Andrew Sinclair - 01 Jul 2022 Form 4 Insider Report for Sierra Oncology, Inc.

Footnote F1

The securities of Sierra Oncology, Inc. (the "Issuer") are held by Abingworth Bioventures VII, LP ("ABV VII"). Abingworth LLP is the investment manager of ABV VII and has been delegated with all investment and dispositive power over the securities held by ABV VII. Reporting Person is a Partner and Portfolio Manager of Abingworth LLP.

Footnote F2

An investment committee approves investment and voting decisions by a majority vote, and no individual member has the sole control or voting power over the shares held by ABV VII. From time to time, the investment committee may delegate investment and voting authority over certain securities held by ABV VII to employees of Abingworth LLP subject to the supervision and oversight of the investment committee, including any limits on such authority imposed by the investment committee in its discretion and the right of the investment committee to revoke such authority at any time. The Reporting Person disclaims beneficial ownership of such shares, except to the extent of his pecuniary interest therein, if any.

Footnote F3

Reflects disposition in connection with the consummation of the transactions contemplated by the Agreement and Plan of Merger, dated as of April 12, 2022 (the "Merger Agreement"), between Sierra Oncology Inc. (the "Issuer"), GlaxoSmithKline plc ("GSK"), and Orikum Acquisition Inc. ("Acquisition Sub"). On July 1, 2022, upon the closing of the merger of Acquisition Sub with and into the Issuer (the "Merger") contemplated by the Merger Agreement, each share of common stock of the Issuer, par value $0.001 per share, was cancelled and automatically converted into the right to receive an amount in cash equal to $55.00, without interest and less any applicable withholding taxes.

Footnote F4

This option was granted to Dr. Andrew Sinclair as director's compensation. Dr. Sinclair is a Partner of Abingworth LLP. Under an agreement between Dr. Sinclair and Abingworth LLP, Dr. Sinclair is deemed to hold the options and any shares of Common Stock issuable upon exercise of the options for the benefit of ABV VII, and must exercise the options solely upon the direction of Abingworth LLP.

Footnote F5

ABV VII may be deemed the indirect beneficial owner of the option, and Dr. Sinclair may be deemed the indirect beneficial owner of the option through his indirect interest in ABV VII. Abingworth LLP disclaims beneficial ownership of the option except to the extent, if any, of its pecuniary interest therein. This report shall not be deemed an admission that Abingworth LLP, ABV VII, Dr. Sinclair or any other person is the beneficial owner of the securities reported herein for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.

Footnote F6

The option vested in equal monthly installments over a period of 12 months commencing on December 29, 2019, and was fully vested at the effective time of the Merger.

Footnote F7

The option vested as to 8.333% of the total shares monthly, commencing on July 9, 2020, and was fully vested at the effective time of the Merger.

Footnote F8

Pursuant to the Merger Agreement, at the effective time of the Merger all options that were outstanding and unexercised as of immediately prior to the effective time of the Merger accelerated vesting in full and were cancelled and converted into a right to receive an amount in cash, without interest, equal to the product of (1) the excess, if any, of $55.00 less the exercise price per share of such option, and (2) the number of shares of the Issuer's common stock issuable upon exercise in full of such option.

Footnote F9

At the effective time of the Merger, each warrant to purchase common stock of the Issuer (the "Series A warrants") that was outstanding as of immediately prior to the effective time of the Merger was cancelled and automatically converted into the right to receive an amount in cash equal to $45.98 per share of the Issuer's common stock subject to the Series A warrants.