Background This study examines the dynamics of the eculizumab patenting, orphan designation, and marketing authorization process in different countries and regulatory systems and analyzes drug revenues since its first marketing authorization. Methods A retrospective case study was conducted. Multiple information sources were used to: determine the status of eculizumab patents; examine the designation of orphan drug status by US, European, Japanese, and Brazilian regulatory authorities to determine registration status and approved clinical indications; estimate the prevalence of associated clinical conditions; investigate the history of the drug manufacturer, Alexion Pharmaceuticals, Inc., and its financialized business model; and examine global eculizumab sales revenues since its first marketing authorization. Results Our search yielded 32 patent families divided into 98 applications. The first patent granted was filed in 1995 by Alexion Pharmaceuticals, Inc. in the US. Eculizumab has always been as an orphan drug, except in the Brazilian regulatory agency. All clinical indications approved thus far refer to rare diseases (e.g., paroxysmal nocturnal hemoglobinuria syndrome, atypical hemolytic-uremic syndrome, refractory and generalized myasthenia gravis, and neuromyelitis optica spectrum disorder). Alexion's revenues amounted to more than US$25 billion between 2007 and 2019, showing a growing trend. Eculizumab led sales from the beginning, being the only product in the company's portfolio until 2015. In 2019, the drug accounted for 79.1% of all revenues. Discussion Our findings show that a strategy focused on obtaining orphan drug designation, expanding therapeutic indications and the geographic range of marketing approvals, extending monopoly periods, and prioritizing public procurement niches has enhanced revenues and helped the company achieve leadership in a highly specific and profitable market.