Summary of Significant Accounting Policies | 2. Summary of Significant Accounting Policies Basis of Presentation and Use of Estimates The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP). The preparation of the accompanying consolidated financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities as of the date of the consolidated financial statements, and the reported amounts of revenue and expenses during the reporting periods. Actual results could differ from those estimates. Liquidity and Substantial Doubt in Going Concern As of December 31, 2016, the Company has an accumulated deficit of $196.8 million as well as negative cash flows from operating activities. Presently, the Company does not have sufficient cash resources to meet its plans in the next twelve months from issuance of these financial statements. The Company will continue to require substantial funds to continue research and development, including clinical trials of its product candidate. Management’s plans in order to meet its operating cash flow requirements include financing activities such as private placements of its common stock, preferred stock offerings, issuances of debt and convertible debt instruments and collaborative or other arrangements with corporate sources. These factors raise substantial doubt regarding the Company’s ability to continue as a going concern for a period of one year from the issuance of the statement. There are no assurances that such additional funding will be achieved and that the Company will succeed in its future operations. The Company’s inability to obtain required funding in the near future or its inability to obtain funding on favorable terms will have a material adverse effect on its operations and strategic development plan for future growth. If the Company cannot successfully raise additional capital and implement its strategic development plan, its liquidity, financial condition and business prospects will be materially and adversely affected, and the Company may have to cease operations. In accordance with ASU No. 2014-15 Presentation of Financial Statements – Going Concern (Subtopic 205-40), the Company’s management evaluates whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the financial statements are issued. The Company has incurred significant operating losses and had an accumulated deficit of $196.8 million as of December 31, 2016. The Company has financed its operations primarily through the sale of equity securities, debt financing and payments received under its former licensing and collaboration agreements with pharmaceutical companies. To date, none of the Company’s product candidates have been approved by the Food and Drug Administration for sale. The Company will continue to require additional financing to develop its product candidates and fund operating losses. Management intends to seek capital to support company initiatives through equity or debt financing, collaboration or other arrangements with corporate partners, and/or other sources of financing. However, if such financing is not available at adequate levels or on acceptable terms, the Company could be required to significantly reduce its operating expenses and delay, reduce the scope of, or eliminate some of its development programs, out-license Consolidation The consolidated financial statements include the accounts of Zosano Pharma Corporation and Opco. Intercompany balances and transactions have been eliminated in consolidation. Segment Reporting The Company operates in one reportable segment to develop human pharmaceutical products. Management uses one measurement of profitability and does not segregate its business for internal reporting. All long-lived assets are maintained in the United States. Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Investments in Marketable Securities The Company classifies its investments in marketable securities as available-for-sale. available-for-sale Restricted Cash The Company entered into a pledge and security agreement with a bank whereby $35,000 was held as a security for corporate purchasing cards. The balance is classified as restricted cash as of December 31, 2016 and 2015, respectively. Concentrations of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash, cash equivalents and short-term investments. The Company invests its excess cash in money market funds, U.S. government agency bonds, corporate notes, certificates of deposit and commercial paper. The Company’s investment policy limits investments to certain types of debt securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. Other than for obligations of the U.S. government, the Company’s policy is that no more than 5% of its investments may be concentrated in a single issuer. Bank deposits are held by a single financial institution having a strong credit rating and these deposits may at times be in excess of FDIC insured limits. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents and short-term investments and issuers of investments to the extent recorded on the balance sheets. Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method over the estimated useful lives of the respective assets, which range from three to five years for computer equipment and software, and nine years for manufacturing, laboratory, and office equipment. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful lives of the respective assets. Impairment of Long-Lived Assets The Company identifies and records impairment losses on long-lived assets used in operations when events and changes in circumstances indicate that the carrying amount of an asset likely is not recoverable. Recoverability is measured by comparing the anticipated undiscounted future net cash flows to the related asset’s carrying value. If an asset is considered impaired, the asset is written down to fair value, which is determined based either on discounted cash flows or appraised value, depending on the nature of the asset. No impairment charge was recorded for the years ended December 31, 2016 and 2015. Long-Term Investment In October 2013, the Company entered into a stock purchase agreement with Zosano, Inc. (the Shell Corporation), a Delaware corporation, pursuant to which the Company acquired 10,016,973 shares of the Shell Corporation’s common stock, $0.0001 par value, for an aggregate cash purchase price of $0.4 million. Immediately following the closing of the acquisition, 10,027,000 shares of the Shell Corporation’s common stock were issued and outstanding, approximately 99.9% of which were held by the Company. The Company accounted for its investment in the Shell Corporation using the cost method of accounting and classified it as other long-term assets in its consolidated balance sheet. In November 2016, the Company sold its interest in Zosano, Inc. for an aggregate cash selling price of $225,000 and recorded a realized loss of approximately $57,000 in its consolidated income statement under the caption Other expense, net. Debt Issuance Costs Deferred issuance costs related to the Company’s debt are presented as a direct deduction from the carrying amount of the debt liability, consistent with debt discounts. Deferred Rent Rent expense is recognized on a straight-line basis over the non-cancelable non-cancelable Promissory Notes The Company accounts for its unsecured and secured promissory notes issued to certain related and non- Revenue Recognition The Company recognizes revenue when all four of the following criteria have been met: (i) persuasive evidence of an arrangement exists, (ii) delivery has occurred or services have been rendered, (iii) the fee is fixed or determinable, and (iv) collectability is reasonably assured. Revenue under collaboration and license arrangements is recognized based on the performance requirements of the contract. Research and Development Expenses Research and development costs are charged to expense as incurred and consist of costs related to (i) servicing the Company’s collaborative development efforts with other pharmaceutical companies, (ii) furthering the Company’s research and development efforts, and (iii) designing and manufacturing the Company’s intracutaneous applicator for the Company’s clinical and nonclinical studies. Research and development costs include salaries and related employee benefits, costs associated with clinical trials, nonclinical research and development activities, regulatory activities, costs of active pharmaceutical ingredients and raw materials, research and development related overhead expenses, fees paid to contract research organizations that conduct clinical trials on behalf of the Company, and fees paid to contract manufacturing organizations that conduct manufacturing activities on behalf of the Company. For the year ended December 31, 2016, the Company incurred research and development costs of approximately $11.9 million in connection with the Company’s research and development efforts and approximately $8.6 million in the manufacturing of the Company’s intracutaneous delivery system for development of the Company’s product candidate. For the year ended December 31, 2015, the Company incurred research and development costs of $0.1 million in support of the Company’s collaborative development services to Novo Nordisk A/S (Novo Nordisk), $9.3 million in connection with the Company’s research and development efforts, and $10.9 million in the manufacturing of the Company’s intracutaneous delivery system for the development of the Company’s product candidates. Clinical Trial Costs Clinical trial costs are a component of research and development expenses. The Company expenses clinical trial activities performed by third parties based upon actual work completed in accordance with agreements established with clinical research organizations and clinical sites. The Company accrues clinical trial expenses each reporting period. The Company determines the actual costs through discussions with internal personnel and external service providers as to the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services. Stock-Based Compensation The Company accounts for its stock-based compensation, generally recorded as an expense, based on the fair value of the stock- based awards that are ultimately expected to vest. The fair value of employee stock option grants is estimated on the date of grant using the Black-Scholes option pricing model, and are recognized as expense on a straight- line basis over the employee’s requisite service period (generally the vesting period), net of estimated forfeitures. The Company records the expense attributed to non-employee non-employees re-measurement Income Taxes The Company uses the liability method to account for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between the financial statement carrying amounts of existing assets and liabilities and their tax bases. Deferred tax assets and liabilities are measured using enacted tax rates applied to taxable income in the years in which those temporary differences are expected to be recovered or settled. A valuation allowance is established when necessary to reduce deferred tax assets to the amount expected to be realized. Financial statement effects of uncertain tax positions are recognized when it is more-likely-than-not, Comprehensive Loss Comprehensive loss is comprised of net loss and other comprehensive loss. The only component of the Company’s other comprehensive loss is the unrealized losses on the Company’s marketable securities at December 31, 2015. Net Loss Per Common Share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per common share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares and potentially dilutive securities outstanding for the period determined using the treasury-stock and if-converted The following outstanding common stock equivalents were excluded from the computations of diluted net loss per common share for the periods presented as the effect of including such securities would be antidilutive: December 31, 2016 2015 (in shares) Warrants to purchase common stock 9,672,379 72,379 Options to purchase common stock 1,846,058 (1) 972,951 11,518,437 1,045,330 (1) Total does not include 670,000 conditional stock options granted to certain executives since these grants are subject to approval by the Corporation’s shareholders of an amendment of the 2014 Plan. Recently Issued Accounting Standards In November 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016-18, Statement of Cash Flows In March 2016, the FASB issued Accounting Standards Update (ASU) 2016-09, Improvements to Employee Share-Based Payment Accounting In February 2016, the FASB issued Accounting Standards Update (ASU) 2016-02, Leases right-of-use In January 2016, the FASB issued ASU 2016-01, Financial Instruments – Overall: Recognition and Measurement of Financial Assets and Financial Liabilities In May 2014, the Financial Accounting Standards Board, or FASB, issued Auditing Standard Updated (ASU), No. 2014-09, Revenue from Contracts with Customers |