Aplagon Doses First Patient in Phase 2a Trial for Chronic Limb Threatening Ischemia

Clinical-stage biotech Aplagon has reached an important milestone in its pipeline for thrombo-inflammatory diseases.

The company announced that the first patient has been dosed in its Phase 2a HEALING clinical trial evaluating APAC, a first-in-class therapy designed to treat Peripheral Arterial Occlusive Disease that progresses to Chronic Limb-Threatening Ischemia.

The trial is currently being conducted in Finland.

Understanding APAC: A First-in-Class Therapy

APAC is a heparin proteoglycan mimetic designed to target vascular injury sites.

The therapy combines two critical mechanisms:

• Antiplatelet activity – prevents platelet aggregation
• Anticoagulant effects – reduces blood clot formation

By mimicking naturally occurring mast cell–derived heparin proteoglycans, APAC can localize to arterial injury sites, where it provides long-lasting antithrombotic and anti-inflammatory activity.

The drug can be administered either:

• Locally during vascular procedures, or
• Intravenously in hospital settings

This flexibility could support adoption by vascular surgeons and angiologists.

Details of the Phase 2a HEALING Trial

The Phase 2a study aims to evaluate the safety and early efficacy of APAC in patients with chronic limb-threatening ischemia.

Key trial details include:

• Up to 42 patients
• 4 study cohorts
• Single-dose and repeat-dose regimens
• Intravenous administration
• Conducted in Finland

The trial will examine:

• Safety and tolerability of APAC
• Preliminary efficacy signals
• Effects on thrombo-inflammatory biomarkers

The study includes both patients undergoing revascularization procedures and those receiving medical therapy alone.

Why Chronic Limb-Threatening Ischemia Is a Serious Condition?

Chronic limb-threatening ischemia is a severe stage of peripheral arterial disease caused by atherosclerosis-driven thrombo-inflammation.

The condition reduces blood flow to the limbs and can lead to:

• Severe tissue damage
• Non-healing ulcers
• Limb amputation

The first-year mortality rate is approximately 25%. Major risk factors include:

• Diabetes
• Cigarette smoking

Without improved blood flow through revascularization procedures, the risk of amputation rises significantly.

The Limitations of Current Treatments

Existing treatments for peripheral arterial disease primarily focus on symptom management rather than disease reversal. While revascularization procedures can restore blood flow, they are not always durable.

A major clinical challenge is restenosis, where arteries narrow again after treatment. Research shows that around one-third of treated arteries develop restenosis, even when patients receive standard antithrombotic therapy.

This recurring blockage remains a major limitation of current endovascular interventions.

Phase 1 Results Supported Further Development

The new Phase 2a trial follows a successful Phase 1 clinical study in 30 healthy participants.

Key findings included:

• APAC was well tolerated
• It produced dose-dependent antithrombotic effects
• Effects were transient and manageable

The trial received regulatory approval from Finnish Medicines Agency before advancing to Phase 2. In parallel, an imaging study using 89Zirconium-labeled APAC is currently underway to better understand how the drug distributes in patients and healthy volunteers.

This study is expected to conclude in H1 2026.

Expert Perspective on the Study

According to Maarit Venermo, Professor of Vascular Surgery at Helsinki University Hospital, APAC may offer several benefits for patients with limb ischemia.

Previous studies suggest the therapy can:

• Prevent platelet aggregation
• Reduce clot formation
• Decrease inflammatory responses in oxygen-deprived tissues

These mechanisms could help:

• Improve healing of ischemic tissue
• Enhance outcomes after revascularization procedures
• Reduce the need for repeat interventions

Aplagon’s Broader Clinical Development Strategy

Beyond CLTI, Aplagon is also developing APAC for arteriovenous fistula (AVF) maturation failure. AVF maturation is critical for patients with end-stage kidney disease who require lifesaving haemodialysis.

Following promising Phase 1 results, the company plans to initiate a Phase 2 trial in Europe in 2026.

The Science Behind APAC

APAC is based on pioneering research into mast cell–derived heparin proteoglycans led by Riitta Lassila at the Wihuri Research Institute in Helsinki.

The therapy is designed to:

• Target arterial injury sites
• Deliver localized antithrombotic effects
• Reduce inflammation in damaged vascular tissue

This targeted mechanism could make APAC useful across multiple thrombo-inflammatory vascular diseases.

Investors Supporting Aplagon

Aplagon is backed by a consortium of Nordic investors, including:

• FSG Fund
• Wihuri Foundation
• Innovestor
• Serlachius Foundation
• EIC Fund

Their support is helping advance APAC through clinical development as a potential first-in-class treatment for thrombo-inflammatory diseases.