Mechanism of Action

CroFab is a venom-specific Fab fragment of immunoglobulin G (IgG) that works by binding and neutralizing venom toxins, facilitating their redistribution away from target tissues and their elimination from the body.

Animal Studies

CroFab was effective in neutralizing the venoms of 10 clinically important North American crotalid snakes in a murine lethality model (see Table 2) [1]. In addition, preliminary data from experiments in mice using whole IgG from the sheep immunized for CroFab production suggest that CroFab might possess antigenic cross-reactivity against the venoms of some Middle Eastern and North African snakes; however,there are no clinical data available to confirm these findings.

The planned pharmacokinetic study of CroFab was not adequately performed. A limited number of samples were collected from three patients. Based on these data, estimates of elimination half-life were made. The elimination half-life for total Fab ranged from approximately 12 to 23 hours. These limited pharmacokinetic estimates of half-life are augmented by data obtained with an analogous ovine Fab product produced by Protherics Inc. using a similar production process. In that study, 8 healthy subjects were given 1 mg of intravenous digoxin followed by an approximately equimolar neutralizing dose of 76 mg of digoxin immune Fab (ovine).Total Fab was shown to have a volume of distribution of 0.3 L/kg,a systemic clearance of 32 mL/min (approximately 0.4 mL/min/kg) and an elimination half-life of approximately 15 hours.

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