1 5 ▁super agon ist ▁complex ▁IL - 1 5 N 7 2 D : IL - 1 5 R α Su / F c ▁that ▁includes ▁an ▁IL - 1 5 ▁mut ant ▁( IL - 1 5 N 7 2 D ) ▁and ▁a ▁dim er ic ▁IL - 1 5 ▁re ceptor ▁α ▁s ush i ▁domain - Ig G 1 ▁F c ▁fusion ▁protein . ▁ ▁A LT - 8 0 3 ▁was ▁given ▁fast ▁track ▁status ▁by ▁the ▁F DA ▁in ▁ 2 0 1 7 ▁and ▁at ▁that ▁time , ▁Ph ase ▁III ▁tri als ▁in ▁bl ad der ▁cancer ▁were ▁being ▁prepared . ▁ ▁R LI - 1 5 ▁ ▁R LI - 1 5 ▁is ▁an ▁fusion ▁protein ▁consisting ▁of ▁the ▁N H 2 - term inal ▁( am ino ▁ac ids ▁ 1 – 7 7 , ▁s ush i +) ▁cy tok ine - binding ▁domain ▁of ▁ ▁IL - 1 5 R α ▁couple d ▁to ▁IL - 1 5 ▁via ▁a ▁ 2 0 - am ino ▁acid ▁flexible ▁linker . ▁This ▁fusion ▁protein , ▁referred ▁to ▁as ▁protein ▁re ceptor - link er - IL - 1 5 ▁( RL I ) ▁acts ▁as ▁an ▁IL - 1 5 ▁super agon ists ▁that ▁has ▁an ▁increased ▁ser um ▁half - life ▁and ▁bi ological ▁activity ▁similar ▁to ▁complex ed ▁IL - 1 5 / IL - 1 5 R α - F c . ▁R LI ▁demonstrated ▁a ▁strong ▁anti