Notes to Consolidated Financial Statements (continued) The Black-Scholes option valuation model was developed for use in estimating the fair value of traded options that have no vesting restrictions and are fully transferable. In addition, option valuation models require the input of highly subjective assumptions including the expected stock price volatility. Because our employee stock options have characteristics sig- nificantly different from those of traded options, and because changes in the subjective input assumptions can materially affect the fair value estimate, in management’s opinion, the existing models do not necessarily provide a reliable single measure of the fair value of our employee stock options. Based upon the above methodology, the weighted-average fair value of options granted during the years ended December 31, 2001, 2000 and 1999 was $8.44, $23.56 and $4.83, respectively. 13. Related Parties Transactions 14. Income Taxes We make loans to our officers and employees from time to time in order to attract and retain the best available talent and to encourage the highest level of performance. In 2001 and 2000, we provided certain relocation loans to employees  in connection with employment. Also in February 2001, we provided a loan to an officer. The loan, originally due in February 2002, bears an interest rate at prime and has been extended to August 2002. As of December 31, 2001, the  principal amount outstanding on the loan was $373,000. As of December 31, 2001, we had net operating loss carry- forwards for federal income tax purposes of approximately $99.0 million that expire in the years 2006 through 2021, and federal research and development tax credits of approximately $2.2 million that expire in the years 2007 through 2021. We also had net operating loss carryforwards for state income tax purposes of approximately $12.0 million that expire in the years 2002 through 2011. For purposes of SFAS 123 disclosures, the estimated fair value of the options is amortized to expense over the options’ vest- ing period. Our pro forma information is as follows (in thou- sands, except per share amount): Utilization of our net operating loss may be subject to substan- tial annual limitation due to ownership change limitations pro- vided by the Internal Revenue Code and similar state provisions. Such an annual limitation could result in the expira- tion of the net operating loss carryforwards before utilization. Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabil- ities for financial reporting purposes and the amounts used for income tax purposes. Significant components of our deferred tax assets are as follows (in thousands): The consolidated pro forma net loss calculated above also includes the estimated fair value of the options granted by  our subsidiaries in 2001, 2000 and 1999, calculated on sub- stantially equivalent assumptions. The $1.2 million received by Ingenex upon the issuance of its Series B convertible preferred stock has been classified as minority interest in the consolidated balance sheet. As a result of the Series B preferred stockholders’ liquidation preference, the balance has not been reduced by any portion of the losses of Ingenex. Amounts invested by outside investors in the common stock of the consolidated subsidiaries have been apportioned between minority interest and additional paid-in capital in the consolidated balance sheets. Losses applicable to the minority interest holdings of the subsidiaries’ common stock have been reduced to zero. 12. Minority Interest December 31, 2001 2000 Deferred tax assets: Net operating loss carryforwards $ 34,300 $ 28,200 Research credit carryforwards 3,000 2,000 Capitalized research and development 3,400 2,900 Other, net 900 2,000 Total deferred tax assets 41,600 35,100 Deferred tax liabilities: Unrealized gain on investments (800) (200) Valuation allowance (40,800) (34,900) Net deferred tax assets $ — $ — December 31, 2001 2000 1999 Net loss as reported $(17,464) $(18,788) $(11,296) Basic and diluted net loss  per share as reported $ (0.63) $ (0.73) $ (0.70) Pro forma net loss $(27,690) $(27,569) $(13,487) Pro forma basic and diluted  net loss per share $ (1.00) $ (1.08) $ (0.84) Twenty-Eight