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 Be in good general health with no significant medical history and has no clinically significant abnormalities on physical examination (Part A and B only) Have a diagnosis of chronic spontaneous urticaria (CSU) for at least 6 months (Part C only) 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 (Part C only) Have moderate to severe CSU that is refractory to stable doses of a single 2nd or later generation H1-antihistamines between 1× and 4× the licensed dose and frequency at the time of randomization as defined by the following (Part C Only): Presence of hives and itch for at least 6 consecutive weeks prior to the Screening Visit. Weekly urticaria activity score (UAS7) of at least 16 and weekly hive severity score (HSS7) of at least 8 for the 2 consecutive weeks prior to randomization (Day 1) while on the stable dose of an H1-antihistamines as described above (Note: participant must have completed at least 4 daily Urticaria Patient Daily Diary (UPDD) questionnaires during each of these qualifying weeks to remain eligible for study participation). Key Exclusion Criteria: A participant who meets any of the following exclusion criteria will not be eligible for inclusion in the study: Male participants sexually active with a woman of childbearing potential, or female participants of childbearing potential who are not willing to use a highly effective method of contraception from the time of first dose of investigational product (IP) until 120 days after the last dose 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. Treatment with any prescribed (excluding hormonal contraceptives) or nonprescribed systemic or topical medication (including herbal product, and vitamins) within 21 days prior to the first dose of IP (excluding acetaminophen) (Part A and B only).