Achondroplasia is the most common genetic form of short-limbed skeletal dysplasia, affecting an estimated 4.6 per 100,000 births worldwide. The condition arises from a gain-of-function mutation in FGFR3 (fibroblast growth factor receptor 3), which disrupts endochondral ossification and leads to characteristic short stature and limb proportions. Beyond stature, individuals with achondroplasia may face complications across the lifespan, including foramen magnum stenosis, spinal canal narrowing, sleep-disordered breathing, and challenges with activities of daily living, all of which can impact quality of life and necessitate multidisciplinary care.
Historically, clinical care has focused on symptomatic management, with limited pharmacological options. Interventions to increase height were restricted to growth hormone therapy or surgical limb lengthening, the latter carrying a high risk of complications. The approval of vosoritide in 2021 marked the first pharmacological therapy for achondroplasia, targeting the underlying FGFR3 pathway. Vosoritide is a once-daily injection that inhibits the downstream pathways that FGFR3 uses to restrict bone growth.
Although Vosoritide represents a landmark advance, it still has important limitations, including annual height increases, selectivity, and delivery. A few companies are now developing more precise oral therapies for achondroplasia that go a step further. One of these is Tyra Biosciences, which is developing dabogratinib (TYRA-300), a potential first-in-class, oral, FGFR3-selective inhibitor.
Toward next-generation precision therapies
“What vosoritide demonstrated for the first time was an enduring increase in annualized growth velocity,” Todd Harris, CEO and cofounder of Tyra Biosciences, told DDN. “That was an important distinction from growth hormone, which had been used for years but typically produced only a transient spike in growth that faded over time, ultimately accelerating children toward their final adult height without meaningfully changing it.”
That said, height alone is not the primary concern for most individuals with achondroplasia. What matters far more to the community is whether treatment can meaningfully affect the broader clinical implications of the condition. Improvements in proportionality, for example, could translate into tangible benefits in daily life, from reach and mobility to endurance, gait, and the ability to navigate physical environments. There is also significant interest in whether earlier intervention could reduce the need for surgical procedures related to ear canal narrowing, spinal stenosis, or foramen magnum stenosis — areas where growth plate abnormalities play a central role.
To date, however, vosoritide has not demonstrated clear benefit across this full range of complications, particularly in randomized studies. This has led to growing interest in whether earlier treatment, greater efficacy, or alternative therapeutic approaches could more comprehensively address the underlying disease and its long-term consequences.
A more effective and selective approach
Both Tyra Biosciences and BridgeBio are developing oral therapies for achondroplasia. BridgeBio’s candidate, infigratinib, is a pan-FGFR inhibitor originally developed for oncology but repurposed at carefully calibrated lower doses to target FGFR3 effectively while minimizing off-target toxicities.
BridgeBio recently reported positive topline Phase 3 results for infigratinib, showing best-in-class growth improvements and the first statistically significant improvement in body proportionality in a randomized trial for the condition. Importantly, it also represents what could become the first oral treatment option for children with achondroplasia — a potential inflection point for long-term adherence and quality of life. The latest results suggest that, after one year, children taking infigratinib grew faster than those on placebo, gaining approximately 1.7-2.1cm more per year.
However, Harris believes that there is still meaningful headroom to further improve growth outcomes and, potentially, their downstream clinical impact. “The usual benchmark for annualized height velocity improvement over placebo is around 1.7cm across current agents,” Harris explained. But the average adult height difference between individuals with and without achondroplasia is approximately 46 cm. Considering the roughly 17 years during which growth plates remain active, this translates to a target annual growth increase of about 2.7 cm per year. “That extra centimeter per year is what would really indicate a more normalized growth pattern and could potentially improve downstream clinical outcomes as well.”
Tyra Biosciences believes achieving that extra growth likely requires an FGFR3-selective approach, allowing for higher dosing and deeper target engagement. While infigratinib has demonstrated meaningful growth and proportionality benefits, its pan-FGFR activity inherently limits the maximum tolerable dose. Because the drug also inhibits FGFR1 and FGFR2, increasing exposure to fully engage FGFR3 can lead to off-target toxicities such as hyperphosphatemia, diarrhea, and eye and nail toxicity.
“In our own work, we’ve shown that our molecule, dabagratinib, can potently inhibit FGFR3 while largely sparing FGFR1 and FGFR2,” said Harris. “That selectivity has allowed us to design dosing regimens in our current study that aim to engage the target more fully and, we believe, potentially deliver the greater efficacy the achondroplasia community is seeking.”
Finding the right dose
Determining the optimal dose is critical in achondroplasia, particularly because FGFR3 plays a central role in regulating growth plate activity. Too little inhibition may not produce meaningful height gains, while too much could accelerate bone growth excessively, increasing the risk of fractures and skeletal complications.
“We know from preclinical studies that fully inhibiting FGFR3 while growth plates are open can cause bones to grow too fast, which can lead to fractures,” Harris explained. “The key is getting the dose precisely right to maximize benefit while avoiding adverse effects.”
Dabogratinib has also been clinically validated in a Phase 1 setting outside of achondroplasia, where it showed dose‑dependent inhibition of FGFR3 signaling and preliminary anti‑tumor activity in patients with advanced cancers driven by FGFR3 alterations.
“Our Phase 1 data showed we could effectively inhibit FGFR3, even causing significant tumor shrinkage in many patients. That gives us confidence that the drug hits the target,” said Harris. “Now it’s about finding the right dose for children, which we’re doing using robust translational models that guide us toward the doses most likely to work, with adjustments along the way.”
Tyra’s BEACH301 Phase 2 trial is currently exploring multiple dose levels of dabogratinib in children aged three to ten years. “We’re testing four different doses in children, monitoring their annualized height velocity, and selecting the dose that best meets our growth targets. This work will continue over the next year, after which we plan to move quickly into Phase 3 at the selected dose,” said Harris.
Promising future for achondroplasia
As research in achondroplasia progresses, the field is moving beyond simply addressing short stature toward a more holistic approach aimed at improving proportionality, mobility, and long-term quality of life. Vosoritide demonstrated for the first time that pharmacological intervention could provide sustained increases in annualized growth velocity, offering a meaningful proof of concept. However, limitations in efficacy, delivery, and broader clinical impact highlight the need for next-generation therapies.
Oral FGFR3-targeted therapies, such as dabogratinib, represent a promising step forward, offering the potential for greater target engagement, improved proportionality, and more convenient administration. Early clinical data suggest that this approach can safely accelerate growth and enhance body proportions, bringing the field closer to therapies that address the full spectrum of challenges faced by individuals with achondroplasia.
