr Gill.
He envisions patients receiving ibrutinib for 6 months, which would allow time to manufacture T cells, and then have a T-cell infusion.
“Once patients achieve MRD, then we can discuss the possibility of stopping ibrutinib therapy,” he said.
“Most patients remain on ibrutinib, but longer follow-up may show whether remissions are sustained off ibrutinib.”
The researchers have ongoing plans to treat 25 patients with CTL19 plus ibrutinib in a continuation of this trial.
Dr Gill said longer follow-up will reveal the durability of these results “and could support evaluation of a first-line combination approach in an attempt to obviate the need for chronic therapy.”