ORLANDO – Chimeric antigen receptor (CAR) T cells targeting BCMA eradicated myeloma cells in a patient with a heavy burden of chemotherapy-resistant multiple myeloma.
The patient had received three prior myeloma therapies and relapsed with myeloma making up more than 90% of his bone marrow cells just 3 months after autologous transplant.
Dr. James N. Kochenderfer
CD138-positive plasma cells were completely absent, however, one month after infusion of CAR T cells directed against the B-cell maturation antigen (BCMA), and remain undetectable 14 weeks after infusion.
“We have demonstrated for the first time that CAR T cells can have powerful activity against measurable multiple myeloma,” Dr. James N. Kochenderfer of the National Cancer Institute in Bethesda, Md., said at the annual meeting of the American Society of Hematology.
A second patient, who had five prior lines of myeloma therapy and myeloma in 80% of his bone marrow cells, also experienced a dramatic reduction in myeloma, resulting so far in a partial response. The patient has returned to full-time work and myeloma cells continue to decrease 6 weeks after infusion.
The two ongoing responses, however, were associated with the most severe clinical signs of cytokine release syndrome in the late-breaking abstract study (LBA-1), Dr. Kochenderfer said.
The complete responder experienced cytokine release toxicities including fever, tachycardia, hypotension, elevated liver enzymes, and elevated creatinine kinase that resolved. The patient was also platelet transfusion-dependent for 9 weeks after infusion and a baseline absolute neutrophil count of less than 500 microliters remained at that level for 40 days after infusion. All symptoms resolved within two weeks, he said.
The ongoing partial responder experienced fever, tachycardia, hypotension, acute kidney injury, dyspnea, delirium, and prolonged thrombocytopenia and all completely resolved.
Both patients had much higher serum levels of interleukin-6 than the other patients, he noted.
Both patients also received the highest dose level of anti-BCMA CAR T cells. Going forward, that dose will now only be administered to patients with less than 50% bone marrow plasma cells, Dr. Kochenderfer said.
Other responses among the 12 patients treated thus far include 1 transient very good partial response of 8-week duration, 1 transient partial response lasting 2 weeks, and 8 responses of stable disease.
While three new drugs (elotuzumab, daratumumab, ixazomib) were approved for the treatment of multiple myeloma in the month of November alone, this is early days for CAR T-cell therapy in multiple myeloma.
“Almost all of the CAR T-cell work has been in B-cell malignancies, acute lymphocytic leukemia, and chronic lymphocytic leukemia, so is this the right antigen, we don’t know? Is this the right construct, we don’t know? But there’s clearly activity and that is very exciting,” session comoderator Dr. David P. Steensma of the Dana-Farber Cancer Institute in Boston, said in an interview.
Dana-Farber is conducting a CAR T cell trial in myeloma using a different target and NKG2D ligands. Other centers are also using CAR T cells with different targets. “So maybe other targets would have different results and a better safety profile,” he added.
BCMA is an appropriate target for CAR T cell therapy for multiple reasons, Dr. Kochenderfer said. Multiple myeloma is still an incurable disease and BCMA, a member of the tumor necrosis factor superfamily, is uniformly expressed in 60% to 70% of cases.
Preclinical studies by the team also show that BCMA is not detectable in normal human tissues, but is selectively expressed only in bone marrow, lymphoid organs, and organs known to have plasma cells in their lamina propria and by plasma cells and a small fraction of B cells.
The investigators genetically modified autologous T cells to express an anti-BCMA CAR and ligated it into a replication-incompetent gamma retrovirus. The T cells were stimulated with the anti-CD3 monoclonal antibody OKT3 before transduction, with the entire culture process taking 9 days from start to finish. T cells expressing this CAR recognize BCMA with great specificity, Dr. Kochenderfer observed.
The 12 patients received 300 mg/m2 of cyclophosphamide and 30 mg/m2 of fludarabine (Fludara) daily for 3 days before a single infusion of anti-BCMA CAR at dose levels of 0.3 x 106 to 9 x 106 T cells/kg. All patients had at least 3 prior therapies and normal organ function. Five had amyloid light chain only, 4 had immunoglobulin gamma disease, and 4 patients, including the complete responder, had immunoglobulin alpha disease.
It’s unclear why only a few patients responded to the CAR T cells, but dose level was likely a big factor and there is a lot of patient variability with T-cell therapies, Dr. Kochenderfer said at a press briefing.