Results of Operations and Financial Condition. On August 3, 2026, Design Therapeutics, Inc. issued a press release announcing its financial results for the three and six months ended June 30, 2026. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto, are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subj…

Other Events. On May 18, 2026, Design Therapeutics, Inc. (the “Company”) announced biomarker and clinical data from the ongoing Phase 1/2 RESTORE-FA trial evaluating DT-216P2 in patients with Friedreich ataxia (“FA”). RESTORE-FA Key Data Highlights RESTORE-FA is a Phase 1/2 clinical trial evaluating DT-216P2 in patients with FA, designed to assess safety, pharmacokinetics, pharmacodynamics, and exploratory clinical endpoints. As of May 17, 2026, 16 patients had completed treatment with weekly…

Results of Operations and Financial Condition. On April 28, 2026, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three months ended March 31, 2026. A copy of the press release is attached hereto as Exhibit 99.1.

Class III director — David Shapiro, M.D.: Dr. David Shapiro was appointed as a Class III director and to the Nominating Committee.

Results of Operations and Financial Condition. On March 9, 2026, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three and twelve months ended December 31, 2025. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act…

Director — Deepa Prasad: Resigned due to required conflict-avoidance policies associated with her newly appointed role with a major bank.

Results of Operations and Financial Condition. On November 5, 2025, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three and nine months ended September 30, 2025. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange A…

Director — Arsani William, M.D.: Dr. Arsani William resigned from the board of directors.

Results of Operations and Financial Condition. On August 7, 2025, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three and six months ended June 30, 2025. A copy of the press release is attached hereto as Exhibit 99.1.

Results of Operations and Financial Condition. On May 7, 2025, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three months ended March 31, 2025. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise…

Results of Operations and Financial Condition. On March 10, 2025, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three and twelve months ended December 31, 2024. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Ac…

Results of Operations and Financial Condition. On November 7, 2024, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three and nine months ended September 30, 2024. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange A…

Results of Operations and Financial Condition. On August 5, 2024, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three and six months ended June 30, 2024. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or…

Results of Operations and Financial Condition. On May 8, 2024, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three months ended March 31, 2024. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise…

Results of Operations and Financial Condition. On March 19, 2024, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three and twelve months ended December 31, 2023. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Ac…

Results of Operations and Financial Condition. On November 13, 2023, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three and nine months ended September 30, 2023. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange…

President, Chief Executive Officer and principal financial officer — João Siffert, M.D.: Dr. João Siffert resigned from all offices and the Board was immediately succeeded by Pratik Shah, Ph.D.

Results of Operations and Financial Condition. On August 14, 2023, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three and six months ended June 30, 2023. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), o…

Results of Operations and Financial Condition. On May 9, 2023, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three months ended March 31, 2023. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise…

Results of Operations and Financial Condition. On March 14, 2023, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three and twelve months ended December 31, 2022. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Ac…

Results of Operations and Financial Condition. On November 3, 2022, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three and nine months ended September 30, 2022. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange A…

Results of Operations and Financial Condition. On August 8, 2022, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three and six months ended June 30, 2022. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or…

Results of Operations and Financial Condition. On May 9, 2022, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three months ended March 31, 2022. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise…

Entry into a Material Definitive Agreement. On March 18, 2022, Design Therapeutics, Inc. (the “Company”) entered into a First Amendment (the “Lease Amendment”) to its Lease, dated February 2, 2021 (the “Lease Agreement”) with Crossing Holdings, LLC. Pratik Shah, Ph.D., Executive Chair, co-founder and a member of the Company’s Board of Directors, is the sole member and Manager of Crossing Holdings, LLC. Under the Lease Agreement, the Company currently leases approximately 12,370 square feet of…

Results of Operations and Financial Condition. On March 10, 2022, Design Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the three and twelve months ended December 31, 2021. A copy of the press release is attached hereto as Exhibit 99.1. The information in this Item and the exhibit attached hereto are being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Ac…