C5AR1 and COVID-19: Studies have shown that pharmaceutical targeting of complement at the level of the C5–C5a–C5aR1 axis or at glucosylceramide synthase (GCS) inhibited the replication of SARS-CoV-2, and the SARS-CoV-2 or GC-induced immune inflammation and tissue destruction in COVID-19 and GD [78,79,80,81,82].