Immutep's IMP761 healthy-volunteer trial pushes MAD readout to Q3 2026
The LAG-3 antibody's single-ascending-dose phase cleared safety at 14 mg/kg with no concerns, and the ongoing multiple-ascending-dose phase will test whether that tolerability holds at repeat dosing.
Executive Summary
- Immutep's first-in-human safety study of its LAG-3 antibody IMP761 is moving through repeat-dose testing in healthy volunteers, with the sponsor guiding completion of that phase to the third quarter of 2026.
- The single-dose portion of the study cleared without safety concerns at the highest dose tested, which is why the trial advanced into the multiple-dose phase now underway.
- The trial's completion date has been pushed back twice since first posted, even as its enrollment target has held steady, a pattern that separates timeline discipline from execution risk.
- IMP761 targets LAG-3 for immune suppression rather than the checkpoint-blockade use seen in oncology programs from Regeneron and Bristol-Myers Squibb, placing it in an unproven application of an otherwise clinically established target.
The trial
NCT06637865 is testing IMP761 in healthy volunteers in the Netherlands, with adverse-event frequency, duration and severity, and clinically relevant abnormalities in ECG, safety labs, and vital signs as its six primary endpoints. The design randomizes participants against placebo across ascending single-dose and multiple-dose cohorts, an approach standard for first-in-human antibody testing. Immutep disclosed in its quarterly update that the single-ascending-dose portion has been completed with dosing up to 14 mg/kg and no safety concerns observed, and that the study is now in the multiple-ascending-dose phase. NCT06637865+1A First-in-human Study of the Safety of an Immunosuppressive Antibody (IMP761) in Healthy VolunteersNCT06637865Immutep Quarterly Activities Report Q3 FY26Apr 30, 2026
Probability of SuccessBased on the AppliedXL Probability of Success model. For more information about the methodology, read the research here.
What it targets
IMP761 is designed as an immunosuppressive antibody against LAG-3, the opposite therapeutic direction from the checkpoint-blocking LAG-3 antibodies advancing in oncology, including Regeneron Pharmaceuticals' fianlimab and Bristol-Myers Squibb's relatlimab, both in Phase 3 melanoma and lung-cancer testing. That divergent use of the same target means IMP761's healthy-volunteer safety data cannot be benchmarked against those oncology programs' results; the closest read comes from IMP761's own single-ascending-dose outcome.
The timeline shift
The trial's primary completion date has moved twice since it was first posted: from August 2025 to April 2026 in July 2025, then from April 2026 to August 2026 in April 2026. Enrollment was raised from 49 to 79 participants in the same July 2025 update and has not changed since, a Phase 1 enrollment increase that the trial's own operational baseline characterizes as within the routine band rather than a signal of distress. The completion-date slippage has occurred without an enrollment cut, consistent with a trial still recruiting toward an unchanged target rather than one in difficulty. NCT06637865A First-in-human Study of the Safety of an Immunosuppressive Antibody (IMP761) in Healthy VolunteersNCT06637865
What Q3 2026 will show
Immutep's most recent guidance points to completion of the multiple-ascending-dose phase in the third quarter of 2026, a window it later widened to the second half of 2026 in a subsequent update. That phase will test whether the tolerability profile established in single dosing, no safety concerns through 14 mg/kg, extends to repeat administration, the standard bar a Phase 1 safety study in healthy volunteers must clear before a sponsor can advance into patient populations. ImmutepImmutep Quarterly Activities Report Q3 FY26Apr 30, 2026
This analysis was produced using AI-assisted reporting systems, AppliedXL data, and official public records. These systems undergo editorial review, quality checks, and regular audits by human experts. Errors may still occur, as with any automated system. Always consult the linked primary sources. Read our AI Editorial Policy.