Fig 1: Confirmation of luspatercept presence in serum samples. (a) Analysis by SDS‐PAGE and double‐blot (anti‐ActRIIB Sino Biological Inc. 10229‐T20). (b) Analysis by SAR‐PAGE and double‐blot (anti‐ActRIIB Sino Biological Inc. 10229‐T16). (c) Analysis by IEF‐PAGE (2‐10) and single‐blot (biotinylated anti‐ActRIIB R&D systems BAF339). A signal corresponding to the reference luspatercept was present in all samples evaluated post‐administration (D49 to D70) and absent before administration (C1). Positive QC (serum spiked with luspatercept) and negative QC (blank serum) were prepared with the samples and included in the analysis