TLL-018

TYK2/JAK1 inhibitor

Investigational TYK2/JAK1 inhibitor with a small randomized chronic-spontaneous-urticaria pilot and no measured mast-cell or MCAS outcome.

How it relates to mast cells: Related inflammatory condition
Types of studies cited: Randomised controlled trial
Randomised trials in: chronic spontaneous urticaria
Approved for: nothing — Investigational

What this relationship means: Studied in people with a condition in which mast cells can contribute, but the study did not measure an effect on mast cells. This is a clinical bridge for inclusion, not a direct observation of mast cells and not an MCAS outcome.

Mechanism of action

TLL-018 is an oral small molecule designed to inhibit tyrosine kinase 2 and Janus kinase 1. Those kinases transmit signals from several cytokine receptors and are used across multiple immune-cell types. The mechanism is therefore broader than blocking a released mast-cell mediator and less mast-cell-specific than anti-IgE, BTK, or KIT targeting.

A phase Ib pilot randomized 41 people with chronic spontaneous urticaria to TLL-018 or placebo for the initial comparison. The publication reports urticaria endpoints and treatment-emergent laboratory abnormalities, but it does not report a mast-cell measurement. That distinction is why this page says it was studied in a related condition without a measured mast-cell effect despite the randomized study design.

The phase 3 CSU study is active but no longer recruiting. Its registry currently records actual enrolment while its planned completion remains in the future. Those facts make the program visible as investigational; they do not supply phase 3 results. Searches of PubMed and ClinicalTrials.gov located no direct MCAS or mastocytosis study for TLL-018.

Sources

Safety and efficacy of the selective tyrosine kinase 2/Janus kinase 1 inhibitor TLL-018 in patients with moderate-to-severe chronic spontaneous urticaria with inadequate response to H1 antihistamines: a phase Ib, randomized, double-blind, placebo-controlled pilot study Peer-reviewed study 2026 PMID 41834239 NCT05373355 · link checked 21 Aug 2026
Safety and Efficacy of TLL018 in Patients With Chronic Spontaneous Urticaria Trial registry NCT05373355 · link checked 21 Aug 2026
A Study of Efficacy and Safety of TLL-018 in CSU Participants Trial registry NCT06396026 · link checked 21 Aug 2026

What this evidence cannot establish

The published placebo-controlled pilot enrolled 41 people with chronic spontaneous urticaria, used a short randomized comparison, and identified safety as its primary endpoint. It did not enroll people with MCAS or measure a drug effect on mast cells. TYK2 and JAK1 transmit signals for multiple cytokines across several immune-cell types, so pathway activity is not a direct mast-cell-stabilization claim. The larger phase 3 CSU study is active but has no published results; registration and enrolment are not outcome evidence. TLL-018 remains investigational, and the small pilot cannot define uncommon or longer-term risks.

Registered trials

Phase 1 · Completed NCT05373355

chronic spontaneous urticaria · 41 participants enrolled

Read from ClinicalTrials.gov on 21 Aug 2026
Phase 3 · Active, not recruiting NCT06396026

chronic spontaneous urticaria · 440 participants enrolled

Read from ClinicalTrials.gov on 21 Aug 2026

What this page does not say

No dosing, and no claim that this works. The entry describes a published mechanism, the cited study types, and what those studies cannot establish — nothing further. Why the site is built this way.

Recently verified. Verified 21 Aug 2026