Objectives of this placebo-controlled study were to assess the safety and tolerability of single dose ANB020 administration in peanut-allergic adult patients and to measure the response during a standardized oral food challenge (OFC) after ANB020 or placebo administration compared to baseline OFCs. On Day 1, fifteen highly allergic adult patients were administered 300 milligrams of ANB020 by IV infusion, and five patients were administered placebo injections. To measure patient response, patients were administered ex vivo whole blood peanut antigen challenges on Day 2 and Day 5 and OFCs on Day 15 and Day 45. The clinical outcomes and cellular responses of patients were analyzed. For patients given ANB020, 67% on Day 15 and 57% on Day 45 passed the OFC; no placebo patients passed on either day. Patients given ANB020 had fewer adverse events (abdominal pain, nasal congestion) compared to placebo patients (abdominal pain, vomiting, nausea, asthma, allergic reaction). The median percentages of IL-4 and IL-9 cells in CD69 T cells were lower for patients given ANB020 compared to patients given placebo at Baseline, Day 2, and Day 5, and higher at Day 15. Peanut-specific and histamine skin test wheal sizes among all patients stayed consistent, except at Day 15 for patients given ANB020, where both wheal sizes decreased to less than 5 mm. Volumes of peanut-specific IgE and total IgE were smaller for patients given ANB020 at Baseline, Day 15, and Day 45. Study results show ANB020 to be potentially helpful in increasing patient tolerability and safety during OFCs.