Business	12 Months Ended
Dec. 31, 2019
Business
Business	1. Business Nature of Business Atreca, Inc. (the “Company”) was incorporated in the State of Delaware on June 11, 2010 (“inception date”), and is located in South San Francisco, California. In April 2016, the Company formed a wholly owned subsidiary, Atreca Pte. Ltd., in Singapore. The Company is a biopharmaceutical company utilizing its differentiated platform to discover and develop novel antibody-based immunotherapeutics to treat a range of solid tumor types. The Company's lead product candidate, ATRC-101, is a monoclonal antibody in clinical development with a novel mechanism of action and a target derived from an antibody identified using its discovery platform. The Company operates in a single segment. Since inception, the Company has been primarily engaged in research and development, raising capital, building its management team and building its intellectual property portfolio. Reverse Stock Split On June 7, 2019, the Company effected a 1-for-6 reverse stock split of all classes of its capital stock. Upon the effectiveness of the reverse stock split, (i) every one share of the Company’s outstanding capital stock was combined into one-sixth of one share of the same class and series of capital stock, (ii) the number of shares of its Class A common stock and its Series A preferred stock for which each outstanding option or warrant, to purchase its Class A common stock and its Series A preferred stock is exercisable was proportionally decreased on a 1-for-6 basis and (iii) the exercise price of each outstanding option or warrant to purchase its Class A common stock and its Series A preferred stock was proportionately increased on a 1-for-6 basis. The par value per share of its common stock and preferred stock were not adjusted as a result of the reverse stock split. Initial Public Offering In June 2019, the Company closed its initial public offering (“IPO”) of 6,452,500 shares of its Class A common stock and 2,000,000 shares of its Class B common stock at an offering price of $17.00 per share, including 1,102,500 shares pursuant to the underwriters’ option to purchase additional shares of the Company’s Class A common stock. The Company received net proceeds of $130.8 million, after deducting underwriting discounts and commissions of $10.1 million and offering expenses of $2.8 million. Immediately prior to the closing of the IPO, all outstanding shares of the Company’s convertible Series A preferred stock, convertible Series B preferred stock and convertible Series C1 preferred stock automatically converted into 13,314,068 shares of the Company’s Class A common stock and all outstanding shares of the Company’s convertible Series C2 preferred stock automatically converted into 3,934,191 shares of the Company’s Class B common stock. Immediately prior to the closing of the IPO, the Company issued 62,936 shares of Class A common stock upon the exercise of an outstanding warrant. The Company reclassified $209.7 million from temporary equity to Class A common stock, Class B common stock, and additional paid-in-capital on its consolidated balance sheet. Deferred Offering Cost Deferred offering costs of $2.8 million, consisting of legal, accounting and other fees and costs related to the IPO, were reclassified to additional paid-in capital as a reduction of the proceeds upon the closing of the IPO in June 2019. During the year ended December 31, 2019, $2.8 million of the deferred offering costs were paid.

1. Business

Nature of Business

Atreca, Inc. (the “Company”) was incorporated in the State of Delaware on June 11, 2010 (“inception date”), and is located in South San Francisco, California. In April 2016, the Company formed a wholly owned subsidiary, Atreca Pte. Ltd., in Singapore. The Company is a biopharmaceutical company utilizing its differentiated platform to discover and develop novel antibody-based immunotherapeutics to treat a range of solid tumor types. The Company's lead product candidate, ATRC-101, is a monoclonal antibody in clinical development with a novel mechanism of action and a target derived from an antibody identified using its discovery platform. The Company operates in a single segment. Since inception, the Company has been primarily engaged in research and development, raising capital, building its management team and building its intellectual property portfolio.

Reverse Stock Split

On June 7, 2019, the Company effected a 1-for-6 reverse stock split of all classes of its capital stock. Upon the effectiveness of the reverse stock split, (i) every one share of the Company’s outstanding capital stock was combined into one-sixth of one share of the same class and series of capital stock, (ii) the number of shares of its Class A common stock and its Series A preferred stock for which each outstanding option or warrant, to purchase its Class A common stock and its Series A preferred stock is exercisable was proportionally decreased on a 1-for-6 basis and (iii) the exercise price of each outstanding option or warrant to purchase its Class A common stock and its Series A preferred stock was proportionately increased on a 1-for-6 basis. The par value per share of its common stock and preferred stock were not adjusted as a result of the reverse stock split.

Initial Public Offering

In June 2019, the Company closed its initial public offering (“IPO”) of 6,452,500 shares of its Class A common stock and 2,000,000 shares of its Class B common stock at an offering price of $17.00 per share, including 1,102,500 shares pursuant to the underwriters’ option to purchase additional shares of the Company’s Class A common stock. The Company received net proceeds of $130.8 million, after deducting underwriting discounts and commissions of $10.1 million and offering expenses of $2.8 million. Immediately prior to the closing of the IPO, all outstanding shares of the Company’s convertible Series A preferred stock, convertible Series B preferred stock and convertible Series C1 preferred stock automatically converted into 13,314,068 shares of the Company’s Class A common stock and all outstanding shares of the Company’s convertible Series C2 preferred stock automatically converted into 3,934,191 shares of the Company’s Class B common stock. Immediately prior to the closing of the IPO, the Company issued 62,936 shares of Class A common stock upon the exercise of an outstanding warrant. The Company reclassified $209.7 million from temporary equity to Class A common stock, Class B common stock, and additional paid-in-capital on its consolidated balance sheet.

Deferred Offering Cost

Deferred offering costs of $2.8 million, consisting of legal, accounting and other fees and costs related to the IPO, were reclassified to additional paid-in capital as a reduction of the proceeds upon the closing of the IPO in June 2019. During the year ended December 31, 2019, $2.8 million of the deferred offering costs were paid.