Efficacy, Safety, and Health-Related Quality of Life (HRQOL) in Patients with Sickle Cell Disease (SCD) Who Have Received Lovotibeglogene Autotemcel (Lovo-cel) Gene Therapy: Up to 60 Months of Follow-up

Introduction: Lovo-cel gene therapy uses autologous transplantation of hematopoietic stem and progenitor cells (HSPC) transduced with the BB305 lentiviral vector encoding a modified β-globin gene, which produces an anti-sickling hemoglobin (Hb), HbA ^T87Q. The phase 1/2 HGB-206 (NCT02140554) and phase 3 HGB-210 (NCT04293185) studies of lovo-cel are the largest clinical trials of gene therapy in SCD to date. We report efficacy and safety from these studies, including the first data from adult and pediatric patients (age 12 to <18 years) in HGB-210, and HRQOL data from HGB-206.

Methods: This analysis includes patients from HGB-206 Group C and HGB-210 who received lovo-cel using the current HSPC mobilization and manufacturing process. Patients with SCD and recurrent severe vaso-occlusive events (VOEs) or history of overt stroke underwent plerixafor mobilization and apheresis followed by myeloablative busulfan conditioning and lovo-cel infusion. After 24 months of follow-up post lovo-cel infusion, patients enrolled in the long-term study LTF-307 (NCT04628585). Lab evaluations, SCD-related outcomes (eg, resolution of VOEs), globin response (a composite endpoint evaluating HbA ^T87Q percentage and total Hb), and safety are reported up to 60 months. An independent Event Adjudication Committee confirmed VOEs met protocol criteria. HRQOL data from Patient-Reported Outcomes Measurement Information System (PROMIS)-57 domains of pain interference, fatigue, and pain intensity are reported up to 48 months.

Results:This analysis includes47 patients (HGB-206 Group C, n=36; HGB-210, n=11; male, 59.6%; median [range] age, 23 y [12-38]) who received a lovo-cel infusion as of Feb 13, 2023. Median (range) follow-up was 35.5 months (0.3-61.0). Median (range) time to neutrophil and platelet engraftment was 20 days (12-35) and 35 days (19-136). Peripheral blood vector copy number remained stable (median >1 c/dg through follow-up). Median HbA ^T87Q levels were ≥4.5 g/dL from 6 months post infusion to last study visit. Median (range) total Hb level increased from 8.7 g/dL (6.1-12.5) at relative baseline to 11.8 g/dL (8.4-15.0) at last visit; median percent HbA ^T87Q of nontransfused total Hb was ≈40% or more ( Figure).

Of 33 evaluable patients (ie, ≥18 months follow-up and ≥4 VOEs in the 2 years before enrollment), 30 (90.9%) and 32 (97.0%) had complete resolution of VOEs and severe VOEs during the 6-18 months post infusion, vs a median (range) of 3.5 (1.5-16.5) and 3.0 (0.5-13.0) events/year in the 2 years before enrollment. Additional efficacy analyses in subgroups (eg, stroke history, α-globin genotype) will be presented.

Among patients who had globin response or who had ≥18 months follow-up (n=38), 33 (86.8%) achieved globin response. Hemolysis markers (eg, reticulocytes, total bilirubin, lactate dehydrogenase) approached normal levels.

Among all 47 patients, 44 (93.6%) had ≥1 AE of grade ≥3 after lovo-cel infusion; the most common of which were stomatitis (33 [70.2%] patients) and thrombocytopenia (28 [59.6%]). Serious AEs were reported for 26 (55.3%) patients, the most common of which was chronic pain/acute exacerbation of chronic pain (3 [6.4%]; 2 chronic neuropathic pain and 1 chronic pain associated with anxiety). One patient with -α3.7/-α3.7 genotype was diagnosed with myelodysplastic syndrome with stable complete blood counts 30 months post infusion; updated data to be presented. No veno-occlusive liver disease, graft failure, replication-competent lentivirus, or vector-mediated insertional oncogenesis was observed. Lovo-cel treatment regimen largely reflected known side effects of HSPC collection and busulfan conditioning regimen.

A total of 25 patients (all from HGB-206 Group C; age ≥18 y) had evaluable HRQOL data. Mean scores for PROMIS-57 domains of pain intensity, pain interference, and fatigue improved (ie, decreased) over time up to 48 months ( Table).

Conclusion: One-time treatment with lovo-cel resulted in sustained HbA ^T87Q production and near-complete resolution of VOEs and severe VOEs up to 18 months post treatment; the safety profile was consistent with underlying SCD and myeloablative conditioning. Patients reported sustained improvements in pain intensity, pain interference, and fatigue. Ongoing long-term follow-up will continue to provide important information on efficacy, safety, and patient experience post lovo-cel treatment.