Spatial transcriptomic validation of a biomimetic model of fibrosis enables re-evaluation of a therapeutic antibody targeting LOXL2

Matrix stiffening by lysyl oxidase-like 2 (LOXL2) mediated collagen cross-linking is proposed as a core feed-forward mechanism that promotes fibrogenesis. Failure in clinical trials of simtuzumab (the humanized version of AB0023, a monoclonal antibody against human LOXL2) suggested targeting LOXL2 may not have disease relevance, however target engagement was not directly evaluated. We compared the spatial transcriptome of active human lung fibrogenesis sites with different human cell culture models to determine the model with greatest disease relevance. Within the selected model system, we then evaluated AB0023, identifying that it did not inhibit collagen cross-linking or reduce tissue stiffness, nor did it inhibit LOXL2 catalytic activity. In contrast it did potently inhibit angiogenesis consistent with an alternative, non-enzymatic mechanism of action. Thus, AB0023 is anti-angiogenic but does not inhibit LOXL2 catalytic activity, collagen cross-linking or tissue stiffening. These findings have implications for the interpretation of lack of efficacy of simtuzumab in clinical trials of fibrotic diseases. To compare different model systems for fiboblastic foci, we cultured primary fibroblasts in different culture conditions including standard 2D culture, 2D culture with ficoll (scar-in-a-jar), and 3D spheroids, with and without the profibrotic cytokine TGF-β