Part A Main Inclusion Criteria:
1. Capable of giving signed informed consent.
2. Subject who has a signed and dated Informed Consent Form (ICF).
3. Subject must be 18 to 50 years inclusive, at the time of signing the ICF.
4. Male or female.
5. Female subjects who are not of childbearing potential (or females of childbearing potential who agree to comply with the contraceptive requirements of the clinical trial protocol).
6. Good general health, as determined by the Investigator.
7. A positive SPT to histamine.
The following additional inclusion criteria are only applicable to the healthy subjects in Group A1:
8. Healthy subjects (non-atopic) with no clinically significant co-morbidity (including broncho-reactive airway disease like asthma, current allergic rhinitis, etc.).
9. Subjects with no history of allergy or intolerance to peanut or any other food and who consume peanuts with no effect.
10. Subjects with lack of sensitivity to peanut allergen confirmed by SPT using whole peanut extract.
11. Peanut specific immunoglobulin E (IgE) \<0.35 kU/L.
12. Ara h 2 specific IgE \<0.35 kU/L.
13. Subjects with negative basophil activation test (BAT).
The following additional inclusion criteria are only applicable to the subjects with PA in Group A2:
14. Clinical history of physician diagnosed PA.
15. Peanut allergen sensitivity confirmed by SPT and IgE.
16. Subjects who currently adhere to a strict peanut-free diet and who agree to continue this for the duration of the clinical trial.
17. Subjects who are able to handle and correctly use an adrenaline auto-injector.
Part B Main Inclusion Criteria:
1. Capable of giving signed informed consent.
2. Subject who has a signed and dated ICF.
3. Subjects aged 18 to 50 years of age inclusive, at the time of signing the ICF.
4. Male or female.
5. Female subjects who are not of childbearing potential (or females of childbearing potential who agree to comply with the contraceptive requirements of the clinical trial protocol).
6. Clinical history of physician diagnosed PA.
7. Peanut allergen sensitivity confirmed by positive SPT and Ara h 2 specific IgE ≥1.0 kU/L
8. Subjects with positive BAT.
9. Subjects who currently adhere to a strict peanut-free diet and who agree to continue this for the duration of the clinical trial.
10. Good general health, as determined by the Investigator.
11. Subjects who are able to handle and correctly use an adrenaline auto-injector.
Main Exclusion Criteria Part A and B:
1. Pregnant or lactating subject.
2. Presence of any medical condition that may reduce the ability to survive a serious allergic reaction.
3. Subjects with atopic dermatitis with \>25% skin surface involvement.
4. For subjects with PA, presence of severe, poorly controlled or uncontrolled asthma.
5. History of severe or life-threatening anaphylactic reactions to peanut resulting in neurological compromise or requiring mechanical ventilation.
6. History of severe or life-threatening anaphylactic reactions to foods (excluding peanuts), insect venom, exercise, drugs, or idiopathic causes, resulting in neurological compromise or requiring mechanical ventilation or deemed severe as per Investigator assessment.
7. Unable to receive epinephrine therapy or at greater risk of developing adverse reactions after epinephrine administration as assessed by the site Investigator.
8. Clinical history of drug or alcohol abuse, which, in the Investigator's opinion, could interfere with the subject's ability to participate in the clinical trial.
9. Participation in a clinical research trial with any investigational drug/placebo within 3 months of screening (Visit 1) or concomitantly with this clinical trial.
10. Personal, financial or other dependent relationship (e.g., employee or immediate relative) with the clinical trial site, Sponsor, Sponsor's representative, or another individual who has access to the clinical trial protocol.
11. Vulnerable subjects or those in judicial or governmental detention, detainment or imprisonment in a public institution.
