Results of a phase 1/2 trial suggest treatment with haploidentical natural killer (NK) cells can be effective against relapsed/refractory myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML).
NK-cell therapy elicited responses in 6 of the 16 patients studied and provided a bridge to transplant for 5 patients.
Three responders were still alive at more than 3 years of follow-up.
There were 4 grade 3 adverse events (AEs) and 2 grade 5 AEs considered possibly or probably related to NK-cell therapy.
Investigators reported these results in Clinical Cancer Research.
The trial enrolled 16 patients. Eight had MDS/AML, 3 had de novo AML, and 5 had high-risk MDS, including refractory anemia with excess blasts (RAEB) type 1 progressing toward type 2, RAEB-2, and chronic myelomonocytic leukemia type 2.
The patients’ median age was 64 (range, 40-70), and they had received a median of 3 prior therapies (range, 1-6). Six patients had received an allogeneic hematopoietic stem cell transplant (HSCT).
For this study, all patients received fludarabine, cyclophosphamide, and total lymphoid irradiation prior to receiving haploidentical NK cells.
The median follow-up was 8 months for all patients and 28 months for responders.
Six patients responded to treatment. One patient with de novo AML had a complete response (CR). Two high-risk MDS patients had a marrow CR (mCR), as did 2 MDS/AML patients. One MDS/AML patient had a partial response (PR).
Two patients had stable disease (SD)—1 with MDS and 1 with MDS/AML. One patient with de novo AML had a morphologic leukemia-free state after NK-cell therapy.
Five patients proceeded to HSCT—3 in mCR, 1 in PR, and 1 with SD.
Three patients were still alive at last follow-up—1 with MDS who achieved an mCR and went on to HSCT, 1 with MDS/AML who achieved an mCR and went on to HSCT, and 1 with MDS/AML who achieved an mCR and went on to receive chemotherapy and donor lymphocyte infusion.
One survivor has more than 5 years of follow-up (the MDS patient), and the other 2 have more than 3 years of follow-up.
“Our study shows that patients with MDS, AML, and MDS/AML can be treated with NK cell-based immunotherapy and that the therapy can be highly efficacious,” said study author Hans-Gustaf Ljunggren, MD, PhD, of Karolinska Institutet in Stockholm, Sweden.
The most common AEs of any grade considered possibly or probably related to NK-cell therapy were chills (n=13) and nausea (n=4).
Two patients had cytokine release syndrome (CRS) likely associated with hemophagocytic lymphohistiocytosis (HLH).
Each of the following potentially related AEs were reported once: headache, vomiting, encephalitis infection, sinus tachycardia, bone pain, pain in extremity, and maculopapular rash.
There were 4 grade 3 AEs—CRS/HLH (n=1), chills (n=1), and nausea (n=2)—but no grade 4 AEs.
There were 2 grade 5 AEs—CRS/HLH and encephalitis infection. These occurred in a single patient who died with HLH, human herpes virus-6 encephalitis, and AML relapse.
Two investigators involved in this study serve on the scientific advisory board of Fate Therapeutics. Dr Ljunggren serves on the scientific advisory board of CellProtect, Nordic Pharmaceuticals, and HOPE Bio-Sciences. He is also on the board of directors of Vycellix and is a collaborator with Fate Therapeutics.