PROPEL 3 Trial: Oral Drug Infigratinib Shown to Increase Height Velocity in Children with Achondroplasia

A phase 3 randomised trial presented at a major international conference has found that once-daily oral infigratinib markedly increased height growth rates in children with achondroplasia compared with placebo over one year.

What the Trial Found

Results from the PROPEL 3 trial, presented at the International Conference on Children’s Bone Health 2026 (#ICCBH2026), show that a once-daily oral dose of infigratinib produced a statistically significant increase in annualised height velocity in children aged 3 to 17 years living with achondroplasia. The findings were published in the New England Journal of Medicine.

The trial was structured as a phase 3, randomised, placebo-controlled study — the gold standard design in clinical research, meaning participants were randomly assigned to receive either the active drug or an inactive placebo, with neither group knowing which they had received. This design is used to minimise bias and isolate the effect of the treatment itself.

Understanding Achondroplasia

Achondroplasia is the most common form of short-limb dwarfism. It is a genetic condition affecting bone growth, caused by a mutation in the FGFR3 gene — a gene that, in its altered form, actively inhibits the normal development of cartilage into bone. Children with the condition typically experience disproportionately short stature, with the arms and legs affected more than the trunk.

Infigratinib works by blocking FGFR3 activity. The logic is straightforward: if an overactive FGFR3 is suppressing bone growth, then inhibiting it may allow more normal growth to occur. That’s the mechanism the PROPEL 3 results appear to support, according to the New England Journal of Medicine.

Why an Oral Treatment Matters

Until now, the treatment landscape for achondroplasia has included vosoritide, an injectable therapy administered daily by subcutaneous injection. An oral alternative — a tablet or liquid taken by mouth — could represent a meaningful practical difference for families managing a daily treatment regimen for a child. The PROPEL 3 trial is the first phase 3 evidence base for an oral FGFR3 inhibitor in this age group, according to the published results.

The trial ran over one year. Longer-term safety and efficacy data have not yet been reported from this study.

What Remains Unanswered

The PROPEL 3 results address height velocity — the rate at which children grow — but do not yet confirm whether infigratinib improves final adult height or other clinical outcomes associated with achondroplasia, such as spinal stenosis or limb proportionality. Regulatory submissions to bodies such as the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK have not been announced at this stage, meaning the drug is not currently approved for use on the NHS.

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Key Takeaways

• The PROPEL 3 phase 3 randomised trial found once-daily oral infigratinib much increased annualised height velocity in children aged 3 to 17 with achondroplasia compared with placebo over one year
• Infigratinib is an oral FGFR3 inhibitor — it works by blocking the gene mutation that suppresses normal bone growth in children with achondroplasia
• The drug is not currently approved for NHS use; no MHRA regulatory submission has been publicly announced following the trial presentation

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What This Means for Kent Residents

Families in Kent with a child diagnosed with achondroplasia should be aware that, while these trial results are promising, infigratinib is not yet available through the NHS and has not received regulatory approval from the MHRA. Any questions about current treatment options — including vosoritide, which is available through NHS England’s specialised commissioning pathway — should be directed to your child’s specialist paediatrician or consultant. For general health queries, NHS 111 is available online and by phone; for urgent medical concerns, always call 999 or attend your nearest emergency department. Kent families seeking support and information about achondroplasia can also contact the Restricted Growth Association UK, a charity providing advice and community support to those affected by the condition.