This document summarizes Andrew Su's presentation on building and mining a heterogeneous biomedical knowledge graph. The presentation discusses integrating data from 29 public resources to create a knowledge graph called Hetionet containing over 47,000 nodes and 2.25 million relationships. It also describes Semantic MEDLINE, a database containing over 90 million biomedical relationships extracted from PubMed abstracts. Finally, it discusses challenges with using knowledge graphs for computational drug repurposing due to loss of predictive signals over time as relationships age and new knowledge is discovered.