The transaction took place on 9 August, the same day Mylan ‐ the drugmaker that manufactures EpiPen released its most recent earnings report. Mylan spokeswoman Nina Devlin told the Guardian that the sale was "part of a 10b5 plan".
Typically, executives and directors of public companies who want to sell their stock establish a written 10b5 plan to do so. Most of 10b5 plans include a waiting period spanning days or weeks to avoid any suspicion of trading based on material non-public information. Simply put, 10b5 plans are used to avoid being suspected of insider trading.