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Contextualizing the Use of Moxetumomab Pasudotox in the Treatment of Relapsed or Refractory Hairy Cell Leukemia.

ABSTRACT: Hairy cell leukemia (HCL) is an indolent B-cell malignancy characterized by high initial sensitivity to purine analog chemotherapy, minimal residual disease (MRD) frequently accompanying complete remission (CR), and relapses requiring additional treatment. Repeat chemotherapy shows decreasing efficacy and increasing toxicity with each course. Newer therapies targeting BRAF/MEK or Bruton's tyrosine kinase are effective but generally leave MRD. Rituximab has modest activity as a single agent and can achieve MRD-negative CR in combination with purine analogs, but there is significant toxicity from the chemotherapy. Moxetumomab pasudotox-tdfk (Moxe) is a biologic containing an antibody fragment (Fv) binding to CD22, attached to a portion of Pseudomonas exotoxin A. Binding to CD22 enables the toxin to enter and kill cells. Moxe is administered by 30-minute infusions on days 1, 3, and 5 of up to six cycles spaced 4?weeks apart. In phase I testing, 64% of 33 patients at the highest dose level achieved CR, most without MRD. Lack of MRD correlated with prolonged CR duration; of 11 MRD-negative CRs, 10 were still in CR after a median of 42 months of observation. In pivotal testing, 75% of 80 patients had a hematologic response, 41% with CR; 82% (27/33) of CRs were MRD-negative, and only 4 of the 27 MRD-negative patients relapsed during the follow-up period. Hemolytic uremic syndrome and capillary leak syndrome were each observed in 9% of patients, all reversible. In September 2018, the U.S. Food and Drug Administration approved Moxe for the treatment of relapsed/refractory HCL after ?2 prior therapies. Moxe is undergoing further development in combination with rituximab. IMPLICATIONS FOR PRACTICE: Hairy cell leukemia (HCL) has effective treatments including purine analogs with and without rituximab, and oral inhibitors of BRAF, MEK and Bruton's tyrosine kinase (BTK). Despite these therapies, relapse occurs, and moxetumomab pasudotox has an important role in relapsed and refractory HCL because of its ability to achieve high rates of complete remissions (CRs) without chemotherapy; most of these CRs are without minimal residual disease (MRD). CR duration is enhanced in patients who achieve eradication of MRD. To improve the efficacy of this recombinant immunotoxin, a phase I trial is underway in combination with rituximab to reduce tumor burden and decrease immunogenicity.

SUBMITTER: Kreitman RJ

PROVIDER: S-EPMC6964124 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Contextualizing the Use of Moxetumomab Pasudotox in the Treatment of Relapsed or Refractory Hairy Cell Leukemia.

Kreitman Robert J RJ Pastan Ira I

The oncologist 20191018 1

Hairy cell leukemia (HCL) is an indolent B-cell malignancy characterized by high initial sensitivity to purine analog chemotherapy, minimal residual disease (MRD) frequently accompanying complete remission (CR), and relapses requiring additional treatment. Repeat chemotherapy shows decreasing efficacy and increasing toxicity with each course. Newer therapies targeting BRAF/MEK or Bruton's tyrosine kinase are effective but generally leave MRD. Rituximab has modest activity as a single agent and c ...[more]

PMID: 31628266

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Project description:BackgroundMoxetumomab pasudotox is a recombinant CD22-targeting immunotoxin. Here, we present the long-term follow-up analysis of the pivotal, multicenter, open-label trial (NCT01829711) of moxetumomab pasudotox in patients with relapsed/refractory (R/R) hairy cell leukemia (HCL).MethodsEligible patients had received ≥ 2 prior systemic therapies, including ≥ 2 purine nucleoside analogs (PNAs), or ≥ 1 PNA followed by rituximab or a BRAF inhibitor. Patients received 40 µg/kg moxetumomab pasudotox intravenously on Days 1, 3, and 5 of each 28-day cycle for up to six cycles. Disease response and minimal residual disease (MRD) status were determined by blinded independent central review. The primary endpoint was durable complete response (CR), defined as achieving CR with hematologic remission (HR, blood counts for CR) lasting > 180 days.ResultsEighty adult patients were treated with moxetumomab pasudotox and 63% completed six cycles. Patients had received a median of three lines of prior systemic therapy; 49% were PNA-refractory, and 38% were unfit for PNA retreatment. At a median follow-up of 24.6 months, the durable CR rate (CR with HR > 180 days) was 36% (29 patients; 95% confidence interval: 26-48%); CR with HR ≥ 360 days was 33%, and overall CR was 41%. Twenty-seven complete responders (82%) were MRD-negative (34% of all patients). CR lasting ≥ 60 months was 61%, and the median progression-free survival without the loss of HR was 71.7 months. Hemolytic uremic and capillary leak syndromes were each reported in ≤ 10% of patients, and ≤ 5% had grade 3-4 events; these events were generally reversible. No treatment-related deaths were reported.ConclusionsMoxetumomab pasudotox resulted in a high rate of durable responses and MRD negativity in heavily pre-treated patients with HCL, with a manageable safety profile. Thus, it represents a new and viable treatment option for patients with R/R HCL, who currently lack adequate therapy.Trial registrationClinicalTrials.gov identifier: NCT01829711; first submitted: April 9, 2013. https://clinicaltrials.gov/ct2/show/NCT01829711.

Project description:BRAF V600E is the genetic lesion underlying hairy-cell leukemia. We assessed the safety and activity of the oral BRAF inhibitor vemurafenib in patients with hairy-cell leukemia that had relapsed after treatment with a purine analogue or who had disease that was refractory to purine analogues.We conducted two phase 2, single-group, multicenter studies of vemurafenib (at a dose of 960 mg twice daily)--one in Italy and one in the United States. The therapy was administered for a median of 16 weeks in the Italian study and 18 weeks in the U.S. study. Primary end points were the complete response rate (in the Italian trial) and the overall response rate (in the U.S. trial). Enrollment was completed (28 patients) in the Italian trial in April 2013 and is still open (26 of 36 planned patients) in the U.S. trial.The overall response rates were 96% (25 of 26 patients who could be evaluated) after a median of 8 weeks in the Italian study and 100% (24 of 24) after a median of 12 weeks in the U.S. study. The rates of complete response were 35% (9 of 26 patients) and 42% (10 of 24) in the two trials, respectively. In the Italian trial, after a median follow-up of 23 months, the median relapse-free survival was 19 months among patients with a complete response and 6 months among those with a partial response; the median treatment-free survival was 25 months and 18 months, respectively. In the U.S. trial, at 1 year, the progression-free survival rate was 73% and the overall survival rate was 91%. Drug-related adverse events were usually of grade 1 or 2, and the events most frequently leading to dose reductions were rash and arthralgia or arthritis. Secondary cutaneous tumors (treated with simple excision) developed in 7 of 50 patients. The frequent persistence of phosphorylated ERK-positive leukemic cells in bone marrow at the end of treatment suggests bypass reactivation of MEK and ERK as a resistance mechanism.A short oral course of vemurafenib was highly effective in patients with relapsed or refractory hairy-cell leukemia. (Funded by the Associazione Italiana per la Ricerca sul Cancro and others; EudraCT number, 2011-005487-13; ClinicalTrials.gov number NCT01711632.).

Dataset Information

Contextualizing the Use of Moxetumomab Pasudotox in the Treatment of Relapsed or Refractory Hairy Cell Leukemia.

Publications

Contextualizing the Use of Moxetumomab Pasudotox in the Treatment of Relapsed or Refractory Hairy Cell Leukemia.

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