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