A proportion of patients with exertional angina and symptoms strongly suggestive of coronary artery disease (CAD) show normal coronary angiograms and are designated as having microvascular angina.
Microvascular angina is a type of angina in which no obstructive coronary artery disease is present and myocardial ischemia is a result of coronary microvascular dysfunction attributed to structural and functional abnormalities of the coronary microcirculation. According to experts interviewed by GlobalData, microvascular angina is being increasingly recognised in clinical practice. In the past, these patients were often disregarded since the diagnosis of chronic stable angina was highly related to the presence of atherosclerotic obstructions. As the condition’s pathogenesis remained uncertain, it was labelled as ‘cardiac syndrome X.’ In the last few years, the landscape is shifting with an increasing number of physicians accepting the notion that a dysfunctional microvasculature is the cause of angina in some patients, and an increased awareness among the cardiology community regarding its diagnosis.
Experts further highlighted that a knowledge gap still exists in understanding microvascular syndromes, coronary microvascular dysfunction in particular, and treatment strategies that are particularly targeting the microvascular dysfunction are lacking. There has been a renewed interest, however, among the medical community to elucidate the underlying causes of microvascular angina. Efforts towards understanding the pathophysiological mechanisms underpinning microvascular angina are of paramount importance in the process of developing therapies that optimally treat these patients.
Currently, standard antianginal drugs, such as beta-blockers, calcium channel blockers, and nitrates, offer some relief from symptoms. Despite the availability of these therapies, however, key opinion leaders (KOLs) interviewed by GlobalData highlight that a significant need remains in the current treatment paradigm for additional agents that target the specific heterogeneous pathogenesis of microvascular angina.
Two drugs currently being pursued in late-stage studies in this subset of angina patients across seven major markets (7MM: US, France, Germany, Italy, Spain, UK, Japan) are CLBS16 (formerly CLBS14-CMD), an intracoronary injection of autologous CD34+ cells, in a Phase II trial in the US by Caladrius Biosciences, and zibotentan, an endothelin receptor inhibitor, being investigated in a Phase II trial sponsored by NHS Greater Glasgow and Clyde in the UK.