On the run
From ACT Wiki
The most recently issued of a series of similar securities from an issuer.
For example, the most recently issued 10 year US treasury (government) bond is on the run. Earlier issues are 'off the run'.
In general, there is greater liquidity in the on the run issue. This can be reflected in higher price, lower yield. The higher liquidity occurs as the issue finds its way to longer-term holders' portfolios from primary dealers and more speculative buyers, prime brokers.
The term can also be applied to derivatives related to securities.