Biomarker
A measurable biological indicator used to assess a disease state, predict treatment response, or monitor drug effects. Key biomarkers for peptide therapeutics include HbA1c (diabetes), IGF-1 (growth hormone activity), calcitonin (thyroid C-cell monitoring), and NT-proBNP (heart failure).
Technical Context
FDA/NIH BEST (Biomarkers, EndpointS, and other Tools) resource classifies biomarkers: diagnostic (identifying disease — HbA1c ≥6.5% for diabetes), prognostic (predicting disease outcome regardless of treatment — NT-proBNP in heart failure), predictive (predicting response to specific treatment — Ga-68 DOTATATE uptake predicting Lu-177 PRRT response), pharmacodynamic (measuring drug effect — HbA1c change reflecting GLP-1 RA glycaemic effect), safety (monitoring adverse effects — calcitonin for C-cell tumour surveillance during GLP-1 RA therapy), and monitoring (serial measurement detecting disease change — IGF-1 during GH or somatostatin analogue therapy). Biomarker qualification by regulatory agencies (FDA Biomarker Qualification Program, EMA qualification advice) validates specific contexts of use. For peptide drug development, validated biomarkers can serve as surrogate endpoints, potentially accelerating development timelines through earlier efficacy assessment.