GSK PLC

This securities fraud class action asserts claims against GlaxoSmithKline plc (“GSK”), a multinational pharmaceutical and biotechnology company, its current CEO, Emma Walmsley, and its former CFO, Iain Mackay. On July 7, 2025, Lead Plaintiff filed the Consolidated Class Action Complaint against GSK and these executives pursuant to Sections 10(b) and 20(a) of the Exchange Act.

The case arises out of public representations that Defendants made during the Class Period concerning Zantac, a medication to treat heartburn, reflux, and ulcers. From the early 1980s through late-2019, GSK sold this drug to millions of consumers while allegedly knowing that its active ingredient, ranitidine, formed a carcinogenic substance known as “NDMA” both within and outside the human body. Following the revelation of the presence of this carcinogen and the drug’s removal from the market in 2019-2020, GSK faced an onslaught of litigation. Defendants, however, claimed that GSK was still “investigating” the source of the NDMA found in Zantac and assured investors that GSK’s financial and business risk associated with litigation related to Zantac was minimal. 

Plaintiffs allege that the foregoing representations were materially false or misleading. In this regard, the Complaint alleges that Defendants manufactured Zantac while aware that the drug’s active ingredient formed a carcinogen, NDMA, when interacting with elements normally found in the human digestive system. In 1982, prior to Zantac’s initial FDA approval and public sale the following year, Dr. Richard Tanner, a GSK scientist, documented the degradation of Zantac into NDMA in the “Tanner Study.” Consequently, Defendants were aware prior to the FDA approval of Zantac that the drug’s active ingredient would form a carcinogen. Despite the FDA’s concerns and questions regarding this issue during the drug approval process, GSK dismissed the “possibility of carcinogenesis,” and concealed its knowledge of this carcinogen for decades. The Complaint alleges that the truth contained in the Tanner Study was first revealed to investors and the public following a February 15, 2023 publication of a Bloomberg Businessweek article entitled “Zantac Cancer Risk Data Was Kept Quiet by Manufacturer Glaxo for 40 years.”

In early 2019, an independent laboratory, Valisure, discovered that OTC Zantac contained significantly more NDMA than the FDA’s daily limit. Based on this finding, Valisure submitted a Citizen’s Petition to the FDA, requesting it be removed from the market. That same year, following Valisure’s revelation to the public of the unsafe levels of NDMA in Zantac, the FDA recalled the drug. However, for years thereafter, GSK continued to conceal from investors and the public the connection between Zantac and NDMA. In particular, Defendants made misrepresentations concerning: (1) GSK’s awareness of carcinogenic issues with Zantac before the FDA reached out in 2019; (2) GSK’s “exposure” to patient safety and product quality risks, which Defendants misleadingly claimed remained “unchanged,” even after GSK belatedly revealed the Tanner Study showing the connection between the drug and NDMA; (3) the FDA’s purportedly thorough reviews of Zantac’s safety, when GSK failed to disclose critical data to the FDA, including the Tanner Study; and (4) the range of GSK’s Zantac-related liability.

The relevant truth about the connection between NDMA and Zantac, as well as the potential liability for GSK, was revealed through a series of corrective events. First, on August 10, 2022, analysts revealed that GSK’s potential Zantac litigation exposure could be “in the $5-10 billion range.” Additionally, on August 11, 2022, analysts revealed that GSK would bear approximately 80% percent of the Zantac litigation liability—far from GSK’s representations that its risk exposure was “unchanged.” Next, on August 16, 2022, Defendant Mackay confirmed GSK’s exposure was significant, quantifying it to be in the “mid $ billions.” Following these disclosures, GSK’s stock price fell precipitously. The Complaint alleges that GSK’s investors suffered substantial losses as a result of Defendants’ misstatements and omissions being revealed to the market.