Update (July 27): The US Justice Department will investigate whether Cassava Sciences manipulated results pertaining to its experimental Alzheimer’s drug, sources tell Reuters, though neither the government nor the biotech has confirmed the launch of the investigation.

Five studies coauthored by Hoau-Yan Wang at the City University of New York and colleagues were pulled from PLOS ONE over concerns about data integrity yesterday (March 30), Retraction Watch reports. Wang, who already had another retraction to his name and who contributed to three other papers that have received expressions of concern, conducted research on an Alzheimer’s therapy called Simufilam that is under development by Austin, Texas–based Cassava Sciences (formerly Pain Therapeutics). Wang is also a paid advisor to the company, and Cassava employee Lindsay Burns is a coauthor on two of the newly retracted papers, which don’t pertain to Simufilam or Alzheimer’s disease.

Citing “people familiar with the matter,” The Wall Street Journal reported in November that the Securities and Exchange Commission (SEC) is looking into claims that the company submitted Simufilam-related materials to the US Food and Drug Administration (FDA) that included altered data. The claims came in the form of a citizen’s petition filed with the FDA last August by two physicians who tell the WSJ that they shorted Cassava’s stock after becoming suspicious of the company’s published research. They also raise concerns that the company did not disclose its relationship with Wang when sharing his work with investors, the WSJ reports.

Cassava Chief Executive Remi Barbier defended his company to the WSJ: “There is zero evidence, zero credible evidence, zero proof that I’ve ever engaged in, nor anyone I know, has ever engaged in funny business.” 

Similarly, Wang also does not agree with the retractions and stands by the studies’ findings, according to the retraction notices.

But several scientists spoke to the WSJ about what appear to be manipulated Western blot images in papers about Simufilam. Barbier tells the publication that both the City University of New York and the National Institutes of Health launched inquiries into the accusations. However, neither the Cassava nor the SEC confirmed that an SEC investigation is underway.