X0306 4 2020-05-18 0 0001730430 Kiniksa Pharmaceuticals, Ltd. KNSA 0001263508 BAKER BROS. ADVISORS LP 860 WASHINGTON STREET 3RD FLOOR NEW YORK NY 10014 1 0 1 0 0001551139 667, L.P. 860 WASHINGTON STREET, 3RD FLOOR NEW YORK NY 10014 1 0 1 0 0001580575 Baker Bros. Advisors (GP) LLC 860 WASHINGTON STREET 3RD FLOOR NEW YORK NY 10014 1 0 1 0 0001363364 Baker Brothers Life Sciences LP 860 WASHINGTON STREET 3RD FLOOR NEW YORK NY 10014 1 0 1 0 0001087940 BAKER FELIX 860 WASHINGTON STREET 3RD FLOOR NEW YORK NY 10014 1 0 1 0 0001087939 BAKER JULIAN 860 WASHINGTON STREET, 3RD FLOOR NEW YORK NY 10014 1 0 1 0 Class A1 Common Shares 2020-05-18 4 A 0 134397 18.25 A Class A Common Shares 134397 1050440 I See Footnotes Class A1 Common Shares 2020-05-18 4 A 0 1465603 18.25 A Class A Common Shares 1465603 10302952 I See Footnotes 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences" and together with 667, the "Funds") purchased 134,397 and 1,465,603 Class A1 common shares of Kiniksa Pharmaceuticals, Ltd. (the "Issuer"), respectively, for $18.25 per share pursuant to a private placement with the Issuer that closed on May 18, 2020. Represents the Issuer's Class A1 common shares which are subject to a beneficial ownership limitation, convertible at the election of the holder on a 1 for 1 basis into Class A common shares. The Class A1 common shares have no expiration date. Each Class A1 common share automatically converts into one Class A common share upon transfer, except for transfers to or between affiliated holders. Baker Bros. Advisors LP (the "Adviser") serves as the Investment Adviser to the Funds. In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds. Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose. After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Biotech Capital, L.P. and (ii) 667, Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in securities reported in column 9 of Table II directly held by 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to their interest in 667 and Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667. After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Brothers Life Sciences Capital, L.P. and (ii) Life Sciences, Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in the Issuer's securities reported in column 9 of Table II directly held by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to their interest in Life Sciences and Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences. Felix J. Baker, a managing member of Baker Bros. Advisors (GP) LLC and Dr. Stephen R. Biggar, a full-time employee of Baker Bros. Advisors LP are directors of Kiniksa Pharmaceuticals, Ltd. (the "Issuer"). By virtue of their representation on the board of directors of the Issuer, for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, the reporting persons are deemed directors by deputization of the Issuer. Baker Bros. Advisors LP, Name: Scott L. 2020-05-18 Baker Bros. Advisors LP, Mgmt. Co. and Inv. Adviser to 667, L.P., pursuant to authority granted by Baker Biotech Capital, L.P., GP to 667, L.P. Name: Scott L. Lessing, Title: President /s/ Scott L. Lessing 2020-05-18 By: Baker Bros. Advisors (GP) LLC, Name: Scott L. Lessing, Title: President /s/ Scott L. Lessing 2020-05-18 Baker Bros. Advisors LP, Mgmt. Co. and Inv. Adviser to BAKER BROTHERS LIFE SCIENCES, L.P., pursuant to authority granted by Baker Brothers Life Sciences Capital, L.P., GP to Baker Brothers Life Sciences, L.P., Name: Scott L. Lessing, Title: President /s/ 2020-05-18 /s/ Felix J. Baker 2020-05-18 /s/ Julian C. Baker 2020-05-18