Erasca, Inc.

Rule 10b5-1 Trading Plans

During the three months ended June 30, 2025, none of our officers (as defined in Rule 16a–1(f)) or directors adopted, materially modified orterminated any Rule 10b5-1 trading arrangement or non-Rule 10b5-1 trading arrangement, as each such term is defined in Item 408 of Regulation S-K.

At the Market Sales Agreements

2022 Sale Agreement

On August 11, 2022, we entered into an Open Market Sale Agreement (the Sale Agreement), with Jefferies LLC (the Agent), pursuant to which we could offer and sell shares of our common stock having an aggregate offering price of up to $200 million from time to time, in an “at-the-market offering” (2022 ATM Offering) through the Agent. In connection with the 2022 ATM Offering, we filed a sales agreement prospectus (the 2022 ATM Prospectus) with a shelf registration statement on Form S-3 (File No. 333-266802), which was declared effective by the SEC on August 18, 2022. In connection with the Amended and Restated Sale Agreement (defined below), effective August 12, 2025, we amended and restated the Sale Agreement, and we have discontinued all offers and sales of shares of our common stock under the Sale Agreement and the 2022 ATM Prospectus. As of June 30, 2025, we had $178.1 million of shares available for sale under the 2022 ATM Offering.

Amended and Restated Sale Agreement

On August 12, 2025, we entered into an Amended and Restated Open Market Sale Agreement (the Amended and Restated Sale Agreement) with the Agent, pursuant to which we may offer and sell shares of our common stock having an aggregate offering price of up to $200 million from time to time, in an “at-the-market offering” (2025 ATM Offering) through the Agent. Sales of the shares of common stock, if any, will be made at prevailing market prices at the time of sale, or as otherwise agreed with the Agent. The Agent will receive a commission from us of up to 3.0% of the gross proceeds of any shares of common stock sold under the Amended and Restated Sale Agreement.

We are not obligated to sell, and the Agent is not obligated to buy or sell, any shares of common stock under the Amended and Restated Sale Agreement. No assurance can be given that we will sell any shares of common stock under the Amended and Restated Sale Agreement, or, if we do, as to the price or amount of shares of common stock that we sell or the dates when such sales will take place.

In the Amended and Restated Sale Agreement, we agreed to indemnify the Agent against certain liabilities, including under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended, or to contribute to payments that the Agent may be required to make because of such liabilities. We and the Agent may each terminate the Amended and Restated Sale Agreement at any time upon specified prior written notice.

The foregoing description of the Amended and Restated Sale Agreement is not complete and is qualified in its entirety by reference to the Amended and Restated Sale Agreement, a copy of which will be filed as Exhibit 1.2 to our Registration Statement on Form S-3 to be filed on August 12, 2025 with the SEC and is incorporated herein by reference.