The FDA has requested the withdrawal of avacopan (Tavneos), an oral C5a receptor 1 (C5aR1) antagonist, according to a case report reviewing its uncertain future. ChemoCentryx originally discovered the molecule, which received approval in 2021 for ANCA-associated vasculitis. Following Amgen’s $3.7 billion acquisition of ChemoCentryx, avacopan’s status has become a watch item for complement-modulating vasculitis therapies. For investors and clinicians, the development raises immediate questions about label, post-market obligations, and downstream treatment continuity. The case also spotlights how post-approval compliance and benefit-risk reassessments can materially reshape commercial pipelines after acquisitions.