ORLANDO – A dasatinib-based two-step treatment regimen before allogeneic hematopoietic cell transplantation (alloHCT) for Philadelphia chromosome–positive acute lymphoblastic leukemia (Ph+ALL) reduces relapse and toxicity and improves survival versus an imatinib-based approach, according to findings from the phase 2 Ph+ALL213 study.

Of 78 evaluable patients aged 15-64 years with newly diagnosed BCR/ABL1-positive ALL in the single-arm, multicenter study conducted by the Japanese Adult Leukemia Study Group (JALSG), all but one experienced complete remission (CR or CRi) after dasatinib induction (step 1), and 56% achieved molecular complete response (MCR) after intensive consolidation (IC; step 2), Isamu Sugiura, MD, PhD, reported at the annual meeting of the American Society of Hematology.

The MCR rate increased to 66.2% after the first cycle of consolidation, which included high-dose methotrexate/cytarabine followed by 21 days of 100-mg dasatinib (C1), said Dr. Sugiura of the division of hematology and oncology, Toyohashi Municipal Hospital, Japan.

After all cycles of treatment, the MCR rates before and at 30 and 100 days after transplant were 75.9%, 92.7%, and 93.6%, respectively, he added.

The current standard of care of Ph+ALL is tyrosine kinase inhibitor (TKI)-based chemotherapy followed by alloHCT in the first CR, he said noting that deeper MCR at the time of transplant is associated with the best prognosis.

However, early therapy-related mortality, relapse, and non-relapse mortality remain problematic, he said.

JALSG previously reported results from the Ph+ALL202 and Ph+ALL208 studies, which successfully introduced the TKI imatinib into IC followed by alloHCT for newly diagnosed PH+ALL, establishing the standard of care in Japan, Dr. Sugiura said.

“As the next step, Ph+ALL213 was started to evaluate the introduction of dasatinib and two-step chemotherapy,” he said, explaining that 30%-40% of patients in the prior studies were unable to undergo alloHCT at the first CR because of older age, early relapse, or therapy-related death; benefits in Ph+ALL202, for example, were largely seen in patients younger than age 55 years.

Ph+ALL213 was designed to assess to ability of dasatinib to improve efficacy and reduce toxicity in those settings.

Patients with Eastern Cooperative Oncology Group performance status scores of 0-3 and sufficient organ function were enrolled and underwent step 1 (induction), which targeted hematologic complete response (HCR) by day 28 of dasatinib at a dose of 140 mg daily and day 14 of 60 mg/m² of prednisone, followed by step 2 (IC), which targeted MCR by day 28 of 100-mg dasatinib in combination with CALGB BFM-like intensive chemotherapy, Dr. Sugiura said.

Consolidation included four cycles alternating between the C1 methotrexate/cytarabine/dasatinib regimen and a CHOP-like regimen using vincristine/cyclophosphamide/daunorubicin followed by 21 days of 100-mg dasatinib (C2). Maintenance therapy included 12 cycles of 24 days of 100 mg DA with vincristine/prednisone.

Patients who achieved HCR and had an appropriate donor proceeded to alloHCT after the first cycle of C1 (C1-1), and in those who were minimal residual disease (MRD)–positive just before transplantation, 100 mg dasatinib was given for 10 cycles after alloHCT, whereas MRD-negative patients underwent observation.

Toxicities associated with dasatinib included liver dysfunction in 11 patients (14.1%), and pneumonitis with severe allergic reaction in 1 patient, Dr. Sugiura said, adding that no therapy-related mortality was reported.

Overall, 74.4% of patients underwent transplant, which was significantly greater than the 59.6% who did so in the JALSG Ph+ALL202 trial. Other significant differences between the Ph+ALL213 and 202 trials included the rates of related donor transplants (29.3% vs. 50.8%) and use of reduced-intensity conditioning (31.0% vs. 10.2%), respectively, he said.

At a median follow-up of 48.1 months, 3-year event-free survival in the current trial was 66.2%, and overall survival (OS) was 80.5%, and in the 58 patients who underwent transplant at the first CR, the rates, respectively, were 74.1% and 84.5%. In those with MCR they were 79.5% and 90.9%.

Of note, the presence of additional cytogenetic abnormalities at presentation was associated with worse OS (P = .0346), and the effect was greatest when derivative 22 syndrome was present (P = .00174), Dr. Sugiura said.

MRD state at the time of transplant in first CR also was associated with outcomes; 3-year event-free survival was 79.5% in 44 MRD-negative patients, compared with 57.1% in 14 MRD-positive patients, and 3-year overall survival was 90.9% vs. 64.3%, respectively.

“Survival curves for MRD-positive patients were inferior to those for MRD-negative patients not because of hematological relapse, but because of transplant-related mortality caused by therapy-related complications and gastrointestinal acute [graft-versus-host] disease,” he said.

The findings demonstrate that dasatinib-based two-step induction was highly effective and safe as pretransplant therapy, he said, noting that transplant was “maximally used,” and although 16% of patients relapsed, both relapse- and non-relapse-related mortality were minimized, with rates of 8.6% and 10.3%, respectively, after transplant.

Longer observation and a larger study are required to confirm these findings, Dr. Sugiura said, noting that the phase 2 JALSG Ph+ALL219 study will look at the potential for further improving outcomes with the addition of the multitargeted TKI ponatinib in patients who are MRD-positive after IC.

This study was funded by the Ministry of Health, Labor and Welfare of Japan. Dr. Sugiura reported having no disclosures.

sworcester@mdedge.com

SOURCE: Sugiura I et al. ASH 2019. Abstract 743.

Phase 2 study shows regimen benefit with dasatinib in Ph+ALL therapy