Summary of Significant Accounting Policies

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) and applicable rules and regulations of the SEC regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by GAAP have been condensed or omitted, and accordingly the consolidated balance sheet as of December 31, 2016 has been derived from the audited consolidated financial statements at that date but does not include all of the information required by GAAP for complete consolidated financial statements. These unaudited interim condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair statement of the Company’s consolidated financial information. The results of operations for the three and nine months ended September 30, 2017 are not necessarily indicative of the results to be expected for the year ending December 31, 2017 or for any other interim period or for any other future year.

The accompanying interim unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2016 included in the Company’s Annual Report on Form 10-K, filed with the SEC on March 7, 2017.

Principles of Consolidation

The accompanying unaudited interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary. All intercompany transactions and balances have been eliminated upon consolidation.

Use of Estimates

The preparation of the condensed consolidated financial statements in conformity with GAAP requires management to make estimates, assumptions and judgments that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. On an ongoing basis, management evaluates its estimates related to revenue recognition, accruals for research and development activities, stock-based compensation, and income taxes. Estimates related to revenue recognition include actual costs incurred versus total estimated budgeted cost of the Company's deliverables, actual costs incurred versus total estimated budgeted cost of variable consideration, and application of constraint in the determination of transaction price under its license and collaboration agreement with Janssen Biotech, Inc. (the "Janssen License and Collaboration Agreement"). Management bases these estimates on historical and anticipated results, trends, and various other assumptions that the Company believes are reasonable under the circumstances, including assumptions as to forecasted amounts and future events. Actual results may differ significantly from those estimates.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash, cash equivalents and available-for-sale securities. Substantially all of the Company’s cash is held by two financial institutions that management believes are of high credit quality. Such deposits may, at times, exceed federally insured limits. The primary focus of the Company’s investment strategy is to preserve capital and to meet liquidity requirements. The Company’s cash equivalents and available-for-sale securities are managed by external managers within the guidelines of the Company’s investment policy. The Company’s investment policy addresses the level of credit exposure by limiting concentration in any one corporate issuer and establishing a minimum allowable credit rating. To manage its credit risk exposure, the Company maintains its portfolio of cash equivalents and available-for-sale securities in fixed income securities denominated and payable in U.S. dollars. Permissible investments of fixed income securities include obligations of the U.S. government and its agencies, money market instruments including commercial paper and negotiable certificates of deposit, and highly rated corporate debt obligations and money market funds. The Company has not experienced any material credit losses on its investments.

Cash Equivalents

Cash equivalents that are readily convertible to cash are stated at cost, which approximates fair value. The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents.

Restricted Cash

Restricted cash consists of cash balances primarily held as security in connection with the Company’s corporate credit card and a letter of credit related to the Company's facility lease entered into in March 2017.

Cash as Reported in Consolidated Statements of Cash Flows

Cash as reported in the unaudited condensed consolidated statements of cash flows includes the aggregate amounts of cash and cash equivalents and the restricted cash as presented on the consolidated balance sheets.

Cash as reported in the unaudited condensed consolidated statements of cash flows consists of (in thousands):



	September 30,
	2017		2016
Cash and cash equivalents	$	50,395	$	96,024
Restricted cash - current	10		10
Restricted cash - noncurrent	450		—
Cash balance in condensed consolidated statements of cash flows	$	50,855	$	96,034

Available-for-Sale Securities

All marketable securities have been classified as “available-for-sale” and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. Management determines the appropriate classification of its marketable securities at the time of purchase and reevaluates such designation as of each balance sheet date. Short-term marketable securities have maturities greater than three months but no longer than 365 days as of the balance sheet date. Long-term marketable securities have maturities of 365 days or longer as of the balance sheet date. Unrealized gains and losses are excluded from earnings and are reported as a component of comprehensive loss. Realized gains and losses and declines in fair value judged to be other than temporary, if any, on available-for-sale securities are included in interest income. The cost of securities sold is based on the specific-identification method. Interest on marketable securities is included in interest income.

Fair Value of Financial Instruments

Fair value accounting is applied to all financial assets and liabilities that are recognized or disclosed at fair value in the condensed consolidated financial statements on a recurring basis (at least annually). The carrying amount of the Company’s financial instruments, including cash equivalents, receivable from collaboration partner, accounts payable and accrued expenses and other payables approximates fair value due to their short-term maturities. See Note 4, Fair Value Measurements, regarding the fair value of the Company’s other financial assets and liabilities.

Revenue Recognition

Effective July 1, 2017, the Company adopted Accounting Standards Codification Topic 606, Revenue from Contracts with Customers ("ASC 606") using the full retrospective transition method. The Company did not have any effective contracts within the scope of this guidance prior to July 1, 2017. Accordingly, the Company did not elect to use any of the practical expedients permitted related to adoption, and the adoption of ASC 606 had no impact on the Company's financial position, results of operations or liquidity. This standard applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. Under ASC 606, 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 when (or as) the performance obligation is satisfied.

The Company entered into a license and collaboration agreement that became effective upon the resolution of regulatory requirements during the third quarter of 2017 which is within the scope of ASC 606, under which it has licensed certain rights to its PTG-200 product candidate to a third party and may enter into other such arrangements in the future. The terms of the arrangement include payment to the Company of one or more of the following: non-refundable, up-front license fees, development and regulatory and commercial milestone payments, and royalties on net sales of licensed products.

Licenses 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, up-front 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, 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 and, if over time, the appropriate method of measuring proportional performance for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of proportional performance each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition.

Milestone payments: At the inception of each arrangement that includes development, regulatory or commercial 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. Whichever method is used, it should be consistently applied throughout the life of the contract; however, it is not necessary for the Company to use the same approach for all contracts. The Company expects to use the most likely amount method for development and regulatory milestone payments. If it is probable that a significant 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 revenues and earnings in the period of adjustment. To date, the Company has not recognized any milestone payments resulting from its collaboration arrangement.

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). To date, the Company has not recognized any royalty revenue resulting from its collaboration arrangement.

Up-front 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.

Research and Development Costs

Research and development costs are expensed as incurred, unless there is an alternate future use in other research and development projects or otherwise. Research and development costs include salaries and benefits, stock-based compensation expense, laboratory supplies and facility-related overhead, outside contracted services including clinical trial costs, manufacturing and process development costs for both clinical and preclinical materials, research costs, development milestone payments under license and collaboration agreements, and other consulting services.

The Company accrues for estimated costs of research and development activities conducted by third-party service providers, which include the conduct of pre-clinical studies and clinical trials, and contract manufacturing activities. The Company records the estimated costs of research and development activities based upon the estimated services provided but not yet invoiced, and includes these costs in accrued expenses and other payables in the condensed consolidated balance sheets and within research and development expense in the condensed consolidated statements of operations. These costs are a significant component of the Company’s research and development expenses. The Company accrues for these costs based on factors such as estimates of the work completed and in accordance with agreements established with its third-party service providers. The Company makes significant judgments and estimates in determining the accrued liabilities at each balance sheet date. As actual costs become known, the Company adjusts its accrued liabilities. The Company has not experienced any material differences between accrued liabilities and actual costs incurred. However, the status and timing of actual services performed, number of patients enrolled, and the rate of patient enrollment may vary from the Company’s estimates, resulting in adjustments to expense in future periods. Changes in these estimates that result in material changes to the Company’s accruals could materially affect the Company’s results of operations.

Research and Development Tax Incentive

The Company is eligible under the AusIndustry research and development tax incentive program to obtain a cash amount from the Australian Taxation Office. The tax incentive is available to the Company on the basis of specific criteria with which the Company must comply. Specifically, the Company must have annual turnover of less than AUD 20.0 million and cannot be controlled by income tax exempt entities. The research and development tax incentive is recognized as a reduction to research and development expense when the right to receive has been attained and funds are considered to be collectible. The tax incentive is denominated in Australian dollars and, therefore, the related receivable is remeasured into U.S. dollars as of each reporting date.

Under certain conditions, research and development activities conducted outside Australia (“overseas finding”) also qualify for the research and development tax incentive. Funds received for overseas finding are at a risk of clawback until substantiation that less than 50% of research and development expenditures for a project will be incurred overseas. A deferred tax incentive is recorded upon the cash receipt of the overseas finding funds and a reduction of research and development expense is not recognized until the Company can substantiate that more than 50% of the total project expenditure will occur in Australia.

When there is reasonable assurance that the grant will be received with remote risk of clawback, the relevant expenditure has been incurred, and the consideration can be reliably measured, the Company records the research and development incentive, including the overseas finding funds, as research and development tax incentive receivable and a reduction of research and development expenses to reflect that the funds are owed to the Company for the period the eligible costs are incurred.

Net Loss per Share Attributable to Common Stockholders

Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding during the period, without consideration of potentially dilutive securities. The net loss attributable to common stockholders is calculated by adjusting the net loss of the Company for the accretion on the redeemable convertible preferred stock, if applicable. Diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders for all periods presented since the effect of potentially dilutive securities are anti-dilutive given the net loss of the Company.

Recently Adopted Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2014-09, which amends the guidance for accounting for revenue from contracts with customers. This ASU supersedes the revenue recognition requirements in ASC Topic 605, Revenue Recognition, and creates a new ASC Topic 606, Revenue from Contracts with Customers. Customers. Subsequent to May 2014, the FASB issued additional guidance that delayed the effective date and clarified various aspects of the new guidance, including principal versus agent considerations, identifying performance obligations and licensing, and also included other improvements and practical expedients. The Company adopted this new guidance effective July 1, 2017 using the full retrospective transition method. The Company did not have any effective contracts within the scope of this guidance prior to July 1, 2017. Accordingly, the Company did not elect to use any of the practical expedients permitted under the transition guidance, and the adoption had no impact on the Company's previously reported financial position, results of operations or liquidity.

In November 2015, the FASB issued ASU No. 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes, which is intended to simplify and improve how deferred income taxes are classified on the balance sheet. This guidance eliminates the current requirement to present deferred tax assets and liabilities as current and noncurrent in a classified balance sheet and now requires entities to classify all deferred tax assets and liabilities as noncurrent. The guidance is effective for annual periods beginning after December 15, 2016 and for interim periods within those annual periods, and early adoption is permitted. The Company adopted this guidance effective January 1, 2017. The adoption of this guidance did not have a material impact on the Company's financial position, results of operations or liquidity.

In March 2016, the FASB issued ASU No. 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting, which is intended to simplify several aspects of accounting for employee share-based payment transactions, including income tax consequences, the determination of forfeiture rates, classification of awards as either equity or liabilities, and classification on the statement of cash flows. This guidance is effective for fiscal years and interim periods within those years beginning after December 15, 2016, and early adoption is permitted. The Company adopted this guidance effective January 1, 2017 and has elected to recognize forfeitures of share-based payment awards as they occur on a prospective basis. The impact of the adoption of ASU 2016-09 was not material to the Company’s condensed consolidated financial statements. The adoption of this guidance did not have a material impact on the income tax effects of share-based payment awards as the resulting change in the Company's deferred income tax assets is fully offset by a corresponding deferred income tax asset valuation allowance.

In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash, which requires the presentation of changes in restricted cash or restricted cash equivalents on the statement of cash flows. This guidance is effective for the fiscal years and interim periods within those years beginning after December 15, 2017, with early adoption permitted. The Company early adopted this guidance effective March 31, 2017, and, accordingly, amounts generally described as restricted cash are included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts of cash reflected on the accompanying consolidated statements of cash flows. The Company has adopted ASU 2016-18 retrospectively and has revised the prior period cash flows from investing activities, beginning cash balance, and ending cash balance to reflect the change in presentation of restricted cash. Other than the change in presentation in the accompanying consolidated statements of cash flows, the adoption of this guidance had no effect on the Company’s financial position, results of operations or liquidity.

Recently Issued Accounting Pronouncements Not Adopted as of September 30, 2017

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). Under the new guidance, (with the exception of short-term leases) at the commencement date, lessees will be required to recognize a lease liability and a right-of-use asset. Lessor accounting is largely unchanged, while lessees will no longer be provided with a source of off-balance sheet financing. This guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. Lessees (for capital and operating leases) are required to apply the modified retrospective transition method for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The modified retrospective method does not require any transition accounting for leases that did not exist before the earliest comparative period presented. While the Company continues to evaluate the impact of this guidance on its consolidated financial statements and disclosures, it expects that its non-cancellable operating lease commitments will be subject to the new guidance and recognized as right-of-use assets and operating lease liabilities on the Company’s consolidated balance sheets, and that the adoption of this new guidance will not have a material impact on its results of operations or liquidity.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326), which is intended to provide financial statement users with more useful information about expected credit losses on financial assets held by a reporting entity at each reporting date. The new standard replaces the existing incurred loss impairment methodology with a methodology that requires consideration of a broader range of reasonable and supportable forward-looking information to estimate all expected credit losses. This guidance is effective for fiscal years and interim periods within those years beginning after December 15, 2019 and early adoption is permitted for fiscal years and interim periods within those years beginning after December 15, 2018. The Company is currently evaluating the impact of this new guidance on its consolidated financial statements and disclosures.

In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments, which clarifies the classification of certain cash receipts and cash payments in the statements of cash flow to eliminate the diversity in practice related to eight specific cash flow issues. This guidance is effective for fiscal years and interim periods within those years beginning after December 15, 2017, and early adoption is permitted. The Company is currently evaluating the impact of this new guidance on its consolidated financial statements and disclosures.

In May 2017, the FASB issued ASU No. 2017-09, Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting, which provides guidance on the types of changes to the terms and conditions of share-based payment awards to which an entity would be required to apply modification accounting. Specifically, an entity would not apply modification accounting if the fair value, vesting conditions and classification of the awards are the same immediately before and after the modification. This guidance is effective for fiscal years and interim periods within those years beginning after December 15, 2017, and early adoption is permitted. The Company is currently evaluating the impact of this new guidance on its consolidated financial statements and disclosures.