Table 4.

Potency of selected HNE inhibitors (with IC₅₀ <100 nM) over extended period of time (16 h).

Compounds	Remaining HNE activity (%)a
3a	5.5 ± 1.8
3b	20.5 ± 1.7
3c	2.0 ± 0.4
3d	4.3 ± 0.3
3e	41.7 ± 3.2
3f	5.9 ± 1.2
3g	20.1 ± 1.6
3i	2.6 ± 0.5
3j	26.2 ± 3.4
3l	4.5 ± 1.7
4	8.6 ± 1.7
7d	9.1 ± 2.5
9a	2.2 ± 0.1
9b	9.2 ± 2.5
Sivelestat	3.7 ± 0.1

^aEnzymatic activity of HNE was monitored during 16 h in the presence of 10 μM inhibitor.