This is a phase II/III multicenter, prospective, randomized, placebo-controlled, double-blind, parallel-group clinical trial with an adaptive design (flexible group sequential design with adaptive dose selection) in subjects with PPS.~This study will consist of two stages. The first stage (Stage 1) is for dose selection, and the second stage (Stage 2) is to establish the superiority (efficacy confirmation) of Flebogamma 5% DIF and for overall safety analysis. Stage 1 is a 3-arm evaluation of 2 dose levels of Flebogamma 5% DIF intravenous immunoglobulin (IVIG) 1 g/kg and 2 g/kg of body weight) and placebo randomized in a 1:1:1 ratio. Flebogamma 5% DIF 2 g/kg of body weight will be administered over 2 consecutive days (IVIG 1g/kg on Day 1 and IVIG 1g/kg on Day 2) (IVIG 2 g/kg arm), Flebogamma 5% DIF 1 g/kg of body weight plus the equivalent volume of Normal Saline Solution (20 mL/kg of body weight) (IVIG 1 g/kg arm), or a total dose of 40 mL/kg of body weight Normal Saline Solution (equivalent volume of the 2 g/kg of body weight Flebogamma 5% DIF infusions) (placebo arm) will be administered over 2 consecutive days every 4 weeks during a 52-week treatment period. At the end of Stage 1, an interim analysis will be conducted and 1 of the 2 Flebogamma 5% DIF doses will be selected based on predefined criteria to be used for Stage 2.~Stage 2 will consist of 2 treatment arms, the selected dose of Flebogamma 5% DIF from Stage 1 and Normal Saline Solution (40 mL/kg of body weight). Study drug will be administered over 2 consecutive days every 4 weeks during a 52-week treatment period. During Stage 2, the selected dose of Flebogamma 5% DIF and Normal Saline Solution will be administered in the same manner as in Stage 1, including administering the total dose for both treatment arms at a volume equivalent to that for the IVIG 2 g/kg arm, regardless of the selected dose.~Primary efficacy endpoint will be:~• Physical performance 2MWD from baseline to the end of the treatment period (at End of Treatment Visit -Week 52).
This is a multicenter, prospective, randomized, placebo-controlled, double-blind, parallel group clinical trial with adaptive dose selection in subjects with post-polio syndrome (PPS).~The main purpose of this study is to select a dose of Flebogamma 5% DIF and confirm the efficacy of the selected Flebogamma® 5% DIF dose by assessing physical performance, as measured by Two-Minute Walk Distance (2MWD) test.~The study will consist of 2 stages, with each stage consisting of a screening period (up to 4 weeks), a treatment period (52 weeks), and a follow-up period (24 weeks).