Hartmut Bhatt

Hartmut Bhatt has contributed to the analytical and clinical validation of PD-L1 as a predictive biomarker for checkpoint immunotherapy response, examining concordance and discordance among the major PD-L1 IHC assays used as companion diagnostics for pembrolizumab, nivolumab, atezolizumab, and durvalumab. His research has characterized how different PD-L1 scoring systems including tumor proportion score, combined positive score, and immune cell score capture different aspects of PD-L1 expression and their differential correlation with IO outcomes across tumor types. He has studied the analytical challenges of PD-L1 biomarker testing including tissue heterogeneity, assay variability, biopsy site selection, and temporal dynamics during treatment, and their implications for clinical decision-making. His work has contributed to harmonization efforts for PD-L1 testing and understanding the biological meaning of PD-L1 expression patterns in diverse tumor microenvironments.