Latrodectism Clinical Trial
Official title:
A Phase III Multicenter Clinical Trial of Analatro® [Antivenin Latrodectus (Black Widow) Equine Immune F(ab)2] in Patients With Systemic Latrodectism
The purpose of this study is to test the efficacy and safety of a new antivenom called Analatro® for treating black widow spider bites in patients who present to a hospital emergency room within 24 hours of symptom onset. This study will be a phase III, multi-center, double-blind, randomized controlled study that takes place in emergency departments. The primary aim of this study is to determine the proportion of patients in which pain control was not achieved by 48 hours post treatment. Secondary aims are as follows: 1) a reduction in pain intensity at the end of the treatment phase compared to baseline; 2) the proportion of patients with a clinically significant decrease in pain intensity at 30 minutes post-treatment; 3) the proportion of patients in which drug-related adverse events occurred; and 4) to determine if serious, drug-related adverse events in Analatro-treated patients occurred at a rate greater than one in 10 (10%).
Instituto Bioclon S.A. de C.V. has developed Analatro®, an antibody fragment (Fab2)
containing widow spider (Latrodectus) antivenom, and proposes to conduct a clinical trial in
hospital emergency departments to assess the efficacy and safety of this product in patients
with moderate to severe pain associated with Latrodectus envenomation (latrodectism). The
primary objectives of this Phase III, multi-center, double-blind, controlled study are as
follows:
To determine the efficacy of Analatro compared to control for the treatment of latrodectism
as measured by the proportion of patients in whom pain control is not achieved (e.g.,
treatment failure)
To further characterize the safety profile of Analatro, including comparison of the rate of
drug-related adverse events to control for the treatment of latrodectism
The flow of study procedures are illustrated in the chart on the following page. All patients
who consent to participate will be given a visual analog scale (VAS, 0=no pain to 100mm=worst
possible pain) for assessing pain intensity. Patients that meet all study enrollment
requirements, including a minimum age of 10 years, a clinical diagnosis of latrodectism and a
VAS pain score of ≥40 mm (moderate to severe pain) will be randomly assigned to be treated
with Analatro or control. A screening phase will be completed, during which time preliminary
procedures will be performed by the investigator (medical history, physical exam, and
pregnancy test as applicable) and two doses of Analatro or two doses of saline control will
be prepared. Fentanyl may be administered intravenously as needed for pain relief during the
screening phase at a dosage not to exceed 1.5 µg/kg/hr. At the end of the screening phase,
baseline measurements (vital signs, VAS pain score) will be performed. Patients must have a
baseline VAS score ≥40 mm to receive study medication.
Eligible patients will begin a 2.5 hour treatment phase. Dose 1 of study medication (50 mL)
will be infused intravenously over 10 minutes. Thirty minutes after the start of Dose 1, pain
intensity will be assessed (VAS2), vital signs will be recorded (VS2), and a blood sample
collected (B2). Clinical improvement in this study will be defined as a VAS score that is at
least 13mm less than the baseline VAS score (VAS1). Patients that fail to show clinical
improvement at 30 minutes will receive Dose 2 of study medication (Dose 2 will be identical
to Dose 1). Patients showing clinical improvement will not receive Dose 2.
Thirty minutes after VAS2 (or after the start of Dose 2, if applicable), VAS3 will be
administered, vital signs (VS3) will be recorded, and a blood sample (B3) will be collected.
If the patient has not clinically improved relative to baseline, the patient will be deemed a
treatment failure; the treatment phase will be discontinued, and the patient will be treated
in accordance with standard of care by the investigator and/or treating physician. Patients
that have clinically improved will remain in the treatment arm.
The remaining 1.5 hours of the treatment arm will consist of serial assessments of pain
intensity (VAS4, 5 and 6), vital signs (VS4, 5 and 6), and collection of one blood sample
(B4, 5 and 6) every 30 minutes. After each VAS, the patient must continue to show clinical
improvement relative to baseline to remain in the treatment arm. Otherwise, the patient will
exit the treatment phase and be treated in accordance with standard of care. No analgesics
will be allowed during the treatment phase to eliminate the potential confounding effect of
pain medication on assessing the effectiveness of the study medication on clinical
improvement. Routine decision points for treatment failure (every thirty minutes) will
promote accurate identification of treatment failures without compromising timely provision
of pain medication in absence of clinical improvement.
All patients will be closely monitored for adverse events during Dose 1 of treatment until
the time of discharge from the emergency department. Follow-up for possible adverse events
and recurring/residual symptoms will be conducted by telephone on Days 2, 10, and 17 after
discharge from the emergency department.
Treatment failure will be defined as (1) early exit from the treatment phase due to absence
of clinical improvement relative to baseline and/or (2) patient requires prescription pain
medication or Antivenin Latrodectus Mactans (Merck) for pain associated with the study
condition being treated at any time after the treatment phase up to 48 hours after the time
of discharge from the emergency department. To improve accurate identification of treatment
failure after discharge, no preventative pain medication will be administered or prescribed
to patients that successfully complete the treatment phase. Patients will be encouraged to
call the investigator or return to the emergency department, if necessary, for proper
evaluation and treatment.
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