Organization

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Organization

1. Organization

Annexon, Inc., or the Company, is a clinical-stage biopharmaceutical company pioneering a new class of complement medicines designed to stop the classical complement pathway at its start, C1q, in order to bring therapies to patients suffering from serious complement-mediated autoimmune, neurodegenerative and ophthalmic disorders. The Company is located in Brisbane, California and was incorporated in Delaware in March 2011.

The Company’s wholly-owned subsidiary, Annexon Biosciences Australia Pty Ltd, or the Subsidiary, is a proprietary limited company incorporated in 2016 and domiciled in Australia. The Subsidiary is also engaged in research and development activities in support of its parent company.

Initial Public Offering

On July 23, 2020, the Company’s registration statement on Form S-1 relating to its initial public offering, or the IPO, was declared effective by the SEC and the shares of its common stock began trading on the Nasdaq Global Select Market on July 24, 2020. The IPO closed on July 28, 2020, pursuant to which the Company issued and sold 14,750,000 shares of its common stock at a public offering price of $17.00 per share. On August 4, 2020, the Company issued 2,139,403 shares of its common stock to the underwriters of the IPO pursuant to the partial exercise of their option to purchase additional shares. The Company received net proceeds of approximately $262.4 million from the IPO, after deducting underwriting discounts and commissions of $20.1 million and offering costs of $4.6 million. Immediately prior to the completion of the IPO, all shares of redeemable convertible preferred stock then outstanding were converted into 20,824,938 shares of common stock.

Reverse Stock Split

On July 17, 2020, the Company’s board of directors approved an amendment to the Company’s certificate of incorporation to effect a reverse split of shares of the Company’s common stock on a one-for-8.81 basis, or the Reverse Stock Split. The number of authorized shares and the par values of the common stock and redeemable convertible preferred stock were not adjusted as a result of the Reverse Stock Split. In connection with the Reverse Stock Split, the conversion ratio for the Company’s outstanding redeemable convertible preferred stock was proportionately adjusted such that the common stock issuable upon conversion of such preferred stock was decreased in proportion to the Reverse Stock Split. All references to common stock and options to purchase common stock share data, per share data and related information contained in the consolidated financial statements have been adjusted to reflect the effect of the Reverse Stock Split.

Liquidity

Since inception, the Company has been involved primarily in performing research and development activities, conducting clinical trials, hiring personnel, and raising capital to support and expand these activities. The Company has experienced losses and negative cash flows from operations since its inception and, as of December 31, 2021, had an accumulated deficit of $296.3 million and cash and cash equivalents and short-term investments of $242.7 million.

The Company has historically funded its operations through the issuance of shares of its redeemable convertible preferred stock and common stock. Based on projected activities, management projects that cash on hand is sufficient to support operations for at least the next 12 months following issuance of these consolidated financial statements. Management expects to continue to incur losses and negative cash flows from operations for at least the next several years.