Use of Estimates

The preparation of financial statements in conformity with GAAP in the United States requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, and related disclosures. On an ongoing basis, management evaluates its estimates including, but not limited to, those related to revenue recognition, revenue recognized under units-of-revenue method, equity securities, legal contingencies and stock-based compensation. The Company bases its estimates on historical experience and on various other market-specific and other relevant assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources.

Actual results may differ significantly from these estimates, such as the Company’s billing under government contracts and amortization of the payments received from HealthCare Royalty Partners II, L.P. (“HCRP”). Under the Company’s contracts with the National Institute of Allergy and Infectious Diseases (“NIAID”), a part of the National Institutes of Health (“NIH”), the Company billed using NIH’s provisional rates and thus is subject to future audits at the discretion of NIAID’s contracting office. In October of 2019, NIH notified the Company that it engaged KPMG to perform an audit of the Company’s incurred cost submissions for 2013, 2014 and 2015. The audit procedures were completed and the Company adjusted its estimated liability owed to NIH to $1.4 million as of December 31, 2020. The audit remains subject to further review by NIH as part of the contract close-out process and the Company may incur further liability as a result.  In addition, under the contracts with HCRP, the amortization for the reporting period is calculated based on the

payments expected to be made by the licensees to HCRP over the term of the arrangement. Any changes to the estimated payments by the licensees to HCRP can result in a material adjustment to revenue previously reported.

The COVID-19 pandemic has resulted in a global slowdown of economic activity which has led to delays and could result in further delays or terminations of some clinical trials underlying the Company’s royalty purchase agreements. Estimates and assumptions about future events and their effects cannot be determined with certainty and therefore require the exercise of judgment. These estimates may change, as new events occur and additional information is obtained, and are recognized in the condensed consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the Company’s financial statements.

Revenue Recognition

The Company recognizes revenue from all contracts with customers according to Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers ("ASC 606"), except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. The Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services.

To determine revenue recognition for arrangements that the Company determines are within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation based on relative fair values, when (or as) the performance obligation is satisfied.

The Company recognizes revenue from its license and collaboration arrangements and royalties. The terms of the arrangements generally include payment to the Company of one or more of the following: non-refundable, upfront license fees, development, regulatory and commercial milestone payments, and royalties on net sales of licensed products.

License of intellectual property

If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenue from non-refundable, upfront fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are bundled with other promises, such as transfer of related materials, process and know-how, the Company utilizes judgement to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time. Under the Company’s license agreements, the nature of the combined performance obligation is the granting of licenses to the customers as the other promises are not separately identifiable in the context of the arrangement. Since the Company grants the license to a customer as it exists at the point of transfer and is not involved in any future development or commercialization of the products related to the license, the nature of the license is a right to use the Company’s intellectual property as transferred. As such, the Company recognizes revenue related to the combined performance obligation upon completion of the delivery of the related materials, process and know-how (i.e., at a point in time).

Milestone payments

At the inception of each arrangement that includes development and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price. ASC 606 suggests two alternatives to use when estimating the amount of variable consideration: the expected value method and the most likely amount method. Under the expected value method, an entity considers the sum of probability-weighted amounts in a range of possible consideration amounts. Under the most likely amount method, an entity considers the single most likely amount in a range of possible consideration amounts. The Company uses the most likely amount method for development and regulatory milestone payments.

If it is probable that a significant cumulative revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis. The Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability or achievement of each such milestone and any related constraint, and if necessary, adjusts its estimates of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenue and earnings in the period of adjustment.

Royalties

For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied).

Upfront payments and fees are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Amounts payable to the Company are recorded as accounts receivable when the Company’s right to consideration is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less.

Stock-Based Compensation

The Company recognizes compensation expense for all stock-based payment awards made to the Company’s employees, consultants and directors that are expected to vest based on estimated fair values. The valuation of stock option awards is determined at the date of grant using the Black-Scholes Option Pricing Model (the “Black-Scholes Model”). The Black-Scholes Model requires inputs such as the expected term of the option, expected volatility and risk-free interest rate. To establish an estimate of expected term, the Company considers the vesting period and contractual period of the award and its historical experience of stock option exercises, post-vesting cancellations and volatility. The estimate of expected volatility is based on the Company’s historical volatility. The risk-free rate is based on the yield available on United States Treasury zero-coupon issues corresponding to the expected term of the award. The Company records forfeitures when they occur.

The Company records compensation expense for service-based awards on a straight-line basis over the requisite service period, which is generally the vesting period of the award, or to the date on which retirement eligibility is achieved, if shorter. For awards with performance-based conditions, at the point that it becomes probable that the performance conditions will be met, the Company records a cumulative catch-up of the expense from the grant date to the current date, and then amortizes the remainder of the expense over the remaining service period. Management evaluates when the achievement of a performance-based condition is probable based on the expected satisfaction of the performance conditions as of the reporting date. The amount of stock-based compensation expense recognized during a period is based on the value of the portion of the awards that are ultimately expected to vest.

The valuation of restricted stock units (“RSUs”) is determined at the date of grant using the Company’s closing stock price.

Purchase of Rights to Future Milestones and Royalties

The Company has purchased rights to receive a portion of certain future developmental, regulatory and commercial sales milestones, royalties, and option fees on sales of products currently in clinical development. The Company acquired such rights from various entities and recorded the amount paid for these rights as long-term royalty receivables (Note 5). In addition, the Company may be obligated to make contingent payments related to certain product development milestones, fees upon exercise of options related to future license products and sales-based milestones. The contingent payments are evaluated whether they are freestanding instruments or embedded derivatives. If freestanding instruments, the contingent payments are measured at fair value at the inception of the arrangement, subject to remeasurement to fair value each reporting period. Any changes in the estimated fair value is recorded in the consolidated statement of operations and comprehensive loss.

The Company accounts for milestone and royalty rights related to developmental pipeline products on a non-accrual basis using the cost recovery method. These developmental pipeline products are non-commercialized, non-approved products that require Food and Drug Administration (“FDA”) or other regulatory approval, and thus have uncertain cash flows. The Company is not yet able to reliably forecast future cash flows given their pre-commercial stages of development. The related receivable balance is classified as noncurrent since no payments are probable to be received in the near term. Under the cost recovery method, any milestone or royalty payment received is recorded as a direct reduction of the recorded receivable balance. When the recorded receivable balance has been fully collected, any additional amounts collected are recognized as revenue.

The Company reviews public information on clinical trials, press releases and updates from its partners regularly to identify any impairment indicators or changes in expected recoverability of the long-term receivable asset. If expected future cash flows discounted to the current period are less than the carrying value of the asset, the Company will record impairment. The impairment will be recognized by reducing the financial asset to an amount that represents the present value of the most recent estimate of future cash flows. No impairment indicators were identified, and no impairment was recorded as of December 31, 2020 and December 31, 2019.

Income Taxes

The Company accounts for income taxes using the liability method under which deferred tax assets and liabilities are determined based on differences between financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. Valuation allowances are established when necessary to reduce deferred tax assets to the amount which is more likely than not to be realizable.

The recognition, derecognition and measurement of a tax position is based on management’s best judgment given the facts, circumstances and information available at each reporting date. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense. To date, there have been no interest or penalties charged in relation to the unrecognized tax benefits.

Net Income (Loss) per Share Attributable to Common Stockholders

The Company calculates basic and diluted income (loss) per share attributable to common stockholders using the two-class method. The Company’s convertible Series X and Series Y preferred stocks participate in any dividends declared by the Company on its common stock and are therefore considered to be participating securities. The Company’s Series A Preferred Stock does not participate in any dividends or distribution by the Company on its common stock and is therefore not considered to be a participating security.

Under the two-class method, net income, as adjusted for any accumulated dividends on Series A Preferred Stock for the period and any deemed dividends related to beneficial conversion features on convertible preferred stock, if applicable, is allocated to each class of common stock and participating security as if all of the net income for the period had been distributed. Undistributed earnings allocated to participating securities are subtracted from net income in determining net income attributable to common stockholders. During periods of loss, the Company allocates no loss to participating securities because they have no contractual obligation to share in the losses of the Company. Basic net income (loss) per share attributable to common stockholders is then calculated by dividing the net income (loss) attributable to common stockholders by the weighted average number of shares of common stock outstanding during the period. All participating securities are excluded from the basic weighted average common shares outstanding.

Diluted net income (loss) per share attributable to common stockholders is based on the weighted average number of shares outstanding during the period, adjusted to include the assumed exercise of certain stock options and warrants for common stock. The calculation of diluted net income (loss) per share attributable to common stockholders requires that, to the extent the average market price of the underlying shares for the reporting period exceeds the exercise price of any

outstanding options or warrants, the presumed exercise of such securities are dilutive to net income (loss) per share attributable to common stockholders for the period. Adjustments to the denominator are required to reflect the related dilutive shares. The Company’s Series A Preferred Stock becomes convertible upon the occurrence of specific events other than the Company’s share price and therefore, is not included in the diluted shares until the contingency is resolved.

Accounting Pronouncements Recently Adopted

In August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2018-13, Fair Value Measurement (Topic 820) (“ASU 2018-13”), which modifies, removes and adds certain disclosure requirements on fair value measurements based on the FASB Concepts Statement, Conceptual Framework for Financial Reporting—Chapter 8: Notes to Financial Statements. The ASU is effective for the Company’s interim and annual reporting periods during the year ending December 31, 2020, and all annual and interim reporting period thereafter. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. Early adoption is permitted upon issuance of ASU 2018-13. An entity is permitted to early adopt any removed or modified disclosures upon issuance of ASU 2018-13 and delay adoption of the additional disclosures until their effective date. The Company early adopted the guidance related to removal of disclosures upon issuance of this ASU and adopted the deferred provisions as permitted under the ASU in the first quarter of 2020. The adoption of ASU 2018-13 did not have a material impact on the Company’s consolidated financial statements.

In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808) “Clarifying the Interaction between Topic 808 and Topic 606,” which requires transactions in collaborative arrangements to be accounted for under ASC 606 if the counterparty is a customer for a good or service that is a distinct unit of account. The new standard also precludes an entity from presenting consideration from transactions with a collaborator that is not a customer together with revenue recognized from contracts with customers. The ASU is effective for the Company’s interim and annual reporting periods during the year ending December 31, 2020, and all annual and interim reporting period thereafter. Early adoption is permitted, but no earlier than an entity’s adoption date of Topic 606. This ASU requires retrospective adoption to the date the Company adopted ASC 606, January 1, 2018, by recognizing a cumulative-effect adjustment to the opening balance of retained earnings of the earliest annual period presented. The Company may elect to apply the ASU retrospectively either to all contracts or only to contracts that are not completed at the date it initially applied ASC 606. The Company adopted ASU 2018-18 as of January 1, 2020. The adoption of ASU 2018-18 did not have a material impact on the Company’s consolidated financial statements.

Recent Accounting Pronouncements

In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. ASU 2016-13 replaced the incurred loss impairment methodology under current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. ASU 2016-13 requires use of a forward-looking expected credit loss model for accounts receivables, loans, and other financial instruments. Adoption of the standard requires using a modified retrospective approach through a cumulative-effect adjustment to retained earnings as of the effective date to align existing credit loss methodology with the new standard. ASU 2016-13 will be effective for all entities except public companies that are not smaller reporting companies for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years, using a modified retrospective approach. Early adoption is permitted. The Company

plans to adopt ASU 2016-13 and related updates as of January 1, 2023. The Company is currently evaluating the impact of adopting this new accounting guidance on its consolidated financial statements.

In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. The amendments in ASU 2019-12 are intended to simplify various aspects related to accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. ASU 2019-12 is effective for the Company on January 1, 2021. The Company is evaluating the impact of ASU 2019-12, but does not expect adopting this new accounting guidance will have a material impact on its consolidated financial statements.

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In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting. These amendments provide temporary optional guidance to ease the potential burden in accounting for reference rate reform. The ASU provides optional expedients and exceptions for applying generally accepted accounting principles to contract modifications and hedging relationships, subject to meeting certain criteria, that reference LIBOR or another reference rate expected to be discontinued. It is intended to help stakeholders during the global market-wide reference rate transition period. The guidance is effective for all entities as of March 12, 2020 through December 31, 2022 and can be adopted as of any date from the beginning of an interim period that includes or is subsequent to March 12, 2020. The Company is evaluating the impact of adopting this new accounting guidance on its consolidated financial statements.

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In August 2020, the FASB issued ASU 2020-06, Debt – Debt with Conversion and Other Options (Subtopic 470-20) and Derivative and Hedging – Contracts in Entity’s Own Equity (Subtopic 815-40). This ASU reduces the number of accounting models for convertible debt instruments and convertible preferred stock and amends the guidance for the derivatives scope exception for contracts in an entity’s own equity to reduce form-over-substance-based accounting conclusion. In addition, this ASU improves and amends the related EPS guidance. These amendments are effective for the Company for fiscal years beginning after December 15, 2023, including interim period within those fiscal years. Early adoption is permitted, but no earlier than fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. Adoption is either a modified retrospective method or a fully retrospective method of transition. The Company is currently evaluating the impacts of the provisions of ASU 2020-06 and the Company does not expect this ASU to have a material impact on its consolidated financial statements.