Immutep completes critical Phase I milestone for first-in-class autoimmune therapy
Immutep Limited (ASX: IMM; NASDAQ: IMMP) has successfully completed the single ascending dose (SAD) portion of its Phase I study evaluating IMP761, a first-in-class LAG-3 agonist antibody for autoimmune diseases. The Immutep IMP761 Phase I results showed the therapy was well tolerated across all dose levels up to 14 mg/kg, with no safety concerns or dose-limiting toxicities observed to date.
The clinical-stage biotechnology company announced that the placebo-controlled, double-blind first-in-human study in healthy participants is now progressing to the multiple ascending dose (MAD) portion, which is evaluating pharmacokinetics and safety across two dose levels. Completion of the MAD portion is expected in Q3 2026.
The successful SAD completion de-risks IMP761 as a clinical asset and validates the novel therapeutic approach of using LAG-3 agonism to treat autoimmune diseases. This milestone brings the therapy closer to Phase II trials in actual autoimmune disease patients.
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What is a LAG-3 agonist and why does it matter?
LAG-3 (Lymphocyte Activation Gene-3) is an immune checkpoint protein that acts as a natural “brake” on T-cell activity. Understanding this mechanism is critical to appreciating IMP761’s therapeutic approach.
In cancer immunotherapy, LAG-3 antagonists are designed to release these brakes, allowing T cells to attack tumours more aggressively. IMP761 takes the opposite approach as a LAG-3 agonist, it enhances the brake function to suppress overactive immune responses.
Autoimmune diseases occur when T cells mistakenly attack the body’s own tissues, causing chronic inflammation and tissue damage. IMP761 is designed to selectively silence these misbehaving memory T cells rather than broadly suppressing the entire immune system, which is how many current autoimmune treatments work.
How IMP761 works:
- IMP761 binds to LAG-3 on activated T cells
- This enhances LAG-3’s natural inhibitory function on T-cell receptor signalling
- Pathogenic self-antigen-specific memory T cells are selectively silenced
- Immune balance is restored without broad immunosuppression
This differentiated mechanism represents a potentially significant advance over existing autoimmune treatments. If successful in clinical development, IMP761 could offer better efficacy with fewer side effects than current options, which often compromise patients’ ability to fight infections.
Clinical evidence shows durable immunosuppressive effect
The Immutep IMP761 Phase I results demonstrated a clear immunosuppressive effect in healthy participants, with particularly encouraging data on durability of response.
Dr Frédéric Triebel, Chief Scientific Officer
“IMP761 continues to show a clear immunosuppressive effect in healthy participants challenged with a foreign antigen in an intra-dermal reaction, with durable inhibition of T-cell-mediated responses after a single administration.”
The study used an antigen challenge methodology, where participants received an intra-dermal reaction (a small injection under the skin) of a foreign antigen to test IMP761’s ability to suppress T-cell responses. The therapy showed durable inhibition after a single administration, suggesting potential for convenient dosing regimens in future clinical development.
Dr Triebel added that the first-in-human findings support the mechanistic aim of selectively silencing pathogenic, self-antigen-specific memory T cells via LAG-3 agonism and provide the basis for dose levels to be tested in a future Phase II trial in patients with autoimmunity.
This early proof-of-mechanism in humans validates preclinical work and provides confidence for advancing IMP761 into patient populations with actual autoimmune diseases.
Multiple ascending dose study underway
The Phase I study is now evaluating the therapy in its MAD portion, which will provide additional safety and pharmacokinetic data critical for Phase II planning.
Upcoming catalysts and timelines:
- MAD portion evaluating two dose levels currently in progress
- Study completion expected in Q3 2026
- Data presentation at the European Alliance of Associations for Rheumatology (EULAR) annual congress in London on 4 June 2026 at 1:30pm UK time (poster view session)
The EULAR presentation represents a near-term catalyst that will provide investors and the scientific community with detailed Phase I data, including pharmacokinetic profiles and safety findings across the full dose range tested.
Multi-billion dollar market opportunity across autoimmune indications
IMP761 has potential applications across rheumatoid arthritis, Type 1 diabetes, and multiple sclerosis, each representing multi-billion dollar markets with significant unmet medical need.
As the first LAG-3 agonist antibody developed to potentially treat these increasingly prevalent disorders, IMP761 offers a differentiated approach to a crowded therapeutic landscape. LAG-3 expression on activated T cells demonstrates high specificity for disease sites, especially in tissues characterised by chronic inflammation.
This targeted characteristic of the LAG-3 immune checkpoint suggests IMP761 may enable a more targeted therapeutic approach with fewer adverse effects compared to other treatments that broadly suppress immune function.
| Attribute | Detail |
|---|---|
| Drug Candidate | IMP761 |
| Mechanism | LAG-3 agonist (enhances immune “brake” function) |
| Development Stage | Phase I (SAD complete, MAD ongoing) |
| Target Indications | Rheumatoid arthritis, Type 1 diabetes, Multiple sclerosis |
| Key Differentiator | First-in-class LAG-3 agonist antibody for autoimmune diseases |
| Market Opportunity | Multi-billion dollar markets across multiple indications |
By enhancing the physiological brake function of LAG-3 to silence dysregulated self-antigen-specific memory T cells, IMP761 is designed to target the cause of autoimmune diseases rather than simply managing symptoms. This disease-modifying approach could represent a step change in treatment paradigms.
Addressing multiple large-market indications with a single platform asset provides significant optionality for Immutep and potential for partnering interest from larger pharmaceutical companies seeking to strengthen their autoimmune portfolios.
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What comes next for Immutep’s autoimmune pipeline
Immutep has established clear near-term milestones that provide multiple potential catalysts for investors monitoring the IMP761 programme.
Upcoming milestones in chronological order:
- 4 June 2026: Phase I data presentation at EULAR congress in London (poster view session at 1:30pm UK time)
- Q3 2026: Expected completion of MAD portion of Phase I study
- Post-Q3 2026: Phase II planning based on dose selection from current study
- 2027 onwards: Potential Phase II trial initiation in autoimmune disease patients
The EULAR data presentation represents the most immediate catalyst, providing visibility into the full Phase I dataset including detailed pharmacokinetic profiles, safety findings, and evidence of immunosuppressive activity across the dose ranges tested.
Successful completion of the Phase I MAD portion will position IMP761 for advancement into Phase II trials in actual autoimmune disease patients, where the therapy’s clinical benefit can be properly assessed. The company’s parallel development of oncology assets through its broader LAG-3 platform provides additional development optionality and potential revenue streams to support the autoimmune programme.
For investors in (ASX: IMM), the successful SAD completion validates the therapeutic approach and reduces clinical risk, whilst the structured timeline of upcoming milestones provides multiple opportunities to reassess the investment thesis as new data emerges.
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