A Study of TYRA-300 in Children With Achondroplasia: BEACH301

Inclusion Criteria:

* Aged 3 to 10 years old (inclusive) at the time of consent.
* Informed consent provided by parent(s) or legal guardian(s). As study participants are less than 18 years old, participants are willing and able to provide written assent (where applicable and required).
* Molecular diagnosis of achondroplasia (FGFR3 G380R).
* Radiographically confirmed open growth plates at Screening, as determined by bone age X-ray.
* Able to stand and ambulate independently.
* Able to take oral medication.
* Sentinel Safety Cohort only: aged 5 to 10 years old (inclusive).
* Cohort 1 only: aged 3 to 10 years old (inclusive) and are naive to prior growth accelerating therapy.
* Cohort 2 only: aged 3 to 10 years old (inclusive) and have received prior growth accelerating therapy.

Exclusion Criteria:

* Presence or history of any concurrent disease or condition that would interfere with study participation, safety evaluations, or any uncontrolled or untreated condition that could impact pediatric growth.
* Diagnosis of endocrine condition that alters calcium/phosphate homeostasis.
* Prior limb lengthening surgery or planned or expected to have limb lengthening surgery while enrolled in the study.
* Taking medications that are strong inhibitors or inducers of cytochrome P450 (Cyp) 3A4.
* History or current evidence of corneal or retinal disorder/keratopathy.
* Presence of guided growth hardware/8 plates. Planned or anticipated orthopedic surgeries.