Long-Term Follow up of Blinatumomab in Older Patients with B-Cell Acute Lymphoblastic Leukemia.

Older adults who are diagnosed with acute lymphoblastic leukemia (ALL) and are treated with chemotherapy generally have poor outcomes. Blinatumomab is a CD19/CD3 bispecific T-cell engager that has been approved for the treatment of B-cell ALL in the relapsed/refractory setting or in patients with minimal residual disease (MRD) positivity. We previously reported on a small cohort of older adults with newly diagnosed Philadelphia chromosome negative B-cell ALL who were treated with blinatumomab monotherapy in the first line setting. This is a long-term follow up of those patients and their clinical courses. All five patients achieved complete remission (CR) after one cycle of blinatumomab, and three were MRD-negative. Two patients completed three cycles of blinatumomab, two patients completed four cycles of blinatumomab, and one patient completed 17 cycles of blinatumomab total. In the last four years, four of these patients had relapsed disease requiring additional therapy. Two patients are alive after 61 months and 57 months since their first cycle of blinatumomab. Two of the patients died at 10 months and one died at 20 months. Here we describe the long-term clinical courses of these patients.

Methylthioadenosine phosphorylase (MTAP)-deficient T-cell ALL xenografts are sensitive to pralatrexate and 6-thioguanine alone and in combination.

PURPOSE: To investigate the effectiveness of a combination of 6-thioguanine (6-TG) and pralatrexate (PDX) in methylthioadenosine phosphorylase (MTAP)-deficient T-cell acute lymphoblastic leukemia (T-cell ALL). METHODS: CCRF-CEM (MTAP(-/-)) and Molt4 (MTAP(+/+)) T-cell ALL cell lines were treated with 6-TG or PDX and evaluated for efficacy 72 h later. NOD/SCID gamma mice bearing CEM or Molt4 xenografts were treated with 6-TG and PDX alone or in combination to evaluate antitumor effects. RESULTS: CEM cells were more sensitive to 6-TG and PDX in vitro than Molt4. In vivo, CEM cells were very sensitive to PDX and 6-TG, whereas Molt4 cells were highly resistant to 6-TG. A well-tolerated combination of PDX and 6-TG achieved significant tumor regression in CEM xenografts. CONCLUSIONS: The loss of MTAP expression may be therapeutically exploited in T-cell ALL. The combination of 6-TG and PDX, with the inclusion of leucovorin rescue, allows for a safe and effective regimen in MTAP-deficient T-cell ALL.

Leucovorin rescue allows effective high-dose pralatrexate treatment and an increase in therapeutic index in mesothelioma xenografts.

PURPOSE: To investigate the ability of leucovorin (LV) to abrogate dose-limiting toxicities of pralatrexate (PDX) while maintaining efficacy, in vivo. METHODS: H2052 mesothelioma cells were treated with the antifolates methotrexate (MTX), PDX and pemetrexed, with and without LV rescue 24 h later. Cell killing was evaluated 48 h later. Female nude mice bearing H2052 xenografts were treated with varying doses and schedules of the antifolate PDX and LV. RESULTS: In vitro, H2052 cells were more sensitive to PDX as compared to MTX and pemetrexed. Administration of LV 24 h after antifolate treatment reduced efficacy of antifolates MTX and pemetrexed, but not PDX. In vivo, LV was found to reduce toxicity of PDX at the maximum tolerated dose without sacrificing efficacy. Lethal doses of PDX were rescued by LV, and mice bearing the H2052 tumor demonstrated prolonged and enhanced tumor regression. CONCLUSIONS: High-dose PDX with subsequent LV rescue may be a viable treatment strategy in mesothelioma and other cancers. The inclusion of LV rescue into new and existing PDX treatment protocols should be explored as a way to expand the tolerability and effectiveness of PDX in the clinic.