Form 8-K BlossomHill Therapeutics For: Sep 15

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): September 15, 2026

BlossomHill Therapeutics, Inc.

(Exact name of registrant as specified in its charter)

10255 Science Center Drive

Suite 200

San Diego, California 92121

(Address of principal executive offices)

Registrant’s telephone number, including area code: (858) 732-3880

N/A

(Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

On September 15, 2026, BlossomHill Therapeutics, Inc. issued a press release announcing updated data from the ongoing Phase 1/2 SOLARA trial of BH-30643 in non-small cell lung cancer (NSCLC) patients with secondary epidermal growth factor receptor (EGFR) resistance mutations such as EGFR C797S. The data were highlighted in a mini-oral presentation at the International Association for the Study of Lung Cancer (IASLC) 2026 World Conference on Lung Cancer in Seoul, South Korea. The full text of the press release issued in connection with this announcement is furnished as Exhibit 99.1 to this Current Report on Form 8-K.

The information in this Item 7.01 and the attached Exhibit 99.1 is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of that Section. The information in this Item 7.01 and the attached Exhibit 99.1 shall not be incorporated by reference into any registration statement or other document pursuant to the Securities Act of 1933, as amended.

(d) Exhibits.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.