X0206 3 2017-11-15 0 0001501697 Arsanis, Inc. ASNS 0001644160 SVLSF V, LLC ONE BOSTON PLACE, SUITE 3900 201 WASHINGTON STREET BOSTON MA 02108 0 0 1 0 0001717728 SVLSF VI, LLC ONE BOSTON PLACE, SUITE 3900 201 WASHINGTON STREET BOSTON MA 02108 0 0 1 0 0001667605 SV Life Sciences Fund VI Strategic Partners, L.P. ONE BOSTON PLACE, SUITE 3900, 201 WASHINGTON STREET BOSTON MA 02108 0 0 1 0 0001642251 SV Life Sciences Fund VI, L.P. ONE BOSTON PLACE, SUITE 3900, 201 WASHINGTON STREET BOSTON MA 02108 0 0 1 0 0001482194 SV Life Sciences Fund V Strategic Partners, L.P. ONE BOSTON PLACE, SUITE 3900, 201 WASHINGTON STREET BOSTON MA 02108 0 0 1 0 0001460732 SV LIFE SCIENCES FUND V LP ONE BOSTON PLACE, SUITE 3900, 201 WASHINGTON STREET BOSTON MA 02108 0 0 1 0 Series A-1 Convertible Preferred Stock Common Stock 19128 D Series A-1 Convertible Preferred Stock Common Stock 404 D Series A-2 Convertible Preferred Stock Common Stock 247010 D Series A-2 Convertible Preferred Stock Common Stock 5219 D Series B Convertible Preferred Stock Common Stock 322102 D Series B Convertible Preferred Stock Common Stock 6806 D Series C Convertible Preferred Stock Common Stock 111955 D Series C Convertible Preferred Stock Common Stock 2365 D Series D Convertible Preferred Stock Common Stock 202915 D Series D Convertible Preferred Stock Common Stock 4288 D Series D Convertible Preferred Stock Common Stock 431980 D Series D Convertible Preferred Stock Common Stock 14789 D The Series A-1 Convertible Preferred Stock is convertible into Common Stock on a 0.29300-for-one basis into the number of shares of Common Stock shown in column 3 at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering without payment of further consideration. The shares have no expiration date. The Series A-2 Convertible Preferred Stock is convertible into Common Stock on a 0.35785-for-one basis into the number of shares of Common Stock shown in column 3 at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering without payment of further consideration. The shares have no expiration date. The Series B Convertible Preferred Stock is convertible into Common Stock on a 0.44650-for-one basis into the number of shares of Common Stock shown in column 3 at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering without payment of further consideration. The shares have no expiration date. The Series C Convertible Preferred Stock is convertible into Common Stock on a 0.49832-for-one basis into the number of shares of Common Stock shown in column 3 at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering without payment of further consideration. The shares have no expiration date. The Series D Convertible Preferred Stock is convertible into Common Stock on a 0.29300-for-one basis into the number of shares of Common Stock shown in column 3 at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering without payment of further consideration. The shares have no expiration date. These shares are owned directly by SV Life Sciences Fund V, L.P. ("SVLS V LP"). SV Life Sciences Fund V (GP), LP ("SVLS V GP") is the general partner of SVLS V LP. The general partner of SVLS V GP is SVLSF V, LLC. Kate Bingham, James Garvey, Eugene D. Hill, III and Michael Ross are members of the investment committee of SVLSF V, LLC. SVLS V GP, SVLSF V, LLC and each of the individuals comprising the SVLSF V, LLC investment committee may be deemed to share voting, dispositive and investment power over the shares held of record by SVLS V LP. Each of SVLS V GP, SVLSF V, LLC and the individual members of the SVLSF V, LLC investment committee disclaims beneficial ownership of these securities and this report shall not be deemed to be an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or any other purpose, except to the extent of their pecuniary interest therein. These shares are owned directly by SV Life Sciences Fund V Strategic Partners, L.P. ("SVLS V SPP"). SVLS V GP is the general partner of SVLS V SPP. The general partner of SVLS V GP is SVLSF V, LLC. Kate Bingham, James Garvey, Eugene D. Hill, III and Michael Ross are members of the investment committee of SVLSF V, LLC. SVLS V GP, SVLSF V, LLC and each of the individuals comprising the SVLSF V, LLC investment committee may be deemed to share voting, dispositive and investment power over the shares held of record by SVLS V SPP. Each of SVLS V GP, SVLSF V, LLC and the individual members of the SVLSF V, LLC investment committee disclaims beneficial ownership of these securities and this report shall not be deemed to be an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or any other purpose, except to the extent of their pecuniary interest therein. These shares are owned directly by SV Life Sciences Fund VI, L.P. ("SVLS VI LP"). SV Life Sciences Fund VI (GP), LP ("SVLS VI GP") is the general partner of SVLS VI LP. The general partner of SVLS VI GP is SVLSF VI, LLC. Kate Bingham, James Garvey, Eugene D. Hill, III, Paul LaViolette, Thomas Flynn and Michael Ross are members of the investment committee of SVLSF VI, LLC. SVLS VI GP, SVLSF VI, LLC and each of the individuals comprising the SVLSF VI, LLC investment committee may be deemed to share voting, dispositive and investment power over the shares held of record by SVLS VI LP. Each of SVLS VI GP, SVLSF VI, LLC and the individual members of the SVLSF VI, LLC investment committee disclaims beneficial ownership of these securities and this report shall not be deemed to be an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or any other purpose, except to the extent of their pecuniary interest therein. These shares are owned directly by SV Life Sciences Fund VI Strategic Partners, L.P. ("SVLS VI SPP"). SVLS VI GP is the general partner of SVLS VI SPP. The general partner of SVLS VI GP is SVLSF VI, LLC. Kate Bingham, James Garvey, Eugene D. Hill, III, Paul LaViolette, Thomas Flynn and Michael Ross are members of the investment committee of SVLSF VI, LLC. SVLS VI GP, SVLSF VI, LLC and each of the individuals comprising the SVLSF VI, LLC investment committee may be deemed to share voting, dispositive and investment power over the shares held of record by SVLS VI SPP. Each of SVLS VI GP, SVLSF VI, LLC and the individual members of the SVLSF VI, LLC investment committee disclaims beneficial ownership of these securities and this report shall not be deemed to be an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or any other purpose, except to the extent of their pecuniary interest therein. Exhibit Index: 24.1 Power of Attorney 24.2 Power of Attorney 24.3 Power of Attorney 24.4 Power of Attorney 24.5 Power of Attorney 24.6 Power of Attorney /s/ Mike Gray, as attorney-in-fact on behalf of SVLSF V, LLC 2017-11-15 /s/ Mike Gray, as attorney-in-fact on behalf of SVLSF VI, LLC 2017-11-15 /s/ Mike Gray, as attorney-in-fact on behalf of SV Life Sciences Fund V, L.P. 2017-11-15 /s/ Mike Gray, as attorney-in-fact on behalf of SV Life Sciences Fund V Strategic Partners, L.P. 2017-11-15 /s/ Mike Gray, as attorney-in-fact on behalf of SV Life Sciences Fund VI, L.P. 2017-11-15 /s/ Mike Gray, as attorney-in-fact on behalf of SV Life Sciences Fund VI Strategic Partners, L.P. 2017-11-15