Tvardi Reports Positive Phase 1 Results for Oral STAT3 Inhibitor TTI-109

On July 7, 2026, Tvardi Therapeutics  announced Phase 1 results for TTI-109, its next-generation oral STAT3 inhibitor and phosphate prodrug of TTI-101. Conducted in healthy volunteers, the three-part study met all primary objectives confirming rapid prodrug conversion, equivalent drug exposure at molar-equivalent doses, and a notably improved gastrointestinal tolerability profile over TTI-101. An exploratory pharmacodynamic analysis added a clinically meaningful dimension: reductions of up to 60% in STAT3-driven immune cell populations, a pharmacodynamic signal that would not typically be expected in a healthy volunteer setting.

STAT3: A High-Value but Difficult Target

STAT3 is a transcription factor at the crossroads of multiple inflammatory and proliferative signalling pathways cytokines, growth factors, Th17, T follicular helper (Tfh) and B cell cascades. In STAT3-driven diseases of the skin, gastrointestinal tract, and in cancer, its chronic activation sustains immune dysregulation, fibrosis, and unchecked cell survival. Because STAT3 sits downstream where these pathways converge, a single oral STAT3 inhibitor could target what no individual biologic can multiple disease drivers at once.

TTI-109: The Prodrug Rationale

TTI-101, Tvardi’s first-generation direct STAT3 inhibitor currently in a Phase 1b/2 trial in hepatocellular carcinoma (NCT05440708), showed gastrointestinal tolerability challenges  specifically diarrhea duration at higher doses. TTI-109 addresses this through a phosphate prodrug modification: chemically engineered to improve absorption and GI tolerability, then rapidly cleaved back to active TTI-101 after absorption, preserving identical mechanism of action with better delivery.

Phase 1 Study Design:

The study ran in three sequential parts:

Part A: Randomised, double-blind, placebo-controlled single ascending dose (SAD) at four dose levels (n=8/cohort), to evaluate safety, tolerability, and initial pharmacokinetics.

Part B: Bioequivalence crossover comparing TTI-109 and TTI-101 in both sequences with a 48-hour washout (n=6/sequence), to confirm exposure equivalence at molar-equivalent doses.

Part C: Randomised, double-blind, placebo-controlled multiple ascending dose (MAD) with 21 days of twice-daily dosing at four dose levels, plus a TTI-101 reference arm (n=8/cohort), to assess repeat-dose pharmacokinetics and tolerability.

Primary objectives covered rapid prodrug conversion, exposure equivalence, dose-proportional pharmacokinetics, and tolerability versus TTI-101 and placebo. Pharmacodynamic effects on immune cell populations were an exploratory objective.

Key Results

All primary objectives were met:

Prodrug conversion confirmed: TTI-109 converted to TTI-101 within two hours across all cohorts, validating the prodrug design at the most fundamental level.

Exposure equivalence: TTI-109 produced nearly identical TTI-101 plasma levels at molar-equivalent doses, demonstrating that the chemical modification does not compromise drug delivery.

Sustained target-level exposure: 21-day repeat dosing showed stable, dose-proportional pharmacokinetics, with TTI-101 plasma concentrations maintained above the STAT3 IC₅₀ throughout the dosing period.

Improved tolerability: Diarrhea event duration with TTI-109 was substantially shorter than with TTI-101 at near-equivalent doses (0.46 vs. 3.35 days). Compared to placebo, diarrhea events were similar in duration, transient, and resolved without any treatment interruption.

Pharmacodynamic target engagement: An exploratory analysis showed reductions of up to 60% in Th17 cells, T follicular helper (Tfh) cells, and B cells disease-relevant STAT3-driven immune cell populations a signal uncommonly observed in healthy volunteers and indicative of meaningful biological activity.

Clinical Implications

Imran Alibhai, Ph.D., Chief Executive Officer of Tvardi, stated that the results validated the prodrug strategy on every objective set, noting that TTI-109 matched TTI-101’s exposure with substantially better tolerability and delivered a pharmacodynamic signal across immune cell populations that would not typically be expected in healthy volunteers a combination that supports advancing into Phase 2.

Path Forward

Tvardi has identified dermatologic and gastrointestinal diseases driven by STAT3 including conditions where Th17 and B cell pathways are central as its priority therapeutic areas for TTI-109. Initiation of Phase 2 trials is contingent on IND clearance and the availability of additional funding. In parallel, Tvardi continues to advance TTI-101 in HCC (NCT05440708), with Phase 1b/2 topline data expected in the second half of 2026.

What This Means?

For patients with STAT3-driven inflammatory diseases of the skin and gut, current treatment options are predominantly injectable biologics that each block a single upstream pathway meaning patients often cycle through multiple agents, sometimes without durable response. An oral STAT3 inhibitor acting at the point of convergence of these pathways could theoretically offer broader anti-inflammatory coverage in a more accessible form. TTI-109’s Phase 1 package conversion confirmed, exposure matched, tolerability improved, and a pharmacodynamic signal generated in healthy volunteers is a scientifically coherent basis for a Phase 2 programme, provided the funding and regulatory pathway align.

Reference

Tvardi Therapeutics’ TTI-109 Phase 1 Study Confirms Prodrug Design, Improved Tolerability and Pharmacodynamic Evidence of STAT3 Target Engagement. Tvardi Therapeutics. July 7, 2026.