BRAIN-CELL PENETRATING ANTIBODIES FOR TREATMENT OF PROGRESSIVE MULTIPLE SCLEROSIS - ABSTRACT. CENTRAL NERVOUS SYSTEM (CNS) PHYSICAL INJURIES, INCLUDING BACTERIAL OR VIRAL INFECTION, CAN INDUCE CHRONIC NEUROINFLAMMATION THAT IS BELIEVED TO PERSIST FOR THE LIFETIME OF AN INDIVIDUAL. AMONG THE OTHER INFLAMMATORY EVENTS, IT IS RECOGNIZED THAT BOTH ACUTE AND CHRONIC ACTIVATION OF THE COMPLEMENT PATHWAY PLAYS A ROLE IN THE DEVELOPMENT OF SECONDARY BRAIN INJURIES BY INDUCING NEURONAL CELL LOSS AND SYNAPTIC PRUNING. COMPLEMENT OVER-ACTIVATION IS ALSO FIRMLY IMPLICATED IN THE PATHOLOGY THAT UNDERLIES THE IRREVERSIBLE PROGRESSION OF MULTIPLE SCLEROSIS (MS), A COMMON INFLAMMATORY AND NEURODEGENERATIVE DISEASE OF THE CNS. WE HYPOTHESIZE THAT THERAPEUTIC INHIBITION OF THE COMPLEMENT SYSTEM AND CONCURRENT STIMULATION OF NERVE GROWTH MAY PREVENT CNS TISSUE DAMAGE AND SLOW OR EVEN BLOCK THE PROGRESSION OF MS. CURRENTLY, THE MAIN OBSTACLE FOR DRUG DELIVERY TO THE CNS IS THE PRESENCE OF A SELECTIVELY PERMEABLE BLOOD-BRAIN BARRIER (BBB), LIMITING BLOOD-BORNE PROTEINS' ENTRYINTO THE CNS. TO OVERCOME THIS ISSUE, WE HAVE RECENTLY DEVELOPED SEVERAL POTENT CAMELID-DERIVED NANOBODIES. THE FIRST GROUP OF NANOBODIES CAN INHIBIT COMPLEMENT ACTIVATION, WHEREAS THE SECOND GROUP COMPRISES TYROSINE KINASE RECEPTOR TRKB AGONISTS THAT MIMIC THE ACTION OF BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF), A GROWTH FACTOR IN THE BRAIN THAT PROMOTES NEURONAL SURVIVAL, SYNAPTIC PLASTICITY AND NEUROGENESIS. HERE, WE PROPOSE TO ENGINEER THESE NANOBODIES FURTHER TO FACILITATE THEIR CROSSING OF THE BBB, THEREBY GAINING THE ABILITY TO MORE EFFECTIVELY INHIBIT THE COMPLEMENT CASCADE AND/OR STIMULATE NERVE GROWTH WITHIN THE CNS. DURING PHASE I, BISPECIFIC NANOBODIES WILL BE PRODUCED AND VALIDATED IN IN VITRO CELLULAR FUNCTIONAL ASSAYS. THERAPEUTIC EFFICACY WILL BE FURTHER VALIDATED IN A WELL-CHARACTERIZED MURINE MODEL OF PROGRESSIVE MS, THE THEILER'S MURINE ENCEPHALOMYELITIS VIRUS-INDUCED DEMYELINATING DISEASE (TMEV-IDD). TO THIS END, MICE WILL BE TREATED WITH CONTROL NANOBODIES, A COMPLEMENT INHIBITOR NANOBODY, TRKB AGONISTIC NANOBODY, OR A COMBINATION OF THE LATTER TWO. ONCE THERAPEUTIC EFFICACY IS CONFIRMED IN TMEV-IDD, THE CAMELID-DERIVED NANOBODIES WILL BE HUMANIZED TO REDUCE ANTIGENICITY IN HUMANS. STATISTICALLY SIGNIFICANT IMPROVEMENT IN TREATED MICE MONITORED AS AN IMPACT ON DISABILITY PROGRESSION AND CNS PATHOLOGY WILL BE THE FOUNDATION FOR A PHASE II SUBMISSION. THE GOALS OF PHASE II ARE 1) REVALIDATE THE THERAPEUTIC EFFICACY OF HUMANIZED ANTIBODIES IN MORE EXTENSIVE EXPERIMENTS, INCLUDING A DETAILED ANALYSIS OF THE EFFECT OF SEX, AGE, DOSE-RANGES AND DELAYED TREATMENTS, I.E., LATER THAN 30 DAYS POST-INFECTION, ON DISABILITY PROGRESSION, DISEASE PATHOLOGY AND RECOVERY; 2) TO ESTABLISH MANUFACTURING PROTOCOLS UNDER CURRENT GOOD MANUFACTURING PRACTICE CONDITIONS AND; 3) TO DEFINE THE BIOLOGICAL RESPONSE, PK/PD, DOSE-RANGING AND TOXICOLOGY IN MULTIPLE MODEL ANIMALS, INCLUDING TOXICOLOGY STUDIES IN NON-HUMAN PRIMATES.