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Results of a phase 1 study suggest that repeated doses of the immunotherapy drug ipilimumab is a feasible treatment option for patients with hematologic diseases who relapse after allogeneic hematopoietic stem cell transplant (HSCT).
Seven of the 28 patients studied responded to the treatment, but immune-mediated toxic effects and graft-vs-host disease (GVHD) occurred as well.
These results were published in NEJM.
Ipilimumab, which is already approved to treat unresectable or metastatic melanoma, works by blocking the immune checkpoint CTLA-4. Blockade of CTLA-4 has been shown to augment T-cell activation and proliferation.
“We believe [,in the case of relapse after HSCT,] the donor immune cells are present but can’t recognize the tumor cells because of inhibitory signals that disguise them,” said study author Matthew Davids, MD, of the Dana-Farber Cancer Institute in Boston, Massachusetts.
“By blocking the checkpoint, you allow the donor cells to see the cancer cells.”
Dr Davids and his colleagues tested this theory in 28 patients who had relapsed after allogeneic HSCT. The patients had acute myeloid leukemia (AML, n=12), Hodgkin lymphoma (n=7), non-Hodgkin lymphoma (n=4), myelodysplastic syndromes (MDS, n=2), multiple myeloma (n=1), myeloproliferative neoplasm (n=1), or acute lymphoblastic leukemia (n=1).
Patients had received a median of 3 prior treatment regimens, excluding HSCT (range, 1 to 14), and 20 patients (71%) had received treatment for relapse after transplant. Eight patients (29%) previously had grade 1/2 acute GVHD, and 16 (57%) previously had chronic GVHD.
The median time from transplant to initial treatment with ipilimumab was 675 days (range, 198 to 1830), and the median time from relapse to initial treatment with ipilimumab was 97 days (range, 0 to
1415).
Patients received induction therapy with ipilimumab at a dose of 3 mg/kg or 10 mg/kg every 3 weeks for a total of 4 doses. Those who had a clinical benefit received additional doses every 12 weeks for up to 60 weeks.
Safety
Five patients discontinued ipilimumab due to dose-limiting toxic effects. Four of these patients had GVHD, and 1 had severe immune-related adverse events.
Dose-limiting GVHD presented as chronic GVHD of the liver in 3 patients and acute GVHD of the gut in 1 patient.
Immune-related adverse events included death (n=1), pneumonitis (2 grade 2 events, 1 grade 4 event), colitis (1 grade 3 event), immune thrombocytopenia (1 grade 2 event), and diarrhea (1 grade 2 event).
Efficacy
There were no responses in patients who received ipilimumab at 3 mg/kg. Among the 22 patients who received ipilimumab at 10 mg/kg, 5 had a complete response, and 2 had a partial response.
Six other patients did not qualify as having responses but had a decrease in their tumor burden. Altogether, ipilimumab reduced tumor burden in 59% of patients.
The complete responses occurred in 4 patients with extramedullary AML and 1 patient with MDS developing into AML. Two of the AML patients remained in complete response at 12 and 15 months, and the patient with MDS remained in complete response at 16 months.
At a median follow-up of 15 months (range, 8 to 27), the median duration of response had not been reached. Responses were associated with in situ infiltration of cytotoxic CD8+ T cells, decreased activation of regulatory T cells, and expansion of subpopulations of effector T cells.
The 1-year overall survival rate was 49%.
The investigators said these encouraging results have set the stage for larger trials of checkpoint blockade in this patient population. Further research is planned to determine whether immunotherapy drugs could be given to high-risk patients to prevent relapse.
