Improvements in Health-Related Quality of Life after Exagamglogene Autotemcel in Patients with Transfusion-Dependent Beta-Thalassemia

Background: Transfusion-dependent β-thalassemia (TDT), an inherited hematological disorder which requires life-long, chronic red blood cell transfusion (RBC) and regular iron chelation therapy, has a substantial negative impact on health-related qualify of life (HRQoL). Exagamglogene autotemcel (exa-cel) is a one-time, non-viral, ex vivo CRISPR-Cas9 gene-edited cell therapy in phase 3 clinical trials that has been shown to eliminate the need for RBC transfusions and achieve transfusion independence. Here, we report HRQoL data from a pre-specified interim analysis of the exa-cel CLIMB TDT-111 study.

Methods: CLIMB TDT-111 is an ongoing, 24-mo, phase 3 trial of a single dose of exa-cel in patients aged 12-35 years with TDT and a history of ≥100 mL/kg/year or ≥10 U/year of packed RBC transfusions for 2 years prior to screening. Changes in patient-reported outcome (PRO) measures including EuroQol Quality of Life Scale 5 dimensions 5 levels of severity (EQ-5D-5L, including descriptive system and visual analog scale [VAS]) and Functional Assessment of Cancer Therapy Bone Marrow Transplant (FACT-BMT, including FACT-General [FACT-G] and bone marrow transplant subscale [BMTS]) for adults and the EuroQol Quality of Life Scale 5 dimensions youth (EQ-5D-Y) and Pediatric Quality of Life Inventory (PedsQL) for adolescents were assessed through month 24 as a secondary endpoint in the trial. Data are presented as of 16 January 2023 for the 24 adults (aged ≥18-35 years) and 11 adolescents (aged ≥12 to < 18 years) who had been followed for ≥16 months after exa-cel infusion.

Results: Clinically meaningful improvements, exceeding the minimal clinically important difference (MCID) thresholds, were observed in all PRO measures in adults. Baseline mean EQ-5D-5L health utility US index score (n=24, mean [SD]: 0.85 [0.18]) was near the general population norm and in line with baseline scores previously reported for adult patients with TDT. By month 24, both EQ-5D-5L health utility US index scores and EQ VAS scores showed substantial improvement (mean [SD] changes at month 24 [n=15]: 0.12 [0.26] and 10.2 [20.9] points; MCIDs 0.078 and 7 to 10, respectively). FACT-G Total Score improved from baseline by month 12 and was sustained through month 24 (mean [SD] change at month 24 [n=15] 10.3 [17.0] points; MCID 3 to 7), with improvements observed in all 4 subscales (physical, social/family, emotional, and functional well-being). BMTS score improved by month 12 and was sustained through month 24 (mean [SD] change at month 24 [n=15] 6.8 [4.7] points; MCID 2 to 3).

For adolescents, EQ VAS scores improved through month 18 (mean [SD] change from baseline 4.8 [6.1] points). Total PedsQL score improved by month 6 and was sustained through month 18 (mean [SD] change from baseline [n=7] 14.1 [9.2] points; MCID 4.36). Physical functioning and psychosocial health scores, sub-components of PedsQL, both showed sustained improvement through month 18 (mean [SD] change [n=7] 19.2 [9.1] and 11.4 [10.9] points; MCID of 6.66 and 5.30 points, respectively). Improvement in psychosocial score was observed in all 3 subscales (social, emotional, and school functioning).

Conclusion: Adults and adolescents infused with exa-cel reported sustained and clinically meaningful improvements in their HRQoL, with improvements observed across different instruments and domains, including physical, emotional, social/family and functional well-being and overall health status. These results demonstrate the broad clinical benefits of exa-cel in patients with TDT.