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Enrolling by Invitation

NCT Number: NCT05929807

A Clinical Trial to Investigate Long-term Safety, Tolerability, and Efficacy of Weekly Subcutaneous Doses With TransCon CNP in Children and Adolescents With Achondroplasia

TransCon CNP administered once-weekly in children and adolescents with achondroplasia who have completed a prior TransCon CNP clinical trial. Participants who complete a prior TransCon CNP trial and meet all eligibility criteria will be invited to continue into the long-term open label extension trial to receive 100 µg CNP/kg/week of TransCon CNP. Trial treatment will be completed when the participant reaches 16 years of age for females and 18 years of age for males and have femur and tibial epiphyseal closure. TransCon CNP treatment will continue if femur and tibial epiphyseal closure is not confirmed at the age of 16 years for females, and 18 years for males. Treatment with TransCon CNP will be completed once femur and tibial epiphyseal closure is confirmed by radiographic imaging. The trial duration is individual for each trial participant. Visits will occur every 12-14 weeks throughout the trial.

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Key information

Conditions

Achondroplasia Bone Diseases Bone Diseases, Developmental Congenital, Hereditary, and Neonatal Diseases and Abnormalities Dwarfism Endocrine System Diseases Genetic Diseases, Inborn Musculoskeletal Diseases Osteochondrodysplasias

Age range

3 year–15 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 2 / Phase 3

Primary location

Ascendis Pharma Investigational Site, Parkville, Victoria, Australia

Loading trial locations.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Written, signed informed consent of the parent(s) or legal guardian(s) of the participant, and as required by the institutional review board/human research ethics committee/independent ethics committee (IRB/HREC/IEC). For participants who are below the age of consent, a written assent will be obtained in accordance with applicable requirements as required by IRB/HREC/IEC. Upon reaching the legal age of consent, depending on applicable requirements, these participants will be asked to give their own written consent.
  • Participants with achondroplasia who have completed a clinical trial with TransCon CNP.
  • Parent(s)/legal guardian(s) willing and able to administer weekly SC injections of TransCon CNP and to follow the protocol.
  • Considered eligible based on the safety evaluations performed for evaluating stopping/holding rule criteria during the prior TransCon CNP clinical trial.

Exclusion criteria

  • Known or suspected hypersensitivity to the investigational product or related products (trehalose, tris[hydroxymethyl]aminomethane, succinate, and methoxy polyethylene glycol [mPEG]).
  • Have received any dose of prescription medications, investigational medicinal product (other than TransCon CNP).
  • Sexually active female participants and female partners of male participants of childbearing potential not using a highly effective form of contraceptive (including oral, injectable, or implantable contraception, or intrauterine device (IUD)) for the entire trial period and for 90 days post end of the trial.
  • Participants with serum 25-hydroxy-vitamin D (25OHD) levels of <50 nmol/L (<20 ng/mL) at Visit 1 must be on treatment regimen of Vitamin D supplementation.
  • Any disease or condition that, in the opinion of the investigator, may make the participant unlikely to fully complete the trial, may confound interpretation of trial results, or may present undue risk from receiving trial treatment. This could include family situations, complications or manifestations, or medications that might impact safety or be considered confounding.

Treatment and study plan

TransCon CNP

Drug

TransCon CNP drug product is a lyophilized powder in a single-use vial. Prior to use, the lyophilized powder is reconstituted with sterile water for injection and administered by subcutaneous injection via syringe and needle.

Primary outcomes

  1. Safety and Tolerability

    Time frame: Through trial completion, an average of 10 years

    Incidence of Treatment-Emergent Adverse Events

  2. Height Z-scores

    Time frame: Through trial completion, an average of 10 years

    Number of standard deviations

Secondary outcomes

  1. Annualized Growth Velocity

    Time frame: Through trial completion, an average of 10 years

    cm per year

Sponsors and collaborators

Lead sponsor

Ascendis Pharma Growth Disorders A/S

Industry

Registry information

Official study title

A Phase 2, Multicenter, Long-Term, Open Label Extension Trial Evaluating Safety, Tolerability, and Efficacy of Subcutaneous Doses of TransCon CNP Administered Once Weekly in Children and Adolescents With Achondroplasia

Acronym: AttaCH

Important dates

Study start
2023
Primary completion
2039
Study completion
2039
First posted
Jul 3, 2023
Registry last updated
Oct 27, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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