The Company has an investment policy that includes guidelines on acceptable investment securities, minimum credit quality, maturity parameters, and concentration and diversification. The Company has invested its excess cash primarily in direct obligations of the U.S. government and its agencies, other debt securities guaranteed by the U.S. government, and money market funds that invest in U.S. government securities. The Company considers its marketable securities to be “available-for-sale,” as defined by authoritative guidance issued by the Financial Accounting Standards Board (“FASB”). These assets are carried at fair value and the unrealized gains and losses are included in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity. If the decline in the value of a marketable security in the Company’s investment portfolio is deemed to be other-than-temporary, the Company writes down the security to its current fair value and recognizes a loss as a charge against income. As described under “Use of Estimates” below, the Company reviews its portfolio of marketable securities, using both quantitative and qualitative factors, to determine if declines in fair value below cost are other-than-temporary.

The Company’s trade accounts receivable represents amounts due from its distributors and specialty pharmacies (collectively, the Company’s “customers”), which are all located in the United States. The Company monitors the financial performance and credit worthiness of its large customers so that it can properly assess and respond to changes in their credit profile. The Company provides reserves against trade receivables for estimated losses that may result from a customer’s inability to pay. Amounts determined to be uncollectible are written-off against the reserve. As of December 31, 2011 and 2010, there were no reserves against trade accounts receivable. In addition, during the years ended December 31, 2011, 2010 and 2009, no trade accounts receivable were written-off.

Inventories are stated at the lower of cost or estimated realizable value. The Company determines the cost of inventory using the first-in, first-out, or FIFO, method. The Company capitalizes inventory costs associated with the Company’s products prior to regulatory approval when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized; otherwise, such costs are expensed as research and development. The Company periodically analyzes its inventory levels to identify inventory that may expire prior to expected sale or has a cost basis in excess of its estimated realizable value, and writes-down such inventories as appropriate. In addition, the Company’s products are subject to strict quality control and monitoring which the Company performs throughout the manufacturing process. If certain batches or units of product no longer meet quality specifications or become obsolete due to expiration, the Company records a charge to cost of goods sold to write down such unmarketable inventory to its estimated realizable value.

Property, plant, and equipment are stated at cost, net of accumulated depreciation. Depreciation is provided on a straight-line basis over the estimated useful lives of the assets. Expenditures for maintenance and repairs which do not materially extend the useful lives of the assets are charged to expense as incurred. The cost and accumulated depreciation or amortization of assets retired or sold are removed from the respective accounts, and any gain or loss is recognized in operations. The estimated useful lives of property, plant, and equipment are as follows:

As a result of the Company’s research and development efforts, the Company obtains and applies for patents to protect proprietary technology and inventions. All costs associated with patents for product candidates under development are expensed as incurred. Patent costs related to commercial products are capitalized and amortized over the shorter of their estimated useful life or the remaining patent term. To date, the Company has no capitalized patent costs.

The Company earns collaboration revenue in connection with collaboration agreements to develop and commercialize product candidates and utilize the Company’s technology platforms. The terms of these agreements typically include non-refundable up-front licensing payments, research progress (milestone) payments, and payments for development activities. Non-refundable up-front license payments, where continuing involvement is required of the Company, are deferred and recognized over the related performance period. The Company estimates its performance period based on the specific terms of each agreement, and adjusts the performance periods, if appropriate, based on the applicable facts and circumstances. Although the Company did not enter into, or materially modify, any collaboration arrangements with multiple-deliverables during the year ended December 31, 2011, any future arrangements with multiple deliverables will be divided into separate units of accounting if the deliverables in the arrangement meet certain criteria, including whether the delivered item or items has value to the collaborator on a standalone basis. Payments which are based on achieving a specific performance milestone, involving a degree of risk, are recognized as revenue when the milestone is achieved and the related payment is due and non-refundable, provided there is no future service obligation associated with that milestone. Substantive performance milestones typically consist of significant achievements in the development life-cycle of the related product candidate, such as completion of clinical trials, filing for approval with regulatory agencies, and receipt of approvals by regulatory agencies. In determining whether a payment is deemed to be a substantive performance milestone, the Company takes into consideration (i) the enhancement in value to the related development product candidate, (ii) the Company’s performance and relative level of effort required to achieve the milestone, (iii) whether the milestone relates solely to past performance, and (iv) whether the milestone payment is considered reasonable relative to all of the deliverables and payment terms. Payments for achieving milestones which are not considered substantive are deferred and recognized over the related performance period.

The Company enters into collaboration agreements that include varying arrangements regarding which parties perform and bear the costs of research and development activities. The Company may share the costs of research and development activities with a collaborator, such as in the Company’s EYLEAÒ collaboration with Bayer HealthCare LLC, or the Company may be reimbursed for all or a significant portion of the costs of the Company’s research and development activities, such as in the Company’s ZALTRAP® (aflibercept) and antibody collaborations with Sanofi. The Company records its internal and third-party development costs associated with these collaborations as research and development expenses. When the Company is entitled to reimbursement of all or a portion of the research and development expenses that it incurs under a collaboration, the Company records those reimbursable amounts as collaboration revenue proportionately as the Company recognizes its expenses. If the collaboration is a cost-sharing arrangement in which both the Company and its collaborator perform development work and share costs, in periods when the Company’s collaborator incurs development expenses that benefit the collaboration and Regeneron, the Company also recognizes, as additional research and development expense, the portion of the collaborator’s development expenses that the Company is obligated to reimburse. In certain cases, the Company may also share the costs of pre-launch commercialization activities with its collaborators. The Company records its share of these costs as a reduction of collaboration revenue.

In connection with non-refundable licensing payments, the Company’s performance period estimates are principally based on projections of the scope, progress, and results of its research and development activities. Due to the variability in the scope of activities and length of time necessary to develop a drug product, changes to development plans as programs progress, and uncertainty in the ultimate requirements to obtain governmental approval for commercialization, revisions to performance period estimates are likely to occur periodically, and could result in material changes to the amount of revenue recognized each year in the future. In addition, estimated performance periods may change if development programs encounter delays, or the Company and its collaborators decide to expand or contract the clinical plans for a drug candidate in various disease indications. Also, if a collaborator terminates an agreement in accordance with the terms of the agreement, the Company would recognize any unamortized remainder of an up-front or previously deferred payment at the time of the termination.

The Company enters into non-exclusive license agreements with third parties that allow the third party to utilize the Company’s VelocImmune® technology in its internal research programs. The terms of these agreements include up-front payments and entitle the Company to receive royalties on any future sales of products discovered by the third party using the Company’s VelocImmune® technology. Up-front payments under these agreements, where continuing involvement is required of the Company, are deferred and recognized ratably over their respective license periods.

Product sales consist of U.S. sales of the Company’s two marketed products, EYLEAÒ and ARCALYSTÒ. Revenue from product sales is recognized when persuasive evidence of an arrangement exists, title to product and associated risk of loss have passed to the customer, the price is fixed or determinable, collection from the customer is reasonably assured, the Company has no further performance obligations, and returns can be reasonably estimated. The Company’s written contracts with its customers stipulate product is shipped freight on board destination (FOB destination). The Company records revenue from product sales upon delivery to its customers.

The Company sells EYLEAÒ in the United States to three distributors and several specialty pharmacies. The Company sells ARCALYSTÒ in the United States to two specialty pharmacies. Under these distribution models, the distributors and specialty pharmacies generally take physical delivery of product. For EYLEAÒ, the distributors and specialty pharmacies generally sell the product directly to healthcare providers; whereas for ARCALYSTÒ, the specialty pharmacies sell the product directly to patients.

Revenue from product sales are recorded net of applicable provisions for prompt pay discounts, rebates and chargebacks under governmental programs (including Medicaid), product returns, distribution-related fees, and other sales-related deductions. Calculating these provisions involves estimates and judgments. The Company reviews its estimates of rebates, chargebacks, and other applicable provisions each period and records any necessary adjustments in the current period’s net product sales.

Prompt Pay Discounts: No prompt pay discounts are currently offered to the Company’s customers on sales of EYLEAÒ. In connection with sales of ARCALYSTÒ, the Company offers discounts to its customers for prompt payments. The Company estimates these discounts based on customer terms and historical experience, and expects that its customers will always take advantage of this discount. Therefore, the Company accrues 100% of the prompt pay discount that is based on the gross amount of each ARCALYSTÒ invoice, at the time of sale.

Government Rebates and Chargebacks: The Company estimates reductions to product sales for Medicaid and Veterans’ Administration (VA) programs, and for certain other qualifying federal and state government programs. Based upon the Company’s contracts with government agencies, statutorily-defined discounts applicable to government-funded programs, historical experience, and, in the case of EYLEAÒ, estimated payer mix based on third-party market research data, the Company estimates and records an allowance for rebates and chargebacks. The Company’s liability for Medicaid rebates consists of estimates for claims that a state will make for a current quarter, claims for prior quarters that have been estimated for which an invoice has not been received, and invoices received for claims from prior quarters that have not been paid. The Company’s reserves related to discounted pricing offered to VA, Public Health Services (PHS), and other institutions (collectively, “qualified healthcare providers”) represent the Company’s estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices the Company charges to its customers (i.e., distributors and specialty pharmacies). The Company’s customers charge the Company for the difference between what they pay for the products and the ultimate selling price to the qualified healthcare providers. The Company’s reserve for this discounted pricing is based on expected sales to qualified healthcare providers and the chargebacks that customers have already claimed.

Product Returns: Consistent with industry practice, the Company offers its customers a limited right to return product purchased directly from the Company, which is principally based upon the product’s expiration date. The Company will accept returns for three months prior to and up to six months after the product expiration date. Product returned is generally not resalable given the nature of the Company’s products and method of administration. The Company develops estimates for product returns based upon historical experience, inventory levels in the distribution channel, and other relevant factors.

The Company has developed estimates for EYLEAÒ product returns, based on several factors, including (i) the Company’s historical experience to date, and the Company’s expectation, that its customers will not stock significant supplies of EYLEAÒ due to contractual limitations and other mitigating circumstances, (ii) historical industry information regarding product return rates for similar specialty products, and (iii) the shelf life of the product. Estimates for ARCALYSTÒ product returns have been developed based primarily on historical returns experience; to date, actual ARCALYSTÒ product returns have been negligible. The Company monitors product supply levels in the distribution channel, as well as sales by its customers of EYLEAÒ to healthcare providers and ARCALYSTÒ to patients using product-specific data provided by its customers. If necessary, the Company’s estimates of product returns may be adjusted in the future based on actual returns experience, known or expected changes in the marketplace, or other factors.

Research and development expenses include costs directly attributable to the conduct of research and development programs, including the cost of salaries, payroll taxes, employee benefits, materials, supplies, depreciation on and maintenance of research equipment, costs related to research collaboration and licensing agreements, the cost of services provided by outside contractors, including services related to the Company’s clinical trials, clinical trial expenses, the full cost of manufacturing drug for use in research, preclinical development, and clinical trials, amounts that the Company is obligated to reimburse to collaborators for research and development expenses that they incur, and the allocable portions of facility costs, such as rent, utilities, insurance, repairs and maintenance, depreciation, and general support services. All costs associated with research and development are expensed.

Clinical trial costs are a significant component of research and development expenses and include costs associated with third-party contractors. The Company outsources a substantial portion of its clinical trial activities, utilizing external entities such as contract research organizations (“CROs”), independent clinical investigators, and other third-party service providers to assist the Company with the execution of its clinical studies. For each clinical trial that the Company conducts, certain clinical trial costs are expensed immediately, while others are expensed over time based on the expected total number of patients in the trial, the rate at which patients enter the trial, and/or the period over which clinical investigators or CROs are expected to provide services.

Clinical activities which relate principally to clinical sites and other administrative functions to manage the Company’s clinical trials are performed primarily by CROs. CROs typically perform most of the start-up activities for the Company’s trials, including document preparation, site identification, screening and preparation, pre-study visits, training, and program management. On a budgeted basis, these start-up costs are typically 10% to 20% of the total contract value. On an actual basis, this percentage range can be significantly wider, as many of the Company’s contracts with CROs are either expanded or reduced in scope compared to the original budget, while start-up costs for the particular trial may not change materially. These start-up costs usually occur within a few months after the contract has been executed and are event driven in nature. The remaining activities and related costs, such as patient monitoring and administration, generally occur ratably throughout the life of the individual contract or study. In the event of early termination of a clinical trial, the Company accrues and recognizes expenses in an amount based on its estimate of the remaining non-cancelable obligations associated with the winding down of the clinical trial and/or penalties.

For clinical study sites, where payments are made periodically on a per-patient basis to the institutions performing the clinical study, the Company accrues expense on an estimated cost-per-patient basis, based on subject enrollment and activity in each quarter. The amount of clinical study expense recognized in a quarter may vary from period to period based on the duration and progress of the study, the activities to be performed by the sites each quarter, the required level of patient enrollment, the rate at which patients actually enroll in and drop-out of the clinical study, and the number of sites involved in the study. Clinical trials that bear the greatest risk of change in estimates are typically those that have a significant number of sites, require a large number of patients, have complex patient screening requirements, and span multiple years. During the course of a trial, the Company adjusts its rate of clinical expense recognition if actual results differ from the Company’s estimates. The Company’s estimates and assumptions for clinical expense recognition could differ significantly from its actual results, which could cause material increases or decreases in research and development expenses in future periods when the actual results become known.

The Company recognizes stock-based compensation expense for grants of stock option awards and restricted stock under the Company’s Long-Term Incentive Plan to employees and non-employee members of the Company’s board of directors based on the grant-date fair value of those awards. The grant-date fair value of an award is generally recognized as compensation expense over the award’s requisite service period. In addition, the Company has granted performance-based stock option awards which vest based upon the optionee satisfying certain performance and service conditions as defined in the agreements. Potential compensation cost, measured on the grant date, related to these performance options will be recognized only if, and when, the Company estimates that these options will vest, which is based on whether the Company consider the options’ performance conditions to be probable of attainment. The Company’s estimates of the number of performance-based options that will vest will be revised, if necessary, in subsequent periods.

The Company uses the Black-Scholes model to compute the estimated fair value of stock option awards. Using this model, fair value is calculated based on assumptions with respect to (i) expected volatility of the Company’s Common Stock price, (ii) the periods of time over which employees and members of the board of directors are expected to hold their options prior to exercise (expected lives), (iii) expected dividend yield on the Common Stock, and (iv) risk-free interest rates. Stock-based compensation expense also includes an estimate, which is made at the time of grant, of the number of awards that are expected to be forfeited. This estimate is revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates.

The Company recognizes deferred tax liabilities and assets for the expected future tax consequences of events that have been included in the financial statements or tax returns. Under this method, deferred tax liabilities and assets are determined on the basis of the difference between the tax basis of assets and liabilities and their respective financial reporting amounts (“temporary differences”) at enacted tax rates in effect for the years in which the differences are expected to reverse. A valuation allowance is established for deferred tax assets for which it is more likely than not that some portion or all of the deferred tax assets will not be realized.

Uncertain tax positions are accounted for in accordance with FASB authoritative guidance, which prescribes a comprehensive model for the manner in which a company should recognize, measure, present, and disclose in its financial statements all material uncertain tax positions that the company has taken or expects to take on a tax return. Those positions, for which management's assessment is that there is more than a 50% probability of sustaining the position upon challenge by a taxing authority based upon its technical merits, are subjected to certain measurement criteria.

Net income (loss) per share, basic and diluted, is computed on the basis of the net income (loss) for the period divided by the weighted average number of shares of Common Stock and Class A Stock outstanding during the period. Basic net income (loss) per share excludes restricted stock awards until vested. Diluted net income per share is based upon the weighted average number of shares of Common Stock and Class A Stock outstanding, and of common stock equivalents outstanding when dilutive. Common stock equivalents include: (i) outstanding stock options and restricted stock awards under the Company’s Long-Term Incentive Plans, which are included under the “treasury stock method” when dilutive, (ii) Common Stock to be issued upon the assumed conversion of the Company’s convertible senior notes, which are included under the “if-converted method” when dilutive, and (iii) Common Stock to be issued upon the exercise of outstanding warrants, which are included under the “treasury stock method” when dilutive. The computation of diluted net loss per share for the years ended December 31, 2011, 2010, and 2009 does not include common stock equivalents, since such inclusion would be antidilutive.

Developing and commercializing new medicines entails significant risk and expense. Before revenues from the commercialization of the Company’s current or future product candidates can be realized, the Company (or its collaborators) must overcome a number of hurdles which include successfully completing research and development and obtaining regulatory approval from the FDA and regulatory authorities in other countries. In addition, the biotechnology and pharmaceutical industries are rapidly evolving and highly competitive, and new developments may render the Company’s products and technologies uncompetitive or obsolete. The Company may be subject to legal claims by third parties seeking to enforce patents to limit or prohibit the Company from marketing or selling its products. The Company is also dependent upon the services of its employees, consultants, collaborators, and certain third-party suppliers, including single-source unaffiliated third-party suppliers of certain raw materials and equipment. Regeneron, as licensee, licenses certain technologies that are important to the Company’s business which impose various obligations on the Company. If Regeneron fails to comply with these requirements, licensors may have the right to terminate the Company’s licenses.

The Company has generally incurred net losses and negative cash flows from operations since its inception. The Company received regulatory approval from the FDA for ARCALYST® for the treatment of CAPS in February 2008 and EYLEAÒ for the treatment of wet AMD in November 2011; however, the Company has not generated significant sales or profits to date from these two drug products. Revenues to date have principally been limited to (i) up-front, license, milestone, and reimbursement payments from the Company’s collaborators and other entities related to the Company’s development activities and technology platforms, (ii) ARCALYST® and EYLEAÒ product sales, (iii) payments for past contract manufacturing activities, and (iv) investment income. Collaboration revenue in 2011 was earned from Sanofi and Bayer HealthCare under collaboration agreements (see Note 3 for the terms of these agreements). These collaboration agreements contain early termination provisions that are exercisable by Sanofi or Bayer HealthCare, as applicable.

In connection with stock option awards, (i) the fair value of stock options on their date of grant using the Black-Scholes option-pricing model, based on assumptions with respect to (a) expected volatility of the Company’s Common Stock price, (b) the periods of time for which employees and members of the Company’s board of directors are expected to hold their options prior to exercise (expected lives), (c) expected dividend yield on the Company’s Common Stock, and (d) risk-free interest rates, which are based on quoted U.S. Treasury rates for securities with maturities approximating the options’ expected lives; (ii) the number of stock option awards that are expected to be forfeited; and (iii) with respect to performance-based stock option awards, if and when the options’ performance conditions are considered to be probable of attainment.

The Company’s determination of whether marketable securities are other-than-temporarily impaired. The Company conducts a review of its portfolio of marketable securities, using both quantitative and qualitative factors, to determine, for securities whose current fair value is less than their cost, whether the decline in fair value below cost is other-than-temporary. In making this determination, the Company considers factors such as the length of time and the extent to which fair value has been less than cost, financial condition and near-term prospects of the issuer, recommendations of investment advisors, and forecasts of economic, market, or industry trends. This review process also includes an evaluation of the Company’s ability and intent to hold individual securities until they mature or their full value can be recovered. This review is subjective and requires a high degree of judgment.

In addition, the Company’s share of EYLEAÒ development expenses incurred by Bayer HealthCare, including the Company’s share of Bayer HealthCare’s estimated EYLEAÒ development expenses for the most recent fiscal quarter, are included in research and development expenses. The Bayer HealthCare estimate for the most recent fiscal quarter is adjusted in the subsequent quarter to reflect actual expenses for the quarter. Also, the Company’s share of ZALTRAP® pre-launch commercialization expenses incurred by Sanofi, including the Company’s share of Sanofi’s estimated ZALTRAP® pre-launch commercialization expenses for the most recent fiscal quarter, are included as a reduction of Sanofi collaboration revenue. The Sanofi estimate for the most recent fiscal quarter is adjusted in the subsequent quarter to reflect actual expenses for the quarter.

During the first quarter of 2011 the Company adopted amended authoritative guidance issued by the FASB on multiple-deliverable revenue arrangements. The amended guidance provides greater ability to separate and allocate consideration to be received in a multiple-deliverable revenue arrangement by requiring the use of estimated selling prices to allocate the consideration, thereby eliminating the use of the residual method of allocation. The amended guidance also requires expanded qualitative and quantitative disclosures surrounding multiple-deliverable revenue arrangements. The Company is applying this amended guidance prospectively for new or materially modified arrangements, of which there were none during the year ended December 31, 2011; therefore, the adoption of this guidance did not have an impact on the Company’s financial statements.

During the first quarter of 2011, the Company adopted amended authoritative guidance issued by the FASB codifying the milestone method of revenue recognition as an acceptable revenue recognition model when a milestone is deemed to be substantive. The Company earns substantive performance milestone payments in connection with its collaboration agreements to develop and commercialize product candidates with Sanofi and Bayer HealthCare. Descriptions of these collaboration agreements, including various financial terms and conditions, are provided in Note 3. Since the Company has historically accounted for milestones under the milestone method, the adoption of this guidance did not have a material impact on the Company’s financial statements.

In December 2010, the FASB provided authoritative guidance on how pharmaceutical manufacturers should recognize and classify in their income statement annual fees mandated by the Patient Protection and Affordable Care Act as amended by the Health Care and Education Reconciliation Act. This guidance became effective for calendar years beginning after December 31, 2010. The adoption of this guidance did not have an impact on the Company’s financial statements for the year ended December 31, 2011, since (i) ARCALYST® for the treatment of CAPS, has been approved as an orphan drug and orphan drugs are not subject to this annual fee and (ii) since EYLEAÒ received regulatory approval from the FDA, and was launched, in November 2011.

In June 2011, the FASB amended its authoritative guidance on the presentation of comprehensive income. Under the amendment, an entity will have the option to present the total of comprehensive income, the components of net income, and the components of other comprehensive income either in a single continuous statement of comprehensive income or in two separate but consecutive statements. This amendment, therefore, eliminates the currently available option to present the components of other comprehensive income as part of the statement of changes in stockholders' equity. The amendment does not change the items that must be reported in other comprehensive income or when an item of other comprehensive income must be reclassified to net income. The Company will adopt this amended guidance for the fiscal year beginning January 1, 2012. As this guidance relates to presentation only, the adoption of this guidance will not have any other effect on the Company's financial statements.