Hydrolytic biotransformation of the bumetanide ester prodrug DIMAEB to bumetanide by esterases in neonatal human and rat serum and neonatal rat brain-A new treatment strategy for neonatal seizures?

Effects of bumetanide on neonatal seizures: A systematic review of animal and human studies

BACKGROUND

Bumetanide, an inhibitor of the sodium-potassium-chloride cotransporter-1, has been suggested as an adjunct to phenobarbital for treating neonatal seizures.

METHODS

A systematic review of animal and human studies was conducted to evaluate the efficacy and safety of bumetanide for neonatal seizures. PubMed, Embase, CINAHL and Cochrane databases were searched in March 2023.

RESULTS

26 animal (rat or mice) studies describing 38 experiments (28 in-vivo and ten in-vitro) and two human studies (one RCT and one open-label dose-finding) were included. The study designs, methods to induce seizures, bumetanide dose, and outcome measures were heterogeneous, with only 4/38 experiments being in animal hypoxia/ischaemia models. Among 38 animal experiments, bumetanide was reported to have antiseizure effects in 21, pro-seizure in six and ineffective in 11. The two human studies (n = 57) did not show the benefits of bumetanide as an add-on agent to phenobarbital in their primary analyses, but one study reported benefit on post-hoc analysis. Overall, hearing impairment was detected in 5/37 surviving infants in the bumetanide group vs. 0/13 in controls. Four of the five infants with hearing impairment had received aminoglycosides concurrently. Other adverse effects reported were diuresis, mild-to-moderate dehydration, hypotension, and electrolyte disturbances. The studies did not report on long-term neurodevelopment. The certainty of the evidence was very low.

CONCLUSION

Animal data suggest that bumetanide has inconsistent effects as an antiseizure medication in neonates. Data from human studies are scarce and raise some concerns regarding ototoxicity when given with aminoglycosides. Well conducted studies in animal models of hypoxic-ischaemic encephalopathy are urgently needed. Future RCTs, if conducted in human neonates, should have an adequate sample size, assess neurodevelopment, minimize using aminoglycosides, be transparent about the potential ototoxicity in the parent information sheet, conduct early hearing tests and have trial-stopping rules that include hearing impairment as an outcome.

Evaluation of bumetanide as a potential therapeutic agent for Alzheimer's disease

Therapeutics discovery and development for Alzheimer's disease (AD) has been an area of intense research to alleviate memory loss and the underlying pathogenic processes. Recent drug discovery approaches have utilized in silico computational strategies for drug candidate selection which has opened the door to repurposing drugs for AD. Computational analysis of gene expression signatures of patients stratified by the APOE4 risk allele of AD led to the discovery of the FDA-approved drug bumetanide as a top candidate agent that reverses APOE4 transcriptomic brain signatures and improves memory deficits in APOE4 animal models of AD. Bumetanide is a loop diuretic which inhibits the kidney Na+-K+-2Cl- cotransporter isoform, NKCC2, for the treatment of hypertension and edema in cardiovascular, liver, and renal disease. Electronic health record data revealed that patients exposed to bumetanide have lower incidences of AD by 35%-70%. In the brain, bumetanide has been proposed to antagonize the NKCC1 isoform which mediates cellular uptake of chloride ions. Blocking neuronal NKCC1 leads to a decrease in intracellular chloride and thus promotes GABAergic receptor mediated hyperpolarization, which may ameliorate disease conditions associated with GABAergic-mediated depolarization. NKCC1 is expressed in neurons and in all brain cells including glia (oligodendrocytes, microglia, and astrocytes) and the vasculature. In consideration of bumetanide as a repurposed drug for AD, this review evaluates its pharmaceutical properties with respect to its estimated brain levels across doses that can improve neurologic disease deficits of animal models to distinguish between NKCC1 and non-NKCC1 mechanisms. The available data indicate that bumetanide efficacy may occur at brain drug levels that are below those required for inhibition of the NKCC1 transporter which implicates non-NKCC1 brain mechansims for improvement of brain dysfunctions and memory deficits. Alternatively, peripheral bumetanide mechanisms may involve cells outside the central nervous system (e.g., in epithelia and the immune system). Clinical bumetanide doses for improved neurological deficits are reviewed. Regardless of mechanism, the efficacy of bumetanide to improve memory deficits in the APOE4 model of AD and its potential to reduce the incidence of AD provide support for clinical investigation of bumetanide as a repurposed AD therapeutic agent.

Progress report on new antiepileptic drugs: A summary of the Sixteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XVI): II. Drugs in more advanced clinical development

The Sixteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XVI) was held in Madrid, Spain on May 22-25, 2022 and was attended by 157 delegates from 26 countries representing basic and clinical science, regulatory agencies, and pharmaceutical industries. One day of the conference was dedicated to sessions presenting and discussing investigational compounds under development for the treatment of seizures and epilepsy. The current progress report summarizes recent findings and current knowledge for seven of these compounds in more advanced clinical development for which either novel preclinical or patient data are available. These compounds include bumetanide and its derivatives, darigabat, ganaxolone, lorcaserin, soticlestat, STK-001, and XEN1101. Of these, ganaxolone was approved by the US Food and Drug Administration in March 2022 for the treatment of seizures associated with cyclin-dependent kinase-like 5 deficiency disorder in patients 2 years of age and older.

Administration of Phosphonate Inhibitors of Dehydrogenases of 2-Oxoglutarate and 2-Oxoadipate to Rats Elicits Target-Specific Metabolic and Physiological Responses

In vitro and in cell cultures, succinyl phosphonate (SP) and adipoyl phosphonate (AP) selectively target dehydrogenases of 2-oxoglutarate (OGDH, encoded by OGDH/OGDHL) and 2-oxoadipate (OADH, encoded by DHTKD1), respectively. To assess the selectivity in animals, the effects of SP, AP, and their membrane-penetrating triethyl esters (TESP and TEAP) on the rat brain metabolism and animal physiology are compared. Opposite effects of the OGDH and OADH inhibitors on activities of OGDH, malate dehydrogenase, glutamine synthetase, and levels of glutamate, lysine, citrulline, and carnosine are shown to result in distinct physiological responses. ECG is changed by AP/TEAP, whereas anxiety is increased by SP/TESP. The potential role of the ester moiety in the uncharged precursors of the 2-oxo acid dehydrogenase inhibitors is estimated. TMAP is shown to be less efficient than TEAP, in agreement with lower lipophilicity of TMAP vs. TEAP. Non-monotonous metabolic and physiological impacts of increasing OADH inhibition are revealed. Compared to the non-treated animals, strong inhibition of OADH decreases levels of tryptophan and beta-aminoisobutyrate and activities of malate dehydrogenase and pyruvate dehydrogenase, increasing the R–R interval of ECG. Thus, both metabolic and physiological actions of the OADH-directed inhibitors AP/TEAP are different from those of the OGDH-directed inhibitors SP/TESP, with the ethyl ester being more efficient than methyl ester.

A combination of phenobarbital and the bumetanide derivative bumepamine prevents neonatal seizures and subsequent hippocampal neurodegeneration in a rat model of birth asphyxia

OBJECTIVES

Bumetanide was suggested as an adjunct to phenobarbital for suppression of neonatal seizures. This suggestion was based on the idea that bumetanide, by reducing intraneuronal chloride accumulation through inhibition of the Na-K-2Cl cotransporter NKCC1, may attenuate or abolish depolarizing γ-aminobutyric acid (GABA) responses caused by birth asphyxia. However, a first proof-of-concept clinical trial failed. This could have had several reasons, including bumetanide's poor brain penetration, the wide cellular NKCC1 expression pattern in the brain, and problems with the general concept of NKCC1's role in neonatal seizures. We recently replicated the clinical failure of bumetanide to potentiate phenobarbital's effect in a novel rat model of birth asphyxia. In this study, a clinically relevant dose (0.3 mg/kg) of bumetanide was used that does not lead to NKCC1-inhibitory brain levels. The aim of the present experiments was to examine whether a much higher dose (10 mg/kg) of bumetanide is capable of potentiating phenobarbital in this rat model. Furthermore, the effects of the two lipophilic bumetanide derivatives, the ester prodrug N,N-dimethylaminoethylester of bumetanide (DIMAEB) and the benzylamine derivative bumepamine, were examined at equimolar doses.

METHODS

Intermittent asphyxia was induced for 30 min by exposing male and female P11 rat pups to three 7 + 3 min cycles of 9% and 5% O₂ at constant 20% CO₂ . All control pups exhibited neonatal seizures after the asphyxia.

RESULTS

Even at 10 mg/kg, bumetanide did not potentiate the effect of a submaximal dose (15 mg/kg) of phenobarbital on seizure incidence, whereas a significant suppression of neonatal seizures was determined for combinations of phenobarbital with DIMAEB or, more effectively, bumepamine, which, however, does not inhibit NKCC1. Of interest, the bumepamine/phenobarbital combination prevented the neurodegenerative consequences of asphyxia and seizures in the hippocampus.

SIGNIFICANCE

Both bumepamine and DIMAEB are promising tools that may help to develop more effective lead compounds for clinical trials.