Blinatumomab + Ponatinib for Relapsed Ph1-Positive Acute Lymphoblastic Leukemia: The French Experience

Prognosis of Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph1+ ALL) has been considerably improved since the beginning of the BCR-ABL1 tyrosine kinase inhibitors (TKI) era 20 years ago. However, the prognosis of patients with a refractory/relapsed (including molecular relapse) disease is still very dismal. New drugs or combination of new drugs may improve outcomes of these patients. For example, ponatinib, a 3^rd-generation oral TKI, known to have activity against BCR-ABL1 T315I mutations, has shown some efficacy in this context. Similarly, a recent study has reported very encouraging results of the bispecific anti-CD3/CD19 monoclonal antibody blinatumomab as single-agent in refractory/relapsed Ph1+ ALL. Data regarding the efficacy and tolerance of a combination of blinatumomab+ponatinib (blina/pona) are still scarce.

This was a retrospective study with the aim to report outcomes of patients receiving a combination of blina/pona for refractory/relapsed Ph1+ ALL in France. Fifteen adults from 8 French centers were identified and data were collected by physicians of each centers, then gathered for the purpose of this study.

There were 9 males and 6 females, with a median age of 53 years (range:17-72). All patients, but 2 with blast crisis of chronic myeloid leukemia, had de novo Ph1+ ALL. Four cases had BCR-ABL1 T315I mutation. Patients received the blina/pona combination, either after a first (n=8) or a second (n=7) cytologic relapse. There was no refractory patient in theses series. Previous allograft and autograft has been performed in 7 and 2 patients, respectively. The majority of patients (n=12) had previously received 2 or more lines of TKI. The median time between the first cycle of blina/pona and diagnosis was 14 months (range: 8-40). The median number of blinatumomab cycle (28 mg/day by continuous infusion for 28 days every 6 weeks) administered per patient was 3 (range: 1-6) while ponatinib was concomittantly administered continuously at an initial dose of 45 mg once daily in 11 pts (73%) and 30 mg in 4 pts (27%). Median duration of ponatinib administration was 4 months (range: 1.1-10.9) from first blinatumomab cycle. The toxicity profile was safe: all patients received a complete first cycle without grade 3-4 adverse events. After cycle 1, blinatumomab was stopped in 47% of cases because of neurologic events in 4 and infections in 3; ponatinib was stopped in 33% of cases because of neurologic events in 3, fluid retention in 1 and severe arteriopathy in 1 patient with other vascular disease risk factors. All neurologic events resolved after stopping blinatumomab or ponatinib.

The majority of patients were evaluated after one cycle (n=11, after cycle 2 n=3, after cycle 3 n=1). All but one patients (93%) obtained a cytologic complete remission (CR), of whom 12/14 (86%) achieved a complete molecular response. However, 2 patients were documented with CNS relapse at the time of blina/pona evaluation although in bone marrow molecular remission. Both obtained clearance of leukemic blasts after intrathecal infusion of chemotherapy. Then, 5 patients underwent allogeneic transplant (including 2 patients already allotransplanted before blina/pona) and 1 patient received donor lymphocyte infusion. Seven cases pursued maintenance therapy with ponatinib as single agent after stopping blinatumomab. With a median follow-up of 8 months (range: 2.6-30.2) for alive patients, median overall and leukemia-free survivals from first cycle of blina/pona were 8.5 months (range: 1.7-30.2) and 8 months (range: 1.3-30.2), respectively.

At last follow-up (July 2018), only 4 relapses had occurred at a median of 3.3 months (range: 1.3-8.3) from first blina/pona cycle and 6 patients had died (3 bacterial infections, 1 fungal infection, 1 secondary cancer and 1 ALL relapse). All alive patients (n=9) but one (cytologic CR but detectable minimal residual disease) are in complete molecular response. Four patients are still under ponatinib medication at last follow-up.

The combination of blinatumomab+ponatinib appears effective and tolerable in relapsed Ph1+ALL patients and may replace chemotherapy salvage regimens. The combination should be tested in first-line therapy in the future. Our results have also to be confirmed prospectively on a larger cohort of patients.