Nature of Business Concert Pharmaceuticals, Inc., or the Company, was incorporated on April 12, 2006 as a Delaware corporation and has its operations based in Lexington, Massachusetts. The Company is a clinical stage biopharmaceutical company that is developing small molecule drugs that it discovered through the application of its deuterated chemical entity platform, or DCE Platform  . Selective incorporation of deuterium into known molecules has the potential, on a case-by-case basis, to provide better pharmacokinetic or metabolic properties, thereby enhancing their clinical safety, tolerability or efficacy. The Companys pipeline consists of clinical stage candidates targeting autoimmune and central nervous system, or CNS, disorders, and a number of preclinical compounds that it is currently assessing. Liquidity and Going Concern As of September 30, 2020, the Company had cash, cash equivalents and investments of $124.2 million and net working capital of $129.0 million. The Company has incurred cumulative net losses of $247.1 million since its inception and requires capital to continue future development activities. The Company does not have any products approved for sale and has not generated any revenue from product sales. The Company has funded its operations primarily through the public offering and private placement of its equity, debt financing, funding from collaborations and patent assignments, an asset sale and other arrangements. The Company expects its expenses to increase in connection with its ongoing activities, particularly as it initiates new clinical trials such as the Phase 3 trial of CTP-543 in alopecia areata. See Notes 12-14 for information regarding the Company's recently completed equity financings. The Company is subject to risks common to companies in the biotechnology industry, including, but not limited to, risks of failure or unsatisfactory results of nonclinical studies and clinical trials, the need to obtain additional financing to fund the future development of its pipeline, the need to obtain marketing approval for its product candidates, the need to successfully commercialize and gain market acceptance of its product candidates, dependence on key personnel, protection of proprietary technology, compliance with government regulations, development by competitors of technological innovations and ability to transition from pilot-scale manufacturing to large-scale production of products. Under Accounting Standards Codification, or ASC, Topic 205-40, Presentation of Financial Statements - Going Concern , management is required at each reporting period to evaluate whether there are conditions and events, considered in the aggregate, that raise substantial doubt about an entity's ability to continue as a going concern within one year after the date that the financial statements are issued. This evaluation initially does not take into consideration the potential mitigating effect of management's plans that have not been fully implemented as of the date the financial statements are issued. When substantial doubt exists, management evaluates whether the mitigating effect of its plans sufficiently alleviates the substantial doubt about the Company's ability to continue as a going concern. The mitigating effect of management's plans, however, is only considered if both (i) it is probable that the plans will be effectively implemented within one year after the date that the financial statements are issued and (ii) it is probable that the plans, when implemented, will mitigate the relevant conditions or events that raise substantial doubt about the entity's ability to continue as a going concern within one year after the date that the financial statements are issued. Generally, to be considered probable of being effectively implemented, the plans must have been approved by the Company's board of directors before the date that the financial statements are issued. Successful completion of the Companys development program and, ultimately, the attainment of profitable operations are dependent upon future events, including obtaining adequate financing to support the Companys cost structure and operating plan. Managements plans to alleviate its financing requirements include, among other things, pursuing one or more of the following steps to raise additional capital, none of which can be guaranteed or are entirely within the Companys control:  raise funding through the sale of the Company's common stock;  raise funding through debt financing; and  establish collaborations with potential partners to advance the Companys product pipeline. Based on the Companys current operating plan, management believes that its current cash, cash equivalents and available for sale investments will allow the Company to meet its liquidity requirements into the second half of 2021. The Company's history of significant losses, the negative cash flows from operations, the limited liquidity resources currently on hand and the dependence by the Company on its ability, about which there can be no certainty, to obtain additional financing to fund its operations after the current resources are exhausted raises substantial doubt about the Company's ability to continue as a going concern for a period of at least twelve months from the issuance date of this Quarterly Report on Form 10-Q. The accompanying condensed consolidated financial statements have been prepared on a going concern basis, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business, and do not include any adjustments that may result from the outcome of this uncertainty. If the Company is unable to raise capital when needed or on attractive terms, or if it is unable to procure collaboration arrangements to advance its programs, the Company would be forced to discontinue some of its operations or develop and implement a plan to further extend payables, reduce overhead or scale back its current operating plan until sufficient additional capital is raised to support further operations. There can be no assurance that such a plan would be successful.