Written By: Pharmacally Medical News Desk
Kyowa Kirin has announced the initiation of the Phase 3 AOBA clinical study of KK8398 (infigratinib) in patients with achondroplasia in Japan. This groundbreaking marks a significant step in evaluating an innovative oral treatment aimed at addressing the root cause of this rare genetic disorder. The first patient was dosed on November 20, 2025, starting a pivotal trial designed to evaluate the efficacy and safety of KK8398 over a 52-week treatment and observation period.
The AOBA study (jRCT2031240562), is a multicenter, open-label, single-arm trial planned to enroll approximately six pediatric patients aged 3 to under 18 years. The primary endpoint of this study is the annualized height growth velocity, with secondary outcomes including growth and body proportion parameters, quality of life (QOL) assessments, and safety metrics. This approach reflects Kyowa Kirin’s commitment to improving patient outcomes by providing new therapeutic options tailored specifically to the needs of individuals living with achondroplasia, a designated intractable disease in Japan that causes not only short stature but multiple physical and social challenges throughout life.
KK8398, known generically as infigratinib, is a selective FGFR1-3 oral inhibitor that targets the activating mutations in the FGFR3 gene responsible for achondroplasia. Kyowa Kirin holds exclusive licensing rights in Japan for the development and commercialization of KK8398 for skeletal dysplasias. This Phase 3 trial in Japan aligns with ongoing global efforts led by BridgeBio Pharma, which is concurrently conducting a global Phase 3 study of infigratinib for achondroplasia. The partnership between Kyowa Kirin and BridgeBio exemplifies collaboration to advance treatments for rare bone disorders.
Achondroplasia is characterized by activating FGFR3 mutations in over 97% of cases, resulting in various complications beyond short stature, including spinal canal stenosis, respiratory difficulties, hearing loss, and dental abnormalities. Current treatment options are limited, which underscores the importance of developing effective targeted therapies like KK8398. By inhibiting FGFR3, KK8398 has demonstrated promising results in earlier Phase 2 studies, showing potential to improve height velocity significantly.
Kyowa Kirin’s AOBA study represents a critical step toward making KK8398 available as a new treatment option in Japan. The company anticipates that the data generated will support regulatory submission and eventual commercialization, offering hope to patients with achondroplasia and their families by potentially improving growth outcomes and quality of life.
This development establishes Kyowa Kirin as a key player in bone and mineral disorder therapeutics, while advancing the global clinical development program for KK8398 in skeletal dysplasias, with important implications for Japan’s rare disease community.
References
Kyowa Kirin Announces Initiation of Phase 3 AOBA Study of KK8398 (Infigratinib) in Patients with Achondroplasia in Japan, Kyowa Kirin, 21 November 2025, https://www.kyowakirin.com/media_center/news_releases/2025/pdf/e20251121_01.pdf
BridgeBio Pharma and Kyowa Kirin Announce Partnership with an Upfront Payment of $100 Million for an Exclusive License on Infigratinib in Skeletal Dysplasias in Japan, Bridgebio, 2024, https://bridgebio.com/news/bridgebio-pharma-and-kyowa-kirin-announce-partnership-with-an-upfront-payment-of-100-million-for-an-exclusive-license-on-infigratinib-in-skeletal-dysplasias-in-japan/