A Study to Evaluate the Safety, Tolerability and Pharmacokinetics of AZD5148 in Healthy Adults

This is a first in human study which will be conducted at four clinical units. Participants will be randomized to receive AZD5148, or placebo administered by intramuscular (IM) injection into the lateral thigh muscle or intravenous (IV) bolus (single, discrete dose of a drug). This study will include 7 dose cohorts, two of which will include exclusively participants of Chinese descent, Cohort 2b and 4b. Each dose cohort will begin with a Sentinel Group of 2 participants randomized 1:1 (AZD5148:placebo). The participants in the Sentinel Group will undergo a safety monitoring period of 24 hours before the remaining participants in that cohort are dosed. If there would be no safety concerns, the remaining participants in the cohort will be dosed in a 9:1 ratio (AZD5148: placebo). Each participant will be involved in the study for up to 56 weeks (including Screening Period) The study will comprise: * A Screening Period of maximum 28 days (Day -28 to Day -1 inclusive). * A Treatment and Follow-up Period lasting 12 months after the administration of the study drug. * Participants will be resident at the Clinical Unit from the day before study drug administration (Day -1) until all assessments are completed on Day 2. * A final Follow-up Visit will occur within 361 ± 14 days after the study drug administration.