Phase 1 Study of a Sulforaphane-Containing Broccoli Sprout Homogenate for Sickle Cell Disease

Abstract

Sickle cell disease (SCD) is the most common inherited hemoglobinopathy worldwide. Our previous results indicate that the reduced oxidative stress capacity of sickle erythrocytes may be caused by decreased expression of NRF2 (Nuclear factor (erythroid-derived 2)-like 2), an oxidative stress regulator. We found that activation of NRF2 with sulforaphane (SFN) in erythroid progenitors significantly increased the expression of NRF2 targets HMOX1, NQO1, and HBG1 (subunit of fetal hemoglobin) in a dose-dependent manner. Therefore, we hypothesized that NRF2 activation with SFN may offer therapeutic benefits for SCD patients by restoring oxidative capacity and increasing fetal hemoglobin concentration. To test this hypothesis, we performed a Phase 1, open-label, dose-escalation study of SFN, contained in a broccoli sprout homogenate (BSH) that naturally contains SFN, in adults with SCD. The primary and secondary study endpoints were safety and physiological response to NRF2 activation, respectively. We found that BSH was well tolerated, and the few adverse events that occurred during the trial were not likely related to BSH consumption. We observed an increase in the mean relative whole blood mRNA levels for the NRF2 target HMOX1 (p = 0.02) on the last day of BSH treatment, compared to pre-treatment. We also observed a trend toward increased mean relative mRNA levels of the NRF2 target HBG1 (p = 0.10) from baseline to end of treatment, but without significant changes in HbF protein. We conclude that BSH, in the provided doses, is safe in stable SCD patients and may induce changes in gene expression levels. We therefore propose investigation of more potent NRF2 inducers, which may elicit more robust physiological changes and offer clinical benefits to SCD patients. Trial registration: ClinicalTrials.gov NCT01715480.

Fig 1. CONSORT flow diagram enrollment summary

Fig 2. Treatment of erythroid progenitors with sulforaphane induces NRF2 target expression.

Relative mRNA expression of in vitro differentiating erythroid progenitors 48 hours after beginning treatment, relative to untreated for A) NQO1, B) HMOX1, and C) HBG1/(HBB+HBG1) (n = 3). Cells were treated starting on Day 8 of differentiation, and were treated once every 24 hours, with a total of two treatments for the listed concentration. TBHQ was used as a positive control. All expression was set relative to pre-treatment values, was normalized with GAPDH, and all statistical analyses were performed using an unpaired t-test (* = p<0.05, ** = p<0.01, *** = p<0.001).

Fig 3. Effect of BSH ingestion on whole blood mRNA in SCD subjects.

The composite of the mean for relative mRNA expression of A) NQO1, B) HMOX1, and C) HBG1/(HBB+HBG1) for all patients during the study period. All expression was set relative to pre-treatment values. Expression was normalized with GAPDH, and all statistical analyses were performed using Friedman’s test (* = p<0.05).

Fig 4. Fetal hemoglobin levels during study period.

Fetal hemoglobin levels were assessed with hemoglobin electrophoresis for the A) 50g, B) 100g, and C) 150g cohorts. Each individual patient is designated with letter, symbol, and color codes; several patients participated in multiple cohorts. Patient F was diagnosed with HbSß° thalassemia; all other patients were diagnosed with HbSS. Patients taking hydroxyurea during the study period are denoted with an asterisk.