Organization and Significant Accounting Policies (Policies)	12 Months Ended
Sep. 30, 2013
Nature of Business	Nature of Business Arrowhead Research Corporation is a biopharmaceutical company developing targeted RNAi therapeutics. The Company is leveraging its proprietary drug delivery technologies to develop targeted drugs based on the RNA interference mechanism that efficiently silence disease-causing genes. Arrowhead technologies also enable partners to create peptide-drug conjugates that specifically home to cell types of interest while sparing off-target tissues. Arrowhead’s pipeline includes clinical programs in chronic hepatitis B virus and obesity and partner-based programs in oncology.
Liquidity	Liquidity Historically, The Company’s primary source of financing has been through the sale of securities of Arrowhead Research Corp. Research and development activities have required significant capital investment since the Company’s inception and we expect our operations to continue to require cash investment in fiscal 2014 and beyond as the Company continues its research and development efforts, as well as clinical trials, and related drug manufacturing. At September 30, 2013, the Company had $19.1 million in cash to fund operations. In addition to its cash resources, the Company has invested excess cash in investment grade commercial bonds maturing in less than 18 months. These bonds provide a source of liquidity, although the Company plans to hold them until maturity. At September 30, 2013, the Company had invested $10.8 million in these bonds. During October 2013, the Company completed an additional financing through the sale of equity securities in the amount of $60 million, providing additional liquidity to the Company. During the year ended September 30, 2013, the Company’s cash position increased by $15.7 million. The Company received cash from the issuance of equity of $44.5 million, cash from the sale of its holdings of stock in Wisepower Co. Ltd of $1.4 million, and cash from licensing revenue of $0.2 million. The Company had cash outflow of $19.8 million related to its continuing operating activities and capital expenditures of $0.3 million. On October 21, 2011, Arrowhead completed the acquisition of certain RNAi assets from Hoffmann-La Roche Inc. and F. Hoffmann-La Roche Ltd., including intellectual property and a research and development facility in Madison, Wisconsin. At the time of the acquisition, the facility had 41 employees. Due to the costs associated with operating the facility, including personnel costs, rent, research and development expenses, and other costs, cash expenses have increased, and it is expected that the Company will incur higher cash expenses during the remainder of 2013 and beyond, relative to periods prior to the acquisition, as the Company accelerates its preclinical and clinical development efforts.
Principles of Consolidation	Principles of Consolidation—The consolidated financial statements include the accounts of Arrowhead and its Subsidiaries, Arrowhead Madison, Calando, Ablaris, Tego, and until its disposition in January 2011, Unidym. In 2013, Agonn and Alvos were merged into Arrowhead. Prior to April 2008, Arrowhead’s Subsidiaries included Insert Therapeutics, Inc. (“Insert”), which was merged with Calando in April 2008. The merged entity is majority-owned by Arrowhead and continues to operate under the name of Calando. In January 2011, Arrowhead sold its interests in Unidym to Wisepower, and in December 2009, Tego completed a sale of its assets to Luna Innovations, Inc. Unidym and Tego results are included in the Income (Loss) from Discontinued Operations. Income (Loss) from Discontinued Operations also includes Aonex Technologies, Inc., sold in May 2008, and Nanotechnica, Inc., dissolved in June 2005. All significant intercompany accounts and transactions are eliminated in consolidation, and noncontrolling interests are accounted for in the Company’s financial statements.
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates—The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Significant estimates made in preparing these financial statements include valuing the stock of the Subsidiaries, assumptions to calculate stock-based compensation expense, allowance for doubtful accounts, deferred tax asset valuation allowance, derivative assets and liabilities, contingent consideration, noncontrolling interest and useful lives for depreciable and amortizable assets. Actual results could differ from those estimates. Additionally, certain reclassifications have been made to prior period financial statements to conform to the current period presentation. In the opinion of management, all adjustments, including normal recurring accruals considered necessary for a fair presentation, have been included.
Cash and Cash Equivalents	Cash and Cash Equivalents—The Company considers all liquid debt instruments purchased with a maturity of three months or less to be cash equivalents. The Company had no restricted cash at September 30, 2012 and 2013.
Concentration of Credit Risk	Concentration of Credit Risk—The Company maintains checking accounts for Arrowhead and separate accounts for each Subsidiary at two financial institutions. These accounts are insured by the Federal Deposit Insurance Corporation (FDIC) for up to $250,000 per account. Management believes the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which these deposits are held.
Investments	Investments—the Company invests excess cash balances in short-term and long-term marketable debt securities. Investments may consist of certificates of deposits, money market accounts, government-sponsored enterprise securities, corporate bonds and/or commercial paper. The Company accounts for its investment in marketable securities in accordance with FASB ASC 320, Investments – Debt and Equity Securities. This statement requires certain securities to be classified into three categories: Held-to-maturity—Debt securities that the entity has the positive intent and ability to hold to maturity are reported at amortized cost. Trading Securities—Debt and equity securities that are bought and held primarily for the purpose of selling in the near term are reported at fair value, with unrealized gains and losses included in earnings. Available-for-Sale—Debt and equity securities not classified as either securities held-to-maturity or trading securities are reported at fair value with unrealized gains or losses excluded from earnings and reported as a separate component of shareholders’ equity. The Company classifies its investments in marketable debt securities based on the facts and circumstances present at the time of purchase of the securities. At September 30, 2013, the Company classified all of its investments as held-to-maturity. Held-to-maturity investments are measured and recorded at amortized cost on the Company’s Consolidated Balance Sheet. Discounts and premiums to par value of the debt securities are amortized to interest income/expense over the term of the security. No gains or losses on investment securities are realized until they are sold or a decline in fair value is determined to be other-than-temporary. As of September 30, 2013, all short-term investments were comprised of corporate bonds with maturity dates of less than one year. Certain investments maturing in excess of twelve months, but less than 24 months are classified as long-term investments. As of September 30, 2013, the amortized cost of such bonds was $10,732,414. For the year ended September 30, 2013, gross unrealized losses were $41,643; gross unrealized gains were $7,500. The total fair value of the investments at September 30, 2013 was $10,698,271. See further information regarding fair market value of marketable debt securities in Note 11 – Fair Value Measurements, such fair market data is obtained from independent pricing services.
Property and Equipment	Property and Equipment—Property and equipment are recorded at cost, which may equal fair market value in the case of property and equipment acquired in conjunction with a business acquisition. Depreciation of property and equipment is recorded using the straight-line method over the respective useful lives of the assets ranging from three to seven years. Leasehold improvements are amortized over the lesser of the expected useful life or the remaining lease term. Long-lived assets, including property and equipment are reviewed for impairment whenever events or circumstances indicate that the carrying amount of these assets may not be recoverable.
Intangible Assets subject to amortization	Intangible Assets Subject to Amortization—At September 30, 2013, intangible assets subject to amortization included patents and certain license agreements. Intangible assets subject to amortization are reviewed for impairment whenever events or circumstances indicate that the carrying amount of these assets may not be recoverable.
In-Process Research & Development (IPR&D)	In-Process Research & Development (IPR&D)—IPR&D assets represent capitalized on-going research projects that Arrowhead acquired through business combinations. Such assets are initially measured at their acquisition date fair values. The amounts capitalized are being accounted for as indefinite-lived intangible assets, subject to impairment testing until completion or abandonment of R&D efforts associated with the project. Upon successful completion of a project, Arrowhead will make a determination as to the then remaining useful life of the intangible asset and begin amortization. Based on early adoption of ASU 2012-02, Arrowhead tests its indefinite-lived assets for impairment at least annually, through a two-step process. The first step is a qualitative assessment to determine if it is more likely than not that the indefinite lived assets are impaired. Arrowhead considers relevant events and circumstances that could affect the inputs used to determine the fair value of the intangible assets. If the qualitative assessment indicates that it is more likely than not that the intangible assets is impaired, a second step is performed which is a quantitative test to determine the fair value of the intangible asset. If the carrying amount of the intangible assets exceeds its fair value, an impairment loss is recorded in the amount of that excess. If circumstances determine that it is appropriate, the Company may also elect to bypass step one, and proceed directly to the second step.
Contingent Consideration	Contingent Consideration - The consideration for our acquisitions often includes future payments that are contingent upon the occurrence of a particular event. For example, milestone payments might be based on the achievement of various regulatory approvals or future sales milestones, and royalty payments might be based on drug product sales levels. We record a contingent consideration obligation for such contingent payments at fair value on the acquisition date. We estimate the fair value of contingent consideration obligations through valuation models designed to estimate the probability of such contingent payments based on various assumptions and incorporating estimated success rates. Estimated payments are discounted using present value techniques to arrive at estimated fair value at the balance sheet date. We revalue these contingent consideration obligations each reporting period. Changes in the fair value of our contingent consideration obligations are recognized within our consolidated statements of operations. Changes in the fair value of the contingent consideration obligations can result from changes to one or multiple inputs, including adjustments to the discount rates, changes in the amount or timing of expected expenditures associated with product development, changes in the amount or timing of cash flows from products upon commercialization, changes in the assumed achievement or timing of any development milestones, changes in the probability of certain clinical events and changes in the assumed probability associated with regulatory approval. These fair value measurements are based on significant inputs not observable in the market. Significant judgment is employed in determining the appropriateness of these assumptions as of the acquisition date and for each subsequent period. Accordingly, changes in assumptions could have a material impact on the amount of contingent consideration expense we record in any given period.
Equity Investments	Equity Investments—Arrowhead had a noncontrolling equity investment in Nanotope, a privately held biotechnology company, which is recorded in Other Assets. Historically, this investment was carried at cost less Arrowhead’s proportionate share of Nanotope’s operating loss for the period since investment. The investment was fully reserved in 2012. During 2013, Nanotope was dissolved.
Minority Equity Investments	Minority Equity Investments—The Company’s minority equity investment in Leonardo, a privately held biotechnology company, had been recorded in Other Assets, however, an impairment charge was recorded in 2012, and its net book value at September 30, 2013 is $0. This investment has been accounted for under the cost method of accounting.
Noncontrolling Interests in Majority-Owned Subsidiaries	Noncontrolling Interests in Majority-Owned Subsidiaries—Operating losses applicable to majority-owned Calando, Ablaris and, prior to its disposal, Unidym have periodically exceeded the noncontrolling interests in the equity capital of either Subsidiary. Such excess losses applicable to the noncontrolling interests have been and are borne by the Company as there is no obligation of the noncontrolling interests to fund any losses in excess of their original investment. There is also no obligation or commitment on the part of the Company to fund operating losses of any Subsidiary whether wholly-owned or majority-owned. The Company allocates the noncontrolling interest’s share of net loss in excess of the noncontrolling interest’s initial investment in accordance with FASB ASC 810-10. When there is a change in the Company’s proportionate share of a development-stage Subsidiary resulting from additional equity transactions in a Subsidiary, the change is accounted for as an equity transaction in consolidation. To the extent that the increase in the calculated value of the Company’s interest in the equity of the Subsidiary exceeds the Company’s investment in the offering, that increase in value is referred to as the Company’s “increase in its proportionate share of the Subsidiary’s equity” and the amount is recorded as an increase in the Company’s Additional Paid-in Capital.
Revenue Recognition	Revenue Recognition—Revenue from license fees are recorded when persuasive evidence of an arrangement exists, title has passed or services have been rendered, a price is fixed and determinable, and collection is reasonably assured. We may generate revenue from product sales, technology licenses, collaborative research and development arrangements, and research grants. Revenue under technology licenses and collaborative agreements typically consists of nonrefundable and/or guaranteed technology license fees, collaborative research funding and various milestone and future product royalty or profit-sharing payments. Revenue associated with research and development funding payments under collaborative agreements, is recognized ratably over the relevant periods specified in the agreement, generally the research and development period. Revenue from up-front license fees, milestones and product royalties are recognized as earned based on the completion of the milestones and product sales, as defined in the respective agreements. Payments received in advance of recognition as revenue are recorded as deferred revenue.
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts—The Company accrues an allowance for doubtful accounts based on estimates of uncollectible revenues by analyzing historical collections, accounts receivable aging and other factors. Accounts receivable are written off when all collection attempts have failed.
Research and Development	Research and Development—Costs and expenses that can be clearly identified as research and development are charged to expense as incurred in accordance with FASB ASC 730-10.
Earnings (Loss) per Share	Earnings (Loss) per Share—Basic earnings (loss) per share is computed using the weighted-average number of common shares outstanding during the period. Diluted earnings (loss) per share are computed using the weighted-average number of common shares and dilutive potential common shares outstanding during the period. Dilutive potential common shares primarily consist of stock options issued to employees and consultants and warrants to purchase Common Stock of the Company.
Stock-Based Compensation	Stock-Based Compensation—The Company accounts for share-based compensation arrangements in accordance with FASB ASC 718, which requires the measurement and recognition of compensation expense for all share-based payment awards to be based on estimated fair values. We use the Black-Scholes option valuation model to estimate the fair value of our stock options at the date of grant. The Black-Scholes option valuation model requires the input of subjective assumptions to calculate the value of stock options. We use historical data among other information to estimate the expected price volatility and the expected forfeiture rate.
Derivative Assets and Liabilities	Derivative Assets and Liabilities - We account for warrants and other derivative financial instruments as either equity or assets/liabilities based upon the characteristics and provisions of each instrument. Warrants classified as equity are recorded as additional paid-in capital on our consolidated balance sheet and no further adjustments to their valuation are made. Some of our warrants were determined to be ineligible for equity classification because of provisions that may result in an adjustment to their exercise price. Warrants classified as derivative liabilities and other derivative financial instruments that require separate accounting as assets or liabilities are recorded on our consolidated balance sheet at their fair value on the date of issuance and are revalued on each subsequent balance sheet date until such instruments are exercised or expire, with any changes in the fair value between reporting periods recorded as other income or expense. We estimate the fair value of these assets/liabilities using option pricing models that are based on the individual characteristics of the warrants or instruments on the valuation date, as well as assumptions for expected volatility, expected life and risk-free interest rate.
Income Taxes	Income Taxes—The Company accounts for income taxes under the liability method, which requires the recognition of deferred income tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Under this method, deferred income taxes are recognized for the tax consequences in future years of differences between the tax bases of assets and liabilities and their financial reporting amounts at each period end based on enacted tax laws and statutory tax rates applicable to the periods in which the differences are expected to affect taxable income. Valuation allowances are established, when necessary, to reduce deferred income tax assets to the amount expected to be realized. The provision for income taxes, if any, represents the tax payable for the period and the change in deferred income tax assets and liabilities during the period.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In July 2012, the FASB issued ASU 2012-02, Testing Indefinite-Lived Intangible Assets for Impairment, which amended the guidance in ASU 2011-08 to simplify the testing of indefinite-lived intangible assets other than goodwill for impairment. ASU 2012-02 becomes effective for annual and interim impairment tests performed for fiscal years beginning on or after September 15, 2012 and earlier adoption is permitted. We adopted this standard in the third quarter of fiscal year 2012. We believe adoption did not have a material effect on our financial statements. In September 2011, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2011-08, Intangibles—Goodwill and Other (Topic 350)—Testing Goodwill for Impairment (ASU 2011-08), to allow entities to use a qualitative approach to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying value. If after performing the qualitative assessment an entity determines it is not more likely than not that the fair value of a reporting unit is less than its carrying amount, then performing the two-step goodwill impairment test is unnecessary. However, if an entity concludes otherwise, then it is required to perform the first step of the two-step goodwill impairment test. ASU 2011-08 is effective for us in fiscal 2013 and earlier adoption is permitted. The adoption of ASU 2011-08 did not have a material impact on our financial position, results of operations or cash flows. In May 2011, the Financial Accounting Standards Board (“FASB”) issued ASU 2011-04, Fair Value Measurement (“ASU 2011-04”), which amended ASC 820, Fair Value Measurements (“ASC 820”), providing a consistent definition and measurement of fair value, as well as similar disclosure requirements between U.S. GAAP and International Financial Reporting Standards. ASU 2011-04 changes certain fair value measurement principles, clarifies the application of existing fair value measurement and expands the disclosure requirements. ASU 2011-04 was effective for us beginning January 1, 2012. The adoption of ASU 2011-04 did not have a material effect on our consolidated financial statements or disclosures.

Organization and Significant Accounting Policies (Policies)

12 Months Ended

Sep. 30, 2013

Arrowhead Research Corporation is a biopharmaceutical company developing targeted RNAi therapeutics. The Company is leveraging its proprietary drug delivery technologies to develop targeted drugs based on the RNA interference mechanism that efficiently silence disease-causing genes. Arrowhead technologies also enable partners to create peptide-drug conjugates that specifically home to cell types of interest while sparing off-target tissues. Arrowhead’s pipeline includes clinical programs in chronic hepatitis B virus and obesity and partner-based programs in oncology.

Liquidity

Historically, The Company’s primary source of financing has been through the sale of securities of Arrowhead Research Corp. Research and development activities have required significant capital investment since the Company’s inception and we expect our operations to continue to require cash investment in fiscal 2014 and beyond as the Company continues its research and development efforts, as well as clinical trials, and related drug manufacturing.

At September 30, 2013, the Company had $19.1 million in cash to fund operations. In addition to its cash resources, the Company has invested excess cash in investment grade commercial bonds maturing in less than 18 months. These bonds provide a source of liquidity, although the Company plans to hold them until maturity. At September 30, 2013, the Company had invested $10.8 million in these bonds. During October 2013, the Company completed an additional financing through the sale of equity securities in the amount of $60 million, providing additional liquidity to the Company. During the year ended September 30, 2013, the Company’s cash position increased by $15.7 million. The Company received cash from the issuance of equity of $44.5 million, cash from the sale of its holdings of stock in Wisepower Co. Ltd of $1.4 million, and cash from licensing revenue of $0.2 million. The Company had cash outflow of $19.8 million related to its continuing operating activities and capital expenditures of $0.3 million.

On October 21, 2011, Arrowhead completed the acquisition of certain RNAi assets from Hoffmann-La Roche Inc. and F. Hoffmann-La Roche Ltd., including intellectual property and a research and development facility in Madison, Wisconsin. At the time of the acquisition, the facility had 41 employees. Due to the costs associated with operating the facility, including personnel costs, rent, research and development expenses, and other costs, cash expenses have increased, and it is expected that the Company will incur higher cash expenses during the remainder of 2013 and beyond, relative to periods prior to the acquisition, as the Company accelerates its preclinical and clinical development efforts.

Principles of Consolidation

Principles of Consolidation—The consolidated financial statements include the accounts of Arrowhead and its Subsidiaries, Arrowhead Madison, Calando, Ablaris, Tego, and until its disposition in January 2011, Unidym. In 2013, Agonn and Alvos were merged into Arrowhead. Prior to April 2008, Arrowhead’s Subsidiaries included Insert Therapeutics, Inc. (“Insert”), which was merged with Calando in April 2008. The merged entity is majority-owned by Arrowhead and continues to operate under the name of Calando. In January 2011, Arrowhead sold its interests in Unidym to Wisepower, and in December 2009, Tego completed a sale of its assets to Luna Innovations, Inc. Unidym and Tego results are included in the Income (Loss) from Discontinued Operations. Income (Loss) from Discontinued Operations also includes Aonex Technologies, Inc., sold in May 2008, and Nanotechnica, Inc., dissolved in June 2005. All significant intercompany accounts and transactions are eliminated in consolidation, and noncontrolling interests are accounted for in the Company’s financial statements.

Basis of Presentation and Use of Estimates

Basis of Presentation and Use of Estimates—The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Significant estimates made in preparing these financial statements include valuing the stock of the Subsidiaries, assumptions to calculate stock-based compensation expense, allowance for doubtful accounts, deferred tax asset valuation allowance, derivative assets and liabilities, contingent consideration, noncontrolling interest and useful lives for depreciable and amortizable assets. Actual results could differ from those estimates. Additionally, certain reclassifications have been made to prior period financial statements to conform to the current period presentation. In the opinion of management, all adjustments, including normal recurring accruals considered necessary for a fair presentation, have been included.

Cash and Cash Equivalents

Cash and Cash Equivalents—The Company considers all liquid debt instruments purchased with a maturity of three months or less to be cash equivalents. The Company had no restricted cash at September 30, 2012 and 2013.

Concentration of Credit Risk

Concentration of Credit Risk—The Company maintains checking accounts for Arrowhead and separate accounts for each Subsidiary at two financial institutions. These accounts are insured by the Federal Deposit Insurance Corporation (FDIC) for up to $250,000 per account. Management believes the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which these deposits are held.

Investments

Investments—the Company invests excess cash balances in short-term and long-term marketable debt securities. Investments may consist of certificates of deposits, money market accounts, government-sponsored enterprise securities, corporate bonds and/or commercial paper. The Company accounts for its investment in marketable securities in accordance with FASB ASC 320, Investments – Debt and Equity Securities. This statement requires certain securities to be classified into three categories:

Held-to-maturity—Debt securities that the entity has the positive intent and ability to hold to maturity are reported at amortized cost.

Trading Securities—Debt and equity securities that are bought and held primarily for the purpose of selling in the near term are reported at fair value, with unrealized gains and losses included in earnings.

Available-for-Sale—Debt and equity securities not classified as either securities held-to-maturity or trading securities are reported at fair value with unrealized gains or losses excluded from earnings and reported as a separate component of shareholders’ equity.

The Company classifies its investments in marketable debt securities based on the facts and circumstances present at the time of purchase of the securities. At September 30, 2013, the Company classified all of its investments as held-to-maturity.

Held-to-maturity investments are measured and recorded at amortized cost on the Company’s Consolidated Balance Sheet. Discounts and premiums to par value of the debt securities are amortized to interest income/expense over the term of the security. No gains or losses on investment securities are realized until they are sold or a decline in fair value is determined to be other-than-temporary.

As of September 30, 2013, all short-term investments were comprised of corporate bonds with maturity dates of less than one year. Certain investments maturing in excess of twelve months, but less than 24 months are classified as long-term investments. As of September 30, 2013, the amortized cost of such bonds was $10,732,414. For the year ended September 30, 2013, gross unrealized losses were $41,643; gross unrealized gains were $7,500. The total fair value of the investments at September 30, 2013 was $10,698,271.

See further information regarding fair market value of marketable debt securities in Note 11 – Fair Value Measurements, such fair market data is obtained from independent pricing services.

Property and Equipment

Property and Equipment—Property and equipment are recorded at cost, which may equal fair market value in the case of property and equipment acquired in conjunction with a business acquisition. Depreciation of property and equipment is recorded using the straight-line method over the respective useful lives of the assets ranging from three to seven years. Leasehold improvements are amortized over the lesser of the expected useful life or the remaining lease term. Long-lived assets, including property and equipment are reviewed for impairment whenever events or circumstances indicate that the carrying amount of these assets may not be recoverable.

Intangible Assets subject to amortization

Intangible Assets Subject to Amortization—At September 30, 2013, intangible assets subject to amortization included patents and certain license agreements. Intangible assets subject to amortization are reviewed for impairment whenever events or circumstances indicate that the carrying amount of these assets may not be recoverable.

In-Process Research & Development (IPR&D)

In-Process Research & Development (IPR&D)—IPR&D assets represent capitalized on-going research projects that Arrowhead acquired through business combinations. Such assets are initially measured at their acquisition date fair values. The amounts capitalized are being accounted for as indefinite-lived intangible assets, subject to impairment testing until completion or abandonment of R&D efforts associated with the project. Upon successful completion of a project, Arrowhead will make a determination as to the then remaining useful life of the intangible asset and begin amortization. Based on early adoption of ASU 2012-02, Arrowhead tests its indefinite-lived assets for impairment at least annually, through a two-step process. The first step is a qualitative assessment to determine if it is more likely than not that the indefinite lived assets are impaired. Arrowhead considers relevant events and circumstances that could affect the inputs used to determine the fair value of the intangible assets. If the qualitative assessment indicates that it is more likely than not that the intangible assets is impaired, a second step is performed which is a quantitative test to determine the fair value of the intangible asset. If the carrying amount of the intangible assets exceeds its fair value, an impairment loss is recorded in the amount of that excess. If circumstances determine that it is appropriate, the Company may also elect to bypass step one, and proceed directly to the second step.

Contingent Consideration

Contingent Consideration - The consideration for our acquisitions often includes future payments that are contingent upon the occurrence of a particular event. For example, milestone payments might be based on the achievement of various regulatory approvals or future sales milestones, and royalty payments might be based on drug product sales levels. We record a contingent consideration obligation for such contingent payments at fair value on the acquisition date. We estimate the fair value of contingent consideration obligations through valuation models designed to estimate the probability of such contingent payments based on various assumptions and incorporating estimated success rates. Estimated payments are discounted using present value techniques to arrive at estimated fair value at the balance sheet date. We revalue these contingent consideration obligations each reporting period. Changes in the fair value of our contingent consideration obligations are recognized within our consolidated statements of operations. Changes in the fair value of the contingent consideration obligations can result from changes to one or multiple inputs, including adjustments to the discount rates, changes in the amount or timing of expected expenditures associated with product development, changes in the amount or timing of cash flows from products upon commercialization, changes in the assumed achievement or timing of any development milestones, changes in the probability of certain clinical events and changes in the assumed probability associated with regulatory approval. These fair value measurements are based on significant inputs not observable in the market. Significant judgment is employed in determining the appropriateness of these assumptions as of the acquisition date and for each subsequent period. Accordingly, changes in assumptions could have a material impact on the amount of contingent consideration expense we record in any given period.

Equity Investments

Equity Investments—Arrowhead had a noncontrolling equity investment in Nanotope, a privately held biotechnology company, which is recorded in Other Assets. Historically, this investment was carried at cost less Arrowhead’s proportionate share of Nanotope’s operating loss for the period since investment. The investment was fully reserved in 2012. During 2013, Nanotope was dissolved.

Minority Equity Investments

Minority Equity Investments—The Company’s minority equity investment in Leonardo, a privately held biotechnology company, had been recorded in Other Assets, however, an impairment charge was recorded in 2012, and its net book value at September 30, 2013 is $0. This investment has been accounted for under the cost method of accounting.

Noncontrolling Interests in Majority-Owned Subsidiaries

Noncontrolling Interests in Majority-Owned Subsidiaries—Operating losses applicable to majority-owned Calando, Ablaris and, prior to its disposal, Unidym have periodically exceeded the noncontrolling interests in the equity capital of either Subsidiary. Such excess losses applicable to the noncontrolling interests have been and are borne by the Company as there is no obligation of the noncontrolling interests to fund any losses in excess of their original investment. There is also no obligation or commitment on the part of the Company to fund operating losses of any Subsidiary whether wholly-owned or majority-owned. The Company allocates the noncontrolling interest’s share of net loss in excess of the noncontrolling interest’s initial investment in accordance with FASB ASC 810-10.

When there is a change in the Company’s proportionate share of a development-stage Subsidiary resulting from additional equity transactions in a Subsidiary, the change is accounted for as an equity transaction in consolidation. To the extent that the increase in the calculated value of the Company’s interest in the equity of the Subsidiary exceeds the Company’s investment in the offering, that increase in value is referred to as the Company’s “increase in its proportionate share of the Subsidiary’s equity” and the amount is recorded as an increase in the Company’s Additional Paid-in Capital.

Revenue Recognition

Revenue Recognition—Revenue from license fees are recorded when persuasive evidence of an arrangement exists, title has passed or services have been rendered, a price is fixed and determinable, and collection is reasonably assured. We may generate revenue from product sales, technology licenses, collaborative research and development arrangements, and research grants. Revenue under technology licenses and collaborative agreements typically consists of nonrefundable and/or guaranteed technology license fees, collaborative research funding and various milestone and future product royalty or profit-sharing payments.

Revenue associated with research and development funding payments under collaborative agreements, is recognized ratably over the relevant periods specified in the agreement, generally the research and development period. Revenue from up-front license fees, milestones and product royalties are recognized as earned based on the completion of the milestones and product sales, as defined in the respective agreements. Payments received in advance of recognition as revenue are recorded as deferred revenue.

Allowance for Doubtful Accounts

Allowance for Doubtful Accounts—The Company accrues an allowance for doubtful accounts based on estimates of uncollectible revenues by analyzing historical collections, accounts receivable aging and other factors. Accounts receivable are written off when all collection attempts have failed.

Research and Development

Research and Development—Costs and expenses that can be clearly identified as research and development are charged to expense as incurred in accordance with FASB ASC 730-10.

Earnings (Loss) per Share

Earnings (Loss) per Share—Basic earnings (loss) per share is computed using the weighted-average number of common shares outstanding during the period. Diluted earnings (loss) per share are computed using the weighted-average number of common shares and dilutive potential common shares outstanding during the period. Dilutive potential common shares primarily consist of stock options issued to employees and consultants and warrants to purchase Common Stock of the Company.

Stock-Based Compensation

Stock-Based Compensation—The Company accounts for share-based compensation arrangements in accordance with FASB ASC 718, which requires the measurement and recognition of compensation expense for all share-based payment awards to be based on estimated fair values. We use the Black-Scholes option valuation model to estimate the fair value of our stock options at the date of grant. The Black-Scholes option valuation model requires the input of subjective assumptions to calculate the value of stock options. We use historical data among other information to estimate the expected price volatility and the expected forfeiture rate.

Derivative Assets and Liabilities

Derivative Assets and Liabilities - We account for warrants and other derivative financial instruments as either equity or assets/liabilities based upon the characteristics and provisions of each instrument. Warrants classified as equity are recorded as additional paid-in capital on our consolidated balance sheet and no further adjustments to their valuation are made. Some of our warrants were determined to be ineligible for equity classification because of provisions that may result in an adjustment to their exercise price. Warrants classified as derivative liabilities and other derivative financial instruments that require separate accounting as assets or liabilities are recorded on our consolidated balance sheet at their fair value on the date of issuance and are revalued on each subsequent balance sheet date until such instruments are exercised or expire, with any changes in the fair value between reporting periods recorded as other income or expense. We estimate the fair value of these assets/liabilities using option pricing models that are based on the individual characteristics of the warrants or instruments on the valuation date, as well as assumptions for expected volatility, expected life and risk-free interest rate.

Income Taxes

Income Taxes—The Company accounts for income taxes under the liability method, which requires the recognition of deferred income tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Under this method, deferred income taxes are recognized for the tax consequences in future years of differences between the tax bases of assets and liabilities and their financial reporting amounts at each period end based on enacted tax laws and statutory tax rates applicable to the periods in which the differences are expected to affect taxable income. Valuation allowances are established, when necessary, to reduce deferred income tax assets to the amount expected to be realized. The provision for income taxes, if any, represents the tax payable for the period and the change in deferred income tax assets and liabilities during the period.

Recently Issued Accounting Standards

In July 2012, the FASB issued ASU 2012-02, Testing Indefinite-Lived Intangible Assets for Impairment, which amended the guidance in ASU 2011-08 to simplify the testing of indefinite-lived intangible assets other than goodwill for impairment. ASU 2012-02 becomes effective for annual and interim impairment tests performed for fiscal years beginning on or after September 15, 2012 and earlier adoption is permitted. We adopted this standard in the third quarter of fiscal year 2012. We believe adoption did not have a material effect on our financial statements.

In September 2011, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2011-08, Intangibles—Goodwill and Other (Topic 350)—Testing Goodwill for Impairment (ASU 2011-08), to allow entities to use a qualitative approach to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying value. If after performing the qualitative assessment an entity determines it is not more likely than not that the fair value of a reporting unit is less than its carrying amount, then performing the two-step goodwill impairment test is unnecessary. However, if an entity concludes otherwise, then it is required to perform the first step of the two-step goodwill impairment test. ASU 2011-08 is effective for us in fiscal 2013 and earlier adoption is permitted. The adoption of ASU 2011-08 did not have a material impact on our financial position, results of operations or cash flows.

In May 2011, the Financial Accounting Standards Board (“FASB”) issued ASU 2011-04, Fair Value Measurement (“ASU 2011-04”), which amended ASC 820, Fair Value Measurements (“ASC 820”), providing a consistent definition and measurement of fair value, as well as similar disclosure requirements between U.S. GAAP and International Financial Reporting Standards. ASU 2011-04 changes certain fair value measurement principles, clarifies the application of existing fair value measurement and expands the disclosure requirements. ASU 2011-04 was effective for us beginning January 1, 2012. The adoption of ASU 2011-04 did not have a material effect on our consolidated financial statements or disclosures.