A series of 1-phenyl-3-(1-phenylethyl) urea derivatives were identified as novel and potent complement inhibitors through structural modification of the original compound from high- throughput screening. Various analogues (7 and 13–15) were synthesized and identified as complement inhibitors, with the introduction of a five-or six-carbon chain (7c, 7d, 7k, 7l, and 7o) greatly improving their activity. Optimized compound 7l has an excellent inhibition ...