Sosei Heptares Announces Submission of New Drug Application in Japan for Daridorexant (ACT-541468), a Dual Orexin Receptor Antagonist for the Treatment of Insomnia

• NDA includes robust data from a Phase 3 trial that demonstrated efficacy of daridorexant on improving Total Sleep Time and Latency for Sleep Onset, while maintaining a favorable safety profile
• Sosei Heptares to receive JPY 1.5 billion milestone revenue in relation to the submission

Tokyo, Japan and Cambridge, UK, 31 October 2023 – Sosei Group Corporation (“Sosei Heptares” or “the Company”; TSE: 4565) announces that Idorsia Pharmaceuticals Japan Ltd. (“Idorsia Japan”), a Sosei Group company, has submitted a New Drug Application (“NDA”) to the Japanese Pharmaceuticals and Medical Devices Agency (“PMDA”) for the approval of daridorexant (ACT-541468), a dual orexin receptor antagonist which has been co-developed with Mochida Pharmaceutical Co., Ltd. ("Mochida”), for the treatment of adult patients with insomnia.

The NDA is supported by positive results of a randomized, double-blind, placebo-controlled Phase 3 study in Japan to investigate the efficacy and safety of daridorexant. The study met both primary and secondary efficacy endpoints. Daridorexant significantly improved subjective Total Sleep Time (“sTST”), a primary endpoint defined as the change from baseline compared to placebo at 28 days (p<0.001 for 50 mg, p=0.042 for 25 mg). Daridorexant also significantly improved sleep onset as measured by a decrease in subjective Latency for Sleep Onset (“sLSO”), a primary endpoint defined as the change from baseline compared to placebo at 28 days (p<0.001 for 50 mg, p=0.006 for 25 mg). The rate of adverse events was comparable between placebo and daridorexant at both treatment doses. Treatment-emergent adverse events (“TEAEs”) during the double-blind study period were reported in 23.5% and 22.7% of the patients treated with 50 mg and 25 mg daridorexant, respectively (24.4% for placebo).

Sosei Heptares gained Japan and Asia-Pacific (ex-China) rights to daridorexant from Idorsia Pharmaceuticals Ltd (Allschwil, Switzerland) in July 2023 in the context of its acquisition of Idorsia Japan and Idorsia Pharmaceuticals Korea Co., Ltd. Daridorexant was approved in the US and Europe in January and April 2022, respectively, and is marketed by Idorsia in these and other approved territories as QUVIVIQ. In December 2019, Mochida and Idorsia Pharmaceuticals Ltd entered into an exclusive license agreement for the co-development and co-marketing of daridorexant for insomnia and related disorders in Japan. Under the agreement, Mochida and Idorsia Japan have jointly developed daridorexant and plan to co-market daridorexant pending Idorsia Japan receiving Japanese PMDA approval.