X0306 4 2020-04-06 0 0001622229 Unum Therapeutics Inc. UMRX 0001451612 Booth Bruce C/O UNUM THERAPEUTICS INC. 200 CAMBRIDGE PARK DRIVE, SUITE 3100 CAMBRIDGE MA 02140 1 0 0 0 Stock Option (Right to Buy) 0.3495 2020-04-06 4 A 0 86735 0.2205 A 2030-04-06 Common Stock 86735 86735 D The option award was issued to the Reporting Person, who elected to take shares in lieu of cash compensation for services as a director, pursuant to the Issuer's non-employee director compensation plan. The number of options granted was determined by dividing the cash compensation otherwise payable with respect to the quarter by the Black-Scholes value of a single option calculated as of the date of the grant. This option is fully vested at time of grant. This option was granted to the Reporting Person, a director of the Issuer. The proceeds of any sale of shares of common stock issued to the Reporting Person upon exercise of this option will be transferred to Atlas Venture Advisors, LLC and as such, the Reporting Person disclaims beneficial ownership of the securities reported herein for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, except to the extent of this pecuniary interest therein, if any. /s/ Frank Castellucci, as Attorney-in-Fact 2020-04-08