Summary Inhibition of complement activation via human membrane‐associated complement regulators is known to prevent hyperacute rejection in heart and kidney pig‐to‐primate transplantation. The protective effect of such strategies in pulmonary xenografts, however, seems to be insufficient. In an ex vivo perfusion, model lungs from donor pigs transgenic for human CD55 (n = 6) or human CD59 (n = 5) were perfused with fresh human blood and compared with nontransgenic organs (n = 6). In addition, a soluble complement component 1 esterase inhibitor (C1‐Inh) was applied in h‐CD55 transgenic lungs (n = 3). In the h‐CD55 transgenic group, survival was prolonged (P < 0.05), quality and maximal time of oxygenation significantly improved and pulmonary vascular resistance reduced compared with the control group. There was a decreased sequestration of platelets, less parenchymal injury and reduced deposition of C5b−9 in the h‐CD55 transgenic group. Additional soluble complement inhibition (C1‐Inh) did not prolong survival of h‐CD55 transgenic lungs. Survival and pulmonary function in lungs expressing h‐CD59 was not significantly different from parameters observed in nontransgenic lungs. In this ex vivo model of pig‐to‐primate lung transplantation, membrane‐based complement inhibition resulted in significantly improved pulmonary function. However, minor histopathological injuries observed in these transgenic xenografts suggested only partial protection from pulmonary dysfunction by complement inhibition alone.

In this ex-vivo lung perfusion model, a trisaccharide polymer prevented immediate HAR, due to effective removal of alpha-Gal antibodies. In combination with additional strategies GAS914 may be a valuable tool in overcoming HAR and dysfunction of pulmonary xenografts.

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