Radiation and Chemical Program Research for Multi-Utility and Repurposed Countermeasures: A US Department of Health and Human Services Agencies Perspective.

Although chemical and radiological agents cause toxicity through different mechanisms, the multiorgan injuries caused by these threats share similarities that convene on the level of basic biological responses. This publication will discuss these areas of convergence and explore "multi-utility" approaches that could be leveraged to address common injury mechanisms underlying actions of chemical and radiological agents in a threat-agnostic manner. In addition, we will provide an overview of the current state of radiological and chemical threat research, discuss the US Government's efforts toward medical preparedness, and identify potential areas for collaboration geared toward enhancing preparedness and response against radiological and chemical threats. We also will discuss previous regulatory experience to provide insight on how to navigate regulatory paths for US Food and Drug Administration (FDA) approval/licensure/clearance for products addressing chemical or radiological/nuclear threats. This publication follows a 2022 trans-agency meeting titled, "Overlapping Science in Radiation and Sulfur Mustard Exposures of Skin and Lung: Consideration of Models, Mechanisms, Organ Systems, and Medical Countermeasures," sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), a part of the National Institutes of Health (NIH). Discussions from this meeting explored the overlapping nature of radiation and chemical injury and spurred increased interest in how preparedness for one threat leads to preparedness for the other. Herein, subject matter experts from the NIAID and the Biomedical Advanced Research and Development Authority (BARDA), a part of the Administration for Strategic Preparedness and Response (ASPR), summarize the knowledge gained from recently funded biomedical research, as well as insights from the 2022 meeting. These topics include identification of common areas for collaboration, potential use of biomarkers of injury to identify injuries caused by both hazards, and common and widely available treatments that could treat damage caused by radiological or chemical threats.

Systemic Bioavailability of Sublingual Atropine Ophthalmic Solution: a Phase I Study in Healthy Volunteers with Implications for Use as a Contingency Medical Countermeasure.

INTRODUCTION: Atropine sulfate is an FDA-approved medical countermeasure (MCM) for the treatment of organophosphorus nerve agent and organophosphate pesticide toxicity. Sufficient MCM supplies must be available in an incident involving a mass human exposure either from an accidental chemical release or a terrorist attack. METHODS: We performed a randomized, 3-sequence, 3-period phase I crossover study to assess the bioavailability and pharmacokinetics (PK) of a single dose (0.5 mg and 1.0 mg) of 1% ophthalmic atropine sulfate solution administered sublingually to 15 healthy adult volunteers. The primary endpoint was evaluation of the bioavailability of each of the two sublingual doses against a 1.0 mg reference intravenous (IV) atropine dose. Secondary endpoints included the safety and tolerability (xerostomia scale) of atropine sulfate administered sublingually. RESULTS: Sublingual atropine was safe (no severe AEs or SAEs were reported with either dose) and well tolerated, with a single subject reaching maximum xerostomia on a single dosing day. The geometric mean AUC∞ was 286.40, 493.81, and 816.47 min*ng/mL for the 0.5 mg and 1.0 mg sublingual doses, and the 1.0 mg IV dose, respectively. Compared to IV administration, the 1.0 mg sublingual dose produced 0.60 (90% CI: 0.55-0.66) of the overall concentration of atropine over time (AUC∞). CONCLUSION: Sublingual atropine sulfate 1% ophthalmic solution may be an alternative formulation and route of administration combination which expands the capacity and dosing options of atropine as a nerve agent MCM.

A delayed treatment model for the evaluation of scopolamine for VX nerve agent intoxication.

Most research on medical countermeasures for nerve agent exposure assumes a military scenario, in which (autoinjector) treatment is envisaged to be available immediately. In a civilian setting however, treatment is delayed until arrival of first-aid responders. This may significantly affect treatment efficacy and the requirements for secondary intensive care. The aim of the current study was to develop a guinea pig model to evaluate the efficacy of delayed treatment following nerve agent exposure. We identified a trigger-to-treat based on a progressive stage of the toxidrome following VX exposure, which was associated with the subsiding of clonic movements. This paradigm resulted in treatment consistently being administered between 15 and 25 min post-exposure. Using the model, we investigated the potential for the anticholinergic scopolamine to act as a delayed treatment either as a standalone treatment, or as an adjunct to delayed treatment with Standard of Care (SOC), containing atropine, 2-PAM, and midazolam. The study provides a framework for a small animal model for evaluating the efficacy of treatment administered at a specific stage of the toxidrome, when immediate treatment is absent. As an adjunct, scopolamine treatment did not result in improved survival, but did show a beneficial effect on recovery, in terms of general posture. As a standalone treatment, scopolamine showed a significant, dose-responsive, beneficial effect on survival and recovery. These promising results warrant additional studies to investigate which observed physiological improvements are relevant for the recovery process and residual injury.

The pharmacokinetics of ketamine following intramuscular injection to F344 rats.

Ketamine is a glutamate N-methyl-D-aspartate receptor antagonist that is a rapid-acting dissociative anesthetic. It has been proposed as an adjuvant treatment along with other drugs (atropine, midazolam, pralidoxime) used in the current standard of care (SOC) for organophosphate and nerve agent exposures. Ketamine is a pharmaceutical agent that is readily available to most clinicians in emergency departments and possesses a broad therapeutic index with well-characterized effects in humans. The objective of this study was to determine the pharmacokinetic profile of ketamine and its active metabolite, norketamine, in F344 rats following single or repeated intramuscular administrations of subanesthetic levels (7.5 mg/kg or 30 mg/kg) of ketamine with or without the SOC. Following administration, plasma and brain tissues were collected and analyzed using a liquid chromatography-mass spectrometry method to quantitate ketamine and norketamine. Following sample analysis, the pharmacokinetics were determined using non-compartmental analysis. The addition of the current SOC had a minimal impact on the pharmacokinetics of ketamine following intramuscular administration and repeated dosing at 7.5 mg/kg every 90 minutes allows for sustained plasma concentrations above 100 ng/mL. The pharmacokinetics of ketamine with and without the SOC in rats supports further investigation of the efficacy of ketamine co-administration with the SOC following nerve agent exposure in animal models.

Addition of ketamine to standard-of-care countermeasures for acute organophosphate poisoning improves neurobiological outcomes.

Rats poisoned with sarin enter into ahyper-cholinergic crisis characterized by excessive salivation, respiratory distress, tremors, seizures, and death. Through the use of rescue medications and an anticonvulsant, death can be avoided in many animals, with the long-term consequences of poisoning partly ameliorated, especially when countermeasures are made available immediately after exposure. However, when anticonvulsant measures are delayed by as little as 30 min, clinical, neurological, cognitive, and psychiatric abnormalities may persist long after the initial exposure. This study sought to determine if the addition of the NMDA receptor antagonist Ketamine to human standard-of-care countermeasures consisting of two rescue medications (2-PAM and atropine) and an anti-convulsant (Midazolam), would afford protection against persistent neurobiological compromise. Rats were exposed to sarin (105 µg/kg via subcutaneous injection), and treated 1 min later with 2-PAM and Atropine Methyl Nitrate (IM) to minimize mortality. One of four anti-convulsant protocols was then initiated at 50 min postsarin:Midazolam alone (MDZ, a single injection (IM) at 0.66 mg/kg); Ketamine alone (KET, a series of five injections (IM) of Ketamine at 7.5 mg/kg, 90 min apart); Midazolam + low dose Ketamine (MDZ + lowKET, a single injection of Midazolam (IM) at 0.66 mg/kg, plus five sequential doses of ketamine (IM) at 2.5 mg/kg, starting at the time of Midazolam dosing and then 90 min apart); Midazolam + high dose Ketamine (MDZ + highKET, a single injection of Midazolam (IM) at 0.66 mg/kg, plus five sequential injections of 7.5 mg/kg Ketamine (IM), starting at the time of Midazolam dosing and then 90 min apart). Animals were preassigned to groups culled at post-exposure Days 1, 7 or 30, for histopathology. For all surviving animals, EEG activity was monitored through skull electrodes for 24-h beginning immediately after sarin exposure. Surviving animals also underwent 24-h EEG monitoring on Days 6, 13, and/or 29, post-sarin. Memory assessment using the Morris Water Maze was performed on Days 1, 4, 7, 14 and 30. Following sarin exposure, 85% of surviving animals demonstrated status epilepticus within 20 min. Each of the anti-convulsant protocols was sufficient to stop convulsions within 1 h of anti-convulsant administration, but all of the animals still showed signs of electrographic status for an additional 2-12 h, without substantial differentiation between treatment groups. However, for post-sarin hours 13-24, the MDZ + highKET group showed significantly less severe EEG abnormalities than the MDZ and KET groups (Mood's Median Test, p < 0.005). At one month post-exposure, 90% of animals that had received Midazolam alone still showed evidence of some epileptiform activity. In contrast, 90% of animals that had received Midazolam + high dose Ketamine combination therapy had EEG profiles that were within normal limits. This difference in EEG outcomes was highly significant (Mood's Median Test, p < 0.001). Likewise, on the water maze, the majority of animals that had received Midazolam combined with either high or low dose Ketamine therapy returned to near baseline levels of mnemonic performance within 2 weeks, whereas the majority of the animals that had received midazolam alone or ketamine alone demonstrated persistent and significant memory impairments even at one month postexposure (Mood's Median Test, p < 0.005). With respect to neuronal necrosis, animals in the MDZ + highKET group showed significantly less overall damage than animals in other treatment groups (Mood's Median Test, p < 0.001). Of special note were findings in the hippocampus, where only 12% of animals in the MDZ + highKET group showed evidence of necrosis on H&E staining, whereas 100% of animals in the KET group, 70% of animals in the MDZ group, and 40% of animals in the MDZ + lowKET group showed evidence of hippocampal necrosis. Overall, the data demonstrate that Ketamine augmentation of an atropine, 2PAM, and Midazolam standard-ofcare for sarin exposure provides clinically-relevant additional protection against the negative neurobiological consequences of sarin, even when initiation of the anti-convulsant countermeasures is delayed by 50 min.