X0306 4 2020-10-07 0 0001383701 Histogen Inc. HSTO 0001810103 Zhang Yizhuo C/O HISTOGEN INC. 10655 SORRENTO VALLEY ROAD, SUITE 200 SAN DIEGO CA 92121 1 0 0 0 Stock Option (right to buy) 1.89 2020-10-07 4 A 0 20000 0.00 A 2030-10-07 Common Stock 20000 20000 D This option was issued to the Reporting Person, a non-employee director of the Issuer, for his service as a director of the Issuer. The shares subject to this option become fully vested and exercisable on the first anniversary of the grant date, subject to the Reporting Person's continued service on the board of directors of the Issuer through such vesting date. /s/ Richard W. Pascoe as attorney-in-fact for Yizhuo Zhang 2020-10-09