A Study to Assess the Efficacy and Safety of GSK5784283 (Felcorekibart) Compared With Placebo in Participants With Chronic Rhinosinusitis With Nasal Polyps (CRSwNP)

The aim of this study is to assess the efficacy and safety of GSK5784283 administered as add-on maintenance therapy to participants with CRSwNP.

Inclusion Criteria: * 18 years of age and older * Male or eligible female participants * Physician-diagnosed CRSwNP for greater than or equals to (\>=) 12 months before screening. * Have had at least one of the following at Visit 1: * Any documented history of Nasal surgery for the removal of NP (or contraindications/intolerance to Nasal surgery) * Have used at least 3 consecutive days of Systemic corticosteroid (SCS) or 1 intramuscular depot injectable dose (or contraindications/intolerance to SCS) in the previous 12 months (but not in the past 3 months before screening) for the treatment of NP. * Endoscopic bilateral NP score consistent with severe CRSwNP assessed by the investigator. * Symptoms of Chronic rhinosinusitis (CRS) * Presence of symptoms of CRS for at least 12 weeks prior to Visit 1 such as rhinorrhea and/or reduction or loss of smell and * Moderate to severe nasal congestion/blockade/obstruction at Visit 1 based on clinical assessment by the investigator. * Participants must have an elevated SNOT-22 score at screening. * Participants must be on daily treatment with intranasal corticosteroids (INCS) (including intranasal liquid steroid wash/douching) for at least the 8 weeks prior to screening. Exclusion Criteria: * As a result of medical interview, physical examination, or screening investigation the physician responsible considers the participant unfit for the study. * Have the following conditions:- Cystic fibrosis, Antrochoanal polyps, Nasal cavity tumor (malignant or benign), Fungal rhinosinusitis, Rhinitis medicamentosa, Hyper-eosinophilic syndrome (HES) Eosinophilic granulomatosis with polyangiitis (EGPA) or Churg-Strauss Syndrome or eosinophilic esophagitis, Helminth parasitic infection in the past 6 months unless treated and have responded to therapy. * Female who are pregnant * Known substance or alcohol abuse * Current smokers (including e-cigarettes) or ex-smokers of 6 months or less * Other significant medical conditions (eg immunogenicity, Human immunodeficiency virus \[HIV\], viral hepatitis, tuberculosis \[TB\], cardiac and liver disease) that could impact participants' safety or study outcomes. * Where nasal surgery is contraindicated * Nasal surgery in the past 6 months * Asthma exacerbation in the past 4 weeks.