Thymic stromal lymphopoietin (TSLP), an epithelial cytokine (alarmin), is a central regulator of the immune response to inhaled environmental insults such as allergens, viruses and pollutants, init...

Rationale: Extensive evidence in animal models supports a role for IL-13 in the pathobiology of asthma. IMA-638 and IMA-026 are fully humanized IgG1 antibodies that bind to different epitopes and neutralize IL-13 bioactivity. Objectives: We hypothesized that anti–IL-13 treatment would inhibit allergen-induced late-phase asthmatic responses, airway hyperresponsiveness, and inflammation in subjects with asthma. Methods: Fifty-six subjects with mild, atopic asthma were recruited for two double-blind, randomized, placebo-controlled, parallel group trials to compare IMA-638 and IMA-026 IL-13 antibody treatments with placebo treatment. Drug was administered on Days 1 and 8, and allergen challenges were performed on Days 14 and 35. The primary outcome variable was the late-phase area under the curve (AUC), and secondary outcome variables were the early- and late-phase maximum percent fall in FEV1, early AUC, allergen-induced shift in airway hyperresponsiveness, and sputum eosinophils. Measurements and Main Results: The treatment difference with IMA-638 on Day 14 was −19.1 FEV1 × hour (95% confidence interval: −36.2, −1.9) for the allergen-induced early AUC and −23.8 FEV1 × hour (95% confidence interval: −46.4, −1.2) for the late AUC (both P < 0.05), but this effect was lost by Day 35. Treatment with IMA-026 did not attenuate the asthmatic responses on Day 14 or Day 35. There was no effect of either antibody on allergen-induced airway hyperresponsiveness or sputum eosinophils. The frequency of adverse events after administration of the IL-13 antibodies was similar to placebo. Conclusions: IL-13 has a role in allergen-induced airway responses in humans. Further study is required to determine whether anti–IL-13 monoclonal antibodies will be beneficial clinically. Clinical trial registered with www.clinicaltrials.gov (NCT00410280 and NCT00725582).

Rationale: Group 2 innate lymphoid cells (ILC2), a major source of type 2 cytokines, initiate eosinophilic inflammatory responses in murine models of asthma. Objectives: To investigate the role of ILC2 in allergen-induced airway eosinophilic responses in subjects with atopy and asthma. Methods: Using a diluent-controlled allergen challenge crossover study, where all subjects (n = 10) developed allergen-induced early and late responses, airway eosinophilia, and increased methacholine airway responsiveness, bone marrow, blood, and sputum samples were collected before and after inhalation challenge. Measurements and Main Results: ILC2 (lin−FcεRI−CD45+CD127+ST2+) and CD4+T lymphocytes were enumerated by flow cytometry, as well as intracellular IL-5 and IL-13 expression. Steroid sensitivity of ILC2 and CD4+ T cells was investigated in vitro. A significant increase in total, IL-5+, IL-13+, and CRTH2+ ILC2 was found in sputum, 24 hours after allergen, coincident with a significant decrease in blood ILC2. Total, IL-5+, and IL-13+, but not CRTH2+, CD4+ T cells significantly increased at 24 and 48 hours after allergen in sputum. In blood and bone marrow, only CD4+ cells demonstrated increased activation after allergen. Airway eosinophilia correlated with IL-5+ ILC2 at all time points and allergen-induced changes in IL-5+ CD4+ cells at 48 hours after allergen. Dexamethasone significantly attenuated IL-2– and IL-33–stimulated IL-5 and IL-13 production by both cell types. Conclusions: Innate and adaptive immune cells are increased in the airways associated with allergic asthmatic responses. Total and type 2 cytokine–positive ILC2 are increased only within the airways, whereas CD4+ T lymphocytes demonstrated local and systemic increases. Steroid sensitivity of both cells may explain effectiveness of this therapy in those with mild asthma.

The alarmin cytokines thymic stromal lymphopoietin (TSLP), interleukin (IL)‐33, and IL‐25 are epithelial cell‐derived mediators that contribute to the pathobiology and pathophysiology of asthma. Released from airway epithelial cells exposed to environmental triggers, the alarmins drive airway inflammation through the release of predominantly T2 cytokines from multiple effector cells. The upstream positioning of the alarmins is an attractive pharmacological target to block multiple T2 pathways important in asthma. Blocking the function of TSLP inhibits allergen‐induced responses including bronchoconstriction, airway hyperresponsiveness, and inflammation, and subsequent clinical trials of an anti‐TSLP monoclonal antibody, tezepelumab, in asthma patients demonstrated improvements in lung function, airway responsiveness, inflammation, and importantly, a reduction in the rate of exacerbations. Notably, these improvements were observed in patients with T2‐high and with T2‐low asthma. Clinical trials blocking IL‐33 and its receptor ST2 have also shown improvements in lung function and exacerbation rates; however, the impact of blocking the IL‐33/ST2 axis in T2‐high versus T2‐low asthma is unclear. To date, there is no evidence that IL‐25 blockade is beneficial in asthma. Despite the considerable overlap in the cellular functions of IL‐25, IL‐33, and TSLP, they appear to have distinct roles in the immunopathology of asthma.

Rationale: The drug product TPI ASM8 contains two modified phosphorothioate antisense oligonucleotides designed to inhibit allergic inflammation by down-regulating human CCR3 and the common beta chain (βc) of IL-3, IL-5, and granulocyte-macrophage colony–stimulating factor receptors. Objectives: This study examined the effects of inhaled TPI ASM8 on sputum cellular influx, CCR3 and βc mRNA and protein levels, and the airway physiologic response after inhaled allergen. Methods: Seventeen subjects with mild atopic asthma were randomized in a crossover study to inhale 1,500 μg TPI ASM8 or placebo by nebulizer, once daily for 4 days. On Day 3, subjects underwent allergen inhalation challenge. Sputum samples were collected before and after allergen. CCR3 and βc protein levels were measured by flow cytometry, mRNA was measured using real-time quantitative polymerase chain reaction, and the FEV1 was measured over 7 hours after challenge. Measurements and Main Results: Compared with placebo, TPI ASM8 inhibited sputum eosinophil influx by 46% (P = 0.02) and blunted the increase in total cells (63%) after allergen challenge. TPI ASM8 significantly reduced the early asthmatic response (P = 0.04) with a trend for the late asthmatic response (P = 0.08). The allergen-induced (Day 2 to Day 3) levels of βc mRNA and CCR3 mRNA in sputum-derived cells were inhibited by TPI ASM8 (P = 0.039 and P = 0.054, respectively), with no significant effects on the cell surface protein expression of CCR3 and βc (P > 0.05). No serious adverse events were reported. Conclusions: TPI ASM8 attenuates the allergen-induced increase in target gene mRNA and airway responses in subjects with mild asthma. Clinical trial registered with www.clinicaltrials.gov (NCT00264966).

The airway epithelium is the first line of defense for the lungs, detecting inhaled environmental threats through pattern recognition receptors expressed transmembrane or intracellularly. Activation of pattern recognition receptors triggers the release of alarmin cytokines IL-25, IL-33, and TSLP. These alarmins are important mediators of inflammation, with receptors widely expressed in structural cells as well as innate and adaptive immune cells. Many of the key effector cells in the allergic cascade also produce alarmins, thereby contributing to the airways disease by driving downstream type 2 inflammatory processes. Randomized controlled clinical trials have demonstrated benefit when blockade of TSLP and IL-33 were added to standard of care medications, suggesting these are important new targets for treatment of asthma. With genome-wide association studies demonstrating associations between single-nucleotide polymorphisms of the TSLP and IL-33 gene and risk of asthma, it will be important to understand which subsets of asthma patients will benefit most from anti-alarmin therapy.