This phase 1/2 multisite study (ClinicalTrials.gov: NCT03598608) will enroll patients with PD-1/PD-L1 inhibitor–naive cHL (cohort 1), PD-1/PD-L1 inhibitor–refractory R/R cHL (cohort 2), R/R DLBCL (cohort 3), and R/R indolent B-cell lymphoma (cohort 4). Here, CD274 is linked to diffuse large B-cell lymphoma.