ALPN-101 (Acazicolcept) a Dual ICOS/CD28 Antagonist, Demonstrates Efficacy in Systemic Sclerosis Preclinical Mouse Models

Abstract

BackgroundUncontrolled immune response with T cell activation has a key role in the pathogenesis of systemic sclerosis (SSc), a disorder that is characterised by generalized fibrosis affecting particularly the lungs and skin. Co-stimulatory molecules are key players during immune activation, and recent evidence supports a role of CD28 and ICOS in the development of fibrosis. We herein investigated the efficacy of ALPN-101 (acazicolcept), a dual ICOS/CD28 antagonist, in two complementary SSc-related mouse models recapitulating skin fibrosis, interstitial lung disease, and pulmonary hypertension. MethodsExpression of circulating soluble ICOS and skin-expressed ICOS was investigated in SSc patients. Thereafter, ALPN-101 was evaluated in the hypochlorous acid (HOCL)-induced dermal fibrosis mouse model and in the Fra-2 transgenic (Tg) mouse model. In each model, mice received 400 µg of ALPN-101 or a molar-matched dose of an Fc control protein twice a week for six weeks. After six weeks, skin and lung were evaluated.Results ICOS was significantly increased in the sera from SSc patients and in SSc skin biopsies as compared to samples from healthy controls. Similar body weight changes were observed between Fc Control and ALPN-101 groups in both HOCL and Fra-2 Tg mice suggesting a good tolerance of ALPN-101 treatment. In mice challenged with HOCL, ALPN-101 induced a significant decrease in dermal thickness, collagen content, myofibroblast number and inflammatory infiltrates characterized by B cells, T cells, neutrophils, and macrophages. In the Fra-2 Tg mouse model, ALPN-101 treatment reduced lung collagen content, fibrillar collagen, histological fibrosis score, and right ventricular systolic pressure (RVSP). A reduction in frequency of CD4+ and T effector memory cells and an increase in the percentage of CD4+ T naïve cells in spleen and lung of ALPN-101-treated Fra-2 Tg mice was observed as compared to Fc control-treated Fra-2 Tg mice. Moreover, ALPN-101 reduced CD69 and PD-1 expression on CD4+ T cells from the spleen and the lung. Target engagement by ALPN-101 was demonstrated by blockade of CD28 and ICOS detection by flow cytometry in treated mice. Conclusions Our results confirm the importance of co-stimulatory molecules in inflammatory-driven fibrosis. Our data highlight a key role of ICOS and CD28 in SSc. Using complementary models, we demonstrated that dual ICOS/CD28 blockade by ALPN-101 decreased dermal and pulmonary fibrosis and alleviated pulmonary hypertension. These results pave the way for subsequent research on ICOS/CD28-targeted therapies.

Immune checkpoints in rheumatoid arthritis: progress and promise

“…Acaziocolcept, a dual ICOS/CD28 inhibitor trialed for therapeutic efficacy in a murine model of systemic sclerosis (79), inhibited collagen-induced arthritis more potently than Abatacept, and inhibited human T cell function more effectively than inhibition of either ICOS or CD28 alone, suggesting its potential therapeutic use in human disease (80).…”