This study is about testing a treatment called ELA026 for a rare disease called secondary hemophagocytic lymphohistiocytosis (sHLH). sHLH is a serious condition where the immune system goes out of control. The study has two parts. Part 1 is already closed and was for testing safety and how the drug works. It included children and adults who are either new to treatment or who have had a relapse. Part 2 is ongoing and is for people newly diagnosed with sHLH, both kids and adults. It aims to see how well the drug works and its safety. Participation involves taking ELA026 through an IV (a needle in the vein) or a shot under the skin.

• Part 2 is currently recruiting participants.
• Participants need to meet specific criteria to join.
• The study involves medical tests and taking ELA026 safely.