A Comparison of Crotalinae Equine Immune F(ab)2 Antivenom (Anavip) and Crotalidae Polyvalent Immune Fab,
This phase II study was a prospective, randomized, open-label, multi-center study in the United States, involving patients from 18 to 70 years of age, comparing Anavip (Antivenin Crotalinae [pit viper] equine immune F(ab)2; Instituto Bioclon, Mexico City, Mexico) against CroFab (Protherics Inc., Nashville, Tennessee), the only currently approved product for treatment of Crotalinae (pit viper) envenomation in the US.
The study was designed to evaluate the hypothesis that lasting correction of snakebite induced thrombocytopenia and hypofibrinogenemia are possible following correction with F(ab)2 antivenom, by analyzing in detail the relationships among platelet count, fibrinogen, venom levels, and antivenom levels in subjects presenting with thrombocytopenia following crotaline viper envenomation. In the study we expected to see a fall in platelet count following Fab treatment, commensurate with that reported in the past. We hypothesized that following F(ab)2 treatment there would be a slower drop in post-treatment platelet counts, with a relatively higher platelet count at any given point in the follow-up period. We further hypothesized that an initial rise and later fall in platelet count would correspond with rise and fall in antivenom levels, and would be mirrored by concurrent drop and rise in levels of unbound circulating venom.
Blood Coagulation Disorders
|Study Design:||Allocation: Randomized
Endpoint Classification: Safety/Efficacy Study
Intervention Model: Parallel Assignment
Masking: Open Label
Primary Purpose: Treatment
|Official Title:||A Comparison of Anavip and CroFab in the Treatment of Subjects With Crotalinae (Pit Viper) Envenomation: A Randomized, Prospective, Open-Label, Controlled, Comparative, Multicenter Study|
- Detection of Plasma Venom Levels During the Post Acute Treatment Period. [ Time Frame: Follow up after Maintenance doses were completed. Two Weeks. ] [ Designated as safety issue: Yes ]
- >50,000 Platelets/mm3 [ Time Frame: Follow up after maintenance dose ] [ Designated as safety issue: Yes ]Thrombocytopenia during follow up period. Two weeks
|Study Start Date:||January 2005|
|Study Completion Date:||February 2007|
|Primary Completion Date:||August 2006 (Final data collection date for primary outcome measure)|
The initial dose of study drug was administered in a total volume of 500 mL (initial doses only) IV over 30 minutes for Anavip
Anavip, 10 vials Intravenous (IV) every 2 hours until initial control has been achieved; then 3 maintenance doses of 4 vials every 6 hrs
Other Name: Antivenin Crotalinae (pit viper) equine immune F(ab)2
Active Comparator: CroFab
The initial dose of study drug was administered in a total volume of 500 mL (initial doses only) IV over 60 minutes for CroFab, or as permitted by IV access.
CroFab, 5 vials Intravenous (IV) every 2 hours until initial control has been achieved; then 3 maintenance doses of 2 vials every 6 hrs
The overall objective of this Phase 2 open-label comparative study was to demonstrate that the F(ab)2 antivenom Anavip has significantly longer plasma persistence than does Fab, and that this is associated with a slower rise in venom levels and slower decline in platelet count and fibrinogen following hospital discharge of envenomated subjects. The effectiveness of F(ab)2 in preventing the recurrence of coagulopathies after the subject's discharge from hospital will indicate that, inherently, F(ab)2 antivenom has an improved safety profile relative to the Fab antivenom CroFab in treating envenomation by crotaline vipers.
Each subject was assessed for quantitative serum venom levels. Relatively few historical data exist to support the use of venom levels as a surrogate endpoint in envenomation. However, changes in venom levels have been correlated with coagulopathic effects, during both the acute phase of venom toxicity and the post treatment period of recurrent venom effect. Validation of this surrogate endpoint via correlation of venom effect with platelet count and fibrinogen level in this phase II study is intended to support future studies.
The secondary endpoints were the determination of coagulation abnormalities during the follow up period.
Please refer to this study by its ClinicalTrials.gov identifier: NCT00868309
|United States, Arizona|
|Tucson snakebite investigational site|
|Tucson, Arizona, United States, 85724|
|Study Director:||Walter García, MD||Instituto Bioclon|
|Principal Investigator:||Leslie Boyer, MD||University of Arizona|
|Principal Investigator:||Alejandro Alagón, MD, PhD||Instituto de Biotecnología UNAM|