Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Operating expenses:
Research and development	$ 28,184	$ 19,951	$ 83,101	$ 49,794
In-process research and development		1,680	2,000	10,848
General and administrative	8,778	6,916	24,271	15,696
Contribution of common stock to Erasca Foundation		17,497		17,497
Total operating expenses	36,962	46,044	109,372	93,835
Loss from operations	(36,962)	(46,044)	(109,372)	(93,835)
Other income (expense)
Interest income	1,522	49	2,024	110
Other expense	(49)	(74)	(207)	(190)
Change in fair value of preferred stock purchase right liability				1,615
Total other income (expense), net	1,473	(25)	1,817	1,535
Net loss	$ (35,489)	$ (46,069)	$ (107,555)	$ (92,300)
Net loss per share, basic	$ (0.29)	$ (0.46)	$ (0.90)	$ (1.90)
Net loss per share, diluted	$ (0.29)	$ (0.46)	$ (0.90)	$ (1.90)
Weighted-average shares of common stock used in computing net loss per share, basic	120,798,322	99,127,286	120,166,023	48,584,029
Weighted-average shares of common stock used in computing net loss per share, diluted	120,798,322	99,127,286	120,166,023	48,584,029
Other comprehensive income (loss):
Unrealized (loss) gain on marketable securities, net	$ (156)	$ 1	$ (1,217)	$ (2)
Comprehensive loss	$ (35,645)	$ (46,068)	$ (108,772)	$ (92,302)