Mo. Rev. Stat. § 116.115: Withdrawal of petition, when — vacation of official ballot title, when.

Any person who submits a sample sheet to or files an initiative petition with the secretary of state may withdraw the petition upon written notice to the secretary of state. If such notice is submitted to the secretary of state, the proposed petition shall no longer be circulated by any person, committee, or other entity. The secretary of state shall vacate the certification of the official ballot title within three days of receiving notice of the withdrawal.