##### Table of Contents

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549





Form 10-Q







|           |  |                                                                                         
|---------- |  | ----------------------------------------------------------------------------------------
|(Mark One) |  |                                                                                         
|[X]        |  | QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d)
OF THE SECURITIES EXCHANGE ACT OF 1934 
|           | 
|           |  | For the Quarterly Period Ended March 31, 2011                                           
|           | 
|           |  | or                                                                                      
|           | 
|[    ]     |  | TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d)
OF THE SECURITIES EXCHANGE ACT OF 1934

Commission File Number: 000-29959





Pain
Therapeutics, Inc.

(Exact name of registrant as specified in its charter)



| |  |                                 |  |                       
| |  | ------------------------------- |  | ----------------------
| |  | Delaware                        |  | 91-1911336            
| |  | (State or other jurisdiction of |  | (I.R.S. Employer      
| |  | incorporation or organization)  |  | Identification Number)

2211 Bridgepointe Parkway

Suite 500

San Mateo, CA 94404

(650) 624-8200

(Address, including zip code, of registrants
principal executive offices and

telephone number, including area code)

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or
15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90
days.  Yes [X]    No [  ]

Indicate by check mark whether the
registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12
months (or for such shorter period that the registrant was required to submit and post such files). Yes [  ]    No [  ]

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or a small reporting company. See the definitions of large accelerated
filer, accelerated filer and smaller reporting company in Rule 12b-2 of the Exchange Act. (Check one):



|                             |  |                               
|---------------------------- |  | ------------------------------
|Large accelerated filer [  ] |  | Accelerated filer [X]         
|                             | 
|Non-accelerated filer [  ]   |  | Smaller reporting Company [  ]

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes [  ]    No [X]

Indicate the number of shares outstanding of each of the issuers classes of common stock, as of the latest
practicable date.



|                               |  |                                        
|------------------------------ |  | ---------------------------------------
|Common Stock, $0.001 par value |  | 44,015,538                             
|                               |  | Shares Outstanding as of April 18, 2011





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##### Table of Contents

PAIN THERAPEUTICS, INC.

TABLE OF CONTENTS

|           |  |                                                                                       |  |         
|---------- |  | ------------------------------------------------------------------------------------- |  | --------
|           |  |                                                                                       |  | Page No.
|PART I.    |  | FINANCIAL INFORMATION                                                                 |  |         
|           |  |                                                                                      
|Item 1.    |  | Financial Statements                                                                  |  |         
|           |  |                                                                                      
|           |  | Condensed Balance Sheets  March 31, 2011 and December 31, 2010                       |  | 3       
|           |  |                                                                                      
|           |  | Condensed Statements of Operations  Three Month Periods EndedMarch 31, 2011 and
2010 |  | 4       
|           |  |                                                                                      
|           |  | Condensed Statements of Cash Flows  Three Month Periods EndedMarch 31, 2011 and
2010 |  | 5       
|           |  |                                                                                      
|           |  | Notes to Condensed Financial Statements                                               |  | 6       
|           |  |                                                                                      
|Item 2.    |  | Managements Discussion and Analysis of Financial Condition andResults of
Operations  |  | 12      
|           |  |                                                                                      
|Item 3.    |  | Quantitative and Qualitative Disclosures About Market Risk                            |  | 21      
|           |  |                                                                                      
|Item 4.    |  | Controls and Procedures                                                               |  | 22      
|           |  |                                                                                      
|PART II.   |  | OTHER INFORMATION                                                                     |  |         
|           |  |                                                                                      
|Item 1.    |  | Legal Proceedings                                                                     |  | 23      
|           |  |                                                                                      
|Item 1A.   |  | Risk Factors                                                                          |  | 23      
|           |  |                                                                                      
|Item 2.    |  | Unregistered Sales of Equity Securities and Use of Proceeds                           |  | 41      
|           |  |                                                                                      
|Item 3.    |  | Defaults Upon Senior Securities                                                       |  | 41      
|           |  |                                                                                      
|Item 4.    |  | (Removed and Reserved)                                                                |  | 41      
|           |  |                                                                                      
|Item 5.    |  | Other Information                                                                     |  | 41      
|           |  |                                                                                      
|Item 6.    |  | Exhibits                                                                              |  | 42      
|           |  |                                                                                      
|Signatures |  |                                                                                       |  | 43      



2



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##### Table of Contents

PART I. FINANCIAL INFORMATION

Item 1.Financial Statements

PAIN THERAPEUTICS, INC.

Condensed Balance Sheets

(Unaudited)

(in thousands)



|                                                   |  |               |          |   |                     |   |          |  
|-------------------------------------------------- |  | ------------- | -------- | - | ------------------- | - | -------- | -
|                                                   |  | March 31,2011 |          |   | December 31,2010(1) |  
|Current assets                                     |  |               |          |   |                     |   |          |  
|Cash and cash equivalents                          |  | $             | 54,894   |   |                     | $ | 4,798    |  
|Marketable securities                              |  |               | 43,583   |   |                     |   | 86,428   |  
|Receivables                                        |  |               | 1,996    |   |                     |   | 7,114    |  
|Other current assets                               |  |               | 84       |   |                     |   | 144      |  
|                                                   |  |               |          |   |                     |   |          |  
|Total current assets                               |  |               | 100,557  |   |                     |   | 98,484   |  
|Non-current assets                                 |  |               |          |   |                     |   |          |  
|Property and equipment, net                        |  |               | 232      |   |                     |   | 285      |  
|Other assets                                       |  |               | 437      |   |                     |   | 426      |  
|                                                   |  |               |          |   |                     |   |          |  
|Total assets                                       |  | $             | 101,226  |   |                     | $ | 99,195   |  
|                                                   |  |               |          |   |                     |   |          |  
|                                                   |  |              
|Current liabilities                                |  |               |          |   |                     |   |          |  
|Accounts payable                                   |  | $             | 436      |   |                     | $ | 1,107    |  
|Accrued development expense                        |  |               | 435      |   |                     |   | 258      |  
|Deferred program fee revenue - current portion     |  |               | 10,897   |   |                     |   | 10,897   |  
|Accrued compensation and benefits                  |  |               | 1,500    |   |                     |   | 1,712    |  
|Other accrued liabilities                          |  |               | 93       |   |                     |   | 97       |  
|                                                   |  |               |          |   |                     |   |          |  
|Total current liabilities                          |  |               | 13,361   |   |                     |   | 14,071   |  
|                                                   |  |              
|Non-current liabilities                            |  |               |          |   |                     |   |          |  
|Deferred program fee revenue - non-current portion |  |               | 49,036   |   |                     |   | 51,760   |  
|Other liabilities                                  |  |               | 432      |   |                     |   | 431      |  
|                                                   |  |               |          |   |                     |   |          |  
|Total liabilities                                  |  |               | 62,829   |   |                     |   | 66,262   |  
|                                                   |  |               |          |   |                     |   |          |  
|                                                   |  |              
|Commitments and contingencies                      |  |               |          |   |                     |   |          |  
|Stockholders equity                               |  |               |          |   |                     |   |          |  
|Preferred stock                                    |  |               | -        |   |                     |   | -        |  
|Common stock                                       |  |               | 44       |   |                     |   | 43       |  
|Additional paid-in-capital                         |  |               | 167,684  |   |                     |   | 161,957  |  
|Accumulated other comprehensive income             |  |               | 468      |   |                     |   | 525      |  
|Accumulated deficit                                |  |               | (129,799 | ) |                     |   | (129,592 | )
|                                                   |  |               |          |   |                     |   |          |  
|Total stockholders equity                         |  |               | 38,397   |   |                     |   | 32,933   |  
|                                                   |  |               |          |   |                     |   |          |  
|Total liabilities and stockholders equity         |  | $             | 101,226  |   |                     | $ | 99,195   |  
|                                                   |  |               |          |   |                     |   |          |  



|(1) | Derived from the Companys audited financial statements as of December 31, 2010, included in the Companys Annual Report on Form 10-K filed with the
Securities and Exchange Commission.
|--- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

See accompanying notes to condensed financial statements.



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PAIN THERAPEUTICS, INC.

Condensed Statements of Operations

(Unaudited)

(in thousands, except per share data)



|                                                            |  |                             |        |   |      |   |        |  
|----------------------------------------------------------- |  | --------------------------- | ------ | - | ---- | - | ------ | -
|                                                            |  | Three Months EndedMarch 31, |       
|                                                            |  | 2011                        |        |   | 2010 |  
|Revenue                                                     |  |                             |        |   |      |   |        |  
|Program fee revenue                                         |  | $                           | 2,724  |   |      | $ | 2,524  |  
|Collaboration revenue                                       |  |                             | 512    |   |      |   | 725    |  
|                                                            |  |                             |        |   |      |   |        |  
|Total revenue                                               |  |                             | 3,236  |   |      |   | 3,249  |  
|                                                            |  |                             |        |   |      |   |        |  
|                                                            |  |                            
|Operating expenses                                          |  |                             |        |   |      |   |        |  
|Research and development                                    |  |                             | 2,178  |   |      |   | 3,127  |  
|General and administrative                                  |  |                             | 1,537  |   |      |   | 1,486  |  
|                                                            |  |                             |        |   |      |   |        |  
|Total operating expenses                                    |  |                             | 3,715  |   |      |   | 4,613  |  
|                                                            |  |                             |        |   |      |   |        |  
|Operating loss                                              |  |                             | (479   | ) |      |   | (1,364 | )
|Interest income                                             |  |                             | 272    |   |      |   | 344    |  
|                                                            |  |                             |        |   |      |   |        |  
|Net loss                                                    |  | $                           | (207   | ) |      | $ | (1,020 | )
|                                                            |  |                             |        |   |      |   |        |  
|                                                            |  |                            
|Net loss per share                                          |  |                             |        |   |      |   |        |  
|Basic and diluted                                           |  | $                           | (0.00  | ) |      | $ | (0.02  | )
|                                                            |  |                             |        |   |      |   |        |  
|Weighted-average shares used in computingnet loss per share |  |                             |        |   |      |   |        |  
|Basic and diluted                                           |  |                             | 43,124 |   |      |   | 42,410 |  
|                                                            |  |                             |        |   |      |   |        |  

See accompanying notes to condensed financial statements.



4



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PAIN THERAPEUTICS, INC.

Condensed Statements of Cash Flows

(Unaudited)

(in thousands)



|                                                                             |  |                              |        |   |      |   |         |  
|---------------------------------------------------------------------------- |  | ---------------------------- | ------ | - | ---- | - | ------- | -
|                                                                             |  | Three Months Ended March 31, |       
|                                                                             |  | 2011                         |        |   | 2010 |  
|Cash flows provided by (used in) operating activities:                       |  |                              |        |   |      |   |         |  
|Net loss                                                                     |  | $                            | (207   | ) |      | $ | (1,020  | )
|Adjustments to reconcile net loss to net cash  used in operating activities: |  |                              |        |   |      |   |         |  
|Non-cash stock based compensation                                            |  |                              | 1,303  |   |      |   | 1,418   |  
|Depreciation and amortization                                                |  |                              | 53     |   |      |   | 60      |  
|Non-cash net interest income                                                 |  |                              | 386    |   |      |   | 731     |  
|Program fee revenue                                                          |  |                              | (2,724 | ) |      |   | (2,524  | )
|Changes in operating assets and liabilities:                                 |  |                              |        |   |      |   |         |  
|Receivables                                                                  |  |                              | 5,118  |   |      |   | 215     |  
|Other current assets                                                         |  |                              | 60     |   |      |   | 316     |  
|Other assets                                                                 |  |                              | (11    | ) |      |   | 1,578   |  
|Accounts payable                                                             |  |                              | (671   | ) |      |   | (832    | )
|Accrued development expense                                                  |  |                              | 177    |   |      |   | (453    | )
|Other accrued liabilities                                                    |  |                              | (3     | ) |      |   | (188    | )
|Accrued compensation and benefits                                            |  |                              | (212   | ) |      |   | (95     | )
|                                                                             |  |                              |        |   |      |   |         |  
|Net cash provided by (used in) operating activities                          |  |                              | 3,269  |   |      |   | (794    | )
|                                                                             |  |                              |        |   |      |   |         |  
|Cash flows provided by investing activities:                                 |  |                              |        |   |      |   |         |  
|Purchases of marketable securities                                           |  |                              | -      |   |      |   | (18,677 | )
|Maturities of marketable securities                                          |  |                              | 42,402 |   |      |   | 33,351  |  
|                                                                             |  |                              |        |   |      |   |         |  
|Net cash provided by investing activities                                    |  |                              | 42,402 |   |      |   | 14,674  |  
|                                                                             |  |                              |        |   |      |   |         |  
|Cash flows provided by financing activities:                                 |  |                              |        |   |      |   |         |  
|Proceeds from exercise of common stock options                               |  |                              | 4,425  |   |      |   | 983     |  
|                                                                             |  |                              |        |   |      |   |         |  
|Net cash provided by financing activities                                    |  |                              | 4,425  |   |      |   | 983     |  
|                                                                             |  |                              |        |   |      |   |         |  
|Net increase in cash and cash equivalents                                    |  |                              | 50,096 |   |      |   | 14,863  |  
|Cash and cash equivalents at beginning of the period                         |  |                              | 4,798  |   |      |   | 35,794  |  
|                                                                             |  |                              |        |   |      |   |         |  
|Cash and cash equivalents at end of the period                               |  | $                            | 54,894 |   |      | $ | 50,657  |  
|                                                                             |  |                              |        |   |      |   |         |  

See accompanying notes to condensed financial statements.



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PAIN THERAPEUTICS, INC.

Notes to Condensed Financial Statements

(Unaudited)

Note 1. General

We are a biopharmaceutical company that develops novel drugs. Our lead drug candidate is called REMOXY. REMOXY is a
strong painkiller with a unique formulation designed to reduce potential risks of unintended use. REMOXY and three other abuse-resistant painkillers are being developed pursuant to our collaboration and license agreements with King Pharmaceuticals,
Inc., or the King Agreements.

We are also developing novel drug candidates in the area of hematology and
oncology. We have in pre-clinical development a drug candidate to treat hemophilia, a genetic disorder in which patients are unable to stop bleeding. We have in clinical development a monoclonal antibody to treat metastatic melanoma, a deadly form
of skin cancer.

Although we were profitable in the past based on program fee revenue, milestone revenue and
interest income, in the course of our development activities, we have sustained significant cumulative operating losses. As we continue to incur losses, we may need additional financing and there are no assurances that additional financing will be
available on favorable terms, or at all.

We have prepared the accompanying unaudited condensed financial
statements of Pain Therapeutics, Inc. in accordance with generally accepted accounting principles for interim financial information and pursuant to the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, the financial statements
do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. In our opinion, all adjustments, consisting of normal recurring adjustments, considered necessary for a fair
presentation have been included. Operating results for the three months ended March 31, 2011 are not necessarily indicative of the results that may be expected for any other interim period or for the year 2011.

We have evaluated subsequent events through the date of the filing this Form 10-Q with the Securities and Exchange
Commission. No material subsequent events have occurred that require recognition or disclosure in these financial statements.

Note 2.
Significant Accounting Policies

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States
of America requires that management 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 amount of
revenue



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earned and expenses incurred during the reporting period. Actual results could differ from those estimates.

Revenue Recognition and Deferred Program Fee Revenue

Revenue is recognized when there is persuasive evidence that an arrangement exists, delivery has occurred, the price is
fixed and determinable, and collection is reasonably assured.

We recognize program fee revenue, collaboration
revenue and milestone revenue in connection with the King Agreements. Program fee revenue is derived from program fee payments, including the upfront $150.0 million payment we received in 2005 and the $5.0 million payment we received in 2010. These
payments are recognized from receipt ratably over our estimate of the development period through the fourth of four drug candidates expected to be developed. We currently estimate the development period for all four drug candidates to end by
September 30, 2016. We periodically review the estimated development period and change it if appropriate based upon our latest expectations. Deferred program fee revenue represents the amount of the upfront program fee payments that have not
yet been recognized as revenue.

Collaboration revenue from reimbursement of development expenses are
generally recognized after expenses have been incurred and when King has completed its review of the expenses invoiced to them.

We recognize milestone payments as revenue when we achieve the underlying developmental milestone as the milestone payments are not dependent upon any other future activities or achievement of any other
future milestones and the achievement of each of the developmental milestones were substantively at risk and contingent at the effective date of the collaboration. Substantial effort is involved in achieving each of the developmental milestones.
These milestones represent the culmination of discrete earnings processes and the amount of each milestone payment is reasonable in relation with the level of effort associated with the achievement of the milestone. Each milestone payment is
non-refundable and non-creditable when made. The ongoing research and development services we provide are priced at fair value based upon the reimbursement of expenses we incur.

Cash, Cash Equivalents and Concentration of Credit Risk

We consider all highly liquid financial instruments with original maturities of three months or less to be cash equivalents. Cash and cash equivalents consist of cash maintained at two financial
institutions and in money market funds. We believe the financial risks associated with these instruments are minimal. We have not experienced material losses from our investments in these securities.

Marketable Securities and Fair Value Measurements

We invest in interest-bearing marketable securities, generally consisting of corporate and government securities. We may elect to sell these investments before they mature. Therefore, we hold these
investments as available for sale and include these investments in our balance sheets as current assets, even though the contractual maturity of a particular investment may be beyond



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one year. We report our marketable securities at fair value, which may include unrealized gains and losses. Our unrealized gains and losses on investments are recorded as a separate component of
stockholders equity as accumulated other comprehensive income or loss. We recognize all realized gains and losses on sales of our marketable securities in interest income in the accompanying statement of operations on a specific identification
basis. Our marketable securities are maintained at two financial institutions and are governed by our investment policy as approved by our Board of Directors.

To date we have not recorded any impairment charges on marketable securities related to other-than-temporary declines in market value. We would recognize an impairment charge when the decline in the
estimated fair value of a marketable security below the amortized cost is determined to be other-than-temporary. We consider various factors in determining whether to recognize an impairment charge, including the duration of time and the severity to
which the fair value has been less than our amortized cost, any adverse changes in the investees financial condition and our intent to sell or whether it is more likely than not that we would be required to sell the marketable security before
its anticipated recovery.

We measure our cash equivalents and marketable securities at fair value on a
recurring basis and have significant observable inputs where there are identical or comparable assets in the market to use in establishing our fair value measurements. We use significant observable inputs that include but are not limited to
benchmark yields, reported trades, broker/dealer quotes and issuer spreads. We consider available information regarding our cash, cash equivalents, money market funds and US government obligations to be Level 1 inputs. Generally, the types of
instruments we invest in are not traded on a market such as the NASDAQ Global Market, which we would consider to be Level 1 inputs. We generally consider available information regarding our other marketable securities to be Level 2 inputs. We do not
have any investments that would require inputs considered to be Level 3. We use the bid price to establish fair value.

Stock-based
Compensation

We recognize expense in the statement of operations for the fair value of all
share-based payments, including grants of employee stock options and other share based awards. For stock options, we use the Black-Scholes option valuation model and the single-option award approach and straight-line attribution method. Using this
approach, the compensation cost is amortized on a straight-line basis over the vesting period of each respective stock option, generally four years. We estimate forfeitures and adjust this estimate periodically based on the extent to which future
actual forfeitures differ, or are expected to differ, from such estimates.

We have granted share-based awards
that vest upon achievement of certain performance criteria, or Performance Awards. The value of these awards is the product of the number of shares of our common stock to be issued under the award multiplied by the fair market value of a share of
our common stock on the date of grant. These awards include future performance conditions. We estimate an implicit service period for achieving these performance conditions. Performance Awards vest and common stock is issued on achieving performance
conditions. We recognize stock-based compensation expense for Performance Awards when we conclude that achieving a performance condition is probable. We periodically review and update as appropriate our estimates of the implicit service periods and
the likelihood of achieving the performance conditions.



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Net Loss per Share

Basic net loss per share is computed on the basis of the weighted-average number of common shares outstanding for the
reporting period. Diluted net loss per share is computed on the basis of the weighted-average number of common shares outstanding plus dilutive potential common shares outstanding using the treasury-stock method. Potential dilutive common shares
consist of outstanding stock options, restricted stock units and warrants.

The numerators and denominators in
the calculation of basic and diluted net loss per share were as follows (in thousands except per share data):



|                                                                             |  |                             |        |  |      |   |         | 
|---------------------------------------------------------------------------- |  | --------------------------- | ------ |  | ---- | - | ------- | 
|                                                                             |  | Three Months EndedMarch 31, |       
|                                                                             |  | 2011                        |        |  | 2010 |  
|Numerators:                                                                  |  |                             |        |  |      |   |         | 
|Net loss                                                                     |  | $                           | (207)  |  |      | $ | (1,020) | 
|                                                                             |  |                            
|Denominators:                                                                |  |                             |        |  |      |   |         | 
|Weighted average shares used to compute basic and diluted net loss per share |  |                             | 43,124 |  |      |   | 42,410  | 
|                                                                             |  |                             |        |  |      |   |         | 
|                                                                             |  |                            
|Basic and diluted net loss per share                                         |  | $                           | (0.00) |  |      | $ | (0.02)  | 
|                                                                             |  |                             |        |  |      |   |         | 

Options to purchase 3.7 million and 10.4 million common shares were excluded from
the calculation of diluted loss per share for the three months ended March 31, 2011 and 2010 because the effect of including these shares in this calculation would be anti-dilutive.

Income Taxes

We make estimates and judgments in
determining the need for a provision for income taxes, including the estimation of our taxable income or loss for each full fiscal year. We have accumulated significant deferred tax assets. Deferred income taxes reflect the tax effects of net
operating loss and tax credit carryovers and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Realization of certain deferred tax assets is
dependent upon future earnings. We are uncertain about the timing and amount of any future earnings. Accordingly, we offset these net deferred tax assets with a valuation allowance. We may in the future determine that more of our deferred tax assets
will likely be realized, in which case we will reduce our valuation allowance in the quarter in which such determination is made. If the valuation allowance is reduced, we may recognize a benefit from income taxes in our statement of operations in
that period. We classify interest recognized pursuant to our deferred tax assets as interest expense, when appropriate.



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Note 3. Cash, Cash Equivalents and Marketable Securities

The following tables summarize our cash, cash equivalents and available-for-sale marketable securities as of
March 31, 2011 and December 31, 2010 (in thousands):



|                            |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|--------------------------- |  | ------------------------------------------------ | ------ |  | --------------- | - | --- | ---------------- |  | - | ------------------- |  |  | --------------- | ------ |  | ----------- | - | --- |  |  | - | ------ | 
|                            |  | Cash, Cash Equivalents and Marketable Securities |       
|                            |  | AmortizedCost                                    |        |  | UnrealizedGains |   |     | UnrealizedLosses |  |   | EstimatedFair Value |  |  | AccruedInterest |        |  | Total Value |  
|March 31, 2011              |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|Cash and cash equivalents   |  | $                                                | 14,842 |  |                 | $ | 2   |                  |  | $ | -                   |  |  | $               | 14,844 |  |             | $ | -   |  |  | $ | 14,844 | 
|Money market securities     |  |                                                  | 40,050 |  |                 |   | -   |                  |  |   | -                   |  |  |                 | 40,050 |  |             |   | -   |  |  |   | 40,050 | 
|Corporate securities        |  |                                                  | 32,441 |  |                 |   | 466 |                  |  |   | -                   |  |  |                 | 32,907 |  |             |   | 498 |  |  |   | 33,405 | 
|Certificates of deposit     |  |                                                  | 10,132 |  |                 |   | -   |                  |  |   | -                   |  |  |                 | 10,132 |  |             |   | 46  |  |  |   | 10,178 | 
|                            |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|                            |  | $                                                | 97,465 |  |                 | $ | 468 |                  |  | $ | -                   |  |  | $               | 97,933 |  |             | $ | 544 |  |  | $ | 98,477 | 
|                            |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|Reported as:                |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|Cash and cash equivalents   |  | $                                                | 54,892 |  |                 | $ | 2   |                  |  | $ | -                   |  |  | $               | 54,894 |  |             | $ | -   |  |  | $ | 54,894 | 
|Short term investments      |  |                                                  | 42,573 |  |                 |   | 466 |                  |  |   | -                   |  |  |                 | 43,039 |  |             |   | 544 |  |  |   | 43,583 | 
|                            |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|                            |  | $                                                | 97,465 |  |                 | $ | 468 |                  |  | $ | -                   |  |  | $               | 97,933 |  |             | $ | 544 |  |  | $ | 98,477 | 
|                            |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|Maturities:                 |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|Matures in one year or less |  | $                                                | 80,235 |  |                 | $ | 127 |                  |  | $ | -                   |  |  | $               | 80,362 |  |             | $ | 331 |  |  | $ | 80,693 | 
|Matures one to three years  |  |                                                  | 17,230 |  |                 |   | 341 |                  |  |   | -                   |  |  |                 | 17,571 |  |             |   | 213 |  |  |   | 17,784 | 
|                            |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|                            |  | $                                                | 97,465 |  |                 | $ | 468 |                  |  | $ | -                   |  |  | $               | 97,933 |  |             | $ | 544 |  |  | $ | 98,477 | 
|                            |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|December 31, 2010           |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|Cash and cash equivalents   |  | $                                                | 4,798  |  |                 | $ | -   |                  |  | $ | -                   |  |  | $               | 4,798  |  |             | $ | -   |  |  | $ | 4,798  | 
|Certificates of deposit     |  |                                                  | 10,131 |  |                 |   | -   |                  |  |   | -                   |  |  |                 | 10,131 |  |             |   | 31  |  |  |   | 10,162 | 
|Corporate securities        |  |                                                  | 75,063 |  |                 |   | 525 |                  |  |   | -                   |  |  |                 | 75,588 |  |             |   | 678 |  |  |   | 76,266 | 
|                            |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|                            |  | $                                                | 89,992 |  |                 | $ | 525 |                  |  | $ | -                   |  |  | $               | 90,517 |  |             | $ | 709 |  |  | $ | 91,226 | 
|                            |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|Reported as:                |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|Cash and cash equivalents   |  | $                                                | 4,798  |  |                 | $ | -   |                  |  | $ | -                   |  |  | $               | 4,798  |  |             | $ | -   |  |  | $ | 4,798  | 
|Marketable securities       |  |                                                  | 85,194 |  |                 |   | 525 |                  |  |   | -                   |  |  |                 | 85,719 |  |             |   | 709 |  |  |   | 86,428 | 
|                            |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|                            |  | $                                                | 89,992 |  |                 | $ | 525 |                  |  | $ | -                   |  |  | $               | 90,517 |  |             | $ | 709 |  |  | $ | 91,226 | 
|                            |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|Maturities:                 |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|Matures in one year or less |  | $                                                | 67,557 |  |                 | $ | 106 |                  |  | $ | -                   |  |  | $               | 67,663 |  |             |   | 433 |  |  | $ | 68,096 | 
|Matures one to three years  |  |                                                  | 22,435 |  |                 |   | 419 |                  |  |   | -                   |  |  |                 | 22,854 |  |             |   | 276 |  |  |   | 23,130 | 
|                            |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 
|                            |  | $                                                | 89,992 |  |                 | $ | 525 |                  |  | $ | -                   |  |  | $               | 90,517 |  |             | $ | 709 |  |  | $ | 91,226 | 
|                            |  |                                                  |        |  |                 |   |     |                  |  |   |                     |  |  |                 |        |  |             |   |     |  |  |   |        | 

We did not realize any gains or losses on our investments in securities during the first
quarter of 2011 or 2010. To date we have not recorded any impairment charges on marketable securities related to other-than-temporary declines in market value.



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The following table presents our assets measured at fair value on a
recurring basis (in thousands):



|                          |  |         |        |  |         |   |        |         |  |   |       |  |  |   |        | 
|------------------------- |  | ------- | ------ |  | ------- | - | ------ | ------- |  | - | ----- |  |  | - | ------ | 
|                          |  | Level 1 |        |  | Level 2 |   |        | Level 3 |  |   | Total | 
|March 31, 2011            |  |         |        |  |         |   |        |         |  |   |       |  |  |   |        | 
|Cash and cash equivalents |  | $       | 14,844 |  |         | $ | -      |         |  | $ | -     |  |  | $ | 14,844 | 
|Money market securities   |  |         | 40,050 |  |         |   | -      |         |  |   | -     |  |  |   | 40,050 | 
|Corporate securities      |  |         | -      |  |         |   | 33,405 |         |  |   | -     |  |  |   | 33,405 | 
|Certificates of deposit   |  |         | 10,178 |  |         |   | -      |         |  |   | -     |  |  |   | 10,178 | 
|                          |  |         |        |  |         |   |        |         |  |   |       |  |  |   |        | 
|                          |  | $       | 65,072 |  |         | $ | 33,405 |         |  | $ | -     |  |  | $ | 98,477 | 
|                          |  |         |        |  |         |   |        |         |  |   |       |  |  |   |        | 
|                          |  |         |        | 
|                          |  | Level 1 |        |  | Level 2 |   |        | Level 3 |  |   | Total | 
|December 31, 2010         |  |         |        |  |         |   |        |         |  |   |       |  |  |   |        | 
|Cash and cash equivalents |  | $       | 4,798  |  |         | $ | -      |         |  | $ | -     |  |  | $ | 4,798  | 
|Corporate securities      |  |         | -      |  |         |   | 76,266 |         |  |   | -     |  |  |   | 76,266 | 
|Certificates of deposit   |  |         | 10,162 |  |         |   | -      |         |  |   | -     |  |  |   | 10,162 | 
|                          |  |         |        |  |         |   |        |         |  |   |       |  |  |   |        | 
|                          |  | $       | 14,960 |  |         | $ | 76,266 |         |  | $ | -     |  |  | $ | 91,226 | 
|                          |  |         |        |  |         |   |        |         |  |   |       |  |  |   |        | 

Note 4. Comprehensive Loss

Comprehensive loss is the sum of net loss and other comprehensive income (loss), as follows (in thousands):



|                                  |  |                              |      |   |      |   |        |  
|--------------------------------- |  | ---------------------------- | ---- | - | ---- | - | ------ | -
|                                  |  | Three Months Ended March 31, |     
|                                  |  | 2011                         |      |   | 2010 |  
|Net loss                          |  | $                            | (207 | ) |      | $ | (1,020 | )
|Other comprehensive income (loss) |  |                              | (57  | ) |      |   | 317    |  
|                                  |  |                              |      |   |      |   |        |  
|Comprehensive loss                |  | $                            | (264 | ) |      | $ | (703   | )
|                                  |  |                              |      |   |      |   |        |  

Other comprehensive income (loss) consists of net unrealized holding gains and losses on available-for-sale
securities.

Note 5. Stock-Based Compensation

Our non-cash stock-based compensation expense is as follows (in thousands):



|                           |  |                              |       |  |      |   |       | 
|-------------------------- |  | ---------------------------- | ----- |  | ---- | - | ----- | 
|                           |  | Three Months Ended March 31, |      
|                           |  | 2011                         |       |  | 2010 |  
|Research and development   |  | $                            | 732   |  |      | $ | 842   | 
|General and administrative |  |                              | 571   |  |      |   | 576   | 
|                           |  |                              |       |  |      |   |       | 
|                           |  | $                            | 1,303 |  |      | $ | 1,418 | 
|                           |  |                              |       |  |      |   |       | 

Note 6. Income Taxes

We did not provide for income taxes in 2011 because we have projected a tax loss for the full year 2011. Interest expense and penalties related to unrecognized tax benefits were immaterial for 2011 and
2010.



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Note 7. Commitments

We conduct our product research and development programs through a combination of internal and collaborative programs
that include, among others, arrangements with universities, contract research organizations and clinical research sites. We have contractual arrangements with these organizations, however these contracts are cancelable on thirty days notice and our
obligations under these contracts are largely based on services performed.

We currently lease approximately
36,400 square feet of office space pursuant to non-cancelable operating leases that will expire in 2012. Future minimum lease payments are as follows for the years ended December 31, (in thousands):



|                              |  |      |     |  |      |   |     |       |  |   |       |  |  | 
|----------------------------- |  | ---- | --- |  | ---- | - | --- | ----- |  | - | ----- |  |  | 
|                              |  | 2011 |     |  | 2012 |   |     | Total |  |   |      
|Future minimum lease payments |  | $    | 667 |  |      | $ | 373 |       |  | $ | 1,040 |  | 
|                              |  |      |     |  |     

Note 8.Recently Issued Accounting Pronouncements

We reviewed recently issued accounting pronouncements and have adopted or plan to adopt those that are applicable to us.
We do not expect the adoption of these pronouncements to have a material impact on our financial position, results of operations or cash flows.

Item 2.Managements
Discussion and Analysis of Financial Condition and Results of Operations

This discussion and analysis
should be read in conjunction with our financial statements and accompanying notes included elsewhere in this report. Operating results are not necessarily indicative of results that may occur in future periods.

This document contains forward-looking statements, that are based upon current expectations, within the meaning of the
Private Securities Reform Act of 1995. We intend that such statements be protected by the safe harbor created thereby. Forward-looking statements involve risks and uncertainties and our actual results and the timing of events may differ
significantly from the results discussed in the forward-looking statements. Examples of such forward-looking statements include, but are not limited to, statements about:



| |  |  | the New Drug Application, or NDA, for REMOXY® (controlled-release oxycodone) with the U.S. Food and Drug Administration, or FDA, by King
Pharmaceutical, Inc., or King, a wholly-owned subsidiary of Pfizer, Inc., or Pfizer;
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  | royalty, milestone or collaboration revenue we may receive from King and other payments we may receive from our collaboration agreements;
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------

| |  |  | the duration of the development period for expected drug candidates;
| | - |  | --------------------------------------------------------------------

| |  |  | expansion of our potential product line, including the formulation of additional dosage forms of our drug candidates;
| | - |  | ---------------------------------------------------------------------------------------------------------------------

| |  |  | operating losses and anticipated operating and capital expenditures;
| | - |  | --------------------------------------------------------------------

| |  |  | uses of proceeds from our securities offerings;
| | - |  | -----------------------------------------------

| |  |  | the potential benefits of our drug candidates;
| | - |  | ----------------------------------------------



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| |  |  | the sufficiency of materials required for the clinical development of our drug candidates;
| | - |  | ------------------------------------------------------------------------------------------

| |  |  | the size of potential markets for our products;
| | - |  | -----------------------------------------------

| |  |  | the utility of protection of our intellectual property;
| | - |  | -------------------------------------------------------

| |  |  | expected future sources of revenue and capital and increasing cash needs;
| | - |  | -------------------------------------------------------------------------

| |  |  | potential competitors or competitive products;
| | - |  | ----------------------------------------------

| |  |  | market acceptance of our drug candidates and potential drug candidates;
| | - |  | -----------------------------------------------------------------------

| |  |  | expenses increasing or fluctuations in our operating results;
| | - |  | -------------------------------------------------------------

| |  |  | expectations regarding trade secrets, technological innovations, licensing agreements and outsourcing of certain business functions;
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------

| |  |  | anticipated hiring and development of our internal systems and infrastructure;
| | - |  | ------------------------------------------------------------------------------

| |  |  | the sufficiency of our current resources to fund our operations over the next twelve months;
| | - |  | --------------------------------------------------------------------------------------------

| |  |  | plans with respect to our headquarters relocation to Austin, Texas;
| | - |  | -------------------------------------------------------------------

| |  |  | assumptions and estimates used for our disclosures regarding stock-based compensation; and
| | - |  | ------------------------------------------------------------------------------------------

| |  |  | estimates concerning the realization of deferred tax assets.
| | - |  | ------------------------------------------------------------

Such forward-looking statements involve risks and uncertainties, including, but not limited to, those risks and uncertainties relating
to:



| |  |  | difficulties or delays in the potential regulatory approval of the REMOXY NDA, including the potential request by the FDA of additional data which
may require an extended period of time to obtain and submit, that could significantly delay or prevent such approval;
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  | the successful development and commercialization of REMOXY and other drug candidates pursuant to our collaboration and license agreements with King,
or the King Agreements, and development of other drug candidates pursuant to our other collaboration agreements, and the continuation of such agreements;
| | - |  | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  | difficulties or delays in development, testing, clinical trials (including patient enrollment), regulatory approval, production and
commercialization of our drug candidates;
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  | unexpected adverse side effects or inadequate therapeutic efficacy of our drug candidates that could slow or prevent product approval (including the
risk that current and past results of clinical trials are not indicative of future results of clinical trials) or potential post-approval market acceptance;
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  | the uncertainty of protection of our intellectual property rights or trade secrets;
| | - |  | -----------------------------------------------------------------------------------

| |  |  | potential infringement of the intellectual property rights of third parties;
| | - |  | ----------------------------------------------------------------------------

| |  |  | pursuing in-license and acquisition opportunities;
| | - |  | --------------------------------------------------

| |  |  | maintenance or third party funding of our collaboration and license agreements;
| | - |  | -------------------------------------------------------------------------------

| |  |  | hiring and retaining personnel; and
| | - |  | -----------------------------------

| |  |  | our financial position and our ability to obtain additional financing if necessary.
| | - |  | -----------------------------------------------------------------------------------

In addition, such statements are subject to the risks and uncertainties discussed in the Risk Factors section
and elsewhere in this document.

This discussion and analysis should be read in conjunction with our financial
statements and accompanying notes included elsewhere in this report. Operating results are not necessarily indicative of results that may occur in future periods.



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Overview

We are a biopharmaceutical company that develops novel drugs. Our lead drug candidate is called REMOXY. REMOXY is a strong painkiller with a unique formulation designed to reduce potential risks of
unintended use. REMOXY and three other abuse-resistant painkillers are being developed pursuant to the King Agreements.

Pfizer acquired King in early 2011. We expect REMOXY will be commercialized within Pfizers primary care unit. We believe Pfizers acquisition of King may facilitate REMOXYs commercial
success if this drug is approved.

We and King jointly managed a Phase III clinical program and NDA submission
for REMOXY. In mid-2008, the FDA accepted our NDA for REMOXY with Priority Review. In December 2008, we received from the FDA a Complete Response Letter for the NDA for REMOXY. In this Complete Response Letter, the FDA indicated additional
non-clinical data was required to support the approval of REMOXY. The FDA has not requested or recommended additional clinical efficacy studies prior to approval. In 2009, King assumed sole responsibility for the regulatory approval of REMOXY. This
shift of responsibility did not change any economic term of the King Agreements. In December 2010, King resubmitted the REMOXY NDA. In January 2011, we announced that the FDA had accepted the resubmission of the REMOXY NDA.

In January 2011, we announced that the FDA had accepted our IND for abuse-resistant oxymorphone and that we had received
a $5.0 million milestone payment for this milestone.

In April 2011, we announced top-line results of an abuse
liability study with REMOXY and that the article entitled The Abuse Potential of REMOXY®, an
Extended-Release Formulation of Oxycodone, Compared with Immediate- and Extended-Release Oxycodone was published in Pain Medicine, the Official Journal of the American Academy of Pain Medicine. In the study, REMOXY met all prospectively
defined primary endpoints.

We are also developing a pipeline of novel drug candidates in the area of oncology
and hematology. We hold all commercial rights to our pipeline of drug candidates in oncology and hematology.

We are developing a novel drug candidate called PTI-188 to treat metastatic melanoma, a deadly form of skin cancer.
PTI-188 is a monoclonal antibody linked to a radioisotope, intended to deliver doses of radiation lethal to melanoma tumors without harming normal tissue.

We have a gene transfer program, initially developed at Stanford University, aimed at correcting an underlying genetic defect in patients with hemophilia, a genetic disorder in which patients are unable
to stop bleeding. We have licensed exclusive worldwide commercial rights to the technology used in this program from Poetic Genetics, LLC.

All of our program fee, collaboration and milestone revenue is recognized pursuant to the King Agreements, including:



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|                                                                      |  |               |  |                    |     | 
|--------------------------------------------------------------------- |  | ------------- |  | ------------------ | --- | 
|Description                                                           |  | Year Received |  | AmountReceived(mm) |    
|Upfront program fee payment                                           |  | 2005          |  | $                  | 150 | 
|Program fee payment related to an amendment to the strategic alliance |  | 2010          |  | $                  | 5   | 
|Milestone payments related to:                                        |  |               |  |                    |     | 
|acceptance by the FDA of the NDA for REMOXY                           |  | 2008          |  | $                  | 15  | 
|acceptance by the FDA of the IND for abuse-resistant oxymorphone      |  | 2011          |  | $                  | 5   | 
|acceptance by the FDA of the IND for abuse-resistant hydrocodone      |  | 2008          |  | $                  | 5   | 
|acceptance by the FDA of the IND for abuse-resistant hydromorphone    |  | 2006          |  | $                  | 5   | 

We will receive a
$15.0 million cash milestone payment from King upon regulatory approval of REMOXY in the United States. We could also receive up to $105.0 million in additional milestone payments in the course of clinical development of the other abuse-resistant
opioid painkillers. Subject to certain limitations, King is also obligated to fund development expenses incurred by us pursuant to the King Agreements, which result in collaboration revenue. King is obligated to fund the commercialization expenses
of, and has the exclusive right to market and sell, drugs developed in connection with the King Agreements. The royalty rate for net sales of REMOXY and the other three abuse-resistant product candidates covered by the King Agreements in the United
States is 20%, except as to the first $1.0 billion in cumulative net sales in the United States, for which the royalty is set at 15%. The royalty rate for net sales of products covered by the King Agreements outside the United States is 10% on all
of net sales.

Although we were profitable in 2006, 2007 and 2008 based on payments received under the King
Agreements and interest income, we have yet to generate any revenues from product sales. Through March 31, 2011, we have recorded an accumulated deficit of approximately $129.8 million. These losses have resulted principally from costs incurred
in connection with research and development activities, salaries and other personnel-related costs and general corporate expenses. Research and development activities include costs of preclinical and clinical trials as well as clinical supplies
associated with our drug candidates. Salaries and other personnel-related costs include non-cash stock-based compensation associated with options and other equity awards granted to employees and non-employees. Our operating results may fluctuate
substantially from period to period as a result of the timing and enrollment rates of clinical trials for our drug candidates and our need for clinical supplies.

We expect to continue to use significant cash resources in our operations for the next several years. Our cash
requirements for operating activities and capital expenditures may increase substantially in the future as we:



| |  |  | continue to conduct preclinical and clinical trials for our drug candidates;
| | - |  | ----------------------------------------------------------------------------

| |  |  | seek regulatory approvals for our drug candidates;
| | - |  | --------------------------------------------------

| |  |  | develop, formulate, manufacture and commercialize our drug candidates;
| | - |  | ----------------------------------------------------------------------

| |  |  | implement additional internal systems and develop new infrastructure;
| | - |  | ---------------------------------------------------------------------

| |  |  | acquire or in-license additional products or technologies, or expand the use of our technology;
| | - |  | -----------------------------------------------------------------------------------------------

| |  |  | maintain, defend and expand the scope of our intellectual property; and
| | - |  | -----------------------------------------------------------------------



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##### Table of Contents

| |  |  | hire additional personnel.
| | - |  | --------------------------

Product revenue will depend on receiving regulatory approvals for, and successfully marketing, our drug candidates. If development efforts result in regulatory approval and successful commercialization of
our drug candidates, we will generate revenue from direct sales of our drugs and/or, if we license our drugs to future collaborators, from the receipt of license fees and royalties from sales of licensed products. We conduct our research and
development programs through a combination of internal and collaborative programs. We rely on arrangements with universities, our collaborators, contract research organizations and clinical research sites for a significant portion of our product
development efforts.

We focus substantially all our research and development efforts on the research and
development of drugs for the treatment of pain, metastatic melanoma and hemophilia. The following table summarizes expenses by category for research and development efforts (in thousands):



|                      |  |                              |       |  |      |   |       | 
|--------------------- |  | ---------------------------- | ----- |  | ---- | - | ----- | 
|                      |  | Three Months Ended March 31, |      
|                      |  | 2011                         |       |  | 2010 |  
|Compensation          |  | $                            | 1,568 |  |      | $ | 1,712 | 
|Contractor fees(1)    |  |                              | 254   |  |      |   | 999   | 
|Supplies(2)           |  |                              | 19    |  |      |   | 25    | 
|Other common costs(3) |  |                              | 337   |  |      |   | 391   | 
|                      |  |                              |       |  |      |   |       | 
|                      |  | $                            | 2,178 |  |      | $ | 3,127 | 
|                      |  |                              |       |  |      |   |       | 



| | (1) | Contractor fees generally include expenses for preclinical studies and clinical trials.
| | --- | ---------------------------------------------------------------------------------------

| | (2) | Supplies generally include costs for formulation and manufacturing activities.
| | --- | ------------------------------------------------------------------------------

| | (3) | Other generally includes the allocation of common costs such as facilities.
| | --- | ---------------------------------------------------------------------------

Our technology has been applied across certain of our portfolio of drug candidates. Data, know-how, personnel, clinical
results, research results and other matters related to the research and development of any one of our drug candidates also relate to, and further the development of, our other drug candidates. For example, we expect that results of non-clinical
studies, such as pharmacokinetics, toxicology and other studies, regarding certain components of our drug candidate REMOXY to be applicable to the other potential abuse-resistant drug candidates since all such potential drug candidates are expected
to utilize such components. As a result, costs allocated to a specific drug candidate may not necessarily reflect the actual costs surrounding research and development of that drug candidate due to cross application of the foregoing.

We spent approximately $0.1 million in the first quarter of 2011 and $1.3 million in the first quarter of 2010 on
PTI-188, primarily on compensation. We spent approximately $0.3 million in the first quarter of 2011 and $0.2 million in the first quarter of 2010 on hemophilia and other projects, primarily on compensation.

Estimating the dates of completion of clinical development, and the costs to complete development, of our drug candidates
would be highly speculative, subjective and potentially misleading. Pharmaceutical products take a significant amount of time to research, develop and commercialize. The clinical trial portion of the development of a new drug alone usually spans
several years. We expect to reassess our future research and development plans based on our



16



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review of data we receive from our current research and development activities. The cost and pace of our future research and development activities are linked and subject to change.

We intend to relocate our principal place of business to Austin, Texas. In order to minimize potential disruptions
to our on-going operations, this relocation will take place gradually now through the end of 2011. Our intentions are to shift our permanent headquarters and the direction, control, and coordination of all of our operations, from California to
Texas.

Critical Accounting Policies

The preparation of our financial statements in accordance with United States generally accepted accounting principles
requires us to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and interest income in our financial statements and accompanying notes. We evaluate our estimates on an ongoing basis,
including those estimates related to agreements, research collaborations and investments. We base our estimates on historical experience and various other assumptions that we believe to be reasonable under the circumstances, the results of which
form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ from these estimates under different assumptions or conditions. The following items
in our financial statements require significant estimates and judgments:



| |  |  | Expenses for clinical trials. We incur expenses for clinical trials from the planning phase through patient enrollment to reporting of the
underlying data. We estimate expenses incurred for clinical trials that are in process based on patient enrollment and based on clinical data collection and management. Costs that are associated with patient enrollment are recognized as each patient
in the clinical trial completes enrollment. Estimated clinical trial costs related to enrollment can vary based on numerous factors, including expected number of patients in trials, the number of patients that do not complete participation in a
trial, and when a patient drops out of a trial. Information about patient enrollment can become available significantly after we report our expenses for clinical trials, in which case we would change our estimate of the remaining cost of a trial.
Costs that are based on clinical data collection and management are recognized based on estimates of unbilled goods and services received. In the event of early termination of a clinical trial, we would accrue an amount based on estimates of the
remaining non-cancelable obligations associated with winding down the clinical trial.
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | Stock-based compensation. We recognize expense in the statement of operations for the fair value of all share-based payments to employees and
directors, including grants of employee stock options and other share based awards. For stock options, we use the Black-Scholes option valuation model and the single-option award approach and straight-line attribution method. Using this approach,
the compensation cost is amortized on a straight-line basis over the vesting period of each respective stock option, generally four years. We estimate forfeitures and adjust this estimate periodically based on the extent to which future actual
forfeitures differ, or are expected to differ, from such estimates.
| | - |  | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

We have granted
share-based awards that vest upon achievement of certain performance criteria, or Performance Awards. The value of these awards is the product of the number of shares of our common stock to be issued under the award multiplied by the fair market



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value of a share of our common stock on the date of grant. These awards include future performance conditions. We estimate an implicit service period for achieving these performance conditions.
Performance Awards vest and common stock is issued on achieving performance conditions. We recognize stock-based compensation expense for Performance Awards when we conclude that achieving a performance condition is probable. We periodically review
and update as appropriate our estimates of the implicit service periods and the likelihood of achieving the performance conditions.



| |  |  | Revenue recognition and deferred program fee revenue. We recognize program fee revenue, collaboration revenue and milestone revenue in
connection with the King Agreements. Program fee revenue is derived from the $150.0 million paid to us at the inception of these agreements and the $5.0 million paid to us in July 2010 in connection with an amendment to these agreements. These
payments are recognized from receipt ratably over our estimate of the development period for the fourth of four drug candidates expected to be developed. We currently estimate the development period for all four expected drug candidates to end in
the quarter ended September 30, 2016. We review the estimated development period on a quarterly basis and change it if appropriate based upon our latest expectations. Collaboration revenue from reimbursement of development expenses pursuant to
the King Agreements are generally recognized when King has completed its review of the expenses invoiced to them. King is obligated to pay us milestone payments contingent upon the achievement of certain substantive events in the development of
REMOXY and the other opioid painkillers under the King Agreements. We recognize milestone payments as revenue when we achieve the underlying developmental milestone as the milestone payments are not dependent upon any other future activities or
achievement of any other future milestones and the achievement of each of the developmental milestones were substantively at risk and contingent at the effective date of the collaboration. Substantial effort is involved in achieving each of the
developmental milestones. These milestones represent the culmination of discrete earnings processes and the amount of each milestone payment is reasonable in relation with the level of effort associated with the achievement of the milestone. Each
milestone payment is non-refundable and non-creditable when made. The ongoing research and development services we provide are priced at fair value based upon the reimbursement of expenses we incur.
| | - |  | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | Taxes. We make estimates and judgments in determining the need for a provision for income taxes, including the estimation of our taxable
income or loss for each full fiscal year. We have accumulated significant deferred tax assets. Deferred income taxes reflect the tax effects of net operating loss and tax credit carryovers and temporary differences between the carrying amounts of
assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Realization of certain deferred tax assets is dependent upon future earnings, if any. We are uncertain as to the timing and amount of any future
earnings. Accordingly, we offset these net deferred tax assets with a valuation allowance. We may in the future determine that more of our deferred tax assets will likely be realized, in which case we will reduce our valuation allowance in the
quarter in which such determination is made. If the valuation allowance is reduced, we may recognize a benefit from income taxes in our statement of operations in that period. We classify interest recognized in connection with our tax positions as
interest expense, when appropriate.
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



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Results of Operations

Three months ended March 31, 2011 and 2010

Revenue  Program fee
revenue

Program fee revenue recognized from the program fees we received under the King Agreements
increased to $2.7 million for the first quarter of 2011 from $2.5 million for the first quarter of 2010. This increase resulted from our June 2010 amendment to these agreements.

Revenue - Collaboration revenue

Collaboration revenue
from reimbursement of our development expenses incurred under the King Agreements decreased to $0.5 million for the first quarter of 2011 from $0.7 million for the first quarter of 2010. These reimbursements decreased primarily because the related
expenses were lower from period to period.

We expect the amount and timing of collaboration revenue to
fluctuate in relation to the amount and timing of the underlying research and development expenses.

Research and Development Expense

Research and development expense consists primarily of costs of drug development work associated with our
drug candidates, including:



| |  |  | preclinical testing,
| | - |  | --------------------

| |  |  | clinical trials,
| | - |  | ----------------

| |  |  | clinical supplies and related formulation and design costs, and
| | - |  | ---------------------------------------------------------------

| |  |  | salaries and other personnel-related expenses.
| | - |  | ----------------------------------------------

Research and development expense decreased to $2.2 million in the first quarter of 2011 from $3.1 million in the first
quarter of 2010. The decrease was primarily due to decreases in clinical and development activities for metastatic melanoma, hemophilia and other projects. Research and development expenses included non-cash stock related compensation costs of $0.7
million in the first quarter of 2011 and $0.8 million in the first quarter of 2010.

We expect research and
development expenses to fluctuate over the next several years as we continue our development efforts. We expect our development efforts to result in our drug candidates progressing through various stages of clinical trials, including current and
potential clinical trials for our other abuse-resistant drug candidates, as well as further clinical development of our product candidates in metastatic melanoma and hemophilia. Our research and development expenses may fluctuate from period to
period due to the timing and scope of our development activities and the results of clinical trials and preclinical studies.



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General and Administrative Expense

General and administrative expenses consist primarily of compensation and other general corporate expenses. General and
administrative expenses were $1.5 million in each of the quarters ended March 31, 2011 and 2010, respectively. General and administrative expenses included non-cash stock related compensation costs of $0.6 million in each of the quarters ended
March 31, 2011 and 2010, respectively.

We expect general and administrative expenses to increase over
the next several years in connection with support of pre-commercialization and commercialization activities for our drug candidates. The increase may fluctuate from period to period due to the timing and scope of these activities and the results of
clinical trials and preclinical studies.

Interest Income

Interest income was $0.3 million in each of the quarters ended March 31, 2011 and 2010, respectively. We expect our
interest income to decrease in the future as we use cash to fund our operations.

Liquidity and Capital Resources

Since inception, we have financed our operations primarily through public and private stock offerings, payments received
under the King Agreements and interest earned on our investments. We intend to continue to use our capital resources to fund research and development activities, capital expenditures, working capital requirements and other general corporate
purposes. As of March 31, 2011, cash, cash equivalents and marketable securities were $98.5 million.

Net
cash provided by operating activities was $3.3 million for the first quarter of 2011 compared to net cash used in operating activities of $0.8 million for the first quarter of 2010. Cash provided by operating activities in the first quarter of 2011
included cash from liquidation of receivables at December 31, 2010, consisting of the $5.0 million milestone payment for the IND accepted by the FDA in December 2010 and the $2.1 million in tax credits awarded to us in 2010 under the federal
Qualifying Therapeutic Discovery Project Program.

Net cash provided by investing activities was $42.4 million
for the first quarter of 2011 and $14.7 million for the first quarter of 2010. Investing activities for both periods consisted primarily of the purchase and maturities of marketable securities. There were no significant purchases of property,
equipment or leasehold improvements in 2011 and 2010.

Net cash provided by financing activities was $4.4
million for the first quarter of 2011 and $1.0 for the first quarter of 2010. Cash from financing activities in 2011 and 2010 consisted primarily of proceeds from employee stock option exercises.

Realization of our other deferred tax assets is dependent on future earnings, if any. We are uncertain about the timing
and amount of any future earnings. Accordingly, we offset these net deferred tax assets with a valuation allowance. There is a high degree of uncertainty regarding



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the timing of future cash outflows associated with our liabilities related to uncertain tax positions. Our liability at March 31, 2011 related to our uncertain tax positions is immaterial.

In 2010, we were selected for an audit of our 2008 federal tax return. This audit was completed in early 2011
with no changes in any of our tax positions.

We currently lease approximately 36,700 square feet of general
office space in San Mateo, California and Austin, Texas pursuant to non-cancelable operating leases that will expire in 2012. We believe that our facilities are adequate and suitable for our current needs. Future minimum lease payments are as
follows for the years ended December 31, (in thousands):



|                              |  |      |     |  |      |   |     |       |  |   |       |  |  | 
|----------------------------- |  | ---- | --- |  | ---- | - | --- | ----- |  | - | ----- |  |  | 
|                              |  | 2011 |     |  | 2012 |   |     | Total |  |   |      
|                              |  |      |     |  |     
|Future minimum lease payments |  | $    | 667 |  |      | $ | 373 |       |  | $ | 1,040 |  | 
|                              |  |      |     |  |     

We have license agreements that require us to make milestone payments
upon the successful achievement of milestones, including clinical milestones. Our license agreements also require us to pay certain royalties to our licensors if we succeed in fully commercializing products under these license agreements. All of
these potential future payments are cancelable as of March 31, 2011. Our formulation agreement with Durect Corporation obligates us to make certain milestone payments upon achieving clinical milestones and regulatory milestones. King is
obligated to reimburse us for any of our milestone payments and royalty payments to Durect Corporation.

We
have an accumulated deficit of $129.8 million at March 31, 2011. We expect our cash requirements to be significant in the future. The amount and timing of our future cash requirements will depend on regulatory and market acceptance of our drug
candidates and the resources we devote to researching and developing, formulating, manufacturing, commercializing and supporting our products. We believe that our current resources should be sufficient to fund our operations for at least the next 12
months. We may seek additional future funding through public or private financing within this timeframe, if such funding is available and on terms acceptable to us.

Off-balance Sheet Arrangements

As of March 31, 2011,
we did not have any relationships with unconsolidated entities or financial partnerships, such as entities often referred to as structured finance or special purpose entities, which would have been established for the purpose of facilitating
off-balance sheet arrangements or other contractually narrow or limited purposes. In addition, we do not engage in trading activities involving non-exchange traded contracts. Therefore, we are not materially exposed to financing, liquidity, market
or credit risk that could arise if we had engaged in these relationships. We do not have relationships or transactions with persons or entities that derive benefits from their non-independent relationship with us or our related parties.

Item 3.Quantitative and Qualitative Disclosures About Market Risk

The primary objective of our cash investment activities is to preserve principal while at the same time maximizing the
income we receive from our investments without significantly increasing risk. Some of the securities that we invest in may be subject to market risk. This



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means that a change in prevailing interest rates may cause the principal amount of the investment to fluctuate. For example, if we hold a security that was issued with a fixed interest rate at
the then-prevailing rate and the interest rate later rises, the principal amount of our investment will probably decline. A hypothetical 50 basis point increase in interest rates reduces the fair value of our available-for-sale securities at
March 31, 2011 by approximately $0.3 million. To minimize this risk, we intend to maintain our portfolio of cash equivalents and marketable securities in a variety of securities, including commercial paper, government and non-government debt
securities and/or money market funds that invest in such securities. We have no holdings of derivative financial or commodity instruments.

As of March 31, 2011, our investments consisted of investments in corporate and government notes and obligations, certificates of deposits or in money market accounts and checking funds with variable
market rates of interest. We believe our credit risk is immaterial. We measure our cash equivalents and marketable securities at fair value on a recurring basis and have significant observable inputs where there are identical or comparable assets in
the market to use in establishing our fair value measurements. We use significant observable inputs that include but are not limited to benchmark yields, reported trades, broker/dealer quotes, and issuer spreads. Generally, the types of instruments
we invest in are not traded on a market such as the NASDAQ Global Market, which we would consider to be Level 1 inputs. We generally consider our inputs to be Level 1 and Level 2 inputs. We do not have any investments that would require inputs
considered to be Level 3. We use the bid price to establish fair value.

Item 4.Controls and
Procedures

Evaluation of disclosure controls and procedures.Our management evaluated, with
the participation of our Chief Executive Officer and our Chief Financial Officer, the effectiveness of our disclosure controls and procedures as of the end of the period covered by this Quarterly Report on Form 10-Q. Based on this evaluation, our
Chief Executive Officer and our Chief Financial Officer have concluded that our disclosure controls and procedures are effective to ensure that information we are required to disclose in reports that we file or submit under the Securities Exchange
Act of 1934 is recorded, processed, summarized and reported within the time periods specified in the Securities and Exchange Commission, or SEC, rules and forms and that such information is accumulated and communicated to management as appropriate
to allow timely decisions regarding required disclosures.

Changes in internal control over financial
reporting.There was no change in our internal control over financial reporting that occurred during the period covered by this Quarterly Report on Form 10-Q that has materially affected, or is reasonably likely to materially affect, our
internal control over financial reporting.



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PART II  OTHER INFORMATION

Item 1.Legal Proceedings

None.

Item 1A. Risk Factors

Our future operating results may vary substantially from anticipated
results due to a number of factors, many of which are beyond our control. The following discussion highlights some of these factors and the possible impact of these factors on future results of operations. You should carefully consider these factors
before making an investment decision. If any of the following factors actually occur, our business, financial condition or results of operations could be harmed. In that case, the price of our common stock could decline, and you could experience
losses on your investment in our common stock.

Clinical and Regulatory Risks

If we or our collaborators fail to obtain the necessary regulatory approvals, or if such approvals are limited, we and our
collaborators will not be allowed to commercialize our drug candidates, and we will not generate product revenues.

Satisfaction of all regulatory requirements for commercialization of a drug candidate typically takes many years, is dependent upon the type, complexity and novelty of the drug candidate, and requires the
expenditure of substantial resources for research and development. In December 2008, we received from the FDA a Complete Response Letter for the NDA for REMOXY. In this Complete Response Letter, the FDA indicated additional non-clinical data is
required to support the approval of REMOXY. The FDA has not requested or recommended additional clinical efficacy studies prior to approval. In March 2009, King assumed sole responsibility for the regulatory approval of REMOXY. In December 2010,
King resubmitted the NDA for REMOXY. While the FDA is not requiring additional clinical trials to support approval, there can be no assurance that the FDA will approve the NDA for REMOXY (even with the additional data provided by King) or that the
FDA will not require additional clinical or non-clinical data to be submitted. If the FDA were to require additional clinical or non-clinical data, providing such data may significantly delay the potential approval of REMOXY.

Our research and clinical approaches may not lead to drugs that the FDA considers safe for humans and effective for
indicated uses we are studying. The FDA may require additional studies, in which case we or our collaborators would have to expend additional time and resources and would likely delay the date of potentially receiving regulatory approval. The
approval process may also be delayed by changes in government regulation, future legislation or administrative action or changes in FDA policy that occur prior to or during our regulatory review. Delays in obtaining regulatory approvals would:



| |  |  | delay commercialization of, and product revenues from, our drug candidates; and
| | - |  | -------------------------------------------------------------------------------

| |  |  | diminish the competitive advantages that we may have otherwise enjoyed, which would have an adverse effect on our operating results and financial
condition.
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------



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Even if we or our collaborators comply with all FDA regulatory requirements,
our drug candidates may never obtain regulatory approval. If we or our collaborators fail to obtain regulatory approval for any of our drug candidates we will have fewer commercial products, if any, and corresponding lower product revenues, if any.
Even if our drug candidates receive regulatory approval, such approval may involve limitations on the indications and conditions of use or marketing claims for our products. Further, later discovery of previously unknown problems or adverse events
could result in additional regulatory restrictions, including withdrawal of products. The FDA may also require us or our collaborators to commit to perform lengthy Phase IV post-approval clinical trials. Our expending additional resources on such
trials would have an adverse effect on our operating results and financial condition.

In jurisdictions
outside the United States, we or our collaborators must receive marketing authorizations from the appropriate regulatory authorities before commercializing our drugs. Regulatory approval processes outside the United States generally include all of
the aforementioned requirements and risks associated with FDA approval.

If we or our collaborators are unable to design,
conduct and complete clinical trials successfully, our drug candidates will not be able to receive regulatory approval.

In order to obtain FDA approval for any of our drug candidates, we or our collaborators must submit to the FDA an NDA that demonstrates with substantive evidence that the drug candidate is both safe and
effective in humans for its intended use. This demonstration requires significant research and animal tests, which are referred to as preclinical studies, as well as human tests, which are referred to as clinical trials.

Results from Phase I clinical programs may not support moving a drug candidate to Phase II or Phase III clinical trials.
Phase III clinical trials may not demonstrate the safety or efficacy of our drug candidates. Success in preclinical studies and early clinical trials does not ensure that later clinical trials will be successful. Results of later clinical trials may
not replicate the results of prior clinical trials and preclinical studies. Even if the results of Phase III clinical trials are positive, we or our collaborators may have to commit substantial time and additional resources to conducting further
preclinical studies and clinical trials before obtaining FDA approval for any of our drug candidates.

Clinical trials are very expensive and difficult to design and implement, in part because they are subject to rigorous
requirements. The clinical trial process also consumes a significant amount of time. Furthermore, if participating patients in clinical trials suffer drug-related adverse reactions during the course of such clinical trials, or if we, our
collaborators or the FDA believe that participating patients are being exposed to unacceptable health risks, such clinical trials will have to be suspended or terminated. Failure can occur at any stage of the clinical trials, and we or our
collaborators could encounter problems that cause abandonment or repetition of clinical trials.

Our clinical
trials with REMOXY and our potential future clinical trials for other drug candidates for treatment of pain measure clinical symptoms, such as pain and physical dependence that are not biologically measurable. The success in clinical trials of
REMOXY and our other drug candidates designed to reduce potential risks of unintended use depends on reaching statistically significant changes in patients symptoms based on clinician-rated scales.



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Due in part to a lack of consensus on standardized processes for assessing clinical outcomes, these scores may or may not be reliable, useful or acceptable to regulatory agencies.

We have no history of developing drug candidates for oncology or hemophilia. We do not know whether any of our planned
clinical trials in metastatic melanoma or hemophilia will result in marketable drugs.

In addition, completion
of clinical trials can be delayed by numerous factors, including:



| |  |  | delays in identifying and agreeing on acceptable terms with prospective clinical trial sites;
| | - |  | ---------------------------------------------------------------------------------------------

| |  |  | slower than expected rates of patient recruitment and enrollment;
| | - |  | -----------------------------------------------------------------

| |  |  | unanticipated patient drop out rates;
| | - |  | -------------------------------------

| |  |  | increases in time required to complete monitoring of patients during or after participation in a clinical trial; and
| | - |  | --------------------------------------------------------------------------------------------------------------------

| |  |  | unexpected need for additional patient-related data.
| | - |  | ----------------------------------------------------

Any of these delays could significantly impact the timing, approval and commercialization of our drug candidates and
could significantly increase our overall costs of drug development.

Even if clinical trials are completed as
planned, their results may not support expectations or intended marketing claims. The clinical trials process may fail to demonstrate that our drug candidates are safe and effective for indicated uses. Such failure would cause us to abandon a drug
candidate and could delay development of other drug candidates.

Clinical trial designs that were discussed with
authorities prior to their commencement may subsequently be considered insufficient for approval at the time of application for regulatory approval.

We discuss with and obtain guidance from regulatory authorities on certain of our clinical development activities. With the exception of our Special Protocol Assessment, or SPA, such as the one we
completed with the FDA with respect to the Phase III clinical trial for REMOXY, these discussions are not binding obligations on the part of regulatory authorities.

Regulatory authorities may revise previous guidance or decide to ignore previous guidance at any time during the course
of our clinical activities or after the completion of our clinical trials. Even with successful clinical safety and efficacy data, including such data from a clinical trial conducted pursuant to an SPA, we may be required to conduct additional,
expensive clinical trials to obtain regulatory approval.

Developments by competitors may establish standards of care that
affect our ability to conduct our clinical trials as planned.

We have conducted clinical trials of our
drug candidates comparing our drug candidates to both placebo and other approved drugs. Changes in standards related to clinical trial design could affect our ability to design and conduct clinical trials as planned. For example, regulatory
authorities may not allow us to compare our drug candidates to placebo in a particular clinical indication where approved products are available. In that case, both the cost and the amount of time required to conduct a clinical trial could increase.



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The DEA limits the availability of the active ingredients in certain of our current drug
candidates and, as a result, quotas for these ingredients may not be sufficient to complete clinical trials, or to meet commercial demand or may result in clinical delays.

The U.S. Drug Enforcement Administration, or DEA, regulates chemical compounds as Schedule I, II, III, IV or V
substances, with Schedule I substances considered to present the highest risk of substance abuse and Schedule V substances the lowest risk. Certain active ingredients in our current drug candidates, such as oxycodone, are listed by the DEA as
Schedule II under the Controlled Substances Act of 1970. Consequently, their manufacture, research, shipment, storage, sale and use are subject to a high degree of oversight and regulation. For example, all Schedule II drug prescriptions must be
signed by a physician, physically presented to a pharmacist and may not be refilled without a new prescription. Furthermore, the amount of Schedule II substances that can be obtained for clinical trials and commercial distribution is limited by the
DEA and quotas for these substances may not be sufficient to complete clinical trials or meet commercial demand. There is a risk that DEA regulations may interfere with the supply of the drugs used in clinical trials for our product candidates, and,
in the future, the ability to produce and distribute our products in the volume needed to meet commercial demand.

Conducting clinical trials of our drug candidates or potential commercial sales of a drug candidate may expose us to expensive product
liability claims and we may not be able to maintain product liability insurance on reasonable terms or at all.

The risk of product liability is inherent in the testing of pharmaceutical products. If we cannot successfully defend ourselves against product liability claims, we may incur substantial liabilities or be
required to limit or terminate testing of one or more of our drug candidates. Our inability to obtain sufficient product liability insurance at an acceptable cost to protect against potential product liability claims could prevent or inhibit the
commercialization of our drug candidates. We currently carry clinical trial insurance but do not carry product liability insurance. If we successfully commercialize one or more of our drug candidates, we may face product liability claims, regardless
of FDA approval for commercial manufacturing and sale. We may not be able to obtain such insurance at a reasonable cost, if at all. Even if our agreements with any current or future corporate collaborators entitle us to indemnification against
product liability losses, such indemnification may not be available or adequate should any claim arise.

If our drug
candidates receive regulatory approval, we and our collaborators will also be subject to ongoing FDA obligations and continued regulatory review, such as continued safety reporting requirements, and we and our collaborators may also be subject to
additional FDA post-marketing obligations or new regulations, all of which may result in significant expense and limit our and our collaborators ability to commercialize our potential drugs.

Any regulatory approvals that our drug candidates receive may also be subject to limitations on the indicated uses for
which the drug may be marketed or contain requirements for potentially costly post-marketing follow-up studies. In addition, if the FDA approves any of our drug candidates, the labeling, packaging, adverse event reporting, storage, advertising,
promotion and record keeping for the drug will be subject to extensive regulatory requirements. The subsequent discovery of previously unknown problems with the drug, including but not limited to adverse



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events of unanticipated severity or frequency, or the discovery that adverse events previously observed in preclinical research or clinical trials that were believed to be minor actually
constitute much more serious problems, may result in restrictions on the marketing of the drug, and could include withdrawal of the drug from the market.

The FDAs policies may change and additional government regulations may be enacted that could prevent or delay regulatory approval of our drug candidates. For example, the FDA has met with the
sponsors of opioid drug products in order to discuss Risk Evaluation and Mitigation Strategies, or REMS, for opioid drugs. These discussions may result in changes to or additional government regulations with respect to our opioid drug candidates. We
cannot predict the likelihood, nature or extent of adverse government regulation that may arise from future legislation or administrative action, either in the United States or abroad. If we are not able to maintain regulatory compliance, we may be
subject to fines, suspension or withdrawal of regulatory approvals, product recalls, seizure of products, operating restrictions and criminal prosecution. Any of these events could prevent us from marketing our drugs and our business could suffer.

Risks Relating to our Collaboration Agreements

Pfizers acquisition of King may have an adverse impact on our collaboration.

Pfizer completed its acquisition of King in early 2011. Drugs or drug candidates being commercialized or developed by
Pfizer, its subsidiaries and affiliates may compete for research, development and commercialization resources with our drug candidates that are subject to the King Agreements. Further, any post-merger integration of Pfizers and Kings
businesses may divert the attention of management and personnel at King from their focus on seeking approval of REMOXY or otherwise supporting the other drug candidates that are subject to our collaboration. Pfizer is a much larger company than King
was prior to Pfizers acquisition of King. Pfizer may have different strategic interests than King had as an independent company. There can be no assurance that King or Pfizer will devote sufficient resources to the continued development of
REMOXY and the other drug candidate that are the subject of our collaboration in a timely manner.

If King, Pfizer or other
outside collaborators fail to devote sufficient time and resources to our drug development programs, or if their performance is substandard, regulatory submissions and introductions for our products may be delayed.

We rely on Pfizer and its subsidiaries to devote time and resources to the development, manufacturing and
commercialization of REMOXY and other drug candidates under the King Agreements. Pfizer and its subsidiaries and affiliates may commercialize, develop or acquire drugs or drug candidates that may compete directly or compete for resources with our
drug candidates under the King Agreements. For instance, King is developing Oxycodone NT (an extended release abuse resistant formulation of oxycodone that would compete with REMOXY) and markets and sells Embeda (an extended-release oral formulation
of morphine sulfate) and Avinza (a once-daily morphine treatment for moderate to severe pain). There can be no assurance that these other drugs or drug candidates in the Pfizer corporate family will not become competitive with our drug candidates
being developed under the King Agreements. If time and



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resources devoted are limited or there is a failure to fund the continued development of REMOXY or other opioid drug candidates as required by the King Agreements, or there is otherwise a failure
to perform as we expect, we may not achieve clinical and regulatory milestones and regulatory submissions and related product introductions may be delayed or prevented, and revenues that we would receive from these activities will be less than
expected. In addition, if King fails to perform as required under the King Agreements, their failure may jeopardize our rights under our license with Durect.

We depend on independent investigators and collaborators, such as universities and medical institutions, to conduct our clinical trials under agreements with us. These investigators and collaborators are
not our employees and we cannot control the amount or timing of resources that they devote to our programs. They may not assign as great a priority to our programs or pursue them as diligently as we would if we were undertaking such activities
ourselves. If these investigators or collaborators fail to devote sufficient time and resources to our drug development programs, or if their performance is substandard, the approval of our regulatory submissions and our introductions of new drugs
will be delayed or prevented.

Our collaborators may also have relationships with other commercial entities,
some of which may compete with us. If outside collaborators assist our competitors to our detriment, the approval of our regulatory submissions will be delayed and the sales from our products, if any are commercialized, will be less than expected.

If we fail to maintain our collaboration agreements and licenses for REMOXY and other drugs designed to reduce potential
risks of unintended use, we may have to reduce or delay our drug candidate development.

Our plan for
developing, manufacturing and commercializing REMOXY and other drugs designed to reduce potential risks of unintended use currently requires us to successfully maintain the King Agreements to advance our programs and provide funding to support our
expenditures on REMOXY and other drug candidates and to maintain our license from Durect. If we are not able to maintain the King Agreements or if King doesnt provide the required funding under the King Agreements and the funding required to
meet our obligations to Durect, we may have to limit the size or scope of, or delay or abandon the development of other drug candidates or undertake and fund development of these drug candidates ourselves and if we are unable to meet the obligations
necessary to maintain our license with Durect for one or more potential products we may lose the rights to utilize Durects technology for such potential products. If we elect to fund drug development efforts with respect to REMOXY and other
drug candidates on our own, we may need to obtain additional capital, which may not be available on acceptable terms, or at all.

We may not succeed at in-licensing drug candidates or technologies to expand our product pipeline.

We may not successfully in-license drug candidates or technologies to expand our product pipeline. The number of such candidates and technologies is limited. Competition among large pharmaceutical
companies and biopharmaceutical companies for promising drug candidates and technologies is intense because such companies generally desire to expand their product pipelines



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through in-licensing. If we fail to carry out such in-licensing and expand our product pipeline, our potential future revenues may suffer.

Our collaborative agreements may not succeed or may give rise to disputes over intellectual property, disputes concerning the scope of
collaboration activities or other issues.

Our strategy to focus on drug development requires us to enter
into collaborative agreements with third parties, such as the King Agreements and our license agreement with Durect. Such agreements are generally complex and contain provisions that could give rise to legal disputes, including potential disputes
concerning ownership of intellectual property under collaborations or disputes concerning the scope of collaboration activities. Such disputes can delay or prevent the development of potential new drug products, or can lead to lengthy, expensive
litigation or arbitration. Other factors relating to collaborative agreements may adversely affect the success of our drug candidates, including:



| |  |  | the development of parallel products by our collaborators or by a competitor;
| | - |  | -----------------------------------------------------------------------------

| |  |  | arrangements with collaborative partners that limit or preclude us from developing certain products or technologies;
| | - |  | --------------------------------------------------------------------------------------------------------------------

| |  |  | premature termination of a collaborative or license agreement; or
| | - |  | -----------------------------------------------------------------

| |  |  | failure by a collaborative partner to provide required funding or to devote sufficient resources to the development of or legal defense of our
potential products.
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------

Risks Relating to Commercialization

If physicians and patients do not accept and use our drugs, we will not achieve sufficient product revenues and our business will
suffer.

Even if the FDA approves our drugs, physicians and patients may not accept and use them.
Acceptance and use of our drugs will depend on a number of factors including:



| |  |  | perceptions by members of the healthcare community, including physicians, about the safety and effectiveness of our drugs, and, in particular, the
effectiveness of REMOXY in reducing potential risks of unintended use;
| | - |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  | perceptions by physicians regarding the cost benefit of REMOXY in reducing potential risks of unintended use;
| | - |  | -------------------------------------------------------------------------------------------------------------

| |  |  | published studies demonstrating the cost-effectiveness of our drugs relative to competing products;
| | - |  | ---------------------------------------------------------------------------------------------------

| |  |  | availability of reimbursement for our products from government or healthcare payers;
| | - |  | ------------------------------------------------------------------------------------

| |  |  | our or our collaborators ability to implement a risk management plan prior to the distribution of any Schedule II drug; and
| | - |  | ----------------------------------------------------------------------------------------------------------------------------

| |  |  | effectiveness of marketing and distribution efforts by King or Pfizer, us and other licensees and distributors.
| | - |  | ---------------------------------------------------------------------------------------------------------------

Because we expect to rely on sales generated by our current lead drug candidates for substantially all of our revenues
for the foreseeable future, the failure of any of these drugs to find market acceptance would harm our business and could require us to seek additional financing.



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If Pfizer or its subsidiaries are not successful in developing and commercializing REMOXY
and in commercializing other opioid drugs under the King Agreements, our revenues and our business will suffer.

Our ability to earn royalties from sales of REMOXY depends on Kings, and the greater Pfizer corporate familys, ability to obtain regulatory approval for and commercialize REMOXY. Additionally,
our ability to earn royalties from sales of REMOXY and other drugs subject to the King Agreements will depend on Kings, and the greater Pfizer corporate familys, ability to maintain regulatory approval and achieve market acceptance of
such drugs once commercialized. Pfizer or its subsidiaries (including King) may elect to independently develop drugs that could compete with ours or fail to commit sufficient resources to the development, marketing and distribution of REMOXY and
other drugs developed under the King Agreements. King, along with its parent and affiliated entities, may not proceed with the commercialization of REMOXY and other drugs developed under the King Agreements with the same degree of urgency as we
would because of other priorities they face. If King and its parent and affiliated entities are not successful in developing or commercializing REMOXY for a variety of reasons, including but not limited to competition from other pharmaceutical
companies, or if King and its parent and affiliated entities fail to perform as we expect, our potential for revenue from drugs developed the King Agreements, if any, could be dramatically reduced and our business would suffer.

If we are unable to develop our own sales, marketing and distribution capabilities, or if we are not successful in contracting with
third parties for these services on favorable terms, or at all, our product revenues could be disappointing.

We currently have no sales, marketing or distribution capabilities. Except with regard to products developed under the King Agreements, in order to commercialize our products, if any are approved by the
FDA, we will either have to develop such capabilities internally or collaborate with third parties who can perform these services for us. If we decide to commercialize any of our drugs ourselves, we may not be able to hire the necessary experienced
personnel and build sales, marketing and distribution operations which are capable of successfully launching new drugs and generating sufficient product revenues. In addition, establishing such operations will take time and involve significant
expense.

If we decide to enter into new co-promotion or other licensing arrangements with third parties, we
may be unable to locate acceptable collaborators because the number of potential collaborators is limited and because of competition from others for similar alliances with potential collaborators. Even if we are able to identify one or more
acceptable new collaborators, we may not be able to enter into any collaborative arrangements on favorable terms, or at all.

In addition, due to the nature of the market for our drug candidates, it may be necessary for us to license all or substantially all of our drug candidates not covered by the King Agreements to a single
collaborator, thereby eliminating our opportunity to commercialize these other products independently. If we enter into any such new collaborative arrangements, our revenues are likely to be lower than if we marketed and sold our products ourselves.

In addition, any revenues we receive would depend upon our collaborators efforts which may not be
adequate due to lack of attention or resource commitments, management turnover,



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change of strategic focus, business combinations or other factors outside of our control. Depending upon the terms of our collaboration, the remedies we have against an under-performing
collaborator may be limited. If we were to terminate the relationship, it may be difficult or impossible to find a replacement collaborator on acceptable terms, or at all.

If we cannot compete successfully for market share against other drug companies, we may not achieve sufficient product revenues and our business will suffer.

The market for our drug candidates is characterized by intense competition and rapid technological advances. If our drug
candidates receive FDA approval, they will compete with a number of existing and future drugs and therapies developed, manufactured and marketed by others. Existing or future competing products may provide greater therapeutic convenience or clinical
or other benefits for a specific indication than our products, or may offer comparable performance at a lower cost. If our products are unable to capture and maintain market share, we may not achieve sufficient product revenues and our business will
suffer.

We and our collaborators will compete for market share against fully integrated pharmaceutical
companies or other companies that are collaborating with larger pharmaceutical companies, academic institutions, government agencies and other public and private research organizations. Many of these competitors have drugs already approved or drug
candidates in development that will or may compete against our approved drug candidates. In addition, many of these competitors, either alone or together with their collaborative partners, operate larger research and development programs and have
substantially greater financial resources than we do, as well as significantly greater experience in:



| |  |  | developing drugs;
| | - |  | -----------------

| |  |  | conducting preclinical testing and human clinical trials;
| | - |  | ---------------------------------------------------------

| |  |  | obtaining FDA and other regulatory approvals of drugs;
| | - |  | ------------------------------------------------------

| |  |  | formulating and manufacturing drugs; and
| | - |  | ----------------------------------------

| |  |  | launching, marketing, distributing and selling drugs.
| | - |  | -----------------------------------------------------

If we fail to obtain acceptable prices or an adequate level of reimbursement for our products from healthcare payers, our ability to generate product revenues will be diminished.

Our ability to commercialize our drugs, alone or with collaborators, will depend in part on the extent to which
reimbursement will be available from:



| |  |  | government and health administration authorities;
| | - |  | -------------------------------------------------

| |  |  | private health maintenance organizations and health insurers; and
| | - |  | -----------------------------------------------------------------

| |  |  | other healthcare payers.
| | - |  | ------------------------

Significant uncertainty exists as to the reimbursement status of newly approved healthcare products. Healthcare payers, including Medicare, health maintenance organizations and managed care organizations,
are challenging the prices charged for medical products and services and/or are seeking pharmacoeconomic data to justify formulary acceptance and reimbursement practices. We currently have not generated pharmacoeconomic data on any of our drug
candidates. Government and other healthcare payers increasingly are attempting to contain



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healthcare costs by limiting both coverage and the level of reimbursement for drugs, and by refusing, in some cases, to provide coverage for uses of approved products for disease indications for
which the FDA has or has not granted labeling approval. Adequate third-party insurance coverage may not be available to patients for any products we discover and develop, alone or with collaborators. If government and other healthcare payers do not
provide adequate coverage and reimbursement levels for our products, market acceptance of our drug candidates could be limited.

Government agencies may establish and promulgate usage guidelines that could limit the use of our drug candidates.

Government agencies, professional and medical societies, and other groups may establish usage guidelines that apply to
our drug candidates. These guidelines could address such matters as usage and dose, among other factors. Application of such guidelines could limit the clinical use or commercial appeal of our drug candidates.

Risks Relating to our Intellectual Property

Our ability to commercialize our drug candidates will depend on our ability to sell such products without infringing the patent or proprietary rights of third parties. If we are sued for infringing the
intellectual property rights of third parties, such litigation will be costly and time consuming and an unfavorable outcome would have a significant adverse effect on our business.

Our ability to commercialize our drug candidates will depend on our ability to sell such products without infringing the
patents or other proprietary rights of third parties. Intellectual property rights in the areas of controlled-release technology, pharmaceutical ingredients, antibodies, gene integration and more generally, in oncology, neurology,
radiopharmaceutical technologies and gene therapy are complicated and are continuously evolving. Holders of patent rights in these areas may allege that the commercialization of REMOXY or our other drug candidates infringes such patent rights. While
we believe that we would have valid defenses to any claim of infringement, there can be no assurance that these or other third party patents will not limit our ability to commercialize REMOXY or our other drug candidates.

In addition, because patent applications are published 18 months after their filing, and because applications can take
several years to issue, there may be currently pending third-party patent applications that are unknown to us, which may later result in issued patents. If a third-party claims that we infringe on its patents or other proprietary rights, we could
face a number of issues that could seriously harm our competitive position, including:



| |  |  | infringement claims that, with or without merit, can be costly and time consuming to litigate, can delay the regulatory approval process and can
divert managements attention from our core business strategy;
| | - |  | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  | substantial damages for past infringement which we may have to pay if a court determines that our products or technologies infringe upon a
competitors patent or other proprietary rights;
| | - |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



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| |  |  | a court order prohibiting us from commercializing our products or technologies unless the holder licenses the patent or other proprietary rights to
us, which such holder is not required to do;
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  | if a license is available from a holder, we may have to pay substantial royalties or grant cross licenses to our patents or other proprietary
rights; and
| | - |  | ---------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  | redesigning our process so that it does not infringe the third-party intellectual property rights, which may not be possible, or which may require
substantial time and expense including delays in bringing our own products to market. Such actions could harm our competitive position and our ability to generate revenue and could result in increased costs.
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

If we are unable to protect our intellectual property our competitors could develop and market products with similar features that may
reduce demand for our drug candidates.

Our success, competitive position and potential future revenues
will depend in part on our ability to protect our intellectual property. If we or our collaborators fail to file, prosecute, obtain or maintain certain patents, our competitors could market products that contain features and clinical benefits
similar to those of our products, and demand for our products could decline as a result.

We and our
collaborators have filed patent applications with the U.S. Patent and Trademark Office to further protect our technologies. If these patent applications do not result in issued patents, the duration or scope of our patent rights may be limited
and our future revenues could be lower as a result.

We may be involved in challenges to our intellectual
property. An adverse outcome of a challenge to our intellectual property could result in loss of claims of patents or other intellectual property rights that pertain to certain drugs we currently have under development and could have a material
adverse impact on our future revenues.

We intend to file additional patent applications relating to our
technology, products and processes. We may direct our collaborators to file additional patent applications relating to the licensed technology or we may do so ourselves. However, our competitors may challenge, invalidate or circumvent any of our
current or future patents. These patents may also fail to provide us with meaningful competitive advantages.

We may become
involved in expensive litigation or other legal proceedings related to our existing intellectual property rights, including patents.

We expect that we will rely upon patents, trade secrets, know-how, continuing technological innovations and licensing opportunities to develop and maintain our competitive position. Others may
independently develop substantially equivalent proprietary information or be issued patents that may prevent the sale of our products or know-how or require us to license such information and pay significant fees or royalties in order to produce our
products.

Our technology could infringe upon claims of patents owned by others. If we were found to be
infringing on a patent held by another, we might have to seek a license to use the patented technology. In that case, we might not be able to obtain such a license on terms acceptable to us,



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or at all. If a legal action were to be brought against us or our licensors, we could incur substantial defense costs, and any such action might not be resolved in our favor. If such a dispute
were to be resolved against us, we could have to pay the other party large sums of money and our use of our technology and the testing, manufacture, marketing or sale of one or more of our proposed products could be restricted or prohibited.

Risks Relating to our Business and Strategy

Competition for qualified personnel in the pharmaceutical industry is intense, and if we are not successful in attracting and
retaining qualified personnel, we could experience delays in completing necessary clinical trials, in the regulatory approval process or in formulating, manufacturing, marketing and selling our potential products.

We will need to hire additional qualified personnel with expertise in clinical research, preclinical testing, government
regulation, formulation and manufacturing and sales and marketing. We compete for qualified individuals with numerous biopharmaceutical companies, universities and other research institutions. Competition for such individuals, particularly in the
San Francisco Bay area, is intense, and our search for such personnel may not be successful. Attracting and retaining qualified personnel is critical to our success.

If third-party manufacturers of our drug candidates fail to devote sufficient time and resources to our concerns, or if their performance is substandard, our clinical trials and product introductions
may be delayed and our costs may be higher than expected.

We have no manufacturing facilities and have
limited experience in drug product development and commercial manufacturing. We lack the resources and expertise to formulate, manufacture or test the technical performance of our drug candidates. We currently rely on a limited number of experienced
personnel and a small number of contract manufacturers and other vendors to formulate, test, supply, store and distribute drug supplies for our clinical trials. Our reliance on a limited number of vendors exposes us to the following risks, any of
which could delay our clinical trials, and, consequently, FDA approval of our drug candidates and commercialization of our products, result in higher costs, or deprive us of potential product revenues:



| |  |  | Contract commercial manufacturers, their sub-contractors or other third parties we rely on, may encounter difficulties in achieving the volume of
production needed to satisfy clinical needs or commercial demand, may experience technical issues that impact quality or compliance with applicable and strictly enforced regulations governing the manufacture of pharmaceutical products, and may
experience shortages of qualified personnel to adequately staff production operations.
| | - |  | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  | Our contract manufacturers could default on their agreements with us to provide clinical supplies or meet our requirements for commercialization of
our products.
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  | For certain of our drug candidates, the use of alternate manufacturers may be difficult because the number of potential manufacturers that have the
necessary governmental licenses to produce narcotic products is limited. Additionally, the FDA and the DEA must approve any alternative manufacturer of our products before we may use the alternative manufacturer to produce our supplies.
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



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| |  |  | It may be difficult or impossible for us to find a replacement manufacturer on acceptable terms quickly, or at all. Our contract manufacturers and
vendors may not perform as agreed or may not remain in the contract manufacturing business for the time required to successfully produce, store and distribute our products.
| | - |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  | If any contract manufacturer makes improvements in the manufacturing process for our products, we may not own, or may have to share, the
intellectual property rights to such innovation.
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

We may not be able to successfully develop or
commercialize potential drug candidates for indications other than pain.

Our research and development
activities include development of potential drug candidates for indications other than pain, such as metastatic melanoma and hemophilia. We have no history of developing metastatic melanoma or hemophilia drug candidates or manufacturing
radiopharmaceuticals. We do not know whether any of our planned clinical trials in metastatic melanoma or hemophilia will result in marketable products. We do not anticipate that our drug candidates in these areas will reach the market for at least
several years, if at all.

Our employees and consultants are generally subject to confidentiality or other agreements with
their former employers and they may inadvertently or otherwise violate those agreements.

Many of our
employees and consultants were previously employed at universities or biotechnology or pharmaceutical companies. While we require our employees and consultants to honor any agreements they may have entered into prior to working with us, we may be
subject to claims that we inadvertently or otherwise used or disclosed trade secrets or other confidential information belonging to former employers. Failure to defend such claims could result in loss of valuable rights or personnel, which in turn
could harm or prevent commercialization of our drug candidates. Successful defense against such claims can be expensive and might distract us from executing our strategies.

Law enforcement concerns over diversion of opioids and social issues around abuse of opioids may make the regulatory approval process and commercialization of our drug candidates very difficult.

Media stories regarding the diversion of opioids and other controlled substances are commonplace. Law
enforcement agencies or regulatory agencies may apply policies that seek to limit the availability of opioids. Such efforts may adversely affect the regulatory approval and commercialization of our drug candidates.

Developments by competitors may render our products or technologies obsolete or non-competitive.

Alternative technologies and products are being developed to improve or replace the use of opioids for pain management,
several of which are in clinical trials or are awaiting approval from the FDA. In addition, the active ingredients in nearly all opioid drugs are available in generic form. Drug companies that sell generic opioid drugs represent substantial
competition. Many of these organizations competing with us have substantially greater capital resources, larger



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research and development staffs and facilities, greater experience in drug development and in obtaining regulatory approvals and greater manufacturing and marketing capabilities than we do. Our
competitors may market less expensive or more effective drugs that would compete with our drug candidates or reach market with competing drugs before we are able to reach market with our drug candidates. These organizations also compete with us to
attract qualified personnel and partners for acquisitions, joint ventures or other collaborations.

Business interruptions
could limit our ability to operate our business.

Our operations as well as those of our collaborators on
which we depend are vulnerable to damage or interruption from computer viruses, human error, natural disasters, electrical and telecommunication failures, international acts of terror and similar events. We have not established a formal disaster
recovery plan and our back-up operations and our business interruption insurance may not be adequate to compensate us for losses we may suffer. A significant business interruption could result in losses or damages incurred by us and require us to
cease or curtail our operations.

Risks Relating to Manufacturing

We rely on third-party commercial drug manufacturers for drug supply.

Approved third-party commercial drug manufacturers may subsequently be stopped from producing, storing, shipping or
testing our drug products due to their non-compliance with federal, state or local regulations. Drug manufacturers are subject to ongoing periodic unannounced inspection by the FDA, the DEA, and corresponding state and foreign government agencies to
ensure strict compliance with GMP and other government regulations and corresponding foreign standards. We do not have control over third-party manufacturers compliance with these regulations and standards.

In addition, even if we enter into long-term supply arrangements with third-party suppliers, we cannot control changes in
strategy by third-party suppliers that affect their ability or willingness to continue to supply our drug products on acceptable terms.

If our drug supply for one of our drug candidates was interrupted, our operations could be negatively affected.

If we and King cannot formulate and scale-up a wide range of dosage forms of REMOXY and other drug candidates designed to reduce potential risks of unintended use, we and King might determine that the
commercial opportunity for REMOXY and these other drug candidates in certain dosage forms is too limited to warrant further investment in clinical testing and development.

We and King plan to formulate and scale-up a wide range of dosage forms of REMOXY and other drug candidates designed to
reduce potential risks of unintended use. We and King may not be able to successfully complete our formulation or scale-up activities or we may determine that the commercial opportunity for REMOXY and these other drug candidates in certain dosage
forms is too limited to warrant further investment. If we and King are unsuccessful in our formulation or scale-up activities with REMOXY and these other drug candidates, our future



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revenue from milestones and royalties under the King Agreements may be less than expected and our operations may suffer.

We and King rely solely on Durect to provide us with certain components of REMOXY and other drug candidates designed to reduce potential risks of unintended use and will continue to rely on Durect to
produce commercial supplies of these components.

We and King rely on Durect as the sole source provider
of certain components of REMOXY and other drug candidates designed to reduce potential risks of unintended use, and will rely solely on Durect to produce commercial supplies of these components. Durects failure to achieve and maintain
satisfactory manufacturing standards could result in product recalls or withdrawals, delays or failures in product testing or delivery, cost overruns or other problems that could materially harm our business. Durect may encounter manufacturing
difficulties involving production yields, quality control and quality assurance. Durect is subject to ongoing periodic unannounced inspection by the FDA and corresponding state and foreign agencies to ensure strict compliance with government
regulations and corresponding foreign standards. We cannot control Durects compliance with these regulations and standards.

If King receives marketing approval for and commercially launches REMOXY or other candidates under the King Agreements, Durect may need to materially expand its manufacturing capacity. Durect may not be
able to increase its manufacturing capacity for REMOXY and these other drug candidates in a timely or economic manner, or at all. Moreover, significant scale up of manufacturing will require additional validation studies, which are subject to FDA
review and approval. If Durect is unable to successfully increase the manufacturing capacity for such components of REMOXY and these other drugs, at an acceptable cost or otherwise, and King is unable to establish alternative manufacturing
capabilities, commercialization of REMOXY and these other drugs may be delayed, prevented or impaired or there may be a shortage in supply, which would harm our future revenues and cause our business to suffer.

Risks Relating to our Financial Position and Need for Financing

Our operating history may make it difficult for you to evaluate our business to date and to assess its future viability.

Our operations from our inception to date have been limited to organizing and staffing our company,
acquiring, developing and securing our technology, undertaking preclinical studies and clinical trials of our drug candidates and forming collaborations. We have not yet demonstrated our ability to obtain regulatory approval, formulate and
manufacture our drug candidates on a commercial scale or conduct sales and marketing activities. Consequently, any predictions you make about our future success or viability may not be as accurate as they could be if we had a longer operating
history.

We have a history of losses and expect to incur substantial losses and negative operating cash flows for the
foreseeable future.

Although we were profitable in some years in the past based on payments from King and
interest income, we have yet to generate any revenues from product sales. We had an



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accumulated deficit. Even if we succeed in developing and commercializing one or more of our drug candidates, we expect to continue to use significant cash resources in our operations for the
foreseeable future. We anticipate that our expenses will increase substantially in the foreseeable future as we:



| |  |  | continue to conduct preclinical studies and clinical trials for our drug candidates;
| | - |  | ------------------------------------------------------------------------------------

| |  |  | seek regulatory approvals for our drug candidates;
| | - |  | --------------------------------------------------

| |  |  | develop, formulate, manufacture and commercialize our drug candidates;
| | - |  | ----------------------------------------------------------------------

| |  |  | implement additional internal systems and develop new infrastructure;
| | - |  | ---------------------------------------------------------------------

| |  |  | acquire or in-license additional products or technologies, or expand the use of our technology;
| | - |  | -----------------------------------------------------------------------------------------------

| |  |  | maintain, defend and expand the scope of our intellectual property; and
| | - |  | -----------------------------------------------------------------------

| |  |  | hire additional personnel.
| | - |  | --------------------------

We will need to generate significant revenues to achieve and maintain profitability. If we cannot successfully develop, obtain regulatory approval for and commercialize our drug candidates, we will not be
able to generate such revenues or achieve profitability in the future. Our failure to achieve or maintain profitability would have a material adverse impact on the market price of our common stock.

If we cannot raise additional capital on acceptable terms, we may be unable to complete planned clinical trials of any or some of our
drug candidates or to pursue attractive business opportunities.

We have funded all of our operations and
capital expenditures with the proceeds from our public and private stock offerings, payments received under the King Agreements and interest earned on our investments. We expect that our current cash, cash equivalents and marketable securities will
be sufficient to meet our working capital and capital expenditure needs for at least the next twelve months. However, we may elect to raise additional funds within such twelve-month period or need to raise additional funds thereafter and additional
financing may not be available on favorable terms, if at all. Even if we succeed in selling additional securities to raise funds, our existing stockholders ownership percentage would be reduced and new investors may demand rights, preferences
or privileges senior to those of existing stockholders. If we raise additional capital through debt financing, if available, such financings may involve covenants that restrict our business activities. If we raise additional capital through
strategic alliance and license arrangements such as the King Agreements, we may have to trade our rights to our technology, intellectual property or drug candidates to others in such arrangements on terms that may not be favorable to us.

If we determine that we need to raise additional funds and we are not successful in doing so, we may be unable to
complete the clinical development of some or all of our drug candidates or to seek or obtain FDA approval of our drug candidates. We then could be forced to discontinue product development, enter into a relationship with an additional strategic
partner earlier than currently intended, reduce sales and marketing efforts or forego attractive business opportunities.

Risks Relating to an Investment in our Common Stock



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Our stock price has been volatile and could experience a sudden decline in value.

Our common stock has experienced significant price and volume fluctuations and may continue to experience
volatility in the future. You may not be able to sell your shares quickly or at the latest market price if trading in our stock is not active or the volume is low. The following factors, in addition to other risk factors described in this section,
may have a significant impact on the market price of our common stock:



| |  |  | results of or delays in efforts to seek regulatory approval for REMOXY, and in preclinical studies and clinical trials for our other drug
candidates;
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  | publicity regarding actual or potential medical results relating to products under development by us or others;
| | - |  | ---------------------------------------------------------------------------------------------------------------

| |  |  | the status of our collaboration agreements;
| | - |  | -------------------------------------------

| |  |  | announcements of technological innovations or new commercial products by us or others;
| | - |  | --------------------------------------------------------------------------------------

| |  |  | developments in patent or other proprietary rights by us or others;
| | - |  | -------------------------------------------------------------------

| |  |  | comments or opinions by securities analysts or major stockholders;
| | - |  | ------------------------------------------------------------------

| |  |  | future sales of our common stock by existing stockholders;
| | - |  | ----------------------------------------------------------

| |  |  | developments with respect to potential merger and acquisition activity of companies with whom we have strategic alliances or other agreements;
| | - |  | ----------------------------------------------------------------------------------------------------------------------------------------------

| |  |  | regulatory developments or changes in regulatory guidance enacted by applicable governmental or other authorities;
| | - |  | ------------------------------------------------------------------------------------------------------------------

| |  |  | litigation or threats of litigation;
| | - |  | ------------------------------------

| |  |  | economic and other external factors or other disaster or crises;
| | - |  | ----------------------------------------------------------------

| |  |  | the departure of any of our officers, directors or key employees;
| | - |  | -----------------------------------------------------------------

| |  |  | period-to-period fluctuations in financial results; and
| | - |  | -------------------------------------------------------

| |  |  | limited daily trading volume.
| | - |  | -----------------------------

Changing laws, regulations and standards relating to corporate governance and public disclosure, including the Sarbanes-Oxley Act of 2002, the Dodd-Frank Act of 2010, SEC regulations and the rules of The
NASDAQ Stock Market LLC, create uncertainty for public companies. If we were unable to continue to comply with these requirements, we could be delisted from trading on the NASDAQ Global Select Market, or Nasdaq, and thereafter trading in our common
stock, if any, may be conducted through the over-the-counter or other market. As a consequence of such delisting, an investor would likely find it more difficult to dispose of, or to obtain quotations as to the price of, our common stock. Delisting
of our common stock could also result in lower prices per share of our common stock than would otherwise prevail.



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Anti-takeover provisions in our charter documents, our Stockholder Rights Plan and
Delaware law may prevent or delay removal of incumbent management or a change of control.

Anti-takeover
provisions of our amended and restated certificate of incorporation and amended and restated bylaws, our Stockholder Rights Plan and Delaware law may have the effect of deterring or delaying attempts by our stockholders to remove or replace
management, engage in proxy contests and effect changes in control. The provisions of our charter documents include:



| |  |  | a classified board so that only one of the three classes of directors on our board of directors is elected each year;
| | - |  | ---------------------------------------------------------------------------------------------------------------------

| |  |  | elimination of cumulative voting in the election of directors;
| | - |  | --------------------------------------------------------------

| |  |  | procedures for advance notification of stockholder nominations and proposals;
| | - |  | -----------------------------------------------------------------------------

| |  |  | the ability of our board of directors to amend our bylaws without stockholder approval; and
| | - |  | -------------------------------------------------------------------------------------------

| |  |  | the ability of our board of directors to issue up to 10,000,000 shares of preferred stock without stockholder approval upon the terms and conditions
and with the rights, privileges and preferences as our board of directors may determine.
| | - |  | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

The rights issued pursuant to our Stockholder Rights Plan will become exercisable, subject to certain exceptions, the
tenth day after a person or group announces acquisition of 15% or more of our common stock or announces commencement of a tender or exchange offer the consummation of which would result in ownership by the person or group of 15% or more of our
common stock.

In addition, as a Delaware corporation, we are subject to Delaware law, including
Section 203 of the Delaware General Corporation Law. In general, Section 203 prohibits a Delaware corporation from engaging in any business combination with any interested stockholder for a period of three years following the date that the
stockholder became an interested stockholder unless certain specific requirements are met as set forth in Section 203.

These provisions, alone or together, could have the effect of deterring or delaying changes in incumbent management, proxy contests or changes in control.

Volatility in the stock prices of other companies may contribute to volatility in our stock price.

The stock market in general, Nasdaq and the market for technology companies in particular, have experienced significant
price and volume fluctuations that have often been unrelated or disproportionate to the operating performance of those companies. Further, there has been particular volatility in the market prices of securities of early stage life sciences
companies. These broad market and industry factors may seriously harm the market price of our common stock, regardless of our operating performance. In the past, following periods of volatility in the market price of a companys securities,
securities class action litigation has often been instituted. A securities class action suit against us could result in substantial costs, potential liabilities and the diversion of managements attention and resources.

Our share ownership is concentrated, and our officers, directors and principal stockholders can exert significant control over matters
requiring stockholder approval.



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Due to their combined stock holdings, our officers, directors and principal
stockholders (stockholders holding greater than 5% of our common stock) acting collectively may have the ability to exercise significant influence over matters requiring stockholder approval including the election of directors and approval of
significant corporate transactions. This concentration of ownership may delay or prevent a change in control of the Company and may make some transactions more difficult or impossible to complete without the support of these stockholders.

Publicly available information regarding stockholders ownership may not be comprehensive because the
SEC does not require certain large stockholders to publicly disclose their stock ownership positions.

Our operating
results may fluctuate from quarter to quarter and this fluctuation may cause our stock price to decline.

Our quarterly operating results have fluctuated in the past and are likely to fluctuate in the future. Factors
contributing to these fluctuations include, among other items, the timing and amounts of collaboration revenue recognized from King, the timing and enrollment rates of clinical trials for our drug candidates, our need for clinical supplies and the
valuation of stock-based compensation. Thus, quarter-to-quarter comparisons of our operating results are not indicative of what we might expect in the future. As a result, in some future quarters our clinical, financial or operating results may not
meet the expectations of securities analysts and investors that could result in a decline in the price of our stock.

There
may not be an active, liquid trading market for our common stock.

There is no guarantee that an active
trading market for our common stock will be maintained on Nasdaq. Investors may not be able to sell their shares quickly or at the latest market price if trading in our stock is not active.

Item 2.Unregistered Sales of Equity Securities and Use of Proceeds

None.

Item 3.Defaults Upon Senior
Securities

None.

Item 4.(Removed and Reserved)

Item 5.Other Information

None.



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Item 6.Exhibits

The following exhibits have been filed with this report:



|               |  |                                                                                                                                                                                                                                                                        
|-------------- |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|Exhibit Number |  | Description of Document                                                                                                                                                                                                                                                
|3.1  (1)       |  | Amended and Restated Certificate of Incorporation.                                                                                                                                                                                                                     
|3.2  (2)       |  | Amended and Restated Bylaws.                                                                                                                                                                                                                                           
|4.1  (1)       |  | Specimen Common Stock Certificate.                                                                                                                                                                                                                                     
|4.2  (3)       |  | Preferred Stock Rights Agreement, dated as of April 28, 2005 between Registrant and Mellon Investor Services LLC, including the Certificate of Designation,
the form of Rights Certificate and Summary of Rights attached thereto as Exhibits A, B and C, respectively.
|10.1           |  | Lease agreement, dated as of February 14, 2011 between Registrant and StoneCliff Office, L.P.                                                                                                                                                                          
|31.1           |  | Certification of Chief Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.                                                                                                                                                                    
|31.2           |  | Certification of Chief Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.                                                                                                                                                                    
|32.1           |  | Certifications of the Chief Executive Officer and the Chief Financial Officer pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002.                                                                                





|(1) | Incorporated by reference from exhibits to our report on Form 10-Q for the period ended June 30, 2005.
|--- | ------------------------------------------------------------------------------------------------------

|(2) | Incorporated by reference from exhibits to our report on Form 10-Q for the period ended March 31, 2005.
|--- | -------------------------------------------------------------------------------------------------------

|(3) | Incorporated by reference from exhibits to our report on Form 8-K as filed with the Securities and Exchange Commission on May 3, 2005.
|--- | --------------------------------------------------------------------------------------------------------------------------------------



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##### Table of Contents

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its
behalf by the undersigned thereunto duly authorized.



Pain Therapeutics, Inc.(Registrant)/s/ REMI BARBIERRemi Barbier,Chairman of the Board of Directors,President and Chief Executive Officer/s/ PETER S. RODDYPeter S. Roddy,Vice President and Chief Financial Officer


Date: April 27, 2011



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##### Table of Contents

EXHIBIT INDEX



|               |  |                                                                                                                                                                                                                                                                        
|-------------- |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|Exhibit Number |  | Description of Document                                                                                                                                                                                                                                                
|3.1  (1)       |  | Amended and Restated Certificate of Incorporation.                                                                                                                                                                                                                     
|3.2  (2)       |  | Amended and Restated Bylaws.                                                                                                                                                                                                                                           
|4.1  (1)       |  | Specimen Common Stock Certificate.                                                                                                                                                                                                                                     
|4.2  (3)       |  | Preferred Stock Rights Agreement, dated as of April 28, 2005 between Registrant and Mellon Investor Services LLC, including the Certificate of Designation,
the form of Rights Certificate and Summary of Rights attached thereto as Exhibits A, B and C, respectively.
|10.1           |  | Lease agreement, dated as of February 14, 2011 between Registrant and StoneCliff Office, L.P.                                                                                                                                                                          
|31.1           |  | Certification of Chief Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.                                                                                                                                                                    
|31.2           |  | Certification of Chief Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.                                                                                                                                                                    
|32.1           |  | Certifications of the Chief Executive Officer and the Chief Financial Officer pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002.                                                                                





|(1) | Incorporated by reference from exhibits to our report on Form 10-Q for the period ended June 30, 2005.
|--- | ------------------------------------------------------------------------------------------------------

|(2) | Incorporated by reference from exhibits to our report on Form 10-Q for the period ended March 31, 2005.
|--- | -------------------------------------------------------------------------------------------------------

|(3) | Incorporated by reference from exhibits to our report on Form 8-K as filed with the Securities and Exchange Commission on May 3, 2005.
|--- | --------------------------------------------------------------------------------------------------------------------------------------



44