RESTORE-FA data push Design Therapeutics (DSGN) to plan registrational path

Rhea-AI Filing Summary

Design Therapeutics reported new biomarker and clinical data from its ongoing Phase 1/2 RESTORE-FA trial of DT-216P2 in Friedreich ataxia. Sixteen patients received weekly intravenous doses from 0.1 to 1 mpk for four weeks.

At the 1 mpk dose, patients showed mean improvements of 6.4 points on the modified Friedreich’s Ataxia Rating Scale and 2.7 points in the Upright Stability Score. Patient-reported fatigue improved by more than five points on the PROMIS Fatigue Scale at four weeks and two weeks after the last dose, exceeding the three-point minimal important change. Whole blood FXN mRNA increased 65%, FXN-M and FXN-E protein rose 22–27%, and muscle FXN mRNA increased 42%, indicating robust frataxin restoration. DT-216P2 was generally well-tolerated, with only mild to moderate adverse events. The company plans to pursue a registrational path and provide an update in the fourth quarter of 2026.

Positive

• Encouraging clinical and biomarker efficacy: At the 1 mpk dose, DT-216P2 produced meaningful improvements in ataxia scores, fatigue, and frataxin biomarkers in both blood and muscle, prompting plans for a registrational path.

Negative

• None.

Insights

Biotech clinical development analyst

Early RESTORE-FA data show promising frataxin and symptom gains with manageable safety.

The RESTORE-FA Phase 1/2 trial tested weekly DT-216P2 infusions in 16 Friedreich ataxia patients across four dose levels for four weeks. At 1 mpk, patients improved by 6.4 points on the modified Friedreich’s Ataxia Rating Scale and 2.7 points on the Upright Stability Score, suggesting meaningful functional benefit.

Biomarker data are strong: whole blood FXN mRNA increased by 65%, FXN-M and FXN-E protein rose 22–27%, and muscle FXN mRNA increased 42%, all after short-term dosing. These concordant blood and muscle effects support DT-216P2’s mechanism in restoring frataxin, a central deficit in Friedreich ataxia.

Safety appears manageable, with no serious adverse events or discontinuations and only mild to moderate events, including transient ALT elevations on background omaveloxolone. The company now intends to pursue a registrational path and plans to update its strategy in Q4 2026. Future data from longer treatment and larger populations will be important to confirm durability and consistency of both clinical and biomarker responses.

8-K Event Classification

Item 8.01 — Other Events

1 item

Item 8.01 Other Events Other

Voluntary disclosure of events the company deems important to shareholders but not covered by other items.

Key Figures

Patients treated: 16 patients Dose cohorts: 0.1, 0.3, 0.6, 1 mpk mFARS improvement: 6.4 points +5 more

8 metrics

Patients treated 16 patients Completed four weeks of weekly intravenous DT-216P2 as of May 17, 2026

Dose cohorts 0.1, 0.3, 0.6, 1 mpk Four weekly intravenous DT-216P2 dose levels, n=4 per cohort

mFARS improvement 6.4 points Mean change from baseline at 1 mpk after four weeks

Upright Stability Score 2.7-point improvement Mean change from baseline at 1 mpk after four weeks

PROMIS Fatigue improvement >5 points Change at four weeks and two weeks post-dose; exceeds 3-point minimal important change

Whole blood FXN mRNA 65% increase Change from baseline after four weeks of 1 mpk DT-216P2, p < 0.001

FXN protein in blood 22–27% increase FXN-M and FXN-E levels two weeks after last 1 mpk dose, p < 0.001

Muscle FXN mRNA 42% increase Change from baseline after four weeks of 1 mpk DT-216P2, p = 0.015

Key Terms

Phase 1/2 clinical trial, RESTORE-FA, Friedreich ataxia, frataxin, +2 more

6 terms

Phase 1/2 clinical trial medical

"RESTORE-FA is a Phase 1/2 clinical trial evaluating DT-216P2 in patients with FA"

A phase 1/2 clinical trial is an early human study that combines first-in-people safety and dosing checks (phase 1) with an initial look at whether the treatment appears to work (phase 2). Think of it as a short test drive where researchers both confirm the product won’t cause serious harm and gather early signs it could be effective; for investors, successful results reduce risk and can unlock value-creating milestones like larger trials or regulatory discussions.

RESTORE-FA medical

"RESTORE-FA is a Phase 1/2 clinical trial evaluating DT-216P2 in patients with FA"

Friedreich ataxia medical

"Phase 1/2 RESTORE-FA trial evaluating DT-216P2 in patients with Friedreich ataxia"

Friedreich ataxia is a rare inherited neurological disease that progressively damages the nerves that control movement and balance and often affects the heart, leading to muscle weakness, coordination loss, and mobility decline. For investors it matters because the condition creates a focused but high-value market for therapies; successful treatments can attract orphan-drug incentives, premium pricing and meaningful returns, while clinical and regulatory risks are heightened by small patient populations and complex trial endpoints.

frataxin medical

"Dose-dependent increases in endogenous frataxin (“FXN”) were observed following treatment"

Frataxin is a small protein found inside cell powerhouses (mitochondria) that helps manage iron and keep energy-producing machinery working properly; think of it as a maintenance worker that prevents iron from gumming up the engines. Low levels or faulty frataxin cause a progressive neurological and heart disease, so it matters to investors because it is a clear biological target and biomarker for drugs, gene therapies, and diagnostics that could address an unmet medical need and drive commercial value.

PROMIS Fatigue Scale medical

"patient-reported fatigue, as measured by the PROMIS Fatigue Scale, both at the end of four weeks"

A PROMIS Fatigue Scale is a standardized patient questionnaire that measures how tiredness affects a person’s day-to-day functioning and well‑being. Investors should note it because results from this scale are used in clinical trials and regulatory reviews to demonstrate whether a treatment meaningfully reduces fatigue; strong, credible scores can boost a therapy’s approval prospects, labeling claims and market value, much like a reliable customer rating for a product.

registrational path regulatory

"Based on these data, the Company intends to pursue a registrational path and provide an update"

Understanding 8-K Material Events →

false 0001807120 0001807120 2026-05-18 2026-05-18

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) May 18, 2026

Design Therapeutics, Inc.

(Exact name of registrant as specified in its charter)

Delaware		001-40288		82-3929248
(State or other jurisdiction of incorporation)		(Commission File Number)		(IRS Employer Identification No.)

6005 Hidden Valley Road, Suite 110 Carlsbad, California		92011
(Address of principal executive offices)		(Zip Code)

Registrant’s telephone number, including area code: (858) 293-4900

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:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock, $0.0001 par value per share		DSGN		The Nasdaq Global Select Market

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. ☒

Item 8.01 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 intravenous DT-216P2 across dose cohorts of 0.1, 0.3, 0.6, and 1 mpk (n=4 per cohort) for four weeks.

Clinical Outcomes

After four weeks of DT-216P2 treatment at the 1 mpk dose cohort, patients demonstrated mean improvements from baseline of 6.4 points in the modified Friedreich’s Ataxia Rating Scale and 2.7 points in the Upright Stability Score. Further, DT-216P2 demonstrated changes of greater than five points in patient-reported fatigue, as measured by the PROMIS Fatigue Scale, both at the end of four weeks of treatment and two weeks following the last dose. These data exceeded the three-point threshold generally considered to be a minimal important change in fatigue.

Biomarker and Safety Results

Dose-dependent increases in endogenous frataxin (“FXN”) were observed following treatment with DT-216P2 across FXN mRNA and protein assays in whole blood, as well as FXN mRNA measurements in affected muscle tissue, demonstrating activity in both blood and muscle.

Following four weeks of treatment at 1 mpk, whole blood FXN mRNA levels increased by 65% from baseline (p < 0.001). Whole blood FXN-M and FXN-E protein levels increased by 22-27% from baseline two weeks following the last dose (p < 0.001). Muscle FXN mRNA levels increased by 42% from baseline (p = 0.015). Together, these findings demonstrate comprehensive biomarker activity with meaningful increases in FXN mRNA and protein, as well as activity in both blood and muscle caused by DT-216P2 treatment. The biomarker data provide mechanistic support for the observed clinical improvements in FA patients.

DT-216P2 was generally well-tolerated, with no serious adverse events or treatment discontinuations reported. All adverse events were mild or moderate. Adverse events considered possibly or probably related to DT-216P2 occurring in more than one patient included mild to moderate transient alanine transaminase (“ALT”) elevations observed in three patients, all of which were asymptomatic with no associated increases in bilirubin and on background omaveloxolone. Transient ALT elevations are anticipated with enhanced mitochondrial activity, a downstream consequence of FXN restoration.

Next Steps for DT-216P2

Based on these data, the Company intends to pursue a registrational path and provide an update on its plans in the fourth quarter of 2026.

Forward-Looking Statements

Statements in this Current Report on Form 8-K that are not purely historical in nature are “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. These statements include, but are not limited to: the progression of studies and clinical trials for DT216P2; plans to advance DT-216P2 towards registrational development with an update to be provided in the fourth quarter of 2026; and projections and expectations arising from early-stage programs, nonclinical data and interim and early-stage clinical data. Because such statements are subject to risks and uncertainties, actual results may differ materially from those expressed or implied by such forward-looking statements. Words such as “believes,” “designed to,” “anticipates,” “capable of,” “plans to,” “expects,” “estimate,” “intends,” “will,” “potential” and similar expressions are intended to identify forward-looking statements. These forward-looking statements are based upon the Company’s current expectations

and involve assumptions that may never materialize or may prove to be incorrect. Actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of various risks and uncertainties, which include, without limitation, risks and uncertainties associated with: the data we observe from early clinical and nonclinical studies may impact our clinical development plans; pursuing a biomarker-driven clinical development strategy carries increased risks as there are currently a limited number of approved biomarker-specific therapies; nonclinical development activities and results of nonclinical studies; conducting a clinical trial and patient enrollment and retention, which are affected by many factors, and any difficulties or delays encountered with such clinical trial or patient enrollment or retention may delay or otherwise adversely affect the Company’s clinical development plans; the process of discovering and developing therapies that are safe and effective for use as human therapeutics and operating as a development stage company; undesirable side effects or other undesirable properties, which could cause the Company or regulatory authorities to suspend or discontinue clinical trials and thereby delay or prevent the Company’s product candidates’ development or regulatory approval; the Company’s ability to develop, initiate or complete nonclinical studies and clinical trials for its product candidates on the timeframe anticipated, or at all; whether promising early research or clinical trials will result in demonstrated safety and/or efficacy in later clinical trials; changes in the Company’s plans to develop its product candidates; the data results described herein are based on a preliminary analysis of key efficacy and safety data, and such data may change following a more comprehensive review of the data and such data may not accurately reflect the complete results of the trial; reliance on third parties to successfully conduct clinical trials and nonclinical studies; competitive products, which may make any products we develop or seek to develop obsolete or noncompetitive; the Company’s reliance on third parties, including contract manufacturers and contract research organizations; the Company’s ability to raise any additional funding it will need to continue to pursue its business and product development plans; regulatory developments in the United States and foreign countries; the Company’s ability to obtain and maintain intellectual property protection for its product candidates; and the Company’s ability to recruit and retain key scientific or management personnel. For a more detailed discussion of these and other factors, please refer to the Company’s filings with the Securities and Exchange Commission (“SEC”), including under the “Risk Factors” heading of the Company’s Quarterly Report on Form 10-Q for the quarter March 31, 2026, as filed with the SEC on April 28, 2026. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement and the Company undertakes no obligation to revise or update this Current Report on Form 8-K to reflect events or circumstances after the date hereof, except as required by law.

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 thereunto duly authorized.

				DESIGN THERAPEUTICS, INC.
Date: May 18, 2026				By:		/s/ Pratik Shah
						Pratik Shah, Ph.D.
						President, Chief Executive Officer and Chairperson

FAQ

What did Design Therapeutics (DSGN) report from the RESTORE-FA trial?

Design Therapeutics reported new Phase 1/2 RESTORE-FA data for DT-216P2 in Friedreich ataxia. Sixteen patients received weekly intravenous doses for four weeks, showing functional improvements, reduced fatigue and robust frataxin biomarker increases in blood and muscle, with a generally well-tolerated safety profile.

How did DT-216P2 affect Friedreich ataxia clinical scores in DSGN’s trial?

At the 1 mpk dose, DT-216P2 improved the modified Friedreich’s Ataxia Rating Scale by 6.4 points and the Upright Stability Score by 2.7 points over four weeks. These changes suggest potential functional benefits for patients with Friedreich ataxia in this early-stage study.

What biomarker changes were seen with DT-216P2 in Design Therapeutics’ RESTORE-FA study?

DT-216P2 increased whole blood FXN mRNA by 65%, FXN-M and FXN-E protein by 22–27%, and muscle FXN mRNA by 42% after four weeks of treatment. These comprehensive frataxin increases support the drug’s intended mechanism in Friedreich ataxia patients.

How did DT-216P2 impact fatigue in patients with Friedreich ataxia?

Patients experienced greater than five-point improvements on the PROMIS Fatigue Scale after four weeks of DT-216P2 and two weeks post-treatment. This exceeded the three-point minimal important change threshold, indicating potentially meaningful reductions in patient-reported fatigue symptoms.

What safety outcomes were reported for DT-216P2 in DSGN’s RESTORE-FA trial?

DT-216P2 was generally well-tolerated, with no serious adverse events or treatment discontinuations. Reported adverse events were mild or moderate, including transient ALT elevations in three patients on omaveloxolone, without bilirubin increases, consistent with enhanced mitochondrial activity from frataxin restoration.

What are Design Therapeutics’ next steps for DT-216P2 after these Phase 1/2 data?

Based on the RESTORE-FA clinical and biomarker results, Design Therapeutics intends to pursue a registrational development path for DT-216P2. The company plans to provide a further update on its development plans in the fourth quarter of 2026, subject to ongoing evaluation.

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