LentiGlobin gene therapy for sickle cell disease results in complete elimination of SCD-related severe vaso-occlusive events in Group C of phase 1/II HGB-206 clinical study .- bluebird bio Inc.

bluebird bio, Inc. announced that new data from Group C of its ongoing Phase 1/II HGB-206 study of investigational LentiGlobin gene therapy (bb 1111) for adult and adolescent patients with sickle cell disease (SCD) show a complete elimination of severe VOEs (vaso-occlusive events) and VOEs between six and 24 months of follow-up. These data are being presented at the 62nd American Society of Hematology (ASH) Annual Meeting and Exposition, taking place virtually from December 5-8, 2020. In the HGB-206 study of LentiGlobin for SCD , VOEs are defined as episodes of acute pain with no medically determined cause other than a vaso-occlusion, lasting more than two hours and severe enough to require care at a medical facility. This includes acute episodes of pain, acute chest syndrome (ACS), acute hepatic sequestration and acute splenic sequestration. A severe VOE requires a 24-hour hospital stay or emergency room visit or at least two visits to a hospital or emergency room over a 72-hour period, with both visits requiring intravenous treatment. LentiGlobin for SCD was designed to add functional copies of a modified form of the beta-globin gene (betaA-T87Q-globin gene) into a patient’s own hematopoietic (blood) stem cells (HSCs). Once patients have the betaA-T87Q-globin gene, their red blood cells can produce anti-sickling hemoglobin (HbAT87Q) that decreases the proportion of HbS, with the goal of reducing sickled red blood cells, hemolysis and other complications. As of the data cut-off date of August 20, 2020, a total of 44 patients have been treated with LentiGlobin for SCD in the HGB-205 (n=3) and HGB-206 (n=41) clinical studies. The HGB-206 total includes: Groups A (n=7), B (n=2) and C (n=32). HGB-206: Group C Updated Efficacy Results : The 32 patients treated with LentiGlobin for SCD gene therapy in Group C of HGB-206 had up to 30.9 months of follow-up (median of 13.0; min-max: 1.1 – 30.9 months). In patients with six or more months of follow-up whose hemoglobin fractions were available (n=22), median levels of gene therapy-derived anti-sickling hemoglobin, HbAT87Q, were maintained with HbAT87Q contributing at least 40% of total hemoglobin at Month 6. At last visit reported, total hemoglobin ranged from 9.6 – 15.1 g/dL and HbAT87Q levels ranged from 2.7 – 8.9 g/dL. At Month 6, the production of HbAT87Q was associated with a reduction in the proportion of HbS in total hemoglobin; median HbS was 50% and remained less than 60% at all follow-up timepoints. All patients in Group C were able to stop regular blood transfusions by three months post-treatment and remain off transfusions as of the data cut-off. Nineteen patients treated in Group C had a history of severe VOEs, defined as at least four severe VOEs in the 24 months prior to informed consent (annualized rate of severe VOE min-max: 2.0 – 10.5 events) and at least six months follow-up after treatment with LentiGlobin for SCD. There have been no reports of severe VOEs in these Group C patients following treatment with LentiGlobin for SCD. In addition, all 19 patients had a complete resolution of VOEs after Month 6. Hemolysis Markers : In SCD, red blood cells become sickled and fragile, rupturing more easily than healthy red blood cells. The breakdown of red blood cells, called hemolysis, occurs normally in the body. However, in sickle cell disease, hemolysis happens too quickly due to the fragility of the red blood cells, which results in hemolytic anemia. Patients treated with LentiGlobin for SCD in Group C demonstrated near-normal levels in key markers of hemolysis, which are indicators of the health of red blood cells. Lab results assessing these indicators were available for the majority of the 25 patients with 6 months of follow-up. The medians for reticulocyte counts (n=23), lactate dehydrogenase (LDH) levels (n=21) and total bilirubin (n=24) continued to improve compared to screening values and stabilized by Month 6. In patients with Month 24 data (n=7), these values approached the upper limit of normal by Month 24. These results continue to suggest that treatment with LentiGlobin for SCD may improve biological markers to near-normal levels for SCD. Pancellularity : As previously reported, assays were developed by bluebird bio to enable the detection of HbAT87Q and HbS protein in individual red blood cells, as well as to assess if HbAT87Q was pancellular, or present throughout all of a patient’s red blood cells. In 25 patients with at least six months of follow-up, on average, more than 80% of red blood cells contained HbAT87Q, suggesting near-complete pancellularity of HbAT87Q distribution and with pancellularity further increasing over time. HGB-206: Improvements in Health-Related Quality of Life : Health-related quality of life (HRQoL) findings in Group C patients treated with LentiGlobin for SCD in the HGB-206 study were generated using the Patient Reported Outcomes Measurement Information System 57 (PROMIS-57), a validated instrument in SCD. Data assessing pain intensity experienced by nine Group C patients were analyzed according to baseline pain intensity scores relative to the general population normative value: 2.6 on a scale of 0-10, where 10 equals the most intense pain. Data were assessed at baseline, Month 6 and Month 12. Of the five patients with baseline scores worse than the population normative value average, four demonstrated clinically meaningful reductions in pain intensity at Month 12; the group had a mean score of 6.0 at baseline and a mean score of 2.4 at Month 12. Of the four patients with better than or near population normative values at baseline, two reported improvement and two remained stable with a mean score of 2.3 at baseline and 0.8 at Month 12. HGB-206: Group C Safety Results : As of August 20, 2020, the safety data from Group C patients in HGB-206 remain generally consistent with the known side effects of hematopoietic stem cell collection and myeloablative single-agent busulfan conditioning, as well as underlying SCD. One non-serious, Grade 2 adverse event (AE) of febrile neutropenia was considered related to LentiGlobin for SCD. There were no serious AEs related to LentiGlobin for SCD. One patient with significant baseline SCD-related and cardiopulmonary disease died 20 months post-treatment; the treating physician and an independent monitoring committee agreed his death was unlikely related to LentiGlobin for SCD and that SCD-related cardiac and pulmonary disease contributed. LentiGlobin for SCD Data at ASH : The presentation of HGB-206 Group C results and patient reported outcomes research are now available on demand on the ASH conference website: Oral #677: Resolution of Serious Vaso-occlusive Pain Crises and Reduction in Patient-Reported Pain Intensity: Results from the Ongoing Phase 1/2 HGB-206 Group C Study of LentiGlobin for Sickle Cell Disease (bb1111) Gene Therapy Oral #365: Improvements in Health-Related Quality of Life for Patients Treated with LentiGlobin for Sickle Cell Disease (bb1111) Gene Therapy.