Synthesis and activity of tetrapeptidic HTLV-I protease inhibitors possessing different P3-cap moieties

The causative agent behind adult T-cell leukemia and tropical spastic paraparesis/HTLV-I-associated myelopathy is the human T-cell leukemia virus type 1 (HTLV-I). Tetrapeptidic HTLV-I protease inhibitors were designed on a previously reported potent inhibitor KNI-10516, with modifications at the P3-cap moieties. All the inhibitors showed high HIV-1 protease inhibitory activity (over 98% inhibition at 50 nM) and most exhibited highly potent inhibition against HTLV-I protease (IC50 values were less than 100 nM).