This is a Phase 1b, single center study designed to evaluate the efficacy, safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of GSK3923868 following repeat doses in mild asthmatics during experimental human rhinovirus 16 (HRV-16) infection. The study will be conducted in two parts. Part A will determine the efficacy of GSK3923868 administration after viral inoculation (i.e., therapeutic treatment) and Part B may be undertaken to determine the efficacy of GSK3923868 administration before viral inoculation (i.e., prophylactic treatment). The purpose of this study is to establish proof-of-mechanism that GSK3923868 treatment can reduce symptoms of Human Rhinovirus (HRV) infection in a controlled setting.

Inclusion Criteria:

• All Participant aged between 18 to 65 years of age (inclusive).
• Participants with a diagnosis of asthma.
• A screening pre-bronchodilator FEV1 greater than or equal to (≥) 65 percentage (%) predicted normal value.
• Positive Methacholine challenge test, defined as ≥ 20% fall in FEV1 at a methacholine concentration less than or equal to (≤) 16 milligram/milliliter (mg/mL) at Screening.

If the methacholine challenge test is negative or the participant is unable to perform this test, bronchodilator reversibility is allowed as an alternative, assessed as follows:

• Positive bronchodilator reversibility test, defined as an increase in FEV1 >12% and >200 mL from baseline, 10 to 15 minutes after administration of 400 micrograms (mcg) salbutamol (or equivalent).
• Participants with positive skin prick test.
• The HRV-16 neutralization antibody assay indicates that the participant will be susceptible to HRV-16 infection.
• Participants with controlled asthma, using short-acting beta agonist (SABA) or intermittent inhaled corticosteroid (ICS) or ICS/ long-acting beta agonist (LABA) therapy.
• Male and female- A female participant is eligible to participate if she is not pregnant or breastfeeding.
• Participant capable of giving signed informed consent.

Exclusion Criteria:

All participants:

• Any asthma exacerbation requiring systemic corticosteroids within 8 weeks of admission, or that resulted in overnight hospitalization requiring additional treatment for asthma within 3 months of admission.
• History of life-threatening asthma, defined as any asthma episode that required admission to a high-dependency or intensive therapy unit.
• The presence of concurrent significant pulmonary diseases, other than asthma, including bronchiectasis, pulmonary fibrosis, bronchopulmonary dysplasia, chronic bronchitis, emphysema, chronic obstructive pulmonary disease, or other significant respiratory abnormalities.
• Any significant abnormality altering the anatomy of the nose in a substantial way or nasopharynx that may interfere with the study.
• Any clinically significant history of epistaxis (large nosebleeds) within the last 3 months of admission and/or history of being hospitalized due to epistaxis on any previous occasion.
• Any nasal or sinus surgery within 3 months of admission with any acute illness, including a common cold or other respiratory tract infection within 6 weeks before admission.
• Any major illness or hospitalization within 6 months before admission to the unit.
• Lifetime history of anaphylaxis or severe allergic reaction or significant intolerance to any food or drug.
• Fridericia's QT correction formula (QTcF) >450 millisecond (msec) on Day -1 based on the average of triplicate ECGs.
• Evidence of vaccinations within the 4 weeks prior to the planned date of viral challenge.
• Intention to receive any vaccination before the last day of follow up.
• Prior participation in another Human Viral Challenge study with a respiratory virus in the preceding 12 months.
• Positive pathogen screen for respiratory tract infection
• History of regular use of tobacco or nicotine-containing products.
• Sensitivity to any of the study interventions, or components thereof, or drug or other allergy that contraindicates participation in the study.

IPD for this study will be made available via the Clinical Study Data Request site.

IPD will be made available within 6 months of publishing the results of the primary endpoints, a key secondary endpoints and safety data of the study.

Access is provided after a research proposal is submitted and has received approval from the 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 can be granted, when justified, for up to another 12 months.

The participants and site staff will be blinded to the study intervention.