RecruitingPhase 2Drug trialFrexalimAB in Preservation of Endogenous insULIN Secretion Compared to Placebo in adUlts and Adolescents on Top of inSulin Therapy (FABULINUS)This is a randomized, parallel group, double-blind Phase 2 study with a 52-week blinded extension evaluating the safety and efficacy of 3 dose levels of frexalimab in comparison with placebo in participants with newly diagnosed T1D on insulin treatment. Study details include: Screening period: at least 3 weeks and up to 5 weeks Double-blind treatment period (104 weeks): * Main treatment period: 52 weeks * Blinded extension: 52 weeks Optional Open Label Extension: 104 weeks Safety follow-up: up to 26 weeks The treatment duration will be up to 104 weeks, the total study duration will be up to 135 weeks.