TL-925, a First-in-class, Topical, Bruton’s Tyrosine Kinase (BTK) Inhibitor Regulates the Ocular Inflammatory Response

Abstract

Purpose : Mast cells (MCs) play an early and critical role in the immune cascade underlying the development of dry eye disease (DED) and allergic conjunctivitis (AC). In DED, MC-driven lacrimal unit dysfunction with desiccating stress leads to reduced tear film production, cytokine-mediated inflammation, and ocular damage. In AC, allergen exposure triggers MC degranulation and the release of pro-inflammatory mediators causing ocular symptoms. BTK plays a key role in MC activation, cytokine production, and the immune response. Our novel and comprehensive strategy for treating DED and AC uses TL-925 (925), a topical formulation of the potent, irreversible, BTK inhibitor TL-895 (895). 895’s effect in vitro and 925’s effect in vivo were assessed.

Methods : Primary human MCs derived from bone marrow CD34⁺ cells were used to evaluate the effects of 895 on antigen-stimulated BTK phosphorylation, activation, calcium flux, histamine release, and cytokine production via multi parameter flow cytometry. Exposure and target BTK occupancy were studied in ocular dog tissue with an ELISA based assay after repeat dosing of 50μL 925 bilaterally twice daily for 15 days.

Results : In primary MCs, 895 prevented BTK phosphorylation (EC₉₀=111nM) and potently inhibited surface expression of CD63, a marker of MC activation and degranulation (EC₉₀=107nM; Figure 1). 895 also potently inhibited calcium flux (100nM), histamine release (EC₉₀=75nM), and the production of cytokines that recruit and activate inflammatory immune cells (eg, IL-8; MCP-1; Figure 1). In dogs, optimal drug exposure (≥EC₉₀)of 925 was observed in the relevant ocular target tissue with median BTK occupancy >95% established in the palpebral and bulbar conjunctiva (Figure 2).

Conclusions : 895 inhibits MC-driven immune and cytokine responses in DED and AC. In vitro, 895 prevented MC activation, degranulation, and cytokine production, indicating potent modulation of the innate and adaptive immune response. In vivo, ocular administration of 925 ensured near-complete inhibition of BTK to target tissue at optimal drug concentrations. Together, these nonclinical data support the potential of 925 as an exciting and novel treatment for patients afflicted with mast cell-driven ocular disorders.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Figure 1: TL-895 Potently Inhibits the Mast Cell Inflammatory Response

 

Figure 2: TL-925 Achieves Optimal Exposure in Canine Target Tissue