ACE Inhibitor - History

History

The first step in the development of ACE inhibitors was the discovery of ACE in plasma by Leonard T. Skeggs and his colleagues in 1956. Brazilian scientist Sergio Ferreira reported a bradykinin-potentiating factor (BPF) present in the venom of Bothrops jararaca, a South American pit viper, in 1965. Ferreira then went to John Vane's laboratory as a postdoctoral fellow with his already-isolated BPF. The conversion of the inactive angiotensin I to the potent angiotensin II was thought to take place in the plasma. However, in 1967, Kevin K. F. Ng and John R. Vane showed plasma ACE is too slow to account for the conversion of angiotensin I to angiotensin II in vivo. Subsequent investigation showed rapid conversion occurs during its passage through the pulmonary circulation.

Bradykinin is rapidly inactivated in the circulating blood, and it disappears completely in a single pass through the pulmonary circulation. Angiotensin I also disappears in the pulmonary circulation due to its conversion to angiotensin II. Furthermore, angiotensin II passes through the lungs without any loss. The inactivation of bradykinin and the conversion of angiotensin I to angiotensin II in the lungs was thought to be caused by the same enzyme. In 1970, Ng and Vane, using BPF provided by Sérgio Henrique Ferreira, showed the conversion is inhibited during its passage through the pulmonary circulation.

BPFs are members of a family of peptides whose potentiating action is linked to inhibition of bradykinin by ACE. Molecular analysis of BPF yielded a nonapeptide BPF teprotide (SQ 20,881), which showed the greatest ACE inhibition potency and hypotensive effect in vivo. Teprotide had limited clinical value due to its peptide nature and lack of activity when given orally. In the early 1970s, knowledge of the structure-activity relationship required for inhibition of ACE was growing. David Cushman, Miguel Ondetti and colleagues used peptide analogues to study the structure of ACE, using carboxypeptidase A as a model. Their discoveries led to the development of captopril, the first orally-active ACE inhibitor, in 1975.

Captopril was approved by the United States Food and Drug Administration in 1981. The first nonsulfhydryl-containing ACE inhibitor, enalapril, was marketed two years later. At least twelve other ACE inhibitors have since been marketed.

In 1991, Japanese scientists created the first milk-based ACE inhibitor, in the form of a fermented milk drink, using specific cultures to liberate the tripeptide isoleucine-proline-proline (IPP) from the dairy protein. Valine-proline-proline (VPP) is also liberated in this process—another milk tripeptide with a very similar chemical structure to IPP. Together, these peptides are now often referred to as lactotripeptides. In 1996, the first human study confirmed the blood pressure-lowering effect of IPP in fermented milk. Although twice the amount of VPP is needed to achieve the same ACE-inhibiting activity as the originally discovered IPP, VPP also is assumed to add to the total blood pressure lowering effect. Since the first lactotripeptides discovery, more than 20 human clinical trials have been conducted in many different countries.