Phase II Trial Assessing Safety and Preliminary Efficacy of High-Dose Intravenous Ascorbic Acid and Decitabine in TET2-Mutant Chronic Myelomonocytic Leukemia
Authors: McCullough Kristen B. , Xie Zhuoer , Lasho Terra L. , Finke Christy , Fernandez Jenna A. , Amundson Michelle Renee , LaPlant Betsy R. , Witzig Thomas E. , Patnaik Mrinal M. 
Published: December 2024

Background: Chronic myelomonocytic leukemia (CMML) is a myelodysplastic/myeloproliferative overlap neoplasm (MDS/MPN), further categorized as MD (WBC &lt; 13 x 109/L) and MP (≥ 13 x 109/L) subtypes with an inherent risk for AML transformation (Am J Hematol 2024; 99: 1142). Hypomethylating agents (HMA), decitabine (DAC) and azacitidine, are the only FDA approved agents for the management of CMML, with complete remission rates of &lt;20%, and a recent prospective study showing no event free survival benefit of DAC over hydroxyurea in MP-CMML (J Clin Oncol 2023; 41: 1888). TET2 mutations (TET2MT) occur in approximately 60% of CMML cases. TET2 converts 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), resulting in DNA demethylation (Nat Rev Gen 2017; 18: 517). IV ascorbic acid (AA) at pharmacologic concentrations demonstrates anti-cancer activity via H2O2-induced oxidative stress and DNA demethylation mediated by TET-activation. AA, a cofactor of TET2, binds to its catalytic domain, restores, and enhances TET1/2/3 activity. Given the synergistic impact of IV AA and HMA on DNA methylation, we designed a phase II clinical trial testing the safety and efficacy of standard dose decitabine and high dose IV AA in HMA-naïve CMML patients.

Methods: LS1781 (NCT03418038) is an investigator-initiated, prospective, single-arm, single-institution, phase II trial assessing the safety and preliminary efficacy of high-dose IV AA in combination with DAC for patients with TET2MT CMML. DAC 20 mg/m2 Days 1-5 of each 28-day cycle is given as standard of care. With each cycle, IV AA (1g/kg, maximum 100g) is given 3 times on Days 1, 3, 5 via central line within 2 hours after DAC. Patients are encouraged to take oral AA 1000 mg once daily on non-treatment days. The primary endpoint is overall response rate determined by IWG MDS/MPN 2015 criteria after 4 cycles of therapy. Secondary endpoints include safety and side effects. Exploratory endpoints include the impact of AA on TET2MT variant allele fraction, plasma cytokine levels, DNA methylation and hydroxymethylation (as measured by Infinium MethylationEPIC array), and hematopoietic progenitor colony forming assay assessment (colony counts and impact on differentiation). Inclusion criteria include patients ≥ 18 years with TET2MT CMML, ≤1 cycle of HMA or ESA (hydroxyurea allowed), platelets ≥ 20,000/m3, ANC ≥ 500/mm3, and Cockcroft-Gault creatinine clearance ≥ 60 mL/min/m2. Twenty-three patients will be enrolled at Mayo Clinic Rochester and the Mayo Clinic Health System, based on power calculations to demonstrate enhanced complete response and overall response rates, in comparison to those seen historically with decitabine alone. Dose modifications have been established and will be considered based on adverse events. Treatment will be discontinued for disease progression or in the event of ≥ Grade 3 adverse events that do not resolve promptly. After completion of up to 12 cycles, patients with stable disease or better may continue single agent DAC with or without oral AA. Enrollment to the trial began in February 2024, with 2 patients enrolled at the time of abstract submission.