Dimerix Confirms ACTION3 Trial Powered to Show DMX-200 Proteinuria Benefit

Statistical Review Validates ACTION3 Trial Design

Dimerix Limited (ASX:DXB) has completed a blinded statistical review of its ACTION3 Phase 3 clinical trial, confirming the study remains statistically powered above 90% to demonstrate a treatment effect of DMX-200 on proteinuria, the primary endpoint. This means that if the drug continues to reduce proteinuria as expected, there is a strong likelihood the trial will show a statistically significant benefit when completed.

The adult cohort has been fully recruited with 333 patients, surpassing initial targets, while recruitment for the pediatric cohort aged 12-17 continues independently. The last adult patient is expected to receive their final dose by March 2028, setting a clear timeline for data readout. This milestone builds on previous positive interim analyses, including a futility analysis in March 2024 that confirmed DMX-200’s performance exceeded placebo, and seven independent data monitoring committee reviews that have not raised safety concerns. These developments follow the company’s earlier blinded review preparation and recruitment achievements that laid the groundwork for this confirmation.

Proteinuria Endpoint Strengthens Regulatory Pathway

Crucially, the FDA has agreed that proteinuria reduction is an appropriate primary endpoint for full regulatory approval of DMX-200, a stance supported by recent approvals of FSGS therapies using the same measure. The PARASOL working group’s analyses, alongside data from the UK’s National Registry of Rare Kidney Diseases and Kaiser Permanente, reinforce proteinuria’s statistical robustness and lower variability compared to traditional kidney function markers like eGFR. This reduces the sample size and risk associated with trial execution.

Dimerix and its commercial partners have decided against pursuing an accelerated approval pathway, which would require a confirmatory eGFR endpoint, increasing trial complexity, cost, and risk. This strategic choice focuses resources on completing the ACTION3 study to its final proteinuria endpoint, streamlining the path to traditional approval. Dr David Fuller, Dimerix’s Chief Medical Officer, highlighted that this approach reduces clinical and commercial risks while enhancing the probability of success for both regulatory and shareholder value.

Commercial and Development Implications

The decision aligns with evolving scientific understanding of FSGS, a rare and serious kidney disease characterised by progressive scarring and proteinuria, with limited treatment options currently available. DMX-200, a chemokine receptor antagonist, is positioned to fill this unmet need, protected by patents until at least 2032 and orphan drug designations in multiple territories.

On the commercial front, Dimerix’s US licensing partner, Amicus Therapeutics, now part of BioMarin following a US$4.8 billion acquisition, remains a key collaborator in advancing DMX-200’s market entry. The strategic endpoint decision and trial progress are likely to influence upcoming licensing discussions in other territories, where Dimerix retains rights. This comes after positive FDA feedback on trial endpoints and a robust cash position reported earlier in the year, positioning the company to navigate the final phases of clinical development with confidence.

With the ACTION3 trial continuing toward completion and pediatric recruitment ongoing, the next critical juncture will be the final data readout expected in 2028. Investors will be watching how the evolving FSGS treatment landscape and regulatory environment shape the commercial prospects for DMX-200 in the coming years.