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Induction of heart valve lesions by small-molecule ALK5 inhibitors

Mark J Anderton1, Howard R Mellor, Alex Bell

  • 1Department of General Toxicology Sciences, AstraZeneca R&D, Mereside, Alderley Park, Macclesfield, Cheshire, United Kingdom.

Toxicologic Pathology
|August 24, 2011
PubMed

Insights

Transforming growth factor-β (TGF-β) inhibitors targeting ALK5 caused heart valve lesions in rats. These findings highlight the critical role of TGF-β/ALK5 signaling in maintaining heart valve integrity.

Area of Science:

  • Cardiovascular Biology
  • Pharmacology
  • Toxicology

Background:

  • Aberrant transforming growth factor-β (TGF-β) signaling is linked to human diseases.
  • The role of TGF-β signaling via ALK5 in adult heart function is not well understood.
  • ALK5 inhibitors are being explored as potential therapeutics.

Purpose of the Study:

  • To investigate the preclinical toxicology of ALK5 inhibitors.
  • To determine the effects of ALK5 inhibitors on heart valve integrity in adult rats.

Main Methods:

  • Ten-week-old female Han Wistar rats were administered oral ALK5 inhibitors for 3-7 days.
  • Histopathological examination of heart valves and joints was performed.
  • Immunohistochemical analysis of ALK5 expression in rat hearts was conducted.

Main Results:

  • Both ALK5 inhibitors induced histopathologic heart valve lesions (hemorrhage, inflammation, degeneration, proliferation) in all treated rats.
  • Pathology affected all four heart valves across all tested doses.
  • ALk5 expression was detected in heart valves but not myocardium; protein levels remained unchanged.
  • Physeal dysplasia was observed in the femoro-tibial joint, consistent with known ALK5 inhibitor effects.

Conclusions:

  • TGF-β signaling via ALK5 is crucial for maintaining heart valve integrity.
  • ALK5 inhibitors can induce significant heart valve pathology.
  • These findings have implications for the therapeutic development of ALK5 inhibitors.

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