RUBIUS THERAPEUTICS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(Unaudited)

1. Nature of the Business and Basis of Presentation

Rubius Therapeutics, Inc. (“Rubius” or the “Company”) is a biopharmaceutical company that is biologically engineering red blood cells into medicines, called Red Cell Therapeutics, for the treatment of cancer and autoimmune diseases. Rubius was incorporated in April 2013 as VL26, Inc. under the laws of the State of Delaware. In January 2015, the Company changed its name to Rubius Therapeutics, Inc.

The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, the ability to establish clinical- and commercial-scale manufacturing processes and the ability to secure additional capital to fund operations. In addition, the Company is subject to uncertainty regarding the performance and safety of its product candidates in humans. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s drug development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

The Company is monitoring the potential impact of the novel coronavirus (“COVID-19”), if any, on the carrying value of certain assets. To date, the Company has not experienced material business disruption, nor has it incurred impairment of any assets as a result of COVID-19. The extent to which these events may impact the Company’s business will depend on future developments, which are highly uncertain and cannot be predicted at this time. The duration and intensity of these impacts and resulting disruption to the Company’s operations is uncertain and the Company will continue to assess the financial impact.

On July 20, 2018, the Company completed its initial public offering (“IPO”), pursuant to which it issued and sold 12,055,450 shares of common stock, inclusive of 1,572,450 shares sold by the Company pursuant to the full exercise of the underwriters’ option to purchase additional shares. The aggregate net proceeds received by the Company from the IPO were $254.3 million, after deducting underwriting discounts and commissions and other offering costs. Upon the closing of the IPO, all of the shares of the Company’s outstanding convertible preferred stock then outstanding automatically converted into 51,845,438 shares of common stock.

On March 18, 2021, the Company completed an underwritten public offering (the “March 2021 Offering”), pursuant to which it issued and sold 6,896,552 shares of common stock. The aggregate net proceeds received by the Company from the March 2021 Offering were $187.2 million, after deducting underwriting discounts and commissions and other offering costs.

The accompanying condensed consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. The Company has incurred recurring losses since inception, including net losses of $52.4 million for the three months ended March 31, 2022 and $196.5 million for the year ended December 31, 2021. As of March 31, 2022, the Company had an accumulated deficit of $729.4 million. The Company expects to continue to generate operating losses in the foreseeable future.

The Company has financed its operations to date primarily through proceeds from private placements, its IPO, the March 2021 Offering and borrowings under credit facilities. The Company has devoted substantially all of its financial resources and efforts to research and development, including preclinical studies and clinical trials, and developing manufacturing capabilities. The Company will need to raise additional funds through public or private equity financings, debt financings, collaborations, strategic alliances or marketing, distribution or licensing arrangements to fund operations. The Company may not be able to obtain financing, or enter into collaboration or other arrangements, on

acceptable terms, or at all. Furthermore, the terms of any financing may adversely affect the holdings or the rights of the Company's stockholders. The Company implemented certain cost reduction actions in April 2022, which are intended to focus its capital on advancing its cancer and autoimmune programs and technology platform. If the Company is unable to obtain additional funding, it will implement further cost reduction actions that delay, scale back or discontinue some or all of its research and development programs and technology platform activities in order to further extend its forecasted cash runway. These actions could adversely affect its business prospects. As of May 10, 2022, the issuance date of the interim condensed consolidated financial statements, the Company expects that its cash, cash equivalents and investments will be sufficient to fund its operating expenses, capital expenditure requirements and debt service payments into the second half of 2023.

The Company’s condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”).

The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All intercompany accounts and transactions have been eliminated in consolidation. Certain prior period amounts have been reclassified to conform to the current year presentation.