Chugai Pharmaceutical : Notice Regarding Discontinuation of Development of GYM329 (Emugrobart) in Spinal Muscular Atrophy (SMA) and Facioscapulohumeral Muscular Dystrophy (FSHD)

March 23, 2026

Name of listed company: Chugai Pharmaceutical Co., Ltd.

Code number: 4519 (Prime Market of Tokyo Stock Exchange)

Head office: 1-1, Nihonbashi-Muromachi 2-Chome, Chuo-ku,

Tokyo

President & CEO: Osamu Okuda

Inquiries to: Kae Miyata

Head of Corporate Communications Dept. Tel:

For media: +81-(0)3-3273-0881

For investors: +81-(0)3-3273-0554

TOKYO, March 23, 2026 -- Chugai Pharmaceutical Co., Ltd. (TOKYO: 4519) announced that Roche has decided to discontinue the clinical development of GYM329 (emugrobart), an investigational anti-latent myostatin sweeping antibody, for spinal muscular atrophy (SMA) and facioscapulohumeral muscular dystrophy (FSHD).

This decision follows a rigorous assessment of data from the Phase II/III MANATEE study (Part 1) in SMA and the Phase II MANOEUVRE study in FSHD. While emugrobart showed a favorable safety profile and target engagement by reducing mature myostatin, it did not translate into the intended functional outcomes. Specifically, muscle growth and exploratory functional efficacy were neither consistent nor robust enough across study participants to provide sufficient confidence for Phase III development in SMA and FSHD.

Emugrobart was well tolerated across both studies, with no serious adverse events or treatment withdrawals. The discontinuation of these studies was not due to safety concerns.

As the scientific rationale for continuing to investigate emugrobart in obesity remains strong, this decision does not impact the development of emugrobart in obesity. Obesity is a chronic metabolic disease with symptoms and underlying causes being fundamentally different from neuromuscular conditions like SMA and FSHD. In obesity, muscle quality is not primarily affected by a neurodegenerative (nerve-wasting) or myopathic (muscle-wasting) process and there is generally more myostatin for an anti-myostatin antibody to act on. Consequently, the Phase II development of emugrobart in obesity will continue as planned.

This announcement is not expected to have an impact on Chugai's consolidated financial forecast for the fiscal year ending December 2026, which was announced on January 29, 2026.

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