Vascular leak syndrome (VLS) is the major dose-limiting toxicity of interleukin-2 (IL-2) and of immunotoxin (IT) therapies.

VLS is characterized by an increase in vascular permeability accompanied by extravasation of fluids and proteins resulting in interstitial edema and organ failure.

Manifestations of VLS include fluid retention, increase in body weight, peripheral edema, pleural and pericardial effusions, ascites, anasarca and, in severe form, signs of pulmonary and cardiovascular failure. Symptoms are highly variable among patients and the causes are poorly understood.

VLS restricts the doses of IL-2 and of ITs which can be administered to humans and, in some cases, necessitates the cessation of therapy.

Sources: National Institutes of Health, ScienceDirect