While promising clinical results have resulted, this combinatorial treatment approach suffers from significant obstacles, including the problematic identification and heterogeneity of PD-L1 expression in patients (11), the limited applicability to patients with PD-L1–positive TNBC (only 20%–42% of cases; refs. 12, 13), and the induction of severe side effects (e.g., neutropenia, peripheral neuropathy, and colitis; refs. 10, 14, 15). The gene discussed is CD274; the disease is colitis.