Early data hint that immune checkpoint inhibitors may be able to restore antitumor activity in patients with hematologic malignancies that have relapsed after allogeneic transplant.
Among 22 patients with relapsed hematologic cancers following allogeneic hematopoietic stem cell transplantation (HSCT) in a phase I/Ib study, treatment with the anti-CTLA-4 antibody ipilimumab (Yervoy) at a dose of 10 mg/kg was associated with complete responses in five patients, partial responses in two, and decreased tumor burden in six, reported Matthew S. Davids, MD, of the Dana-Farber Cancer Institute in Boston, and his colleagues.
Dr. Matthew S. Davids
“CTLA-4 blockade was a feasible approach for the treatment of patients with relapsed hematologic cancer after transplantation. Complete remissions with some durability were observed, even in patients with refractory myeloid cancers,” they wrote (N Engl J Med. 2016 Jul 14. doi: 10.1056/NEJMoa1601202).
More than one-third of patients who undergo HSCT for hematologic malignancies such as lymphoma, multiple myeloma, or leukemia will experience a relapse, and most will die within a year of relapse despite salvage therapies or retransplantation, the authors noted.
“Immune escape (i.e., tumor evasion of the donor immune system) contributes to relapse after allogeneic HSCT, and immune checkpoint inhibitory pathways probably play an important role,” they wrote.
Selective CTLA-4 blockade has been shown in mouse models to treat late relapse after transplantation by augmenting graft-versus-tumor response without apparent exacerbation of graft-versus-host disease (GVHD). To see whether the use of a CTLA-4 inhibitor could have the same effect in humans, the investigators instituted a single-group, open-label, dose-finding, safety and efficacy study of ipilimumab in 28 patients from six treatment sites.
The patients had all undergone allogeneic HSCT more than 3 months before the start of the study. The diagnoses included acute myeloid leukemia (AML) in 12 patients (including 3 with leukemia cutis and 1 with a myeloid sarcoma), Hodgkin lymphoma in 7, non-Hodgkin lymphoma in 4, myelodysplastic syndrome (MDS) in 2, and multiple myeloma, myeloproliferative neoplasm, and acute lymphoblastic leukemia in 1 patient each. Eight of the patients had previously had either grade I or II acute GVHD; 16 had had chronic GVHD.
Patients received induction therapy with ipilimumab at a dose of either 3 mg/kg (6 patients), or 10 mg/kg (22 patients) every 3 weeks for a total of 4 doses. Patients who experienced a clinical benefit from the drug could receive additional doses every 12 weeks for up to 60 weeks.
There were no clinical responses meeting study criteria in any of the patients who received the 3-mg/kg dose. Among the 22 who received the 10-mg/kg dose, however, the rate of complete responses was 23% (5 of 22), partial responses 9% (2 of 22), and decreased tumor burden 27% (6 of 22). The remaining nine patients experienced disease progression.
Four of the complete responses occurred in patients with extramedullary AML, and one occurred in a patient with MDS transforming into AML.
The safety analysis, which included all 28 patients evaluable for adverse events, showed four discontinuations due to dose-limiting chronic GVHD of the liver in the 3 patients, and acute GVHD of the gut in 1, and to severe immune-related events in one additional patient, leading to the patient’s death.
Other grade 3 or greater adverse events possibly related to ipilimumab included acute kidney injury (one patient) , corneal ulcer (one), thrombocytopenia (nine), neutropenia (three), anemia and pleural effusion (two).
The investigators point out that therapy to stimulate a graft-versus-tumor effect has the potential to promote or exacerbate GVHD, as occurred in four patients in the study. The GVHD in these patients was effectively managed with glucocorticoids, however.
The National Institutes of Health, Leukemia and Lymphoma Society, Pasquarello Tissue Bank, and Dana-Farber Cancer Institute supported the study. Dr. Davids disclosed grants from ASCO, the Pasquarello Tissue Bank, NIH, NCI, and Leukemia and Lymphoma society, and personal fees from several companies outside the study. Several coauthors disclosed relationships with various pharmaceutical companies, including Bristol-Myers Squibb, maker of ipilimumab.