August 3, 2017 (Shareholders Foundation) - A participant in the Mallinckrodt PLC’s Employee Stock Purchase Plan filed a lawsuit against Mallinckrodt Public Limited Company over alleged violations of § 11 of the Securities Act of 1933 On August 14, 2014, Mallinckrodt PLC acquired Questcor Pharmaceuticals, Inc. in a $5.6 billion transaction. As a result of the acquisition, Mallinckrodt added HP Acthar Gel (Acthar), an injectable medication made from pigs' pituitary glands, to its drug portfolio. Acthar is the only approved therapeutic preparation of adrenocorticotropic hormone (ACTH) in the U.S., and is approved by the U.S. Food and Drug Administration (FDA) as a treatment for 19 different conditions, including infantile spasms, and difficult-to-treat autoimmune and inflammatory conditions.

On November 9, 2015, Citron Research described Mallinckrodt’s abuse of the pharmaceutical reimbursement system, and stated that Mallinckrodt has “significantly more downside” than rival Valeant Pharmaceuticals International, Inc. and is “a far worse offender” of the reimbursement system.

On November 16, 2016, Citron Research issued a report titled Mallinckrodt CEO FRAUD exposed by the new Medicare Drug Dashboard . In this article, Citron stated that Mallinckrodt CEO has committed Fraud by lying to the shareholders about the Company's dependence on the Medicare system. Per Citron, Mallinckrodt drug Acthar, which is medically unproven, is now the most expensive drug reimbursed by Medicare. Citron has placed a price target of $20 on Mallinckrodt stock. During a conference call with investors on November 29, 2016, Trudeau stated that Acthar now represents a significantly greater proportion of our operating income than one-third.

Shares of Mallinckrodt PLC declined from $129.44 per share in May 2015 to as low as $52.59 per share on 12, November 2015, respectively $42.67 per share on January 18, 2017.