Primary Objective: To determine if 36 months of peanut SLIT as an early intervention in subjects ages 1 to 4 years induces clinical desensitization. The primary outcome of this objective will be a statistically significant difference in challenge scores between the treatment group versus the placebo group during DBPCFC (Double blind placebo controlled food challenge) performed after 36 months of peanut SLIT (desensitization). Challenge scores are measured by the amount of peanut protein participants are able to ingest successfully without symptoms of an allergic reaction. [Time Frame: Baseline, 36 months]

Secondary Objectives:

A secondary outcome of this objective will be a statistically significant difference in the challenge score of the treatment group versus the placebo group during the DBPCFC performed 3 months after discontinuing therapy (tolerance).

To examine the change in immune parameters associated with peanut SLIT and the development of clinical tolerance. Through this objective, the investigators will seek to understand the molecular processes by which SLIT affects the immune system through evaluation of immune mechanisms in relationship to clinical findings of desensitization and tolerance. The investigators will delineate the impact of peanut SLIT on the subsequent cellular and humoral responses to peanut protein.

[Time Frame: Baseline, 39 months]

Peanut allergy is one of the most common food allergies; most children develop this allergy early in life, do not outgrow it and are at risk for severe and life-ending anaphylactic reactions. There is a critical need for a proactive treatment for peanut allergy and the investigators along with others are developing specific types of immunotherapy that will act as disease-modifying therapies.

This SLIT study is a randomized, blinded, placebo-controlled study. The primary outcome of this objective will be a statistically significant difference in challenge scores between the treatment group versus the placebo group during DBPCFC performed after 36 months of peanut SLIT (desensitization). A secondary outcome of this objective will be a statistically significant difference in the challenge score of the treatment group versus the placebo group during the DBPCFC performed 3 months after discontinuing therapy (tolerance).

Upon enrollment into the study, all subjects will undergo a qualifying entry DBPCFC with peanut protein to confirm the diagnosis of peanut allergy and establish a baseline threshold level. Following a positive DBPCFC, each subject will be randomized 1:1 to receive peanut SLIT therapy versus placebo for a duration of 36 months. DBPCFC will be repeated for both active and placebo subjects at 36 months to assess desensitization and at 39 months to assess tolerance.

Outcome variables of interest include peanut specific IgE, IgG, and IgG4, basophil activation, mast cell responses through skin prick testing, and specific T-cell cytokine responses and T regulatory cell (TReg) activation.

COVID-19 SAFETY MEASURES- Reflected in Protocol V4.0- April 2020

In March of 2020, State and National emergencies were declared over the global pandemic coronavirus COVID-19.

As such, any 36 month Desensitization DBPCFC will be postponed while the safety measures surrounding COVID-19 are in place. Subjects who choose to remain in the study will continue on study drug at the maintenance dose level beyond the originally planned 36 months until such time that the Desensitization DBPCFC is conducted.

Subjects who are scheduled to undergo the 39 month Tolerance DBPCFC while the COVID-19 safety measures are in place will have their DBPCFC cancelled. Additional time off of study drug therapy would potentially increase the risk of allergic reaction during the DBPCFC and would not be acceptable.

For subjects whose Desensitization DBPCFC is postponed, a followup visit to review safety and subject dosing diaries would be conducted. This visit would be conducted remotely by telephone. Additional study drug would be sent direct-to-patient as necessary to continue on maintenance dosing. Lab sample collection and mechanistic studies would be deferred and be completed at the time that the Desensitization DBPCFC is completed. The Tolerance DBPCFC would be completed 3 months after the Desensitization DBPCFC is completed.

For subjects whose Tolerance DBPCFC is canceled, an exit visit would be conducted to review safety. The subject would be unblinded to treatment allocation and end of study instructions would be reviewed with the subject.

As the situation is changing daily, we are unable to provide a time frame for extension. We hope to limit the number of subjects who will need to utilize this option and preserve the endpoint data parameters. Previous SLIT studies have not shown any additional risk with peanut SLIT dosing beyond 3 years up to a total of 5 years of dosing.

Inclusion Criteria:

• Written informed consent from participant's parent/guardian.
• Age 12-48 months of either sex, any race, any ethnicity.
• A peanut allergy diagnosis with a convincing clinical history of peanut allergy and a serum peanut-specific IgE [UniCAP] > 0.35 kUA/L AND a positive skin prick test to peanut (>3 mm than the negative control) OR are sensitized to peanut (based on a serum IgE [UniCAP] to peanut of > 5 kUA/L) AND a positive skin prick test to peanut (> 3 mm than the negative control) and no known history of ingestion of peanut.
• A positive DBPCFC to 1000 mg of peanut at enrollment.

Exclusion Criteria:

• History of severe anaphylaxis to peanut, defined as hypoxia, hypotension, or neurologic compromise (cyanosis or peripheral capillary oxygen saturation (SpO2) < 92% at any stage, hypotension, confusion, collapse or loss of consciousness).
• Participation in any interventional study for the treatment of food allergy in the past 6 months.
• Known oat, wheat, or glycerin allergy.
• Eosinophilic or other inflammatory (e.g. celiac) gastrointestinal disease.
• Severe asthma (2007 NHLBI Criteria Steps 5 or 6 - Appendix 2).
• Inability to discontinue antihistamines for skin testing and DBPCFCs.
• Use of omalizumab or other non-traditional forms of allergen immunotherapy (e.g., oral or sublingual) or immunomodulator therapy (not including corticosteroids) or biologic therapy within the past year.
• Use of beta-blockers (oral), angiotensin-converting enzyme (ACE) inhibitors, angiotensin-receptor blockers (ARB) or calcium channel blockers.
• Significant medical condition (e.g., liver, kidney, gastrointestinal, cardiovascular, hematologic, or pulmonary disease) which would make the subject unsuitable for induction of food reactions.

Adverse event data was collected beginning with completion of the qualifying DBPCFC and enrollment in the study through the completion of the tolerance DBPCFC at the 39 month study time point.