Researchers consider R/R ALL drugs in the first-line setting

CHICAGO – Novel antibodies are improving outcomes in relapsed and refractory acute lymphoblastic leukemia (ALL), and the hope is that they will also show benefit in the up-front treatment setting and thereby improve overall outcomes, according to Anjali Advani, MD.

“It has been a really exciting time in ALL because several drugs have now been FDA approved: blinatumomab, inotuzumab, and now – for patients who are less than 26 years of age – we actually have CAR [chimeric antigen receptor] T cells that have been approved,” Dr. Advani, a hematologist and director of the inpatient leukemia program at the Cleveland Clinic said at the American Society of Hematology Meeting on Hematologic Malignancies.

At the time of relapse, however, the only known cure is allogeneic bone marrow transplant. That may change as more data regarding CAR T cells become available, but the typical goal at this time is to get patients into remission and then to transplant, she said.

Blinatumomab

“Blinatumomab is a very interesting antibody,” Dr. Advani said, explaining that it is a bispecific, T cell–engaging antibody with an anti-CD3 arm that engages the T cell and an anti-CD19 antibody that engages the B lymphoblast.

“Basically this drug then acts as a bridge between the lymphoblast and the T cell to lead to proliferation of the cytotoxic T cell and apoptosis of the lymphoblast,” she said. “It’s interesting because it’s an antibody but it actually works through the immune system through the T cells.”

The largest study to date of blinatumomab in the relapsed/refractory ALL setting showed a 43% complete remission (CR) or CR with partial hematological recovery of peripheral blood counts (CRi) in 189 treated patients with Philadelphia chromosome–negative ALL. It also demonstrated and a 39% rate of salvage status 2 or higher, she said, noting that the response was impressive given that about 30% of participants had a prior transplant (Lancet. 2015 Jan 1;16[1]:57-66).

Of the responders, 40% went on to allogeneic transplant. This was a “fairly impressive” rate given the 30% prior-transplant rate, Dr. Advani said.

“There also was a high minimal residual disease response in those patients achieving CR,” she said, adding that the only significant predictor of response was bone marrow blast count; patients with 50% or more blasts in the bone marrow had a reduced likelihood of responding to blinatumomab.

The agent was approved by the Food and Drug Administration in December 2014 based on these phase 2 findings.

Adverse events mainly included toxicities that are expected in leukemia patients; the most frequent were febrile neutropenia, neutropenia, and anemia. Two patients developed cytokine release syndrome, and about half of the blinatumomab-treated patients experienced neurological events, although the majority of those were grade 1 or 2 and were easily manageable, she noted.

Blinatumomab was further evaluated in the phase 3 TOWER study (NCT02013167), which compared it with standard-of-care chemotherapy regimens. This study showed much higher response rates with blinatumomab than with the chemotherapy regimens (CR with full, partial, or incomplete hematologic recovery, 44% vs. 25%, respectively), Dr. Advani said (N Engl J Med. 2017 Mar 2;376[9]:836-47).

“The main things to remember [are that blinatumomab is] generally very well tolerated and it has been shown to be superior over standard chemotherapy,” she said. “I think it’s a very good drug to use as a bridge to transplant.”

One setting where blinatumomab perhaps should not be used is in patients with central nervous system disease, she noted.

“There is some concern, at least theoretically, that if you have to use concurrent intrathecal chemo along with blinatumomab, there could be some neurotoxicity,” Dr. Advani said, adding that there are no clear data in that setting because patients with CNS disease were not included in the trials.

Patients with high tumor burden may also be poor candidates for blinatumomab because they tend to have lower response rates.

“That doesn’t mean you can’t use it, but you have to kind of think about what the best option would be,” she said.

Additionally, patients treated with CAR T-cell therapy may develop CD19 loss or CD19-negative disease, and blinatumomab should be avoided in these patients.

“The nice thing ... is you don’t have to worry about veno-occlusive disease [VOD] in patients who are proceeding to transplant,” she said, explaining that no increased risk of VOD was seen in these trials.