A Study to Learn About Recifercept in Patients With Achondroplasia

The purpose of this study is to learn about the study medicine (called recifercept) in people with achondroplasia. Achondroplasia is a very rare disease and patients of achondroplasia have short arms and legs. The study will include data already collected from a recifercept clinical trial and data collected from a separate study of achondroplasia. This study will compare patient experiences and will help the investigators determine if the study medicine, recifercept, is effective.

Inclusion Criteria:All patients from Study C4181005 who have completed Visits 1 through 11 (at D183) will be included in this project.To construct a concurrent external control, patients from Study C4181001 will need to meet the following inclusion criteria from Study C4181005 to be eligible for inclusion:Documented, confirmed genetic diagnosis of achondroplasia from historical medical records (test must have been performed at a laboratory fully accredited for genetic testing under local regulations)Aged ≥ 3 months to <11 years (up to the day before 11th birthday inclusive) at time of enrollment into the observational natural history study.Havecompleted at least 2 valid height/length measurements (at least 3 months apart)Assessed for Tanner stage 1 during physical examination before or at enrollment (must include assessment of breast development for females, testicular stage for males)Able to stand independently for height measurements (if ≥ 2 years of age at enrollment); If aged <2 years at enrollment, has a documented historical MRI brain/cervical spine performed in the previous 12 months.Have at least 6 months of available follow-up data after enrollment into the natural history studyExclusion Criteria:Patients meeting any of the following criteria will not be included in the study:Presence of severe obesity (BMI>95% percentile on Hoover-Fong BMI charts);Body weight <7kg or >30kgHistory of chronic kidney disease (CKD) or renal impairmentHistory of receipt of any treatment that are known to potentially affect growth (including oral steroids > 5 days in the last 6 months before enrollment, high dose inhaled corticosteroids (>800 mcg/day beclametasone equivalent) and medication for attention deficient hyperactivity disorder.Less than 6 months since fracture or surgical procedure of any bone determined from the baseline visit date.Presence of any internal guided growth plates/devicesHistory of removal of internal guided growth plates/devices within 6 months prior to enrollment