Study to Assess the Safety, Tolerability, Pharmacokinetics and Immunogenicity of AK006 in Healthy Subjects and Subjects With Chronic Spontaneous Urticaria

Key Inclusion Criteria: To be included in the study, the participant must: * Weigh between 60 and 120 kg (inclusive) and have a body mass index (BMI) between 20 and 32 kg/m2, inclusive * Agree (female of childbearing potential or male with female partner of childbearing potential) to use a highly effective method (\<1% failure rate) of birth control, if sexually active from screening and for 16 weeks after the last dose of investigational product (IP). Additionally, to be included in Part A, B and D, the participant must: • Be in good general health with no significant medical history and has no clinically significant abnormalities on physical examination Additionally, to be included in Part C, the participant must: * Have a diagnosis of chronic spontaneous urticaria (CSU) for at least 6 months prior to screening * Has a diagnosis of moderate to severe CSU that is refractory to stable doses of a single 2nd or later generation H1-AH between 1× and 4× the licensed dose and frequency at the time of randomization as defined by the following: * Presence of hives and itch for ≥6 consecutive weeks at any time prior to the Screening, despite the use of non-sedating H1-AHs. Note: Subject must be on a non-sedating H1-AH for treatment of CSU symptoms at the time of the Screening visit. * UAS7 score ≥16 with a HSS7 score ≥8 for the 2 consecutive weeks prior to randomization (Day 1) while on the stable dose of an H1-AH. * Be on a stable dose of a single 2nd or later generation H1-antihistamines for the treatment of CSU, between 1× and 4× the licensed dose and frequency, by Day -14 of the Screening Period and must be willing to remain on the same stable dose throughout the study. * Able and willing to complete a daily electronic diary to collect CSU symptoms for the duration of the study. Key Exclusion Criteria: A participant who meets any of the following exclusion criteria will not be eligible for inclusion in the study: * Female participants who are pregnant, lactating, or planning to become pregnant during the study. * Abnormal laboratory values, or findings in physical examination, ECG (QTc \>450 ms for males and \>470 ms for females), or vital signs considered to be clinically significant by the investigator. Additionally, a participant will be excluded from Part A, B and D, if: • Received treatment with any prescribed (excluding hormonal contraceptives or hormone replacement therapy \[post-menopausal females\]) or nonprescribed systemic or topical medication (including herbal product, and vitamins) within 21 days prior to the first dose of IP (excluding acetaminophen). Additionally, a participant will be excluded from Part C, if: * Has known or suspected urticarial vasculitis * Subject has causes other than CSU for their urticaria including symptomatic dermographism, cholinergic urticaria, or any inducible urticaria * Subject has other conditions or diseases that in the investigator's opinion might influence study evaluations and results * Has any disease or condition (medical or surgical) which, in the opinion of the investigator, or medical monitor, would place the subject at increased risk