The following table summarizes the amortized cost and estimated fair value of the Company's U.S. Treasury securities and U.S. government-sponsored enterprise securities, which are considered to be available-for-sale investments and were included in short-term investments as of March 31, 2024 and December 31, 2023 (in thousands):


	March 31, 2024
Short-term investments:	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasury securities	$	55,353	$	—	$	(25	)	$	55,328
U.S. government-sponsored enterprise securities		30,085		—		(45	)		30,040
	$	85,438	$	—	$	(70	)	$	85,368


	December 31, 2023
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term investments:
U.S. Treasury securities	$	41,470	$	22	$	(19	)	$	41,473
U.S. government-sponsored enterprise securities		50,056		—		(86	)		49,970
	$	91,526	$	22	$	(105	)	$	91,443

Certain short-term debt securities with original maturities of less than 90 days are included in cash and cash equivalents on the condensed consolidated balance sheets and are not included in the tables above. As of March 31, 2024 and December 31, 2023, all short-term investments had contractual maturities within one year.

The aggregate fair value of available-for-sale securities held by the Company in an unrealized loss position for less than 12 months as of March 31, 2024 was $80.4 million. There were no available-for-sale securities in a continuous unrealized loss position for greater than 12 months. The Company evaluated its securities for potential impairment and considered the decline in market value to be primarily attributable to current economic and market conditions. Additionally, the Company does not intend to sell the investments in an unrealized loss position and does not expect it will be required to sell the investments before recovery of their amortized cost bases, which may be maturity. Given the Company's intent and ability to hold such investments until recovery, and the lack of a significant change in credit risk for these investments, the Company does not consider these investments to be impaired and there are no allowances for credit losses as of March 31, 2024.