Academic genres are not static, but they may change according to the values and demands of the particular discourse communities that shape them. This paper explores the research article (RA) abstract, a relevant informative and promotional genre that exhibits the prevalent rhetorical practices of a specific disciplinary community. From a diachronic perspective, our purpose is to examine how these practices have evolved over time. To this end, using a genre-based approach, we have analysed the rhetorical moves and steps of 180 RA abstracts published in the "Journal of Experimental Medicine," over a period of nine decades (1940-2022). The findings revealed that the abstracts have increasingly become more promotional in terms of the persuasive rhetorical strategies that the authors use to enhance the contribution of their research. This is seen in the fact that the texts of more recent decades present a growing number of promotional communicative functions, mainly the moves/steps that claim the importance of the research topic and state the implications or significance of research. This study can have pedagogical implications for English for research publication purposes (ERPP) practitioners and early career researchers who seek to publish in international medical journals.