Infrequent Resolution of Vaso-Occlusive Crises in Routine Clinical Care Among Patients Mimicking the Exa-Cel Trial Population: A Cohort Study of Medicaid Enrollees

The CRISPR-based gene editing therapy exagamglogene autotemcel (exa-cel) recently received FDA approval for patients with severe sickle cell disease (SCD). The approval was based on a phase III trial (CLIMB SCD 121), which showed 97% efficacy of this treatment in eliminating vaso occlusive crises (VOCs) for 12 consecutive months. To help contextualize results from this trial, we aimed to investigate the proportion of patients with severe SCD who remain VOC-free for a 1-year period in routine clinical care. Using Medicaid claims data (2000-2018), we identified a cohort of patients, 12-35 years old with severe SCD, defined by ≥ 2 VOCs per year for 2 consecutive years, who met other exa-cel trial inclusion criteria to mimic a trial-like population. A VOC was identified using ICD diagnosis codes during hospitalization and ER visits. The primary outcome was the proportion of patients with no VOCs during a 1-year follow-up. A total of 7,425 patients with severe SCD [mean (SD) age: 20.5 (6.0) years, 54.6% females, 84% African Americans], had a mean of 5.2 VOCs, 5.1 ER visits and 3.5 hospitalizations per year during the baseline period. The proportion of patients with no VOCs during the 1-year follow-up was 7.7% (95% confidence interval: 7.1%-8.3%). In conclusion, less than one in 12 patients with severe SCD achieved VOC-free status within 1 year in routine clinical care. These findings suggest that the high efficacy observed for exa-cel in the trial, if replicated in routine clinical care, could translate into a significant public health impact.