Reduction In Transfusion Burden Research Articles

Combination of a TGF-β ligand trap (RAP-GRL) and TMPRSS6-ASO is superior for correcting β-thalassemia.

A recently approved drug that induces erythroid cell maturation (luspatercept) has been shown to improve anemia and reduce the need for blood transfusion in non-transfusion-dependent as well as transfusion-dependent β-thalassemia (BT) patients. Although these results were predominantly positive, not all the patients showed the expected increase in hemoglobin (Hb) levels or transfusion burden reduction. Additional studies indicated that administration of luspatercept in transfusion-dependent BT was associated with increased erythropoietic markers, decreased hepcidin levels, and increased liver iron content. Altogether, these studies suggest that luspatercept may necessitate additional drugs for improved erythroid and iron management. As luspatercept does not appear to directly affect iron metabolism, we hypothesized that TMPRSS6-ASO could improve iron parameters and iron overload when co-administered with luspatercept. We used an agent analogous to murine luspatercept (RAP-GRL) and another novel therapeutic, IONIS TMPRSS6-LRx (TMPRSS6-ASO), a hepcidin inducer, to treat non-transfusion-dependent BT-intermedia mice. Our study shows that RAP-GRL alone improved red blood cell (RBC) production, with no or limited effect on splenomegaly and iron parameters. In contrast, TMPRSS6-ASO improved RBC measurements, ameliorated splenomegaly, and improved iron overload most effectively. Our results provide pre-clinical support for combining TMPRSS6-ASO and luspatercept in treating BT, as these drugs together show potential for simultaneously improving both erythroid and iron parameters in BT patients.

Efficacy and Safety of Luspatercept in Patients with HbE/β-Thalassemia from the BELIEVE Study: A Subgroup Analysis

Background: Thalassemias are a group of inherited blood disorders caused by impaired production of the globin chains of hemoglobin (Hb), resulting in anemia. HbE/β-thalassemia results from the co-inheritance of a specific point mutation in the β-globin gene with a second β-thalassemia mutation. The combination of mutations influences disease severity, ranging from mild to severe, with HbE/β-thalassemia accounting for about half of all cases of severe thalassemia. Patients (pts) with severe disease have higher red blood cell (RBC) transfusion requirements, which can be associated with increased risk of related morbidities. Treatments that can reduce dependence on RBC transfusions are needed to improve pt outcomes. Primary results from the BELIEVE study (NCT02604433) demonstrated the efficacy and safety of luspatercept to treat anemia in transfusion-dependent pts with β-thalassemia across genotypes including HbE (Cappellini MD, et al. HemaSphere 2020;4[S1]:108-109). A subsequent analysis of the final BELIEVE data for pts with β 0/β 0 mutations, a form of severe β-thalassemia, demonstrated similar results with longer treatment in this subgroup (Sheth S, et al. Blood 2022;140 [S1]:1946-1948). The aim of this post hoc sub-analysis was to investigate the efficacy and safety of longer-term luspatercept treatment in pts in the BELIEVE trial with HbE/β-thalassemia. Methods: The BELIEVE trial included adult pts with β-thalassemia or HbE/β-thalassemia (compound heterozygous β-thalassemia with mutation and/or multiplication of α-globin genes allowed) who required regular RBC transfusions (6-20 RBC units in the 24 wk before randomization with no transfusion-free period > 35 days). Pts were randomized 2:1 to receive luspatercept (1.0-1.25 mg/kg) or placebo subcutaneously every 3 wk and evaluated for response (defined as reduction in RBC transfusion burden ≥ 33% or ≥ 50% from baseline during any 12-wk interval over the entire study) and safety. Data were evaluated up to the final pt visit (Jan 5, 2021). Results: The BELIEVE trial enrolled 336 pts, 52 (15.5%) of whom had HbE/β-thalassemia; 31 were randomized to the luspatercept group of the overall intent-to-treat (ITT) population (13.8%; N = 224). At baseline, pts receiving luspatercept with HbE/β-thalassemia were similar in age compared with the overall ITT population (median 32 y vs 30 y, respectively) and had similar transfusion burden (median 13.0 units vs 14.0 units over 24 wk), but had higher median fetal Hb (6.1% vs 5.1%), higher median serum ferritin (2087.0 vs 1441.3 μg/L), and higher median liver iron content (10.8 vs 6.1 mg/g dry weight). The median (range) duration of luspatercept treatment for pts with HbE/β-thalassemia was similar to the overall ITT population (157.7 [51.0-207.1] wk vs 153.6 [1.7-215.0] wk). A similar proportion of pts with HbE/β-thalassemia as in the overall ITT population achieved ≥ 33% reduction in transfusion burden (83.9% vs 77.2%) and ≥ 50% reduction in transfusion burden (61.3% vs 50.0%) over any 12-wk interval with luspatercept treatment (Figure A). Median total duration of ≥ 33% reduction in transfusion burden response was longer for HbE/β-thalassemia pts versus the overall ITT population (722.0 days vs 586.0 days). In the HbE/β-thalassemia subgroup, 67.6% of pts experienced ≥ 1 treatment-emergent adverse event (TEAE) related to treatment versus 60.5% of pts in the overall luspatercept safety population. The proportion of pts experiencing grade ≥ 3 treatment-related TEAEs was 25.8% in the HbE/β-thalassemia subgroup and 12.1% in the overall safety population. Treatment-related TEAEs resulted in discontinuation of luspatercept in 6.5% and 9.0% of the HbE/β-thalassemia and overall safety populations, respectively. No treatment-related TEAEs resulted in death in either group (Figure B). Summary: The HbE/β-thalassemia sub-group of the BELIEVE study had rates of response that were consistent with the larger ITT population. Furthermore, pts with HbE/β-thalassemia experienced a longer median total duration of response compared with the overall ITT population with a similar safety profile. Additional evaluation of the efficacy and safety of luspatercept in a larger population of HbE/β-thalassemia pts would be valuable as the number of pts in this sub-analysis was small, yet these results suggest that luspatercept is as safe and effective for this subgroup of pts as for the wider β-thalassemia population.

Longitudinal Assessment of Transfusion Intensity in Patients with JAK Inhibitor-Naive or -Experienced Myelofibrosis Treated with Momelotinib in the Phase 3 Simplify-1 and Momentum Trials

Introduction: Anemia is a cardinal feature of myelofibrosis (MF), along with splenomegaly and constitutional symptoms. Red blood cell (RBC) transfusions, often used to manage anemia in patients (pts) with MF, are a negative prognostic factor for overall survival and are associated with diminished quality of life and increased healthcare-related economic burden. Momelotinib (MMB), a Janus kinase (JAK) 1/JAK2/activin A receptor type 1 inhibitor, has demonstrated clinically meaningful and durable improvements in anemia, splenomegaly, and symptoms. Prespecified anemia endpoints in MMB phase 3 studies prioritized achievement of a strict transfusion independence response, defined as no transfusions for ≥12 wk immediately before the end of wk 24, with all hemoglobin levels ≥8 g/dL. Longitudinal analysis of transfusion intensity (units per 28 days) in a phase 2 trial of MMB in pts with transfusion-dependent MF demonstrated a reduction in transfusion burden in most (85%) pts (Harrison C, et al. EHA 2023). Here, we further characterize the impact of MMB and comparators on transfusion burden in pts with JAK inhibitor-naive and -experienced MF from the phase 3 SIMPLIFY-1 and MOMENTUM trials. Methods: This analysis evaluated time-dependent transfusion burden in pts enrolled in the phase 3 SIMPLIFY-1 (NCT01969838) and MOMENTUM (NCT04173494) trials. SIMPLIFY-1 included pts with JAK inhibitor-naive MF randomized (1:1) to receive MMB or ruxolitinib (RUX). In MOMENTUM, pts with symptomatic (Myelofibrosis Symptom Assessment Form Total Symptom Score ≥10), anemic (hemoglobin <10 g/dL), JAK inhibitor-experienced MF were randomized (2:1) to receive MMB or danazol (DAN). All RBC units transfused were collected during the 24-wk randomized treatment period of each study and during the 84 days before receipt of randomized treatment on study for baseline assessment. Time-dependent transfusion burden was quantified by number of RBC units administered, in a tabular display of baseline- and treatment-period intensity. Pts were grouped jointly based on the baseline- and treatment-period intensity of RBC units per 28 days into ordinal bins: exactly zero units, >0 to 1 unit, >1 to 2 units, >2 to 3 units, >3 to 4 units, and >4 units. Results: In SIMPLIFY-1 (JAK inhibitor-naive pts), 150 of 213 evaluable pts (70%) in the MMB arm and 163 of 216 evaluable pts (76%) in the RUX arm required zero units of RBC transfusion per 28 days at baseline. Of pts who required zero units of transfusion at baseline, a higher proportion in the MMB arm (142 of 150 [95%]) maintained a requirement of zero RBC transfusions during randomized treatment of 24 wks vs the RUX arm (93 of 163 [57%]). Overall, the mean RBC transfusion burden per 28 days declined 0.10 units (SD, 0.701) from baseline to randomized treatment in the MMB arm and increased 0.39 units (SD, 1.016) in the RUX arm. Using ordinal bins, 87% of pts in the MMB arm maintained (144 [67.6%]) or improved (41 [19.2%]) RBC transfusion intensity during randomized treatment compared with baseline vs 54% in the RUX arm (maintained, 94 [43.5%]; improved, 23 [10.6%]) (Figure). In MOMENTUM (JAK inhibitor-experienced pts), most pts had some transfusion requirement at baseline, with 26 of 130 (20%) in the MMB arm and 11 of 65 (17%) in the DAN arm requiring zero units of RBC transfusion per 28 days. During randomized treatment, a higher proportion of pts in the MMB arm (46 of 130 [35%]) required zero units of RBC transfusion vs the DAN arm (11 of 65 [17%]), including a higher proportion of those who had zero RBC transfusion requirement at baseline who maintained zero RBC transfusion requirement during randomized treatment (MMB, 92%; DAN, 64%). The mean RBC transfusion burden per 28 days declined 0.86 units (SD, 1.748) from baseline to randomized treatment in the MMB arm and declined 0.28 units (SD, 1.584) in the DAN arm. Using ordinal bins, 85% of pts in the MMB arm maintained (25 [19.2%]) or improved (85 [65.4%]) RBC transfusion intensity compared with baseline vs 63% in the DAN arm (maintained, 7 [10.8%]; improved, 34 [52.3%]). Conclusions: These data demonstrate that MMB was associated with better maintenance of RBC transfusion intensity and zero RBC transfusion status vs RUX in pts with MF who were JAK inhibitor naive and showed greater reduction in RBC transfusion burden from baseline vs DAN in pts with MF who were JAK inhibitor experienced. Across both trials, ≥85% of pts treated with MMB maintained or improved transfusion intensity.

Clinical Parameters, Anemia, and Spleen Response in Patients with MF-Related Anemia Treated with Luspatercept: Efficacy Sub-Analysis from the ACE-536-MF-001 Study

Introduction: Approximately 24% of patients with myelofibrosis (MF) have anemia requiring red blood cell (RBC) transfusion at initial diagnosis. For patients with MF, chronic anemia and RBC transfusion dependence (TD) often increase throughout the disease course and are an indicator of poor prognosis. Luspatercept (LUSPA) is an erythroid maturation agent approved to treat anemia in adults with β-thalassemia and myelodysplastic syndrome requiring RBC transfusions. Primary results from the phase 2 ACE-536-MF-001 study (NCT03194542) demonstrated reductions in MF-related anemia and transfusion dependence (Gerds et al. ASCO 2023 7016). Here we provide an extended analysis of the impact of LUSPA on clinical parameters and transfusion burden over time, and associated management of MF disease symptoms. Methods: Patients were enrolled into cohorts based on TD and ruxolitinib (RUX) treatment. Patients received LUSPA 1.0 mg/kg subcutaneously (with titration up to 1.75 mg/kg), administered on day 1 of each 21-day cycle (starting dose was 1.33 mg/kg for cohort 3B expansion). Patients were defined as TD if receiving an average of 4-12 RBC units/84 days immediately up to cycle 1 day 1 (C1D1). For non-transfusion dependent (NTD) patients, anemia was defined as 3 or more hemoglobin (Hgb) level measurements of ≤ 9.5 g/dL recorded on at least 3 different days in the 84-day period immediately preceding C1D1. The primary endpoint was anemia response, assessed at day 169 (week 24) and defined as 84 consecutive days without RBC transfusion for TD patients, and 84 consecutive days with Hgb increase of ≥ 1.5 g/dL from baseline without transfusion for NTD patients. Treatment was extended if clinical benefit was observed at day 169. Secondary and exploratory endpoints included anemia response for the entire treatment period, transfusion burden, and clinical and laboratory parameters. Results: A total of 95 patients were enrolled: cohort 1 (NTD, no RUX, n = 22), cohort 2 (TD, no RUX, n = 21), cohort 3A (NTD, RUX, n = 14), and cohort 3B (TD, RUX, n = 38). A total of 63 (66.3%) patients continued to the follow-up period. The mean (SD)/median (range) duration of treatment was 42.8 (47.6)/24.0 (2.0-232.0) weeks and mean/median (range) follow-up duration after first dose was 101.1/78.0 (2.1-232.1) weeks. Anemia response was seen across all cohorts. Among transfusion-dependent patients (cohorts 2 and 3B), transfusion independence ≥ 12 weeks was observed in 4 (19.0%, 95% CI 5.45-41.91) and 12 (31.6%, 95% CI 17.5-48.7) patients, respectively, in the entire treatment period. Additionally, approximately half of patients with TD achieved a 50% reduction in transfusion burden; 10 (47.6%) patients in cohort 2 and 20 (52.6%) patients in cohort 3B had ≥ 50% reduction in transfusion burden over any 84-day period in the entire treatment period, including 16 patients from cohorts 2 and 3B who achieved transfusion independence (100% reduction) (Figure). Changes in laboratory parameters of Hgb, serum erythropoietin, serum ferritin, and platelet count at day 169 are summarized in the Table; in addition, patients with clinical benefit continuing LUSPA treatment after day 169 showed ferritin decreases with longer follow-up from cycle 13 (n = 20) to cycle 33 (n = 6). Additionally, there was minimal (~1 cm) to no increase in median spleen size across patients in all cohorts. Of the 3 patients in cohort 3B who increased their RUX dose during LUSPA treatment, spleen size remained stable, with a -4.0 cm, 1.0 cm, and 3.0 cm change from baseline during the entire treatment period, respectively. Conclusions: In the phase 2 ACE-536-MF-001 study, LUSPA demonstrated improvements in anemia and transfusion burden in patients with MF. Further analysis of clinical and laboratory parameters may reveal differences between responders and non-responders. Spleen size stability was observed in all patients; this suggests that LUSPA does not worsen splenomegaly and may support continual use of RUX for MF disease and symptoms. Study support: Bristol Myers Squibb.

Real-World Characteristics, Treatment Utilization, and Transfusion Burden in Patients with β-Thalassemia Initiating Luspatercept: A US Cohort Study

Introduction: β-thalassemia is a β-globin gene disorder resulting in decreased production of hemoglobin A and chronic anemia. Disease severity ranges from asymptomatic, mild anemia to life-long red blood cell transfusion dependence. Luspatercept is an erythroid maturation agent that reduces transfusion burden in patients with transfusion-dependent β-thalassemia. We describe real-world baseline demographics and clinical characteristics alongside treatment utilization patterns in US patients with β-thalassemia treated with luspatercept. Methods: This retrospective, observational, cohort study used Komodo Health's Healthcare Map, a large administrative claims database in the USA. Patients with a diagnosis of β-thalassemia (ICD-10 code: D56.1) who initiated luspatercept treatment between January 1, 2020 and September 30, 2021 were included; the full study period was July 1, 2019 to September 30, 2022. The index date was defined as the first documented administration of luspatercept during the identification period. Patients were adults (≥ 18 years of age on index date) continuously enrolled for 6 months before (baseline) and 12 months after (follow-up) the index date. Discontinuation was defined as no medication claim for ≥ 90 days (assuming a 3-week schedule while taking into account potential dose delays). Descriptive statistics were used to analyze and report baseline demographics and clinical characteristics. Time-to-event variables were assessed using Kaplan-Meier methods. Results: The 101 patients included had a mean (standard deviation [SD]) age of 37.7 (14.9) years, with a broad geographical spread throughout the USA (Midwest n = 17, 16.8%; Northeast n = 24, 23.8%; South n = 28, 27.7%; West n = 32, 31.7%). Approximately half (52.5%) were female, and mainly commercially insured (56.4%). Patients were in relatively good health (mean [SD] Charlson Comorbidity Index: 0.8 [1.7]). Bone deformities (n = 16, 15.8%), hepatosplenomegaly (n = 13, 12.9%), and thrombotic events (n = 10, 9.9%) were the most common β-thalassemia-related comorbidities observed in the baseline period. Median (interquartile range) baseline transfusion frequency during the 6-month baseline period was 4.0 (8.0), and 55.0% of the patients were transfusion dependent (≥ 4 transfusions in the 6-month baseline period). Over 40% of patients remained on luspatercept after 1 year of treatment with a median time to discontinuation of 96.5 days (Figure). Approximately one fifth (19.0%) of patients who discontinued luspatercept reinitiated treatment (Figure). Among those who were transfusion-dependent who stayed on luspatercept at 6 months, 31.3% (10/32) experienced a reduction in the frequency of transfusions, with a median decrease of 2 visits in the 6-month follow-up period from baseline, and 28.1% (9/32) observed a decrease in the units of blood transfused, with a median decrease of 5 units in the 6-month follow-up period from baseline (Table). Similarly, among patients who were transfusion-dependent who stayed on luspatercept for 12 months, 32.0% (8/25) experienced a reduction in the frequency of transfusions, with a median decrease of 2.5 visits in the follow-up period from baseline, and 48.0% (12/25) observed a decrease in the units of blood transfused, with a median decrease of 3.7 units in the 12 month follow-up period from baseline (Table). Conclusion: This study shows that patients with β-thalassemia treated with luspatercept saw a substantial reduction in transfusion burden, in both the frequency of blood transfusion and units of blood used. As those who remained on luspatercept longer, through 12 months, saw an increased reduction in transfusion burden from baseline, these findings suggest the clinical and real-world benefit of longer-term luspatercept treatment.

Phase 1b/2 Study Evaluating the Safety and Efficacy of Canakinumab with Darbepoetin Alfa in Patients with Lower-Risk Myelodysplastic Syndromes (MDS) Who Have Failed Erythropoietin Stimulating Agents (ESA)

Introduction: Pyroptosis is a form of inflammatory, caspase-1 dependent lytic cell death mediated by inflammasome activation and ultimately leading to enumeration of pro-inflammatory cytokines, particularly interleukin 1β (IL-1β) and is a key driver of MDS pathogenesis (Basiorka A, Blood 2016). Release of IL-1β by pyroptotic cells leads to paracrine stimulation of neighboring hematopoietic and stromal cells resulting in amplification of this circuit, myeloid derived suppressor cell (MDSC) accumulation as well as direct suppression of erythropoiesis. Thus, we investigated the combination of the IL-1β neutralizing antibody canakinumab in combination with darbepoetin in patients with ESA refractory lower risk MDS and present the final dose phase 1b data. Methods: Patients ≥ 18 years old with IPSS-R very low to intermediate risk MDS who were ESA refractory and hypomethylating agent (HMA) naïve with adequate organ function were eligible. Patients must have been RBC transfusion dependent or hemoglobin < 9 gm/dl with symptoms. Treatment consisted of subcutaneous (SC) canakinumab on day 1 of a 28 cycle (150mg dose level 1, 300mg dose level 2) and darbepoetin SC 300µg days 1 and 15 of each cycle for a total of 6 cycles with continuation of therapy for responding patients. The phase 1b portion utilized a 3+3 dose escalation design with 6 patients treated at the maximum tolerated dose (MTD) to define the recommended phase 2 dose (RP2D). Bone marrow (BM) disease assessments occurred every 3 cycles with response defined by IWG 2018 criteria. Quality of life was assessed by QUALMS (Abel A, Haematologica, 2016). Peripheral blood mononuclear cells (PBMCs) were obtained at disease assessments and day 15 of C1 for evaluation of adapter protein apoptosis associated speck-like protein containing a CARD (ASC) specks as a biomarker of inflammasome formation with quantification as previously described (McLemore A, Pyroptosis: Methods and Protocols, 2023). Total IL-1β of BM plasma was assayed by ELISA. Results: Nine patients enrolled with a median age of 71 (range: 61-85 years), 67% female with baseline IPSS-R, IPSS-M and mutation data shown in Table. By IPSS-M, 3, 3, 1, 2 patients were low, moderately-low, moderately high, and high-risk categories. All IPSS-M lower risk mutant patients had splicing mutations. The median number of mutations was 2 (range 0-5). 100% of patients were ESA refractory. Additionally, 33% and 56% were refractory to lenalidomide and luspatercept therapy, respectively. Eight (89%) patients were PRBC dependent at baseline (56% [n=5] with high transfusion burden). The median follow-up duration was 6.1 months (range 3-17.8). The most common adverse events were neutropenia (n=7), followed by thrombocytopenia (n=4), and abnormal liver function tests (n=4). There were two grade 3 adverse events including thrombocytopenia and colitis, both unrelated to study treatment. There were no dose-limiting toxicities or serious adverse events in the phase 1 portion. All patients achieved the best response as stable disease, and no one had progression disease. No patients achieved objective response or significant reduction in transfusion burden. There was no statistical improvement in total QUALMS score from baseline to end of treatment (P=0.72) nor in the individual components (i.e. physical burden, benefit finding and emotional burden, P=0.69, P=0.91, P=0.630; respectively) although several patients had individual improvements. The percentage of PBMCs with ASC specks at baseline ranged from 0.3945-2.978% (median 1.93%). ASC specks decreased significantly after cycle 1 of therapy and were durably suppressed over the course of treatment in a majority of patients (Figure). Extracellular IL-1β in bone marrow plasma robustly increased with treatment and remained elevated (representing non-functional IL-1β [canakinumab bound IL-1β]; P=0.002 cycle 6 versus baseline), supporting pharmacodynamic effect with no differences observed between DL1 and DL2. Conclusions: The combination of canakinumab and darbepoetin was safe and well tolerated and 300mg of canakinumab is the RP2D. Canakinumab inhibited inflammasome activation as evidenced by a reduction of ASC specks although this did not translate to clinical responses. Phase 2 of the study will focus on patients with lower transfusion burden and molecular subsets with highest IL-1β expression (e.g. TET2/ DNMT3A mutant).

Efficacy and Safety of Luspatercept in Patients Enrolled in the BELIEVE Trial: Data from the Phase 3b Long-Term Rollover Study

Background: Ineffective erythropoiesis and anemia are pathognomonic features of β-thalassemia, leading to red blood cell (RBC) transfusion dependence in patients with more severe genotypes and consequently increased morbidity and mortality. The phase 3 BELIEVE study showed that luspatercept reduces transfusion burden in transfusion-dependent patients with a manageable safety profile (Cappellini MD, et al. HemaSphere 2022;6[S3]:171-172; Viprakasit V, et al. HemaSphere 2022;6[S3]:2664-2665). Patients who continued to benefit from luspatercept at completion of the BELIEVE study or who needed to complete post-treatment follow-up could roll over to the phase 3b long-term follow-up study (LTFU; NCT04064060) to continue receiving treatment or complete post-treatment follow-up, respectively. Patients receiving luspatercept were monitored for continued efficacy and safety. Methods: The aim of this analysis was to evaluate long-term safety and efficacy of luspatercept in patients who rolled over to the LTFU study. This analysis included patients randomized to luspatercept during BELIEVE (luspatercept group) and those randomized to placebo who crossed over to receive luspatercept after unblinding (crossover group). Response was defined as ≥ 33% reduction from baseline in RBC transfusion burden during any 12-week interval over the entire treatment period of the combined studies. The data cutoff was Jan 2, 2023. Results: At the closure of the BELIEVE trial, 127/224 (56.7%) patients from the luspatercept group and 67/92 (72.8%) patients from the crossover group had transitioned to the LTFU study with the intention to continue luspatercept. At data cutoff, treatment was ongoing for 138 patients, 90 in the luspatercept group and 48 in the crossover group. Median (range) total treatment duration over the combined studies was 229.1 (1.7-336.1) weeks for the luspatercept group and 221.2 (6.1-230.7) weeks for the crossover group; 98 patients had completed 288 weeks (> 5 years) of treatment at data cutoff, all of whom had been randomized to luspatercept. In the luspatercept group, 180/224 (80.4%) patients had achieved response, continuing the trend showing an increasing proportion of responders with longer duration of treatment observed at previous data cutoffs (Figure A). Response in the crossover group was similar with 71/92 (77.2%) responders. Patients in the luspatercept and crossover groups had median (range) reductions in transfusion burden of −17.75% (−100.0 to 33.3) and −19.05% (−100.0 to 20.8), respectively, from baseline to week 145-192, equating to mean reductions of 6.78 RBC units (SD 7.27; n = 120) and 6.85 RBC units (SD 6.78; n = 50), respectively. Liver iron concentration in the luspatercept group was reduced with long-term treatment at each timepoint compared with the baseline (mean decrease of 2.80 mg/g dry weight [dw] at week 144 from median 8.97 [range, 1.1-31.9] at baseline [n = 24]; mean decrease of 0.45 mg/g dw at week 192 from median 7.75 [1.4-35.5] at baseline [n = 27]; mean decrease of 1.48 mg/g dw at week 240 from median 5.65 [1.0-42.0] at baseline [n = 20]). Mean changes from baseline in overall serum ferritin levels (last 24-week level for each patient prior to their efficacy cutoff) were −376.27 μg/L for luspatercept and +43.09 μg/L for crossover. In the combined studies up to data cutoff, 59.4% of luspatercept patients and 47.8% of crossover patients discontinued treatment. The most frequent reason for treatment discontinuation was the patient's personal decision to withdraw (luspatercept: 23.7% in BELIEVE and 33.5% in the combined studies; crossover: 14.1% in BELIEVE and 28.3% in the combined). Discontinuation due to an adverse event (AE) in the combined studies was similar to experience from BELIEVE (luspatercept: 10.3% BELIEVE and 12.5% combined; crossover: 4.3% BELIEVE and 7.6% combined). One patient (0.4%) discontinued luspatercept and transitioned to a commercially available treatment. The frequency of treatment-emergent AEs in the combined studies was also consistent with previous experience from the BELIEVE trial (Figure B). Summary: These long-term data from the LTFU study show that erythroid responses and safety results in both the luspatercept and crossover groups were consistent with previous clinical experience from the BELIEVE trial. Patients receiving long-term luspatercept treatment experience durable clinical benefit with no new safety concerns.

Effect of Luspatercept on Erythropoiesis and Fetal Hemoglobin in β-Transfusion-Dependent Thalassemia Patients: A Real-Life Experience

Background: Luspatercept is the first erythropoiesis-stimulating agent approved for transfusion-dependent β-thalassemia (TDT). In the BELIEVE trial, more than 70% of the patients had a hematological response defined as a reduction of ≥33% of transfusion burden in any 12-week interval. In our experience, some patients have a clinical benefit even if a response as defined by the clinical trial is not reached. Indeed, several aspects remain to be addressed, including its specific effects on erythropoiesis. Fetal hemoglobin (HbF) has been hypothesized as a potential marker in response evaluation. However, no results have been published, excluding an abstract presentation by Cappellini MD et al. at the European Hematology Association meeting in 2019, showing a greater HbF increase in responders vs. non-responders. Aim: This study aims to evaluate the effect of luspatercept on erythropoiesis and the hemoglobin (Hb) fractions in patients with β-TDT treated with luspatercept in a real-life setting at our Center in Milan, Italy. Methods: Inclusion criteria: age ≥18 years, β-TDT eligible for treatment with luspatercept, and signed informed consent. Exclusion criteria: unwilling to participate in the study. We assessed hematological parameters, Hb fractions, and erythropoiesis markers at baseline and over the treatment period of up to 48 weeks (Dose16). We also extracted mRNA from reticulocytes (RET) from peripheral blood at fixed doses and analyzed the expression of a panel of genes involved in erythropoiesis. We evaluated hematological variables dividing the patients into three groups of responses defined: Full responder (FR): reduction of transfusion burden ≥33% and ≥2 units of blood in any 12-week intervalIntermediate responder (IR): patients with a reduction in transfusion burden ≥25% and <33% in any 12-week intervalNon-responder (NR): reduction of the transfusion burden <25%. Statistical analysis at baseline was performed using Kruskal-Wallis test. We fitted linear random intercept regression models to evaluate time trends of hematological variables. Results: Thirty-seven patients have been enrolled in the study. 3/37 have been excluded from the analysis because they developed adverse events leading to drug interruption before completing 12 weeks of treatment. We herein present the data of the 29/34 subjects who reached at least 12 weeks of treatment as of July 20, 2023. The median age was 41 yrs (range 19-63 yrs), 15 were females (52%). 8/29 (28%) had a β0/β0 genotype; 12/29 (41%) patients underwent splenectomy. Twelve patients had a FR, 6 an IR, and 11 were NR. We found that the baseline median absolute value of HbF (g/dL) was different in the three groups (NR: 0.21, range 0.09-0.34; IR: 0.37, range 0.14-1.52; FR: 0.95, range 0.31-1.65, p=0.009) (Figure 1). In all subjects, HbF increased over time. However, the increase was different in the three groups (p-interaction: 0.0001). In the linear regression model (Figure 2), the HbF absolute increase per week was 0.004 g/dL (95% confidence interval (CI): 0.002-0.006) among NR, 0.015 (CI: 0.008-0.022) in the IR group and 0.03 g/dL (CI: 0.02-0.04) in the FR group. EPO baseline value was similar in the three groups, but unexpectedly we observed different increases over time (p-interaction: 0.0001). In the IR and FR groups, the regression slopes were 6.66 U/L (CI: 3.11-10-21) and 9.42 U/L (CI: 5.53-13.31) per week, respectively. In the NR group, there was no EPO increase. Interestingly, the baseline value of erythroblasts (EB) was different between the three groups, with FR having the highest value. EB increased in both IR and FR, with the IR group displaying a steeper increase and finally reaching the FR group. Preliminary results on gene expression in RET showed an upregulation of GATA-1 and its target genes involved in erythroid differentiation and heme biosynthesis, as shown in the murine model (Martinez PA et al. 2019), irrespective of the response group. Conclusions: Our findings identify baseline HbF as a possible predictor of response. Also, the HbF trend could represent a marker of response to luspatercept in β-TDT patients. Furthermore, HbF can be useful in identifying patients in the IR group with the best chance of becoming responders in long-term treatment. Our preliminary results also suggest that luspatercept acts by enhancing erythropoiesis and leads to an increase in EPO levels and EB. Studies on more patients are needed to confirm these findings.

Predictive Biomarkers of Response to Luspatercept in Patients with Myelofibrosis- (MF) Associated Anemia: Biomarker Analysis from the ACE-536-MF-001 Study

Introduction: MF is a clonal myeloproliferative neoplasm that results in fibrosis of the bone marrow and impaired hematopoiesis. Among other clinical manifestations, ineffective erythropoiesis leads to anemia resulting in poor quality of life and reduced overall survival (Passamonti et al., Blood 2010). Current treatment options for MF-associated anemia with most agents lack optimal efficacy and durability of response (Cervantes et al., Expert Rev Hematol., 2016). Luspatercept is a transforming growth factor-β (TBF-β) family ligand trap that inhibits the TGF-β-Smad signaling axis and promotes late-stage erythropoiesis. Luspatercept is approved in low-risk MDS with ring sideroblasts and β-thalassemia requiring red blood cell (RBC) transfusion. The ACE-536-MF-001 study investigates the safety and efficacy of luspatercept in the treatment of MF-related anemia. Here, through mutational and cytokine analysis of ACE-536-MF-001 biomarker samples, we sought to identify mutational and cytokine profiles associated with response. Methods: Eligible patients were divided into 4 cohorts based on transfusion dependence (TD) and treatment with ruxolitinib (RUX). Cohorts 1 and 3A were non transfusion dependent (NTD) while cohorts 2 and 3B were TD patients receiving 4-12 RBC units/84 days up to C1D1. Cohorts 3A and 3B received a stable dose of RUX. All patients received 1.0 mg/kg of luspatercept (1.33 mg/kg for cohort 3B) with titration up to 1.75 mg/kg once every 21 days. Primary endpoint was anemia response (defined as an increase of ≥ 1.5 g/dL hemoglobin (Hgb) from baseline for cohorts 1/3A or RBC transfusion free for ≥ 12 consecutive weeks for cohorts 2/3B). Secondary endpoint was mean Hgb increase ≥ 1.5 g/dL from baseline for ≥ 12 consecutive weeks for cohorts 1/3A, or ≥ 50% decrease in RBC transfusions from baseline for ≥ 12 consecutive weeks and duration of RBC transfusion-free period for cohorts 2 and 3B. Mutational analysis was performed in DNA from peripheral blood mononuclear cells using a panel targeting 74 genes. Rules-Based Medicine's Human Inflammation panel was used to measure changes in 54 serum cytokines. Nexelis custom panel was used for detection of GDF8, GDF15, erythroferrone, soluble transferrin receptor 1 (sTfR1) and hepcidin. Changes in soluble factors from cycle 1 to end of week 24 (day 169) were examined for correlation with clinical response. Results: All 4 cohorts (N = 95) displayed improvement in anemia and TD patients receiving RUX had the greatest benefit (Gerds et al. EHA 2023 S167). In the biomarker cohort (n = 63 across all 4 cohorts), mutational analysis revealed that most patients carried the JAK2 V617F mutation, and patients with SF3B1 or SF3B1 with co-occurring DTA mutations ( DNMT3A, TET2 or ASXL1) had a favorable prognosis related to anemia response (p= 0.0260, 0.0495; OR= 3.54, 3.86). In addition, JAK2 V617F patients in cohort 3B showed clinical benefit with luspatercept (OR= 6.75, p= 0.0445). Across cohorts and endpoints, the general trend of responders was low baseline (2-3-fold lower relative to nonresponders) levels of key inflammatory cytokines. Low levels of IL-10 (TD patients) and VCAM-1, TNFR2, CRP and IL-18 (NTD patients) were significant ( P < 0.01) predictors of response. Paired analysis between cycle 1 and week 24 revealed increases in alpha-2-macroglobulin, haptoglobin, TIMP1, and decrease in C3, vitamin D-binding protein, hepcidin and sTfR1 associated with anemia response. When transfusion burden reduction was used as a response criterion, ferritin, hepcidin, thrombopoietin, von Willebrand Factor, sTfR1, and beta-2-microglobulin were significantly ( P < 0.05) associated with response (Figure). In addition, Hgb increase was associated with increased TGF-β1 and VEGF levels and decreased GDF-15 and ERFE. These cytokines are implicated in iron metabolism (ferritin, hepcidin, alpha-2-macroglobulin), Hgb catabolism (haptoglobin), anemia (vitamin D-binding protein, C3), and luspatercept-target engagement (hepcidin, sTfR1). Conclusions: Our analysis identifies unique predictors of response to luspatercept treatment in patients with MF. While the data describe our findings across cohorts, cohort 3B (TD, receiving RUX), which had the highest response rate, also had higher levels of RANTES and TPO at baseline in responders. The ongoing phase 3 study, INDEPENDENCE (NCT04717414), would validate these observations in a larger cohort of patients

Pacritinib is a potent ACVR1 inhibitor with significant anemia benefit in patients with myelofibrosis

AbstractIn patients with cytopenic myelofibrosis, treatment with the JAK2/IRAK1 inhibitor pacritinib was associated with anemia benefit in the phase 3 PERSIST-2 study. The impact of pacritinib on transfusion independence (TI) has not been previously described, nor has the mechanism by which pacritinib improves anemia been elucidated. Because it has been previously postulated that inhibition of activin A receptor, type 1 (ACVR1)/activin receptor-like kinase-2 improves anemia in patients with myelofibrosis via suppression of hepcidin production, we assessed the relative inhibitory potency of pacritinib compared with other JAK2 inhibitors against ACVR1. Pacritinib inhibited ACVR1 with greater potency (half-maximal inhibitory concentration [IC50] = 16.7 nM; Cmax:IC50 = 12.7) than momelotinib (IC50 = 52.5 nM; Cmax:IC50 = 3.2), fedratinib (IC50 = 273 nM; Cmax:IC50 = 1.0), or ruxolitinib (IC50 > 1000; Cmax:IC50 < 0.01). Pacritinib’s inhibitory activity against ACVR1 was corroborated via inhibition of downstream SMAD signaling in conjunction with marked suppression of hepcidin production. Among patients on PERSIST-2 who were not transfusion independent at baseline based on Gale criteria, a significantly greater proportion achieved TI on pacritinib compared with those treated on best available therapy (37% vs 7%, P = .001), and significantly more had a ≥50% reduction in transfusion burden (49% vs 9%, P < .0001). These data indicate that the anemia benefit of the JAK2/IRAK1 inhibitor pacritinib may be a function of potent ACVR1 inhibition.

“Luspatercept: a lifesaving therapy for transfusion-dependent thalassemia patients with alloimmunization complications”

This case demonstrates the benefits of luspatercept for thalassemic patients who are unable to receive adequate blood transfusions. It acts as a selective ligand trap and inhibits TGF- signaling via Smad2/3 to promote differentiation and maturation of late-stage erythroid precursors. Phase III clinical data showed that a 33% reduction in transfusion burden from baseline was achieved. The administration of luspatercept was a challenge due to the coexistence of antiphospholipid syndrome, portal vein thrombosis and splenectomy. Since initiating luspatercept, the patient has not experienced any adverse events and her general condition has improved.

Long-Term Hemoglobin Response and Reduction in Transfusion Burden Are Maintained in Patients with Pyruvate Kinase Deficiency Treated with Mitapivat

Long-Term Hemoglobin Response and Reduction in Transfusion Burden Are Maintained in Patients with Pyruvate Kinase Deficiency Treated with Mitapivat

Investigations into the Mechanisms and Clinical Implications of Modulation of Hepcidin Levels By Luspatercept in TD MDS and TD b-Thalassemia

Introduction: Multiple blood transfusions lead to significant iron overload in transfusion dependent (TD) thalassemia (TDT) and TD-MDS. This excess iron is deposited in various organs leading to end organ damage, morbidity, and mortality. Iron overload patients are treated with iron chelation therapy (ICT) owing to lack of effective physiological iron removal mechanisms. Furthermore, chronic transfusions lead to paradoxical changes in hepcidin, the master regulator of iron homeostasis. While hepcidin is upregulated under conditions of increased intracellular and extracellular iron concentrations through BMP6 and IL6 dependent signaling; it is downregulated during expanded erythropoiesis through Erythroferrone (ERFE) to increase iron availability for developing erythron. Increased levels of hepcidin sequesters iron within organs leading to inefficiency of iron chelation therapy in TD-MDS and TDT patients. Luspatercept is a modified activin receptor fusion protein (modified ActRIIB-Fc) that sequesters certain members of TGF-b superfamily ligands, thus enhancing late-stage erythroid-maturation. Luspatercept is approved for TDT and TD-MDS patient populations-based on significant reduction in transfusion burden in two independent phase 3 trails (BELIEVE and MEDALIST, respectively). Here, we evaluated modulation of hepcidin levels with luspatercept treatment and its clinical implications in anemias due to elevated levels of hepcidin including TD-MDS and TDT patients. Methods: Luspatercept was administered sub-cutaneously every three weeks. Hepcidin and ERFE levels were measured in serum or plasma samples from BELIEVE (NCT02604433) and MEDALIST (NCT02631070) trial patients using specific ELISA and or chemiluminescence assay kits at week 25 following treatment. The regulation of hepcidin by luspatercept, BMP6 and IL6 in HepG2 cell-line model was determined by ELISA (in conditioned media) and q-PCR at increasing doses and time points. Results: Serum hepcidin levels at baseline across both arms in MEDALIST and BELIEVE were 80.65 ng/ml and 43.1 ng/ml respectively. These were significantly higher than normal healthy individuals (range of 5-10 ng/ml; P < 0.001), reported previously (Ilkovska etal JIMB 2016). Patients treated with luspatercept in both TDT and TD-MDS showed significant reduction in serum levels of hepcidin by 49% and 53% respectively (P<0.001) at week 25 compared to baseline. Hepcidin levels in the placebo group in TD-MDS patients demonstrated an increase of 119% (P<0.001) and a decrease of 12% in TDT patients (P=0.004) at the same time point. In addition, ERFE protein levels in serum, were elevated in response to Luspatercept treatment in both TD-MDS (30%) and TDT (51%) (P<0.001) in comparison to the placebo arms of decrease of 28% in TD-MDS and an increase of 2% in TDT. In HepG2 cells, treatment with recombinant BMP6 and IL6 increased hepcidin protein expression in a dose dependent manner. Luspatercept treatment inhibited this increase in hepcidin expression mediated by BMP6 and IL6. Time course analyses (2, 6, 24 and 72 hours), revealed that luspatercept inhibited hepcidin transcription and secretion levels starting at 24 hours. Conclusions: Luspatercept treatment reduced transfusion burden and iron loading rate due to improved erythropoiesis and release of ERFE by maturing erythroblasts consequently leading to reductions in elevated hepcidin levels in both TD-MDS and TDT patients. Our data provides a mechanistic rationale for downregulation of hepcidin levels with luspatercept treatment. Interestingly, cell-based assay data suggest that luspatercept directly modulates hepcidin transcription suggesting that in diseased conditions with abnormally higher levels of hepcidin and TGFβ family ligands, luspatercept might also modulate hepcidin transcription by sequestering TGFβ family ligands implicated in hepcidin synthesis. We postulate that decreased hepcidin levels results in release of excess iron into peripheral blood, making it available for effective chelation. These observations implicate sequencing of luspatercept, and ICT for effective management of iron overload in these TD patients. Furthermore, the data provide a mechanistic rationale for evaluating luspatercept in hepcidin dependent anemia of inflammation and iron refractory iron deficiency anemia (IRIDA) disease indications.

An evaluation of mitapivat for the treatment of hemolytic anemia in adults with pyruvate kinase deficiency

Introduction Pyruvate kinase deficiency (PKD) is the most common cause of congenital nonspherocytic hemolytic anemia. Until recently, treatment had been limited to supportive management including red blood cell transfusions, splenectomy, and management of chronic disease complications such as iron overload and decreased bone mineral density. Areas covered We discuss preclinical data and phase 1, 2, and 3 clinical studies evaluating mitapivat for adult patients with hemolytic anemia secondary to PKD. Mitapivat has been shown to offer early and durable improvement in hemoglobin with reduction in transfusion burden, and preliminary data suggests it can induce a negative iron balance in many patients without the use of dedicated iron chelators. Expert opinion Mitapivat is a first-in-class allosteric activator of pyruvate kinase and the first FDA-approved disease directed therapy for PKD. It has a favorable safety profile and clear clinical efficacy. Given the considerable genetic heterogeneity of PKD and the rapid effect on improving hemoglobin and reducing hemolysis, a therapeutic trial of mitapivat should be considered in all patients with PKD who are not homozygous for the PKLR R479H mutation. Further investigations are needed regarding long-term safety and efficacy profiles and whether long-term PKD-associated complications can be reduced or even reversed.

Luspatercept, a two-edged sword in beta-thalassemia-associated paravertebral extramedullary hematopoietic masses (EHMs).

Paravertebral extramedullary hematopoietic masses (EHMs) account for up to 15% of extramedullary pseudotumors in beta-thalassemia (BT) and are most likely related to compensatory hematopoiesis. In most cases, pseudotumors are incidentally detected, as the majority of patients are asymptomatic. Since June 2020, luspatercept is approved for the treatment of patients with BT who require regular red blood cell transfusions. Data addressing the safety and efficacy of luspatercept in patients with BT-associated EHMs are pending. To date (May 2022), paravertebral EHMs were observed in two asymptomatic patients out of currently 43 adult patients with BT registered at the Adult Hemoglobinopathy Outpatient Unit of the University Hospital Essen, Germany. In one of them, a paravertebral EHM was diagnosed more than 10 years prior to referral. Throughout observation time, treatment with luspatercept was associated with a clinically significant reduction in transfusion burden while allowing to maintain a baseline hemoglobin concentration of ≥10 g/dL aiming to suppress endogenous (ineffective) erythropoiesis associated with BT. Considering the rarity of paravertebral EHMs in BT, luspatercept might potentially represent a novel therapeutic option for these often-serious disease-associated complications. However, appropriate follow-up investigations are recommended to detect (early) treatment failures secondary to an undesired luspatercept-associated erythroid expansion.

Mitapivat in adult patients with pyruvate kinase deficiency receiving regular transfusions (ACTIVATE-T): a multicentre, open-label, single-arm, phase 3 trial

Mitapivat, an oral activator of pyruvate kinase (PK) in red blood cells (RBCs), has shown significant improvements in haemoglobin and haemolysis among patients with pyruvate kinase deficiency who were not receiving regular transfusions. We aimed to evaluate the efficacy and safety of mitapivat in adults with pyruvate kinase deficiency receiving regular transfusions. ACTIVATE-T was an open-label, single-arm, phase 3 trial conducted in 20 centres across Europe, North America, and Asia. Eligible participants were adults (aged ≥18 years) with a clinical laboratory confirmation of pyruvate kinase deficiency receiving regular transfusions (at least six episodes in the previous year). Participants received oral mitapivat during a 16-week dose-optimisation period (5 mg, 20 mg, 50 mg twice daily) and 24-week fixed-dose period. The primary endpoint was a reduction in transfusion burden (≥33% reduction in number of RBC units transfused during the fixed-dose period, compared with the participant's individual historical transfusion burden, standardised to 24 weeks). Efficacy and safety were assessed in all participants who received at least one dose of mitapivat. This trial is registered with ClinicalTrials.gov, NCT03559699, and is complete. Between June 26, 2018, and Feb 4, 2020, 27 participants (20 [74%] female and seven [26%] male; 20 [74%] White, three [11%] Asian, and four [15%] not reported) were enrolled and received at least one dose of mitapivat. Median duration of exposure to mitapivat was 40·3 weeks (IQR 40·0-41·3). A reduction in transfusion burden by at least 33% was found in ten (37%) participants (95% CI 19-58; p=0·0002). The most common treatment-emergent adverse events were increase in alanine aminotransferase (ten [37%] participants), headache (ten [37%]), increase in aspartate aminotransferase (five [19%]), fatigue (five [19%]), and nausea (five [19%]). Two grade 3 treatment-emergent adverse events were related to study treatment: joint swelling (one participant [4%]) and an increase in aspartate aminotransferase (one participant [4%]). Three participants had serious treatment-emergent adverse events, none related to the study treatment: increased blood triglycerides, ovarian cyst, and renal colic (each in one participant [4%]). No treatment-related deaths were observed. Mitapivat represents a novel therapy that can reduce transfusion burden in some adults with pyruvate kinase deficiency receiving regular transfusions, and is the first disease-modifying agent approved in this disease. Agios Pharmaceuticals.

P1545: DURABILITY OF HEMOGLOBIN RESPONSE AND REDUCTION IN TRANSFUSION BURDEN IS MAINTAINED OVER TIME IN PATIENTS WITH PYRUVATE KINASE DEFICIENCY TREATED WITH MITAPIVAT IN A LONG-TERM EXTENSION STUDY

Background: Mitapivat (AG-348), a first-in-class, oral, allosteric activator of red blood cell (RBC) PK enzyme, demonstrated improvements in hemoglobin (Hb) and markers of hemolysis and hematopoiesis (ACTIVATE, NCT03548220), and reduction in transfusion burden (ACTIVATE-T, NCT03559699) in patients (pts) with PK deficiency. Aims: Report data from ACTIVATE, ACTIVATE-T, and their long-term extension (LTE) study (NCT03853798). Methods: In the double-blind, placebo (PBO)-controlled ACTIVATE study (12-week [wk] dose-optimization period [5/20/50 mg twice daily [BID]]; 12-wk fixed-dose period [FDP]), 80 pts (≥18 years [yrs]) with PK deficiency who were not regularly transfused (≤4 transfusion episodes in prior yr; none in prior 3 months [mos]) were randomized 1:1 to mitapivat or PBO. Primary endpoint was Hb response (≥1.5 g/dL increase in Hb from baseline [BL] sustained at ≥2 assessments at Wks 16, 20, and 24 in the FDP). In the single-arm, open-label ACTIVATE-T study (16-wk dose-optimization period [5/20/50 mg BID]; 24-wk FDP), 27 pts (≥18 yrs) with PK deficiency who were regularly transfused (≥6 transfusion episodes in prior yr) were treated with mitapivat. Primary endpoint was transfusion response (≥33% reduction in number of RBC units transfused during the FDP, compared with pt’s individual historical transfusion burden standardized to 24 wks). Secondary endpoint was achieving transfusion-free status (no transfusions in FDP). Pts who completed the FDP of ACTIVATE/ ACTIVATE-T were eligible to continue in the LTE, where all received mitapivat. The ACTIVATE/LTE analysis assessed duration of Hb response in 2 cohorts: 1) pts assigned to mitapivat who achieved a Hb response and continued to the LTE (mitapivat-to-mitapivat arm [M/M]); 2) pts assigned to PBO who switched to mitapivat in the LTE (PBO-to-mitapivat arm [P/M]) and then met Hb response criteria. The ACTIVATE-T/LTE analysis assessed transfusion response in the LTE, and transfusion-free duration among pts from ACTIVATE-T who achieved transfusion-free status. Results: In ACTIVATE, 40% of pts treated with mitapivat (N=40) achieved a Hb response; in the LTE, pts randomized to PBO in ACTIVATE showed similar improvements in Hb levels after switching to mitapivat. These improvements were sustained with continued treatment (Figure 1a). All 16 pts assigned to mitapivat in ACTIVATE who achieved Hb responses continued to the LTE; 15 M/M pts were evaluable for Hb assessment in the LTE. 13/15 M/M pts (86.7%) maintained ≥1.5 g/dL Hb increase from BL up to 19.5 mos at all time points; 2 pts maintained ≥1 g/dL Hb increase from BL at all time points. None of the pts assigned to PBO in ACTIVATE (N=40) had a Hb response; 17 P/M pts had sufficient time (24 wks of treatment) in the LTE for Hb response assessment. 6/17 pts (35%) achieved Hb responses in the LTE, and all maintained Hb responses during follow-up. In ACTIVATE-T (N=27), 37% of pts achieved a transfusion response and 22% of pts achieved transfusion-free status. In the LTE, 9 pts (33.3%) met criteria for a transfusion response. All 6 pts who achieved transfusion-free status in ACTIVATE-T maintained the status in the LTE up to 21.9 mos (Figure 1b). One additional pt, who met the primary endpoint, but was not transfusion free in ACTIVATE-T, did not receive any transfusions in the LTE. Image:Summary/Conclusion: Mitapivat improved Hb and reduced transfusion burden in pts with PK deficiency over time, demonstrating the consistency and long-term durability of treatment with mitapivat.

Long-term safety and erythroid response with luspatercept treatment in patients with β-thalassemia.

β-thalassemia is a hereditary blood disorder resulting in ineffective erythropoiesis and anemia. Management of anemia with regular blood transfusions is associated with complications including iron overload. Here, we report long-term safety and efficacy results of the first clinical study of luspatercept in β-thalassemia, initiated in 2013, enrolling adults with both nontransfusion-dependent (NTD) and transfusion-dependent (TD) β-thalassemia. The objective was to report long-term safety data, for up to 5 years of treatment, for 64 patients with TD or NTD β-thalassemia, and long-term efficacy data for a subset of 63 patients with β-thalassemia who received high-dose luspatercept (0.6-1.25 mg/kg): 31 NTD and 32 TD patients. The study was a phase 2, noncontrolled, open-label trial comprising a dose-finding base phase and a 5-year extension phase. Endpoints include safety; erythroid response over a continuous 12-week period [NTD: hemoglobin increase from baseline ⩾1.0 or ⩾1.5 g/dl; TD: red blood cell (RBC) transfusion burden reduction, ⩾20%, ⩾33%, or ⩾50%]; and changes in biomarkers of ineffective erythropoiesis, iron metabolism parameters, Functional Assessment of Chronic Illness Therapy - Fatigue (FACIT-F) scores, and 6-min walking distance. Median duration of luspatercept exposure for NTD and TD patients was 910 days (range, 40-1850) and 433 days (range, 21-1790), respectively. Seventeen of 31 (54.8%) NTD patients achieved a mean hemoglobin increase of ⩾1.5 g/dl and 19 of 32 (59.4%) TD patients achieved ⩾50% reduction in RBC transfusion burden, during any continuous 12-week period. Median cumulative duration of response was 1126 days (range, 127-1790) for NTD patients and 909 days (range, 87-1734) for TD patients. The most common treatment-related adverse events of any grade were bone pain, headache, and myalgia. Long-term assessment of patients with β-thalassemia showed luspatercept was associated with sustained increases in hemoglobin levels in NTD patients and sustained transfusion burden reductions in TD patients. (ClinicalTrials.gov Identifiers: NCT01749540 and NCT02268409). Long-term safety and erythroid response with luspatercept treatment in patients with β-thalassemia Background: β-thalassemia is a genetic blood disorder caused by mutations in the β-globin gene, which encodes one of the proteins that comprise hemoglobin, a key constituent of red blood cells. Patients with β-thalassemia experience anemia, the main treatment for which is blood transfusions. Long-term repeated blood transfusions lower patients' quality of life, use hospital resources, and the resulting accumulation of excess iron can cause organ failure and decrease life expectancy. The severity of the anemia experienced by patients with β-thalassemia varies; patients with transfusion-dependent β-thalassemia require regular blood transfusions, compared with those with nontransfusion-dependent β-thalassemia who require infrequent transfusions, or even none at all, to manage their symptoms. Luspatercept (Reblozyl®) is an agent that stimulates the production of red blood cells and is used to treat anemia caused by β-thalassemia. However, the long-term effects of luspatercept treatment on patients with β-thalassemia are not known.Objective: In this study, we report the long-term safety of luspatercept in 64 adult patients with either transfusion-dependent or nontransfusion-dependent β-thalassemia, and the long-term efficacy of high-dose luspatercept (0.6-1.25 mg/kg) in a subset of 63 patients.Results: The average time period that patients were treated with luspatercept was 910 days for nontransfusion-dependent β-thalassemia and 433 days for transfusion-dependent β-thalassemia. We report that in patients with nontransfusion-dependent β-thalassemia, luspatercept treatment was associated with sustained increases, just over 3 years, in hemoglobin levels. Likewise, in transfusion-dependent β-thalassemia, luspatercept treatment was associated with a sustained reduction, 2.5 years, in the amount of blood transfusion required to manage their anemia. Long-term treatment with luspatercept was not associated with any new side effects compared with previous short-term treatment studies. The most common side effects were headache (27 patients), bone pain (20 patients), and muscle pain (14 patients) with more than 90% of these patients experiencing these side effects as mild severity.Conclusion: The results of this study show that in patients with either transfusion-dependent or nontransfusion-dependent β-thalassemia, luspatercept provides lasting reduction in anemia with mostly mild and predictable side effects.

Durability of Hemoglobin Response and Reduction in Transfusion Burden Is Maintained over Time in Patients with Pyruvate Kinase Deficiency Treated with Mitapivat in a Long-Term Extension Study

Durability of Hemoglobin Response and Reduction in Transfusion Burden Is Maintained over Time in Patients with Pyruvate Kinase Deficiency Treated with Mitapivat in a Long-Term Extension Study

Innovative Adaptive Study Design in Transfusion-Dependent Beta-Thalassemia: Bayesian Design with Concurrent Randomization and Borrowing from Historical Data

BackgroundClinical development of new therapies in transfusion-dependent beta-thalassemia has several challenges. Patient enrollment in rare diseases requires multi-center multi-country studies, and the lack of reliable surrogate endpoint for dose selection requires powering for clinical endpoints usually used in Phase 3 trials. An acceptable endpoint from a regulatory perspective which is based on responders analysis, such as proportion of patients experiencing ≥50% reduction in Red Blood Cell (RBC) transfusion burden and a reduction of ≥2 units, requires 12 weeks screening period to establish baseline transfusion burden for reliable comparison. Importantly, higher randomization ratio of treatment:placebo can improve patients' motivation to enroll into a trial, but it is less statistically efficient and requires higher sample size.We designed a Phase-2b, double-blind, randomized, placebo controlled, multi-center study with Vamifeport (NCT04938635) to assess the efficacy and safety of multiple doses of a new therapy in adults with transfusion-dependent beta-thalassemia. The proposed design follows the Bayesian framework with borrowing from published historical control data. The historical control data is used to construct an informative prior for the control arm to reduce the burden of patients randomized to a control arm and improve the trial's efficiency in performing dose selection.Study Design and MethodsAdults (18 to 65 y.o.) with documented diagnosis of β-thalassemia or hemoglobin E / β-thalassemia will be randomized to three doses of the investigational drug or placebo plus best supportive care. RBC transfusion dependence is defined as at least 6 RBC Units in the 24 weeks prior to randomization and no transfusion-free period for ≥35 days during that period. The primary endpoint is the proportion of patients experiencing ≥33% reduction of RBC units from baseline and a reduction of ≥2 units assessed from week 13 to week 24. The key secondary endpoints include proportion of patients experiencing ≥33% reduction from week 37 to week 48; proportion of patients experiencing ≥50% reduction over any consecutive 12-week interval from week 1 to week 48 and the mean change from baseline in RBC transfusions (units) from week 13 to week 24. The primary and key-secondary analysis will be conducted in a hierarchical fashion to account for multiplicity.We proposed a Bayesian design with the use of noninformative, or weakly informative, priors for the active dose arms while using a robustified informative prior for the control arm. Historical control data will be “borrowed” in an informative prior for the control arm rate from the Phase 3 trial - BELIEVE. The robustification is required in order to control the level of borrowing depending on the level of prior-data conflict.Prior-data conflict can arise from multiple sources like population heterogeneity between the historical and current study. Therefore, the selection of historical data (BELIEVE trial) addresses similarity in inclusion / exclusion criteria, standard of care etc. The robustification of the informative prior does not take into account prior-data conflict in terms of population or study characteristics but directly focuses on the informative prior of the parameter of interest and the corresponding likelihood of the current data. For example, in the BELIEVE study, out of 112 patients randomized to the control arm, 5 patients (4.5%) had a ≥33% reduction in transfusion burden over 24 weeks. A prior-data conflict may arise if the Phase-2b trial of interest here, suggests that the proportion is substantially different that 4.5% and this can inflate the frequentist Type-I or Type-II error rates examined via simulations.We evaluated Type-I error rates of the proposed design with 5000 Monte-Carlo runs for each scenario of the response rates. Using informative prior with no prior-data conflict the type-I error with no robustification is ≈ 2.4%. As the prior-data conflict increases, without robustification, the type-I error cannot be controlled. However, with a robustification weight of 0.5 the type-I errors can be controlled in line with regulatory requirements.DiscussionA proposed Bayesian design with robustified informative prior for the control arm helps reduce patients' burden of randomization to control arm and reduce overall sample size for a rare disease trial when recruitment and trial duration are challenging. DisclosuresMuehlemann: Vifor Pharma AG: Consultancy. Mukherjee: Vifor Pharma AG: Consultancy. Taher: Bristol Myers Squibb: Consultancy, Research Funding; Vifor Pharma: Consultancy, Research Funding; Agios Pharmaceuticals: Consultancy; Ionis Pharmaceuticals: Consultancy, Research Funding; Novartis: Consultancy, Research Funding. Gudmundsdottir: Vifor Pharma AG: Current Employment. Morin: Vifor Pharma AG: Current Employment. Richard: Vifor Pharma AG: Current Employment.