Catalyst Pharmaceutical sued the FDA for approving a rival company's drug regulation, namely Ruzurgi, which is utilized to cure Lambert-Eaton Myasthenic Syndrome (LEMS). The biological name of the drug is known as Amifampridine. The complaint against the FDA was noted for approving the Jacobus Pharmaceutical Company’s drug labeling as an unambiguous FDA regulations' violation.

Catalyst further explained in the complaint noted as "FDA arbitrarily treated Catalyst differently than Jacobus. For example, the FDA allowed Jacobus to submit studies and clinical trials post-approval that it required a Catalyst to submit before FDA would even consider an NDA submitted by Catalyst for Firdapse.  Specifically, Catalyst was required to submit the results of an animal toxicology study and a clinical trial to evaluate the effect of Firdapse on kidneys before Firdapse was reviewed, while FDA permitted Jacobus to conduct a juvenile animal toxicology study and a clinical trial to evaluate the effect of Ruzurgi on kidneys after the Agency approved Ruzurgi".