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Nature of Operations [Text Block]

Organization and Operations

The Company

Proteon Therapeutics, Inc. (the “Company”) is a late-stage biopharmaceutical company focused on the development of novel, first-in-class pharmaceuticals to address the medical needs of patients with kidney and vascular disease. The Company was formed in June 2001 and incorporated on March 24, 2006. During 2013, the Company formed a wholly-owned subsidiary, organized in the United Kingdom, Proteon Therapeutics Limited. As of September 30, 2015, there has been no activity in this subsidiary other than its formation. During 2014, the Company formed a wholly-owned Massachusetts Securities Corporation subsidiary as a holding company for its available-for-sale investments, Proteon Securities Corp. The Company completed its initial public offering of its common stock, $0.001 par value per share (“Common Stock”) on October 27, 2014 (the “IPO”). Since inception, the Company has been primarily involved in research and development activities.

The Company devotes substantially all of its efforts to product research and development, initial market development and raising capital. The Company has not generated any product revenue related to its primary business purpose to date and is subject to a number of risks similar to those of other development stage companies, including dependence on key individuals, competition from other companies, the need for development of commercially viable products and the need to obtain adequate additional financing to fund the development of its product candidates. The Company is also subject to a number of risks similar to other companies in the biotechnology industry, including regulatory approval of products, uncertainty of market acceptance of products, competition from substitute products and larger companies, the need to obtain additional financing, compliance with government regulations, protection of proprietary technology, dependence on third parties, product liability and dependence on key individuals.

As of September 30, 2015, the Company had cash, cash equivalents and available-for-sale investments of $70.5 million. The Company believes that its existing cash, cash equivalents and available-for-sale investments will be sufficient to fund operations and capital expenditures into the fourth quarter of 2017. The Company had an accumulated deficit of $124.9 million as of September 30, 2015.

Note 2 - Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2015

Significant Accounting Policies [Text Block]

Summary of Significant Accounting Policies

Initial Public Offering

On October 27, 2014, the Company completed the IPO of its Common Stock, pursuant to a registration statement on Form S-1, as amended. An aggregate of 7,026,500 shares of Common Stock registered under the registration statement were sold at a price of $10.00 per share (including 916,500 shares of Common Stock sold by the Company pursuant to the full exercise of an overallotment option granted to the Company’s underwriters in connection with the IPO). Net proceeds of the IPO were $62.5 million, after deducting underwriting discounts, commissions and offering-related expenses payable by the Company of approximately $7.8 million. In this transaction, all shares of the Company’s redeemable convertible preferred stock (the “Preferred Stock”) were automatically converted into an aggregate of 8,651,805 shares of its Common Stock and the Series D redeemable convertible preferred stock (the “Series D Preferred Stock”) investors’ rights and obligations were either exercised or extinguished.

Reverse Stock Split

On October 1, 2014, the Board of Directors, and on October 3, 2014, the stockholders, approved a 1-for-15.87 reverse stock split of the Company’s Common Stock, resulting in a proportional adjustment to the existing conversion ratios for each series of Preferred Stock. The effective date of the reverse stock split was October 6, 2014. All share, share equivalent and per share amounts have been adjusted to reflect the reverse stock split. The ratios by which shares of Preferred Stock are convertible into shares of Common Stock were also adjusted to reflect the effects of the reverse stock split.

Basis of Presentation and Principles of Consolidation

The unaudited interim condensed consolidated financial statements of the Company included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2014 and notes thereto included in the Company’s Annual Report on Form 10-K, as filed with the SEC on March 20, 2015.

The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited financial statements. In the opinion of the Company’s management, the accompanying unaudited interim condensed consolidated financial statements contain all adjustments which are necessary to fairly present the Company’s financial position as of September 30, 2015, the results of its operations for the three and nine months ended September 30, 2015 and 2014 and its cash flows for the nine months ended September 30, 2015 and 2014. Such adjustments are of a normal and recurring nature. The results for the three and nine months ended September 30, 2015 are not necessarily indicative of the results for the year ending December 31, 2015, or for any future period.

The unaudited interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Proteon Therapeutics Limited and Proteon Securities Corp. All intercompany balances and transactions have been eliminated in consolidation. These condensed consolidated financial statements have been prepared in conformity with GAAP. Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”).

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, estimates related to convertible notes, stock-based compensation expense, clinical trial accruals and reported amounts of revenues and expenses during the reported period. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.

The Company historically utilized significant estimates and assumptions in determining the fair value of its Common Stock. The Company utilized various valuation methodologies in accordance with the framework of the 2004 and 2013 American Institute of Certified Public Accountants Technical Practice Aids,

Valuation of Privately-Held Company Equity Securities Issued as Compensation

, to estimate the fair value of its Common Stock prior to its IPO. Each valuation methodology included estimates and assumptions that required the Company’s judgment.

These estimates and assumptions included a number of objective and subjective factors, including external market conditions affecting the biotechnology industry sector, the prices at which the Company sold shares of Preferred Stock, the superior rights and preferences of securities senior to the Company’s Common Stock at the time and the likelihood of achieving a liquidity event, such as an initial public offering or a sale of the Company. Significant changes to the key assumptions used in the valuations could have resulted in different fair values of Common Stock at each valuation date and materially affected the financial statements.

Fair Value of Financial Instruments

The Company’s financial instruments consist of cash and cash equivalents, available-for-sale investments, forward foreign currency contracts (see Note 4), accounts payable, accrued liabilities, convertible promissory notes (“Convertible Notes”) and features embedded in the Convertible Notes. The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. FASB ASC Topic 820,

Fair Value Measurement and Disclosures

, established a hierarchy of inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the financial instrument based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the financial instrument and are developed based on the best information available under the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported or disclosed fair value of the financial instruments and is not a measure of the investment credit quality. Fair value measurements are classified and disclosed in one of the following three categories:

Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly.

Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable.

To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

Financial instruments measured at fair value on a recurring basis include cash equivalents, short-term investments and forward foreign currency contracts (see Note 4). There have been no changes to the valuation methods utilized by the Company during the nine months ended September 30, 2015 and 2014. The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of financial instruments between levels during the three and nine months ended September 30, 2015 and 2014.

Derivative Financial Instruments

The Company enters into forward foreign currency contracts to mitigate its exposure to fluctuations in the exchange rates between the Swiss Franc and the U.S. dollar (see Note 4). The Company records these derivative financial instruments on the consolidated balance sheet at fair value. Although these derivative contracts are intended to economically hedge foreign exchange risk, the Company has not elected to apply hedge accounting. As such, changes in the fair value of these instruments are recorded directly in earnings as a component of other income (expense), as they occur. The Company executes its derivative instruments with financial institutions that the Company judges to be credit-worthy, defined as institutions that hold an investment-grade credit rating.

Recent Accounting Pronouncements

In May 2014, the FASB issued a new standard on revenue recognition providing a single, comprehensive revenue recognition model for all contracts with customers. The new revenue standard is based on the principle that revenue should be recognized to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new standard is effective beginning January 1, 2017, with no early adoption permitted. The amendments may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of initial application. The Company is currently evaluating the impact of the new guidance on its condensed consolidated financial statements, if any.

In August 2014, the FASB issued authoritative guidance on determining when and how reporting entities must disclose going-concern uncertainties in their financial statements, including requiring management to perform interim and annual assessments of an entity’s ability to continue as a going concern within one year of the date of issuance of the entity’s financial statements and providing certain disclosures if there is substantial doubt about the entity’s ability to continue as a going concern. This guidance will be effective for the Company’s fiscal year 2016 and for interim periods beginning in the first quarter of fiscal 2017. The Company is still evaluating the impact of this guidance on its financial statement disclosures.

There have been no other material changes to the significant accounting policies previously disclosed in the Company’s Annual Report on Form 10-K, as filed with the SEC on March 20, 2015.

Note 3 - Fair Value Measurements

9 Months Ended

Sep. 30, 2015

Fair Value Disclosures [Text Block]

Fair Value Measurements

Below is a summary of assets and liabilities measured at fair value (in thousands):

	As of September 30, 2015
	Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets
Cash equivalents	$	35,643	$	-	$	-	$	35,643
Government securities		34,565		-		-		34,565
Total	$	70,208	$	-	$	-	$	70,208

Liabilities
Foreign currency forward contracts	$	-	$	426	$	-	$	426
Total	$	-	$	426	$	-	$	426

	As of December 31, 2014
	Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets
Cash equivalents	$	68,830	$	-	$	-	$	68,830
Government securities		6,508		-		-		6,508
Corporate bonds		-		8,247		-		8,247
Total	$	75,338	$	8,247	$	-	$	83,585

As of September 30, 2015 and December 31, 2014, the Company’s cash equivalents consist principally of money market funds and government debt securities with original maturities of 90 days or less. Government securities consist principally of government debt securities and money market funds which are classified as available-for-sale. Corporate bonds consist of bonds issued by highly-rated corporate entities which are classified as available-for-sale. Forward foreign currency contracts consist of contracts with credit-worthy financial institutions to buy Swiss Francs with U.S. dollars in the future at agreed upon exchange rates.

Forward foreign currency contracts are stated at fair value and consist of Level 2 financial instruments in the fair value hierarchy. The Company determines the fair value of its forward foreign currency contracts based on pricing from a service provider. The service provider values the instruments based on market prices from a variety of industry-standard independent data providers. Such market prices are based on inputs other than quoted prices included within Level 1 that are observable for the asset, either directly or indirectly (Level 2 inputs). Cash equivalents and government securities are stated at fair value and consist of Level 1 financial instruments in the fair value hierarchy

The Company determined the fair value of its debt security holdings and corporate bonds based on pricing from a service provider. The service provider values the securities based on market prices from a variety of industry-standard independent data providers. These market prices are quoted prices in active markets for identical assets (Level 1 inputs). Corporate bonds are stated at fair value and consist of Level 2 financial instruments in the fair value hierarchy. The Company determines the fair value of its corporate bonds holdings based on pricing from a service provider. The service provider values the securities based on market prices from a variety of industry-standard independent data providers. Such market prices are based on inputs other than quoted prices included within Level 1 that are observable for the asset, either directly or indirectly (Level 2 inputs).

Available-for-sale securities at September 30, 2015 and December 31, 2014 consist of the following (in thousands):

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
September 30, 2015
Government securities
(Due within 1 year)	$	34,559	$	6	$	-		$	34,565
	$	34,559	$	6	$	-		$	34,565

December 31, 2014
Government securities
(Due within 1 year)	$	6,510	$	-	$	(2	)	$	6,508
Corporate bonds
(Due within 1 year)		8,251		-		(4	)		8,247
	$	14,761	$	-	$	(6	)	$	14,755

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

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Note 4 - Derivative Financial Instruments

9 Months Ended

Sep. 30, 2015

Derivative Instruments and Hedging Activities Disclosure [Text Block]

Derivative Financial Instruments

The Company enters into forward foreign currency contracts to mitigate its exposure to fluctuations in the U.S dollar value of forecasted transactions denominated in Swiss Franc. During the quarter ended September 30, 2015, the Company had forward foreign currency contract activity for which it did not elect hedge accounting for the forward foreign currency contracts outstanding as of September 30, 2015, but may elect to apply hedge accounting in the future. As a result, during the quarter ended September 30, 2015, the Company experienced unrealized losses within other expense in the consolidated statement of operations from the mark-to-market of outstanding forward foreign currency contracts. The Company expects potential volatility within other income (expense) in future periods for contracts for which the Company does not apply hedge accounting.

As of September 30, 2015, the Company had the following outstanding forward foreign currency contracts that were not designated for hedge accounting and that were used to reduce the exposure to fluctuations in the U.S dollar value of forecasted transactions denominated in Swiss Franc (dollars in thousands):

Notional Amount		Effective Date		Maturity Date		Number of Instruments
$6,646		June 12, 2015		Various dates through December 15, 2016		5

No forward foreign currency contracts were held by the Company prior to May 2015. The following table below presents the fair value of the Company’s derivative financial instruments as well as their classification on the balance sheet as of September 30, 2015 (in thousands):

	Balance Sheet line item	Gross amounts of recognized liabilities		Gross amount offset in consolidated balance sheet		Net Amount

Forward foreign currency contracts	Other current liabilities	$	342	$	-	$	342
Forward foreign currency contracts	Other noncurrent liabilities		84		-		84
Total		$	426	$	-	$	426

The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.

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Note 5 - Commitments and Contingencies

9 Months Ended

Sep. 30, 2015

Commitments and Contingencies Disclosure [Text Block]

Commitments and Contingencies

Significant Contracts and Agreements

In February 2002, the Company entered into an agreement to license certain intellectual property with Johns Hopkins University. The agreement calls for payments to be made by the Company upon the commencement of product sales, in the form of a royalty of 2.5% on net sales of the product. As of September 30, 2015 the Company has not commenced product sales and therefore has recognized no royalties on product sales.

In July 2015, the Company entered into a manufacturing services agreement with Lonza LTD (“Lonza”) for the processing, development and manufacture of the active pharmaceutical ingredient (“API”) in its lead product candidate, vonapanitase. Under the agreement, the Company will execute purchase orders authorizing Lonza to manufacture the batches and will pay for the services and batches in accordance with terms and assumptions in the agreement and to be set forth in a project plan.

Operating Leases

Future minimum payments required under operating leases as of September 30, 2015 are summarized as follows (in thousands):

Year Ending December 31:	Amount

2015	$	42
2016		168
2017		168
2018		84
Total minimum lease payments	$	462

Rental expense for the nine months ended September 30, 2015 and 2014 was $139,000. In addition to the base rent, the Company is also responsible for its share of operating expenses and real estate taxes, in accordance with the terms of the lease agreement. As of September 30, 2015, the Company has provided a security deposit in the amount of $14,000 to the lessor.

Restricted cash related to facilities leases

At September 30, 2015 and December 31, 2014, the Company had $14,000 and $38,000, respectively, in an outstanding letter of credit to be used as collateral for leased premises. At September 30, 2015 and December 31, 2014, the Company pledged an aggregate of $14,000 and $39,000, respectively, to the bank as collateral for the letter of credit, which is included in long-term assets and both short-term deposits and long-term assets, respectively.

Note 6 - Common Stock

9 Months Ended

Sep. 30, 2015

Stockholders' Equity Note Disclosure [Text Block]

Common Stock

At September 30, 2015, the Company has 100,000,000 shares of Common Stock authorized for issuance, $0.001 par value per share, of which 16,479,508 shares were issued and outstanding. After the 5,864 shares issued in the second quarter for the ESPP plan, the Company has the following shares of Common Stock reserved for future issuance:

	September 30, 2015		December 31, 2014

Stock-based compensation awards		2,440,127		1,807,349
Employee Stock Purchase Plan		299,127		140,500
Total		2,739,254		1,947,849

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

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-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

+ Details

Note 7 - Stock-based Compensation

9 Months Ended

Sep. 30, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Text Block]

Stock-based Compensation

Stock Options

The following table summarizes stock option activity for employees and non-employees:

	Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (years)		Aggregate Intrinsic Value

Outstanding at December 31, 2014		1,235,526		$	4.19		7.1	$	7,709
Granted		589,924		$	12.68
Exercised		(25,188	)
Outstanding at September 30, 2015		1,800,262		$	7.00		7.4	$	13,061
Exercisable at September 30, 2015		775,789		$	3.22		5.2	$	8,310
Vested or expected to vest at September 30, 2015 (1)		1,683,543		$	6.91		7.3	$	12,403

_________________

(1) Represents the number of vested options at September 30, 2015 plus the number of unvested options expected to vest based on the unvested options outstanding at September 30, 2015.

Employee Stock Purchase Plan

The 2014 ESPP initially authorized the issuance of up to 140,500 shares of Common Stock. The number of shares increases each January 1, commencing on January 1, 2015 and ending on (and including) January 1, 2024, by an amount equal to the lesser of one percent of the outstanding shares as of the end of the immediately preceding fiscal year, 281,000 shares and any lower amount determined by the Company’s Board of Directors prior to each such January 1st. As of September 30, 2015, as a result of an increase on January 1, 2015 of one percent of the outstanding shares as of the end of the fiscal year ending December 31, 2014, the 2014 ESPP authorized the issuance of up to 304,991 shares of Common Stock. The first offering under the 2014 ESPP began on January 1, 2015 and ended on June 30, 2015. The second offering under the 2014 ESPP began on July 1, 2015 and will end on December 31, 2015. During the nine months ended September 30, 2015, 5,864 shares were issued under the 2014 ESPP with 299,127 shares remaining for future issuance under the plan as of September 30, 2015. The Company incurred $5,000 and $27,000 in stock-based compensation expense related to the 2014 ESPP for the three and nine months ended September 30, 2015, respectively.

Note 8 - Income Taxes

9 Months Ended

Sep. 30, 2015

Income Tax Disclosure [Text Block]

Income Taxes

Deferred taxes are recognized for temporary differences between the basis of assets and liabilities for financial statement and income tax purposes. The Company has evaluated the positive and negative evidence bearing upon the Company’s ability to realize the benefit of its deferred tax assets. Based on the Company’s history of operating losses, the Company has concluded that it is more likely than not that the benefit of its deferred tax assets will not be realized. Due to the uncertainty surrounding the realization of the favorable tax attributes in future tax returns, the Company has provided a full valuation allowance against its deferred tax assets. There were no significant income tax provisions or benefits for the three or nine months ended September 30, 2015 and 2014.

Note 9 - Net Loss Per Share Attributable to Common Stockholders

9 Months Ended

Sep. 30, 2015

Earnings Per Share [Text Block]

Net Loss per Share Attributable to Common Stockholders

The Company computes basic and diluted loss per share using a methodology that gives effect to the impact of outstanding participating securities (the “two-class method”). As the three and nine month periods ended September 30, 2015 and 2014 resulted in net losses, there is no income allocation required under the two-class method or dilution attributed to weighted-average shares outstanding in the calculation of diluted loss per share.

The following Common Stock equivalents, presented on an as converted basis, were excluded from the calculation of net loss per share for the periods presented, due to their anti-dilutive effect (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
Convertible preferred stock		-		7,581		-		7,581
Common stock warrants		-		660		-		660
Outstanding stock options		1,800		1,134		1,800		1,134
Outstanding ESPP shares		1		-		1		-
		1,801		9,375		1,801		9,375

Note 10 - Subsequent Events

9 Months Ended

Sep. 30, 2015

Subsequent Events [Text Block]

10.

Subsequent Events

The Company has evaluated all activity that occurred subsequent to quarter end but prior to issuance of the condensed consolidated financial statements for events or transactions that could require disclosure or that could impact the carrying value of assets or liabilities as of the balance sheet date. The Company completed patient enrollment in the first of two Phase 3 trials for vonapanitase in radiocephalic AVFs in October 2015. In the judgment of management, there were no other material events that impacted the unaudited condensed financial statements or disclosures.

Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2015

Accounting Policies [Abstract]

Initial Public Offering, Policy [Policy Text Block

Initial Public Offering

Reverse Stock Split, Policy [Policy Text Block]

Reverse Stock Split

On October 1, 2014, the Board of Directors and on October 3, 2014, the stockholders approved a 1-for-15.87 reverse stock split of the Company’s Common Stock and resulting in a proportional adjustment to the existing conversion ratios for each series of Preferred Stock. The effective date of the reverse stock split was October 6, 2014. All share, share equivalent and per share amounts have been adjusted to reflect the reverse stock split. The ratios by which shares of Preferred Stock are convertible into shares of Common Stock were also adjusted to reflect the effects of the reverse stock split.

Basis of Accounting, Policy [Policy Text Block]

Basis of Presentation and Principles of Consolidation

The unaudited interim condensed consolidated financial statements of the Company included herein have been prepared, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2014 and notes thereto, included in the Company’s Annual Report on Form 10-K, as filed with the SEC on March 20, 2015.

The unaudited interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Proteon Therapeutics Limited and Proteon Securities Corp. All intercompany balances and transactions have been eliminated in consolidation. These condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”).

Use of Estimates, Policy [Policy Text Block]

Use of Estimates

Valuation of Privately-Held Company Equity Securities Issued as Compensation

, to estimate the fair value of its Common Stock prior to its IPO. Each valuation methodology included estimates and assumptions that required the Company’s judgment.

Fair Value Measurement, Policy [Policy Text Block]

Fair Value of Financial Instruments

The Company’s financial instruments consist of cash and cash equivalents, available-for-sale investments, forward foreign currency contracts (see Note 4), accounts payable, accrued liabilities, convertible promissory notes (“Convertible Notes”) and features embedded in the Convertible Notes (see Note 5). The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. FASB ASC Topic 820,

Fair Value Measurement and Disclosures

Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly.

Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable.

Derivatives, Policy [Policy Text Block]

Derivative Financial Instruments

New Accounting Pronouncements, Policy [Policy Text Block]

Recent Accounting Pronouncements

There have been no other material changes to the significant accounting policies previously disclosed in the Company’s Annual Report on Form 10-K, as filed with the SEC on March 20, 2015.

Note 3 - Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2015

Fair Value, Assets Measured on Recurring Basis [Table Text Block]

	As of September 30, 2015
	Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets
Cash equivalents	$	35,643	$	-	$	-	$	35,643
Government securities		34,565		-		-		34,565
Total	$	70,208	$	-	$	-	$	70,208

Liabilities
Foreign currency forward contracts	$	-	$	426	$	-	$	426
Total	$	-	$	426	$	-	$	426

	As of December 31, 2014
	Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets
Cash equivalents	$	68,830	$	-	$	-	$	68,830
Government securities		6,508		-		-		6,508
Corporate bonds		-		8,247		-		8,247
Total	$	75,338	$	8,247	$	-	$	83,585

Available-for-sale Securities [Table Text Block]

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
September 30, 2015
Government securities
(Due within 1 year)	$	34,559	$	6	$	-		$	34,565
	$	34,559	$	6	$	-		$	34,565

December 31, 2014
Government securities
(Due within 1 year)	$	6,510	$	-	$	(2	)	$	6,508
Corporate bonds
(Due within 1 year)		8,251		-		(4	)		8,247
	$	14,761	$	-	$	(6	)	$	14,755

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Note 4 - Derivative Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2015

Schedule of Derivative Instruments [Table Text Block]

Notional Amount		Effective Date		Maturity Date		Number of Instruments
$6,646		June 12, 2015		Various dates through December 15, 2016		5

Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]

	Balance Sheet line item	Gross amounts of recognized liabilities		Gross amount offset in consolidated balance sheet		Net Amount

Forward foreign currency contracts	Other current liabilities	$	342	$	-	$	342
Forward foreign currency contracts	Other noncurrent liabilities		84		-		84
Total		$	426	$	-	$	426

Tabular disclosure of pertinent information about a derivative or group of derivatives on a disaggregated basis, such as for individual instruments, or small groups of similar instruments. May include a combination of the type of instrument, risks being hedged, notional amount, hedge designation, related hedged item, inception date, maturity date, or other relevant item.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=56946850&loc=d3e41641-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624163-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 815
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5580258-113959

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 815
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Reference 10: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=56946850&loc=d3e41620-113959

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(n)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

Note 5 - Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2015

Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]

Year Ending December 31:	Amount

2015	$	42
2016		168
2017		168
2018		84
Total minimum lease payments	$	462

Note 6 - Common Stock (Tables)	9 Months Ended
Note 6 - Common Stock (Tables)	Sep. 30, 2015
Notes Tables
Common Stock Reserve for Future Issuance [Table Text Block]	<div style="display: inline; font-family: times new roman; font-size: 10pt"><table cellpadding="0" cellspacing="0" style="border-collapse: collapse;; width: 700px;"> <tr style="vertical-align: bottom"> <td nowrap="nowrap" style="font-size: 10pt"> </td> <td nowrap="nowrap" style="font-size: 10pt; font-weight: bold; padding-bottom: 1pt"> </td> <td colspan="3" nowrap="nowrap" style="font-size: 10pt; font-weight: bold; text-align: center; border-bottom: Black 1pt solid"><div style=" margin-top: 0; margin-bottom: 0">September 30,</div> <div style=" margin-top: 0; margin-bottom: 0">2015</div></td> <td nowrap="nowrap" style="font-size: 10pt; font-weight: bold; padding-bottom: 1pt"> </td> <td colspan="3" nowrap="nowrap" style="font-size: 10pt; font-weight: bold; text-align: center; border-bottom: Black 1pt solid"><div style=" margin-top: 0; margin-bottom: 0">December 31,</div> <div style=" margin-top: 0; margin-bottom: 0">2014</div></td> </tr> <tr style="vertical-align: bottom"> <td style="font-size: 10pt"> </td> <td style="font-size: 10pt"> </td> <td colspan="3" style="font-size: 10pt; text-align: center"> </td> <td style="font-size: 10pt"> </td> <td colspan="3" style="font-size: 10pt; text-align: center"> </td> </tr> <tr style="vertical-align: bottom; background-color: rgb(204,238,255)"> <td style="width: 70%; font-size: 10pt; text-align: left">Stock-based compensation awards</td> <td style="width: 1%; font-size: 10pt"> </td> <td style="width: 1%; font-size: 10pt; text-align: left"> </td> <td style="width: 12%; font-size: 10pt; text-align: right">2,440,127</td> <td style="width: 1%; font-size: 10pt; text-align: left"> </td> <td style="width: 1%; font-size: 10pt"> </td> <td style="width: 1%; font-size: 10pt; text-align: left"> </td> <td style="width: 12%; font-size: 10pt; text-align: right">1,807,349</td> <td style="width: 1%; font-size: 10pt; text-align: left"> </td> </tr> <tr style="vertical-align: bottom; background-color: White"> <td style="font-size: 10pt; text-align: left; padding-bottom: 1pt">Employee Stock Purchase Plan</td> <td style="font-size: 10pt; padding-bottom: 1pt"> </td> <td style="border-bottom: Black 1pt solid; font-size: 10pt; text-align: left"> </td> <td style="border-bottom: Black 1pt solid; font-size: 10pt; text-align: right">299,127</td> <td style="border-bottom: Black 1pt solid; font-size: 10pt; text-align: left"> </td> <td style="font-size: 10pt; padding-bottom: 1pt"> </td> <td style="border-bottom: Black 1pt solid; font-size: 10pt; text-align: left"> </td> <td style="border-bottom: Black 1pt solid; font-size: 10pt; text-align: right">140,500</td> <td style="border-bottom: Black 1pt solid; font-size: 10pt; text-align: left"> </td> </tr> <tr style="vertical-align: bottom; background-color: rgb(204,238,255)"> <td style="font-size: 10pt; padding-bottom: 2.25pt">Total</td> <td style="font-size: 10pt; padding-bottom: 2.25pt"> </td> <td style="border-bottom: Black 2.25pt double; font-size: 10pt; text-align: left"> </td> <td style="border-bottom: Black 2.25pt double; font-size: 10pt; text-align: right">2,739,254</td> <td style="border-bottom: Black 2.25pt double; font-size: 10pt; text-align: left"> </td> <td style="font-size: 10pt; padding-bottom: 2.25pt"> </td> <td style="border-bottom: Black 2.25pt double; font-size: 10pt; text-align: left"> </td> <td style="border-bottom: Black 2.25pt double; font-size: 10pt; text-align: right">1,947,849</td> <td style="border-bottom: Black 2.25pt double; font-size: 10pt; text-align: left"> </td> </tr> </table></div>

Note 7 - Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2015

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

	Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (years)		Aggregate Intrinsic Value

Outstanding at December 31, 2014		1,235,526		$	4.19		7.1	$	7,709
Granted		589,924		$	12.68
Exercised		(25,188	)
Outstanding at September 30, 2015		1,800,262		$	7.00		7.4	$	13,061
Exercisable at September 30, 2015		775,789		$	3.22		5.2	$	8,310
Vested or expected to vest at September 30, 2015 (1)		1,683,543		$	6.91		7.3	$	12,403

Note 9 - Net Loss Per Share Attributable to Common Stockholders (Tables)

9 Months Ended

Sep. 30, 2015

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]

	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
Convertible preferred stock		-		7,581		-		7,581
Common stock warrants		-		660		-		660
Outstanding stock options		1,800		1,134		1,800		1,134
Outstanding ESPP shares		1		-		1		-
		1,801		9,375		1,801		9,375

Note 1 - Organization and Operations (Details Textual) - USD ($)	Sep. 30, 2015	Dec. 31, 2014	Oct. 27, 2014
Common Stock, Par or Stated Value Per Share	$ 0.001	$ 0.001	$ 0.001
Cash, Cash Equivalents, and Short-term Investments	$ 70,500,000
Retained Earnings (Accumulated Deficit)	$ (124,909,000)	$ (109,874,000)