Nature of Organization and Operations	3 Months Ended
Mar. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Organization and Operations	1. Nature of Organization and Operations Apellis Pharmaceuticals, Inc. (the “Company”) is a clinical-stage biopharmaceutical company focused on the development of novel therapeutic compounds to treat disease through the inhibition of the complement system, which is an integral component of the immune system, at the level of C3, the central protein in the complement cascade. The Company was incorporated in September 2009 under the laws of the State of Delaware and has its principal office in Waltham, Massachusetts. The Company’s operations since inception have been limited to organizing and staffing the Company, acquiring rights to product candidates, business planning, raising capital and developing its product candidates. The Company is subject to risks common in the biotechnology industry including, but not limited to, raising additional capital, development by its competitors of new technological innovations, its ability to successfully complete preclinical and clinical development of product candidates and receive timely regulatory approval of products, market acceptance of the Company’s products, protection of proprietary technology, healthcare cost containment initiatives, and compliance with governmental regulations, including those of the U.S. Food and Drug Administration (“FDA”). Additionally, the Company is subject to risks arising from the Coronavirus Disease 2019 (COVID-19) pandemic, which could have adverse effects upon our business and operations, including on our ability to initiate, conduct and complete clinical trials. Follow-on Public Offerings On January 13, 2020, the Company issued and sold 10,925 shares of its common stock at a price per share to the public of $37.00 in a follow-on public offering including an additional 1,425 shares of its common stock that were sold at the follow-on public offering price of $37.00 per share pursuant to the underwriters’ in full exercise of their option to purchase additional shares of common stock. The Company received net proceeds of $381.5 million after deducting underwriting discounts and commissions of $22.2 million and offering costs of $0.5 million for these transactions. Liquidity and Financial Condition The accompanying unaudited condensed consolidated financial statements have been prepared on the basis of the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. As of April 29, 2020, the date of issuance of these unaudited condensed consolidated financial statements, the Company believes that its cash and cash equivalents of $417.9 million and marketable securities of $228.8 million as of March 31, 2020 will be sufficient to fund its operations and capital expenditure requirements for at least the next twelve months from the date of issuance of the unaudited interim consolidated financial statements. The future viability of the Company beyond that point is dependent on its ability to raise additional capital to finance its operations. The Company is subject to risks common to other life science companies in the development stage including, but not limited to, uncertainty of product development and commercialization, lack of marketing and sales history, development by its competitors of new technological innovations, dependence on key personnel, market acceptance of products, product liability, protection of proprietary technology, ability to raise additional financing, and compliance with FDA and other government regulations. If the Company does not successfully commercialize any of its product candidates, it will be unable to generate recurring product revenue or achieve profitability. Management’s plans in order to meet its short-term and longer-term operating cash flow requirements include obtaining additional funding. There are uncertainties associated with the Company’s ability to (1) obtain additional debt or equity financing on terms that are favorable to the Company (2) enter into collaborative agreements with strategic partners, and (3) succeed in its future operations. If the Company is not able to obtain the required funding for its operations, or is not able to obtain such funding on terms that are favorable to the Company, it could be forced to delay, reduce or eliminate its research and development programs or future commercialization efforts and its business could be materially harmed.

Nature of Organization and Operations

3 Months Ended

Mar. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

1. Nature of Organization and Operations

Apellis Pharmaceuticals, Inc. (the “Company”) is a clinical-stage biopharmaceutical company focused on the development of novel therapeutic compounds to treat disease through the inhibition of the complement system, which is an integral component of the immune system, at the level of C3, the central protein in the complement cascade.

The Company was incorporated in September 2009 under the laws of the State of Delaware and has its principal office in Waltham, Massachusetts.

The Company’s operations since inception have been limited to organizing and staffing the Company, acquiring rights to product candidates, business planning, raising capital and developing its product candidates.

The Company is subject to risks common in the biotechnology industry including, but not limited to, raising additional capital, development by its competitors of new technological innovations, its ability to successfully complete preclinical and clinical development of product candidates and receive timely regulatory approval of products, market acceptance of the Company’s products, protection of proprietary technology, healthcare cost containment initiatives, and compliance with governmental regulations, including those of the U.S. Food and Drug Administration (“FDA”). Additionally, the Company is subject to risks arising from the Coronavirus Disease 2019 (COVID-19) pandemic, which could have adverse effects upon our business and operations, including on our ability to initiate, conduct and complete clinical trials.

Follow-on Public Offerings

On January 13, 2020, the Company issued and sold 10,925 shares of its common stock at a price per share to the public of $37.00 in a follow-on public offering including an additional 1,425 shares of its common stock that were sold at the follow-on public offering price of $37.00 per share pursuant to the underwriters’ in full exercise of their option to purchase additional shares of common stock. The Company received net proceeds of $381.5 million after deducting underwriting discounts and commissions of $22.2 million and offering costs of $0.5 million for these transactions.

Liquidity and Financial Condition

The accompanying unaudited condensed consolidated financial statements have been prepared on the basis of the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. As of April 29, 2020, the date of issuance of these unaudited condensed consolidated financial statements, the Company believes that its cash and cash equivalents of $417.9 million and marketable securities of $228.8 million as of March 31, 2020 will be sufficient to fund its operations and capital expenditure requirements for at least the next twelve months from the date of issuance of the unaudited interim consolidated financial statements. The future viability of the Company beyond that point is dependent on its ability to raise additional capital to finance its operations.

The Company is subject to risks common to other life science companies in the development stage including, but not limited to, uncertainty of product development and commercialization, lack of marketing and sales history, development by its competitors of new technological innovations, dependence on key personnel, market acceptance of products, product liability, protection of proprietary technology, ability to raise additional financing, and compliance with FDA and other government regulations. If the Company does not successfully commercialize any of its product candidates, it will be unable to generate recurring product revenue or achieve profitability. Management’s plans in order to meet its short-term and longer-term operating cash flow requirements include obtaining additional funding.

There are uncertainties associated with the Company’s ability to (1) obtain additional debt or equity financing on terms that are favorable to the Company (2) enter into collaborative agreements with strategic partners, and (3) succeed in its future operations. If the Company is not able to obtain the required funding for its operations, or is not able to obtain such funding on terms that are favorable to the Company, it could be forced to delay, reduce or eliminate its research and development programs or future commercialization efforts and its business could be materially harmed.