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The hype around FGFR3 inhibitors, specifically Erdafitinib and Dabogratinib (TYRA-300), has been going on for a long time. This thread isn't going to be about side effects or any of that bullshit. This is strictly about one thing: which one is actually better for linear bone growth.
1. Erdafitinib
Erda is a pan-FGFR inhibitor, meaning it blocks all four FGFR receptors at once: FGFR1, FGFR2, FGFR3, and FGFR4. In the epiphyseal plate, FGFR3 plays the main "brake" role. When it's active, chondrocytes stop dividing and begin to age, eventually leading to apoptosis (cell death). By removing this brake, chondrocytes continue to divide, which keeps linear growth going and prevents them from entering the hypertrophic stage too early—they stay in the proliferative stage instead.
As I said earlier, Erda hits all FGFRs at once, and these receptors are crucial for the normal function of connective tissue, joints, and the vascular system. Because of this, disruptions can occur in certain processes that affect normal bone formation.
There are also many clinical cases where teenagers taking Erda experienced rapid growth acceleration, up to 19 cm/year. For reference, the normal rate for a 15-year-old is 6–9 cm/year—meaning on Erda, you grow 2–3 times faster than normal.
Currently, there are no clinical trials where Erda has been used to treat achondroplasia.
2. Dabogratinib (TYRA-300)
Dabogratinib is a selective FGFR3 inhibitor. It was specifically designed to solve Erda's main problem—the off-target hit on FGFR1/2. The mechanism of action is the same as Erda's.
Dabogratinib is 63 times more selective for FGFR3 than for FGFR1. This means there is no "dosage ceiling." This is also confirmed by the ongoing pediatric trial for achondroplasia, where the dose has already been escalated 8 times.
What did it show in mice?
Dabogratinib was given to mice with achondroplasia. The results:
· Body length: +17.9%
· Femur length: +22.6%
· Tibia length: +33.0%
The shape of the foramen magnum and intervertebral discs also improved in the mice. This is crucial for the skull because, in achondroplasia, cranial sutures close too early
The effect is also dose-dependent. The higher the dose, the greater the growth
The results of the pediatric achondroplasia study are expected to be released at the end of this year or in early '27
3.
Why I lean more towards Dabogratinib
(IMHO)
If we drop the theory and look at the scientific data, Dabogratinib has already shown incredible results in humans—not in the context of growth yet, but in cancer treatment, where FGFR3 is also involved. If the drug is capable of stopping a cancer that depends on the same FGFR3 receptor, it will most likely also work on chondrocytes in the epiphyseal plate, removing the brake on bone growth.
Conclusion
Selectivity is more important than raw power. Choose Erda if you're ready for the side effects. As for the price, I think once the Dabogratinib trials are finished, the price will drop significantly. So you can wait—but the choice is yours.
@Hypertrophy
1. Erdafitinib
Erda is a pan-FGFR inhibitor, meaning it blocks all four FGFR receptors at once: FGFR1, FGFR2, FGFR3, and FGFR4. In the epiphyseal plate, FGFR3 plays the main "brake" role. When it's active, chondrocytes stop dividing and begin to age, eventually leading to apoptosis (cell death). By removing this brake, chondrocytes continue to divide, which keeps linear growth going and prevents them from entering the hypertrophic stage too early—they stay in the proliferative stage instead.
As I said earlier, Erda hits all FGFRs at once, and these receptors are crucial for the normal function of connective tissue, joints, and the vascular system. Because of this, disruptions can occur in certain processes that affect normal bone formation.
There are also many clinical cases where teenagers taking Erda experienced rapid growth acceleration, up to 19 cm/year. For reference, the normal rate for a 15-year-old is 6–9 cm/year—meaning on Erda, you grow 2–3 times faster than normal.
Currently, there are no clinical trials where Erda has been used to treat achondroplasia.
2. Dabogratinib (TYRA-300)
Dabogratinib is a selective FGFR3 inhibitor. It was specifically designed to solve Erda's main problem—the off-target hit on FGFR1/2. The mechanism of action is the same as Erda's.
Dabogratinib is 63 times more selective for FGFR3 than for FGFR1. This means there is no "dosage ceiling." This is also confirmed by the ongoing pediatric trial for achondroplasia, where the dose has already been escalated 8 times.
What did it show in mice?
Dabogratinib was given to mice with achondroplasia. The results:
· Body length: +17.9%
· Femur length: +22.6%
· Tibia length: +33.0%
The shape of the foramen magnum and intervertebral discs also improved in the mice. This is crucial for the skull because, in achondroplasia, cranial sutures close too early
The effect is also dose-dependent. The higher the dose, the greater the growth
The results of the pediatric achondroplasia study are expected to be released at the end of this year or in early '27
3.
Why I lean more towards Dabogratinib
(IMHO)
If we drop the theory and look at the scientific data, Dabogratinib has already shown incredible results in humans—not in the context of growth yet, but in cancer treatment, where FGFR3 is also involved. If the drug is capable of stopping a cancer that depends on the same FGFR3 receptor, it will most likely also work on chondrocytes in the epiphyseal plate, removing the brake on bone growth.
Conclusion
Selectivity is more important than raw power. Choose Erda if you're ready for the side effects. As for the price, I think once the Dabogratinib trials are finished, the price will drop significantly. So you can wait—but the choice is yours.
Tyra Biosciences Announces First Child Dosed in BEACH301, its Phase 2 Study for Dabogratinib (TYRA-300) in Pediatric Achondroplasia
-Dabogratinib is the only oral FGFR3-selective inhibitor in clinical development for achondroplasia- -Initial results from safety sentinel cohort expected in 2H 2026- CARLSBAD, Calif., Aug. 21, 2025 /
tyrabio.investorroom.com
@Hypertrophy
