Luspatercept

12.1 Mechanism of Action Luspatercept-aamt is a recombinant fusion protein that binds several endogenous TGF-β superfamily ligands, thereby diminishing Smad2/3 signaling. In models of β-thalassemia and MDS, luspatercept-aamt decreased abnormally elevated Smad2/3 signaling and improved hematology parameters associated with ineffective erythropoiesis in mice. Luspatercept-aamt promoted erythroid maturation through differentiation and increasing the percentage of late-stage erythroid precursors (normoblasts) in the bone marrow of mice and increased erythroid precursors in humans, thereby increasing erythropoiesis.

1 INDICATIONS AND USAGE REBLOZYL is an erythroid maturation agent indicated for the treatment of: • Anemia in adult patients with beta thalassemia who require regular red blood cell (RBC) transfusions ( 1.1 ). • Anemia without previous erythropoiesis stimulating agent use (ESA-naïve) in adult patients with very low- to intermediate-risk myelodysplastic syndromes (MDS) who may require regular red blood cell (RBC) transfusions ( 1.2 ). • Anemia failing an erythropoiesis stimulating agent and requiring 2 or more RBC units over 8 weeks in adult patients with very low- to intermediate-risk myelodysplastic syndromes with ring sideroblasts (MDS-RS) or with myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T) ( 1.3 ). • Limitations of Use: REBLOZYL is not indicated for use as a substitute for RBC transfusions in patients who require immediate correction of anemia ( 1.4 ). 1.1 Beta Thalassemia REBLOZYL is indicated for the treatment of anemia in adult patients with beta thalassemia who require regular red blood cell (RBC) transfusions. 1.2 Myelodysplastic Syndromes Associated Anemia REBLOZYL is indicated for the treatment of anemia without previous erythropoiesis stimulating agent use (ESA-naïve) in adult patients with very low- to intermediate-risk myelodysplastic syndromes (MDS) who may require regular red blood cell (RBC) transfusions. 1.3 Myelodysplastic Syndromes with Ring Sideroblasts or Myelodysplastic/ Myeloproliferative Neoplasm with Ring Sideroblasts and Thrombocytosis Associated Anemia REBLOZYL is indicated for the treatment of anemia failing an erythropoiesis stimulating agent and requiring 2 or more red blood cell units over 8 weeks in adult patients with very low- to intermediate-risk myelodysplastic syndromes with ring sideroblasts (MDS-RS) or with myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T). 1.4 Limitations of Use REBLOZYL is not indicated for use as a sub

2 DOSAGE AND ADMINISTRATION • The recommended starting dose is 1 mg/kg once every 3 weeks by subcutaneous injection ( 2.1 , 2.2 ). • Review hemoglobin (Hgb) results prior to each administration ( 2.1 , 2.2 ). • See full prescribing information for preparation and administration instructions ( 2.3 ). 2.1 Recommended Dosage for Beta Thalassemia The recommended starting dose of REBLOZYL is 1 mg/kg once every 3 weeks by subcutaneous injection for patients with beta thalassemia. Prior to each REBLOZYL dose, review the patient’s hemoglobin and transfusion record. Titrate the dose based on responses according to Table 1. Interrupt treatment for adverse reactions as described in Table 2. Discontinue REBLOZYL if a patient does not experience a decrease in transfusion burden after 9 weeks of treatment (administration of 3 doses) at the maximum dose level or if unacceptable toxicity occurs at any time. If a planned administration of REBLOZYL is delayed or missed, administer REBLOZYL as soon as possible and continue dosing as prescribed, with at least 3 weeks between doses. Dose Modifications for Response Assess and review hemoglobin results prior to each administration of REBLOZYL. If an RBC transfusion occurred prior to dosing, use the pretransfusion hemoglobin for dose evaluation. If a patient does not achieve a reduction in RBC transfusion burden after at least 2 consecutive doses (6 weeks) at the 1 mg/kg starting dose, increase the REBLOZYL dose to 1.25 mg/kg. Do not increase the dose beyond the maximum dose of 1.25 mg/kg. In the absence of transfusions, if hemoglobin increase is greater than 2 g/dL within 3 weeks or the predose hemoglobin is greater than or equal to 11.5 g/dL, reduce the dose or interrupt treatment with REBLOZYL as described in Table 1. Dose level modifications for response are provided in Table 1. Table 1: Beta Thalassemia - REBLOZYL Dose Titration for Response * Do not increase the dose if the patient is experiencing an adverse reaction as described in Table 2. REBLOZYL Dosing Recommendation* Starting Dose • 1 mg/kg every 3 weeks Dose Increases for Insufficient Response at Initiation of Treatment No reduction in RBC transfusion burden after at least 2 consecutive doses (6 weeks) at the 1 mg/kg starting dose • Increase the dose to 1.25 mg/kg every 3 weeks No reduction in RBC transfusion burden after 3 consecutive doses (9 weeks) at 1.25 mg/kg • Discontinue treatment Dose Modifications for Predose Hemoglobin Levels or Rapid Hemoglobin Rise Predose hemoglobin is greater than or equal to 11.5 g/dL in the absence of transfusions • Interrupt treatment • Restart when the hemoglobin is no more than 11 g/dL Increase in hemoglobin greater than 2 g/dL within 3 weeks in the absence of transfusions and • current dose is 1.25 mg/kg • current dose is 1 mg/kg • current dose is 0.8 mg/kg • current dose is 0.6 mg/kg • Reduce dose to 1 mg/kg • Reduce dose to 0.8 mg/kg • Reduce dose to 0.6 mg/kg • Discontinue treatment Dose Modifications for Toxicity For patients experiencing Grade 3 or higher adverse reactions, modify treatment as described in Table 2. Table 2: Beta Thalassemia - REBLOZYL Dosing Modifications for Adverse Reactions * Grade 1 is mild, Grade 2 is moderate, Grade 3 is severe, and Grade 4 is life-threatening. REBLOZYL Dosing Recommendation* Grade 3 or 4 hypersensitivity reactions • Discontinue treatment Other Grade 3 or 4 adverse reactions • Interrupt treatment • Restart when the adverse reaction resolves to no more than Grade 1 Extramedullary hematopoietic (EMH) masses causing serious complications • Discontinue treatment 2.2 Recommended Dosage for Myelodysplastic Syndromes Associated Anemia The recommended starting dosage of REBLOZYL is 1 mg/kg once every 3 weeks by subcutaneous injection for the treatment of anemia of MDS. Prior to each REBLOZYL dose, review the patient’s hemoglobin and transfusion record. Titrate the dose based on responses according to Table 3. Interrupt treatment for adverse reactions as described in Table 4. Discontinue REBLOZYL if a patient does not experience a decrease in transfusion burden including no increase from baseline hemoglobin after 9 weeks of treatment (administration of 3 doses) at the maximum dose level (1.75 mg/kg), or if unacceptable toxicity occurs at any time. If a planned administration of REBLOZYL is delayed or missed, administer REBLOZYL as soon as possible and continue dosing as prescribed, with at least 3 weeks between doses. Dose Modifications for Response Assess and review hemoglobin results prior to each administration of REBLOZYL. If an RBC transfusion occurred prior to dosing, use the pretransfusion hemoglobin for dose evaluation. If a patient is not RBC transfusion-free after at least 2 consecutive doses (6 weeks) at the 1 mg/kg starting dose, increase the REBLOZYL dose to 1.33 mg/kg (Table 3). If a patient is not RBC transfusion-free after at least 2 consecutive doses (6 weeks) at the 1.33 mg /kg dose level, increase the REBLOZYL dose to 1.75 mg/

6 ADVERSE REACTIONS The following clinically significant adverse reactions are described elsewhere in the labeling: • Thrombosis/Thromboembolism [see Warnings and Precautions ( 5.1 )] • Hypertension [see Warnings and Precautions ( 5.2 )] • Extramedullary Hematopoietic Masses [see Warnings and Precautions ( 5.3 )] The most common (>10%) adverse reactions were fatigue, headache, musculoskeletal pain, arthralgia, dizziness/vertigo, nausea, diarrhea, cough, abdominal pain, dyspnea, COVID-19, edema peripheral, hypertension, and hypersensitivity ( 6.1 ). To report SUSPECTED ADVERSE REACTIONS, contact Bristol-Myers Squibb at 1-888-423-5436 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The data in the WARNINGS AND PRECAUTIONS reflect exposure to REBLOZYL as a single agent administered across a range of doses (0.125 mg/kg to 1.75 mg/kg) in 571 patients in 4 trials. Beta Thalassemia The safety of REBLOZYL in patients with beta thalassemia was evaluated in the BELIEVE trial [see Clinical Studies ( 14.1 )] . Key eligibility criteria included adult patients with beta thalassemia (with the exception of patients with hemoglobin S or alpha-thalassemia disease) without major organ damage or recent DVT stroke and platelet counts less than or equal to 1000 x 10 9 /L. Patients received a starting dose of REBLOZYL 1 mg/kg subcutaneous injection every 3 weeks. Overall, 53% of patients had their dose increased to 1.25 mg/kg (46% REBLOZYL, n = 223) or placebo (66%, n = 109). The median duration of treatment was similar between the REBLOZYL and placebo arms (63.3 weeks vs. 62.1 weeks, respectively). Per protocol, patients in the REBLOZYL and placebo arms were to remain on therapy for at least 48 weeks in the double-blind phase of the trial. Among patients receiving REBLOZYL, 94% were exposed for 6 months or longer and 72% were exposed for greater than one year. The median age of patients who received REBLOZYL was 30 years (range: 18, 66); 59% female; 54% White and 36% Asian. Serious adverse reactions occurred in 3.6% of patients on REBLOZYL. Serious adverse reactions reported in 1% of patients were cerebrovascular accident and deep vein thrombosis. A fatal adverse reaction occurred in one patient treated with REBLOZYL who died due to an unconfirmed case of AML (M6). Permanent discontinuation due to an adverse reaction (Grades 1-4) occurred in 5.4% of patients who received REBLOZYL. Most frequent adverse reactions requiring permanent discontinuation in patients who received REBLOZYL included arthralgia (1%), back pain (1%), bone pain (<1%), and headache (<1%). Dosage reductions due to an adverse reaction occurred in 2.7% of patients who received REBLOZYL. Most frequent adverse reactions requiring dosage reduction in >0.5% of patients who received REBLOZYL included hypertension and headache. Dosage interruptions due to an adverse reaction occurred in 15.2% of patients who received REBLOZYL. Most frequent adverse reactions requiring dosage interruption in >1% of patients who received REBLOZYL included upper respiratory tract infection, ALT increase, and cough. The most common adverse reactions (at least 10% for REBLOZYL and 1% more than placebo) were headache (26%), bone pain (20%), arthralgia (19%), fatigue (14%), cough (14%), abdominal pain (14%), diarrhea (12%), and dizziness (11%). Table 6 summarizes the adverse reactions in BELIEVE. Table 6: Adverse Drug Reactions (>5%) in Patients with Beta Thalassemia Receiving REBLOZYL with a Difference Between Arms of 1% in BELIEVE Trial Body System REBLOZYL (N=223) Placebo (N=109) Adverse Reaction All Grades n (%) Grades ≥3 a n (%) All Grades n (%) Grades ≥3 n (%) a Limited to Grade 3 reactions with the exception of 4 events of Grade 4 hyperuricemia. b Grouped term includes abdominal pain and abdominal pain upper. c Grouped term includes essential hypertension, hypertension, and hypertensive crisis. Musculoskeletal and connective tissue disorders Bone Pain 44 (20) 3 (1) 9 (8) 0 (0) Arthralgia 43 (19) 0 (0) 13 (12) 0 (0) Infections and infestation Influenza 19 (9) 0 (0) 6 (6) 0 (0) Viral Upper Respiratory Infection 14 (6) 1 (0.4) 2 (2) 0 (0) Nervous system disorders Headache 58 (26) 1 (<1) 26 (24) 1 (1) Dizziness 25 (11) 0 (0) 5 (5) 0 (0) General disorders and administration site conditions Fatigue 30 (14) 0 (0) 14 (13) 0 (0) Gastrointestinal disorders Abdominal Pain b 31 (14) 0 (0) 13 (12) 0 (0) Diarrhea 27 (12) 1 (<1) 11 (10) 0 (0) Nausea 20 (9) 0 (0) 6 (6) 0 (0) Vascular disorders Hypertension c 18 (8) 4 (2) 3 (3) 0 (0) Metabolism and nutrition disorders Hyperuricemia 16 (7) 6 (3) 0 (0) 0 (0) Respiratory, thoracic and mediastinal disorders Cough 32 (14) 0 (0) 12 (11) 0 (0) Clinically relevant adv