Background: Adagloxad simolenin (AS) is a therapeutic vaccine comprising the tumor-associated antigen Globo H linked to the carrier protein keyhole limpet hemocyanin (KLH). The KLH provides antigenic immune recognition and T-cell responses. AS is co-administered with a saponin-based adjuvant OBI-821 to induce a humoral response. A phase 2 trial showed that AS/OBI-821 exhibited a trend for superior progression-free survival vs placebo in patients whose breast cancers have higher Globo H expression. Methods: Patients with TNBC (ER/PR < 5%, and HER2-negative) with nonmetastatic disease and either 1) residual invasive disease of ≥1 cm in the breast or ≥1 positive axillary node following neoadjuvant chemotherapy or 2) ≥4 axillary lymph nodes with invasive carcinoma treated with adjuvant chemotherapy are included. Patients are prescreened for Globo H expression using a validated IHC assay (H-score of ≥15). Patients will receive either AS (30 μg) with OBI-821 (100 μg) or volume-matched placebo (1:1), administered as SC injections. Up to 21 SC injections of study treatment (or placebo), will be administered over 100 weeks, given on the following schedule: weekly for 4 doses; every 2 weeks for 4 doses; every 4 weeks for 4 doses; and then every 8 weeks for 9 doses. Patients may terminate treatment due to disease recurrence or unacceptable toxicity, withdrawal of consent, protocol violation, loss to follow-up or death. The primary objective is to determine the effect of AS/OBI-821 treatment on invasive disease-free survival in patients with TNBC at high risk for recurrence. Secondary objectives are to determine the impact of AS/OBI-821 treatment on overall survival, quality of life (QoL), breast cancer-free interval, distant disease-free survival, safety, and tolerability. Imaging and clinical examination will be performed regularly for 5 years. QoL will be assessed using the EORTC Core Quality of Life Questionnaire (QLQ)-C30 plus the EORTC Breast Cancer-specific QLQ-BR23 questionnaire and the European Quality of Life 5 Dimensions 5 Levels (EQ-5D-5L) questionnaire. Adverse events will be graded/recorded as per National Cancer Institute CTCAE v5.0. An estimated 668 subjects will be enrolled, treated for up to 2 years and followed until occurrence of 187 events (invasive disease recurrence or death) or 3 years from last subject randomized. Survival follow-up is for 5 years from randomization of last subject. Clinical trial information: NTC03562637.