Immutep (NASDAQ: IMMP) reports positive Phase I progress for LAG-3 agonist IMP761

Rhea-AI Filing Summary

Immutep Limited provided an update on its first-in-human Phase I trial of IMP761, a first-in-class LAG-3 agonist antibody for autoimmune diseases. The single ascending dose stage in healthy participants has been completed with dosing up to 14 mg/kg, and IMP761 was well tolerated with no dose-limiting toxicities reported.

The trial has now moved into the multiple ascending dose stage to further assess pharmacokinetics and safety, with completion expected in the third quarter of 2026. Early data show a clear immunosuppressive effect in a controlled antigen challenge model, supporting the planned dose levels for a future Phase II trial in patients with autoimmune conditions.

Immutep plans to present Phase I results for IMP761 at the EULAR congress in London on 4 June 2026 at 1:30 pm UK time. IMP761 targets dysregulated self-antigen-specific memory T cells via LAG-3 agonism, aiming to restore immune balance in major autoimmune diseases such as rheumatoid arthritis, Type 1 diabetes, and multiple sclerosis.

Insights

Biotech clinical development analyst

Immutep advances IMP761 with clean Phase I safety and early immune effects.

Immutep reports completion of the single ascending dose stage for IMP761, a first-in-class LAG-3 agonist antibody, with doses up to 14 mg/kg and no dose-limiting toxicities. This suggests an encouraging initial safety window in healthy participants for an immunosuppressive mechanism.

The ongoing multiple ascending dose stage focuses on pharmacokinetics and safety across two dose levels, aiming to refine exposure and tolerability ahead of patient studies. The reported durable inhibition of T cell–mediated responses in an antigen challenge model supports the drug’s intended mechanism of selectively silencing pathogenic memory T cells.

The company expects MAD completion in the third quarter of 2026 and plans to present Phase I data at the EULAR congress on 4 June 2026. These milestones frame the transition toward Phase II planning in autoimmune indications, though ultimate clinical value will depend on future patient data.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Date as March 19, 2026

Commission File Number 001-35428

IMMUTEP LIMITED

(Exact Name as Specified in its Charter)

N/A

(Translation of Registrant’s Name)

Level 32, Australia Square

264 George Street, Sydney

NSW 2000, Australia

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F ☒   Form 40-F ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1): ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7): ☐

Indicate by check mark whether by furnishing the information contained in this Form, the registrant is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes ☐   No ☒

If “Yes” is marked, indicated below the file number assigned to the registrant in connection with Rule 12g3-2(b): Not applicable.

EXHIBIT INDEX

Exhibit		Description of Exhibit
99.1		Immutep Reports Progress from Phase I Study of LAG-3 Agonist for Autoimmune Diseases

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: March 19, 2026

IMMUTEP LIMITED
By:		/s/ Marc Voigt
Name:		Marc Voigt
Title:		Chief Executive Officer

Exhibit 99.1

Immutep Reports Progress from Phase I Study of LAG-3 Agonist for Autoimmune Diseases

• Immutep has completed the single ascending dose (SAD) portion of its IMP761 study

• IMP761 was well tolerated across all dose levels

• IMP761 data and Phase I results will be presented at the EULAR conference on 4 June 2026

SYDNEY, AUSTRALIA – March 19, 2026 – Immutep Limited (ASX: IMM; NASDAQ: IMMP) (“Immutep” or “the Company”), a clinical-stage biotechnology company targeting cancer and autoimmune diseases, today announces a positive update from the placebo-controlled, double-blind first-in-human Phase I study in healthy participants evaluating IMP761, a first-in-class LAG-3 agonist antibody which enhances the physiological inhibitory function of LAG-3 on T-cell receptor signaling, potentially suppressing pathogenic T cell responses in autoimmune diseases.

The Company reported that the single ascending dose (SAD) portion of the study has been successfully completed, with dosing up to 14 mg/kg. IMP761 was well tolerated across all dose levels, and no safety concerns or dose-limiting toxicities were observed to date.

The study is currently progressing in the multiple ascending dose (MAD) portion, which is evaluating pharmacokinetics and safety across two dose levels. Completion of the MAD portion is expected in the third quarter of 2026.

“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,” said Dr Frédéric Triebel, Chief Scientific Officer, Immutep. “These first-in-human findings support our 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.”

IMP761 data, including Phase I results, will be presented at the European Alliance of Associations for Rheumatology (EULAR) annual congress in London, UK on 4^th June 2026 at 1.30 pm UK time in a poster view session.

A LAG-3 agonist represents a novel therapeutic approach aimed at restoring immune tolerance by modulating T-cell activity, with potential applications across a range of autoimmune diseases, including rheumatoid arthritis, Type 1 diabetes, and multiple sclerosis. IMP761 is the first LAG-3 agonist antibody developed to potentially treat these large, increasingly prevalent disorders, each of which represent multi-billion-dollar markets.

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 and restore balance to the immune system. LAG-3 expression on activated T cells demonstrates high specificity for disease sites, especially in tissues characterised by chronic inflammation. This distinct characteristic of the LAG-3 immune checkpoint suggests IMP761 may enable a more targeted therapeutic approach with fewer adverse effects compared to other treatments.

About IMP761

IMP761, a first-in-class immunosuppressive lymphocyte-activation gene-3 (LAG-3) agonist antibody, has the potential to address the root cause of many autoimmune diseases by specifically silencing autoimmune memory T cells that accumulate at disease sites and restoring balance to the immune system. Encouraging pre-clinical in vivo and in vitro studies show IMP761 inhibits peptide-induced T cell proliferation, activation of human primary T cells, and an antigen-specific delayed-type hypersensitivity (DTH) reaction.¹ Additional preclinical data in oligoarticular juvenile idiopathic arthritis details how IMP761 led to a decrease in 48 hours in a broad spectrum of effector cytokines in coculture experiments where patients T cells are mixed with autologous synoviocytes.² Similarly, IMP761 decreased IFNy, interleukin-4, and tumor necrosis factor a levels in supernatants from cocultures of T cells from patients with systemic sclerosis with their autologous dermal fibroblasts.³

About Immutep

Immutep is a clinical-stage biotechnology company developing novel immunotherapies for cancer and autoimmune disease. The Company is a pioneer in the understanding and advancement of therapeutics related to Lymphocyte Activation Gene-3 (LAG-3), and its diversified product portfolio harnesses LAG-3’s ability to stimulate or suppress the immune response. Immutep is dedicated to leveraging its expertise to bring innovative treatment options to patients in need and to maximise value for shareholders. For more information, please visit www.immutep.com.

Australian Investors/Media:

Eleanor Pearson, Sodali & Co.

+61 2 9066 4071; eleanor.pearson@sodali.com

U.S. Investors/Media:

Matthew Beck, astr partners

Ph: +1 (917) 415-1750; matthew.beck@astrpartners.com

This announcement was authorised for release by the CEO of Immutep Limited.

¹  Angin M, Brignone C, Triebel F. A LAG-3-Specific Agonist Antibody for the Treatment of T Cell-Induced Autoimmune Diseases. J Immunol. 2020 15;204:810-818.

² Sag E, Demir S, Aspari M, Nielsen MA, Skejø C, Hvid M, Turhan E, Bilginer Y, Greisen S, Ozen S, Deleuran B. Juvenile idiopathic arthritis: lymphocyte activation gene-3 is a central immune receptor in children with oligoarticular subtypes. Pediatr Res. 2021;90:744-751.

³  Aspari, M., Greisen, S., Hvid, M., Ong, V.H., Denton, C.P., Abraham, D. and Deleuran, B. Lymphocyte Activation Gene 3 Regulation of Profibrotic Cytokines and Type I Collagen Production in Patients With Systemic Sclerosis. ACR Open Rheumatology, 2026 8: e70120.

FAQ

What did Immutep (IMMP) announce about its IMP761 Phase I trial?

Immutep announced a positive update from its first-in-human Phase I trial of IMP761, a LAG-3 agonist antibody. The single ascending dose stage in healthy participants is complete, showing good tolerability up to 14 mg/kg with no dose-limiting toxicities observed.

How safe was IMP761 in Immutep’s Phase I healthy volunteer study?

IMP761 was reported as well tolerated across all tested dose levels in the single ascending dose stage, up to 14 mg/kg. No safety concerns or dose-limiting toxicities were observed, supporting further evaluation in the ongoing multiple ascending dose part of the trial.

What is the current status and timeline of Immutep’s IMP761 Phase I study?

The IMP761 Phase I study has completed its single ascending dose section and is now in the multiple ascending dose stage. This stage evaluates pharmacokinetics and safety at two dose levels, with completion expected in the third quarter of 2026, guiding later Phase II planning.

When will Immutep present Phase I data for IMP761 and where?

Immutep plans to present IMP761 Phase I data at the European Alliance of Associations for Rheumatology (EULAR) annual congress. The presentation is scheduled in London on 4 June 2026 at 1:30 pm UK time during a poster view session.

What diseases could Immutep’s LAG-3 agonist IMP761 potentially address?

IMP761 targets dysregulated self-antigen-specific memory T cells to restore immune tolerance in autoimmune diseases. Immutep highlights potential applications in conditions such as rheumatoid arthritis, Type 1 diabetes, and multiple sclerosis, all large and increasingly prevalent autoimmune disorders.

How does IMP761 work as a LAG-3 agonist in autoimmune disease?

IMP761 enhances the inhibitory function of LAG-3 on T-cell receptor signaling, aiming to silence pathogenic self-antigen-specific memory T cells. By restoring immune balance at disease sites with chronic inflammation, it seeks a more targeted immunosuppressive effect than broader-acting therapies.

Filing Exhibits & Attachments

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