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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 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 September 30, 2010

OR



| ̈ | TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
|- | ----------------------------------------------------------------------------------------

For the transition period from              to
            .

Commission file number 000-31141





INFINITY PHARMACEUTICALS, INC.

(Exact Name of Registrant as Specified in its Charter)







|                                                               |  |                                     
|-------------------------------------------------------------- |  | ------------------------------------
|Delaware                                                       |  | 33-0655706                          
|(State or Other Jurisdiction of
Incorporation or Organization) |  | (I.R.S. Employer Identification No.)

780 Memorial Drive,
Cambridge, Massachusetts 02139

(Address of Principal Executive Offices) (Zip Code)

(617) 453-1000

(Registrants 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 smaller
reporting company. See the definitions of large accelerated filer, accelerated filer and smaller reporting company in Rule 12b-2 of the Exchange Act.



|                        |  |                                                  |  |                           |  |  
|----------------------- |  | ------------------------------------------------ |  | ------------------------- |  | -
|Large accelerated filer |  |  ̈                                                |  | Accelerated filer         |  | x
|                        |  |                                                  | 
|Non-accelerated filer   |  |  ̈  (Do not check if a smaller reporting company) |  | 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

Number of shares of the registrants Common Stock, $0.001 par value, outstanding on September 30, 2010: 26,368,479









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INFINITY
PHARMACEUTICALS, INC.

FORM 10-Q

FOR THE QUARTER ENDED SEPTEMBER 30, 2010

TABLE OF
CONTENTS



|         |  |                                                                                                                 |  |          |    | 
|-------- |  | --------------------------------------------------------------------------------------------------------------- |  | -------- | -- | 
|         |  |                                                                                                                 |  | Page No. |   
|PART I   |  | FINANCIAL INFORMATION                                                                                           |  |          | 1  | 
|         |  |                                                                                                                
|Item 1.  |  | Unaudited Condensed Consolidated Financial Statements                                                           |  |          | 1  | 
|         |  |                                                                                                                
|         |  | Condensed Consolidated Balance Sheets as of September 30, 2010 and December 31, 2009                            |  |          | 1  | 
|         |  |                                                                                                                
|         |  | Condensed Consolidated Statements of Operations for the Three and Nine Months Ended September 30, 2010 and 2009 |  |          | 2  | 
|         |  |                                                                                                                
|         |  | Condensed Consolidated Statements of Cash Flows for the Three and Nine Months Ended September 30, 2010 and 2009 |  |          | 3  | 
|         |  |                                                                                                                
|         |  | Notes to Condensed Consolidated Financial Statements                                                            |  |          | 4  | 
|         |  |                                                                                                                
|Item 2.  |  | Managements Discussion and Analysis of Financial Condition and Results of Operations                           |  |          | 14 | 
|         |  |                                                                                                                
|Item 3.  |  | Quantitative and Qualitative Disclosures About Market Risk                                                      |  |          | 23 | 
|         |  |                                                                                                                
|Item 4.  |  | Controls and Procedures                                                                                         |  |          | 24 | 
|         |  |                                                                                                                
|PART II  |  | OTHER INFORMATION                                                                                               |  |          | 24 | 
|         |  |                                                                                                                
|Item 1A. |  | Risk Factors                                                                                                    |  |          | 24 | 
|         |  |                                                                                                                
|Item 6.  |  | Exhibits                                                                                                        |  |          | 38 | 
|         |  |                                                                                                                
|         |  | Signatures                                                                                                      |  |          | 39 | 



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PART I. FINANCIAL INFORMATION



|Item 1. | Unaudited Condensed Consolidated Financial Statements
|------- | -----------------------------------------------------

INFINITY PHARMACEUTICALS, INC.

Condensed
Consolidated Balance Sheets

(unaudited)



|                                                                                                                                                                                |  |                    |              |   |                   |   |              |  
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |  | ------------------ | ------------ | - | ----------------- | - | ------------ | -
|                                                                                                                                                                                |  | September 30, 2010 |              |   | December 31, 2009 |  
|Assets                                                                                                                                                                          |  |                    |              |   |                   |   |              |  
|Current assets:                                                                                                                                                                 |  |                    |              |   |                   |   |              |  
|Cash and cash equivalents                                                                                                                                                       |  | $                  | 18,180,304   |   |                   | $ | 16,287,229   |  
|Available-for-sale securities                                                                                                                                                   |  |                    | 91,263,107   |   |                   |   | 113,758,778  |  
|Unbilled accounts receivable from Purdue entities                                                                                                                               |  |                    | 5,579,244    |   |                   |   |             |  
|Notes receivable from employees                                                                                                                                                 |  |                    | 41,936       |   |                   |   | 55,059       |  
|Prepaid expenses and other current assets                                                                                                                                       |  |                    | 2,806,961    |   |                   |   | 3,511,968    |  
|                                                                                                                                                                                |  |                    |              |   |                   |   |              |  
|Total current assets                                                                                                                                                            |  |                    | 117,871,552  |   |                   |   | 133,613,034  |  
|Property and equipment, net                                                                                                                                                     |  |                    | 5,261,112    |   |                   |   | 5,694,150    |  
|Loan commitment asset from Purdue entities, net                                                                                                                                 |  |                    | 14,721,150   |   |                   |   | 16,020,075   |  
|Long-term available-for-sale securities                                                                                                                                         |  |                    | 740,621      |   |                   |   | 690,506      |  
|Notes receivable from employees                                                                                                                                                 |  |                    | 26,085       |   |                   |   | 38,036       |  
|Restricted cash                                                                                                                                                                 |  |                    | 1,121,786    |   |                   |   | 1,146,788    |  
|Other assets                                                                                                                                                                    |  |                    | 150,373      |   |                   |   | 115,244      |  
|                                                                                                                                                                                |  |                    |              |   |                   |   |              |  
|Total assets                                                                                                                                                                    |  | $                  | 139,892,679  |   |                   | $ | 157,317,833  |  
|                                                                                                                                                                                |  |                    |              |   |                   |   |              |  
|Liabilities and stockholders equity                                                                                                                                            |  |                    |              |   |                   |   |              |  
|Current liabilities:                                                                                                                                                            |  |                    |              |   |                   |   |              |  
|Accounts payable                                                                                                                                                                |  | $                  | 2,149,996    |   |                   | $ | 1,441,231    |  
|Accrued expenses                                                                                                                                                                |  |                    | 23,721,309   |   |                   |   | 8,549,382    |  
|Deferred revenue from Purdue entities                                                                                                                                           |  |                    | 2,987,512    |   |                   |   | 2,987,512    |  
|                                                                                                                                                                                |  |                    |              |   |                   |   |              |  
|Total current liabilities                                                                                                                                                       |  |                    | 28,858,817   |   |                   |   | 12,978,125   |  
|Deferred revenue from Purdue entities, less current portion                                                                                                                     |  |                    | 33,614,499   |   |                   |   | 35,855,463   |  
|Other liabilities                                                                                                                                                               |  |                    | 1,212,389    |   |                   |   | 2,224,713    |  
|                                                                                                                                                                                |  |                    |              |   |                   |   |              |  
|Total liabilities                                                                                                                                                               |  |                    | 63,685,705   |   |                   |   | 51,058,301   |  
|Commitments and contingencies                                                                                                                                                   |  |                    |             |   |                   |   |             |  
|Stockholders equity:                                                                                                                                                           |  |                    |              |   |                   |   |              |  
|Preferred Stock, $.001 par value; 1,000,000 shares authorized; no shares issued and outstanding at September 30, 2010 and
December 31, 2009                                     |  |                    |             |   |                   |   |             |  
|Common Stock, $.001 par value; 100,000,000 shares authorized; 26,368,479 and 26,238,954 shares issued and outstanding at
September 30, 2010 and December 31, 2009, respectively |  |                    | 26,369       |   |                   |   | 26,239       |  
|Additional paid-in capital                                                                                                                                                      |  |                    | 293,358,803  |   |                   |   | 287,593,176  |  
|Accumulated deficit                                                                                                                                                             |  |                    | (217,263,165 | ) |                   |   | (181,397,174 | )
|Accumulated other comprehensive income                                                                                                                                          |  |                    | 84,967       |   |                   |   | 37,291       |  
|                                                                                                                                                                                |  |                    |              |   |                   |   |              |  
|Total stockholders equity                                                                                                                                                      |  |                    | 76,206,974   |   |                   |   | 106,259,532  |  
|                                                                                                                                                                                |  |                    |              |   |                   |   |              |  
|Total liabilities and stockholders equity                                                                                                                                      |  | $                  | 139,892,679  |   |                   | $ | 157,317,833  |  
|                                                                                                                                                                                |  |                    |              |   |                   |   |              |  

The accompanying notes are an integral part of these unaudited, condensed consolidated financial
statements.



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INFINITY PHARMACEUTICALS, INC.

Condensed Consolidated Statements of Operations

(unaudited)



|                                                                       |  |                                  |             |   |                                 |   |            |      |  |   |             |   |  |   |             |  
|---------------------------------------------------------------------- |  | -------------------------------- | ----------- | - | ------------------------------- | - | ---------- | ---- |  | - | ----------- | - |  | - | ----------- | -
|                                                                       |  | Three Months Ended September 30, |             |   | Nine Months Ended September 30, |  
|                                                                       |  | 2010                             |             |   | 2009                            |   |            | 2010 |  |   | 2009        |  
|Collaborative research and development revenue from Purdue entities    |  | $                                | 22,189,115  |   |                                 | $ | 13,775,745 |      |  | $ | 56,570,208  |   |  | $ | 36,370,000  |  
|Operating expenses:                                                    |  |                                  |             |   |                                 |   |            |      |  |   |             |   |  |   |             |  
|Research and development                                               |  |                                  | 38,731,902  |   |                                 |   | 18,499,060 |      |  |   | 77,120,670  |   |  |   | 60,453,361  |  
|General and administrative                                             |  |                                  | 5,014,987   |   |                                 |   | 4,570,282  |      |  |   | 14,980,274  |   |  |   | 15,581,871  |  
|                                                                       |  |                                  |             |   |                                 |   |            |      |  |   |             |   |  |   |             |  
|Total operating expenses                                               |  |                                  | 43,746,889  |   |                                 |   | 23,069,342 |      |  |   | 92,100,944  |   |  |   | 76,035,232  |  
|                                                                       |  |                                  |             |   |                                 |   |            |      |  |   |             |   |  |   |             |  
|Loss from operations                                                   |  |                                  | (21,557,774 | ) |                                 |   | (9,293,597 | )    |  |   | (35,530,736 | ) |  |   | (39,665,232 | )
|Other income (expense):                                                |  |                                  |             |   |                                 |   |            |      |  |   |             |   |  |   |             |  
|Interest expense                                                       |  |                                  | (521,742    | ) |                                 |   | (433,272   | )    |  |   | (1,387,983  | ) |  |   | (866,943    | )
|Income from residual funding after reacquisition of Hsp90 program      |  |                                  |            |   |                                 |   |           |      |  |   |            |   |  |   | 12,450,000  |  
|Income from NIH reimbursement                                          |  |                                  |            |   |                                 |   |           |      |  |   |            |   |  |   | 1,745,386   |  
|Interest and investment income                                         |  |                                  | 122,474     |   |                                 |   | 401,264    |      |  |   | 352,407     |   |  |   | 1,735,742   |  
|                                                                       |  |                                  |             |   |                                 |   |            |      |  |   |             |   |  |   |             |  
|Net other income (expense)                                             |  |                                  | (399,268    | ) |                                 |   | (32,008    | )    |  |   | (1,035,576  | ) |  |   | 15,064,185  |  
|                                                                       |  |                                  |             |   |                                 |   |            |      |  |   |             |   |  |   |             |  
|Loss before income taxes                                               |  |                                  | (21,957,042 | ) |                                 |   | (9,325,605 | )    |  |   | (36,566,312 | ) |  |   | (24,601,047 | )
|Income tax benefit                                                     |  |                                  | 700,321     |   |                                 |   |           |      |  |   | 700,321     |   |  |   |            |  
|                                                                       |  |                                  |             |   |                                 |   |            |      |  |   |             |   |  |   |             |  
|Net loss                                                               |  | $                                | (21,256,721 | ) |                                 | $ | (9,325,605 | )    |  | $ | (35,865,991 | ) |  | $ | (24,601,047 | )
|                                                                       |  |                                  |             |   |                                 |   |            |      |  |   |             |   |  |   |             |  
|Basic and diluted loss per common share                                |  | $                                | (0.81       | ) |                                 | $ | (0.36      | )    |  | $ | (1.36       | ) |  | $ | (0.94       | )
|                                                                       |  |                                  |             |   |                                 |   |            |      |  |   |             |   |  |   |             |  
|Basic and diluted weighted average number of common shares outstanding |  |                                  | 26,333,012  |   |                                 |   | 26,154,557 |      |  |   | 26,287,775  |   |  |   | 26,062,217  |  
|                                                                       |  |                                  |             |   |                                 |   |            |      |  |   |             |   |  |   |             |  

The accompanying notes are an integral part of these unaudited, condensed consolidated financial
statements.



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INFINITY PHARMACEUTICALS, INC.

Condensed Consolidated Statements of Cash Flows

(unaudited)



|                                                                                          |  |                                     |              |   |                                     |   |              |  
|----------------------------------------------------------------------------------------- |  | ----------------------------------- | ------------ | - | ----------------------------------- | - | ------------ | -
|                                                                                          |  | Nine Months EndedSeptember 30, 2010 |              |   | Nine Months EndedSeptember 30, 2009 |  
|Operating activities                                                                      |  |                                     |              |   |                                     |   |              |  
|Net loss                                                                                  |  | $                                   | (35,865,991  | ) |                                     | $ | (24,601,047  | )
|Adjustments to reconcile net loss to net cash provided by (used in) operating activities: |  |                                     |              |   |                                     |   |              |  
|Depreciation                                                                              |  |                                     | 1,634,238    |   |                                     |   | 1,591,335    |  
|Stock-based compensation, including 401(k) match                                          |  |                                     | 5,579,700    |   |                                     |   | 5,444,847    |  
|Impairment of property and equipment                                                      |  |                                     | 311,200      |   |                                     |   |             |  
|Gain on sales of property and equipment                                                   |  |                                     |             |   |                                     |   | (62,171      | )
|Amortization of loan commitment asset from Purdue entities                                |  |                                     | 1,298,925    |   |                                     |   | 865,950      |  
|Net amortization (accretion) of available-for-sale securities                             |  |                                     | 1,142,790    |   |                                     |   | (242,801     | )
|Other, net                                                                                |  |                                     | 56,513       |   |                                     |   | 24,381       |  
|Changes in operating assets and liabilities:                                              |  |                                     |              |   |                                     |   |              |  
|Accounts receivable and unbilled accounts receivable                                      |  |                                     | (5,579,244   | ) |                                     |   | 7,414,570    |  
|Prepaid expenses and other assets                                                         |  |                                     | 646,674      |   |                                     |   | (860,930     | )
|Accounts payable, accrued expenses and other liabilities                                  |  |                                     | 14,898,489   |   |                                     |   | (1,968,844   | )
|Deferred revenue from Purdue entities                                                     |  |                                     | (2,240,964   | ) |                                     |   | 16,187,370   |  
|                                                                                          |  |                                     |              |   |                                     |   |              |  
|Net cash provided by (used in) operating activities                                       |  |                                     | (18,117,670  | ) |                                     |   | 3,792,660    |  
|Investing activities                                                                      |  |                                     |              |   |                                     |   |              |  
|Purchases of property and equipment                                                       |  |                                     | (1,512,400   | ) |                                     |   | (1,854,995   | )
|Proceeds from sales of property and equipment                                             |  |                                     |             |   |                                     |   | 62,171       |  
|Purchases of available-for-sale securities                                                |  |                                     | (168,676,720 | ) |                                     |   | (134,813,291 | )
|Proceeds from sales of available-for-sale securities                                      |  |                                     | 7,239,262    |   |                                     |   | 36,141,736   |  
|Proceeds from maturities of available-for-sale securities                                 |  |                                     | 182,788,023  |   |                                     |   | 102,117,084  |  
|                                                                                          |  |                                     |              |   |                                     |   |              |  
|Net cash provided by investing activities                                                 |  |                                     | 19,838,165   |   |                                     |   | 1,652,705    |  
|Financing activities                                                                      |  |                                     |              |   |                                     |   |              |  
|Proceeds from issuances of common stock                                                   |  |                                     | 160,732      |   |                                     |   | 168,924      |  
|Proceeds from issuance of common stock and warrants to Purdue entities                    |  |                                     |             |   |                                     |   | 11,830,000   |  
|Release of restricted cash                                                                |  |                                     | 26,642       |   |                                     |   |             |  
|Capital lease payments                                                                    |  |                                     | (4,794       | ) |                                     |   | (4,419       | )
|New employee loans                                                                        |  |                                     | (10,000      | ) |                                     |   | (40,000      | )
|                                                                                          |  |                                     |              |   |                                     |   |              |  
|Net cash provided by financing activities                                                 |  |                                     | 172,580      |   |                                     |   | 11,954,505   |  
|                                                                                          |  |                                     |              |   |                                     |   |              |  
|Net increase in cash and cash equivalents                                                 |  |                                     | 1,893,075    |   |                                     |   | 17,399,870   |  
|Cash and cash equivalents at beginning of period                                          |  |                                     | 16,287,229   |   |                                     |   | 16,574,549   |  
|                                                                                          |  |                                     |              |   |                                     |   |              |  
|Cash and cash equivalents at end of period                                                |  | $                                   | 18,180,304   |   |                                     | $ | 33,974,419   |  
|                                                                                          |  |                                     |              |   |                                     |   |              |  

The accompanying notes are an integral part of these unaudited, condensed consolidated financial
statements.



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Infinity Pharmaceuticals, Inc.

Notes to Condensed Consolidated Financial Statements

(Unaudited)

1. Organization

Infinity Pharmaceuticals, Inc. is a drug discovery and development company that is utilizing its strength in small molecule drug technologies to discover and develop medicines for difficult to treat
diseases. As used throughout these unaudited, condensed consolidated financial statements, the terms Infinity, we, us, and our refer to the business of Infinity Pharmaceuticals, Inc. and its wholly
owned subsidiary.

2. Basis of Presentation

These condensed consolidated financial statements include the accounts of Infinity and its wholly owned subsidiary. We have eliminated all significant intercompany accounts and transactions in
consolidation.

The accompanying condensed consolidated financial statements have been prepared in accordance with generally
accepted accounting principles for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted
accounting principles for complete financial statements. In the opinion of management, all adjustments, consisting of normal recurring accruals and revisions of estimates, considered necessary for a fair presentation of the accompanying condensed
consolidated financial statements have been included. Interim results for the three and nine months ended September 30, 2010 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2010.

The information presented in the condensed consolidated financial statements and related footnotes at September 30,
2010, and for the three and nine months ended September 30, 2010 and 2009, is unaudited, and the condensed consolidated balance sheet amounts and related footnotes at December 31, 2009 have been derived from our audited financial
statements. For further information, please refer to the consolidated financial statements and accompanying footnotes included in our annual report on Form 10-K for the fiscal year ended December 31, 2009, which was filed with the U.S.
Securities and Exchange Commission (SEC) on March 12, 2010.

3. Significant Accounting Policies

Cash Equivalents and Available-For-Sale Securities

Cash equivalents and available-for-sale securities primarily consist of money market funds, U.S. government-sponsored enterprise obligations, corporate obligations, U.S. Treasury obligations and
mortgage-backed securities. We consider all highly liquid investments with maturities of three months or less at the time of purchase to be cash equivalents. Cash equivalents, which consist of money market funds, corporate obligations and
U.S. government-sponsored enterprise obligations, are stated at fair value. They are also readily convertible to known amounts of cash and close enough to maturity that each presents insignificant risk of change in value due to changes in interest
rates. Our classification of cash equivalents is consistent with prior periods.

We determine the appropriate classification
of available-for-sale securities at the time of purchase and reevaluate such designation at each balance sheet date. We have classified all of our marketable securities at September 30, 2010 and December 31, 2009 as
available-for-sale. We carry available-for-sale securities at fair value, with the unrealized gains and losses reported in accumulated other comprehensive income, which is a separate component of stockholders equity.

We adjust the cost of available-for-sale debt securities for amortization of premiums and accretion of discounts to maturity.
We include such amortization and accretion in interest and investment income. The cost of securities sold is based on the specific identification method. We include interest and dividends on available-for-sale securities in interest and
investment income.

We conduct periodic reviews to identify and evaluate each investment that has an unrealized loss in order
to determine whether an other-than-temporary impairment exists. An unrealized loss exists when the current fair value of an individual security is less than its amortized cost basis. Unrealized losses on available-for-sale debt securities that are
determined to be temporary, and not related to credit loss, are recorded, net of tax, in accumulated other comprehensive income.

For available-for-sale debt securities with unrealized losses, we perform an analysis to assess whether we intend to sell or whether we would more likely than not be required to sell the security before
the expected recovery of the amortized cost basis. Where we intend to sell a security, or may be required to do so, the securitys decline in fair value is deemed to be other-than-temporary and the full amount of the unrealized loss is recorded
within earnings as an impairment loss.



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Regardless of our
intent to sell a security, we perform additional analysis on all securities with unrealized losses to evaluate losses associated with the creditworthiness of the security. Credit losses are identified where we do not expect to receive cash flows
sufficient to recover the amortized cost basis of a security and are recorded within earnings as an impairment loss.

Segment Information

We make operating decisions based upon performance of the enterprise as a whole and utilize our consolidated financial statements for decision making. We operate in one business segment, which focuses on
drug discovery and development.

All of our revenues to date have been generated under research collaboration agreements.
Revenue associated with the amortization of the deferred revenue associated with the grant of rights and licenses to, and reimbursed research and development services provided for, Mundipharma International Corporation Limited
(Mundipharma) and Purdue Pharmaceutical Products L.P. (Purdue) accounted for all of our revenue for the three and nine months ended September 30, 2010 and 2009. Payments due from Mundipharma and Purdue represented the
entire unbilled accounts receivable as of September 30, 2010. Following entry into the strategic alliance agreements in November 2008, we consider Mundipharma, Purdue and associated entities to be related parties for financial reporting
purposes because of their equity ownership (see Note 8).

Basic and Diluted Loss per Common Share

Basic loss per share is based upon the weighted average number of common shares outstanding during the period, excluding restricted shares
of common stock that have been issued but are not yet vested. Diluted loss per share is based upon the weighted average number of common shares outstanding during the period, plus the effect of additional weighted average common equivalent shares
outstanding during the period when the effect of adding such shares is dilutive. Common equivalent shares result from the assumed exercise of outstanding stock options (the proceeds of which are then assumed to have been used to repurchase
outstanding stock using the treasury stock method) and the vesting of restricted shares of common stock. In addition, the assumed proceeds under the treasury stock method include the average unrecognized compensation expense of stock options that
are in-the-money. This results in the assumed buyback of additional shares, thereby reducing the dilutive impact of stock options. Common equivalent shares have not been included in the loss per share calculations for the periods
presented because the effect of including them would have been anti-dilutive. Total potential gross common equivalent shares consisted of the following:



|                           |  |                  |           |  |      |  |           | 
|-------------------------- |  | ---------------- | --------- |  | ---- |  | --------- | 
|                           |  | At September 30, |          
|                           |  | 2010             |           |  | 2009 | 
|Stock options              |  |                  | 6,027,450 |  |      |  | 5,051,643 | 
|Warrants                   |  |                  | 5,246,629 |  |      |  | 6,246,629 | 
|Unvested restricted shares |  |                  | 3,420     |  |      |  | 22,164    | 

Stock-Based
Compensation Expense

We measure stock-based compensation cost at the grant date based on the estimated fair value of
the award, and recognize it as expense over the employees requisite service period on a straight-line basis. We have no awards with market or performance conditions. We use the Black-Scholes valuation model in determining the fair value of
equity awards.

Revenue Recognition

To date, all of our revenue has been generated under research collaboration agreements. The terms of these research collaboration agreements may include payment to us of non-refundable, up-front license
fees, funding or reimbursement of research and development efforts, milestone payments if specified objectives are achieved, and/or royalties on product sales. We divide agreements containing multiple elements into separate units of accounting if
certain criteria are met, including whether the delivered element has stand-alone value to the collaborative partner and whether there is objective and reliable evidence of fair value of the undelivered obligation(s). For these agreements, we
allocate the consideration we receive among the separate units based on their respective fair values or, in some cases, the residual method, and we apply the applicable revenue recognition criteria to each of the separate units.

We recognize revenues from non-refundable, up-front license fees on a straight-line basis over the contracted or estimated period of
performance, which is typically the research or development term. We recognize research and development funding as earned over the period of effort as related research costs are incurred in proportion to our forecasted total expenses as compared to
the total research funding budget for the year. We regularly consider whether events warrant a change in the estimated period of performance under an agreement. Such a change would cause us to modify the period of time over which we recognize
revenue from the up-front license fee on a prospective basis and would, in turn, result in changes in our quarterly and annual results.

We recognize milestone payments as revenue upon achievement of the milestone only if (1) the milestone payment is non-refundable, (2) substantive effort is involved in achieving the milestone,
(3) the amount of the milestone is reasonable in relation to the



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effort expended or the risk associated with achievement of the milestone, and (4) the milestone is at risk for both parties. If any of these conditions is not met, we defer the recognition
of revenue underlying the milestone payment and recognize it over the remaining estimated period of performance under the contract as we complete our performance obligations.

We will recognize royalty revenue, if any, based upon actual and estimated net sales by the licensee of licensed products in licensed territories, and in the period the sales occur. We have not recognized
any royalty revenues to date.

Research and Development Expense

Research and development expense consists of expenses incurred in performing research and development activities, including salaries and
benefits, facilities expenses, overhead expenses, materials and supplies, preclinical expenses, clinical trial and related clinical manufacturing expenses, costs associated with the licensing of research and development programs, stock-based
compensation expense, contract services, and other outside expenses. We expense research and development costs as they are incurred. We have entered into certain collaboration agreements in which expenses are shared with the collaborator, others in
which we are reimbursed for work performed on behalf of the collaborator, and another in which we reimburse the collaborator for work it has performed. We record all of our expenses as research and development expense. If the arrangement is a
cost-sharing arrangement and there is a period during which we receive payments from the collaborator, we record payments from the collaborator for its share of the development effort as a reduction of research and development expense. If the
arrangement is a cost-sharing arrangement and there is a period during which we make payments to the collaborator, we record our payments to the collaborator for its share of the development effort as additional research and development expense. If
the arrangement provides for reimbursement of research and development expenses, as is the case with our alliance with Mundipharma and Purdue, we record the reimbursement as revenue. If the arrangement provides for us to reimburse the collaborator
for research and development expenses, as is the case with our agreement with Intellikine, Inc. (Intellikine) we record the reimbursement as research and development expense.

Income Taxes

We use the liability method to account for income taxes. Deferred tax assets and liabilities are determined based on differences between financial reporting and income tax basis of assets and
liabilities, as well as net operating loss carryforwards, and are measured using the enacted tax rates and laws that will be in effect when the differences reverse. Deferred tax assets are reduced by a valuation allowance to reflect the
uncertainty associated with their ultimate realization. The effect on deferred taxes of a change in tax rate is recognized in income or loss in the period that includes the enactment date.

We use our judgment for the recognition threshold and measurement attribute for the financial statement recognition and measurement of a
tax position taken or expected to be taken in a tax return. We recognize any material interest and penalties related to unrecognized tax benefits in income tax expense.

Due to the uncertainty surrounding the realization of the favorable tax attributes in future tax returns, we have recorded a full valuation allowance against our otherwise recognizable net deferred tax
assets as of September 30, 2010 and December 31, 2009.

Fair Value Measurements

We define fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction
between market participants at the measurement date. We determine fair value based on the assumptions market participants use when pricing the asset or liability. We also use the fair value hierarchy that prioritizes the information used to develop
these assumptions.

The carrying amounts reflected in the condensed consolidated balance sheets for unbilled accounts
receivable from Purdue and Mundipharma, notes receivable from employees, prepaid expenses and other current assets, accounts payable and accrued expenses approximate fair value due to their short term maturities.

Property and Equipment

Property and equipment are stated at cost. Depreciation is recorded using the straight-line method over the estimated useful lives of the applicable assets. Application development costs incurred for
computer software developed or obtained for internal use are capitalized. Upon sale or retirement, the cost and related accumulated depreciation are eliminated from the applicable account and the resulting gain or loss, if any, is included in
current operations. Amortization of leasehold improvements and capital leases are included in depreciation expense. Repairs and maintenance charges that do not increase the useful life of the assets are charged to operations as incurred. Property
and equipment are depreciated over the following periods:



|                                |  |                                                 
|------------------------------- |  | ------------------------------------------------
|Laboratory equipment            |  | 5 years                                         
|Computer equipment and software |  | 3 to 5 years                                    
|Leasehold improvements          |  | Shorter of life of lease or useful life of asset
|Furniture and fixtures          |  | 7 years                                         



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We regularly review
our property and equipment and evaluate the carrying value for impairment whenever events or changes in circumstances indicate that such values may not be recoverable. An impairment loss is recognized when the carrying amount of a long-lived asset
is not recoverable and exceeds its fair value. During the quarter ended September 30, 2010, we recognized an impairment loss of $311,200 related to lab equipment as a consequence of decreased clinical trial activity of IPI-504. This amount is
included in research and development expense in the statement of operations. We determined the fair value of the equipment based on quoted market prices.

New Accounting Pronouncements

In October 2009, the FASB issued
Accounting Standard Update No. 2009-13, Multiple-Element Revenue Arrangements(ASU No. 2009-13) ,which updates the existing multiple-element revenue arrangements guidance currently included in Accounting
Standards Codification No. 605-25 in two ways. The first change relates to the determination of when the individual deliverables included in a multiple-element arrangement may be treated as separate units of accounting. This is significant as
it will likely result in the requirement to separate more deliverables within an arrangement, ultimately leading to less revenue deferral. The second change modifies the manner in which the transaction consideration is allocated across the
separately identified deliverables. ASU No. 2009-13 also significantly expands the disclosures required for multiple-element revenue arrangements. ASU No. 2009-13 will be effective for the first annual reporting period beginning on or
after June 15, 2010, and may be applied retrospectively for all periods presented or prospectively to arrangements entered into or materially modified after the adoption date. We do not expect ASU No. 2009-13 to have a material impact on
our financial statements or results of operations.

In April 2010, the Financial Accounting Standards Board issued Accounting
Standard Update No. 2010-17, Milestone Method of Revenue Recognition (ASU No. 2010-17), which provides guidance on defining a milestone and determining when it may be appropriate to apply the milestone method of revenue
recognition for research or development transactions. Prior to the issuance of ASU No. 2010-17, authoritative guidance on the use of the milestone method did not exist. ASU No. 2010-17 is effective on a prospective basis for milestones
achieved in fiscal years, and interim periods within those years, beginning on or after June 15, 2010 with early adoption permitted. Alternatively, ASU No. 2010-17 can be adopted retrospectively for all prior periods. We do not expect ASU
No. 2010-17 to have a material impact on our financial statements or results of operations.

4. Stock-Based Compensation

2010 Stock Incentive Plan

Our 2010 Stock Incentive Plan (the 2010 Plan) was approved by our stockholders in May 2010. The 2010 Plan provides for the grant of incentive stock options intended to qualify under
Section 422 of the Internal Revenue Code of 1986, as amended, nonstatutory stock options, stock appreciation rights, restricted stock, restricted stock units and other stock-based and cash-based awards. Up to 3,000,000 shares of our common
stock may be issued pursuant to awards granted under the 2010 Plan, plus an additional amount up to 5,443,833 shares of our common stock underlying awards issued under a predecessor plan that expire or are canceled without the holders receiving any
shares under those awards.

For stock option grants made to new employees upon commencement of employment, awards typically
provide for vesting of 25% of the shares underlying the award at the end of the first year of service with the remaining 75% of the shares underlying the award vesting ratable on a monthly basis over the following three-year period subject to
continued service. Annual grants to existing employees typically provide for monthly vesting over four years.

Compensation Expense

Total stock-based compensation expense, related to all equity awards, for the three and nine months ended September 30, 2010 and 2009 comprised the following:



|                                                             |  |                                 |           |  |                                |   |         |      |  |   |           |  |  |   |           | 
|------------------------------------------------------------ |  | ------------------------------- | --------- |  | ------------------------------ | - | ------- | ---- |  | - | --------- |  |  | - | --------- | 
|                                                             |  | Three Months EndedSeptember 30, |           |  | Nine Months EndedSeptember 30, |  
|                                                             |  | 2010                            |           |  | 2009                           |   |         | 2010 |  |   | 2009      | 
|Effect of stock-based compensation on net loss by line item: |  |                                 |           |  |                                |   |         |      |  |   |           |  |  |   |           | 
|Research and development                                     |  | $                               | 1,000,806 |  |                                | $ | 879,723 |      |  | $ | 2,871,296 |  |  | $ | 2,621,461 | 
|General and administrative                                   |  |                                 | 882,524   |  |                                |   | 898,312 |      |  |   | 2,708,404 |  |  |   | 2,823,386 | 

As of
September 30, 2010, there was approximately $7.9 million of total unrecognized compensation cost, net of estimated forfeitures, related to unvested stock options, which are expected to be recognized over a weighted-average period of 2.3 years.



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During the nine months
ended September 30, 2010, we granted options to purchase 1,516,430 shares of our common stock at a weighted average fair value of $3.59. During the nine months ended September 30, 2009, we granted options to purchase 534,260 shares of
our common stock at a weighted average fair value of $3.71. The fair values were estimated using the Black-Scholes valuation model using the following weighted-average assumptions:



|                                |  |                                 |            |   |                                |  |            |      |  |  |            |   |  |  |            |  
|------------------------------- |  | ------------------------------- | ---------- | - | ------------------------------ |  | ---------- | ---- |  |  | ---------- | - |  |  | ---------- | -
|                                |  | Three Months EndedSeptember 30, |            |   | Nine Months EndedSeptember 30, | 
|                                |  | 2010                            |            |   | 2009                           |  |            | 2010 |  |  | 2009       |  
|Risk-free interest rate         |  |                                 | 1.99       | % |                                |  | 2.89       | %    |  |  | 2.72       | % |  |  | 2.23       | %
|Expected annual dividend yield  |  |                                 |           |   |                                |  |           |      |  |  |           |   |  |  |           |  
|Expected stock price volatility |  |                                 | 58.94      | % |                                |  | 58.65      | %    |  |  | 59.51      | % |  |  | 56.64      | %
|Expected term of options        |  |                                 | 5.76 years |   |                                |  | 5.53 years |      |  |  | 5.72 years |   |  |  | 5.42 years |  

5. Comprehensive Loss

Comprehensive loss is comprised of net loss and other comprehensive income (loss). Other comprehensive income (loss)
includes unrealized holding gains and losses arising during the period on available-for-sale securities that are not other-than-temporarily impaired. For the three and nine months ended September 30, 2010 and 2009, comprehensive loss was as
follows:



|                                                                                                 |  |                                 |             |   |                                |   |            |      |  |   |             |   |  |   |             |  
|------------------------------------------------------------------------------------------------ |  | ------------------------------- | ----------- | - | ------------------------------ | - | ---------- | ---- |  | - | ----------- | - |  | - | ----------- | -
|                                                                                                 |  | Three Months EndedSeptember
30, |             |   | Nine Months
EndedSeptember 30, |  
|                                                                                                 |  | 2010                            |             |   | 2009                           |   |            | 2010 |  |   | 2009        |  
|Net loss                                                                                         |  | $                               | (21,256,721 | ) |                                | $ | (9,325,605 | )    |  | $ | (35,865,991 | ) |  | $ | (24,601,047 | )
|Net unrealized holding gains (losses) on available-for-sale securities arising during the period |  |                                 | (9,252      | ) |                                |   | (228,493   | )    |  |   | 47,676      |   |  |   | (498,431    | )
|                                                                                                 |  |                                 |             |   |                                |   |            |      |  |   |             |   |  |   |             |  
|Total comprehensive loss                                                                         |  | $                               | (21,265,973 | ) |                                | $ | (9,554,098 | )    |  | $ | (35,818,315 | ) |  | $ | (25,099,478 | )
|                                                                                                 |  |                                 |             |   |                                |   |            |      |  |   |             |   |  |   |             |  

Accumulated other comprehensive income (loss) consists of unrealized net gains (losses) on
available-for-sale securities.

6. Cash, Cash Equivalents and Available-for-Sale Securities

The following is a summary of cash, cash equivalents and available-for-sale securities:



|                                                                          |  |                    |             |  |                      |   |         |                       |  |   |                     |   |  |   |             | 
|------------------------------------------------------------------------- |  | ------------------ | ----------- |  | -------------------- | - | ------- | --------------------- |  | - | ------------------- | - |  | - | ----------- | 
|                                                                          |  | September 30, 2010 |            
|                                                                          |  | Cost               |             |  | GrossUnrealizedGains |   |         | GrossUnrealizedLosses |  |   | EstimatedFair Value |  
|Cash and cash equivalents due in 90 days or less                          |  | $                  | 18,180,239  |  |                      | $ | 65      |                       |  | $ |                    |   |  | $ | 18,180,304  | 
|Available-for-sale securities:                                            |  |                    |             |  |                      |   |         |                       |  |   |                     |   |  |   |             | 
|Corporate obligations due in one year or less                             |  |                    | 50,511,502  |  |                      |   | 25,897  |                       |  |   | (13,469             | ) |  |   | 50,523,930  | 
|Mortgage-backed securities due after ten years                            |  |                    | 672,352     |  |                      |   | 68,269  |                       |  |   |                    |   |  |   | 740,621     | 
|U.S. government-sponsored enterprise obligations due in one year or less  |  |                    | 36,973,922  |  |                      |   | 7,530   |                       |  |   |                    |   |  |   | 36,981,452  | 
|U.S. government-sponsored enterprise obligations due in one to five years |  |                    | 3,761,050   |  |                      |   |        |                       |  |   | (3,325              | ) |  |   | 3,757,725   | 
|                                                                          |  |                    |             |  |                      |   |         |                       |  |   |                     |   |  |   |             | 
|Total available-for-sale securities                                       |  |                    | 91,918,826  |  |                      |   | 101,696 |                       |  |   | (16,794             | ) |  |   | 92,003,728  | 
|                                                                          |  |                    |             |  |                      |   |         |                       |  |   |                     |   |  |   |             | 
|Total cash, cash equivalents and available-for-sale securities            |  | $                  | 110,099,065 |  |                      | $ | 101,761 |                       |  | $ | (16,794             | ) |  | $ | 110,184,032 | 
|                                                                          |  |                    |             |  |                      |   |         |                       |  |   |                     |   |  |   |             | 
|                                                                          | 
|                                                                          |  | December 31, 2009  |            
|                                                                          |  | Cost               |             |  | GrossUnrealizedGains |   |         | GrossUnrealizedLosses |  |   | EstimatedFair Value |  
|Cash and cash equivalents due in 90 days or less                          |  | $                  | 16,287,229  |  |                      | $ |        |                       |  | $ |                    |   |  | $ | 16,287,229  | 
|Available-for-sale securities:                                            |  |                    |             |  |                      |   |         |                       |  |   |                     |   |  |   |             | 
|Corporate obligations due in one year or less                             |  |                    | 31,505,149  |  |                      |   | 13,461  |                       |  |   | (205                | ) |  |   | 31,518,405  | 
|U.S. Treasury securities due in one year or less                          |  |                    | 2,268,546   |  |                      |   | 3,684   |                       |  |   |                    |   |  |   | 2,272,230   | 
|Mortgage-backed securities due after ten years                            |  |                    | 699,376     |  |                      |   |        |                       |  |   | (8,870              | ) |  |   | 690,506     | 
|U.S. government-sponsored enterprise obligations due in one year or less  |  |                    | 64,841,354  |  |                      |   | 71,583  |                       |  |   | (494                | ) |  |   | 64,912,443  | 
|U.S. government-sponsored enterprise obligations due in one to five years |  |                    | 15,097,568  |  |                      |   |        |                       |  |   | (41,868             | ) |  |   | 15,055,700  | 
|                                                                          |  |                    |             |  |                      |   |         |                       |  |   |                     |   |  |   |             | 
|Total available-for-sale securities                                       |  |                    | 114,411,993 |  |                      |   | 88,728  |                       |  |   | (51,437             | ) |  |   | 114,449,284 | 
|                                                                          |  |                    |             |  |                      |   |         |                       |  |   |                     |   |  |   |             | 
|Total cash, cash equivalents and available-for-sale securities            |  | $                  | 130,699,222 |  |                      | $ | 88,728  |                       |  | $ | (51,437             | ) |  | $ | 130,736,513 | 
|                                                                          |  |                    |             |  |                      |   |         |                       |  |   |                     |   |  |   |             | 



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At September 30,
2010, we held seven debt securities that had been in an unrealized loss position for less than 12 months. The aggregate unrealized loss on these securities was $16,794 and the fair value was $13,396,340. We evaluated our securities for
other-than-temporary impairments based on quantitative and qualitative factors. We considered the decline in market value for these seven securities to be primarily attributable to current economic conditions. We do not intend to sell these
securities. Additionally, it is not more likely than not that we will be required to sell these securities before the recovery of their amortized cost bases, which may be maturity. Based on our analysis, we do not consider these investments to
be other-than-temporarily impaired at September 30, 2010.

There were no other-than-temporary impairments recognized for
the three and nine months ended September 30, 2010. During the three and nine months ended September 30, 2009, we determined that one debt security was other-than-temporarily impaired and accordingly recorded a loss of $15,666 in our
condensed consolidated statement of operations.

Realized gains on our available-for-sale securities were immaterial for the
three and nine months ended September 30, 2010 and 2009.

7. Fair Value

We use a valuation hierarchy for disclosure of the inputs used to measure fair value. This hierarchy prioritizes the inputs into three
broad levels. Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. Level 2 inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or
liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument. Level 3 inputs are unobservable inputs based on our own assumptions used to measure assets and liabilities at fair
value. The classification of a financial asset or liability within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement. For our fixed income securities, we reference pricing data supplied by
our custodial agent and nationally known pricing vendors, using a variety of daily data sources, largely readily-available market data and broker quotes.

The following table provides the assets carried at fair value measured on a recurring basis as of September 30, 2010:



|                                                   |  |         |            |  |         |   |            | 
|-------------------------------------------------- |  | ------- | ---------- |  | ------- | - | ---------- | 
|                                                   |  | Level 1 |            |  | Level 2 |  
|Cash and cash equivalents                          |  | $       | 18,180,304 |  |         | $ |           | 
|Corporate obligations (including commercial paper) |  |         |           |  |         |   | 50,523,930 | 
|Mortgage-backed securities                         |  |         |           |  |         |   | 740,621    | 
|U.S. government-sponsored enterprise obligations   |  |         |           |  |         |   | 40,739,177 | 
|                                                   |  |         |            |  |         |   |            | 
|Total                                              |  | $       | 18,180,304 |  |         | $ | 92,003,728 | 
|                                                   |  |         |            |  |         |   |            | 

The fair value of the available-for-sale securities and cash and cash equivalents (including asset types
listed below with maturities of three months or less at the time of purchase) is based on the following inputs:



| |  |  | Corporate Obligations:
| | - |  | ----------------------



| |  |  | Commercial paper: calculations by custodian based on three month Treasury bill published on last business day of the month.
| | - |  | ---------------------------------------------------------------------------------------------------------------------------



| |  |  | Other: benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers and reference
data.
| | - |  | ---------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | Mortgage-backed securities: benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities,
bids, offers and reference data, new issue data, monthly payment information and collateral performance.
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | U.S. Treasury securities: benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities,
bids, offers and reference data and vendor trading platform data.
| | - |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



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| |  |  | U.S. government-sponsored enterprise obligations: benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets,
benchmark securities, bids, offers and reference data.
| | - |  | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

We did not change these valuation methods during the
nine months ended September 30, 2010.

8. Collaborations

Purdue and Mundipharma

In November 2008, we entered into strategic
alliance agreements with each of Purdue and Mundipharma to develop and commercialize pharmaceutical products. The alliance includes product candidates that inhibit or target the Hedgehog pathway, fatty acid amide hydrolase, or FAAH,
phosphoinositide-3-kinase, or PI3K, and product candidates arising out of all our discovery projects in all disease fields that are identified in the last research plan we submit to Mundipharma prior to December 31, 2011 (with Mundipharma
having the right, through the exercise of two consecutive one-year options, to extend such period through December 31, 2013). We refer to such three to five year period as the funded discovery period. Our heat shock protein 90, or Hsp90, and
Bcl-2 programs are expressly excluded from the alliance. The agreement with Purdue is focused on the development and U.S. commercialization of products targeting FAAH. The agreement with Mundipharma is focused on the development and
commercialization outside of the United States of all products and product candidates covered by the alliance, including those targeting FAAH. Following entry into the strategic alliance agreements in November 2008, we consider Mundipharma, Purdue
and associated entities to be related parties for financial reporting purposes because of their equity ownership.

Under the
strategic alliance agreements, we have responsibility and decision-making authority for the performance of early discovery projects and the development of all product candidates on a worldwide basis. There are no joint steering or similar committees
for the alliance. In October 2010, Mundipharma and Purdue exercised their rights to assume worldwide development and commercialization activities for products arising out of the FAAH project and will fund 100% of all subsequent research, development
and commercialization expenses. Mundipharma is obligated to pay 100% of our contractually budgeted amounts for research and development expenses incurred by us for all other programs included in the alliance until the later of December 31, 2013
and the commencement of the first Phase 3 clinical trial of such product candidate, which we refer to as the transition date. The contractually budgeted amount for the period between November 19, 2008 and December 31, 2009 was $50 million
and the contractually budgeted amounts for the years ending December 31, 2010 and 2011 are $65 million and $85 million, respectively. We have the right to exceed the contractually budgeted amount at our own expense, which we expect to be the
case for 2010 due primarily to the license of our PI3K inhibitor program. Any activities we conduct related to the transition of the FAAH program to Purdue and Mundipharma will be reimbursed in addition to the contractually budgeted amount. After
the transition date for each product candidate, we will share with Mundipharma all research and development costs for such product candidate equally. Mundipharma has the right to opt out of any early discovery project or any preclinical or clinical
development program on an annual basis in November of each year. In the event of an opt-out decision, Mundipharma will continue to provide funding for, in the aggregate, 100% of our contractually budgeted research and development expenses for all
programs included in the alliance for the calendar year following the date of such opt out. In addition, we and Mundipharma each have the right to opt out of continued development of a product candidate after it has reached the transition date, with
a one year tail funding obligation for its 50% of post-transition date research and development expenses. If a party exercises its right to opt out of the development of a product or product candidate after the transition date, the other party may
elect to continue the development and assume responsibility for the worldwide commercialization of such product or product candidate, subject to the payment of a royalty.

We are recognizing revenue for reimbursed research and development services we perform for Mundipharma and Purdue. We recognized $21.5 million and $54.4 million in such revenue in the three and nine month
periods ended September 30, 2010, respectively. We recognized $13.1 million and $34.2 million in such revenue in the three and nine month periods ended September 30, 2009, respectively. In the first month of each quarter, Purdue and
Mundipharma each prepay 25% of the annual agreed upon research and development service amount, which we record as deferred revenue and recognize as revenue as expenses are incurred over the period of effort.

In connection with the entry into the strategic alliance agreements in November 2008, we also entered into a securities purchase
agreement and line of credit agreement with Purdue and its independent associated company, Purdue Pharma L.P. (PPLP). In March 2009, Purdue assigned its interest under the line of credit agreement to PPLP. Under the securities purchase
agreement we issued and sold in a first equity closing in November 2008 an aggregate of four million shares of our common stock at a purchase price of $11.25 per share, for an aggregate purchase price of $45 million. Of such shares, two million
shares of our common stock were purchased by each purchaser. In January 2009, we conducted a second equity closing where we issued and sold an aggregate of two million shares of our common stock and warrants to purchase up to an aggregate of six
million shares of our common stock, for an aggregate purchase price of $30 million. An equal number of shares and warrants were purchased by each purchaser. Warrants for 1,000,000 shares of our common stock expired unexercised on July 1, 2010.

The remaining warrants are currently exercisable for:



| |  |  | 2,000,000 shares of our common stock at any time up to July 1, 2011, with an initial exercise price of $22.50 per share, with such exercise price
increasing over time depending on when such warrants are exercised, up to a maximum exercise price of $30.00 per share; and
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



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| |  |  | 3,000,000 shares of our common stock at any time up to July 2, 2012, with an initial exercise price of $30.00 per share, with such exercise price
increasing over time depending on when such warrants are exercised, up to a maximum exercise price of $40.00 per share.
| | - |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

The
fair value of these warrants was estimated as of November 2008 using a binomial valuation model assuming no expected dividends, a volatility of 58%, contractual lives ranging from 1.6 years to 3.6 years and risk-free interest rates ranging from of
1.0% to 1.5%. The aggregate fair value of these warrants of approximately $1.3 million was recorded as additional paid-in capital in the nine months ended September 30, 2009.

In November 2008, for financial statement purposes we recorded $23.8 million as deferred revenue associated with the grant of rights and
licenses to Mundipharma and Purdue. This amount represented the excess of the amount paid by Purdue and PPLP for the four million shares of our common stock ($11.25 per share) over the closing market price on the day before the first equity closing
($5.29 per share). In 2008, we considered our obligation, absent material adverse changes, to issue Purdue and PPLP the second closing securities as a forward contract with immaterial intrinsic value, which was recorded in stockholders equity.
This forward contract closed in January 2009 upon the issuance of the second closing securities. In January 2009, for financial statement purposes, we recorded $18.2 million as deferred revenue associated with the grant of rights and licenses to
Mundipharma and Purdue representing the excess of the $30 million paid by Purdue and PPLP for the second closing securities over the fair market value of these securities ($5.29 per share for the common stock and approximately $1.3 million for the
warrants) as of the day before the first equity closing.

Since the shares of our common stock were purchased by Purdue and
PPLP at a premium to the closing stock price on November 19, 2008, and the fair value of the rights and licenses transferred as part of the collaboration arrangement could not be reliably determined, we have attributed the premium over the
closing price of our common stock using the residual method to the grant of rights and licenses to Mundipharma and Purdue. There is no obligation for us to repay the $42.0 million allocated to the grant of rights and licenses and we are recognizing
this $42.0 million in deferred revenue ratably over 14 years, which is our estimated period of performance under the arrangement. We periodically review this estimate and make adjustments as facts and circumstances dictate. We recognized $0.7
million in such revenue in the three months ended September 30, 2010 and 2009 and $2.2 million in such revenue in the nine months ended September 30, 2010 and 2009.

The line of credit agreement provides for the borrowing by us of one or more unsecured loans up to an aggregate maximum principal amount of $50 million. The loans may be drawn by us through March 31,
2012. The loans, which may be used by us for any proper corporate purpose, mature on April 1, 2019 and will be subordinate to any senior indebtedness that we may incur. Borrowings made under the line of credit agreement will bear interest,
payable on the maturity date, at a fluctuating rate set at the prime rate on the business day prior to the funding of each loan and will be reset on the last business day of each month ending thereafter. Interest will be compounded on each
successive three-month anniversary of the funding of each loan. Outstanding loans may be prepaid without penalty or premium prior to the maturity date. Amounts borrowed under the credit agreement, once borrowed, may not be borrowed again. We have
certain rights to repay outstanding amounts under the line of credit agreement in shares of our common stock.

Intellikine

In July 2010, we entered into a development and license agreement with Intellikine under which we obtained rights to discover, develop and commercialize pharmaceutical products targeting the delta and/or
gamma isoforms of PI3K, including IPI-145. We are obligated to pay Intellikine $13.5 million in initial license payments, which is included as research and development expense in the three and nine months ended September 30, 2010. In addition,
we are obligated to fund research activities conducted by Intellikine under a two year research program to identify additional novel delta, gamma and dual delta/gamma-specific inhibitors of PI3K for future development. We are recognizing these costs
as research and development expense as they are incurred. We may extend the research program for an additional year upon written notice to Intellikine at least 180 days prior to the last day of the initial two-year research term. We are also
obligated to pay up to $25 million in success-based milestones for the development of two distinct product candidates, and up to $450 million in success-based milestones for the approval and commercialization of two distinct products. In addition,
we are obligated to pay Intellikine tiered royalties ranging from single digits to low teens upon successful commercialization of products licensed to us, which are payable until the later to occur of the last-to-expire of specified patent rights
and the expiration of non-patent regulatory exclusivities in a country, subject to reduction in certain circumstances.

Under
the agreement, we obtained rights to direct all development and commercialization activities worldwide for products arising from the agreement for all therapeutic indications. Mundipharma has commercialization rights outside the United States for
products arising out of our PI3K inhibitor program. For a product directed primarily to an oncology indication, Intellikine will have the option, at the end of Phase 2 clinical development and upon payment of an option fee, to convert its royalty
interest in U.S. sales into the right to share in 50% of profits and losses on U.S. development and commercialization, and to participate in up to 30% of the detailing effort for these products in the United States.



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Intellikine may
terminate its participation rights in any oncology product with twelve months prior written notice to us, after which Intellikines participation rights would revert back to the original milestone- and royalty-based payment structure,
provided that Intellikine would not be entitled to receive royalty payments for net sales occurring prior to the termination date and certain specified milestone payments.

Other than pursuant to the agreement, neither we nor Intellikine may research, develop or commercialize products directed to the PI3K delta and/or gamma isoforms which meet certain selectivity criteria.

The agreement expires when the parties have no further obligations to each other thereunder, unless earlier terminated.
Either party may terminate the agreement on 75 days prior written notice if the other party materially breaches the agreement and fails to cure such breach within the applicable notice period, provided that the notice period is reduced to
30 days where the alleged breach is non-payment. Intellikine may terminate the agreement immediately upon written notice if we fail to make the initial license payments. Additionally, Intellikine may terminate the agreement upon 30 days prior
written notice if we or a related party bring an action challenging the validity of any of the licensed patents, provided that we have not withdrawn such action before the end of the 30-day notice period. We may terminate the agreement at any time
upon 180 days prior written notice provided after the end of the research term.

MedImmune/AZ

In August 2006, we entered into a product development and commercialization agreement with MedImmune, Inc., an affiliate of
AstraZeneca plc (MedImmune/AZ), to jointly develop and commercialize cancer drugs targeting Hsp90 and the Hedgehog pathway. Under the terms of this agreement, we shared equally with MedImmune/AZ all development costs, as well as
potential profits and losses, from any future marketed products. In November 2007, we regained from MedImmune/AZ worldwide development and commercialization rights under our Hedgehog pathway program on a royalty-free basis. In December 2008, we
regained from MedImmune/AZ worldwide development and commercialization rights under our Hsp90 chaperone inhibitor program, subject to the payment of single-digit royalties on worldwide net sales, if any, of each of IPI-504 and IPI-493. In January
2009, we reached an agreement with MedImmune/AZ to settle the residual funding obligation remaining for 2009 through lump-sum payments totaling $12.5 million, which were recorded as income from residual funding after reacquisition of Hsp90 program
(a component of other income) in the nine months ended September 30, 2009. We received $12.5 million in cash from MedImmune/AZ in the nine months ended September 30, 2009.

Novartis

In February 2006, we entered into a collaboration agreement with Novartis Institute for BioMedical Research, Inc., or Novartis, to discover, develop and commercialize drugs targeting Bcl protein family
members for the treatment of a broad range of cancers. Under the terms of this agreement, we granted to Novartis an exclusive, worldwide license to research, develop and commercialize pharmaceutical products that are based upon our proprietary Bcl
inhibitors. Novartis paid us an up-front license fee, an affiliate of Novartis made an equity investment in us, and Novartis provided us research funding over the initial two-year research term, which expired in February 2008. Novartis chose not to
exercise its right to extend the research term for up to two additional one-year terms; thus, the research term ended in February 2008 and we have no further performance obligations to Novartis. We may request to participate in clinical development
of any products arising from this collaboration and, if such request is agreed upon by Novartis, Novartis will fund agreed-upon development costs that are incurred by us. We also have a non-exclusive right to detail Bcl-2 family inhibitor products
in the United States, with our detailing costs to be reimbursed by Novartis. Novartis has agreed to make milestone payments to us totaling over $370 million if certain specified research, development and commercialization milestones are achieved for
multiple products for multiple indications. Novartis has also agreed to pay us tiered royalties ranging from single-digits to teens upon successful commercialization of any products developed under the alliance. Novartis has the right to terminate
the agreement at any time upon 60 days prior written notice. In addition, Novartis has the right to terminate the agreement in connection with a material breach by us that remains uncured for a period of 120 days after notice. We can terminate
specified programs under the agreement as to breaches by Novartis relating solely to such programs that remain uncured for a period of 120 days after notice or can terminate the agreement in its entirety in connection with a material breach by
Novartis of the agreement that remains uncured for a period of 120 days after notice. The agreement shall expire when the parties thereto have no further obligations to each other thereunder unless earlier terminated as described above.

9. Loan Commitment Asset from Purdue Entities

In connection with the strategic alliance with Purdue and Mundipharma, we also entered into a line of credit agreement with Purdue and PPLP. The extension of the line of credit at an interest rate below
our incremental borrowing rate represented the transfer of additional value to us in the arrangement. As such, we recorded this additional value as a loan commitment asset at its fair value of $17.3 million on our balance sheet in 2008. The fair
value of the loan commitment asset was determined using a discounted cash flow model of the differential between the terms and rates of the line of credit and market rates. The loan commitment asset is measured at fair value on a nonrecurring basis
and will only be re-measured at fair value for nonrecurring events such as an impairment loss. Because Mundipharma, Purdue and associated entities are related parties (See Note 8), we recorded the offset to this asset as additional paid-in capital
in 2008.



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We are amortizing this
asset to interest expense over the life of the loan arrangement, or 10 years commencing on April 1, 2009, the date we could begin drawing on the line. We recorded approximately $0.4 million and $1.3 million of related amortization expense in
the three and nine months ended September 30, 2010, respectively. We recognized approximately $0.4 million and $0.9 million of related amortization expense in the three and nine months ended September 30, 2009, respectively. As of
September 30, 2010, no amounts have been borrowed under this line of credit.

10. Accrued Expenses

Accrued expenses consisted of the following:



|                                           |  |                   |            |  |                  |   |           | 
|------------------------------------------ |  | ----------------- | ---------- |  | ---------------- | - | --------- | 
|                                           |  | September 30,2010 |            |  | December 31,2009 |  
|Accrued drug manufacturing costs           |  | $                 | 5,546,382  |  |                  | $ | 2,212,156 | 
|Accrued license fee payable to Intellikine |  |                   | 8,500,000  |  |                  |   |          | 
|Accrued compensation and benefits          |  |                   | 4,043,439  |  |                  |   | 2,576,970 | 
|Accrued clinical studies                   |  |                   | 2,358,378  |  |                  |   | 920,429   | 
|Other                                      |  |                   | 3,273,110  |  |                  |   | 2,839,827 | 
|                                           |  |                   |            |  |                  |   |           | 
|Total accrued expenses                     |  | $                 | 23,721,309 |  |                  | $ | 8,549,382 | 
|                                           |  |                   |            |  |                  |   |           | 

11. Income Taxes

During the three months ended September 30, 2010, we recorded an income tax benefit of $700,321 as an uncertain tax position we took in a prior year is no longer subject to examination due to the
expiration of the statute of limitations.

12. Income from NIH Reimbursement

During the nine months ended September 30, 2009, we received $1.7 million from the National Institutes of Health, or NIH, relating to
contract work performed by Discovery Partners International, Inc. from August 2004 through June 2006. As the amount received is not related to our ordinary course of operations, we have recorded the amount as other income.



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

Forward-Looking Information

The following discussion of our financial condition and results of operations should be read in conjunction with our condensed consolidated financial statements and related notes included elsewhere in
this report. Some of the information contained in this discussion and analysis and set forth elsewhere in this report, including information with respect to our plans and strategy for our business, includes forward-looking statements that involve
risks and uncertainties. You should review the section titled Risk Factors in Part II of this report for a discussion of important factors that could cause actual results to differ materially from the results described in or implied by
the forward-looking statements contained in the following discussion and analysis.

Business Overview

We are a drug discovery and development company that is utilizing our strength in small molecule drug technologies to
discover and develop medicines for difficult to treat diseases. Our discovery program has generated four clinical stage drug candidates spanning programs in the inhibition of heat shock protein 90, or Hsp90, chaperone system, the Hedgehog signaling
pathway and fatty acid amide hydrolase, or FAAH. In July 2010, we also obtained global development and commercialization rights to develop inhibitors of the delta and gamma isoforms of phosphoinositide-3-kinase, or PI3K.

Hsp90 Chaperone Inhibitor Program.Hsp90 plays a role in regulating the stability of key cancer-causing proteins through
its role as a protein chaperone. Proteins chaperoned by Hsp90, known as client proteins, include cancer-causing forms of ALK, BCR-ABL, EGFR, FLT3, and HER2. Inhibition of the Hsp90 chaperone knocks out a critical source of support for cancer cells,
leading to tumor growth inhibition and cancer cell death. Thus, Hsp90 chaperone inhibition may represent an important approach to treating certain cancers. We are developing two drug candidates in our Hsp90 chaperone inhibitor program: IPI-504
(retaspimycin hydrochloride), an intravenously-administered small molecule, and IPI-493, which is administered orally. We are conducting various clinical and preclinical studies of IPI-504 and IPI-493. These studies are focused on establishing a
dose and schedule of administration that optimizes safety and efficacy of these candidates, and identifying patient populations, or subpopulations, most likely to benefit from Hsp90 chaperone inhibition. If these studies do not yield results we
believe are necessary to warrant further development, we may elect to discontinue further development of the applicable drug candidate.

In June 2010, we reported final data from a Phase 2 clinical trial of IPI-504 in patients with advanced non-small cell lung cancer, or NSCLC, which showed an objective response rate of seven percent in
the overall study population of 78 patients: ten percent in patients who were epidermal growth factor receptor, or EGFR, wild-type, four percent in those with EGFR mutations, and 12 percent among KRAS wild-type patients. Among the patients with
anaplastic lymphoma kinase, or ALK, gene rearrangements, there was a 67 percent response rate, with two of three patients experiencing partial responses and the third patient experiencing a 24 percent disease reduction, all three of whom received
IPI-504 for at least six months. IPI-504 was generally well tolerated in this study. Validation of these findings is ongoing in an investigator-sponsored trial at Massachusetts General Hospital by Dr. Lecia Sequist, the principal investigator
of the Phase 2 study. Also in patients with advanced NSCLC, we are continuing to evaluate patients in a Phase 1b clinical trial of IPI-504 in combination with Taxotere® (docetaxel).

In
addition, we completed an interim review of data from the first cohort of patients enrolled in a Phase 2 clinical trial evaluating IPI-504 in combination with Herceptin® (trastuzumab) in patients with HER2-positive metastatic breast cancer. This review showed that IPI-504 was well-tolerated when administered at 300 mg/m2once weekly in combination with trastuzumab in this heavily
pre-treated patient population. Clinical activity was also observed at this dose and schedule, but it was insufficient to satisfy our rigorous stage gate for continuation of this study. While we believe that the insufficient clinical activity in
this study was the result of IPI-504 being administered at a less than optimal dose in this combination, we do not intend to continue development of IPI-504 in breast cancer in light of the evolving therapeutic landscape. We expect to present data
from this clinical trial at a medical meeting in 2011.

We are evaluating IPI-493 in two Phase 1, dose escalation studies to
determine the optimal dose and schedule for future development. One study is designed to assess the safety, tolerability, pharmacokinetic parameters and pharmacodynamic markers of biological activity of IPI-493 in patients with advanced hematologic
malignancies. The second study is being conducted in patients with advanced solid tumors. We anticipate reporting data from our Hsp90 development programs and articulating future development programs, based on data from our ongoing clinical trials
and relevant preclinical data in 2011.

We have worldwide development and commercialization rights for our Hsp90 chaperone
inhibitor program, which includes IPI-504 and IPI-493, subject to the payment to our former partner, MedImmune, Inc., an affiliate of AstraZeneca plc, of a single-digit royalty on net sales of IPI-504 and IPI-493. We refer to MedImmune, Inc. in this
report as MedImmune/AZ.

Hedgehog Pathway Inhibitor Program.The lead candidate in our Hedgehog signal
transduction pathway, or Hedgehog pathway, program is IPI-926. Malignant activation of the Hedgehog



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pathway is believed to be responsible for a broad range of cancers through three distinct mechanisms: signaling to the tumor microenvironment, signaling to tumor progenitor cells, and genetic
activation of the Hedgehog pathway in tumor cells. IPI-926 is a novel, orally available small molecule that inhibits Smoothened, or Smo, a key component of the Hedgehog pathway. By disrupting malignant activation of the pathway, Smo inhibition
represents a significant opportunity for addressing a number of difficult-to-treat cancers, including pancreatic, prostate, small cell lung, breast and blood cancers, as well as certain skin and brain cancers. IPI-926 has demonstrated anti-tumor
activity in numerous preclinical models.

In April 2010, we initiated a randomized Phase 1b/2 clinical trial evaluating
IPI-926 in combination with gemcitabine in patients with pancreatic cancer. The Phase 1b portion of the study is a dose-escalation evaluating once-daily oral administration of IPI-926 and weekly intravenous administration of gemcitabine. The Phase 2
portion of this trial is set to commence once the recommended Phase 2 doses for IPI-926 and gemcitabine have been established. The Phase 2 portion of the trial is an international, multi-center, randomized, double-blind trial evaluating
approximately 120 patients with pancreatic cancer. The primary endpoint of the Phase 2 portion of the trial is overall survival. Secondary endpoints include progression free survival, time to progression, and overall response rate.

In October 2010, we presented preliminary results from a Phase 1 study of IPI-926, which showed that IPI-926 was well tolerated and
demonstrated clinical activity in patients with basal cell carcinoma, or BCC. At the time of the data presentation, 60 patients had been enrolled, including 24 patients with BCC. In the BCC cohort, 17 patients were enrolled who were naïve to
treatment with a Hedgehog pathway inhibitor. To date, four clinical partial responses have been observed in this group of patients. As the majority of patients with BCC have undergone treatment for less than 24 weeks, more time on study will be
required to fully assess the clinical activity of IPI-926 in patients with BCC. Only one patient with BCC naïve to treatment with a Hedgehog pathway inhibitor has discontinued from the study due to progression of disease, and this patient was
on trial for more than 18 months. Among patients with non-BCC solid tumors enrolled in the study, three patients have shown stable disease for at least six months. We continue to enroll patients in this Phase 1 study. Mundipharma International
Corporation Limited, or Mundipharma, has commercialization rights outside of the United States for products arising out of our Hedgehog pathway inhibitor program.

FAAH Inhibitor Program. We also have a program directed to FAAH, an emerging target for neuropathic pain. The enzyme FAAH degrades anandamide, which is a neurotransmitter that produces a
pain relieving effect in response to pain and nerve injury. FAAH inhibition is believed to increase the duration of anandamides effect, prolonging pain relief at the site of release. Our lead candidate in this program is IPI-940, a novel,
orally available inhibitor of FAAH with potential application for the treatment of a broad range of painful conditions and inflammatory diseases. IPI-940 is currently in Phase 1 clinical development. The objectives of our Phase 1 development program
are to evaluate the safety, tolerability, and pharmacokinetic and pharmacodynamic properties of IPI-940. In October 2010, Mundipharma and its independent associated company Purdue Pharmaceutical Products L.P., or Purdue, exercised their rights to
assume worldwide development and commercialization activities for products arising out of the FAAH project and will fund 100% of all subsequent research, development and commercialization expenses.

PI3K Inhibitor Program.In July 2010, we entered into a development and license agreement with Intellikine, Inc., or
Intellikine, under which we obtained global development and commercialization rights to Intellikines portfolio of inhibitors targeting the delta and/or gamma isoforms of PI3K. The PI3Ks are a family of enzymes involved in cellular functions,
including cell proliferation and survival, cell differentiation, intracellular trafficking and immunity, providing multiple opportunities to develop differentiated therapies against inflammatory and autoimmune diseases as well as hematologic
cancers. Our lead compound in this program, IPI-145, is an orally-available, small molecule, dual-selective inhibitor of PI3Kdelta and PI3Kgamma. We intend to commence clinical development of IPI-145 in 2011. Mundipharma has commercialization rights
outside the United States for products arising out of our PI3K inhibitor program.

We have spent, and expect to continue to
spend, significant resources to fund the research and development of IPI-504, IPI-493, IPI-926, IPI-940, IPI-145 and our other drug candidates. While we may have net income in future periods as the result of non-recurring collaboration income, we
expect to incur substantial operating losses over the next several years as our clinical trial and drug manufacturing activities increase.

Collaboration Agreements

Purdue and Mundipharma. In
November 2008, we entered into strategic alliance agreements with each of Purdue and Mundipharma to develop and commercialize pharmaceutical products. The alliance includes product candidates that inhibit or target the Hedgehog pathway, FAAH,
PI3K, and product candidates arising out of all our discovery projects in all disease fields that are identified in the last research plan we submit to Mundipharma prior to December 31, 2011 (with Mundipharma having the right, through the
exercise of two consecutive one-year options, to extend such period through December 31, 2013). We refer to such three to five year period as the funded discovery period. Our Hsp90 and Bcl-2 programs are expressly excluded from the alliance.
The agreement with Purdue is focused on the development and U.S. commercialization of products targeting FAAH. The agreement with Mundipharma is focused on the development and commercialization outside of the United States of all products and
product candidates covered by the alliance, including those targeting FAAH. Following entry into the strategic alliance agreements in November 2008, we consider Mundipharma, Purdue and associated entities to be related parties for financial
reporting purposes because of their equity ownership.

Under the strategic alliance agreements, we have responsibility and
decision-making authority for the performance of early discovery projects and the development of all product candidates on a worldwide basis. There are no joint steering or similar



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committees for the alliance. In October 2010, Mundipharma and Purdue exercised their rights to assume worldwide development and commercialization activities for products arising out of the FAAH
project and will fund 100% of all subsequent research, development and commercialization expenses. Mundipharma is obligated to pay 100% of our contractually budgeted amounts for research and development expenses incurred by us for all other programs
included in the alliance until the later of December 31, 2013 and the commencement of the first Phase 3 clinical trial of such product candidate, which we refer to as the transition date. The contractually budgeted amount for the period between
November 19, 2008 and December 31, 2009 was $50 million and the contractually budgeted amounts for the years ended December 31, 2010 and 2011 are $65 million and $85 million, respectively. We have the right to exceed the contractually
budgeted amount at our own expense, which we expect to be the case for 2010 due primarily to the license of our PI3K inhibitor program. Any activities we conduct related to the transition of the FAAH program to Purdue and Mundipharma will be
reimbursed in addition to the contractually budgeted amount. After the transition date for each product candidate, we will share with Mundipharma all research and development costs for such product candidate equally. We are recognizing revenue for
reimbursed research and development services we perform for Mundipharma and Purdue. We recognized $21.5 million and $54.4 million in such revenue in the three and nine months ended September 30, 2010, respectively. We recognized $13.1 million
and $34.2 million in such revenue in the three and nine months ended September 30, 2009, respectively.

Mundipharma has
the right to opt out of any early discovery project or any preclinical or clinical development program on an annual basis in November of each year. In the event of an opt-out decision, Mundipharma will continue to provide funding for, in the
aggregate, 100% of our contractually budgeted research and development expenses for all programs included in the alliance for the calendar year following the date of such opt out. In addition, we and Mundipharma each have the right to opt out of
continued development of a product candidate after it has reached the transition date, with a one year tail funding obligation for its 50% of post-transition date research and development expenses. If a party exercises its right to opt out of the
development of a product or product candidate after the transition date, the other party may elect to continue the development and assume responsibility for the worldwide commercialization of such product or product candidate, subject to the payment
of a royalty.

Except as set forth above with respect to FAAH products and opt-out products, we will have the right and
responsibility to market and sell products arising from the alliance in the United States and Mundipharma will have the right and responsibility to market and sell products arising from the alliance outside of the United States. Other than pursuant
to the strategic alliance agreements, neither we, Purdue nor Mundipharma may develop, manufacture or commercialize products that arise out of the research program or products that are directed to the same target or pathway as a product included in
the research program, unless and until a party terminates its rights with respect to such products.

If we in-license any
product or product candidate during the funded discovery period for which GLP (Good Laboratory Practice) toxicology studies have been initiated and commercialization rights outside of the United States are available for grant by us to Mundipharma,
Mundipharma will have the option to include such in-licensed product or product candidate in the alliance by paying us a prescribed percentage of the up-front license fee or other acquisition cost, which percentage could be up to 60% of such fee or
cost, in order for Mundipharma to obtain commercialization rights for such in-licensed product or product candidate in all countries outside of the United States, and by funding research and development costs in the same manner as products or
product candidates arising out of our internal discovery programs. The agreement with Mundipharma provides for the agreed-upon research and development budgets to be updated to reflect the inclusion of any in-licensed products or product candidates.
There will be no royalties paid between the parties on in-licensed candidates. If we in-license any product or product candidate during the funded discovery period for which GLP toxicology studies have not been initiated, such products are included
in the alliance as having arisen out of our discovery projects.

Except with respect to products that have been in-licensed by
us, for which no royalties will be payable between the parties, we are obligated to pay Mundipharma a 5% royalty on net sales of the commercialized products until such time as Mundipharma has recovered all research and development expenses paid to
us under the research program prior to the applicable transition date. After such cost recovery, we are obligated to pay a tiered, 1% to 3% royalty on U.S. net sales of those products. For products in which Mundipharma has opted-out of development
prior to the transition date, we are obligated to pay royalties of 1% to 5% of worldwide net sales as a function of the stage of development of the applicable product candidate at the time of opt-out. For products in which either party has opted-out
of development following the transition date, the commercializing party is obligated to pay the other party a 5% royalty on net sales. Mundipharma is obligated to pay us a tiered, 10% to 20% royalty on annual net sales outside of the United States
of each product arising out of the alliance, and Purdue is obligated to pay us a tiered, 10% to 20% royalty on annual net sales of FAAH products in the United States. Royalties are payable until the later to occur of the last-to-expire of specified
patent rights and the expiration of non-patent regulatory exclusivities in a country, provided that if royalties are payable solely on the basis of non-patent regulatory exclusivity, each of the rates above is reduced by one-half. In addition, all
royalties payable under the strategic alliance agreements, whether by us, Purdue or Mundipharma, are subject to reduction on account of third party royalty payments or patent litigation damages or settlements, with any such reductions capped at 50%
of the amounts otherwise payable during the applicable royalty payment period. Each of the strategic alliance agreements expire when the parties thereto have no further obligations to each other thereunder. Either party may terminate the strategic
alliance agreement to which it is a party on 60 days prior written notice if the other party materially breaches the agreement and fails to cure such breach within the 60-day notice period. The agreements may also be terminated by Purdue or
Mundipharma in the event of a change in control of Infinity or in the event that, during the funded research period, (i) Julian Adams is no longer a full-time executive of Infinity, or (ii) both Steven H. Holtzman and Adelene Q. Perkins
are no longer full-time executives of Infinity. Upon termination of either strategic alliance agreement by us or either Purdue or Mundipharma, either party to the other strategic alliance agreement may terminate that agreement.

In connection with the entry into the strategic alliance agreements, we also entered into a securities purchase agreement and line of
credit agreement with Purdue and its independent associated company, Purdue Pharma L.P., or PPLP. In March 2009, Purdue



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assigned its interest under the line of credit agreement to PPLP. Under the securities purchase agreement we issued and sold in a first equity closing in November 2008 an aggregate of four
million shares of our common stock at a purchase price of $11.25 per share, for an aggregate purchase price of $45 million. Of such shares, two million shares of our common stock were purchased by each purchaser. In January 2009, we conducted a
second equity closing where we issued and sold an aggregate of two million shares of our common stock, and warrants to purchase up to an aggregate of six million shares of our common stock, for an aggregate purchase price of $30 million. Of the
second closing securities, an equal number were purchased by each purchaser.

In 2008, we recorded $23.8 million as deferred
revenue associated with the grant of rights and licenses to Mundipharma and Purdue. This amount represented the excess of the amount paid by Purdue and PPLP for our common stock ($11.25 per share) over the closing market price on the day before the
first equity closing ($5.29 per share). In 2008, we considered our obligation, absent material adverse changes, to issue Purdue and PPLP the second closing securities to be a forward contract with immaterial intrinsic value, which was recorded in
stockholders equity. This forward contract closed in January 2009 upon the issuance of the second closing securities. In January 2009, we recorded $18.2 million as deferred revenue associated with the grant of rights and licenses to
Mundipharma and Purdue, representing the excess of the $30 million paid by Purdue and PPLP for the second closing securities over the fair market value of these securities ($5.29 per share for the common stock and approximately $1.3 million for the
warrants) as of the day before the first equity closing.

Since the shares of our common stock were purchased by Purdue and
PPLP at a premium to the closing stock price on November 19, 2008, and the fair value of the rights and licenses transferred as part of the collaboration arrangement could not be reliably determined, we have attributed the premium over the
closing price of our common stock using the residual method to the grant of rights and licenses to Mundipharma and Purdue. There is no obligation for us to repay the $42.0 million allocated to the grant of rights and licenses and we are recognizing
this $42.0 million in deferred revenue ratably over 14 years, which is our estimated period of performance under the arrangement. We will periodically review this estimate and make adjustments as facts and circumstances dictate. We recognized $0.7
million in such revenue in the three months ended September 30, 2010 and 2009 and $2.2 million in such revenue in the nine months ended September 30, 2010 and 2009.

The line of credit agreement provides for the borrowing by us of one or more unsecured loans up to an aggregate maximum principal amount of $50 million. The loans may be drawn by us during the three-year
period that began on April 1, 2009. The loans, which may be used by us for any proper corporate purpose, mature on April 1, 2019, which we refer to as the maturity date, and will be subordinate to any senior indebtedness that we may incur.
Borrowings made under the line of credit agreement will bear interest, payable on the maturity date, at a fluctuating rate set at the prime rate on the business day prior to the funding of each loan and will be reset on the last business day of each
month ending thereafter. Interest will be compounded on each successive three-month anniversary of the funding of each loan. Outstanding loans may be prepaid without penalty or premium prior to the maturity date. Amounts borrowed under the credit
agreement, once borrowed, may not be borrowed again. We have certain rights to repay outstanding amounts under the line of credit agreement in shares of our common stock.

The extension of the line of credit at an interest rate below our incremental borrowing rate represented the transfer of additional value to us in the arrangement. As such, we recorded the fair value of
the line of credit of $17.3 million as a loan commitment asset on our balance sheet in 2008. We began amortizing this asset to interest expense over the life of the loan arrangement, or 10 years, on April 1, 2009. We recorded approximately $0.4
million and $1.3 million of related amortization expense in the three and nine months ended September 30, 2010, respectively. We recorded approximately $0.4 million and $0.9 million of related amortization expense in the three and nine months
ended September 30, 2009. Because Mundipharma, Purdue and associated entities are related parties (See Note 8), we recorded the offset to this asset as additional paid-in capital in 2008. As of September 30, 2010, no amounts have been
borrowed under this line of credit.

Intellikine.In July 2010, we entered a development and license agreement
with Intellikine under which we obtained rights to discover, develop and commercialize pharmaceutical products targeting the delta and/or gamma isoforms of PI3K, including IPI-145. We are obligated to pay Intellikine $13.5 million in initial license
payments, which is included as research and development expense in the three and nine months ended September 30, 2010. In addition, we are obligated to fund research activities conducted by Intellikine under a two year research program to
identify additional novel delta, gamma and dual delta/gamma-specific inhibitors of PI3K for future development. We are recognizing these costs as research and development expense as they are incurred. We may extend the research program for an
additional year upon written notice to Intellikine at least 180 days prior to the last day of the initial two-year research term. We are also obligated to pay up to $25 million in success-based milestones for the development of two distinct product
candidates, and up to $450 million in success-based milestones for the approval and commercialization of two distinct products. In addition, we are obligated to pay Intellikine tiered royalties ranging from single digits to low teens upon successful
commercialization of products licensed to us, which are payable until the later to occur of the last-to-expire of specified patent rights and the expiration of non-patent regulatory exclusivities in a country, subject to reduction in certain
circumstances.

Under the agreement, we obtained rights to direct all development and commercialization activities worldwide
for products arising from the agreement for all therapeutic indications. Mundipharma has commercialization rights outside the United States for



17



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##### Table of Contents

products arising out of our PI3K inhibitor program. For a product directed primarily to an oncology indication, Intellikine will have the option, at the end of Phase 2 clinical development and
upon payment of an option fee, to convert its royalty interest in U.S. sales into the right to share in 50% of profits and losses on U.S. development and commercialization, and to participate in up to 30% of the detailing effort for these products
in the United States.

Intellikine may terminate its participation rights in any oncology product with twelve months
prior written notice to us, after which Intellikines participation rights would revert back to the original milestone- and royalty-based payment structure, provided that Intellikine would not be entitled to receive royalty payments for net
sales occurring prior to the termination date and certain specified milestone payments.

Other than pursuant to the agreement,
neither we nor Intellikine may research, develop or commercialize products directed to the PI3K delta and/or gamma isoforms which meet certain selectivity criteria.

The agreement expires when the parties have no further obligations to each other thereunder, unless earlier terminated. Either party may terminate the agreement on 75 days prior written notice
if the other party materially breaches the agreement and fails to cure such breach within the applicable notice period, provided that the notice period is reduced to 30 days where the alleged breach is non-payment. Intellikine may terminate the
agreement immediately upon written notice if we fail to make the initial license payments. Additionally, Intellikine may terminate the agreement upon 30 days prior written notice if we or a related party bring an action challenging the
validity of any of the licensed patents, provided that we have not withdrawn such action before the end of the 30-day notice period. We may terminate the agreement at any time upon 180 days prior written notice provided after the end of the
research term.

MedImmune/AZ. In August 2006, we entered into a product development and
commercialization agreement with MedImmune/AZ, to jointly develop and commercialize cancer drugs targeting Hsp90 and the Hedgehog pathway. Under the terms of this agreement, we shared equally with MedImmune/AZ all development costs, as well as
potential profits and losses, from any future marketed products. In November 2007, we regained from MedImmune/AZ worldwide development and commercialization rights under our Hedgehog pathway program on a royalty-free basis. In December 2008, we
regained from MedImmune/AZ worldwide development and commercialization rights under our Hsp90 chaperone inhibitor program. In January 2009, we reached an agreement with MedImmune/AZ to settle the residual funding obligation remaining for 2009
through lump-sum payments totaling $12.5 million, which were recorded as income from residual funding after reacquisition of Hsp90 program (a component of other income) in the nine months ended September 30, 2009. We received $12.5 million in
cash from MedImmune/AZ in the nine months ended September 30, 2009.

The profit and cost-sharing provisions of our
arrangement with MedImmune/AZ are no longer applicable, and we have full control over all future development and commercialization activities under our Hsp90 and Hedgehog pathway programs, subject to the payment of single-digit royalties to
MedImmune/AZ on worldwide net sales, if any, of each of IPI-504 and IPI-493. We do not have a royalty obligation to MedImmune/AZ on any future sales of IPI-926.

Novartis. In February 2006, we entered into a collaboration agreement with Novartis Institute for BioMedical Research, Inc., or Novartis, to discover, develop and commercialize drugs
targeting Bcl protein family members for the treatment of a broad range of cancers. Under the terms of this agreement, we granted to Novartis an exclusive, worldwide license to research, develop and commercialize pharmaceutical products that are
based upon our proprietary Bcl inhibitors. Novartis paid us an up-front license fee, an affiliate of Novartis made an equity investment in us, and Novartis provided us research funding over the initial two-year research term, which expired in
February 2008. Novartis chose not to exercise its right to extend the research term for up to two additional one-year terms; thus, the research term ended in February 2008 and we have no further performance obligations to Novartis. We may request to
participate in clinical development of any products arising from this collaboration and, if such request is agreed upon by Novartis, Novartis will fund agreed-upon development costs that are incurred by us. We also have a non-exclusive right to
detail Bcl-2 family inhibitor products in the United States, with our detailing costs to be reimbursed by Novartis. Novartis has agreed to make milestone payments to us totaling over $370 million if certain specified research, development and
commercialization milestones are achieved for multiple products for multiple indications. Novartis has also agreed to pay us tiered royalties ranging from single-digits to teens upon successful commercialization of any products developed under the
alliance. Novartis has the right to terminate the agreement at any time upon 60 days prior written notice. In addition, Novartis has the right to terminate the agreement in connection with a material breach by us that remains uncured for a
period of 120 days after notice. We can terminate specified programs under the agreement as to breaches by Novartis relating solely to such programs that remain uncured for a period of 120 days after notice or can terminate the agreement in its
entirety in connection with a material breach by Novartis of the agreement that remains uncured for a period of 120 days after notice. The agreement shall expire when the parties thereto have no further obligations to each other thereunder unless
earlier terminated as described above.



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##### Table of Contents



Financial
Overview

Revenue

All of our revenue to date has been derived from license fees, the reimbursement of research and development costs, contract service revenue and milestones payments received from our collaboration
partners. As the agreements with Mundipharma and Purdue provide for funding for our research and development efforts, we recognize this cost reimbursement as revenue in the period earned in proportion to our forecasted total expenses as compared to
the total research funding budget for the year. In the future, we may generate revenue from a combination of product sales, research and development support services and milestone payments in connection with strategic relationships, and royalties
resulting from the sales of products developed under licenses of our intellectual property. We expect that any revenue we generate will fluctuate from year to year as a result of the timing and amount of license fees, research and development
reimbursement, milestone and other payments earned under our collaborative or strategic relationships, and the amount and timing of payments that we earn upon the sale of our products, to the extent any are successfully commercialized. If we fail to
complete the development of our drug candidates in a timely manner or obtain regulatory approval for them, our ability to generate future revenue, and our results of operations and financial position, would be materially adversely affected.

Research and Development Expense

We are a drug discovery and development company. Our research and development expense primarily consists of the following:



| |  |  | compensation of personnel associated with research activities;
| | - |  | --------------------------------------------------------------



| |  |  | clinical testing costs, including payments made to contract research organizations;
| | - |  | -----------------------------------------------------------------------------------



| |  |  | laboratory supplies and materials;
| | - |  | ----------------------------------



| |  |  | manufacturing drug candidates for preclinical testing and clinical studies;
| | - |  | ---------------------------------------------------------------------------



| |  |  | costs associated with the licensing of research and development programs;
| | - |  | -------------------------------------------------------------------------



| |  |  | preclinical testing costs, including costs of toxicology studies;
| | - |  | -----------------------------------------------------------------



| |  |  | fees paid to external consultants;
| | - |  | ----------------------------------



| |  |  | fees paid to professional service providers for independent monitoring and analysis of our clinical trials;
| | - |  | -----------------------------------------------------------------------------------------------------------



| |  |  | costs for collaboration partners to perform research activities;
| | - |  | ----------------------------------------------------------------



| |  |  | depreciation of equipment; and
| | - |  | ------------------------------



| |  |  | allocated costs of facilities.
| | - |  | ------------------------------

General and Administrative Expense

General and administrative expense
primarily consists of compensation of personnel in executive, finance, accounting, legal, information technology infrastructure, corporate communications, human resources and commercial functions. Other costs include facilities costs not otherwise
included in research and development expense, and professional fees for legal and accounting services. General and administrative expense also consists of the costs of maintaining our intellectual property portfolio.

Other Income and Expense

Interest expense and other interest and investment income typically consists of interest earned on cash, cash equivalents and available-for-sale securities, net of interest expense, and amortization of
warrants. Interest expense includes amortization of the loan commitment asset from PPLP starting on April 1, 2009. Income from residual funding after reacquisition of Hsp90 program was recorded in the nine months ended September 30, 2009.

Critical Accounting Policies and Significant Judgments and Estimates

The discussion and analysis of our financial condition and results of operations is based on our condensed consolidated financial
statements, which have been prepared in accordance with accounting principles generally accepted in the United States. The preparation of these financial statements requires us to make judgments, estimates and assumptions that affect the amounts
reported in the financial statements and accompanying notes. On an ongoing basis, we evaluate our estimates, including those related to revenue recognition, accrued expenses, assumptions in the valuation of stock-based compensation and income taxes.
We base our estimates on historical experience and on various other assumptions that we believe to be reasonable under the circumstances. Actual results could differ from those estimates.

There have been no material changes to our critical accounting policies during the nine months ended September 30, 2010. Please
refer to Part II, Item 7 Managements Discussion and Analysis of Financial Condition and Results of Operations of our annual report on Form 10-K for the fiscal year ended December 31, 2009 for a discussion of our critical
accounting policies and significant judgments and estimates.



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New Accounting
Pronouncements

In October 2009, the FASB issued Accounting Standard Update No. 2009-13, Multiple-Element Revenue
Arrangements (ASU No. 2009-13) , which updates the existing multiple-element revenue arrangements guidance currently included in Accounting Standards Codification No. 605-25 in two ways. The first change relates to the
determination of when the individual deliverables included in a multiple-element arrangement may be treated as separate units of accounting. This is significant as it will likely result in the requirement to separate more deliverables within an
arrangement, ultimately leading to less revenue deferral. The second change modifies the manner in which the transaction consideration is allocated across the separately identified deliverables. ASU No. 2009-13 also significantly expands the
disclosures required for multiple-element revenue arrangements. ASU No. 2009-13 will be effective for the first annual reporting period beginning on or after June 15, 2010, and may be applied retrospectively for all periods presented or
prospectively to arrangements entered into or materially modified after the adoption date. We do not expect ASU No. 2009-13 to have a material impact on our financial statements or results of operations.

In April 2010, the Financial Accounting Standards Board issued Accounting Standard Update No. 2010-17,
Milestone Method of Revenue Recognition (ASU No. 2010-17), which provides guidance on defining a milestone and determining when it may be appropriate to apply the milestone method of revenue
recognition for research or development transactions. Prior to the issuance of ASU No. 2010-17, authoritative guidance on the use of the milestone method did not exist. ASU No. 2010-17 is effective on a prospective basis for milestones
achieved in fiscal years, and interim periods within those years, beginning on or after June 15, 2010 with early adoption permitted. Alternatively, ASU No. 2010-17 can be adopted retrospectively for all prior periods. We do not expect ASU
No. 2010-17 to have a material impact on our financial statements or results of operations.

Results
of Operations

The following tables summarize our results of operations for each of the three and nine months ended
September 30, 2010 and 2009, in thousands, together with the change in these items in dollars and as a percentage:



|                                                                  |  |                                         |         |   |          |   |         |          |  |   |         |   |  |  |      |   
|----------------------------------------------------------------- |  | --------------------------------------- | ------- | - | -------- | - | ------- | -------- |  | - | ------- | - |  |  | ---- | --
|                                                                  |  | For the Three MonthsEnded September 30, |         |   | $ Change |   |         | % Change | 
|                                                                  |  | 2010                                    |         |   | 2009     |   |         |         
|Revenue                                                           |  | $                                       | 22,189  |   |          | $ | 13,776  |          |  | $ | 8,413   |   |  |  | 61   | % 
|Research and development expense                                  |  |                                         | (38,732 | ) |          |   | (18,499 | )        |  |   | (20,233 | ) |  |  | 109  | % 
|General and administrative expense                                |  |                                         | (5,015  | ) |          |   | (4,570  | )        |  |   | (445    | ) |  |  | 10   | % 
|Interest expense                                                  |  |                                         | (522    | ) |          |   | (433    | )        |  |   | (89     | ) |  |  | 21   | % 
|Interest and investment income                                    |  |                                         | 122     |   |          |   | 401     |          |  |   | (279    | ) |  |  | (70  | )%
|Income tax benefit                                                |  |                                         | 700     |   |          |   |        |          |  |   | 700     |   |  |  |     |   
|                                                                  |  |                                         |        
|                                                                  |  | For the Nine MonthsEnded September 30,  |         |   | $ Change |   |         | % Change | 
|                                                                  |  | 2010                                    |         |   | 2009     |   |         |         
|Revenue                                                           |  | $                                       | 56,570  |   |          | $ | 36,370  |          |  | $ | 20,200  |   |  |  | 56   | % 
|Research and development expense                                  |  |                                         | (77,121 | ) |          |   | (60,453 | )        |  |   | (16,668 | ) |  |  | 28   | % 
|General and administrative expense                                |  |                                         | (14,980 | ) |          |   | (15,582 | )        |  |   | 602     |   |  |  | (4   | )%
|Interest expense                                                  |  |                                         | (1,388  | ) |          |   | (867    | )        |  |   | (521    | ) |  |  | 60   | % 
|Income from residual funding after reacquisition of Hsp90 program |  |                                         |        |   |          |   | 12,450  |          |  |   | (12,450 | ) |  |  | (100 | )%
|Income from NIH reimbursement                                     |  |                                         |        |   |          |   | 1,745   |          |  |   | (1,745  | ) |  |  | (100 | )%
|Interest and investment income                                    |  |                                         | 352     |   |          |   | 1,736   |          |  |   | (1,384  | ) |  |  | (80  | )%
|Income tax benefit                                                |  |                                         | 700     |   |          |   |        |          |  |   | 700     |   |  |  |     |   

Revenue

Our revenue during the three and nine months ended September 30, 2010 consisted of approximately $21.5 million and
$54.4 million, respectively, for reimbursed research and development services and $0.7 million and $2.2 million, respectively, from the amortization of the deferred revenue associated with the grant of rights and licenses under our strategic
agreements with Mundipharma and Purdue. Our revenue during the three and nine months ended September 30, 2009 consisted of approximately $13.1 million and $34.2 million, respectively, for reimbursed research and development services and $0.7
million and $2.2 million, respectively, from the amortization of the deferred revenue associated with the grant of rights and licenses under our strategic alliances with Mundipharma and Purdue. The increase in reimbursed research and development
services revenue is a result of a contractual increase in the committed amount of research and development funding from Mundipharma and Purdue and increased internal effort and greater external expenses on our FAAH inhibitor, Hedgehog pathway
inhibitor, PI3K inhibitor and early discovery programs.



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##### Table of Contents



Research and
Development Expense

Research and development expense represented approximately 89% and 80% of our total operating expenses
for the three months ended September 30, 2010 and 2009, respectively. Research and development expense represented approximately 84% and 80% of our total operating expenses for the nine months ended September 30, 2010 and 2009,
respectively. The increase in research and development expense in the three months ended September 30, 2010 as compared to the same period in 2009 is primarily attributable to the $13.5 million license fee for our PI3K program and
increases of $2.7 million in pharmaceutical development expenses and $2.4 million in clinical expenses related to our Hedgehog pathway and FAAH programs.

The increase in research and development expense in the nine months ended September 30, 2010 as compared to the same period in 2009 is primarily attributable to the $13.5 million license fee for our
PI3K program and an increase of $1.7 million in salary and benefit expenses.

We began to track and accumulate costs by major
program starting on January 1, 2006. During the three and nine months ended September 30, 2010 and 2009, and from January 1, 2006 through September 30, 2010, we estimate that we incurred the following expenses by program. These
expenses primarily relate to payroll and related expenses for personnel working on the programs, process development and manufacturing, preclinical toxicology studies, clinical trial costs and allocated costs of facilities.



|                              |  |                                      |      |  |                                      |   |     |                                     |  |   |                                     |  |  |                                      |      |  |  |   |      | 
|----------------------------- |  | ------------------------------------ | ---- |  | ------------------------------------ | - | --- | ----------------------------------- |  | - | ----------------------------------- |  |  | ------------------------------------ | ---- |  |  | - | ---- | 
|(Dollars in Millions)
Program |  | Three Months EndedSeptember 30, 2010 |      |  | Three Months EndedSeptember 30, 2009 |   |     | Nine Months EndedSeptember 30, 2010 |  |   | Nine Months EndedSeptember 30, 2009 |  |  | January 1, 2006 toSeptember 30, 2010 |     
|Hsp90 chaperone inhibitor     |  | $                                    | 2.7  |  |                                      | $ | 6.4 |                                     |  | $ | 11.4                                |  |  | $                                    | 28.0 |  |  | $ | 85.0 | 
|Hedgehog pathway inhibitor    |  |                                      | 11.0 |  |                                      |   | 6.4 |                                     |  |   | 23.9                                |  |  |                                      | 16.4 |  |  |   | 70.8 | 
|FAAH inhibitor                |  |                                      | 6.2  |  |                                      |   | 2.1 |                                     |  |   | 15.9                                |  |  |                                      | 6.9  |  |  |   | 25.3 | 
|PI3K*                         |  |                                      | 14.5 |  |                                      |   |    |                                     |  |   | 14.5                                |  |  |                                      |     |  |  |   | 14.5 | 



|* | Includes a license fee of $13.5 million
|- | ---------------------------------------

We expect expenses for our Hedgehog pathway inhibitor program to increase as we make progress in the clinical development of IPI-926. In addition, we expect expenses for our FAAH program to decrease as we
transition the development activities to Purdue and Mundipharma. For these and other reasons, we do not believe that the historical costs associated with our lead drug development programs are indicative of the future costs associated with these
programs or represent what any other future drug development program we initiate may cost. Due to the variability in the length of time and scope of activities necessary to develop a drug candidate, uncertainties related to cost estimates and our
ability to obtain marketing approval for our drug candidates, accurate and meaningful estimates of the total costs required to bring our product candidates to market are not available.

Because of the risks inherent in drug discovery and development, we cannot reasonably estimate or know:



| |  |  | the nature, timing and estimated costs of the efforts necessary to complete the development of our programs;
| | - |  | ------------------------------------------------------------------------------------------------------------



| |  |  | the anticipated completion dates of these programs; or
| | - |  | ------------------------------------------------------



| |  |  | the period in which material net cash inflows are expected to commence, if at all, from the programs described above and any potential future product
candidates.
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------

There is significant uncertainty regarding our ability to successfully develop any drug
candidates. These risks include the uncertainty of:



| |  |  | the scope, rate of progress and cost of our clinical trials that we are currently running or may commence in the future;
| | - |  | ------------------------------------------------------------------------------------------------------------------------



| |  |  | the scope, rate of progress of our preclinical studies and other research and development activities;
| | - |  | -----------------------------------------------------------------------------------------------------



| |  |  | clinical trial results;
| | - |  | -----------------------



| |  |  | the cost of filing, prosecuting, defending and enforcing any patent claims and other intellectual property rights relating to our programs under
development;
| | - |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | the terms and timing of any strategic alliance, licensing and other arrangements that we have or may establish in the future relating to our programs
under development;
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | the cost and timing of regulatory approvals;
| | - |  | --------------------------------------------



| |  |  | the cost of establishing clinical supplies of any product candidates; and
| | - |  | -------------------------------------------------------------------------



| |  |  | the effect of competing technological and market developments.
| | - |  | --------------------------------------------------------------



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General and
Administrative Expense

The decrease in general and administrative expense for the nine months ended September 30,
2010 as compared to the nine months ended September 30, 2009 is primarily attributable to a decrease in consulting expenses of $1.2 million partially offset by an increase in salary and benefit expenses of $0.4 million.

Interest Expense

Interest expense increased for the nine months ended September 30, 2010 as compared to the nine months ended September 30, 2009, primarily as a result of our having commenced amortization of the
loan commitment asset from Purdue entities on April 1, 2009.

Income from Residual Funding After Reacquisition of
Hsp90 Program

Following our reacquisition of the Hsp90 program in December 2008, MedImmune/AZ remained obligated to fund
an amount equivalent to its share of the Hsp90 program costs for the ensuing six-month period. Reimbursable amounts from the date of reacquisition were recorded as income from residual funding after reacquisition of Hsp90 program. In January 2009,
we agreed with MedImmune/AZ to settle the residual funding obligations through lump sum payments totaling $12.5 million.

Income from NIH Reimbursement

During the nine months ended September 30, 2009, we received $1.7 million from the National Institutes of Health related to contract work performed by Discovery Partners International, Inc. from
August 2004 through June 2006. We do not expect any such income in future periods.

Interest and Investment Income

Interest and investment income decreased in the three and nine months ended September 30, 2010 as compared to the
three and nine months ended September 30, 2009 primarily as a result of the lower yields on our cash equivalents and available-for-sale securities. We expect interest and investment income to continue to be lower in 2010 as compared to 2009
primarily due to lower expected yields and lower average balances.

Income Tax Benefit

During the three months ended September 30, 2010, we recorded an income tax benefit of $700,321 as an uncertain tax position we took
in a prior year is no longer subject to examination due to the expiration of the statute of limitations.

Liquidity and
Capital Resources

We have not generated any revenue from the sale of drugs to date, and we do not expect to generate
any such revenue for the next several years, if at all. We have instead relied on the proceeds from sales of equity securities, interest on investments, license fees, expense reimbursements under our collaborations, a milestone payment, contract
service payments and debt to fund our operations. Our available-for-sale debt securities primarily trade in liquid markets, and the average number of days to maturity of our portfolio as of September 30, 2010 is less than six months. Because
our product candidates are in various stages of clinical and preclinical development and the outcome of these efforts is uncertain, we cannot estimate the actual amounts necessary to successfully complete the development and commercialization of our
product candidates or whether, or when, we may achieve profitability.

The following table summarizes our significant capital
resources (in thousands):



|                                                              |  |                                 |         |   |                  |   |         |  
|------------------------------------------------------------- |  | ------------------------------- | ------- | - | ---------------- | - | ------- | -
|                                                              |  | September 30,2010               |         |   | December 31,2009 |  
|Cash, cash equivalents and available-for-sale securities      |  | $                               | 110,184 |   |                  | $ | 130,737 |  
|Working capital                                               |  |                                 | 89,013  |   |                  |   | 120,635 |  
|                                                              | 
|                                                              |  | Nine Months Ended September 30, |        
|                                                              |  | 2010                            |         |   | 2009             |  
|Cash provided by (used in):                                   |  |                                 |         |   |                  |   |         |  
|Operating activities                                          |  | $                               | (18,118 | ) |                  | $ | 3,793   |  
|Investing activities                                          |  |                                 | 19,838  |   |                  |   | 1,653   |  
|Capital expenditures (included in investing activities above) |  |                                 | (1,512  | ) |                  |   | (1,855  | )
|Financing activities                                          |  |                                 | 173     |   |                  |   | 11,955  |  



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Cash Flows

The principal use of cash in operating activities in all of the periods presented was the funding of our research and
development expenses, which have increased as our product development pipeline has advanced. Our cash flows from operating activities for the period ended September 30, 2010 includes the first license payment of $5 million for our PI3K program.
Cash flows from operations in future periods can vary significantly due to various factors, including changes in accounts payable, accrued expenses and deferred revenue. During January 2009, we issued to Purdue and PPLP an aggregate of two million
shares of our common stock and warrants to purchase up to six million shares of our common stock for cash proceeds of $30 million. The issuance of these securities was recorded for $11.8 million in our cash flows from financing activities, which
represents the fair market value ($5.29 per share for the common stock and approximately $1.3 million for the warrants) as of the day before the first equity closing, and $18.2 million was accounted for as an up-front license fee in deferred revenue
and recorded in our cash flows from operating activities.

Net cash from investing activities for the period ended
September 30, 2010 included proceeds of $182.8 million from maturities of available-for-sale securities, proceeds of $7.2 million from sales of available-for-sale securities and $168.7 million in purchases of available-for-sale securities.
Capital expenditures in the nine months ended September 30, 2010 and September 30, 2009 primarily consisted of laboratory equipment and capitalized software costs.

We will need substantial additional funds to support our planned operations. In the absence of additional funding or business development activities and based on our current operating plans, we expect
that our current cash and investments, together with research and development funding from Purdue and Mundipharma and the $50.0 million line of credit that has been made available to us by PPLP, are sufficient to fund our planned operations
into 2013. We may, however, need to raise additional funds before that date if our research and development expenses exceed our current expectations or if we do not receive the payments we expect to receive from Mundipharma and Purdue. We may need
to raise additional funds for other reasons, including:



| |  |  | our drug candidates require more extensive clinical or preclinical testing than we currently expect;
| | - |  | ----------------------------------------------------------------------------------------------------



| |  |  | we advance more of our drug candidates than expected into costly later stage clinical trials;
| | - |  | ---------------------------------------------------------------------------------------------



| |  |  | we advance more preclinical drug candidates than expected into early stage clinical trials;
| | - |  | -------------------------------------------------------------------------------------------



| |  |  | the cost of acquiring raw materials for, and of manufacturing, our drug candidates is higher than anticipated;
| | - |  | --------------------------------------------------------------------------------------------------------------



| |  |  | we acquire a third party or license rights to additional drug candidates or new technologies from one or more third parties;
| | - |  | ----------------------------------------------------------------------------------------------------------------------------



| |  |  | we are required, or consider it advisable, to acquire or license intellectual property rights from one or more third parties;
| | - |  | -----------------------------------------------------------------------------------------------------------------------------



| |  |  | Mundipharma or Purdue elects to discontinue its participation in a partnered program; or
| | - |  | ----------------------------------------------------------------------------------------



| |  |  | we experience a loss in our investments due to general market conditions or other reasons.
| | - |  | ------------------------------------------------------------------------------------------

We may seek additional funding through public or private financings of equity or debt securities, but such financing may not be available
on acceptable terms, or at all, particularly in light of current market conditions. In addition, the terms of our financings may be dilutive to, or otherwise adversely affect, holders of our common stock, and such terms may impact our ability to
make capital expenditures or incur additional debt. We may also seek additional funds through arrangements with collaborators or other third parties, or through project financing. These arrangements would generally require us to relinquish or
encumber rights to some of our technologies or drug candidates, and we may not be able to enter into such agreements on acceptable terms, if at all. If we are unable to obtain additional funding on a timely basis, we may be required to curtail or
terminate some or all of our product development programs.

Contractual Obligations and Off-Balance Sheet Arrangements

Since inception, we have not engaged in any off-balance sheet financing activities, including the use of structured
finance, special purpose entities or variable interest entities.

We are obligated to pay to Intellikine a license fee of $8.5
million in the first quarter of 2011 in connection with the license of rights to our PI3K program. This amount is included in accrued expenses at September 30, 2010.



|Item 3. | Quantitative and Qualitative Disclosures About Market Risk
|------- | ----------------------------------------------------------

Our interest income is sensitive to changes in the general level of U.S. interest rates, particularly since a significant portion of our investments are in money market funds, U.S. government-sponsored
enterprise obligations, corporate obligations, U.S. Treasury securities and mortgage-backed securities. We do not enter into investments for trading or speculative purposes. Our cash is deposited in and invested through highly rated financial
institutions in North America. Our marketable securities are subject to interest rate risk and will fall in value if market interest rates increase.

A hypothetical 100 basis point increase in interest rates would result in an approximate $317,000 decrease in the fair value of our investments as of September 30, 2010, as compared to an approximate
$446,000 decrease as of December 31, 2009. We generally hold our fixed income investments until maturity and, therefore, we do not expect our operating results or cash flows to be affected to any significant degree by the effect of a
change in market interest rates on our investments.



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|Item 4. | Controls and Procedures
|------- | -----------------------

Our management, with the participation of our principal executive and financial officer, evaluated the effectiveness of our disclosure
controls and procedures as of September 30, 2010. The term disclosure controls and procedures, as defined in Rules 13a-15(e) and 15d-15(e) under the Securities Exchange Act of 1934, as amended, or Exchange Act, means controls and
other procedures of a company that are designed to ensure that information required to be disclosed by a company in the reports that it files or submits under the Exchange Act is recorded, processed, summarized and reported, within the time periods
specified in the SECs rules and forms. Disclosure controls and procedures include, without limitation, controls and procedures designed to ensure that information required to be disclosed by a company in the reports that it files or submits
under the Exchange Act is accumulated and communicated to the companys management, including its principal executive and principal financial officers, as appropriate to allow timely decisions regarding required disclosure. Management
recognizes that any controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving their objectives and management necessarily applies its judgment in evaluating the cost-benefit relationship of
possible controls and procedures. Based on the evaluation of our disclosure controls and procedures as of September 30, 2010, our principal executive and financial officer concluded that, as of such date, our disclosure controls and procedures
were effective at the reasonable assurance level.

No change in our internal control over financial reporting (as defined in
Rules 13a-15(f) and 15d-15(f) under the Exchange Act) occurred during the fiscal quarter ended September 30, 2010 that has materially affected, or is reasonably likely to materially affect, our internal control over financial reporting.

PART II. OTHER INFORMATION



|Item 1A. | Risk Factors
|-------- | ------------

You should
carefully consider the following risk factors, in addition to other information included in this quarterly report on Form 10-Q, in evaluating Infinity and our business. If any of the following risks occur, our business, financial condition and
operating results could be materially adversely affected. These risk factors restate and supersede the risk factors set forth under the heading Risk Factors in our Annual Report on Form 10-K for the year ended December 31, 2009.

Risks Related to Our Stage of Development as a Company

We have a history of operating losses, expect to incur significant and increasing operating losses in the future, and may never be
consistently profitable.

We have a limited operating history for you to evaluate our business. We have no approved
products and have generated no product revenue from sales. We have primarily incurred operating losses. As of September 30, 2010, we had an accumulated deficit of $217.3 million. We have spent, and expect to continue to spend, significant
resources to fund the research and development of IPI-504, IPI-493, IPI-926, IPI-940, IPI-145 and our other drug candidates. While we may have net income in future periods as the result of non-recurring collaboration revenue, we expect to incur
substantial operating losses over the next several years as our clinical trial and drug manufacturing activities increase. As a result, we expect that our accumulated deficit will also increase significantly.

Our drug candidates are in varying stages of preclinical and clinical development and may never be approved for sale or generate any
revenue. We will not be able to generate product revenue unless and until one of our drug candidates successfully completes clinical trials and receives regulatory approval. Since even our most advanced drug candidate requires substantial additional
clinical development, we do not expect to receive revenue from our drug candidates for several years, if at all. Even if we eventually generate revenues, we may never be profitable, and if we do achieve profitability, we may not be able to sustain
or increase profitability on a quarterly or annual basis.

We may be unable to raise the substantial additional capital
that we will need to sustain our operations.

We will need substantial additional funds to support our planned operations.
In the absence of additional funding or business development activities and based on our current operating plans, we expect that our current cash and investments, together with research and development funding from Mundipharma International
Corporation Limited, or Mundipharma, and Purdue Pharmaceutical Products L.P., or Purdue, and the $50 million line of credit that has been made available to us by Purdue Pharma L.P., are sufficient to fund our planned operations into 2013. We may,
however, need to raise additional funds before that date if our research and development expenses exceed our current expectations or if we do not receive the payments we expect to receive from Mundipharma and Purdue. We may need to raise additional
funds for other reasons, including:



| |  |  | our drug candidates require more extensive clinical or preclinical testing than we currently expect;
| | - |  | ----------------------------------------------------------------------------------------------------



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| |  |  | we advance more of our drug candidates than expected into costly later stage clinical trials;
| | - |  | ---------------------------------------------------------------------------------------------



| |  |  | we advance more preclinical drug candidates than expected into early stage clinical trials;
| | - |  | -------------------------------------------------------------------------------------------



| |  |  | the cost of acquiring raw materials for, and of manufacturing, our drug candidates is higher than anticipated;
| | - |  | --------------------------------------------------------------------------------------------------------------



| |  |  | we acquire a third party or license rights to additional drug candidates or new technologies from one or more third parties;
| | - |  | ----------------------------------------------------------------------------------------------------------------------------



| |  |  | we are required, or consider it advisable, to acquire or license intellectual property rights from one or more third parties;
| | - |  | -----------------------------------------------------------------------------------------------------------------------------



| |  |  | Mundipharma or Purdue elects to discontinue its participation in a partnered program; or
| | - |  | ----------------------------------------------------------------------------------------



| |  |  | we experience a loss in our investments due to general market conditions or other reasons.
| | - |  | ------------------------------------------------------------------------------------------

We may seek additional funding through public or private financings of equity or debt securities, but such financing may not be available
on acceptable terms, or at all, particularly in light of current market conditions. In addition, the terms of such financings may be dilutive to, or otherwise adversely affect, holders of our common stock, and such terms may impact our ability to
make capital expenditures or incur additional debt. We may also seek additional funds through arrangements with collaborators or other third parties, or through project financing. These arrangements would generally require us to relinquish or
encumber rights to some of our technologies or drug candidates, and we may not be able to enter into such arrangements on acceptable terms, if at all. If we are unable to obtain additional funding on a timely basis, we may be required to curtail or
terminate some or all of our product development programs.

Our results to date do not guarantee that any of our product
candidates will be safe or effective, or receive regulatory approval.

The risk of failure of our current clinical
candidates is high. To date, the data supporting our clinical development strategy for IPI-504, IPI-493, IPI-926 and IPI-940 are derived solely from laboratory and preclinical studies and, in the case of IPI-504, limited early-to-mid-stage clinical
trials. Later clinical trials may not yield data consistent with earlier clinical trials, as was the case in our Phase 3 clinical trial of IPI-504 in patients with gastrointestinal stromal tumors, or GIST, which we elected to close in April 2009
when an early review of safety data showed a higher than anticipated mortality rate among patients enrolled in the treatment arm. In such a case, it may be necessary for us to change our development strategy or abandon development of that drug
candidate, either of which would result in delays and additional costs. We are conducting various clinical and preclinical studies of IPI-504 and IPI-493. These studies are focused on seeking to establish a dose and schedule of administration that
optimizes safety and efficacy of these candidates, and identifying patient populations, or subpopulations, most likely to benefit from Hsp90 chaperone inhibition. If these studies do not yield results we believe are necessary to warrant further
development, we may elect to discontinue further development of the applicable drug candidate. It is impossible to predict when or if IPI-504, IPI-493, IPI-926, IPI-940, IPI-145 or any of our other drug candidates will prove safe or effective in
humans or receive regulatory approval. These drug candidates may not demonstrate in patients the chemical and pharmacological properties ascribed to them in laboratory studies or early-stage clinical trials, and they may interact with human
biological systems or other drugs in unforeseen, ineffective or harmful ways. If we are unable to discover or successfully develop drugs that are safe and effective in humans, we will not have a viable business.

If our global strategic alliance with Mundipharma and Purdue, or any future alliance we may enter into, is unsuccessful, our
operations may be negatively impacted.

We have a global strategic alliance with Mundipharma to research, develop and
jointly commercialize IPI-926, IPI-940 and product candidates arising out of our Hedgehog pathway, fatty acid amide hydrolase, or FAAH, phosphoinositide-3 kinase, or PI3K, and early discovery programs, and with Purdue to commercialize product
candidates arising out of our FAAH program in the United States. Under the strategic alliance agreements, Mundipharma and Purdue have committed to provide substantial funding, significant capabilities in the field of pain and, in the case of
Mundipharma, significant capabilities in marketing and sales outside of the United States. In addition, we have a collaboration with Intellikine to discover, develop and commercialize pharmaceutical products targeting the delta and/or gamma isoforms
of PI3K. Under this alliance, Intellikine has committed to provide significant chemistry and biochemistry capabilities. The success of these alliances is largely dependent on the resources, efforts, technology and skills brought to such alliance by
our alliance partners. Disputes and difficulties in these types of relationships are common, often due to conflicting priorities or conflicts of interest. Merger and acquisition activity may exacerbate these conflicts. The benefits of our alliances
will be reduced or eliminated if any of our alliance partners:



| |  |  | terminates the applicable strategic alliance agreement;
| | - |  | -------------------------------------------------------



| |  |  | fails to devote financial or other resources to the applicable alliance, thereby hindering or delaying development, manufacturing or commercialization
activities;
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | in the case of Mundipharma and Purdue, fails to successfully develop or manufacture any products arising out of our FAAH program or to commercialize
any drug candidate under the applicable alliance; or
| | - |  | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | fails to maintain the financial resources necessary to continue financing its portion of development, manufacturing, and commercialization costs, if
any, or its own operations.
| | - |  | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



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Under our agreements
with Mundipharma and Purdue, each agreement may be terminated on 60 days prior written notice if we were to materially breach such agreement and fail to cure such breach within the 60-day notice period. In addition, each of these
strategic alliance agreements may be terminated in the event we experience a change in control or in the event that, during the funded research period, either Julian Adams is no longer a full-time executive of Infinity or both Steven Holtzman and
Adelene Perkins are no longer full-time executives of Infinity. In addition, Mundipharma has the right to opt out of participation in the Hedgehog pathway, PI3K program, and early discovery programs in November of each calendar year, subject to 12
months of continued funding.

If Mundipharma and/or Purdue were to exercise its right to opt out of a program or to terminate
its respective agreement, we may not have sufficient financial resources or capabilities to continue development and commercialization of products from the affected program, and our ability to attract a new alliance partner would be made more
difficult.

Much of the potential revenue from our alliance with Mundipharma and Purdue, and any alliances we may enter into
in the future, will consist of contingent payments, such as royalties payable on sales of any successfully developed drugs. Any such contingent revenue will depend upon our, and our alliance partners, ability to successfully develop,
introduce, market and sell new products. In some cases, we will not be involved in these processes and will depend entirely on our alliance partners. For example, Mundipharma will be responsible for all of the commercialization efforts outside of
the United States for any products that are successfully developed from our Hedgehog pathway program and our early stage development programs, and Purdue and Mundipharma are jointly responsible for all development and commercialization activities
for products arising out of the FAAH project. Any of our current or future alliance partners may fail to develop or effectively commercialize products using our products or technologies because it:



| |  |  | decides not to devote the necessary resources because of internal constraints, such as limited personnel with the requisite scientific expertise,
limited cash resources or specialized equipment limitations, or the belief that other drug development programs may have a higher likelihood of obtaining regulatory approval or may potentially generate a greater return on investment;
| | - |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | does not have sufficient resources necessary to carry the drug candidate through clinical development, regulatory approval and commercialization; or
| | - |  | ----------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | cannot obtain the necessary regulatory approvals.
| | - |  | -------------------------------------------------

Further, while our agreement with Intellikine precludes Intellikine from developing or commercializing products directed to the PI3K delta and/or gamma isoforms that meet certain selectivity criteria,
Intellikine or other potential competitors may develop products directed to other isoforms of PI3K.

If any current or future
alliance partner fails to develop or effectively commercialize our drug candidates, we may not be able to develop and commercialize that drug independently, and our financial condition and operations would be negatively impacted.

If we are not able to attract and retain key personnel and advisors, we may not be able to operate our business successfully.

We are highly dependent on our management team, particularly Adelene Perkins, Julian Adams and Steven Holtzman, and the
other members of our executive leadership team. All of these individuals are employees-at-will, which means that neither Infinity nor the employee is obligated to a fixed term of service and that the employment relationship may be terminated by
either Infinity or the employee at any time, without notice, and whether or not cause or good reason exists for such termination. The loss of the services of any of these individuals might impede the achievement of our research, development and
commercialization objectives. For example, Purdue and Mundipharma each have the right to terminate its strategic alliance with us if, during the funded research period, either Julian Adams is no longer a full-time executive of Infinity or both
Steven Holtzman and Adelene Perkins are no longer full-time executives of Infinity. We do not maintain key person insurance on any of our employees.

Recruiting and retaining qualified scientific and business personnel is also critical to our success. We may not be able to attract and retain these personnel on acceptable terms given the competition
among numerous pharmaceutical and biotechnology companies for similar personnel. This competition is particularly intense near our headquarters in Cambridge, Massachusetts. We also experience competition for the hiring of scientific personnel from
universities and research institutions. In addition, we rely on consultants and advisors, including scientific and clinical advisors, to assist us in formulating our research and development strategy. Our consultants and advisors may be employed by
other entities, have commitments under consulting or advisory contracts with third parties that limit their availability to us, or both.

We may encounter difficulties in managing our growth, which could adversely affect our operations.

Our ability to manage our growth effectively depends upon the continual improvement of our processes and procedures, and the preservation of our corporate culture. We may not be able to implement
improvements in an efficient or timely manner, or maintain our corporate culture through organizational change. If we do not meet these challenges, we may be unable to take advantage of market opportunities, execute our business strategies or
respond to competitive pressures, which in turn may slow our growth or give rise to inefficiencies that would increase our losses or delay our programs.



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We may acquire
additional technology and complementary businesses in the future. Acquisitions involve many risks, any one of which could materially harm our business, including the diversion of managements attention from core business concerns, failure to
exploit acquired technologies, or the loss of key employees from either our business or the acquired business.

Our
investments are subject to risks that may cause losses and affect the liquidity of these investments.

As of
September 30, 2010, we had approximately $110.2 million in cash, cash equivalents and available-for-sale securities. We historically have invested these amounts in money market funds, corporate obligations, U.S. government-sponsored
enterprise obligations, U.S. Treasury securities and mortgage-backed securities meeting the criteria of our investment policy, which is focused on the preservation of our capital. These investments are subject to general credit, liquidity, market
and interest rate risks. We may realize losses in the fair value of these investments or a complete loss of these investments. In addition, should our investments cease paying or reduce the amount of interest paid to us, our interest income would
suffer. These market risks associated with our investment portfolio may have a material adverse effect on our financial condition and results of operations.

The estimates we make, or the assumptions on which we rely, in preparing our condensed consolidated financial statements could prove inaccurate.

Our condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the
United States. The preparation of these condensed consolidated financial statements requires us to make estimates and judgments that affect the reported amounts of our assets, liabilities, revenues and expenses. Such estimates and judgments include
those related to revenue recognition, accrued expenses, assumptions in the valuation of stock-based compensation and income taxes. We base our estimates and judgments on historical experience, facts and circumstances known to us and on various
assumptions that we believe to be reasonable under the circumstances. These estimates and judgments, or the assumptions underlying them, may change over time or prove inaccurate.

If we are not able to maintain effective internal controls as required by Section 404 of the Sarbanes-Oxley Act, our business and
stock price could be adversely affected.

Section 404 of the Sarbanes-Oxley Act of 2002 requires us, on an annual
basis, to review and evaluate our internal controls, and requires our independent auditors to attest to the effectiveness of our internal controls. Any failure by us to maintain the effectiveness of our internal controls in accordance with the
requirements of Section 404 of the Sarbanes-Oxley Act, as such requirements exist today or may be modified, supplemented or amended in the future, could have a material adverse effect on our business, operating results and stock price.

Risks Related to the Development and Commercialization of Our Drug Candidates

All of our drug candidates remain subject to clinical testing and regulatory approval. This process is highly uncertain and we may
never be able to obtain marketing approval for any of our drug candidates.

To date, we have not obtained approval from the
U.S. Food and Drug Administration, or FDA, or any foreign regulatory authority to market or sell any of our drug candidates. Our success depends primarily upon our, and our strategic alliance partners, ability to develop and commercialize our
drug candidates successfully. Our two drug candidates in our Hsp90 program are IPI-504, which is currently being evaluated in a Phase 1b clinical trial as well as an investigator-sponsored study, and IPI-493, which is being evaluated in two Phase 1
clinical trials. Our Hedgehog pathway inhibitor, IPI-926 is being evaluated in a Phase 1 clinical trial and in a Phase 1b/2 clinical trial. We also commenced our first clinical trial of IPI-940 in February 2010, and we have other drug candidates in
various stages of preclinical development and discovery research, including IPI-145, the lead compound in our PI3K inhibitor program.

Our drug candidates are subject to extensive governmental regulations relating to development, clinical trials, manufacturing and commercialization. Rigorous preclinical testing and clinical trials and an
extensive regulatory approval process are required in the United States and in many foreign jurisdictions prior to the commercial sale of medicinal products like our drug candidates. Satisfaction of these and other regulatory requirements is costly,
time consuming, uncertain and subject to unanticipated delays. It is possible that none of the drug candidates we are developing, or may in the future develop, either alone or in collaboration with strategic alliance partners, will obtain marketing
approval. In connection with the clinical trials of IPI-504, IPI-493, IPI-926, IPI-940 and any other drug candidate we may seek to develop in the future, including IPI-145, we face, among other risks, risks that:



| |  |  | the drug candidate may not prove to be safe or effective;
| | - |  | ---------------------------------------------------------



| |  |  | the results of later trials may not confirm positive results from earlier preclinical studies or clinical trials, as was the case with our Phase 3
clinical trial of IPI-504 in GIST; and
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | the results may not meet the level of statistical significance required by the FDA or other regulatory authorities.
| | - |  | -------------------------------------------------------------------------------------------------------------------



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We are conducting various clinical and preclinical studies of IPI-504 and IPI-493. These
studies are focused on seeking to establish a dose and schedule of administration that optimizes safety and efficacy of these candidates, and identifying patient populations, or subpopulations, most likely to benefit from Hsp90 chaperone inhibition.
If these studies do not yield results we believe are necessary to warrant further development, we may elect to discontinue further development of the applicable drug candidate.

We have limited experience in conducting and managing the clinical trials necessary to obtain regulatory approvals, including approval by
the FDA and comparable foreign regulatory agencies. The time required to complete clinical trials and for regulatory review by the FDA and other countries regulatory agencies is uncertain and typically takes many years. Some of our drug
candidates may be eligible for the FDAs programs that are designed to facilitate the development and expedite the review of certain drugs, but we cannot provide any assurance that any of our drug candidates will qualify for one or more of
these programs. Even if a drug candidate qualifies for one or more of these programs, the FDA may later decide that the drug candidate no longer meets the conditions for qualification.

Our analysis of data obtained from preclinical and clinical activities is subject to confirmation and interpretation by regulatory
authorities, which could delay, limit or prevent regulatory approval. We may also encounter unanticipated delays or increased costs due to changes in government regulation from future legislation or administrative action or changes in FDA policy
during the period of product development, clinical trials and FDA regulatory review. For example, the Food and Drug Administration Amendments Act of 2007, or FDAAA, may make it more difficult and costly for us to obtain regulatory approval of our
drug candidates and to produce, market and distribute products after approval. The FDAAA granted a variety of new powers to the FDA, many of which are aimed at improving the safety of drug products before and after approval. In particular, it
authorizes the FDA to, among other things, require post-approval studies and clinical trials, mandate changes to drug labeling to reflect new safety information, and require risk evaluation and mitigation strategies for certain drugs. In addition,
it significantly expanded the federal governments clinical trial registry and results databank and creates new restrictions on the advertising and promotion of drug products. Under the FDAAA, companies that violate the new law are subject to
substantial civil monetary penalties.

Any delay in obtaining or failure to obtain required approvals could materially
adversely affect our ability to generate revenues from the particular drug candidate. Furthermore, the uses for which any regulatory authority may grant approval to market a product may be limited, thus placing limitations on the manner in which we
may market the product and limiting its market potential.

Our drug candidates must undergo rigorous clinical trials prior
to receipt of regulatory approval. Any problems in these clinical trials could delay or prevent commercialization of our drug candidates.

We cannot predict whether we will encounter problems with any of our ongoing or planned clinical trials that will cause us or regulatory authorities to delay or suspend clinical trials, as was the case
with our decision to close our Phase 3 clinical trial of IPI-504 in GIST, or to delay the analysis of data from ongoing clinical trials. Any of the following could delay the clinical development of our drug candidates:



| |  |  | unexpected or unfavorable results of discussions with the FDA or comparable foreign authorities regarding the scope or design of our clinical trials;
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | delays in receiving, or the inability to obtain, required approvals from institutional review boards or other reviewing entities at clinical sites
selected for participation in our clinical trials;
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | delays in enrolling patients into clinical trials;
| | - |  | --------------------------------------------------



| |  |  | a lower than anticipated retention rate of patients in clinical trials;
| | - |  | -----------------------------------------------------------------------



| |  |  | the need to repeat clinical trials as a result of inconclusive or negative results or unforeseen complications in testing;
| | - |  | --------------------------------------------------------------------------------------------------------------------------



| |  |  | inadequate supply or deficient quality of drug product or other materials necessary to conduct our clinical trials;
| | - |  | -------------------------------------------------------------------------------------------------------------------



| |  |  | unfavorable FDA inspection and review of a clinical trial site or records of any clinical or preclinical investigation;
| | - |  | -----------------------------------------------------------------------------------------------------------------------



| |  |  | serious and unexpected drug-related side effects experienced by participants in our clinical trials;
| | - |  | ----------------------------------------------------------------------------------------------------



| |  |  | a finding that the trial participants are being exposed to unacceptable health risks;
| | - |  | -------------------------------------------------------------------------------------



| |  |  | the placement by the FDA of a clinical hold on a trial; or
| | - |  | ----------------------------------------------------------



| |  |  | any restrictions on, or post-approval commitments with regard to, any regulatory approval we ultimately obtain that render the drug candidate not
commercially viable.
| | - |  | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------

We may suspend, or the FDA or other applicable regulatory authorities may require us
to suspend, clinical trials of a drug candidate at any time if we or they believe the patients participating in such clinical trials, or in independent third party clinical trials for drugs based on similar technologies, are being exposed to
unacceptable health risks or for other reasons.



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The delay, suspension
or discontinuation of any of our clinical trials or a delay in the analysis of clinical data for our drug candidates, for any of the foregoing reasons, could adversely affect our efforts to obtain regulatory approval for and to commercialize our
drug candidates, increase our operating expenses, and have a material adverse effect on our results of operations and financial condition.

Our inability to enroll sufficient numbers of patients in our clinical trials, or any delays in patient enrollment, can result in increased costs and longer development periods for our drug candidates.

Clinical trials require sufficient patient enrollment, which is a function of many factors, including:



| |  |  | the size of the patient population;
| | - |  | -----------------------------------



| |  |  | the nature of the trial protocol;
| | - |  | ---------------------------------



| |  |  | the number of clinical trial sites and the proximity of patients to those sites;
| | - |  | --------------------------------------------------------------------------------



| |  |  | the availability of effective treatments for the relevant disease;
| | - |  | ------------------------------------------------------------------



| |  |  | the eligibility criteria for the trial;
| | - |  | ---------------------------------------



| |  |  | the commitment of clinical investigators to identify eligible patients; and
| | - |  | ---------------------------------------------------------------------------



| |  |  | competing studies or trials.
| | - |  | ----------------------------

Our failure to enroll patients in our clinical trials could delay the completion of the clinical trial beyond current expectations. In addition, the FDA could require us to conduct clinical trials with a
larger number of subjects than has been projected for any of our drug candidates. As a result of these factors, we may not be able to enroll a sufficient number of patients in a timely or cost-effective manner.

Furthermore, enrolled patients may drop out of a clinical trial, which could impair the validity or statistical significance of the
clinical trial. A number of factors can influence the patient discontinuation rate, including, but not limited to:



| |  |  | the inclusion of a placebo arm in a trial;
| | - |  | ------------------------------------------



| |  |  | possible inactivity or low activity of the drug candidate being tested at one or more of the dose levels being tested;
| | - |  | ----------------------------------------------------------------------------------------------------------------------



| |  |  | the occurrence of adverse side effects, whether or not related to the drug candidate; and
| | - |  | -----------------------------------------------------------------------------------------



| |  |  | the availability of numerous alternative treatment options that may induce patients to discontinue their participation in the trial.
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------

A delay in our clinical trial activities could adversely affect our efforts to obtain regulatory approval
for and to commercialize our drug candidates, increase our operating expenses, and have a material adverse effect on our results of operations and financial condition.

We rely on third parties to conduct our clinical trials, and those third parties may not perform satisfactorily.

We rely on third parties such as contract research organizations, medical institutions and external investigators to enroll qualified patients, conduct our clinical trials and provide services in
connection with such clinical trials, and we intend to rely on these and other similar entities in the future. Our reliance on these third parties for clinical development activities reduces our control over these activities. Accordingly, these
third party contractors may not complete activities on schedule, or may not conduct our clinical trials in accordance with regulatory requirements or the trial design. If these third parties do not successfully carry out their contractual duties or
meet expected deadlines, we may be required to replace them. Replacing a third party contractor may result in a delay of the affected trial and unplanned costs. If this were to occur, our efforts to obtain regulatory approval for and to
commercialize our drug candidates may be delayed.

In addition, we are responsible for ensuring that each of our clinical
trials is conducted in accordance with the general investigational plan and protocol for the trial. The FDA requires us to comply with certain standards, referred to as good clinical practices, for conducting, recording and reporting the results of
clinical trials to assure that data and reported results are credible and accurate and that the rights, integrity and confidentiality of trial participants are protected. Our reliance on third parties that we do not control does not relieve us of
these responsibilities and requirements. If any of our trial investigators or third party contractors does not comply with good clinical practices, we may not be able to use the data and reported results from the trial. If this were to occur, our
efforts to obtain regulatory approval for and to commercialize our drug candidates may be delayed.



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Manufacturing
difficulties could delay or preclude commercialization of our drug candidates and substantially increase our expenses.

Our
drug candidates require precise, high quality manufacturing. The third party manufacturers on which we rely may not be able to comply with the FDAs current good manufacturing practices, or cGMPs, and other applicable government regulations and
corresponding foreign standards. These regulations govern manufacturing processes and procedures and the implementation and operation of systems to control and assure the quality of products. The FDA and foreign regulatory authorities may, at any
time, audit or inspect a manufacturing facility to ensure compliance with cGMPs and other quality standards. Any failure by our contract manufacturers to achieve and maintain high manufacturing and quality control standards could result in the
inability of our drug candidates to be released for use in one or more countries. In addition, such a failure could result in, among other things, patient injury or death, product liability claims, penalties or other monetary sanctions, the failure
of regulatory authorities to grant marketing approval of our drug candidates, delays, suspension or withdrawal of approvals, license revocation, seizures or recalls of drug candidates or products, operating restrictions and/or criminal prosecution,
any of which could significantly and adversely affect supply of our drug candidates and seriously hurt our business.

Contract
manufacturers may also encounter difficulties involving production yields or delays in performing their services. We do not have control over third party manufacturers performance and compliance with these applicable regulations and standards.
If, for any reason, our manufacturers cannot perform as agreed, we may be unable to replace such third party manufacturers in a timely manner and the production of our drug candidates would be interrupted, resulting in delays in clinical trials and
additional costs. Switching manufacturers may be difficult because the number of potential manufacturers is limited and, depending on the type of material manufactured at the contract facility, the change in contract manufacturer must be submitted
to and/or approved by the FDA and comparable regulatory authorities outside of the United States. In addition, a new manufacturer would have to be educated in, or develop substantially equivalent processes for, production of our drug candidates
after receipt of regulatory approval. It may be difficult or impossible for us to find a replacement manufacturer on acceptable terms quickly, or at all.

To date, our drug candidates have been manufactured for preclinical testing and clinical trials primarily by third party manufacturers. If the FDA or other regulatory agencies approve any of our other
drug candidates for commercial sale, we expect that we would continue to rely, at least initially, on third party manufacturers to produce commercial quantities of our approved drug candidates. These manufacturers may not be able to successfully
increase the manufacturing capacity for any approved drug candidates in a timely or economical manner, or at all. Significant scale-up of manufacturing might entail changes in the manufacturing process that have to be submitted to or approved by the
FDA or other regulatory agencies. If contract manufacturers engaged by us are unable to successfully increase the manufacturing capacity for a drug candidate, or we are unable to establish our own manufacturing capabilities, the commercial launch of
any approved products may be delayed or there may be a shortage in supply.

A natural product is utilized in the production of
IPI-926. This product is currently supplied from naturally available plant material. Our ability to acquire and process sufficient amounts of plant material to meet our manufacturing requirements is subject to a number of risks, including the
receipt of permits from federal and state authorities, adverse weather conditions or natural disasters that may impact plant availability or our ability to harvest it. In addition, we may be unsuccessful in identifying other locations where
this plant naturally occurs or establishing a sustainable method for growing this plant in a controlled environment. A material shortage of this plant could adversely impact or disrupt the manufacture of IPI-926, thus impacting our clinical
trial activities and, if IPI-926 is successfully developed, our ability to satisfy commercial demand for the product, thus adversely affecting our financial position and results of operations.

We have certain commercialization rights to our product portfolio, but we currently have limited marketing and sales experience and
capabilities.

We currently have commercialization rights in the United States for products arising out of our all of our
programs, except the FAAH program, and worldwide commercialization rights for our Hsp90 chaperone inhibitor program, including IPI-504 and IPI-493. In order to successfully commercialize our drug candidates, we will need to establish adequate
marketing and sales capabilities. We may not successfully establish these capabilities or have sufficient resources to do so. If we do not establish adequate marketing and sales capabilities, our ability to successfully commercialize any drug
candidates that we successfully develop will be adversely affected, as will our financial condition and results of operations. Even if we do develop such capabilities, we will compete with other companies that have experienced and well-funded
marketing and sales operations, and we will incur additional expenses.

If physicians and patients do not accept our future
drugs, we may not be able to generate significant revenues from product sales.

Even if any of our drug candidates obtains
regulatory approval, that product may not gain market acceptance among physicians, patients and the medical community for a variety of reasons including:



| |  |  | timing of our receipt of any marketing approvals, the terms of any such approvals and the countries in which any such approvals are obtained;
| | - |  | ---------------------------------------------------------------------------------------------------------------------------------------------



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| |  |  | timing of market introduction of competitive drugs;
| | - |  | ---------------------------------------------------



| |  |  | lower demonstrated clinical safety and efficacy compared to other drugs;
| | - |  | ------------------------------------------------------------------------



| |  |  | lack of cost-effectiveness;
| | - |  | ---------------------------



| |  |  | lack of reimbursement from managed care plans and other third-party payors;
| | - |  | ---------------------------------------------------------------------------



| |  |  | inconvenient or difficult administration;
| | - |  | -----------------------------------------



| |  |  | prevalence and severity of side effects;
| | - |  | ----------------------------------------



| |  |  | potential advantages of alternative treatment methods;
| | - |  | ------------------------------------------------------



| |  |  | safety concerns with similar drugs marketed by others;
| | - |  | ------------------------------------------------------



| |  |  | the reluctance of the target population to try new therapies and of physicians to prescribe those therapies;
| | - |  | ------------------------------------------------------------------------------------------------------------



| |  |  | the success of our physician education programs; and
| | - |  | ----------------------------------------------------



| |  |  | ineffective sales, marketing and distribution support.
| | - |  | ------------------------------------------------------

If any of our approved drugs fails to achieve market acceptance, we would not be able to generate significant revenue from those drugs or achieve profitability.

Even if we receive regulatory approvals for marketing our drug candidates, we could lose our regulatory approvals and our business
would be adversely affected if we, our collaborators, or our contract manufacturers fail to comply with continuing regulatory requirements.

The FDA continues to review products even after they receive initial approval. If we receive approval to commercialize any of our drug candidates, the manufacturing, marketing and sale of these drugs will
be subject to continuing regulation, including compliance with quality systems regulations, good manufacturing practices, adverse event requirements, and prohibitions on promoting a product for unapproved uses. Enforcement actions resulting from our
failure to comply with government and regulatory requirements could result in fines, suspension of approvals, withdrawal of approvals, product recalls, product seizures, mandatory operating restrictions, criminal prosecution, civil penalties and
other actions that could impair the manufacturing, marketing and sale of our drug candidates and our ability to conduct our business.

If our drug candidates exhibit harmful side effects after approval, our regulatory approvals could be revoked or otherwise negatively impacted, and we could become subject to costly and damaging
product liability claims.

Even if we receive regulatory approval for any of our drug candidates, we will have tested them
in only a small number of patients during our clinical trials. If our applications for marketing are approved and more patients begin to use our products, new risks and side effects associated with our products may be discovered. In addition,
supplemental clinical trials that may be conducted on a drug following its initial approval may produce findings that are inconsistent with the trial results previously submitted to regulatory authorities. As a result, regulatory authorities may
revoke their approvals, or we may be required to conduct additional clinical trials, make changes in labeling of our product, reformulate our product or make changes and obtain new approvals for our and our suppliers manufacturing facilities.
We also might have to withdraw or recall our products from the marketplace. Any safety concerns with respect to a product may also result in a significant drop in the potential sales of that product, damage to our reputation in the marketplace, or
result in us becoming subject to lawsuits, including class actions. Any of these results could decrease or prevent any sales of our approved product or substantially increase the costs and expenses of commercializing and marketing our product.

We are subject to uncertainty relating to reimbursement policies which could hinder or prevent the commercial success of
our drug candidates.

Our ability to commercialize our product candidates successfully will depend in part on the coverage
and reimbursement levels set by governmental authorities, private health insurers and other third-party payors. As a threshold for coverage and reimbursement, third-party payors generally require that drug products have been approved for marketing
by the FDA. Third-party payors also are increasingly challenging the effectiveness of and prices charged for medical products and services. We may not obtain adequate third-party coverage or reimbursement for our drug candidates or we may be
required to sell our drug candidates at prices that are below our expectations.

We expect that private insurers will consider
the efficacy, cost effectiveness and safety of our drug candidates in determining whether to approve reimbursement for our drug candidates and at what level. Obtaining these approvals can be a time consuming and expensive process. Our business would
be materially adversely affected if we do not receive approval for reimbursement of our drug candidates from private insurers on a timely or satisfactory basis. Our business could also be adversely affected if private insurers, including managed
care organizations, the Medicare program or other reimbursing bodies or payors limit the indications for which our drug candidates will be reimbursed to a smaller set than we believe it is effective in treating.



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In some foreign
countries, particularly Canada and the countries of Europe, the pricing of prescription pharmaceuticals is subject to strict governmental control. In these countries, pricing negotiations with governmental authorities can take six to 12 months
or longer after the receipt of regulatory approval and product launch. To obtain favorable reimbursement for the indications sought or pricing approval in some countries, we may be required to conduct a clinical trial that compares the
cost-effectiveness of our drug candidates to other available therapies. If reimbursement for our products is unavailable in any country in which reimbursement is sought, limited in scope or amount, or if pricing is set at unsatisfactory levels, our
business could be materially harmed.

We expect to experience pricing pressures in connection with the sale of our drug
candidates and our future products due to the potential healthcare reforms discussed below, as well as the trend toward programs aimed at reducing health care costs, the increasing influence of health maintenance organizations and additional
legislative proposals.

Healthcare reform measures could hinder or prevent our product candidates commercial success.

The U.S. government and other governments have shown significant interest in pursuing healthcare reform. Any
government-adopted reform measures could adversely impact the pricing of healthcare products and services in the U.S. or internationally and the amount of reimbursement available from governmental agencies or other third party payors. The continuing
efforts of the U.S. and foreign governments, insurance companies, managed care organizations and other payors of health care services to contain or reduce health care costs may adversely affect our ability to set prices for our products which we
believe are fair, and our ability to generate revenues and achieve and maintain profitability.

In both the U.S. and some
foreign jurisdictions, there have been a number of legislative and regulatory proposals and initiatives to change the health care system in ways that could affect our ability to sell our products profitably. Some of these proposed and implemented
reforms could result in reduced reimbursement rates for our potential products, which would adversely affect our business strategy, operations and financial results. For example, in March 2010, President Obama signed into law a legislative overhaul
of the U.S. healthcare system, known as the Patient Protection and Affordable Care Act of 2010, as amended by the Healthcare and Education Affordability Reconciliation Act of 2010. This law, which we refer to as the PPACA, may have far reaching
consequences for biopharmaceutical companies like us. As a result of this new legislation, substantial changes could be made to the current system for paying for healthcare in the United States, including changes made in order to extend medical
benefits to those who currently lack insurance coverage. Extending coverage to a large population could substantially change the structure of the health insurance system and the methodology for reimbursing medical services and drugs. These
structural changes could entail modifications to the existing system of private payors and government programs, such as Medicare and Medicaid, creation of a government-sponsored healthcare insurance source, or some combination of both, as well as
other changes. Restructuring the coverage of medical care in the United States could impact the reimbursement for prescribed drugs, including our product candidates. If reimbursement for our approved product candidates, if any, is substantially less
that we expect in the future, or rebate obligations associated with them are substantially increased, our business could be materially and adversely impacted.

In addition, the Medicare Prescription Drug Improvement and Modernization Act of 2003 reformed the way Medicare will cover and reimburse for pharmaceutical products. This legislation could also decrease
the coverage and price that we may receive for our products. Other third-party payors are increasingly challenging the prices charged for medical products and services. It will be time consuming and expensive for us to go through the process of
seeking reimbursement from Medicare and private payors. Our products may not be considered cost-effective, and coverage and reimbursement may not be available or sufficient to allow us to sell our products on a profitable basis.

Further federal and state proposals and health care reforms could limit the prices that can be charged for the product candidates that we
develop and may further limit our commercial opportunity. Our results of operations could be materially adversely affected by the PPACA, by the Medicare prescription drug coverage legislation, by the possible effect of such current or future
legislation on amounts that private insurers will pay and by other health care reforms that may be enacted or adopted in the future.

Our business could be harmed if we are unable to comply with applicable fraud and abuse and other laws and regulations where our drug candidates may ultimately be sold.

As our pipeline of drug candidates matures, we are becoming increasingly subject to extensive and complex laws and regulations, including
but not limited to health care fraud and abuse and patient privacy laws and regulations by both the federal government and the states in which we conduct our business. These laws and regulations include:



| |  |  | the federal healthcare program anti-kickback law, which prohibits, among other things, persons from soliciting, receiving or providing remuneration,
directly or indirectly, to induce either the referral of an individual, for an item or service or the purchasing or ordering of a good or service, for which payment may be made under federal healthcare programs such as the Medicare and Medicaid
programs;
| | - |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | federal false claims laws which prohibit, among other things, individuals or entities from knowingly presenting, or causing to be presented, claims for
payment from Medicare, Medicaid, or other third-party payors that are false or fraudulent, and which may apply to entities like us which provide coding and billing advice to customers;
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



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| |  |  | the federal Health Insurance Portability and Accountability Act of 1996, which prohibits executing a scheme to defraud any healthcare benefit program
or making false statements relating to healthcare matters and which also imposes certain requirements relating to the privacy, security and transmission of individually identifiable health information;
| | - |  | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | the Federal Food, Drug, and Cosmetic Act, which among other things, strictly regulates drug product marketing, prohibits manufacturers from marketing
drug products for off-label use and regulates the distribution of drug samples; and
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | state law equivalents of each of the above federal laws, such as anti-kickback and false claims laws which may apply to items or services reimbursed by
any third-party payor, including commercial insurers, and state laws governing the privacy and security of health information in certain circumstances, many of which differ from each other in significant ways and often are not preempted by federal
laws, thus complicating compliance efforts.
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

If our operations are found to be in violation of any of the
laws described above or any governmental regulations that apply to us, we may be subject to penalties, including civil and criminal penalties, damages, fines and the curtailment or restructuring of our operations. Any penalties, damages, fines,
curtailment or restructuring of our operations could adversely affect our ability to operate our business and our financial results. We are developing and implementing a corporate compliance program designed to ensure that we will market and sell
any drug candidates that we successfully develop in compliance with all applicable U.S. laws and regulations, but we cannot guarantee that this program will protect us from governmental investigations or other actions or lawsuits stemming from a
failure to be in compliance with such laws or regulations. If any such actions are instituted against us, and we are not successful in defending ourselves or asserting our rights, those actions could have a significant impact on our business,
including the imposition of significant fines or other sanctions.

Risks Related to Our Field

Our competitors and potential competitors may develop products that make ours less attractive or obsolete.

We seek to develop new drugs for cancer and related conditions. The cancer therapeutic segment of the pharmaceutical industry is highly
competitive and rapidly changing. Many large pharmaceutical and biotechnology companies, academic institutions, governmental agencies and other public and private research organizations are pursuing the development of novel drugs that target various
forms of cancer. We currently face, and expect to continue to face, intense and increasing competition as new products enter the market and advanced technologies become available. Moreover, there are a number of large pharmaceutical companies
currently marketing and selling products to treat cancer, including Bristol-Myers Squibb Company, F. Hoffmann-La Roche Ltd. and its subsidiary Genentech, Inc., Novartis AG and Pfizer, Inc. In addition to currently approved drugs, there are a
significant number of drugs that are currently under development and may become available in the future for the treatment of various forms of cancer. We are also aware of a number of companies seeking to develop drug candidates directed to the same
biological targets that our own drug candidates are designed to inhibit. Specifically, we are aware of numerous companies that have clinical development programs for compounds targeting Hsp90, which is the target of IPI-504 and IPI-493. These
companies include, without limitation, Bristol Myers Squibb Company, Biogen Idec Inc., Synta Pharmaceuticals Corp., Vernalis plc (in collaboration with Novartis), Pfizer, Inc., Astex Therapeutics Limited, Exelixis, Inc., Myriad Pharmaceuticals,
Inc., Kyowa Hakko Kirin Co. Ltd., and Abraxis Bioscience, Inc. In addition, Genentech, Inc. (through its collaboration with Curis, Inc.), Bristol Myers Squibb Company (through its collaboration with Exelixis, Inc.), Novartis AG and Pfizer, Inc. are
developing drugs targeting the Hedgehog pathway, which is also being targeted by IPI-926. Also, we believe that Ironwood Pharmaceuticals, Inc. is developing inhibitors of FAAH. Finally, we believe that Novartis AG, Pfizer, Inc., Semafore
Pharmaceuticals, Inc., Bayer AG, GlaxoSmithKline plc, Calistoga Pharmaceuticals, Inc., sanofi-aventis (through its collaboration with Exelixis, Inc.), Genentech, Inc. and Oncothyreon Inc. are developing drugs that target PI3K.

Many of our competitors have:



| |  |  | significantly greater financial, technical and human resources than us, and may be better equipped to discover, develop, manufacture and commercialize
drug candidates;
| | - |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | more extensive experience in preclinical testing and clinical trials, obtaining regulatory approvals and manufacturing and marketing pharmaceutical
products; and/or
| | - |  | --------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | drug candidates that have been approved or are in later-stage clinical development than our own drug candidates.
| | - |  | ----------------------------------------------------------------------------------------------------------------

Our competitors may commence and complete clinical testing of their product candidates, obtain regulatory approvals, and begin
commercialization of their products sooner than we and/or our strategic alliance partners may for our own drug candidates. These competitive products may have superior safety or efficacy, have more attractive pharmacologic properties, or may be
manufactured less expensively than our drug candidates. If we are unable to compete effectively against these companies on the basis of safety, efficacy or cost, then we may not be able to commercialize our drug candidates or achieve a competitive
position in the market. This would adversely affect our ability to generate revenues.



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We may have
significant product liability exposure that may harm our business and our reputation.

We face exposure to significant
product liability or other claims if any of our drug candidates is alleged to have caused harm. These risks are inherent in the testing, manufacturing and marketing of human medicinal products. Although we do not currently commercialize any
products, claims could be made against us based on the use of our drug candidates in clinical trials. We currently have clinical trial insurance and will seek to obtain product liability insurance prior to the commercial launch of any of our drug
candidates. Our insurance may not, however, provide adequate coverage against potential liabilities. Furthermore, clinical trial and product liability insurance is becoming increasingly expensive. As a result, we may be unable to maintain current
amounts of insurance coverage or obtain additional or sufficient insurance at a reasonable cost. If we are sued for any injury caused by our products or product candidates, our liability could exceed our insurance coverage and our total assets, and
we would need to divert management attention to our defense. Claims against us, regardless of their merit or potential outcome, may also generate negative publicity or hurt our ability to recruit investigators and patients to our clinical trials,
obtain physician acceptance of our products, or expand our business.

We work with hazardous materials that may expose us
to liability.

Our activities involve the controlled storage, use and disposal of hazardous materials, including infectious
agents, corrosive, explosive and flammable chemicals, various radioactive compounds, and compounds known to cause birth defects. We are subject to certain federal, state and local laws and regulations governing the use, manufacture, storage,
handling and disposal of these hazardous materials. We incur significant costs to comply with these laws and regulations. In addition, we cannot eliminate the risk of accidental contamination or injury from these materials. In the event of an
accident, regulatory authorities may curtail our use of these materials, and we could be liable for any civil damages that result. These damages may exceed our financial resources or insurance coverage, and may seriously harm our business.
Additionally, an accident could damage, or force us to shut down, our operations.

Security breaches may disrupt our
operations and harm our operating results.

Our network security and data recovery measures may not be adequate to protect
against computer viruses, break-ins, and similar disruptions from unauthorized tampering with our computer systems. The misappropriation, theft, sabotage or any other type of security breach with respect to any of our proprietary and confidential
information that is electronically stored, including research or clinical data, could have a material adverse impact on our business, operating results and financial condition. Additionally, any break-in or trespass of our facilities that results in
the misappropriation, theft, sabotage or any other type of security breach with respect to our proprietary and confidential information, including research or clinical data, or that results in damage to our research and development equipment and
assets could have a material adverse impact on our business, operating results and financial condition.

Risks Related
to Intellectual Property

Our success depends substantially upon our ability to obtain and maintain intellectual
property protection for our drug candidates.

We own or hold exclusive licenses to a number of U.S. and foreign patents and
patent applications directed to our drug candidates. Our success depends on our ability to obtain patent protection both in the United States and in other countries for our drug candidates, their methods of manufacture and methods of their use. Our
ability to protect our drug candidates from unauthorized or infringing use by third parties depends substantially on our ability to obtain and enforce our patents. Our lead oral Hsp90 candidate, IPI-493, contains an active pharmaceutical ingredient
for which we believe composition of matter protection is unavailable. Consequently, we have filed patent applications directed to IPI-493 and other novel formulations of this active pharmaceutical ingredient, as well as methods of their use, which
may not provide the same level of protection as composition of matter patent protection on the active pharmaceutical ingredient itself.

Due to evolving legal standards relating to the patentability, validity and enforceability of patents covering pharmaceutical inventions and the claim scope of these patents, our ability to obtain and
enforce patents that may issue from any pending or future patent applications is uncertain and involves complex legal, scientific and factual questions. The standards that the United States Patent and Trademark Office, or PTO, and its foreign
counterparts use to grant patents are not always applied predictably or uniformly and are subject to change. To date, no consistent policy has emerged regarding the breadth of claims allowed in pharmaceutical patents. Thus, we cannot guarantee that
any patents will issue from any pending or future patent applications owned by or licensed to us. Even if patents do issue, we cannot guarantee that the claims of these patents will be held valid or enforceable by a court of law, will provide us
with any significant protection against competitive products, or will afford us a commercial advantage over competitive products. In addition, the U.S. Congress has considered, and may consider in the future, legislation that could change United
States law regarding, among other things, post-grant review of issued patents and the calculation of damages once patent infringement has been determined by a court of law. If enacted into law, these provisions could severely weaken patent
protection in the United States.



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If we do not obtain
adequate intellectual property protection for our products in the United States, competitors could duplicate them without repeating the extensive testing that we had been required to undertake to obtain approval of the products by the FDA.
Regardless of any patent protection, under the current statutory framework the FDA is prohibited by law from approving any generic version of any of our products for up to five years after it has approved our product. Upon the expiration of that
period, or if that time period is altered, the FDA could approve a generic version of our product unless we have patent protection sufficient for us to block that generic version. Without sufficient patent protection, the applicant for a generic
version of our product would only be required to conduct a relatively inexpensive study to show that its product is bioequivalent to our product, and would not have to repeat the studies that we conducted to demonstrate that the product is safe and
effective. In the absence of adequate patent protection in other countries, competitors may similarly be able to obtain regulatory approval in those countries of products that duplicate our products.

The laws of some foreign jurisdictions do not protect intellectual property rights to the same extent as in the United States. Many
companies have encountered significant difficulties in protecting and defending such rights in foreign jurisdictions. Some of our development efforts are performed in China, India, and other countries outside of the United States through third party
contractors. We may not be able to monitor and assess intellectual property developed by these contractors effectively; therefore, we may not appropriately protect this intellectual property and could thus lose valuable intellectual property rights.
In addition, the legal protection afforded to inventors and owners of intellectual property in countries outside of the United States may not be as protective of intellectual property rights as in the United States, and we may, therefore, be unable
to acquire and protect intellectual property developed by these contractors to the same extent as if these development activities were being conducted in the United States. If we encounter difficulties in protecting our intellectual property rights
in foreign jurisdictions, our business prospects could be substantially harmed.

In addition, we rely on intellectual property
assignment agreements with our strategic alliance partners, vendors, employees, consultants, scientific advisors and other collaborators to grant us ownership of new intellectual property that is developed by them. These agreements may not result in
the effective assignment to us of that intellectual property. As a result, our ownership of key intellectual property could be compromised.

Patent interference, opposition or similar proceedings relating to our intellectual property portfolio are costly, and an unfavorable outcome could prevent us from commercializing our drug candidates.

Patent applications in the United States are maintained in confidence for up to 18 months after their filing. In some
cases, however, patent applications remain confidential in the PTO for the entire time prior to issuance as a U.S. patent. Similarly, publication of discoveries in the scientific or patent literature often lags behind actual discoveries.
Consequently, we cannot be certain that we were the first to invent, or the first to file patent applications on, our drug candidates or their therapeutic use. In the event that a third party has also filed a U.S. patent application relating to our
drug candidates or a similar invention, we may have to participate in interference proceedings declared by the PTO or the third party to determine priority of invention in the United States. For example, we are aware of third parties who are
actively researching ansamycin analogs that are similar to IPI-504. These third parties have pending applications related to these analogs, but we have the first published application covering IPI-504. Notwithstanding the fact that we filed the
first patent application related to these analogs, it is possible that an interference proceeding could be declared between our application covering IPI-504 and one or more of these third party applications, even the one of those applications for
which we have secured a license. An adverse decision in an interference proceeding may result in the loss of rights under a patent or patent application. In addition, the cost of interference proceedings could be substantial.

Obtaining and maintaining our patent protection depends on compliance with various procedural, document submission, fee payment and
other requirements imposed by governmental patent agencies, and our patent protection could be reduced or eliminated for non-compliance with these requirements.

The PTO and various foreign governmental patent agencies require compliance with a number of procedural, documentary, fee payment and other provisions during the patent process. There are situations in
which non-compliance can result in abandonment or lapse of a patent or patent application, resulting in partial or complete loss of patent rights in the relevant jurisdiction. In such an event, competitors might be able to enter the market earlier
than would otherwise have been the case.

Claims by third parties of intellectual property infringement are costly and
distracting, and could deprive us of valuable rights we need to develop or commercialize our drug candidates.

Our
commercial success will depend on whether there are third party patents or other intellectual property relevant to our potential products that may block or hinder our ability to develop and commercialize our drug candidates. We may not have
identified all U.S. and foreign patents or published applications that may affect our business either by blocking our ability to manufacture or commercialize our drugs or by covering similar technologies that affect the applicable market. In
addition, we may undertake research and development with respect to potential products, even when we are aware of third party patents that may be relevant to such potential products, on the basis that we may challenge or license such patents. For
example, in our Hsp90 chaperone inhibitor program, we are conducting a clinical trial evaluating the administration of IPI-504 in combination with docetaxel, and we may conduct additional trials with IPI-504 in combination with other therapeutic
agents. We are aware of issued patents and published



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applications directed to combinations of Hsp90 chaperone inhibitors with a variety of other therapeutic agents. We are also aware of patents and patent applications directed to methods of
treating various disorders using a variety of Hsp90 chaperone inhibitors. We are in the process of evaluating the scope and validity of these patents and applications to determine whether we need to obtain one or more licenses.

While we are not currently aware of any litigation or third party claims of intellectual property infringement related to our drug
candidates, the biopharmaceutical industry is characterized by extensive litigation regarding patents and other intellectual property rights. Other parties may obtain patents and claim that the use of our technologies infringes these patents or that
we are employing their proprietary technology without authorization. We could incur substantial costs and diversion of management and technical personnel in defending against any claims that the manufacture and sale of our potential products or use
of our technologies infringes any patents, or defending against any claim that we are employing any proprietary technology without authorization. The outcome of patent litigation is subject to uncertainties that cannot be adequately quantified in
advance, including the demeanor and credibility of witnesses and the identity of the adverse party, especially in pharmaceutical patent cases that may turn on the testimony of experts as to technical facts upon which experts may reasonably disagree.
In the event of a successful claim of infringement against us, we may be required to:



| |  |  | pay substantial damages;
| | - |  | ------------------------



| |  |  | stop developing, manufacturing and/or commercializing the infringing drug candidates or approved products;
| | - |  | ----------------------------------------------------------------------------------------------------------



| |  |  | develop non-infringing products, technologies and methods; and
| | - |  | --------------------------------------------------------------



| |  |  | obtain one or more licenses from other parties, which could result in our paying substantial royalties or the granting of cross-licenses to our
technologies.
| | - |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------

If this were to occur, we may be unable to commercialize the affected products, or we may elect to cease
certain of our business operations, either of which could severely harm our business.

We may undertake infringement or
other legal proceedings against third parties, causing us to spend substantial resources on litigation and exposing our own intellectual property portfolio to challenge.

Competitors may infringe our patents. To prevent infringement or unauthorized use, we may need to file infringement suits, which are expensive and time-consuming. In an infringement proceeding, a court
may decide that one or more of our patents is invalid, unenforceable, or both. Even if the validity of our patents is upheld, a court may refuse to stop the other party from using the technology at issue on the ground that the other partys
activities are not covered by our patents. In this case, third parties may be able to use our patented technology without paying licensing fees or royalties. Policing unauthorized use of our intellectual property is difficult, and we may not be able
to prevent misappropriation of our proprietary rights, particularly in countries where the laws may not protect such rights as fully as in the United States. In addition, third parties may affirmatively challenge our rights to, or the scope or
validity of, our patent rights.

Confidentiality agreements may not adequately prevent disclosure of trade secrets and
other proprietary information.

In order to protect our proprietary technology, we rely in part on confidentiality
agreements with our vendors, strategic alliance partners, employees, consultants, scientific advisors, clinical investigators and other collaborators. We generally require each of these individuals and entities to execute a confidentiality agreement
at the commencement of a relationship with us. These agreements may not effectively prevent disclosure of confidential information, and may not provide an adequate remedy in the event of unauthorized disclosure of confidential information or other
breaches of the agreements.

In addition, we may rely on trade secrets to protect our technology, especially where we do not
believe patent protection is appropriate or obtainable. Trade secrets are, however, difficult to protect. Others may independently discover our trade secrets and proprietary information, and in such case we could not assert any trade secret rights
against such party. Enforcing a claim that a party illegally obtained and is using our trade secrets is difficult, expensive and time consuming, and the outcome is unpredictable. In addition, courts outside of the United States may be less willing
to protect trade secrets. Costly and time-consuming litigation could be necessary to seek to enforce and determine the scope of our proprietary rights and could result in a diversion of managements attention, and failure to obtain or maintain
trade secret protection could adversely affect our competitive business position.

If we fail to obtain necessary or useful
licenses to intellectual property, we could encounter substantial delays in the research, development and commercialization of our drug candidates.

We may decide to license third-party technology that we deem necessary or useful for our business. We may not be able to obtain these licenses at a reasonable cost, or at all. If we do not obtain
necessary licenses, we could encounter substantial delays in developing and commercializing our drug candidates while we attempt to develop alternative technologies, methods and drug candidates, which we may not be able to accomplish. Furthermore,
if we fail to comply with our obligations under our third party license agreements, we could lose license rights that are important to our business.



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Risks Associated
with Our Common Stock

Our common stock may have a volatile trading price and low trading volume.

The market price of our common stock could be subject to significant fluctuations. Some of the factors that may cause the market price of
our common stock to fluctuate include:



| |  |  | the results of our current and any future clinical trials of IPI-504, IPI-493, IPI-926, IPI-940 and our other drug candidates;
| | - |  | ------------------------------------------------------------------------------------------------------------------------------



| |  |  | the results of preclinical studies and planned clinical trials of our discovery-stage programs;
| | - |  | -----------------------------------------------------------------------------------------------



| |  |  | product portfolio decisions resulting in the delay or termination of our product development programs;
| | - |  | ------------------------------------------------------------------------------------------------------



| |  |  | future sales of, and the trading volume in, our common stock;
| | - |  | -------------------------------------------------------------



| |  |  | our entry into key agreements, including those related to the acquisition or in-licensing of new programs, or the termination of key agreements,
including our strategic alliance agreements with Purdue and Mundipharma and our development and license agreement with Intellikine, Inc.;
| | - |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| |  |  | the results and timing of regulatory reviews relating to the approval of our drug candidates;
| | - |  | ---------------------------------------------------------------------------------------------



| |  |  | the initiation of, material developments in, or conclusion of litigation to enforce or defend any of our intellectual property rights;
| | - |  | --------------------------------------------------------------------------------------------------------------------------------------



| |  |  | the initiation of, material developments in, or conclusion of litigation to defend product liability claims;
| | - |  | ------------------------------------------------------------------------------------------------------------



| |  |  | the failure of any of our drug candidates, if approved, to achieve commercial success;
| | - |  | --------------------------------------------------------------------------------------



| |  |  | the results of clinical trials conducted by others on drugs that would compete with our drug candidates;
| | - |  | --------------------------------------------------------------------------------------------------------



| |  |  | issues in manufacturing our drug candidates or any approved products;
| | - |  | ---------------------------------------------------------------------



| |  |  | the loss of key employees;
| | - |  | --------------------------



| |  |  | changes in estimates or recommendations by securities analysts who cover our common stock;
| | - |  | ------------------------------------------------------------------------------------------



| |  |  | future financings through the issuance of equity or debt securities or otherwise;
| | - |  | ---------------------------------------------------------------------------------



| |  |  | changes in the structure of health care payment systems;
| | - |  | --------------------------------------------------------



| |  |  | our cash position and period-to-period fluctuations in our financial results; and
| | - |  | ---------------------------------------------------------------------------------



| |  |  | general and industry-specific economic conditions.
| | - |  | --------------------------------------------------

Moreover, the stock markets in general have experienced substantial volatility that has often been unrelated to the operating performance of individual companies. These broad market fluctuations may also
adversely affect the trading price of our common stock.

In the past, when the market price of a stock has been volatile, as
our stock price may be, holders of that stock have occasionally brought securities class action litigation against the company that issued the stock. If any of our stockholders were to bring a lawsuit of this type against us, even if the lawsuit is
without merit, negative publicity could be generated and we could incur substantial costs defending the lawsuit. A stockholder lawsuit could also divert the time and attention of our management.

We do not anticipate paying cash dividends, so you must rely on stock price appreciation for any return on your investment.

We anticipate retaining any future earnings for reinvestment in our research and development programs. Therefore, we do
not anticipate paying cash dividends in the future. As a result, only appreciation of the price of our common stock will provide a return to stockholders. Investors seeking cash dividends should not invest in our common stock.

Our stockholder rights plan, anti-takeover provisions in our organizational documents, and Delaware law may make an acquisition of us
difficult.

We are a party to a stockholder rights plan, also referred to as a poison pill, which is intended to deter a
hostile takeover by making any proposed acquisition of us more expensive and less desirable to the potential acquirer.

In
addition, we are incorporated in Delaware. Anti-takeover provisions of Delaware law and our organizational documents may make a change in control more difficult. Also, under Delaware law, our board of directors may adopt additional anti-takeover
measures. For example, our charter authorizes our board of directors to issue up to 901,000 shares of currently undesignated preferred stock and to determine the terms of those shares of stock without any further action by our stockholders. If our
board of directors exercises this power, it could be more difficult for a third party to acquire a majority of our outstanding voting stock. Our charter and by-laws also contain provisions limiting the ability of stockholders to call special
meetings of stockholders.



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Our stock incentive
plan generally permits our board of directors to provide for acceleration of vesting of options granted under that plan in the event of certain transactions that result in a change of control. If our board of directors uses its authority to
accelerate vesting of options, this action could make an acquisition more costly, and it could prevent an acquisition from going forward.

Under Section 203 of the Delaware General Corporation Law, a corporation may not engage in a business combination with any holder of 15% or more of its capital stock until the holder has held the
stock for three years unless, among other possibilities, the board of directors approves the transaction. Our board of directors could use this provision to vote against any such transaction. The existence of the foregoing provisions could limit the
price that investors might be willing to pay in the future for shares of our common stock.

Our officers, directors and
major shareholders may be able to exert significant control over the company, which may make an acquisition of us difficult.

Our executive officers, directors, certain affiliates and other major shareholders control approximately 31% of our outstanding common
stock and have the ability to influence the company through this ownership position. For example, as a result of this concentration of ownership, these stockholders, if acting together, may have the ability to determine the outcome of matters
submitted to our stockholders for approval, including the election and removal of directors and any merger or similar transaction. This concentration of ownership may, therefore, harm the market price of our common stock by:



| |  |  | delaying, deferring or preventing a change in control of Infinity;
| | - |  | ------------------------------------------------------------------



| |  |  | impeding a merger, consolidation, takeover or other business combination involving Infinity; or
| | - |  | -----------------------------------------------------------------------------------------------



| |  |  | discouraging a potential acquirer from making a tender offer or otherwise attempting to obtain control of Infinity.
| | - |  | -------------------------------------------------------------------------------------------------------------------



|Item 6. | Exhibits
|------- | --------

(a) Exhibits.

The exhibits listed in the Exhibit Index are included in this report.



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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.



|                       |  |                                |  |                                                      
|---------------------- |  | ------------------------------ |  | -----------------------------------------------------
|                       |  | INFINITY PHARMACEUTICALS, INC.
|                       |  |                               
|Date: November 9, 2010 |  | By:                            |  | /S/    ADELENE Q.
PERKINS                            
|                       |  |                                |  | Adelene Q. Perkins                                   
|                       |  |                                |  | President and Chief Executive Officer                
|                       |  |                                |  | (Principal Executive and Principal Financial Officer)



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EXHIBIT INDEX



|        |  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|------- |  | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|Exhibit |  | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|        | 
|3.1     |  | Restated Certificate of Incorporation of the Registrant. Previously filed as Exhibit 3.1 to the Registrants Quarterly Report on Form 10-Q for the quarter ended June 30, 2007
(File No. 000-31141) and incorporated herein by reference.                                                                                                                                                                                                                                                                                                                
|        | 
|3.2     |  | Amended and Restated Bylaws of the Registrant. Previously filed as Exhibit 3.1 to the Registrants Current Report on Form 8-K filed on March 17, 2009 (File No. 000-31141) and
incorporated herein by reference.                                                                                                                                                                                                                                                                                                                                         
|        | 
|4.1     |  | Form of Common Stock Certificate. Previously filed as Exhibit 4.1 to the Registrants Annual Report on Form 10-K for the year ended December 31, 2007 (File No. 000-31141) and
incorporated herein by reference.                                                                                                                                                                                                                                                                                                                                         
|        | 
|4.2     |  | Rights Agreement between the Registrant and American Stock Transfer & Trust Company dated February 13, 2003, which includes the form of Certificate of Designation for the Series
A junior participating preferred stock as Exhibit A, the form of Rights Certificate as Exhibit B and the Summary of Rights to Purchase Series A junior participating preferred stock as Exhibit C. Previously filed as Exhibit 4.2 to the
Registrants Current Report on Form 8-K filed on February 24, 2003 (File No. 000-31141) and incorporated herein by reference.
|        | 
|4.3     |  | First Amendment to the Rights Agreement between the Registrant and American Stock Transfer & Trust Company dated April 11, 2006. Previously filed as Exhibit 4.1 to the
Registrants Current Report on Form 8-K filed on April 12, 2006 (File No. 000-31141) and incorporated herein by reference.                                                                                                                                                                                                                                                       
|        | 
|4.4     |  | Second Amendment to the Rights Agreement between the Registrant and American Stock Transfer & Trust Company, LLC dated November 19, 2008. Previously filed as Exhibit 4.1 to the
Registrants Current Report on Form 8-K filed on November 20, 2008 (File No. 000-31141) and incorporated herein by reference.                                                                                                                                                                                                                                           
|        | 
|31.1    |  | Certification of principal executive and principal financial officer pursuant to Rule 13a-14(a)/15d-14(a) of the Securities Exchange Act of 1934, as amended. Filed
herewith.                                                                                                                                                                                                                                                                                                                                                                            
|        | 
|32.1    |  | Certification of principal executive and principal financial officer pursuant to 18 U.S.C. §1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002. Filed
herewith.                                                                                                                                                                                                                                                                                                                                                                  



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