3. Fair Value Measurements

The following table sets forth the fair value of the Company’s financial assets and liabilities measured on a recurring basis by level within the fair value hierarchy:

The following table sets forth the fair value of the Company’s financial assets and liabilities measured on a recurring basis by level within the fair value hierarchy:

Where applicable, the Company uses quoted market prices in active markets for identical assets to determine fair value. This pricing methodology applies to Level 1 investments, which are comprised of money market funds, U.S. government securities and the Vaxcyte common stock shares held by the Company.

If quoted prices in active markets for identical assets are not available, then the Company uses quoted prices for similar assets or inputs other than quoted prices that are observable, either directly or indirectly. These investments are included in Level 2 and consist of commercial paper, corporate debt securities, asset-backed securities and supranational debt securities. These assets are valued using market prices when available, adjusting for accretion of the purchase price to face value at maturity.

A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability.

In certain cases where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3 within the valuation hierarchy. As of September 30, 2021 and December 31, 2020, the Company did not hold any securities that were classified as Level 3 within the valuation hierarchy.

Investments in Equity Securities

Subsequent to the closing of the IPO of Vaxcyte in June 2020, the fair value of Vaxcyte’s common stock became readily determinable. As a result, beginning June 2020, Vaxcyte common stock held by the Company is measured at fair value at each reporting period based on the closing price of Vaxcyte’s common stock on the last trading day of each reporting period, with any unrealized gains and losses recorded in the Company’s statements of operations.

As of September 30, 2021, the Company held 1,567,324 shares of Vaxcyte common stock with an estimated fair value of $39.8 million. Related to Vaxcyte common stock, the Company recognized an unrealized gain of $4.5 million for the three months ended September 30, 2021 and unrealized loss of $1.9 million for the nine months ended September 30, 2021.