<img src="https://ml-eu.globenewswire.com/Resource/Download/bb724119-468d-4b1d-8206-3c2175d07f2b?size=2" nborder="0" align="left" hspace="5" vspace="5" title="logo.png" alt="Idorsia Pharmaceuticals Ltd"/>Ad hoc announcement pursuant to Art. 53 LR <ul type="disc"><li>The DEA states that dual orexin receptor antagonists “do not produce physical or psychological dependence”</li><li>Lower schedule expected to enhance patient access in the US</li></ul> Allschwil, Switzerland – August 11, 2026 Idorsia Ltd (SIX: IDIA) announces that the US Drug Enforcement Administration (DEA) will publish a proposed rule to reclassify dual orexin receptor antagonists (DORAs) from Schedule IV to Schedule V under the Controlled Substances Act (CSA). The proposal will be open to public comment for a duration of 30 days from publication – expected later today. The DEA’s proposed rule follows a scientific and medical evaluation and scheduling recommendation from HHS, considering the statutory eight factors, which the DEA then reviewed in its own eight-factor analysis. Jean-Paul Clozel, MD, Chairman and interim CEO of Idorsia, commented: “We view the recommendation to reclassify to the least restrictive schedule V as an important first step. The proposed reclassification recognizes the favorable profile of daridorexant compared with traditional sedative-hypnotics. While we believe that the available evidence supports full descheduling, we will now analyze the proposal in detail and provide comments through the appropriate forum. We hope the continued removal of restrictions paves the way for more patients to benefit from the DORA class.”  Next steps The DEA will accept public comments on the proposed rule before issuing a final decision. About QUVIVIQ® (daridorexant) in the United States QUVIVIQ is approved in the United States for the treatment of adult patients with chronic insomnia characterized by difficulties with sleep onset and/or sleep maintenance. Notes to the editor About Idorsia The purpose of Idorsia is to discover, develop and commercialize innovative medicines to help more patients. To achieve this, we will develop Idorsia into a leading biopharmaceutical company, with a strong scientific core. Headquartered near Basel, Switzerland – a European biotech hub – Idorsia has a highly experienced team of dedicated professionals, covering all disciplines from bench to bedside; QUVIVIQ™ (daridorexant), a different kind of insomnia treatment with the potential to revolutionize this mounting public health concern; strong partners to maximize the value of our portfolio; a promising in-house development pipeline; and a specialized drug discovery engine focused on small-molecule drugs that can change the treatment paradigm for many patients. Idorsia is listed on the SIX Swiss Exchange (ticker symbol: IDIA). For further information, please contact: Investor &amp; Media Relations Idorsia Pharmaceuticals Ltd, Hegenheimermattweg 91, CH-4123 Allschwil +41 58 844 10 10 investor.relations@idorsia.com – media.relations@idorsia.com – www.idorsia.com The above information contains certain "forward-looking statements", relating to the company's business, which can be identified by the use of forward-looking terminology such as “intend”, "estimates", "believes", "expects", "may", "are expected to", "will", "will continue", "should", "would be", "seeks", "pending" or "anticipates" or similar expressions, or by discussions of strategy, plans or intentions. Such statements include descriptions of the company's investment and research and development programs, business development activities and anticipated expenditures in connection therewith, descriptions of new products expected to be introduced by the company and anticipated customer demand for such products and products in the company's existing portfolio. Such statements reflect the current views of the company with respect to future events and are subject to certain risks, uncertainties and assumptions. Many factors could cause the actual results, performance or achievements of the company to be materially different from any future results, performances or achievements that may be expressed or implied by such forward-looking statements. Should one or more of these risks or uncertainties materialize, or should underlying assumptions prove incorrect, actual results may vary materially from those described herein as anticipated, believed, estimated or expected. 
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Idorsia acknowledges the DEA proposal to reclassify dual orexin receptor antagonists to the lowest schedule – Schedule V

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