GlaxoSmithKline (Middlesex, UK)

GSK plc (an acronym from its former name GlaxoSmithKline plc) is a British multinational pharmaceutical and biotechnology company with headquarters in London. It was established in 2000 by a merger of Glaxo Wellcome and SmithKline Beecham, which was itself a merger of a number of pharmaceutical companies around the Smith, Kline & French firm.

GSK is the tenth largest pharmaceutical company and No. 294 on the 2022 Fortune Global 500, ranked behind other pharmaceutical companies China Resources, Sinopharm, Johnson & Johnson, Pfizer, Roche, AbbVie, Novartis, Bayer, and Merck Sharp & Dohme.

The company has a primary listing on the London Stock Exchange and is a constituent of the FTSE 100 Index. As of February 2024, it had a market capitalisation of £69 billion, the eighth largest on the London Stock Exchange.

The company developed the first malaria vaccine, RTS,S, which it said in 2014, it would make available for five per cent above cost. Legacy products developed at GSK include several listed in the World Health Organization's List of Essential Medicines, such as amoxicillin, mercaptopurine, pyrimethamine and zidovudine.

In 2012, under prosecution by the United States Department of Justice (DoJ) based on combined investigations of the Department of Health and Human Services (HHS-OIG), FDA and FBI, primarily concerning sales and marketing of the drugs Avandia, Paxil and Wellbutrin, GSK pleaded guilty to promotion of drugs for unapproved uses, failure to report safety data and kickbacks to physicians in the United States and agreed to pay a US$3 billion (£1.9bn) settlement. It was the largest health-care fraud case to date in the US and the largest settlement in the pharmaceutical industry.