Istiratumab is an anti-insulin like growth factor 1 receptor (IGF-1R) / anti-human epidermal growth factor receptor 3 (HER3 or Erbb3) bispecific monoclonal antibody optimized to dampen IGF-1R and HER3 signalisation, while inducing both receptors degradation and overcoming therapy resistance usually limiting PI3K pathway inhibition strategies. Holding the entire intellectual property from MerriMack since 2021, we are in the frame of launching a phase II clinical trial on two rare pediatric indications : Ewing Sarcoma and Rhabdomyosarcoma