Nature of the Business (Policies)

12 Months Ended

Dec. 31, 2017

On January 19, 2016, the Company effected a 1-for-10.8102 reverse stock split of its issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios for each series of the Company’s Preferred Stock (see Note 10). Accordingly, all share and per share amounts for all periods presented in the accompanying financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect this reverse stock split and adjustment of the preferred stock conversion ratios.

Public Offerings

In February 2016, the Company issued and sold 6,250,000 shares of its common stock in its initial public offering (“IPO”) at a public offering price of $8.00 per share, for net proceeds of $42.5 million after deducting underwriting discounts and commissions of $3.5 million and other offering expenses of $4.0 million. Upon the closing of the IPO, all shares of convertible preferred stock then outstanding converted into an aggregate of 9,699,600 shares of common stock, and the Company issued 2,590,742 shares of common stock as payment of $36.0 million of accruing dividends due to holders of Series A preferred stock. In addition, the Company’s convertible preferred stock warrant outstanding at the close of the IPO converted to a warrant to purchase common stock.

In connection with the completion of the IPO, the Company amended its certificate of incorporation to authorize the future issuance of up to 5,000,000 shares of undesignated preferred stock, par value $0.001 per share. As of December 31, 2017 and 2016, there were no shares of preferred stock issued or outstanding.

In September 2016, the Company issued and sold 5,750,000 shares of its common stock in a public offering at a public offering price of $13.00 per share, for net proceeds of $69.5 million after deducting underwriter discounts and commissions of $4.5 million and other offering expenses of $0.8 million. The foregoing includes the exercise by the underwriters of their options to purchase an additional 750,000 shares of the Company’s common stock within 30 days following the date of the final prospectus for the offering.

In December 2017, the Company issued and sold 9,200,000 shares of its common stock in a public offering at a public offering price of $5.00 per share, for net proceeds of $42.9 million after deducting underwriting discounts and commissions of $2.8 million and other offering expenses of $0.3 million. The foregoing includes the exercise by the underwriters of their option to purchase an additional 1,200,000 shares of the Company’s common stock within 30 days following the date of the final prospectus for the offering.

Basis of Presentation

The financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”).

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and assumptions reflected in these financial statements include, but are not limited to, revenue recognition, the accrual for research and development expenses, including clinical trials, and the valuation of common stock, preferred stock warrant liability, derivative liability and build-to-suit lease obligation. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.

Concentrations of Credit Risk and Significant Customers

Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents, short-term investments and accounts receivable. The Company mitigates its risk with respect to cash, cash equivalents and short-term investments by maintaining its balances at two accredited financial institutions, in amounts that exceed federally insured limits. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company’s accounts receivable balances are due from the counterparty to its collaboration agreements (see Note 13) that the Company believes to be creditworthy. As of December 31, 2016, accounts receivable consisted of amounts due from one such counterparty.

Deferred Offering Costs

The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ equity (deficit) as a reduction of additional paid-in capital generated as a result of the offering. As of December 31, 2015, the Company had recorded $2.7 million of deferred offering costs in contemplation of the Company’s IPO, which was completed on February 11, 2016. In conjunction with the completion of the IPO, the Company reclassified $4.0 million of deferred financing costs to additional paid-in capital as a reduction of the proceeds from the IPO. In September 2016, the Company reclassified $0.8 million of deferred financing costs to additional paid-in capital as a reduction of the proceeds from the follow-on public offering. In December 2017, the Company reclassified less than $0.4 million of deferred financing costs to additional paid-in capital as a reduction of the proceeds from its public offering, of which $0.3 million is included within accrued expenses and accounts payable as of December 31, 2017.

Cash Equivalents

The Company considers all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash equivalents. As of December 31, 2017, the Company’s cash equivalents consisted of money market funds, U.S. government-sponsored securities and U.S. treasury securities. The Company’s cash equivalents as of December 31, 2016 consisted of money market funds.

Restricted Cash

As of December 31, 2017and 2016, short term restricted cash consisted of a certificate of deposit collateralizing a letter of credit issued as a security deposit in connection with the Company’s lease of its corporate facilities at 200 Technology Square, Cambridge, MA.

On September 19, 2017, the Company entered into a lease agreement for a new corporate headquarters at 80 Guest Street, Brighton, MA (see Note 16). As of December 31, 2017, long term restricted cash consisted of a money market account in the amount of $1.7 million collateralizing a letter of credit issued as a security deposit for this lease agreement.

Short-Term Investments

Short-term investments represent holdings of available-for-sale marketable securities in accordance with the Company’s investment policy and cash management strategy. Short-term investments mature within one-year from the balance sheet date. Investments in marketable securities are recorded at fair value, with any unrealized gains and losses, net of taxes, reported as a component of stockholders’ equity until realized or until a determination is made that an other-than-temporary decline in market value has occurred. The cost of marketable securities sold is determined based on the specific identification method and any realized gains or losses on the sale of investments are reflected as a component of other expense, net.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are charged to expense as incurred.

Impairment of Long-Lived Assets

Long-lived assets consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset group for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset group to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset group are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset group over its fair value, determined based on discounted cash flows. To date, the Company has not recorded any impairment losses on long-lived assets.

Fair Value Measurements

Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

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Level 1—Quoted prices in active markets for identical assets or liabilities.

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Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.

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Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques.

The Company’s investments and its derivative liability are carried at fair value determined according to the fair value hierarchy described above (see Note 4). The carrying value of accounts receivable, accounts payable and accrued expenses approximate their fair value due to the short-term nature of these assets and liabilities.

Segment Information

The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is developing therapeutics to treat protein conformational diseases. All of the Company’s tangible assets are held in the United States. To date, all of the Company’s revenue has been generated in the United States.

Revenue Recognition

The Company recognizes revenue in accordance with Accounting Standards Codification (“ASC”) Topic 605, Revenue Recognition. Accordingly, the Company recognizes revenue for each unit of accounting when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; the seller’s price to the buyer is fixed or determinable; and collectability is reasonably assured.

The Company records as deferred revenue any amounts received prior to satisfying the revenue recognition criteria. Deferred revenue not expected to be recognized within the next twelve months is reported as non-current deferred revenue.

Collaborative Research and License Agreements

The terms of these agreements contain multiple deliverables, which may include licenses and research and development activities. The terms of these agreements may also include nonrefundable upfront license fees, payments for research and development activities, reimbursement of certain third-party costs, payments based upon the achievement of specified milestones, and royalty payments based on product sales derived from the collaboration.

The Company evaluates multiple-element arrangements based on the guidance in ASC Topic 605-25, Revenue Recognition—Multiple-Element Arrangements (“ASC 605-25”). Pursuant to the guidance in ASC 605-25, the Company evaluates multiple-element arrangements to determine (1) the deliverables included in the arrangement and (2) whether the individual deliverables represent separate units of accounting or whether they must be accounted for as a combined unit of accounting. When deliverables are separable, consideration received is allocated to the separate units of accounting based on the relative selling price method and the appropriate revenue recognition principles are applied to each unit. When the Company determines that an arrangement should be accounted for as a single unit of accounting, the Company must determine the period over which the performance obligations will be performed and revenue will be recognized. This evaluation requires the Company to make judgments about the individual deliverables and whether such deliverables are separable from the other aspects of the contractual relationship. Deliverables are considered separate units of accounting provided that the delivered item has value to the customer on a standalone basis and, if the arrangement includes a general right of return with respect to the delivered item, delivery or performance of the undelivered item is considered probable and substantially in the Company’s control. In assessing whether an item has standalone value, the Company considers factors such as the research, development, manufacturing and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the collaboration partner can use any other deliverable for its intended purpose without the receipt of the remaining deliverable, whether the value of the deliverable is dependent on the undelivered item, and whether there are other vendors that can provide the undelivered items.

The consideration received under the arrangement that is fixed or determinable is then allocated among the separate units of accounting based on the relative selling prices of the separate units of accounting. The Company determines the selling price of a unit of accounting within each arrangement following the hierarchy of evidence prescribed by ASC 605-25. Accordingly, the Company determines the estimated selling price for units of accounting within each arrangement using vendor-specific objective evidence (“VSOE”), if available; third-party evidence (“TPE”) of selling price if VSOE is not available; or best estimate of selling price (“BESP”), if neither VSOE nor TPE is available. The Company typically uses BESP to estimate the selling price as it generally does not have VSOE or TPE of selling price for its units of accounting. Determining the BESP for a unit of accounting requires significant judgment. In developing the BESP for a unit of accounting, the Company considers applicable market conditions and relevant entity-specific factors, including factors that were contemplated in negotiating the agreement with the customer and estimated costs. The Company validates the BESP for units of accounting by evaluating whether changes in the key assumptions used to determine the BESP will have a significant effect on the allocation of arrangement consideration between multiple units of accounting.

The Company recognizes arrangement consideration allocated to each unit of accounting when all of the revenue recognition criteria in ASC 605 are satisfied for that particular unit of accounting. In the event that a deliverable does not represent a separate unit of accounting, the Company recognizes revenue from the combined unit of accounting over the contractual or estimated performance period for the undelivered items, which is typically the term of the Company’s research and development obligations. If there is no discernible pattern of performance or objectively measurable performance measures do not exist, then the Company recognizes revenue under the arrangement on a straight-line basis over the period the Company is expected to complete its performance obligations. Conversely, if the pattern of performance over which the service is provided to the customer can be determined and objectively measurable performance measures exist, then the Company recognizes revenue under the arrangement using the proportional performance method. Revenue recognized is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the straight-line method or proportional performance method, as applicable, as of the period ending date. At the inception of an arrangement that includes milestone payments, the Company evaluates whether each milestone is substantive and at risk to both parties on the basis of the contingent nature of the milestone. This evaluation includes an assessment of whether: (1) the consideration is commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the delivered item as a result of a specific outcome resulting from the Company’s performance to achieve the milestone, (2) the consideration relates solely to past performance, and (3) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company evaluates factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the particular milestone and the level of effort and investment required to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether a milestone satisfies all of the criteria required to conclude that a milestone is substantive. The Company will recognize revenue in its entirety upon successful accomplishment of any substantive milestones, assuming all other revenue recognition criteria are met. Milestones that are not considered substantive are recognized as earned if there are no remaining performance obligations or over the remaining period of performance, with a cumulative catch-up for the elapsed portion of the research term, assuming all other revenue recognition criteria are met.

Research Grant Contracts

Under these contracts, the Company is typically compensated for specific research or development activities. The Company recognizes revenue as the activities specified under the research grant contracts are performed and all of the revenue recognition criteria in ASC 605 are satisfied.

Adoption of ASC 606

The Company will adopt new revenue accounting guidance in the first quarter of 2018, which it expects to impact this policy, the amount and timing of our future revenue recognition, and the amount of revenue previously recognized in our published financial statements. For further discussion, see Recent Accounting Pronouncements in this note below.

Embedded Derivatives

Embedded derivatives that are required to be bifurcated from the underlying host instrument are accounted for and valued as a separate financial instrument. An embedded derivative exists associated with an alternate payment option upon change of control within the research, development and commercialization agreement with Cystic Fibrosis Foundation Therapeutics, Inc. (see Note 13). The embedded derivative has been bifurcated and is classified as a liability on the balance sheet and separately accounted for at its fair value. The derivative liability is marked-to-market every reporting period. Changes in fair value of the derivative liability are recognized as a component of other income (expense), net in the accompanying statement of operations and comprehensive loss.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development expenses are comprised of costs incurred in performing research and development activities, including salaries, stock-based compensation and benefits, facilities costs, depreciation, third-party license fees, and external costs of outside vendors engaged to conduct preclinical development activities and clinical trials. Research and development expenses include the Company’s costs of performing services in connection with its collaboration agreements and research grant.

Nonrefundable prepayments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized. Such amounts are recognized as an expense as the goods are delivered or the related services are performed, or until it is no longer expected that the goods will be delivered or the services rendered.

Research Contract Costs and Accruals

The Company has entered into various research and development contracts with research institutions and other companies both inside and outside of the United States. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.

Patent Costs

All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.

Preferred Stock Warrant Liability

Through February 2016, the Company classified a warrant to purchase shares of its Series A preferred stock as a liability on its balance sheets as this warrant was a free-standing financial instrument could have required the Company to transfer assets upon exercise. The warrant was initially recorded at fair value on date of grant and subsequently remeasured to fair value at each balance sheet date. Changes in fair value of the warrant were recognized as a component of other income (expense), net in the statement of operations. Following the reverse stock split of the common stock of the Company and the completion of the Company’s IPO in February 2016, the warrant became a warrant to purchase 14,800 shares of common stock. At that time, the warrant was reclassified to a component of stockholder’s equity and is no longer subject to remeasurement.

The Company used the Black-Scholes option-pricing model, which incorporates assumptions and estimates, to value the preferred stock warrant. The Company has assessed these assumptions and estimates on a quarterly basis as additional information impacting the assumptions is obtained. Estimates and assumptions impacting the fair value measurement include the fair value per share of the underlying Series A preferred stock, the remaining contractual term of the warrant, risk-free interest rate, expected dividend yield and expected volatility of the price of the underlying preferred stock. The Company determined the fair value per share of the underlying preferred stock by taking into consideration the most recent sales of its convertible preferred stock, results obtained from third-party valuations and additional factors that are deemed relevant. Up until February 2016, the Company was a private company and therefore lacks company-specific historical and implied volatility information of its stock. Therefore, it estimates its expected stock volatility based on the historical volatility of publicly traded peer companies for a term equal to the remaining contractual term of the warrant. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve for time periods approximately equal to the remaining contractual term of the warrant. Expected dividend yield is determined considering that the underlying Series A preferred stock is entitled to dividends of 8.0% per year, whether or not declared.

Stock-Based Compensation

The Company measures all stock options and other stock-based awards granted to employees and directors based on the fair value on the date of the grant and recognizes compensation expense of those awards, net of estimated forfeitures, over the requisite service period, which is generally the vesting period of the respective award. Generally, the Company issues stock options and restricted stock awards to employees with only service- based vesting conditions and records the expense for these awards using the straight-line method.

The Company measures stock-based awards granted to consultants and non-employees based on the fair value of the award on the date on which the related service is complete. Compensation expense is recognized over the period during which services are rendered by such consultants and non-employees until completed. At the end of each financial reporting period prior to completion of the service, the fair value of these awards is remeasured using the then-current fair value of the Company’s common stock and updated assumption inputs in the Black-Scholes option-pricing model. The Company does not recognize compensation expense for awards with performance-based vesting conditions granted to consultants and non-employees for which satisfaction of the performance conditions is not solely within the control of the holder until the performance conditions have been met.

The Company classifies stock-based compensation expense in its statement of operations in the same manner in which the award recipient’s payroll costs are classified or in which the award recipients’ service payments are classified.

Prior to January 1, 2017, the Company recognized compensation expense for only the portion of awards that are expected to vest. In developing a forfeiture rate estimate, the Company has considered its historical experience to estimate pre- vesting forfeitures for service-based awards. Effective January 1, 2017, the company adopted ASU No. 2016-09 on a modified retrospective basis. As a result, the Company has made an accounting policy election to account for forfeitures as they occur.

The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option- pricing model. The Company historically has been a private company and lacks company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The expected term of stock options granted to non-employees is equal to the contractual term of the option award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends on common stock and does not expect to pay any cash dividends in the foreseeable future.

Comprehensive Loss

Comprehensive loss includes net loss as well as other changes in stockholders’ equity (deficit) that result from transactions and economic events other than those with stockholders. For the years ended December 31, 2017 and 2016, comprehensive loss included less than $0.1 million of unrealized gains and less than $0.1 million of unrealized losses on short-term investments, respectively. There was no difference between net loss and comprehensive loss for the year ended December 31, 2015.

Income Taxes

The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the financial statements or in the Company’s tax returns. Deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies.

The Company accounts for uncertainty in income taxes recognized in the financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.

Net Loss per Share

Basic net loss per share is computed using the weighted average number of common shares outstanding during the period. Diluted net loss per share is computed using the sum of the weighted average number of common shares outstanding during the period and, if dilutive, the weighted average number of potential shares of common stock, including the assumed exercise of stock options and unvested restricted stock. Net loss per share attributable to common stockholders is calculated using the two-class method, which is an earnings allocation formula that determines net loss per share for the holders of the Company’s common shares and participating securities. The Company’s convertible preferred stock contains participation rights in any dividend paid by the Company and are deemed to be participating securities. Net loss attributable to common stockholders and participating preferred shares are allocated to each share on an as-converted basis as if all of the earnings for the period had been distributed. The participating securities do not include a contractual obligation to share in losses of the Company and are not included in the calculation of net loss per share in the periods that have a net loss.

Diluted net loss per share is computed using the more dilutive of (a) the two-class method or (b) the if- converted method. The Company allocates earnings first to preferred stockholders based on dividend rights and then to common and preferred stockholders based on ownership interests. The weighted average number of common shares included in the computation of diluted net loss gives effect to all potentially dilutive common equivalent shares, including outstanding stock options, warrants, preferred stock and the potential issuance of stock upon the conversion of the Company’s convertible notes. Common stock equivalent shares are excluded from the computation of diluted net loss per share if their effect is antidilutive.

In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss attributable to common stockholders for the years ended December 31, 2017, 2016 and 2015.

Recently Issued Accounting Pronouncements

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which supersedes existing revenue recognition guidance under GAAP. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The standard defines a five-step process to achieve this principle, and will require companies to use more judgment and make more estimates than under the current guidance. The Company expects that these judgments and estimates will include identifying performance obligations in the customer contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. ASU 2014-09 also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which delays the effective date of ASU 2014-09 such that the standard is effective for public entities for annual periods beginning after December 15, 2017 and for interim periods within those fiscal years. In April 2016, the FASB issued ASU 2016-10, Identifying Performance Obligations and Licensing, which clarifies two aspects of ASU 2014-09, Revenue from Contracts with Customers (Topic 606): identifying performance obligations and the licensing implementation guidance. These new standards will become effective for the Company on January 1, 2018. Companies have the option of applying this new guidance retrospectively to each prior reporting period presented (the full retrospective method) or retrospectively with the cumulative effect of initially applying this update recognized at the date of initial application (the modified retrospective method). The Company only has one contract (see Note 13) within the scope of Topic 606 and intends to use the modified retrospective method for adoption. Since the inception of the contract, the Company has recognized $9.7 million in revenue.

The Company is assessing, but has not yet completed its assessment of the impact of the adoption of this standard on its consolidated financial statements and related disclosures. Currently, the Company anticipates a potential impact on the revenue recognition method used to recognize revenue under its agreement with Astellas and the accounting for research funding payments based on a specified rate for time incurred as well as the recognition of milestone revenue prior to achievement. The expected impact is further described below. Estimated impacts from the adoption of this standard could differ upon the final adoption and implementation of the standard.

Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of ASC 606, the entity 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 entity satisfies a performance obligation. ASC 606 also impacts certain other areas, such as the accounting for costs to obtain or fulfill a contract.

With respect to its collaboration with Astellas, the Company currently expects the one performance obligation identified under the provisions of ASC 606 will be consistent with the one unit of accounting identified under the provisions of ASC 605. However, as previously described, it currently expects that the pattern of revenue recognition under step (v) above will differ from the pattern of revenue recognition under ASC 605. Any change in the timing or pattern of revenue recognition will have a corresponding change to the Company’s deferred revenue balance.

The Company expects the accounting for research funding payments and milestone payments under its agreement to change under ASC 606. Revenue from research funding and milestone payments may be recognized earlier under ASC 606 than under ASC 605. Under ASC 605, upon being earned or achieved, these payments were being recognized as revenue over the three and a half year research term of the agreement, which commenced in January 2015, with a cumulative catch-up for the elapsed portion of the research term being recognized at the time any such payments are earned. The adoption of ASC 606 may result in the recognition of revenue related to these payments over the three and a half year research term before being earned or achieved. For the milestone payments, this recognition is based on assessment of the probability of achievement of the milestone event and the likelihood of a significant reversal of such milestone revenue at each reporting date.

ASC 606 requires more robust disclosures than required by previous guidance, including disclosures related to disaggregation of revenue into appropriate categories, performance obligations, the judgments made in revenue recognition determinations, adjustments to revenue which relate to activities from previous quarters or years, any significant reversals of revenue, and costs to obtain or fulfill contracts.

In February 2016, the FASB issued ASU No. 2016-02, Leases. This guidance will require that lease arrangements longer than 12 months result in an entity recognizing an asset and liability equal to the present value of the lease payments in the statement of financial position. This guidance is effective for annual periods beginning after December 15, 2018, and interim periods therein. This standard requires a modified retrospective transition approach for all leases existing at, or entered into after, the date of initial application, with an option to use certain transition relief. Early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2016-02 will have on its financial statements and related disclosures.

In March 2016, the FASB issued ASU No. 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. The new standard involves several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities and classification on the statement of cash flows. The new standard was adopted by the Company on January 1, 2017 on a modified retrospective basis. As a result, the Company has made an accounting policy election to account for forfeitures as they occur. The adoption of ASU 2016‑09 also requires excess tax benefits and tax deficiencies be recorded in the income statement as opposed to additional paid‑in capital when the awards vest or are settled. This had no material impact on the condensed financial statements as of and for year ended December 31, 2017.

In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. The new standard clarifies certain aspects of the statement of cash flows, including the classification of debt prepayment or debt extinguishment costs, settlement of zero-coupon debt instruments or other debt instruments with coupon interest rates that are insignificant in relation to the effective interest rate of the borrowing, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies, distributions received from equity method investees and beneficial interests in securitization transactions. The new standard also clarifies that an entity should determine each separately identifiable source or use within the cash receipts and cash payments on the basis of the nature of the underlying cash flows. In situations in which cash receipts and payments have aspects of more than one class of cash flows and cannot be separated by source or use, the appropriate classification should depend on the activity that is likely to be the predominant source or use of cash flows for the item. The new standard will be effective for the Company on January 1, 2018. The Company is currently evaluating the impact that the adoption of this standard will have on its statements of cash flows.

In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230) - Restricted Cash (“ASU 2016-18”). ASU 2016-18 requires a statement of cash flows to explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of- period total amounts shown on the statement of cash flows. The effective date will be the first quarter of fiscal year 2018. The Company is currently assessing the impact that adopting this new accounting guidance will have on its financial statements and footnote disclosures.

In May 2017, the FASB issued ASU 2017-09, Compensation – Stock Compensation (Topic 719): Scope of Modification Accounting. The new standard provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. The new standard will be effective for the Company on January 1, 2018. The adoption of this standard is not expected to have a material impact on the Company’s financial position or results of operations.

Build-to-suit Lease

The Company is not the legal owner of the leased space. However, in accordance with ASC 840, Leases, the Company is deemed to be the owner of the leased space during the construction period because of the Company’s involvement with the build-out of the space. As a result, the Company has capitalized approximately $16.1 million as construction-in-progress within property, plant and equipment equal to the estimated fair value of its leased portion of the premises. Also, the Company has recognized a corresponding build-to-suit facility lease financing obligation with a current portion of $0.9 million classified as other liabilities and $15.3 million classified as other non-current liabilities on its balance sheet as of December 31, 2017. The Company’s expected costs to complete construction is estimated to be $0.7 million as of December 31, 2017. The construction is expected to be completed in the second quarter of 2018, upon which time the Company will assess and determine if the assets and corresponding liability should be de-recognized.