TOPaZ trial still recruiting

TOPaZ is a randomised open-label clinical trial for people with osteogenesis imperfecta (OI). The study aims to investigate whether a two-year spell of treatment with a drug called teriparatide (TPTD) followed by treatment with another drug called Zoledronic acid (ZA) reduces the risk of broken bones occurring in people with OI.

The TOPaZ trial receives funding for a 24 month extension

The TOPAZ trial has received funding for an additional 24 months to compensate for the interruption of recruitment imposed by the COVID-19 pandemic. The trial is designed to determine if anabolic therapy with Teriparatide (TPTD) followed by a single infusion of zoledronic acid (ZA) is superior to standard care in adults with osteogenesis imperfecta (OI). The trial is open to anyone over 18 years with OI whether or not they have previously been treated. The only exception is people who have received anabolic therapies in the past two years.

25 study centres aim at 350 participants

topaz graphicThe trial now has 25 study centres actively recruiting in the UK with additional European centres in Dublin, Paris and Amsterdam. A new study centre is being added in Zwolle, the Netherlands, where the local PI is Dr. Hans Feenstra, and in Aarhus, Denmark where the local PI is Professor Bente Langdahl.

Professor Stuart H. Ralston the Chief investigator said “We are delighted that the funder has granted this 24 month extension which will allow us to complete this important study which has been designed to determine if TPTD and ZA is more effective than standard care at preventing fractures in adults with OI.”

At the present time the investigators have recruited 310 people which makes it the largest every clinical trial in adults with osteogenesis imperfecta by a long way (Figure).

white man wearing a doctor's shirt with a stetoscopeRecruitment closes at end of November 2022

The investigators are aiming to reach their target of 350 before recruitment is scheduled to close at the end of November 2022. With the additional funding the study is due to run until the end of 2024, with closeout scheduled for April 2025. If you are interested in taking part in the study please feel free to email the study team on or Professor Stuart H. Ralston, the Chief Investigator on for further information.

More information can also be found here.

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