Bloomsbury Genetic Therapies Announces Initiation of Recruitment in Phase 1/2 HORACE Clinical Trial of Investigational Gene Therapy BGT-OTCD for the Treatment of Ornithine Transcarbamylase Deficiency (OTCD)

– HORACE trial initiated to evaluate the safety, efficacy and tolerability of BGT-OTCD in paediatric patients diagnosed with OTCD –


London, UK, 16 November 2023 – Bloomsbury Genetic Therapies Limited, a clinical-stage biotechnology company developing potentially curative treatments for patients suffering from rare neurological and metabolic diseases based on clinically proven gene therapy technologies, announced today that the Company’s collaborator, University College London (UCL), has initiated recruitment in the Phase 1/2 clinical trial HORACE (Halting Ornithine transcarbamylase deficiency with Recombinant AAV in ChildrEn, NCT05092685) evaluating BGT-OTCD, Bloomsbury’s investigational AAV-LK03 gene therapy, in paediatric patients diagnosed with OTCD.

HORACE is an open-label, safety, efficacy and dose-finding trial and will enrol up to 12 patients aged between 0 and 16 years old diagnosed with OTCD. UCL is the sponsor of the trial with financial support provided by the Company. HORACE will be conducted at a single treatment site, Great Ormond Street Hospital (GOSH) in London, UK, with three further referring UK sites: Evelina London Children’s Hospital, Royal Manchester Children’s Hospital and Birmingham Children’s Hospital.

“OTCD is a devastating disease, particularly in the paediatric population. Current medical management of children with OTCD and dietary protein restriction do not prevent recurrent metabolic crises and don’t fully address the sub-clinical chronic neuronal damage caused by elevated blood ammonia levels, and its impact on children’s neurological development. I am therefore very pleased that recruitment has been initiated in the HORACE trial and look forward to evaluating BGT-OTCD as a potentially curative solution for children with OTCD”, said Dr Anupam Chakrapani, Consultant in Metabolic Medicine, GOSH and the trial’s Principal Investigator.

“The initiation of our first clinical trial just a year after Bloomsbury’s launch is a landmark moment for us. BGT-OTCD is a highly differentiated gene therapy candidate for OTCD, relying on the best-in-class capsid AAV-LK03, whose efficacy, durability and safety has already been illustrated in the clinic in haemophilia A clinical trials, and we believe it has curative potential for both paediatric and adult patients suffering from OTCD,” said Adrien Lemoine, Co-Founder & Chief Executive Officer of Bloomsbury. “We look forward to UCL sharing initial clinical data with the OTCD community in due course.”

For more information on the Phase 1/2 HORACE trial of BGT-OTCD for the treatment of OTCD, please visit: and for more information about participation to the trial, please contact


– ENDS –



JW Communications

Julia Wilson

Tel: +44 (0)7818 430877


About Bloomsbury Genetic Therapies

Bloomsbury is a clinical-stage biotechnology company, developing potentially curative treatments for patients suffering from rare neurological and metabolic diseases based on clinically proven gene therapy technologies. The Company was spun out of University College London and launched in October 2022 with funding from UCL Technology Fund. Bloomsbury is building a pipeline of highly differentiated first- or best-in-class programs. For more information, please visit


About Ornithine transcarbamylase deficiency

Ornithine transcarbamylase deficiency (OTCD) is a rare, X-linked genetic disorder that is characterised by complete or partial lack of the OTC enzyme. OTC enzyme is a key component of the urea cycle and patients with OTCD accumulate nitrogen waste in the form of excess ammonia (hyperammonaemia) in the blood, causing hyperammonaemic decompensations with symptoms including vomiting, impaired voluntary movement and progressive lethargy. If left untreated, these may progress to coma and life-threatening complications. While later onset disease can occur in adults with a milder form of the disorder, symptoms present within a few days of birth of males with severe OTCD. Patients are rapidly diagnosed (urine and blood biochemical analyses, gene sequencing) when they present at hospital/are admitted to intensive care with acute hepatic decompensation and hyperammonaemia.

Current standard of care involves protein-restricted diets and ammonia-scavenger medications; however, these approaches can have a significant impact on patients’ quality of life and patients still face a lifelong risk of decompensation and neurological damage resulting in intellectual disability, developmental delays, and movement disorder. Liver transplant is the only curative option, but is often unavailable and comes with significant morbidity/mortality risk and lifelong immunosuppression and arginine supplementation. Over 10,000 patients suffering from OTCD have been identified worldwide.



BGT-OTCD is an investigational AAV-LK03 gene therapy designed to provide a potentially curative solution to OTCD patients following a one-time intravenous injection. AAV-LK03 was selected for its high tropism for liver cells and its success in other liver disorders such as haemophilia A. BGT-OTCD has been granted Orphan Drug Designation (ODD) for the treatment of OTCD by the European Commission (EC) and the US Food and Drug Administration (FDA) as well as Rare Pediatric Disease Designation (RPDD) from the FDA.  BGT-OTCD is currently being evaluated in HORACE (Halting Ornithine transcarbamylase deficiency with Recombinant AAV in ChildrEn; NCT 05092685), a Phase 1/2 clinical trial initiated in November 2023.