For adults with Philadelphia chromosome–positive acute lymphoblastic leukemia (Ph+ALL), frontline therapy with the chemotherapy-free combination of ponatinib (Iclusig) and blinatumomab (Blincyto) shows promise as an alternative to early hematopoietic stem cell transplantation (HSCT), investigators in a single-arm phase 2 study reported.
In an interim analysis of the combination in patients with newly diagnosed or relapsed/refractory Ph+ALL or lymphoid accelerated or blast phase chronic myeloid leukemia (CML), 20 patients who received it as frontline therapy had a rate of complete responses (CR) or complete responses with partial recovery of blood counts (CRp) of 100% and a complete molecular remission (CMR) rate of 85%, reported Nicholas Short, MD, of the University of Texas MD Anderson Cancer Center in Houston.
“This translated into an estimated 2-year overall survival of 93%, with no patients undergoing transplant in first remission, and none having relapse at last follow-up,” he said in an oral abstract presented during the European Hematology Association annual congress.
Among patients with relapsed/refractory Ph+ALL, the CR/CRp rate was 89%, the CMR rate was 88%, and the estimated 2-year overall survival rate was 53%, he said.
Transplants on hold
“The big selling point is the ability to avoid stem cell transplant, which is not always the first thing you do in Ph-positive ALL, but it’s always on your mind,” said Gwen Nichols, MD, chief medical officer of the Leukemia and Lymphoma Society, who was not involved in the study.
“It looks, albeit with very limited follow-up, that patients haven’t relapsed yet such that transplant would be necessary. Anything we can do to avoid people having long-term complications that go along with an allogeneic transplant is a step in the right direction,” she said in an interview.
One combination, three cohorts
Ph+ALL comprises about 25% of all adult ALL. The standard of care in newly diagnosed patients is chemotherapy plus a tyrosine kinase inhibitor (TKI) targeted against the BCR-ABL transcript.
Ponatinib is a pan-BCR-ABL TKI that has been shown to have activity against ALL with T315I mutations, which are present in about 75% of the cases of relapsed disease, Dr. Short said.
Blinatumomab is a bi-specific T-cell engager (BiTe) that has been shown to be effective as monotherapy against relapsed/refractory Ph+ALL as monotherapy and in combination with dasatinib.
Dr. Short and colleagues enrolled patients with newly diagnosed or relapsed/refractory Ph+ALL or lymphoid accelerated or blast phase CML. Patients in the frontline cohort could have received one or two prior lines of chemotherapy with or without a TKI.
The patients all had Eastern Cooperative Oncology Group performance status of 0-2, and adequate liver function.
Patients with clinically significant cardiovascular disease or central nervous system disease pathology were excluded, except that patients with CNS leukemia could be enrolled.
The induction phase consisted of 30 mg ponatinib daily plus blinatumomab standard dosing on a 4-week-on, 2-week-off schedule. Patients in CMR, defined for frontline patients as undetectable BCR-ABL transcripts by polymerase chain reaction, then received up to four consolidation cycles of the regimen with ponatinib at a 15-mg dose, followed by 5 years of ponatinib 15-mg maintenance. All patients also received CNS prophylaxis with 12 cycles of intrathecal chemotherapy with alternating administration of methotrexate and cytarabine.
Of the 35 patients treated to date with the combination, 20 with Ph+ALL received it as frontline therapy and 10 received it for relapsed/refractory disease; 5 patients with CML in lymphoid blast phase also were treated.