• Phase 1 Trial of DT-216 in Patients with Friedreich Ataxia to Be Initiated Soon
• Topline Data from Phase 1 Trial Expected in the Second Half of 2022

Design Therapeutics, Inc. (Nasdaq: DSGN), a biotechnology company developing treatments for degenerative genetic disorders, today announced that its Investigational New Drug Application (IND) for its lead candidate, DT-216, for the treatment of Friedreich ataxia (FA), was cleared by the U.S. Food and Drug Administration (FDA). The company is preparing to initiate a Phase 1 clinical trial of DT-216 to assess the safety, tolerability, pharmacokinetics, and frataxin (FXN) levels in patients with FA. Study enrollment is expected to begin in the coming weeks.

FA is a devastating multisystem degenerative disease caused by a mutation of the GAA repeat expansion of the FXN gene that impairs transcription and reduces gene expression. Low FXN levels result in all FA disease manifestations, including neurological deficits such as loss of balance and coordination, cardiomyopathy and arrhythmias, as well as diabetes and other serious symptoms. DT-216 is a GeneTAC™ gene targeted chimera small molecule designed to specifically target the GAA repeat expansion mutation and restore FXN gene expression.

“The IND clearance for DT-216 is an important milestone for the company, further validating the therapeutic potential of our GeneTAC™ platform, a new class of medicines being developed for serious degenerative diseases caused by a single gene defect. GeneTAC™ molecules, designed based on decades of pioneering research into the mechanisms of gene transcription, are capable of dialing up or dialing down the expression of disease-causing genes and therefore have the potential to address the root cause of genetic diseases,” said João Siffert, M.D., president and chief executive officer of Design Therapeutics. “DT-216 is the first in a pipeline of GeneTAC™ molecules, which can be designed and selected for desirable pharmaceutical properties such as tolerability, broad tissue distribution, including the CNS, efficient manufacturing, and convenient administration. We are eager to begin clinical development of DT-216 for people with FA, for whom there are no disease-modifying treatments available today.”

Design’s IND was supported by a comprehensive package of preclinical data including 2-week multidose studies in rodents, and 2- and 13-week studies in non-human primates (NHPs) demonstrating that systemic administration of DT-216 was well tolerated at dose levels that are projected to achieve concentrations in the CNS, heart and skeletal muscle well in excess of those required to restore FXN gene expression in FA patient derived cells in vitro.

About Design Therapeutics

Design Therapeutics is a biotechnology company developing a new class of therapies based on its platform of GeneTAC™ gene targeted chimera small molecules. The company’s GeneTAC™ molecules are designed to either dial up or dial down the expression of a specific disease-causing gene to address the underlying cause of disease. Design’s lead program is focused on the treatment of Friedreich ataxia, followed by a program in myotonic dystrophy type-1 and discovery efforts for multiple other serious degenerative disorders caused by nucleotide repeat expansions. For more information, please visit designtx.com.

Forward Looking Statements

Statements in this press release 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, statements related to: the expected initiation of Design’s Phase 1 clinical trial for DT-216 in patients with Friedreich ataxia and the timing thereof; the expected timing for beginning enrollment for Design’s Phase 1 clinical trial for DT-216; the expected timing for topline data; the IND clearance for DT-216 being indicative of the therapeutic potential of Design’s GeneTAC^TM platform; and the capabilities and potential advantages of GeneTAC™ molecules. 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," “planned,” "expects," “estimate,” "intends," "will," "goal," "potential" and similar expressions are intended to identify forward-looking statements. These forward-looking statements are based upon Design’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 associated with patient enrollment, which is affected by many factors, and any difficulties or delays encountered with patient enrollment may delay or otherwise adversely affect Design’s planned Phase 1 clinical trial for DT-216; the process of discovering and developing therapies that are safe and effective for use as human therapeutics and operating as a development stage company; Design’s ability to develop, initiate or complete preclinical studies and clinical trials for its product candidates; the risk that promising early research or clinical trials do not demonstrate safety and/or efficacy in later preclinical studies or clinical trials; changes in Design’s plans to develop its product candidates; uncertainties associated with performing clinical trials, regulatory filings and applications; risks associated with reliance on third parties to successfully conduct clinical trials and preclinical studies; Design’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; Design’s reliance on key third parties, including contract manufacturers and contract research organizations; Design’s ability to obtain and maintain intellectual property protection for its product candidates; Design’s ability to recruit and retain key scientific or management personnel; competition in the industry in which Design operates, which may result in others discovering, developing or commercializing competitive products before or more successfully than Design; and market conditions. For a more detailed discussion of these and other factors, please refer to Design’s filings with the Securities and Exchange Commission (“SEC”), including under the “Risk Factors” heading of Design’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2021, as filed with the SEC on November 9, 2021. 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 Design undertakes no obligation to revise or update this press release to reflect events or circumstances after the date hereof, except as required by law.

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