The most common use of "IRB" combined with alphanumeric strings is for Clinical Trial Reports or ethics approval packages. If you are looking for a specific study's findings, this file would typically contain protocol summaries and safety data.
In medical and academic fields, this refers to a committee that reviews research to ensure ethical standards are met.
This often serves as a geographic code (e.g., Mozambique) or a specific project/version identifier in technical naming conventions.