Water-soluble progesterone analogues are effective, injectable treatments in animal models of traumatic brain injury

Effects of Progesterone on Preclinical Animal Models of Traumatic Brain Injury: Systematic Review and Meta-analysis

Since the publication of two phase III clinical trials not supporting the use of progesterone in patients with traumatic brain injury (TBI), several possible explanations have been postulated, including limitations in the analysis of results from preclinical evidence. Therefore, to address this question, a systematic review and meta-analysis was performed to evaluate the effects of progesterone as a neuroprotective agent in preclinical animal models of TBI. A total of 48 studies were included for review: 29 evaluated brain edema, 21 evaluated lesion size, and 0 studies reported the survival rate. In the meta-analysis, it was found that progesterone reduced brain edema (effect size - 1.73 [- 2.02, - 1.44], p < 0.0001) and lesion volume (effect size - 0.40 [- 0.65, - 0.14], p = 0.002). Lack of details in the studies hindered the assessment of risk of bias (through the SYRCLE tool). A funnel plot asymmetry was detected, suggesting a possible publication bias. In conclusion, preclinical studies show that progesterone has an anti-edema effect in animal models of TBI, decreasing lesion volume or increasing remaining tissue. However, more studies are needed using assessing methods with lower risk of histological artifacts.

Branched-Chain Amino Acids Are Neuroprotective Against Traumatic Brain Injury and Enhance Rate of Recovery: Prophylactic Role for Contact Sports and Emergent Use

Branched-chain amino acids (BCAAs) are known to be neurorestorative after traumatic brain injury (TBI). Despite clinically significant improvements in severe TBI patients given BCAAs after TBI, the approach is largely an unrecognized option. Further, TBI continues to be the most common cause of morbidity and mortality in adolescents and adults. To date, no study has evaluated whether BCAAs can be preventive or neuroprotective if taken before a TBI. We hypothesized that if BCAAs were elevated in the circulation before TBI, the brain would readily access the BCAAs and the severity of injury would be reduced. Before TBI induction with a standard weight-drop method, 50 adult mice were randomized into groups that were shams, untreated, and pre-treated, post-treated, or pre- + post-treated with BCAAs. Pre-treated mice received BCAAs through supplemented water and were dosed by oral gavage 45 min before TBI induction. All mice underwent beam walking to assess motor recovery, and the Morris water maze assessed cognitive function post-injury. On post-injury day 14, brains were harvested to assess levels of astrocytes and microglia with glial fibrillary acidic protein (GFAP) and ionized calcium-binding adapter molecule 1 (IBA-1) immunohistochemistry, respectively. Pre-treated and pre- +post-treated mice exhibited significantly better motor recovery and cognitive function than the other groups. The pre- + post-treated group had the best overall memory performance, whereas the pre-treated and post-treated groups only had limited improvements in memory compared to untreated animals. Pre- + post-treated brains had levels of GFAP that were similar to the sham group, whereas the pre-only and post-only groups showed increases. Although trends existed, no meaningful changes in IBA-1 were detected. This is the first study, animal or human, to demonstrate that BCAA are neuroprotective and substantiates their neurorestorative benefits after TBI, most likely through the important roles of BCAAs to glutamate homeostasis.

Development of a novel progesterone analog in the treatment of traumatic brain injury

Although systemic progesterone (PROG) treatment has been shown to be neuroprotective by many laboratories and in multiple animal models of brain injury including traumatic brain injury (TBI), PROG's poor aqueous solubility limits its potential for use as a therapeutic agent. The problem of solubility presents challenges for an acute intervention for neural injury, when getting a neuroprotectant to the brain quickly is crucial. Native PROG (nPROG) is hydrophobic and does not readily dissolve in an aqueous-based medium, so this makes it harder to give under emergency field conditions. An agent with properties similar to those of PROG but easier to store, transport, formulate, and administer early in emergency trauma situations could lead to better and more consistent clinical outcomes following TBI. At the same time, the engineering of a new molecule designed to treat a complex systemic injury must anticipate a range of translational issues including solubility and bioavailability. Here we describe the development of EIDD-1723, a novel, highly stable PROG analog with >10⁴-fold higher aqueous solubility than that of nPROG. We think that, with further testing, EIDD-1723 could become an attractive candidate use as a field-ready treatment for TBI patients. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".

Repurposing and repositioning neurosteroids in the treatment of traumatic brain injury: A report from the trenches

The field of neuroprotection after brain injuries has been littered with failed clinical trials. Finding a safe and effective treatment for acute traumatic brain injury remains a serious unmet medical need. Repurposing drugs that have been in use for other disorders is receiving increasing attention as a strategy to move candidate drugs more quickly to trial while reducing the very high cost of new drug development. This paper describes our own serendipitous discovery of progesterone's neuroprotective potential, and the strategies we are using in repurposing and developing this hormone for use in brain injuries-applications very different from its classical uses in treating disorders of the reproductive system. We have been screening and testing a novel analog that maintains progesterone's therapeutic properties while overcoming its physiochemical challenges, and testing progesterone in combination treatment with another pleiotropic hormone, vitamin D. Finally, our paper, in the context of the problems and pitfalls we have encountered, surveys some of the factors we found to be critical in the clinical translation of repurposed drugs. This article is part of the Special Issue entitled 'Drug Repurposing: old molecules, new ways to fast track drug discovery and development for CNS disorders'.

Evaluating the neurotherapeutic potential of a water-soluble progesterone analog after traumatic brain injury in rats

The poor aqueous solubility of progesterone (PROG) limits its potential use as a therapeutic agent. We designed and tested EIDD-1723, a novel water-soluble analog of PROG with >100-fold higher solubility than that of native PROG, as candidate for development as a field-ready treatment for traumatic brain injury (TBI). The pharmacokinetic effects of EIDD-1723 on morphological and functional outcomes in rats with bilateral cortical impact injury were evaluated. Following TBI, 10-mg/kg doses of EIDD-1723 or PROG were given intramuscularly (i.m.) at 1, 6 and 24 h post-injury, then daily for the next 6 days, with tapering of the last 2 treatments. Rats were tested pre-injury to establish baseline performance on grip strength and sensory neglect, and then retested at 4, 9 and 21 days post-TBI. Spatial learning was evaluated from days 11-17 post-TBI. At 22 days post-injury, rats were perfused and brains extracted and processed for lesion size. For the edema assay the animals were killed and brains removed at 24 h post-injury. EIDD-1723 significantly reduced cerebral edema and improved recovery from motor, sensory and spatial learning deficits as well as, or better than, native PROG. Pharmacokinetic investigation after a single i.m. injection in rats revealed that EIDD-1723 was rapidly converted to the active metabolite EIDD-036, demonstrating first-order elimination kinetics and ability to cross the blood-brain barrier. Our results suggest that EIDD-1723 represents a substantial advantage over current PROG formulations because it overcomes storage, formulation and delivery limitations of PROG and can thereby reduce the time between injury and treatment.

Progesterone binding nano-carriers based on hydrophobically modified hyperbranched polyglycerols

Progesterone (Pro) is a potent neurosteroid and promotes recovery from moderate Traumatic Brain Injury but its clinical application is severely impeded by its poor water solubility. Here we demonstrate that reversibly binding Pro within hydrophobically modified hyperbranched polyglycerol (HPG-Cn-MPEG) enhances its solubility, stability and bioavailability. Synthesis, characterization and Pro loading into HPG-Cn-MPEG is described. The release kinetics are correlated with structural properties and the results of Differential Scanning Calorimetry studies of a family of HPG-Cn-MPEGs of varying molecular weight and alkylation. While the maximum amount of Pro bound correlates well with the amount of alkyl carbon per molecule contributing to its hydrophobicity, the dominant first order rate constant for Pro release correlates strongly with the amount of structured or bound water in the dendritic domain of the polymer. The results provide evidence to justify more detailed studies of interactions with biological systems, both single cells and in animal models.