Dimerix Doses Final Adult Patient in Pivotal Kidney Trial, Eyes 2028 Approval

Dimerix completes adult patient dosing in pivotal FSGS trial

Dimerix Limited (ASX: DXB) has completed dosing of the final adult patient in its DMX-200 Phase 3 Trial, with 333 patients now randomised and dosed in the ACTION3 study. The trial has closed to further adult recruitment, exceeding the original target of 286 patients after allowing consented patients already in screening to complete enrolment. Full study completion, including the 2-year treatment period for all participants, is expected in March 2028.

The over-recruitment occurred as standard practice allowed patients progressing through screening when the 286th patient was reached to continue if still eligible. Paediatric cohort recruitment continues independently as per regulatory agreement. The ACTION3 trial spans 219 sites across 21 countries, including the US, Europe, UK, Japan, China, Hong Kong, Taiwan, Malaysia, Australia and New Zealand.

Dr Nina Webster, CEO & Managing Director, Dimerix

“I am delighted with the achievement of such a significant milestone in the Company’s clinical development of DMX-200 in FSGS patients. By allowing patients who had been progressing through the screening process at the time 286 patients had been randomised and dosed, we have naturally recruited beyond the targeted 286 adult patients. This will ultimately support the statistical powering of the study endpoints.”

The additional patients strengthen the statistical power of the trial’s endpoints, potentially enhancing the regulatory submission case. With recruitment execution risk now substantially reduced, investor focus shifts to data quality and regulatory outcomes.

What is FSGS and why does it need new treatments?

Focal segmental glomerulosclerosis (FSGS) is a rare, serious kidney disorder characterised by progressive scarring in the glomeruli, the kidney’s filtering units. This scarring leads to proteinuria (excess protein in urine), progressive loss of kidney function, and often end-stage renal disease requiring dialysis or transplantation.

The disease is increasingly understood to have an inflammatory component, with monocyte and macrophage activation contributing to glomerular injury. More than 40,000 people are estimated to be living with FSGS in the United States, including both adults and children.

There are no therapies specifically approved for FSGS in the US. Disease management relies on non-specific immunosuppressive and supportive therapies. In patients with progressive or treatment-resistant FSGS, the average time from diagnosis to end-stage kidney disease can be as short as five years. Even among those who undergo kidney transplantation, disease recurrence occurs in up to 60% of cases.

The absence of approved FSGS therapies creates significant commercial opportunity for DMX-200 if clinical trial outcomes support regulatory approval.

ACTION3 trial design and progress to date

The ACTION3 Phase 3 study is a pivotal, multi-centre, randomised, double-blind, placebo-controlled trial evaluating the efficacy and safety of DMX-200 in FSGS patients receiving a stable dose of an angiotensin II receptor blocker (ARB), a blood pressure medication that represents standard of care treatment.

Once the ARB dose is stable, patients are randomised to receive either DMX-200 (120 mg capsule, twice daily) or placebo for a 2-year treatment period. The single Phase 3 trial is designed to capture evidence of proteinuria reduction and kidney function (eGFR slope) to generate sufficient evidence supporting marketing approval.

Key trial parameters:

1. Design: Pivotal Phase 3, multi-centre, randomised, double-blind, placebo-controlled
2. Dosing regimen: DMX-200 120 mg capsule twice daily alongside stable ARB dose
3. Treatment period: 2 years
4. Primary endpoints: Proteinuria reduction and kidney function (eGFR slope)
5. Geographic scope: 21 countries across US, Europe, UK, Japan, Asia-Pacific
6. Safety oversight: 7 successful IDMC reviews with no protocol changes or safety concerns

In March 2024, Dimerix reported that the trial was successful in the pre-specified interim analysis of the proteinuria (efficacy) endpoint from the first 72 randomised patients. The analysis indicated that DMX-200 was performing better than placebo in reducing proteinuria in patients with FSGS.

The study has now successfully passed seven scheduled Independent Data Monitoring Committee (IDMC) reviews with no changes to the protocol required or safety concerns identified. This clean safety record through multiple independent reviews substantially de-risks the regulatory pathway and supports the therapy’s favourable benefit-risk profile.

Understanding proteinuria as a kidney disease marker

Proteinuria refers to excess protein in the urine, indicating damage to the kidney’s filtering system. In healthy kidneys, the glomeruli prevent most proteins from passing into the urine. When these filters are damaged, as occurs in FSGS, proteins leak through.

Proteinuria is a surrogate marker of kidney disease progression. Reducing proteinuria is associated with slowing disease progression toward kidney failure. The FDA’s acceptance of proteinuria reduction as a meaningful endpoint in kidney disease trials supports DMX-200’s regulatory strategy.

The March 2024 interim analysis demonstrated DMX-200’s superiority over placebo in reducing proteinuria at that point in the trial, though interim analysis data does not guarantee a statistically significant outcome at trial completion.

Next steps and commercial positioning

Following the successful outcome of the PARASOL collaboration data analysis on eGFR and proteinuria endpoints, Dimerix plans to conduct a blinded statistical powering analysis of the primary endpoint in the ACTION3 study in line with FDA guidance.

DMX-200 is a chemokine receptor (CCR2) antagonist administered to patients already receiving an angiotensin II type I receptor (AT1R) blocker. The therapy is protected by granted patents in various territories until 2032, with patent applications submitted globally that may extend patent protection to 2045. DMX-200 has received Orphan Drug Designation in the United States, Europe, UK and Japan.

Orphan Drug status provides regulatory incentives, potential fee waivers, and market exclusivity in major territories. This designation validates the unmet medical need in FSGS and supports commercial viability.

The company remains positioned to advance licensing opportunities with potential partners in territories not already licensed, while existing commercial partnerships continue to support development in licensed regions.

What this means for Dimerix shareholders

Completion of adult patient dosing in the DMX-200 Phase 3 Trial removes recruitment execution risk and positions the company for upcoming value inflection points. Over-recruitment to 333 patients enhances statistical power, potentially strengthening regulatory submissions.

Management has stated the company remains well positioned to advance toward regulatory submission, potential approval, and commercialisation of DMX-200. Upcoming potential catalysts include:

• Completion of paediatric cohort recruitment
• Blinded statistical powering analysis of primary endpoint
• Full study completion and primary data readout (March 2028)
• Regulatory submission preparation in the US and other territories
• Partnership expansion in unlicensed territories

With clinical execution substantially de-risked through successful recruitment, clean safety reviews, and positive interim efficacy signals, investor attention now centres on data quality at study completion and commercial outcomes. The company’s existing partnerships validate DMX-200’s commercial potential, while ongoing licensing discussions position Dimerix to maximise global market access.

The trial’s scale, spanning 219 sites across 21 countries, demonstrates Dimerix’s clinical execution capability and positions the therapy for global regulatory submissions if trial outcomes support marketing approval.

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