The primary objective of the study is to investigate the safety and tolerability of ascending doses of GSK3862995B following single dose in healthy participants and repeat doses in participants with Chronic obstructive pulmonary disease (COPD).

Inclusion Criteria:

Healthy participants (Part A)

• Participant must be 18 to 65 years of age inclusive.
• Participants who are overtly healthy as determined by medical evaluation including medical history, physical examination, laboratory tests, and cardiac monitoring
• Body weight within the range 50-110 kilogram (kg) (inclusive)
• Body mass index (BMI) within the range 19.5-32 kilogram per square meter (kg/m^2)
• Male and/or female of non-childbearing potential

Participants with Chronic Obstructive Pulmonary Disorder (COPD) (Part B)

• Participant must be 40 to 75 years of age inclusive.
• Body weight within the range 50-110 kg (inclusive)
• BMI within the range 19.5-32 kg/m^2
• Participant has a confirmed diagnosis of COPD for greater than (>)12 months
• Participants must present with a measured post-salbutamol Forced expiratory volume in 1 second/Forced vital capacity (FEV1/FVC) ratio of less than (<) 0.70 at screening to confirm the diagnosis of COPD and a measured post-salbutamol FEV1 greater than or equal to (>=) 40% of predicted normal values.
• Participants must have a well-documented requirement for optimized standard of care background therapy that includes daily inhaled medication.
• A peripheral blood eosinophil count of >=150 cells/microliter (mcL) at screening
• Former cigarette smokers with a history of cigarette smoking of >=10 pack-years at screening current smokers (includes the use of any type of nicotine containing product), or non-smokers are permitted
• Male and/or female of non-childbearing potential.

Exclusion Criteria:

• Participant has a past or current medical condition(s) or disease(s) that is/are not well controlled and, which in the judgement of the Investigator, may affect participant safety or affect study endpoints.
• A history of recurrent infections, or treatment of a chronic infection within 3 months prior to the first dose of study drug, including both serious local infection (for example, cellulitis, abscess) or systemic infection (for example, pneumonia, tuberculosis, hepatitis B, shingles).
• 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 immunoglobulin A (IgA) dermatosis, toxic epidermal necrolysis, and exfoliative dermatitis).
• Lymphoma, leukemia, or any malignancy within the past 5 years except for basal cell or squamous epithelial carcinomas of the skin that have been resected with no evidence of metastatic disease for 3 years.
• Breast cancer within the past 10 years
• Alanine transaminase (ALT) >1x upper limit of normal (ULN)
• Total bilirubin >1.5xULN (isolated total bilirubin >1.5xULN is acceptable if total bilirubin is fractionated and direct bilirubin less than (<) 35%).
• Current or chronic history of liver disease or known hepatic or biliary abnormalities (with the exception of Gilbert's syndrome or asymptomatic gallstones).
• A clinically significant abnormality in 12-lead ECG readings performed at screening
• A clinically significant abnormality in the Holter monitor performed at screening (IV cohorts only).

Qualified researchers may request access to anonymized individual patient-level data (IPD) and related study documents of the eligible studies via the Data Sharing Portal. Details on GSK's data sharing criteria can be found at: https://www.gsk.com/en-gb/innovation/trials/data-transparency/

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 terminated asset(s) 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.