Can a drug that boosts red blood cells help anemia in kidney disease?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: Documentation of Anemia due to CKD * Patients must have a Hb ≤ 9.5 g/dL on two separate occasions within 4 weeks prior to enrollment. * Do not anticipate red cell transfusion within the following 4 weeks and no history of red cell transfusion in three weeks prior to enrollment. * Ferritin ≥100 ng/mL and iron transferrin saturation (TSAT) ≥ 20%. * Serum folate \> 4 ng/mL * Serum vitamin B12 \> 250 pg/mL * Patients may have received iron, B12 and folic acid repletion if initiated \> 6 weeks prior to enrollment. Patients who are already on iron, B12 and folic acid repletion can continue throughout the trial. * TSH, T4 within institutional normal limits. Documentation of Chronic Kidney Disease * Chronic kidney disease defined as a GFR between 30-60 mL/min/1.73m2 for ≥ 3 months calculated by the 2021 CKD-EPI creatinine equation for eGFR, the 2021 CKD-EPI creatinine-cystatin C equation, or creatinine clearance measured by a 24-hour urine collection. Prior Treatment with Erythrocyte Stimulating Agents (ESA) * Eligible patients will not have had recent (within past 3 weeks) erythrocyte stimulating agents (ESA) prior to enrollment unless they are hyporesponsive to ESA therapy. * Patients are eligible if they are either hyporesponsive to ESA therapy or unwilling to accept ESAs. defined by the Kidney Disease Outcomes Quality Initiative (KDOQI) as the inability to achieve/maintain a desired hemoglobin (herein defined as a hemoglobin of \> 9.0 g/dL) using a maximum dose of erythropoietin (450 units/kg/week IV or 300 units/kg/week SQ or the darbepoetin equivalent using the conversion of 45,000 units/week of epoetin = 100 mcg/week of darbepoetin). * Age ≥ 18 * ECOG Performance Status of ≤ 2 * Not Pregnant and Not Nursing Required Organ Function * Adequate hematologic function defined as follows: * Absolute neutrophil count (ANC) ≥ 1,000 cells/mm3 * Platelets ≥ 75,000 cells/mm3 * Adequate hepatic function defined as follows: * Total bilirubin ≤ 1.5 x institutional upper limit of normal (ULN) (patients with known Gilbert's disease who have bilirubin level ≤ 3 x ULN may be enrolled) * AST and ALT ≤3 x institutional ULN * Comorbid Conditions * Patients with a history of a solid organ malignancy can be included if they have been in remission for at least 12 months. Exclusion Criteria: * Evidence of recent (within previous 4 weeks) bleeding including gastrointestinal to explain anemia. * Evidence of hemolysis (LDH ≥ 2 x ULN and haptoglobin below lower limit of normal) * Known diagnosis of myelodysplastic syndrome or any known hematologic malignancy \[not including monoclonal of undetermined significance (MGUS) or monoclonal b-cell lymphocytosis (MBL)\] not in remission * GFR \< 30 mL/min/1.73m2 or on dialysis (no available data for luspatercept on HD) * Acute kidney injury ( ≤ 3 months) * Uncontrolled hypertension: repeated elevations of SBP ≥ 150 mmHg and/or DBP ≥ 100 mmHg despite adequate treatment * Known hemoglobinopathy. * Known inherited or acquired thrombophilia. * History of venous thromboembolism within past 2 years * Cerebral vascular accident within past 2 years * Recent (within 2 years) myocardial infarction * Allergy to luspatercept components