Chugai Pharmaceutical - Notice Regarding Discontinuation of Development of GYM329 in Spinal Muscular Atrophy and Facioscapulohumeral Muscular Dystrophy

TOKYO - 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.

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.

Contact:

Naoki Kouzai

Tel: +81-3-3273-0881

Email: [email protected]

Takayuki Sakurai

Tel: +81-3-3273-0554

Email: [email protected]

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