Mo. Rev. Stat. § 429.616

A real estate broker may bring suit to enforce a lien which attaches pursuant to the provisions of sections 429.600 to 429.627 in the circuit court in the county where the property is located by filing a verified petition that the lien has been recorded. Unless the claim is based upon an option to purchase the commercial real estate, the broker claiming such lien must commence proceedings within six months after recording the lien and failure to commence proceedings within the six months shall extinguish the lien. A claim for the same lien, extinguished pursuant to this section and section 429.618, may not be asserted in any subsequent proceeding.