This article analyses the importance of legal aspects and patent law in the development, production, and marketing of pharmaceuticals at the beginning of the 20th century in the German Empire. It investigates how property, priority, and trust were linked and how this affected the patenting of pharmaceuticals. Moreover, it also looks at the interaction between different actors—scientists, the state, and the industry—and possible conflicts resulting from this interaction. After a general introduction to and review of the literature on law and legal aspects in the history of pharmaceuticals, the article sketches the state regulation of pharmaceuticals and the impact of patent law on pharmaceuticals in historical perspective. It goes on to explore the nexus of priority, prestige, and originality to explain why applications for patents became attractive to scientists. The influence of patents on legal, economic, and scientific aspects within the research process and their entanglements are demonstrated using the example of the Institute for Experimental Therapy and the Georg Speyer House in Frankfurt in the first decade of the 20th century. Friedrich Franz Friedmann’s application for his tuberculosis remedy serves to emphasize the aspects of scientific research, patent law, economic interest, and public trust. The final section summarizes the relation between patents, priority, property, and trust as well as the entanglement of law and science in the history of pharmaceuticals.