Marked Asymptomatic Creatine Kinase Elevation With Preserved Renal Function Identified Through Protocol-Driven Monitoring in a Clinical Trial Participant: A Case Report

Elevated creatine kinase (CK) levels may occur in a wide range of clinical conditions including skeletal muscle injury, inflammatory myopathies, medication-associated myotoxicity, rhabdomyolysis, and strenuous physical activity. Distinguishing clinically significant muscle injury from transient physiologic hyperCKemia may be particularly challenging in asymptomatic patients undergoing routine laboratory surveillance. We report the case of a 62-year-old African American male clinical trial participant in whom marked asymptomatic hyperCKemia was identified through protocol-driven safety monitoring during long-term study participation. Serial laboratory assessments identified a marked isolated serum CK elevation (2694 U/L) with preserved creatinine clearance and stable renal function throughout the monitoring period. Approximately three weeks prior to the peak laboratory abnormality, the participant reported intensification of physical exercise activity. Despite marked CK elevation, the participant denied myalgia, muscle weakness, dark urine, decreased urine output, chest pain, palpitations, dyspnea, or constitutional symptoms. Twelve-lead electrocardiography demonstrated normal sinus rhythm with nonspecific low-amplitude T-wave abnormalities without clinically significant arrhythmias or acute ischemic abnormalities. Review of temporal relationships, concomitant medications, available safety data, and the Investigator’s Brochure did not support the investigational product as a likely contributor to the laboratory abnormalities. The participant remained clinically stable with preserved renal function and spontaneous improvement in laboratory abnormalities during continued monitoring. This case highlights the importance of contextual interpretation of marked asymptomatic CK elevation and demonstrates how protocol-driven safety monitoring can facilitate early identification and evaluation of clinically silent laboratory abnormalities in clinical trial participants.