Background: Hodgkin lymphoma (HL) is a rare disease that commonly occurs in adolescents and young adults (AYAs) which is typically defined as 15 to 39 years. Given their young age at presentation, key factors in treatment selection include a high cure rate and limiting long-term toxicities. Brentuximab vedotin (Adcetris®; A) is a CD30-directed ADC approved in combination with doxorubicin, vinblastine, and dacarbazine chemotherapy (A+AVD) for adults with previously untreated stage III/IV cHL based on results from the phase 3 ECHELON-1 trial. Recent 5-year data demonstrated a significantly improved PFS per investigator (INV) vs doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD) (HR, 0.69; 95% CI, 0.54–0.9; P = 0.003) (Straus 2020). Here we describe key efficacy and safety results for AYA pts enrolled in ECHELON-1. Methods: ECHELON-1 (N = 1334) is a global, open-label, multicenter, randomized trial of pts with previously untreated stage III/IV cHL. A total of 771 AYAs (57.8%) received either A+AVD (n = 396) or ABVD (n = 375) with a PET scan after cycle 2 (PET2). An analysis of PFS (time from randomization to progression or death from any cause) per INV was conducted. Results: After a median follow-up of 60.7 months (95% CI, 60.4-61.0), there was a 36% reduction in the risk of progression or death in AYAs receiving A+AVD vs ABVD (HR 0.64; 95% CI, 0.45-0.92; P = 0.013) with a 5-year PFS of 86.3% vs 79.4%, respectively, similar to the ITT population. The PFS benefit of A+AVD vs ABVD was independent of PET2 status; PET2 positivity (Deauville 4-5) was 6% and 8%, respectively. On the A+AVD arm, 81 AYAs (20%) had at least 1 subsequent anticancer therapy vs 96 AYAs (26%) on the ABVD arm; 26 AYAs (7%) received subsequent high dose chemotherapy and autologous stem cell transplant vs 32 AYAs (9%) on the A+AVD and ABVD arms, respectively. Resolution or improvement of peripheral neuropathy (PN) were similar in both arms; 224 AYAs (88%) on the A+AVD had resolution or improvement of PN vs 133 AYAs (89%) on the ABVD arm. Ongoing PN was predominantly Gr 1 (62%) and Gr 2 (26%), with 8 AYAs (13%) on the A+AVD arm and 1 AYA (5%) on the ABVD arm reporting ongoing Gr 3 PN. Finally, 7 AYAs (1.8%) and 5 AYAs (1.4%) on the A+AVD and ABVD arms, respectively, reported a secondary malignancy. Subsequent pregnancies were reported in female pts (44 A+AVD; 26 ABVD) and partners of male pts (31 A+AVD; 30 ABVD). No stillbirths were reported. All but 1 pt in each arm was < 40. Conclusions: Consistent with the ITT population, AYAs treated with A+AVD compared to ABVD had a durable PFS benefit at this significant 5-year milestone. No impact on the rate of secondary malignancies and a numerically greater number of pregnancies were observed, outcomes of interest to AYAs. Additionally, the majority of PN events improved or resolved over time. A+AVD should be considered a treatment option for AYAs with stage III/IV cHL. Clinical trial information: NCT01712490