Sustained Unresponsiveness (SU) to Cashew Nut Protein Following Oral Allergen-Specific Immunotherapy

Oral immunotherapy (OIT) is currently recognized as the most effective disease-modifying intervention for IgE-mediated food allergies. The therapeutic objectives of OIT encompass two distinct immunologic outcomes: desensitization and sustained unresponsiveness (SU).

Desensitization refers to a reversible state of increased clinical tolerance to the allergen, dependent on continuous antigen exposure. In contrast, sustained unresponsiveness-considered the optimal endpoint-describes the maintenance of non-reactivity to the allergen following a defined period of OIT discontinuation.

The present study constitutes a long-term follow-up of participants previously enrolled in the randomized controlled trial (RCT) "Efficacy of Cashew Nut Protein Immunotherapy: A Protocol of a Single-Center Randomized Controlled Trial in the Pediatric Population", NCT06328504. Participants who completed the initial treatment phase will be invited to participate in this extended evaluation.

Study Procedures

Following an additional 8 months (±3 weeks) of continued cashew nut protein OIT, eligible participants will undergo a comprehensive in-hospital evaluation, including:

Skin prick testing (SPT) with commercial extracts of peanut, walnut, hazelnut, pistachio, cashew, almond, and native tests with cashew flour, peanut butter, and fresh nuts listed above

Laboratory assessments (e.g., specific IgE, IgG4), and

A standardized open oral food challenge (OFC) to cashew nut protein to assess clinical desensitization.

Participants who demonstrated confirmed desensitization (i.e., negative OFC) after 3 months of OIT during the initial trial phase will proceed to the next phase of the study protocol without repeating an OFC prior to OIT cessation. Only those with previously confirmed desensitization will be eligible for assessment of sustained unresponsiveness.

Following a 4-week discontinuation period (i.e., OIT treatment break), these participants will undergo a second OFC to evaluate sustained unresponsiveness to cashew nut protein.

Participants who did not achieve desensitization during the initial or extended phases-defined by a positive OFC-will resume cashew nut protein OIT per the established clinical desensitization protocol implemented at the investigational site, irrespective of their initial randomization group.

Statistical Considerations

An interim analysis is planned once 70% of participants have completed the primary outcome assessment. This analysis will be conducted by an independent Data Monitoring Committee (DMC) to ensure participant safety and evaluate preliminary efficacy signals. Statistical inference during interim analysis will be controlled using appropriate alpha-spending functions to maintain the overall Type I error rate.

Inclusion criteria

• Cashew nut allergy confirmed prior to the initiation of immunotherapy
• Completion of the first phase of the study, including achievement of the maintenance dose (1200 mg of cashew nut protein) during immunotherapy
• Provision of informed consent for participation in the study
• Adequate cooperation from the patient and/or their legal guardians

Exclusion criteria

• Severe asthma
• Poorly controlled mild-to-moderate asthma, defined as:

• FEV1 < 80% (below the 5th percentile),
• FEV1/FVC ratio < 75% (below the 5th percentile),
• Hospitalization due to asthma exacerbation within the past 12 months
• Oral, sublingual, or subcutaneous immunotherapy for other allergens during the first year/season of therapy
• Eosinophilic gastrointestinal disorders
• Severe, recurrent episodes of anaphylaxis within the last 6 months
• Chronic illnesses requiring ongoing treatment, including:

• Cardiac conditions
• Epilepsy
• Metabolic disorders
• Diabetes mellitus
• Use of the following medications:

• Daily oral corticosteroid therapy >1 month within the past 12 months
• At least two courses of oral corticosteroids (minimum duration of 7 days each) in the past 12 months
• One course of oral corticosteroids (minimum 7 days) within the past 3 months
• Biologic therapies
• Treatment with β-blockers, ACE inhibitors, or calcium channel blockers
• Pregnancy
• Lack of informed consent for participation
• Lack of cooperation from the patient