1.	The Company and Basis of Presentation

Organization and Description of Business

Sierra Oncology, Inc. (together with its subsidiaries, collectively referred to as the “Company”), a Delaware corporation, is a clinical stage drug development company advancing targeted therapeutics for the treatment of patients with cancer. Sierra Oncology’s lead drug candidate is SRA737, a potent, highly selective, orally bioavailable small molecule inhibitor of Checkpoint kinase 1 (Chk1), a key regulator of cell cycle progression and the DNA Damage Response (DDR) replication stress response. Sierra Oncology is also advancing SRA141, a potent, selective and orally bioavailable small molecule inhibitor of cell division cycle 7 kinase (Cdc7) undergoing preclinical development.

The Company’s primary activities since inception have been conducting research and development activities, conducting preclinical and clinical testing, recruiting personnel, performing business and financial planning, identifying and evaluating additional drug candidates for potential in-licensing or acquisition, and raising capital to support development activities.

The Company has not generated any product revenue related to its primary business purpose to date, nor has it generated any income, and is subject to a number of risks and uncertainties, which include dependence on key individuals, the need to identify and successfully develop commercially viable products, the need to obtain regulatory approval for its products and commercialize them, and the need to obtain adequate additional financing to fund the development of its product candidates.

Initial Public Offering

On July 15, 2015, the Company’s Registration Statement on Form S-1 (File No. 333-204921) relating to the initial public offering (IPO) of its common stock was declared effective by the Securities and Exchange Commission (SEC). Pursuant to such Registration Statement, the Company sold an aggregate of 9,315,000 shares of its common stock at a price of $17.00 per share for aggregate cash proceeds of approximately $143.6 million, net of underwriting discounts and commissions and offering costs.

On July 21, 2015, immediately prior to the closing of the IPO, all outstanding shares of convertible and redeemable convertible preferred stock converted into 18,361,953 shares of common stock, including an aggregate of 390,680 shares of common stock that were issued pursuant to the net exercise of 493,648 preferred stock warrants at the IPO price of $17.00 per share and an aggregate of 481,671 shares of common stock that were issued pursuant to the cash exercise of 481,671 preferred stock warrants. The IPO closed on July 21, 2015.

On the closing of the IPO, the Company paid $5.5 million to the holders of its Series B and B-1 redeemable convertible preferred stock in settlement of the cumulative dividends. In addition, the Company issued 750,946 shares of common stock to the holders of its Series C and D redeemable convertible preferred stock in settlement of the cumulative dividends.

Following the filing of the Restated Certificate of Incorporation of the Company on July 21, 2015, the number of shares of capital stock the Company is authorized to issue is 510,000,000 shares, of which 500,000,000 shares may be common stock and 10,000,000 shares may be preferred stock. Both the common stock and the preferred stock have a par value of $0.001 per share.

Follow On Offering

On February 14, 2017, the Company completed an underwritten public offering of 19,500,000 shares of common stock. As part of the underwritten public offering, on February 21, 2017 the Company issued an additional 2,347,636 shares of common stock representing the underwriters’ exercise of a majority of their over-allotment option. All shares were offered by the Company at a price to the public of $1.35 per share. The aggregate net proceeds received by the Company from the offering were $27.4 million, net of underwriting discounts and commissions and offering expenses of $2.1 million.

Reverse Stock Split

On June 29, 2015, the Company’s Board of Directors approved an amendment to the Company’s Amended and Restated Certificate of Incorporation to effect a reverse split of the Company’s common stock, convertible preferred stock and redeemable convertible preferred stock at a 7.45-to-1 ratio (Reverse Stock Split). The Reverse Stock Split became effective on July 2, 2015, upon the filing of the amendment to the Company’s Amended and Restated Certificate of Incorporation. The authorized shares and par value of the common, convertible preferred and redeemable convertible preferred stock were not adjusted as a result of the Reverse Stock Split. All issued and outstanding common stock, convertible preferred stock, redeemable convertible preferred stock, warrants to purchase preferred stock, options to purchase common stock and per share amounts contained in the consolidated financial statements have been retroactively adjusted to reflect this Reverse Stock Split for all periods presented.