VCAM1 and progressive multifocal leukoencephalopathy: In addition, Natalizumab, which targets the binding of α4β1 integrin to VCAM-1 and α4β7 integrin to MAdCAM-1, has a high clinical response rate, but the risk of progressive multifocal leukoencephalopathy,[112] a serious and fatal adverse effect, has led to the gradual withdrawal of natalizumab from the market.