The Regeneron Case: Regeneron involved a drug manufacturer's contributions to a copayment assistance program. The drug manufacturer, Regeneron, funded an independent charitable organization, which in turn subsidized patient copayments for Eylea, Regeneron's blockbuster biologic drug for macular degeneration. 4 The government alleged that Regeneron's contributions to the charitable fund violated the AKS, thereby giving rise to FCA liability. 5 Regeneron contended that in order to impose FCA liability pursuant to an alleged violation of the AKS, the government needed to prove that the alleged kickback scheme was the "but for" cause of the submitted claims. 6 In other words, if the government could not prove that prescriptions written for Eylea, and the resulting Medicare reimbursement claim, would not have happened absent the copay assistance program, then the claim could not have "result[ed] from" a violation of the AKS.