Mo. Rev. Stat. § 408.090

Any other laws to the contrary notwithstanding, in any case in which advances of money, repayable on demand, are made solely upon securities, as defined in section 400.8-102 (a), RSMo 1969, pledged as collateral for such repayment and in which such advances are used by the borrower only for the purchase of securities, as so defined, it shall be lawful to receive or to contract to receive and collect, as compensation for making such advances, any sum agreed upon by the parties to such transaction.