This is a first time in Asia (FTIA) study of GSK4771261 in healthy participants of Chinese, Japanese, and White/European ancestry. The study will test whether GSK4771261 is safe, well-tolerated, how it is processed in the body, and whether it triggers an immune response.

Inclusion Criteria:

• Participants who are overtly healthy as determined by medical evaluation including medical history, physical examination, and laboratory tests. A participant with a clinical abnormality or laboratory parameter(s) which is/are not specifically listed in the inclusion or exclusion criteria, outside the normal reference range for the population being studied may be included only if the Investigator, in their clinical judgement, believes and documents that the finding is unlikely to introduce additional risk factors and will not interfere with the study procedures.
• Body weight at least 50.0 kilograms (kg) for male participants or at least 45.0 kg for female participants at screening
• Body Mass Index (BMI) within the range of 18.0 - 28.0 kilogram per square meters (kg/m^2) (inclusive) at screening
• A female participant is eligible to participate if she is not pregnant or breastfeeding, and is a Participant of non-childbearing potential (PONCBP)
• Capable of giving signed informed consent
• Participants of Chinese ancestry or Japanese ancestry or White/European ancestry are eligible based on meeting all the following criteria:
• Participants of Chinese ancestry: Born in mainland China, Hong Kong, or Taiwan; descendant of 4 ethnic Chinese grandparents and 2 ethnic Chinese parents; and have lived outside mainland China, Hong Kong, or Taiwan for less than 10 years at the time of screening
• Participants of Japanese ancestry: born in Japan; descendant of 4 ethnic Japanese grandparents and 2 ethnic Japanese parents; and have lived outside Japan for less than 10 years at the time of screening
• Participants of White/European ancestry: Self-identified as being of White/European ancestry (i.e., from the original peoples of Europe) irrespective of place of birth and current place of residence; and descendant of 4 grandparents and 2 parents of White/European ancestry (i.e., from the original peoples of Europe) irrespective of place of birth or current place of residence.

Exclusion Criteria:

• History or presence of cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrine, hematologic, or neurological disorders capable of significantly altering the absorption, metabolism, or elimination of drugs; constituting a risk when taking the study intervention; or interfering with the interpretation of data
• History of kidney disease or kidney abnormalities or Estimated glomerular filtration rate (eGFR) less than (<) 90 millilitres per minute per 1.73 square meter (mL/min/1.73m^2) (based on the Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI] 2021 eGFR equation) at screening and on Day -1
• Significant allergies to humanized monoclonal antibodies
• Clinically significant multiple or severe drug allergies, intolerance to topical corticosteroids, or severe post-treatment hypersensitivity reactions (including, but not limited to, erythema multiforme major, linear IgA dermatosis, toxic epidermal necrolysis, and exfoliative dermatitis)
• Current or previous diagnosis of diabetes mellitus (type 1 or type 2)
• Glycosylated hemoglobin (HbA1c) greater than or equal (>=)39 millimoles per mole (mmol/mol) at screening
• Bone fracture within 6 months prior to screening, or presence of a known unresolved or incompletely resolved fracture
• Have a history of malignant neoplasm (excepting definitively treated non-melanoma skin cancer or carcinoma in situ of the uterine cervix, which may be enrolled at any time) within the last 5 years
• Current thyroid disease or history of thyroid disease
• Presence of an incompletely healed wound at screening and/or planned surgical procedure that would occur during study
• Intended use of over-the-counter or prescription medication, including vitamins, herbal and dietary supplements (including St John's Wort) within 7 days or 5 half-lives (whichever is longer) prior to the first dose of study drug and for the duration of study participation (up to discharge on Day 8), unless, in the clinical judgement of the investigator, the medication will not interfere with the study procedures or compromise participant safety. Paracetamol (acetaminophen), at doses of <= 4 grams per day (g/day) is permitted for use at any time during the study
• Treatment with biologic agents (such as monoclonal antibodies including marketed drugs) or investigational drugs within 3 months or 5 half-lives (whichever is longer) prior to dosing
• Donation or loss of more than 450 millilitres (mL) of blood within 60 days prior to study drug administration. Donation or loss of more than 1.5 Liters (L) of blood (for male participants)/more than 1.0 L of blood (for female participants) in the 10 months prior to study drug administration in the current study
• Current enrolment or past participation in an investigational clinical trial in which an investigational medicinal product was administered within the following time periods prior to the first dosing day of the current study: 30 days, 5 half-lives or twice the duration of the biological effect of the investigational product, whichever is longer
• Exposure to more than 4 investigational medicinal products within 12 months prior to dosing in current study
• Positive preclinical study drug/alcohol screen, including tetrahydrocannabinol
• Evidence at screening of clinically significant hematological disorder (affecting hemoglobin, Red Blood Cells [RBC], White Blood Cells [WBC] or platelets) or abnormal blood clotting parameters
• Prothrombin time (PT) or activated partial thromboplastin time (aPTT) >1.5*upper limit of normal (ULN) at screening
• History or presence of excessive bleeding or coagulation disorders that in the opinion of the Investigator (in discussion with the GSK medical monitor as needed) poses a safety risk with regards to participation in the trial
• Positive HIV antibody test
• Presence of hepatitis B surface antigen (HBsAg) and/or hepatitis B core antibody (HBcAb) at screening or within 3 months prior to first dose of study intervention
• Positive hepatitis C antibody test result at screening or within 3 months prior to first dose of study intervention
• Positive hepatitis C RNA test result at screening or within 3 months prior to first dose of study intervention
• Regular use of any recreational drugs, including tetrahydrocannabinol
• Participants who are unable to refrain use of combustible tobacco products, and non-combustible nicotine delivery systems, inclusive of cigarettes, cigars, pipes, and materials used to "vape" during study visits or overnight stays
• Regular alcohol consumption within 6 months prior to the clinical study defined as: for sites in the Netherlands an average weekly intake of >21 units for males or for females. One unit of alcohol is equivalent to 10 g pure alcohol: a half-pint (approximately 250 mL) of beer (5 percent [%]), 1 glass (100 mL of wine [12%] or 1 measure (25 mL) of spirits [35%]
• Sensitivity to any of the study interventions, or components thereof, or drug or other allergy that, in the opinion of the investigator, in consultation with the medical monitor if required, contraindicates participation in the study
• Use of any products intended to treat medical conditions that are not approved by the governing health authority in a given country or region (for example, herbal medicine, health supplements, traditional medicine, homeopathic remedies, etc.)
• Sensitivity to heparin or a history of heparin-induced thrombocytopenia
• Alanine transaminase (ALT) >1.5*(ULN at screening
• Current or chronic history of liver disease, or known hepatic or biliary abnormalities (with the exception of Gilbert's syndrome or asymptomatic gallstones)
• Total bilirubin >1.5*ULN at screening; Participants with Gilbert's syndrome can be included with total bilirubin <=3.0xULN as long as direct bilirubin is <=1.0xULN
• QTc >450 milliseconds (msec) or QTc >480 msec for participants with bundle branch block

Study Sponsor will assess requests from qualified researchers for anonymized individual patient-level data and related study documents. Data sharing is subject to certain criteria, conditions, and exceptions. For further information, refer to https://d3l8i7lo48obsd.cloudfront.net/gsk-patient-level-data-sharing-july2025-1-Bgwa1UthxvluYbWYTThw.pdf

Anonymized IPD will be made available within 6 months of publication of primary, key secondary and safety results for studies in product with approved indication(s) or asset(s) with development terminated across all indications.

Anonymized IPD is shared with researchers whose proposals are approved by an Independent Review Panel and after a Data Sharing Agreement is in place. Access is provided for an initial period of 12 months, but an extension may be granted, when justified, for up to 6 months.