Trial Outcomes & Findings for Haploidentical Bone Marrow Transplantation in Sickle Cell Patients (BMTCTN1507) (NCT NCT03263559)

BMT CTN 1507's enrollment was between October 10, 2017 and October 19, 2022 with 36 participating centers in the United States of America. 95 participants enrolled from 28 centers (18 centers enrolled adults and 17 enrolled pediatrics). Of 95 participants, 54 participants enrolled in the adult stratum, and 41 enrolled in the pediatric stratum. The accrual goal was 40 transplanted participants in each age strata. The study was completed on January 29, 2025.

Participants were enrolled in two age strata: Adults (15.00 - 45.99 years at enrollment) or Pediatrics (5.00 - 14.99 years at enrollment with two approved exceptions). This is an open-label, single arm study in which all enrolled participants were intended to undergo haploidentical bone marrow transplantation (BMT). Of 54 adult and 41 pediatric enrolled participants, 42 and 39 were transplanted, respectively. For various reasons, a small portion of participants did not receive a transplant.

Sickle cell disease types are designated by the types of mutations in hemoglobin. The most common type of sickle cell disease has two copies of hemoglobin S (Hemoglobin SS Disease), but other mutations such a C, beta thalassemia, or OArab can pair with S to yield Hemoglobin SC, Hemoglobin SBeta0 Thalassemia, Hemoglobin SBeta+ Thalassemia, or Hemoglobin S-OArab.

EFS is defined as survival without a qualifying event from transplant. Primary graft failure (PGF), secondary graft failure (SGF), second infusion of hematopoietic cells, or death from any cause will count as events for this endpoint. This endpoint was adjudicated by an Endpoint Review Committee. PGF is lack of engraftment on or before Day 42 post-transplant. Engraftment is defined as having greater than or equal to 5% donor cells post-transplant, from any molecular chimerism assessment (e.g., unsorted, myeloid, or T-cell) on a peripheral blood or bone marrow aspirate sample. SGF is defined as \< 5% donor whole blood or myeloid chimerism in peripheral blood or bone marrow beyond day +42 post-transplant in patients with prior documentation of hematopoietic recovery with \>5% donor cells by day +42 post-transplant. Infusion of a second stem cell product will be considered graft rejection, and counted toward primary or, depending on timing of the second infusion, secondary graft rejection

Death from any cause will be the event and patients will be censored at the date of last contact or two years post-transplant, whichever comes first.

Primary Graft Failure (PGF) is lack of engraftment on or before Day 42 post-transplant. Engraftment is defined as having greater than or equal to 5% donor cells post-transplant, from any molecular chimerism assessment (e.g., unsorted, myeloid, or T-cell) on a peripheral blood or bone marrow aspirate sample. Secondary Graft Failure (SGF) is defined as \< 5% donor whole blood or myeloid chimerism in peripheral blood or bone marrow beyond day +42 post-transplant in patients with prior documentation of hematopoietic recovery with \>5% donor cells by day +42 post-transplant. Infusion of a second stem cell product will be considered graft rejection, and counted toward primary or, depending on timing of the second infusion, secondary graft rejection.

Disease Recurrence is defined as primary graft failure, secondary graft failure, or sickle hemoglobin (HbS) \> 70% within 2 years post-transplant. Cumulative Incidence of Disease Recurrence was estimated with a 95% confidence interval using the Aalen-Johansen estimator with death prior to disease recurrence treated as a competing risk. This endpoint was adjudicated by an Endpoint Review Committee.

Neutrophil recovery is defined as the first of 3 measurements on different days when the patient has an absolute neutrophil count of ≥500/μL after conditioning. The incidence of neutrophil recovery from transplant will be estimated using the cumulative incidence function with a 95% confidence interval using the Aalen-Johansen estimator with death or second transplant without neutrophil recovery as a competing risk.

Platelet recovery is defined as the first day of a minimum of 3 measurements on different days that the patient has achieved a platelet count \> 50,000/μL AND did not receive a platelet transfusion in the previous 7 days. The incidence of platelet recovery from transplant will be estimated using the cumulative incidence function with a 95% confidence interval using the Aalen-Johansen estimator with death or second transplant without platelet recovery as a competing risk.

A point estimate and confidence interval will be provided for the mean percent donor chimerism at the time points specified including Day 28, Day 100, Day 180, 1 year, and 2 years post-transplant. For each participant's visit with multiple chimerism sources recorded, donor percentage is determined by taking the first non-missing chimerism percentage in the following order of sources: marrow, blood, myeloid, and t-cell.

At Day 28, Day 100, Day 180, 1 year and 2 years post-transplant, the proportions with low chimerism (\<5%), mixed chimerism (5-95%), or full chimerism (\>95%) will be tabulated and described. For each participant's visit with multiple chimerism sources recorded, donor percentage is determined by taking the first non-missing chimerism percentage in the following order of sources: marrow, blood, myeloid, and t-cell.

Acute GVHD was graded according to Consensus Criteria with higher grade indicating worse outcomes. Grade I aGVHD is defined as stage 1-2 skin rash and no liver or GI involvement. Grade II is stage 3 skin rash, or stage 1 liver involvement, or stage 1 GI involvement. Grade III is stage 0-3 skin rash, with stage 2-3 liver involvement, or stage 2-3 GI involvement. Grade IV is stage 4 skin rash, liver, or GI involvement. Maximum grade is defined as the maximum grade of acute GVHD (0-IV) that a participant experiences by Day 100 post-transplant.

Acute GVHD was graded according to Consensus Criteria with higher grade indicating worse outcomes. Grade I aGVHD is defined as stage 1-2 skin rash and no liver or GI involvement. Grade II is stage 3 skin rash, or stage 1 liver involvement, or stage 1 GI involvement. Grade III is stage 0-3 skin rash, with stage 2-3 liver involvement, or stage 2-3 GI involvement. Grade IV is stage 4 skin rash, liver, or GI involvement. The cumulative incidence of acute GVHD grade II-IV and III-IV at Day 100 was estimated using the Aalen-Johansen estimator with 95% confidence intervals, treating death prior to aGVHD as a competing event. Time to aGVHD is defined as time from transplant until onset of grades II-IV and III-IV aGVHD, respectively.

Chronic GVHD is based on NIH Consensus Criteria (2014 NIH Consensus Criteria) and includes mild, moderate and severe chronic GVHD. Skin/hair, ocular, oral, pulmonary, gastrointestinal, hepatic, genitourinary, musculoskeletal, and hematologic systems were scored on a 0-3 scale to reflect degree of cGVHD involvement. Maximum grade is defined as the maximum grade of chronic GVHD (mild, moderate, or severe) that a participant experiences by 2 years post-transplant.

Percentage of participants with chronic GVHD (cGVHD) at will be estimated with 95% confidence intervals for each treatment group using the cumulative incidence estimate with the complementary log-log transformation, treating death prior to cGVHD as a competing event. Chronic GVHD is based on NIH Consensus Criteria (2014 NIH Consensus Criteria) and includes mild, moderate and severe chronic GVHD. Skin/hair, ocular, oral, pulmonary, gastrointestinal, hepatic, genitourinary, musculoskeletal, and hematologic systems were scored on a 0-3 scale to reflect degree of cGVHD involvement. This endpoint considers any cGVHD onset.

The number of participants experiencing the following complications and events will be tabulated at baseline, 1 year and 2 years post-transplant: Idiopathic pneumonia syndrome (IPS), Veno-occlusive disease (VOD), Various Central Nervous System (CNS) toxicities, Stroke, participants on immunosuppression for GVHD, and significant infections reported (any bacterial/fungal sepsis, Cytomegalovirus (CMV) reactivation with/without clinical disease, adenovirus, Epstein-Barr Virus (EBV)).

Participants will be followed for the entire 2 year duration of their time on study for the recurrence of Sickle Cell Disease (SCD) related complications. These SCD related complications are referred to as SCD events of special interest (SCD-EOSI) and will be summarized with frequency. These SCD-EOSI include: pulmonary hypertension, new onset of significant cerebrovascular event, renal function compromise, new onset of avascular necrosis of hip or shoulder, new onset of leg ulceration, new onset of acute chest syndrome, and new onset of painful vaso-occlusive crisis requiring hospitalization or parenteral opioid drug in the outpatient setting.

Hematological Outcomes will be summarized with mean and standard deviation at various timepoints. Depending on the measurement, "baseline" could be pre-hydroxyurea conditioning (day -70 pre-transplant) and/or pre-thymoglobulin (day -7 pre-transplant). Measures include: hemoglobin (Hgb) %, reticulocyte count %, and hemoglobin S level %.

Renal Function Outcomes will be summarized with mean and standard deviation at various timepoints. "Baseline" refers to pre-thymoglobulin (day -7 pre-transplant). Measures include: GFR (mL/min/1.73m2) and Estimated GFR. Estimated GFR is computed using the CKD-EPI Creatinine Equation 2021 for Adults and the Bedside Schwartz 2009 equation for Pediatrics.

Lung Function Outcomes will be summarized with mean and standard deviation at various timepoints. "Baseline" refers to pre-hydroxyurea (day -70 pre-transplant). Measures include: FEV1 (L), FVC (L), and TLC (L). All values in this table were reported by study site.

Cardiac Function is measured through tricuspid regurgitant jet velocity (TRJV). It will be summarized with mean and standard deviation at Baseline, 1, and 2 years post-transplant. "Baseline" refers to pre-hydroxyurea (day -70 pre-transplant).

Six Minute Walk Distance is measured in meters to assess how far a participant can walk in 6 minutes. It will be summarized with mean and standard deviation at Baseline, 1, and 2 years post-transplant. "Baseline" refers to pre-hydroxyurea (day -70 pre-transplant). Change from baseline will also be provided at the 1 and 2 years post-transplant visit.

Health-Related Quality of Life (QoL) assessed using the NIH's PROMIS short forms administered to English- and Spanish-speaking patients in the adult stratum. Questions about fatigue (short form 8a), pain interference (short form 8a), and pain intensity (short form 3a) are asked regarding the degree of difficulty in performing activities of daily living such as housework, social activities, and day to day activities. It is scored from 0 to 10 and converted to a standardized T-score with mean 50 and standard deviation 10. A higher T-score represents worse fatigue, pain interfering with more daily activities, and worse pain intensity.

Subjects who speak English and are 15 years or older will be asked to use a web-based diary to report pain intensity on a scale from 0 (no pain) to 10 (worst pain). Subject pain intensity score is reported as an aggregate of several AM and PM scores at Baseline, one year, and two years post-transplant timepoints.

Cause of Death is tabulated by age strata. Deaths among participants who were not transplanted are included.

Number of participants who reported the Maximum Infection Severity of Grade 2 and Grade 3. Only grade 2 and grade 3 infections occurring post transplantation were reported on the study. Grade 2 and grade 3 infections are defined by the BMT CTN Technical MOP. Higher infection grade indicates worse infection severity. The infection grading criteria are published online (https://bmtctn.net/administrative-manual-procedures-moppolicy-guidelines). Severity of grade 1, 2 and 3 are described for bacterial, fungal, viral, parasitic, and nonmicrobiological infections. For example, grade 2 fungal infections are defined as candida esophagitis, or proven or probably fungal sinusistis confirmed radiologically without orbital, brain or bone involvement. Grade 3 fungal infections are defined as Fungemia including candidemia, Proven or probably invasive fungal infections, Disseminated infections with histoplasmosis, blastomycosis, coccidiomycosis, or Cryptococcus, or Pneumocystis jiroveci pneumonia.

The number of systemic infections is reported. Infections are categorized by infection type. A participant can report multiple types of infections, so the categories are not mutually exclusive for participants. All grade 2 and grade 3 infections, as defined by the BMT CTN Technical MOP, occurring post transplantation were reported on the study.

Participants could be readmitted to a hospital for many reasons during follow-up. The causes of each readmission are tabulated by age strata. The protocol-specified scheduled transplant hospitalization is not included in this table.

Hematological Outcomes will be summarized with mean and standard deviation at various post-transplant timepoints. Measures in this table include: LDH (U/L)

Hematological Outcomes will be summarized with mean and standard deviation at various timepoints. Baseline timepoint is pre-thymoglobulin (day -7 pre-transplant). Measures in this table include: Bilirubin (mg/dL)

Hematological Outcomes will be summarized with mean and standard deviation at various timepoints. Baseline refers to pre-thymoglobulin (day -7 pre-transplant). Measures in this table include: Serum Ferritin Level (ng/dL)

Renal Function Outcomes will be summarized with mean and standard deviation at various timepoints. "Baseline" refers to pre-thymoglobulin (day -7 pre-transplant). Measures include: Creatinine Clearance (mL/min).

Renal Function Outcomes will be summarized with mean and standard deviation at various timepoints. Measures include: Urine Albumin Creatine Ratio (mg/g).

Lung Function Outcomes will be summarized with mean and standard deviation at various timepoints. "Baseline" refers to pre-hydroxyurea (day -70 pre-transplant). Measures include: FEV1 (percent predicted), FVC (percent predicted), FEV1/FVC (percent predicted), and TLC (percent predicted). All values in this table, including percent predicted, were reported by study site.

Lung Function Outcomes will be summarized with mean and standard deviation at various timepoints. "Baseline" refers to pre-hydroxyurea (day -70 pre-transplant). Measures include: FEV1/FVC (ratio of Liters). All values in this table were reported by study site.

Lung Function Outcomes will be summarized with mean and standard deviation at various timepoints. "Baseline" refers to pre-hydroxyurea (day -70 pre-transplant). Measures include: DLCO (%) and Oxygen Saturation (%). All values in this table were reported by study site.

Lung Function Outcomes will be summarized with mean and standard deviation at various timepoints. "Baseline" refers to pre-hydroxyurea (day -70 pre-transplant). Measures include: FEV1/FVC (ratio of percent predicted). All values in this table were reported by study site.

Average number of post-transplant follow-up days by age strata.