Safety and Efficacy of ABX-101 in Participants Aged 18 to 50 Years of Age With Moderate to Severe Traumatic Brain Injury

Inclusion Criteria: * Written informed consent from patient, patient's legal guardian or legal representative, or deferred consent procedure, according to local requirements * 18 - 50 years of age, inclusive * Expected to survive more than 24 hours after admission * Clearly defined time of injury no more than 12 hours before administration of study drug/placebo o Subjects stratified 1:1 (in each arm) by treatment administered 0-12 hrs * TBI with Glasgow Coma Score (GCS) 4-12 requiring intracranial pressure (ICP) monitoring according to the assessment of the treating physician o Subjects stratified 1:1 (in each arm) by GCS 4-8 and GCS 9-12 * Catheter placement (intraventricular or intraparenchymal, only) for monitoring and management of increased ICP * \[Brain computed tomography (CT) showing intracranial parenchymal abnormality and hemodynamically stable\] Exclusion Criteria: * Penetrating head injury (e.g. missile, stab wound) * Concurrent, but not pre-existing, spinal cord injury * Not expected to survive more than 24 hours after admission * Pregnant, or a positive pregnancy test * Coma due to an exclusive epidural hematoma (lucid interval and absence of structural brain damage on CT scan) * Patient pupils are unresponsive (dilation) in both eyes * The subject has a neurodegenerative disease or other neurological disorder including dementia, Parkinson's disease, multiple sclerosis, seizure disorder, or brain tumors. * Coma suspected to be primarily due to other causes than head injury (e.g. drug overdose intoxication, drowning/near drowning * Known or CT scan evidence of pre-existing major cerebral damage * Any severe concomitant condition (cancer; hematologic, renal, hepatic, coronary disease; major psychiatric disorder; alcohol or drug abuse), that can be ascertained at admission * Known to have received an experimental drug within 4 weeks prior to current injury * Patients who cannot be monitored with regard to their recovery (GOS-E and QOLIBRI)