A Comparison of Crotalinae Equine Immune F(ab)2 Antivenom (Anavip) and Crotalidae Polyvalent Immune Fab,

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

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.

Study Overview

• Status: Completed
• Conditions: Blood Coagulation Disorders; Snake Bite
• Intervention / Treatment: Biological: Anavip; Biological: CroFab

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Actual): 12
• Phase: Phase 2

Contacts and Locations

Study Locations

• United States
  • Arizona
    • Tucson, Arizona, United States, 85724
      • Tucson snakebite investigational site

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 70 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• men and women 18 to 70 years of age
• presenting for emergency treatment of pit viper bite
• informed consent document read and signed by subject

Exclusion Criteria:

• allergy to horse serum, sheep serum, or papaya
• current use of any antivenom, or use within the last month
• current participation in a clinical drug study, or participation within the last month
• pregnancy or breast-feeding
• underlying medical conditions that significantly alter blood coagulation: thrombocytopenia, hemophilia, familial dysfibrinogenemia, leukemia, recent ingestion of superwarfarin compounds (rat poison)
• use of any medication expected to affect platelet count, coagulation factors, or fibrinogen: chemotherapeutic agents, warfarin, heparin, aspirin
• No clinical indications of snake bite envenomation

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Anavip; The initial dose of study drug was administered in a total volume of 500 mL (initial doses only) IV over 30 minutes for Anavip	Biological: 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 Names: 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.	Biological: CroFab; CroFab, 5 vials Intravenous (IV) every 2 hours until initial control has been achieved; then 3 maintenance doses of 2 vials every 6 hrs

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Detection of Plasma Venom Levels During the Post Acute Treatment Period.	Follow up after Maintenance doses were completed. Two Weeks.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
>50,000 Platelets/mm3	Thrombocytopenia during follow up period. Two weeks	Follow up after maintenance dose

Collaborators and Investigators

• Sponsor: Instituto Bioclon S.A. de C.V.
• Collaborators: University of Arizona
• Investigators: 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

Study record dates

Study Major Dates

• Study Start: January 1, 2005
• Primary Completion (Actual): August 1, 2006
• Study Completion (Actual): February 1, 2007

Study Registration Dates

• First Submitted: November 6, 2008
• First Submitted That Met QC Criteria: March 23, 2009
• First Posted (Estimate): March 24, 2009

Study Record Updates

• Last Update Posted (Estimate): April 18, 2016
• Last Update Submitted That Met QC Criteria: March 18, 2016
• Last Verified: March 1, 2016

More Information

Terms related to this study

• Keywords: Snake Bite; Venom and antivenom kinetics
• Additional Relevant MeSH Terms: Chemically-Induced Disorders; Cardiovascular Diseases; Vascular Diseases; Wounds and Injuries; Hematologic Diseases; Hemorrhagic Disorders; Poisoning; Bites and Stings; Hemostatic Disorders; Blood Coagulation Disorders; Snake Bites; Physiological Effects of Drugs; Immunologic Factors; Antivenins
• Other Study ID Numbers: AN-03/02 (Other Identifier: Bioclon)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: Undecided