The figure that matters: $2.76 to $0.48. That is the round trip Immutep’s American depositary receipts made by March 13, 2026, an 82.6% wipeout that investors now blame on what the company did not tell them. A securities class action filed in May in the Southern District of New York lays out their case.
By the numbers: the suit, case 1:26-cv-03705, was filed on May 5, 2026. It names a class period running from March 24, 2025 to March 12, 2026, covers investors who held the $IMMP depository securities long, and sets 07/06/2026 as the deadline for lead plaintiff motions.
What The Suit Says Happened
During the class period, Immutep told the market that the Phase III TACTI-004 study was testing efti alongside KEYTRUDA and chemotherapy as a first-line option in advanced or metastatic forms of non-small cell lung cancer. Executives leaned on earlier results from the TACTI-002 and INSIGHT-003 studies — strong efficacy, a clean safety record, responses that lasted, encouraging survival numbers — and described enrollment in the new study as healthy and on schedule, according to the complaint.
Investors allege the public story and the internal picture diverged. The suit claims Immutep’s own trial information during that window pointed to a bigger chance that the Phase III program would fall short, that available safety and efficacy data went undisclosed, and that the upbeat earlier efti findings were no reliable guide to whether the Phase III study would hit its goals. The complaint also accuses the company of playing down risks to the trial’s efficacy, safety and future viability.
The Day The Story Broke
On March 13, 2026, Immutep disclosed that its Independent Data Monitoring Committee had recommended discontinuing TACTI-004 after weighing the available safety and efficacy data at a planned interim futility analysis. The market’s verdict was immediate: $IMMP fell $2.28 and closed at $0.48.
The complaint frames three failures: that the company overstated the trial’s prospects, that it built confidence on earlier efti findings while hiding risks specific to the new trial, and that it left shareholders unprepared for both the shutdown and the plunge in the ADR price. The alleged offences listed are misleading statements, fraud and failure to disclose, with directors and management identified as the suspected parties.
The Bottom Line
Investors will note the calendar: lead plaintiff motions are due by 07/06/2026. The allegations are just that — allegations, with no ruling on the merits — and the suit’s theory stands or falls on what Immutep knew about the interim data and when. What is not in dispute is the damage line itself: a $2.28 drop, a $0.48 close, and an 82.6% decline that turned one of the company’s central bets into a case caption.
