• First paediatric patient for Dimerix’s ACTION3 phase III clinical trial into a rare kidney disease has been recruited at a UK specialist site
• A total of 19 specialist paediatric clinical sites across Argentina, Mexico, the UK and US will recruit patients to ACTION3

• Paediatric development plan for lead drug DMX-200 aims to collect sufficient data for marketing approval in children aged over one

Special Report: Dimerix has achieved a key milestone in its ACTION3 phase III trial of lead asset DMX-200 into focal segmental glomerulosclerosis (FSGS) kidney disease with the first paediatric patient recruited at a site in Manchester, UK.

Dimerix (ASX:DXB) said 19 of the planned ~170 study sites involved in the ACTION3 trial were specialist paediatric kidney centres across the UK, USA, Mexico and Argentina.

The sites were chosen to recruit patients aged 12-17 with FSGS to support potential marketing approval in the paediatric population.

Patients in the paediatric cohort of the blinded ACTION3 trial will be randomised –  unknowingly placed on either placebo or DMX-200 – and followed for two years.

Dimerix said dosage of DMX-200 to be used in paediatric patients participating in the trial would be the same dose as provided to adults in the trial, 120mg twice daily.

The company said the Independent Data Monitoring Committee (IDMC) noted that the safety margin of DMX-200 should allow the trial to proceed in this paediatric population using adult doses.

Targeting widespread DMX-200 approval

FSGS is a rare condition affecting the kidney’s filtering units, where blood is purified, resulting in permanent kidney damage and eventual organ failure, necessitating either dialysis or a transplant.

There are currently no drugs currently approved specifically for FSGS treatment worldwide, significantly restricting available options and affecting overall prognosis.

Consequently, DMX-200 has been granted Orphan Drug Designation in the US and Europe, as well as the equivalent Innovative Licensing and Access Pathway (ILAP) designation in the UK.

FSGS is one of the leading causes of kidney failure in children, with 20% of all presentations of nephrotic syndrome in paediatric patients caused by FSGS.

Should the paediatric cohort aged 12-17 years old be successful, and DMX-200 be approved in adults, Dimerix said it could expand approval for the drug and market it to paediatric patients in key territories, including the US and Europe.

The DMX-200 paediatric development plan aims to collect sufficient data for potential marketing approval in children aged over one in accordance with the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) expectations, with key components including:

• Paediatric patients aged from 12-17 to be included in current ACTION3 trial in patients with FSGS, in line with FDA and EMA advice
• In silico (computer) modelling, simulation, and extrapolation of paediatric data from ACTION3 to support confirmatory small open-label study in children aged one to 11

Interim analysis on track for August 2025

Titled Angiotensin II Type 1 Receptor (AT1R) & Chemokine Receptor 2 (CCR2) Targets for Inflammatory Nephrosis – or ACTION3 – the phase III trial is a multi-centre, randomised, double-blind, placebo-controlled study.

ACTION3 is evaluating the efficacy and safety of DMX-200 in patients with FSGS who are receiving a stable dose of an angiotensin II receptor blocker (ARB).

Once the ARB dose is stable, patients will be randomised to receive either DMX-200 (120mg capsule twice daily) or placebo.

The single phase III trial in FSGS patients has interim analysis points designed to capture evidence of proteinuria and kidney function (eGFR slope) during the trial, aimed at generating sufficient evidence to support marketing approval.

ACTION3 successfully passed its first interim analysis using the proteinuria efficacy endpoint.

Dimerix said planned blinded interim data collection is anticipated in August 2025, following 35 weeks of dosing of the first 144 patients.

“The recruitment of the first paediatric patient for ACTION3 is highly significant, being the first step towards providing a potential new treatment for children with FSGS,” Dimerix chief medical officer Dr David Fuller said.

“The study is entering a very exciting phase as we open the last remaining study sites and work towards full recruitment later this year, as well as the blinded interim analysis anticipated in August 2025.”

This article was developed in collaboration with Dimerix, a Stockhead advertiser at the time of publishing.

This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.