D29-21 Evaluation of the Antifibrotic Effect of Zampilimab, a Monoclonal Antibody Targeting Human Transglutaminase-2, in a Humanized Mouse Model of Pulmonary Fibrosis

Rationale Zampilimab is a humanized monoclonal antibody that selectively blocks transamidation of human tissue transglutaminase-2 (hTG2)1 and has recently completed a Phase Ib clinical trial in patients with Idiopathic Pulmonary Fibrosis (IPF)2. In this study, we generated a novel homozygous humanized mouse model that ubiquitously expresses hTG2. Pulmonary fibrosis was induced in male hTG2 mice using bleomycin (BLM), establishing a robust disease model. The antifibrotic effects of zampilimab were assessed in vivo through longitudinal micro-computed tomography (µCT) imaging, lung function tests, histological evaluation, and immunofluorescence analysis. Methods BLM was administered on days 0 and 4 via oropharyngeal aspiration in hTG2 male C57bl/6 mice. Longitudinal µCT imaging and cross-sectional analyses were performed at days 7, 14, and 21 to monitor lung fibrosis development. In the pharmacological study, BLM-treated mice were divided into two groups and intravenously dosed with either zampilimab 100 mg/kg or vehicle on days 7 and 14, whereas saline-treated mice served as the control group. For each mouse and timepoint, structural biomarkers such as %Non-aerated areas and %Gas, as well as the functional %Ventilated areas and regional tidal volume (TV), were extracted from µCT scans3,4. On day 21, lung function was assessed using Flexivent, fibrosis was quantified by histology and hTG2 transamidation was analyzed using a cadaverine-based immunoassay on cryosections. Results BLM administration in hTG2 mice led to an increase in %Non-aerated areas, corresponding to fibrotic lung regions, with a peak at day 14 that remained stable through day 21, parallel with an increase of TG2 transamidation activity.Conversely, %Gas and %Ventilated areas progressively declined until day 21, resembling the progression observed in wild-type mice.Zampilimab treatment significantly slowed down the increase in non-aerated tissue and attenuated the decline in lung ventilation, thereby improving parenchymal stiffness as assessed by TV. The therapy significantly improved the forced vital capacity compared to vehicle, reduced fibrosis severity as measured by Ashcroft score, and reduced hTG2 transamidation on lung cryosections. Conclusion We established a lung fibrosis model in hTG2 mice, providing an invaluable tool to study the role of TG2 in vivo. Zampilimab was well tolerated and significantly improved µCT parameters, lung function, histological outcomes, and reduced tissue stiffness. Additionally, the decrease in hTG2 transamidation suggests the implication of the enzyme in lung fibrosis development, strongly supporting the clinical translation of zampilimab as a potential therapeutic option for patients with IPF. References: 1. Huang L. PLoS One. 2024. 2. Vitiello G. Am.J.Resp.Crit.Care.Med. 2025. 3. Ferrini E. Methods: in Mol.Biology. 2025. 4.Buccardi M. Resp.Res. 2023 This abstract is funded by: Chiesi Farmaceutici S.p.A.