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Trial Finds Patients Receiving CroFab® Antivenom Less Likely to Use Opioids for Pain Control

April 29, 2019 Off By BusinessWire

PHILADELPHIA–(BUSINESS WIRE)–BTG plc (LSE: BTG), the global healthcare company, today announced the
publication of a trial, “Antivenom Treatment is Associated with Fewer
Patients Using Opioids after Copperhead Envenomation” in the Western
Journal of Emergency Medicine (WestJEM).

“In a randomized, double-blind, placebo-controlled, clinical trial of
CroFab® for treatment of copperhead snakebite, patients that received
CroFab® were less likely to use opioids for pain control during
recovery,” said Dr. Charles Gerardo, Chief of Emergency Medicine at Duke
University and expert in copperhead snake envenomation. “This is
completely consistent with antivenom’s effect on tissue injury and
improved recovery. No patients reported use of opioids once they had
regained full function. As the CroFab® patients recovered more quickly,
they required a shorter duration of opioids.”

The secondary analysis was performed using data from a randomized
clinical trial designed to determine the effect of CroFab® on limb
injury recovery following mild to moderate copperhead envenomation. The
original trial results were published in the Annals of Emergency
Medicine in 2017 as “The Efficacy of Crotalidae Polyvalent Immune Fab
(Ovine) Antivenom Versus Placebo Plus Optional Rescue Therapy on
Recovery from Copperhead snake Envenomation: A Randomized Double-Blind,
Placebo-Controlled, Clinical Trial.”

“Exposure to opioids as a result of an initial prescription from the
emergency department may contribute to long term opioid abuse and
addiction,” said Dr. Caroline Freiermuth, Associate Professor of
Emergency Medicine at the University of Cincinnati. “Patients who
continue to use opioids for more than five days following an initial
opioid prescription have a higher risk of ongoing opioid use at a year
than those patients who have stopped. When assessing the efficacy of
treatments for painful diseases such as snakebite, we should more
consistently assess the treatment’s impact on opioid use as was done in
this study.”

Seventy-four patients were enrolled in the parent trial. Forty-five
received CroFab®. Twenty-nine received a placebo. A smaller proportion
of patients treated with CroFab® reported opioid use, nearly 41 percent
versus nearly 61 percent of those in the placebo group. The proportion
of patients using opioids remained smaller in the CroFab® group at every
follow-up time point.

The resulting model estimated the odds of using opioids after hospital
discharge among those who received placebo was nearly 6 times that of
those who received CroFab®.

A secondary analysis, “Early Administration of Fab Antivenom Resulted in
Faster Limb Recovery in Copperhead Snake Envenomation Patients,” showing
early treatment with CroFab® led to faster limb recovery was published
in Clinical Toxicology in 2018. Another secondary analysis, “The
Validity, Reliability and Minimal Clinically Important Difference of the
Patient Specific Functional Scale in Snake Envenomation,” was published
in PLOS One this year.

Real world safety data has also been published in two studies, “Acute
Adverse Events Associated with the Administration of Crotalidae
Polyvalent Immune Fab Antivenom within the North American Snakebite
Registry,” and “Incidence of Allergic Reactions to Crotalidae Polyvalent
Immune Fab,” in Clinical Toxicology in 2018. These studies demonstrated
a low rate of adverse reactions (between 1.4 – 2.7%) in patients treated
with CroFab.

Between 5,000 and 9,000 people in the U.S. seek treatment in an
emergency department due to a snakebite each year. There were 2,048
calls to U.S. poison centers in 2016 for copperhead bites. There were
close to another 2,000 calls in which the type of snake was not
identified.

About CroFab®

CroFab® is the only FDA-approved treatment for all North American pit
viper envenomations in adult and pediatric patients. Since 2001, CroFab
has been used to treat more than 50,000 patients. It is developed
through a unique manufacturing process for exceptional quality and
purity. It is derived from Australian sheep, is free of prions and
viruses, and produced exclusively from U.S. snakes. CroFab® has been
proven to halt local effects including edema, ecchymosis, and treat the
source of pain. It has been found to resolve systemic effects such as
nausea, vomiting, dizziness and tachycardia. CroFab® has also been found
to reduce coagulation abnormalities, such as thrombocytopenia,
hyperfibrinogenemia and spontaneous bleeding.

INDICATION

CroFab® is indicated for the management of adults and pediatric patients
with North American crotalid envenomation. The term crotalid is used to
describe the Crotalinae subfamily (formerly known as Crotalidae) of
venomous snakes which includes rattlesnakes, copperheads, and
cottonmouths/water moccasins.

IMPORTANT SAFETY INFORMATION

CONTRAINDICATIONS

Do not administer CroFab® to patients with a known history of
hypersensitivity to any of its components, or to papaya or papain unless
the benefits outweigh the risks and appropriate management for
anaphylactic reactions is readily available.

WARNINGS AND PRECAUTIONS

Coagulopathy: In clinical trials, recurrent coagulopathy (the return of
a coagulation abnormality after it has been successfully treated with
antivenin), characterized by decreased fibrinogen, decreased platelets,
and elevated prothrombin time, occurred in approximately half of the
patients studied; one patient required re-hospitalization and additional
antivenin administration. Recurrent coagulopathy may persist for 1 to 2
weeks or more. Patients who experience coagulopathy due to snakebite
should be monitored for recurrent coagulopathy for up to 1 week or
longer. During this period, the physician should carefully assess the
need for re-treatment with CroFab® and use of any type of anticoagulant
or anti-platelet drug.

Hypersensitivity Reactions: Severe hypersensitivity reactions may occur
with CroFab®. In case of acute hypersensitivity reactions, including
anaphylaxis and anaphylactoid reactions, discontinue infusion and
institute appropriate emergency treatment. Patients allergic to papain,
chymopapain, other papaya extracts, or the pineapple enzyme bromelain
may also have an allergic reaction to CroFab®. Follow-up all patients
for signs and symptoms of delayed allergic reactions or serum sickness
(e.g., rash, fever, myalgia, arthralgia).

ADVERSE REACTIONS

The most common adverse reactions (incidence ≥ 5% of subjects) reported
in the clinical studies were urticaria, rash, nausea, pruritus and back
pain. Adverse reactions involving the skin and appendages (primarily
rash, urticaria, and pruritus) were reported in 12 of the 42 patients.
Two patients had a severe allergic reaction (severe hives and a severe
rash and pruritus) following treatment and one patient discontinued
CroFab® due to an allergic reaction. Recurrent coagulopathy due to
envenomation and requiring additional treatment may occur.

To report suspected adverse reactions, contact 1-877-377-3784 or FDA at
1-800-FDA-1088 or www.fda.gov/medwatch.

Please
see the full Prescribing Information for CroFab.

About BTG Pharmaceuticals.

BTG Pharmaceuticals provides antidotes that counteract the potentially
life-threatening effects associated with exposure or overexposure to
certain toxins. These acute care products are typically used in
emergency rooms and intensive care units to treat patients for whom
there are limited or no existing treatment options. We are dedicated to
delivering quality medicines that make a real difference to patients
through the development, manufacture, and commercialisation of
pharmaceutical products. To learn more about BTG Pharmaceuticals, please
visit: btgplc.com/pharmaceuticals