Background: In patients with Hodgkin lymphoma (HL), serum concentrations of thymus and activation-regulated chemokine (TARC) and other cytokines may have prognostic significance in both the front-line and salvage therapy settings. The potential utility of TARC to predict relapse or progression of HL following autologous hematopoietic cell transplant (AHCT) is unknown. AETHERA (NCT01100502) is a phase 3, randomized, placebo-controlled trial that demonstrated improved progression-free survival (PFS) in patients with high risk HL who received post-AHCT consolidation treatment with brentuximab vedotin (BV) (hazard ratio [HR]=0.57, P=0.001), and an acceptable safety profile. Methods: In this exploratory analysis, we measured baseline serum TARC levels in patients enrolled in AETHERA, and evaluated impact of TARC on outcomes after AHCT with or without BV consolidation therapy. Additional serum biomarkers under analysis include sCD30, sCD163, IL-6, sIL-2R, and sCD68. Descriptive statistics were used to characterize baseline TARC concentrations as a function of baseline clinical characteristics, and Kaplan-Meier analysis was used to assess PFS over 24 months of follow-up. Results: Among 329 patients enrolled, 312 (156 BV and 156 placebo) had available serum samples collected between days 28-45 post-AHCT. The median (range) baseline TARC concentration was 472 (18-18,092) pg/mL, and was similar among patients in the BV (481 [18-18,092] pg/mL) and placebo (446 [43-9,756] pg/mL) arms. Median TARC levels were higher among patients with (vs without) established risk factors for progression; these included B symptoms (537 vs 414 pg/mL), extranodal involvement (501 vs 450 pg/mL), FDG-avid PET status (543 vs 433 pg/mL), and incomplete response to salvage therapy (532 [stable disease] vs 474 [partial remission] vs 404 [complete remission] pg/mL, respectively). The median TARC level was also higher among patients with ≥2 risk factors vs those with 1 risk factor (487 vs 410 pg/mL). PFS at 12 months decreased progressively with increasing TARC among patients who received placebo, but not among those who received BV consolidation (Figure). PFS at 24 months was more similar across TARC levels within each treatment arm. Conclusions: Overall, these data suggest that serum TARC may help to identify HL patients at increased risk of disease progression following AHCT.