Benserazide As a Novel Fetal Hemoglobin Inducer: An Observational Study in Non-Carriers of Hemoglobin Disorders

Induction of fetal hemoglobin (HbF) production is an effective therapeutic strategy in the management of patients with beta hemoglobinopathies. Hydroxyurea is the only drug with this mechanism approved for clinical use, and 20% or more of patients do not respond or tolerate it, which has led to the search for new HbF inducers. Benserazide (BEN) is a DOPA decarboxylase inhibitor used in combination with levodopa in the treatment of parkinsonism, but it was also noticed to induce increased gamma globin production in preclinical models. The mechanisms by which BEN acts include downregulation of BCL11A, LSD1 and HDAC3 on the promoter region of the gamma globin gene, making it an interesting candidate for clinical studies in hemoglobinopathies. We hypothesized that patients undergoing treatment for parkinsonism with chronic use of BEN-containing medication may develop increase in HbF production and in circulating F-cells. Material and Methods: Peripheral blood samples were collected from patients with parkinsonism during their follow-up at the Neurology Clinic, who had been using BEN for at least 30 days (BEN group), from healthy controls (group AA), and from patients known to have increased of HbF due to sickle cell anemia (group SS), for comparison purposes. Exclusion criteria for BEN and AA groups were: any hemoglobinopathy, transfusion in the last 90 days, and use of HU or any chemotherapeutic agent. Automated complete blood counts with reticulocyte count were performed on a XN-3000 equipment (Sysmex, Japan), HbF levels were determined by HPLC (BioRad, USA), and F-cell percentage was determined by flow cytometry (BD FACSCalibur, USA). Results: Thirty-five patients on BEN, 10 negative controls (AA group) and five positive controls (SS group) were included. One patient taking BEN was excluded due to HPLC compatible with beta thalassemia trait. Patients taking BEN had blood counts within the normal range. There was no statistically significant difference between BEN and AA groups, and the SS group was significantly anemic as expected. We found a strongly positive correlation between HbF and circulating F-cells (p <0.0001, r = 0.946) when analyzing the entire population, but within the subgroup of patients using BEN, this correlation was much weaker (p = 0.0032, r = 0.492). Dose range of BEN used by the patients was 100-700mg daily, at 1.21 to 11.1mg/kg/day, but we found no correlation between dose and HbF levels. Discussion: We found no differences in blood counts, and extensive use of this regimen support that chronic use of BEN is safe in doses up to 11.1mg/kg/day. In vitro studies suggest that BEN is 30 times more potent than HU. Therefore, considering the minimum dose of HU used in clinical practice of 15mg/kg/day, we had expected that some increase in HbF could be observed at 0.5mg/kg/day of BEN. However, our data show that, even with chronic use of doses 20 times higher, there was no increase in HbF or F-cell levels. The lack of effectiveness of BEN in this population may be explained by its hydrolysis in the intestinal mucosa, and by its reported short half-life (48min), which could account for reduced bioavailability. In addition, patients not bearing beta globin mutations may be less likely to respond to gamma globin induction. Conclusion: Although BEN is already in clinical use and is a strong candidate as a new HbF inducer, we did not detect this effect in humans without hemoglobinopathies. Our data impact the experimental design of future clinical trials with BEN, and suggests the need for more studies on its pharmacokinetics and pharmacodynamics to improve the chances of achieving the desired clinical effect.