A chimeric antigen receptor (CAR) construct using transduced natural killer cells instead of T cells was associated with a high complete remission rate without the cytokine release syndrome frequently seen with CAR T cell therapy, early clinical trial results show.
The construct, consisting of natural killer (NK) cells derived from umbilical cord blood that have been transduced to target CD19-expressing cells combined with interleukin 15 and equipped with an “off” switch, offers the prospect of an off-the-shelf CAR product, reported Enli Liu, MD, and colleagues at the University of Texas MD Anderson Cancer Center in Houston.
“We found that allogeneic CAR-NK cells can be delivered in adoptive transfer without the serious cytokine release syndrome and neurologic toxic effects that have been associated with CAR T-cell therapy,” they wrote in The New England Journal of Medicine.
The modified NK cells were delivered to 9 of 11 patients with only partial human leukocyte antigen (HLA) matching, and in 2 patients with no matching, yet there were no cases of graft-versus host disease (GvHD), and no patients had symptoms of cytokine release syndrome (CRS), neurotoxicity, or hemophagocytic lymphohistiocytosis.
CAR T cell production “is a cumbersome process that requires coordination and collection of the cells and there’s several weeks of manufacturing, during which time patients often can have their lymphoma worsen, and so at times it’s a little bit of a race against the clock to get those cells manufactured,” Brian Hill, MD, PhD, director of the lymphoid malignancies program at Taussig Cancer Institute at Cleveland Clinic, said in an interview.
Dr. Hill, who was not involved in the study, said that the proof-of-principle study shows promising early results and offers the prospect of an effective and safe off-the-shelf therapeutic option for patients with lymphoid malignancies.
Advanced B-cell cancers
The investigators conducted a phase 1/2 trial in patients with B-cell lymphoid malignancies, including five patients with chronic lymphocytic leukemia (CLL), one patient with Richter’s transformation and one with accelerated CLL, three with transformed follicular lymphoma, two with diffuse large B-cell lymphoma (DLBCL), and one with follicular lymphoma (focally grade 3B).
The patients were all heavily pretreated, with 3 to as many as 11 prior lines of therapy.
The patients received cord blood-derived NK cells that had been transduced with a retroviral vector expressing genes that encode anti-CD19 CAR, interleukin-15, and inducible caspase 9 as a safety switch.
The cells were expanded in the lab and after the patients underwent lymphodepleting chemotherapy, they received the cells in a single infusion at one of three doses, either 1×105, 1×106, or 1×107 CAR-NK cells per kilogram of body weight.
As noted before, there were no cases of CRS, neurotoxicity, or GvHD and no increase over baseline in inflammatory cytokines, including interleukin-6, a key factor in the development and severity of CRS. The maximum tolerated dose was not reached.
Early efficacy
Of the 11 patients, 8 had a clinical response, and 7 had a complete remission, including 4 patients with lymphomas and 3 with CLL.
The patient with CLL with Richter’s transformation had a remission of the Richter’s component, but not of the CLL itself.
“This is particularly remarkable, because these patients are notoriously very difficult to treat, and the efficacy of autologous CAR T cell therapy in CLL and Richter’s patients has been hampered by lack of fitness of the patient’s own T cells when manufacturing the CAR T cell product, so this approach may obviate the need for autologous T cells in these patients,” Dr. Hill said.
The responses were rapid and occurred within 30 days of infusion at all dose levels. In addition, there was evidence of expansion and persistence of the modified NK cells at low levels for at least 1 year, despite the HLA mismatches between the NK cells and the recipients. The investigators speculated that the inclusion of interleukin-15 in the NL construct may at least partially account for the persistence of the cells and their antitumor activity.
Of the eight patients with a response, five had postremission therapy, including two patients with CLL who had minimal residual disease (MRD), one patient with follicular lymphoma and one with transformed follicular lymphoma who underwent hematopoietic stem-cell transplantation while in complete remission without evidence of MRD, and the patient with CLLL with Richter’s transformation with remission of the lymphoma component, who received a course of venetoclax.
The authors acknowledged that it may be difficult to assess the durability of response after CAR NK therapy in this study because of the allowed consolidation therapy for patients in remission.
They noted that although the patients in the current study each had a fresh CAR NK product manufactured for them, “we have shown that it is possible to produce more than 100 doses of CAR-NK cells from a single cord-blood unit. This capability, together with the apparently minimal HLA-matching requirements between the donor of CAR-NK cells and the patient, may pave the way for a truly off-the-shelf product that could increase treatment accessibility for many more patients.”
The National Institutes of Health supported the study. Dr. Liu disclosed a pending patent for methods of production of CAR-NK cells, and a patent held by MD Anderson for methods of treatment with NK cells. Dr. Hill is a member of the Hematology News editorial advisory board.
SOURCE: Liu E et al. N Engl J Med. 2020 Feb 6;382:545-53.