An Investigational Inhaled rhIL-1Ra (ALTA-2530) Demonstrates Distribution to Distal Regions of Lung and High Affinity IL-1 Receptor Blockade Supporting Development as a Treatment for Bronchiolitis Obliterans Syndrome

Abstract

<h3>Purpose</h3> Dysregulated expression of interleukin-1 (IL-1), and downstream cytokines including IL-6, has been implicated in the development and progression of bronchiolitis obliterans syndrome (BOS). Quiescence of IL-1 signaling via blockade of the IL-1 receptor type 1 (IL-1R1) is proposed to restore physiologic immune regulation. Herein, we characterize ALTA-2530: i) distribution in rat and non-human primate (NHP) lung tissue following aerosolized administration, ii) binding affinity to IL-1R1, and iii) <i>in vitro</i> suppression of IL-6 release to assess potency of receptor blockade and development of an exposure response relationship to guide dose selection for <i>in vivo</i> studies. <h3>Methods</h3> Bronchoalveolar lavage fluid (BALF) and lung tissue samples were collected from rat and NHP following 7 daily inhaled doses of ALTA-2530. ALTA-2530 was determined in BALF by affinity capture LC-MS/MS. Tissues were processed for immunohistochemistry to identify the distribution of rhIL-1Ra. Binding kinetics of rhIL-1Ra to human IL-1R1 were determined by surface plasmon resonance and compared to IL-1α and β. ALTA-2530 mediated inhibition of IL-6 release in human and NHP whole blood was determined following stimulation by IL-1β. <h3>Results</h3> Once daily administration of ALTA-2530 provided >24hr exposure in BALF. Immunohistochemistry of lungs from healthy rats and NHPs 24hr post dose demonstrated dose-dependent delivery of ALTA-2530 to alveoli and bronchial epithelial cells. Early data also indicate association with alveolar macrophages. Distribution to narrow rat bronchioles is supportive of therapeutically relevant distribution in human bronchioles - a target for the treatment of BOS. ALTA-2530 rhIL-1Ra bound to IL-1R1 with over 100X greater affinity (K_D∼10⁻¹² M, k_d∼10⁻⁵ s⁻¹, k_a∼10⁶ M⁻¹s⁻¹) than endogenous IL-1 agonists IL-1α (K_D∼10⁻⁷ M, k_d∼10⁻³ s⁻¹, k_a∼10³ M⁻¹s⁻¹) and IL-1β (K_D∼10⁻¹⁰ M, k_d∼10⁻³ s⁻¹, k_a∼10⁷ M⁻¹s⁻¹). Functional potency for IL-1R1 blockade in whole blood demonstrated ALTA-2530 rhIL-1Ra potently inhibited IL-6 release following IL-1β stimulation (human IC₅₀ 5 ng/mL; NHP IC₅₀ 7 ng/mL). <h3>Conclusion</h3> Inhaled ALTA-2530 distributes to distal regions of lung and inhibits IL-6 release supportive of a therapy for IL-1 and IL-6 driven pathologies including BOS.