A Study Evaluating the Efficacy and Safety of the LentiGlobin® BB305 Drug Product in Participants With Transfusion-Dependent β-Thalassemia

TI was defined as a weighted average hemoglobin (Hb) >= 9 grams per deciliter (g/dL) without any packed red blood cell (pRBC) transfusions for a continuous period of >= 12 months at any time during the study after drug product infusion.

Duration of TI was calculated as the time from the start of TI (i.e. first Hb >=9 with no transfusions in the preceding 60 days) up to the last available Hb at which the TI criteria are still met using Kaplan-Meier methodology.

Time from drug product infusion to achievement of TI was calculated as the time from drug product infusion to the first hemoglobin at which a participant can be declared as TI (that is to 'start of TI + >= 12 months', dependent on Hb lab schedule).

Weighted average Hb was defined as the weighted average of Hb values without any pRBC transfusions in the proceeding 60 days for a given subject. Ratio of the time between two Hb values and the time between the first and the last Hb values was used as the weight for calculation.

TR was defined as demonstration of a 60 percent (%) reduction in the annualized volume of pRBC transfusion requirements (in milliliter per kilogram [mL/kg]) in the post-treatment time period from 12 Months post-drug product infusion through Month 24 compared to the annualized mL/kg pRBC transfusion requirement during the 24 months prior to study enrollment.

Percentage of participants with a reduction in the annualized mL/kg pRBCs transfused from 12 months post-drug product infusion through Month 24 (approximately a 12-month period) of at least 50%, 60%, 75%, 90% or 100% compared to the annualized mL/kg pRBC transfusion requirement during the 24 months prior to enrollment.

Annualized number of pRBC transfusions from 12 months post-drug product infusion through Month 24 was reported.

Annualized volume of pRBC transfusions from 12 months post-drug product infusion through Month 24 compared to the annualized volume of transfusions during the 24 months prior to enrollment.

Time from drug product infusion to last pRBC transfusion was reported.

Time From Last pRBC Transfusion to the Month 24 was reported.

The weighted average nadir Hb was defined as the most recent Hb prior to each pRBC transfusion, on the day of transfusion or within 3 days and, if there was a period of more than 60 days without transfusion, all Hb records between Day 61 and last follow-up or next transfusion (inclusive) was included. The weighted average nadir Hb during the period of 12 months post-drug product infusion to Month 24 was compared to the weighted average nadir Hb during the 24 months prior to enrollment.

Unsupported total Hb level was defined as the total Hb measurement level without any acute or chronic pRBC transfusions within 60 days prior to the measurement date.

Number of participants with unsupported total Hb levels (>=10 g/dL, >=11 g/dL, >=12 g/dL, >=13 g/dL, and >=14 g/dL) meeting the thresholds were reported at Months 6, 9, 12, 18 and 24. Participants were evaluable if they had an unsupported total Hb measurement at the specific timepoint, where unsupported total Hb level is defined as the total Hb measurement level without any acute or chronic pRBC transfusions within 60 days prior to the measurement date.

Percentage of participants who have not received chelation therapy for at least 6 months following drug product infusion were reported.

Time from last iron chelation use to last follow-up to 24 months was reported.

Therapeutic phlebotomy could be used in lieu of chelation in participants who had Hb consistently >= 11 g/dL and who were no longer receiving regular transfusions, at the discretion of the investigator. Number of participants who used therapeutic phlebotomy post Drug Product infusion for up to Month 24 were reported.

Annualized phlebotomy therapy usage (number of procedures per year, calculated from DP infusion through last follow-up) were reported.

Change From Baseline in Liver Iron Content by MRI at Months 12 and 24 were reported. Baseline is defined as value closest to but prior to conditioning.

Change From Baseline in Cardiac T2* on MRI from Baseline, Month 12 and 24 was reported.

Serum ferritin was commonly used for an indirect estimation of body iron stores. Although sensitive, it is not specific for iron overload as it can be elevated in a variety of infectious and inflammatory states, and in the presence of cytolysis. Change from baseline in serum ferritin at Months 12 and 24 was reported.

PedsQL GCS designed to measure health-related quality of life in pediatric and adolescents (2-18 years). It encompassed 4 dimensions of functioning (physical [8 items], emotional [5 items], social [5 items], school [3 items]). Age groups: Toddler (2-4 years), Young pediatric (5-7 years), Pediatric (8-12 years), Teens (13-18 years). The questionnaire was also completed by parent/caregiver to assess parents' perceptions of their children's quality of life. The Toddler group consisted of 21 items, using a 5-point Likert scale (0 to 4); all other groups consisted of 23 items, with a 3-point Likert scale (0, 2, 4) for young pediatric, a 5-point Likert scale for pediatric and teens groups. All reported scores were transformed on a scale from 0 to 100 for each domain where 0=100, 1=75, 2=50, 3=25, and 4=0. Higher scores correspond with higher quality of life.

EQ-5D is a validated, standardized, generic instrument that was most widely used preference based health related quality of life questionnaire in cost effectiveness and health technologies assessment. EQ-5D-Y was a version of instrument specifically developed and validated for use by youths aged 12 through 17 years. The EQ-5D-Y visual analog scale (VAS) consisted of a 20-cm vertical VAS, with anchors of 0 (worst imaginable health state) and 100 (best imaginable health state). Respondents were asked to rate their own health state today by drawing a line from a box containing these words to the point on the scale that they felt most accurately reflected their current health state. The VAS was reported (raw data) on a scale of 0-100 where 0= death and 100= perfect health. Higher scores corresponded with higher quality of life.

EQ-5D is a validated, standardized, generic instrument that was most widely used preference based health related quality of life (HRQoL) questionnaire in cost effectiveness and health technologies assessment. Participants age >=18 at time of informed consent were eligible to complete the EQ-5D-3L visual analog scale (VAS) which consisted of a 20-cm vertical VAS, with anchors of 0 (worst imaginable health state) and 100 (best imaginable health state). Respondents were asked to rate their own health state today by drawing a line from a box containing these words to the point on the scale that they felt most accurately reflected their current health state. The VAS was reported (raw data) on a scale of 0-100 where 0= death and 100= perfect health. Negative change in score indicated decrease in quality of life (as measured by EQ5D VAS) from baseline.

FACT-BMT is assessed bone marrow transplant related quality of life in adults. Total score was sum of sub-scale scores for 5 domains: Physical Well-Being, Social/Family Well-Being, Emotional Well-Being, Functional Well-Being, and Bone Marrow Transplantation Subscale. Each item scored on a 5-point Likert scale based on participant agreement with each statement: 0 for "not at all," 1 for "a little bit," 2 for "somewhat," 3 for "quite a bit," and 4 for "very much. Reported scores were transformed as follows: After taking into account reverse scores for questions constructed in negative form, subscale score for each domain was calculated by multiplying sum of item scores by number of items in subscale, then dividing by number of items answered. Total score was sum of subscale total added together and ranges from 0-148. Higher scores corresponded with higher quality of life.

SF-36 was designed to measure health-related quality of life in adults. The instrument consisted of 36 items that were aggregated into 8 multi-item scales (physical functioning [1=yes, limited a lot, to 3=no, not limited at all], role-physical [1=all of time, to 5=none of time], bodily pain [1=very severe, to 6=none], general health [1=poor, to 5=excellent], vitality [1=none of time, to 5=all of time], social functioning [1=all of time, to 5=none of time], role emotional [1=all of time, to 5=none of time] and mental health [1=all of time, to 5=none of the time]). The 8 scales were summarized as Physical Component Summary (PCS) score (physical functioning, role-physical, bodily pain, general health scales) and Mental Component Summary (MCS) score (vitality, social functioning, role-emotional, mental health scales). Reported summary scores were transformed on a scale from 0-100 (higher scores corresponded with higher quality of life), with change from baseline results being presented.