Tachykinin antagonists and the airways

Area of Science:

• Pulmonary Medicine
• Neuroscience
• Pharmacology

Background:

• Substance P (SP) and neurokinin A (NKA), tachykinins found in human airway nerves, are increasingly linked to asthma.
• Elevated SP levels are observed in asthmatic airways, suggesting a role in the condition's pathophysiology.
• Asthmatics exhibit heightened sensitivity to the bronchoconstrictive effects of SP and NKA compared to healthy individuals.

Purpose of the Study:

• To review the evidence for SP and NKA in human airways and their role in asthma.
• To explore the involvement of tachykinin receptors (NK1, NK2) in airway functions and inflammation.
• To assess the efficacy of current tachykinin receptor antagonists in clinical trials for asthma.

Main Methods:

• Review of existing literature on SP, NKA, and their receptors in human airways.
• Analysis of studies using autopsy tissue, bronchoalveolar lavage fluid, and sputum.
• Examination of data from early clinical trials of tachykinin receptor antagonists (FK224, CP99994).

Main Results:

• SP and NKA are confirmed as potent bronchoconstrictors, with asthmatics showing increased sensitivity.
• Neutral endopeptidase, the primary enzyme for tachykinin degradation, is present in airways.
• NK1 and NK2 receptors mediate bronchoconstriction, mucus secretion, vasodilation, and inflammatory cell activity; however, initial trials with antagonists FK224 and CP99994 were negative.

Conclusions:

• Tachykinins SP and NKA play significant roles in airway function and inflammation, particularly in asthma.
• While NK1 and NK2 receptors are validated targets, current antagonists have shown limited success in early clinical trials.
• Further research is needed to determine optimal dosing and efficacy of tachykinin receptor antagonists for managing asthma.