Dose proportionality of serum elritercept PK parameters in part 1 (SAD). Cmax values over dose (A) and AUC values over dose (B) demonstrating a proportional increase in systemic exposure with increasing dose over the dose range of 0.5 to 4.5 mg/kg. The 0.05 mg/kg cohort was not included due to only 1 participant demonstrating measurable serum levels. Note, concentrations reported as below the LLOQ (LLOQ = 1.17 μg/mL) were set to 0 for the calculation of summary statistics.