A Study of GSK4527363 in Healthy Participants, Systemic Lupus Erythematosus (SLE) Participants, Healthy Chinese, and Japanese Participants and CTD-ILD Participants

Prior treatment

• A history of recurrent infections, or treatment of a chronic infection within 3 months prior to the first dose of study drug
• Any acute infection (including upper respiratory tract infections and urinary tract infections) which has not fully resolved within four weeks before dosing
• Symptomatic herpes zoster within 3 months prior to screening
• Presence of Hepatitis B surface antigen (HBsAg) and 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 Ribonucleic acid (RNA) test result at screening or within 3 months prior to first dose of study intervention
• Prior medical history of anaphylaxis
• Live vaccine(s) within 30 days before the dosing day or plans to receive such vaccines during the study
  • For Part B (SLE participants):
• Have an acute or chronic infection requiring management as follows:
  • Currently on any suppressive therapy for a chronic infection such as pneumocystis, cytomegalovirus, herpes simplex virus, herpes zoster, or atypical mycobacteria ii. A serious infection requiring treatment with antibiotics and/or hospitalization if the last dose of antibiotics or the hospital discharge date was within 60 days of the first day of dosing (Day 1). Prophylactic anti-infective treatment is allowed
• Presence of HBsAg and/or 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
• Live or live-attenuated vaccine(s) within 30 days prior to Screening
  • For Part D Participants:
• FVC \<= 45% predicted at Screening Pulmonary arterial hypertension, as determined by the Investigator, prior to Day 1
• Major surgery (including joint surgery) within 3 months prior to Screening or planned during the duration of the study
• Previous or planned major organ transplant (e.g. heart, lung, kidney, liver) or bone marrow transplant (e.g. autologous stem cell transplant)
• Presence of HBsAg and/or 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
• Live or live-attenuated vaccine(s) within 30 days prior to Screening or plans to receive such vaccines during the Screening period or during the clinical study

Other illness

• History or presence or cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrine, hematologic, or neurological disorders
• Have a history of malignancy, or a strong family history of malignancies related to immunosuppression
• Clinically significant multiple or severe drug allergies, intolerance to topical corticosteroids, or severe post-treatment hypersensitivity reactions
• Evidence of active or latent Tuberculosis (TB)
• Positive Human immunodeficiency virus (HIV) antibody test at screening
• Have clinical evidence of significant unstable or uncontrolled acute or chronic diseases not due to SLE which, in the opinion of the principal investigator (PI), could confound the results of the clinical study or put the participant at undue risk
• History or positive test at Screening for HIV
• Solid or hematological malignancy or a history of malignancy (in the past 5 years) of except for basal cell or squamous cell in situ skin carcinomas, Cervical intraepithelial neoplasia (CIN) or carcinoma in situ of the cervix that have been resected with no evidence of metastatic disease for 3 years
• Have clinical evidence of significant unstable or uncontrolled acute or chronic diseases not due to CTD-ILD (i.e., cardiovascular, metabolic, hematologic, GI, hepatic, renal, neurological, psychiatric, malignancy, or infectious diseases) which, in the opinion of the PI, could confound the results of the clinical study or put the participant at undue risk
• Have an acute or chronic infection including requiring management
• History or positive test at Screening for HIV
• Solid or hematological malignancy or a history of malignancy (in the past 5 years) of except for basal cell or squamous cell in situ skin carcinomas, CIN or carcinoma in situ of the cervix that have been resected with no evidence of metastatic disease for 3 years

Lab values

• Alanine transaminase (ALT) \>=1.1\* Upper limit of normal (ULN)
• Total bilirubin \>1.0\*ULN; Participants with Gilbert's syndrome can be included with total bilirubin \>=1.5\*ULN as long as direct bilirubin is less than or equal to (\<=)1.5\*ULN
• QT interval corrected for heart rate according to Fridericia's formula (QTcF) \>450 milliseconds (msec)
• ALT \>2\*ULN
• Total bilirubin \>1.5\*ULN; Participants with Gilbert's syndrome can be included with total bilirubin \>1.5\*ULN as long as direct bilirubin is \>1.5\*ULN
• ALT \>2\*ULN
• Total bilirubin \>1.5\*ULN; Participants with Gilbert's syndrome can be included with total bilirubin \>1.5\*ULN as long as direct bilirubin is \>1.5\*ULN

Other

• For Part A and Part C (Healthy Participants):
• Abnormal blood pressure
• Any acute, severe lupus related flare during the Screening Period that needs immediate treatment
• Evidence of active or latent TB
• Confirmed Progressive Multifocal Leukoencephalopathy (PML) or unexplained new-onset or deteriorating neurologic signs and symptoms
• QTcF \>450 msec
• A diagnosis of: ILD other than CTD-ILD and/or SLE
• Evidence of active or latent TB
• Confirmed PML or unexplained new-onset or deteriorating neurologic signs and symptoms

• For Part A and Part C (Healthy Participants):
• Participant must be 18 to 55 years of age inclusive, at the time of signing the informed consent form
• Participants who are overtly healthy as determined by medical evaluation including medical history, physical examination, laboratory tests, and cardiac monitoring (vital signs and 12-lead ECG)
• Part C only: Be of Japanese (Cohort C1) or Chinese (Cohort C2) ancestry i. Born in Japan (Cohort C1) or China mainland, Hong Kong or Taiwan (Cohort C2); and ii. Descendent of 2 ethnic Japanese (Cohort C1) or Chinese (Cohort C2) parents and 4 ethnic grandparents; and iii. Have lived outside Japan (Cohort C1) or China mainland, Hong Kong or Taiwan (Cohort C2) for less than 10 years at the time of screening
• Body weight greater than or equals to (\>=) 45 kilograms (kg)
• Body mass index (BMI) within the range 18-32 kilograms per square meter (kg/m\^2) (inclusive)
• Male or female of non-childbearing potential
  • For Part B (SLE participants):
• 18 to 65 years of age inclusive, at the time of signing the informed consent form
• Documented clinical diagnosis of SLE according to the (European alliance of associations of rheumatology \[EULAR\]/ American College of Rheumatology \[ACR\] SLE classification criteria)
• Body weight \>= 45 kg
• BMI within the range 18-32 kg/m\^2 (inclusive)
• Male or female
• Capable of giving signed informed consent For Part D (CTD-ILD Participants)
• Participants must be 18 to 65 years of age, at the time of signing the informed consent form
• Documented clinical diagnosis of specific Connective Tissue Diseases in accordance with internationally recognised classification criteria
• Documented clinical diagnosis of interstitial lung disease (ILD) as determined by historical High-resolution computed tomography (HRCT)
• Participants must be on a stable dose of therapy to manage ILD and/or underlying connective tissue disease (CTD)
• Body weight \>= 45 kg
• BMI within the range 18-32 kg/m\^2 (inclusive)
• Male or female
• Capable of giving signed informed consent