Table 3.

Enzyme Inhibitors

Drugs	Tpye	Clinical Outcomes
AZD9668	NE inhibitor	ClinicalTrials.gov NCT01054170 (After 12 weeks of treatment with 60 mg dose of AZD9668, not found of that CT airway structure were improved in COPD patients) ClinicalTrials.gov, NCT01023516 (AZD9668 three months treatment, no significant improvement in lung function found in COPD patients)
AZD1236	MMP-9, MMP-12 inhibitors	6 weeks of AZD1236 in COPD patients, had not found any valuable clinical outcomes81
RPL554	PED3/4 inhibitors	ClinicalTrials.gov, NCT02542254, NCT03028142 (Combined with that standard bronchodilators, it improves peak FEV1 in COPD patients)
Roflumilast	PED4 inhibitor	ClinicalTrials.gov, NCT00313209, NCT00424268 (Can improve lung function in COPD patients, but has the side effect of headache)