X0306 5 2018-12-31 1 0 0 0001615219 Flex Pharma, Inc. FLKS 0001762003 Boston Foundation, Inc. 75 ARLINGTON STREET BOSTON MA 02116 0 0 1 0 Common Stock, par value $0.0001 2019-01-30 5 S 0 1600000 0.326 D 2200000 D *Price reported of $0.326 is the weighted average price of the sales prices received for the 1,600,000 stock shares sold during the period 1/10/2019 to 1/30/2019. **This Form 5 voluntarily reports stock sales occurring after 1/9/2019, the date after Reporting Person ceased to own 10% of the Issuer as reported in Form 4 filed on 1/10/2019. As of the date of the filing of this Form 5, Reporting Person owns no shares of the Issuer. George C. Wilson 2019-02-05