Efficacy and Safety of Oral Meclizine for Growth Promotion in Children with Achondroplasia: A Phase 2 Clinical Trial.

Meclizine has been shown to promote bone growth by inhibiting a key signaling pathway involved in achondroplasia (ACH). Earlier studies demonstrated its safety in children with ACH after short-term use. The purpose of this study is to assess the safety and efficacy of meclizine treatment over 26 weeks in children with ACH. This open-label, single-arm, Phase 2 study was conducted at four sites in Japan. Nine children with ACH, aged 5-10 years old, received daily meclizine (12.5 mg/day for those < 20 kg; 25 mg/day for those ≥ 20 kg). This was co-administered with growth hormone therapy for 26 weeks. Safety was monitored through adverse events (AEs), while treatment efficacy was measured by changes in height velocity (cm/year). Secondary measures included the proportion of children achieving a height velocity of ≥ 6 cm/year and changes in arm span growth. Arm span velocity and the proportion of participants reaching ≥ 6 cm/year were evaluated through ad hoc analyses. No serious AEs were reported. Height velocity increased slightly from 4.35 ± 1.36 cm/year pre-treatment to 4.46 ± 1.54 cm/year post-treatment. One participant achieved a height velocity of ≥ 6 cm/year. Mean height increased from 107.48 ± 9.04 to 109.77 ± 8.69 cm over the study period. By contrast, arm span velocity was higher at 6.93 ± 2.50 cm/year, with six children reaching ≥ 6 cm/year. An additive effect of meclizine and growth hormone on promoting height was not observed; however, meclizine may enhance arm span growth in children with ACH.Trial registration number jRCT2041230001.