Skip to main content
2024 PharmSci 360 Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.
Back

Discovery and Basic Research

(T1230-04-22) Investigation of the Anticonvulsant Effect of a New Oxazolidinone Derivative PH166 in Rats

Tuesday, October 22, 2024
12:30 PM – 1:30 PM MT
Purpose: We previously showed that of all the oxazolidinone compounds evaluated, PH192 (figure 1) protected about 70% of rats from chemically- and electrically-induced seizures while maintaining an excellent safety index. However, this anticonvulsant effect was only observed for 30 minutes (1). This may be due to rapid elimination and/or limited brain distribution of PH192. We proposed to screen other lead compounds to explore their favorable pharmacokinetic characteristics for further development. Here we report on the pharmacokinetics and brain distribution of one of these compounds, PH166 (Figure 1), in addition to its anticonvulsant effect in rats.

Methods: PH166 was synthesized and structure confirmed by using previously published methodology (2-4). The pharmacokinetics, brain distribution, and anticonvulsant activity of PH166 were studies in male Sprague-Dawley rats (120-150 g; age  21-25 days), obtained from Kuwait University HSC Animal Resource center. All animal experiments were approved by Kuwait University, Animal Use in Research Ethics committee. The electrically induced 6 Hz complex psychomotor seizures were performed in rats using Ugo-Basile ECT Unit 57800, equipped with ear clips for rats. The 6 Hz seizures were induced using a 40 mA current pulse, 0.2 ms width for a total duration of 3 s (1). All seizures were staged based on the classification described by Mares and Kubova (5). Briefly, mouth and facial movement is considered stage 1, head nodding stage 2, fore limb clonus stage 3, rearing stage 4, and rearing with falling tonic-clonic stage 5. The rats were pretreated with intraperitoneal (IP) injection of 100 mg/kg PH166 at 0, 15, 30, 60, 120, 180 minutes prior to induction of seizures with the electrical shock. Control animals received an equivalent volume of the solvent (DMSO). Each test group consisted of a minimum of 5 rats. After induction of seizures the rats were videotaped and two trained experimenters observed each animal and both had to agree on the stage of a seizure. Rats experiencing stages 1or 2 seizures are considered protected while rats experiencing stages 4 or 5 are deemed as full seizures. Immediately after evaluating the anticonvulsant effect of PH166, rats were euthanized, then blood and brain tissue samples were obtained and frozen at -80 °C until analysis. Quantitative determination of PH166 concentrations in rat plasma and brain tissue were measured using LC/MS/MS method which was linear from 2-30 µg/ml for plasma and 0.5-5 µg/gm for brain tissue.

Results: The average maximum plasma concentration of PH166 was 18.1 µg/ml achieved after 30 min, while the average maximum brain tissue concentration of PH166 was 2.83 µg/gm achieved after 60 min of its administration (Figure 2). The concentration of PH166 decreased gradually in plasma and brain tissues, however its average plasma concentration was above 10 µg/ml and its average brain tissue concentration was about 1.5 µg/gm tissue after 180 min of its administration. It was evident that relatively high PH166 concentrations were maintained in the rat plasma and brain during the 180 min, which is the entire length of the experiment. This was reflected on the observed anticonvulsant effect of this compound where at least 80% of rats were protected from electrically induced seizures during the 180 min and 100% of rats were protected from seizure at  30 min (Figure 3). All rats in the control group which received the solvent developed stage 5 seizures. A rough estimate for the brain tissue to plasma distribution ratio for PH166 is about 15% which is considered relatively good brain tissue distribution.

Conclusion: The obtained results demonstrate that the anticonvulsant activity of PH166 against electrically induced seizures is superior to that of PH192. This is because its anticonvulsant effect was observed at least for 180 min after its administration in contrast to the limited 30 min anticonvulsant effect for PH192. It is possible that the slightly higher lipophilicity of PH166 (ClogP 1.217) compared to PH192 (ClogP 1.055) enhanced the brain distribution for PH166 besides other pharmacokinetic differences. Determination of the pharmacokinetic behavior and the brain distribution of the screened compounds together with the anticonvulsant effect added valuable information to explain the obtained observations. Further screening of other oxazolidinone compounds should shed insight for the structural and pharmacokinetic features that can improve the anticonvulsant effect and duration of activity of this group of compounds, which can lead to better lead compounds for further development.

References: 1- Qaddoumi MG, Phillips OA, and Kombian SB (2019). A novel oxazolidinone derivative PH192 demonstrates anticonvulsant activity in vivo in rats and mice. Eur. J. Pharm. Sci., 130 21-26 (2019).
2- Phillips OA, Udo EE, Ali AAM and Al-Hassawi N, 2003. Synthesis and antibacterial activity of 5-substituted oxazolidinones. Bioorg. Med. Chem. 11(1), 35-41.
3- Phillips OA, Udo EE, Ali AAM and Samuel S, 2005. Synthesis and antibacterial activity of new N-linked 5- triazolylmethyl oxazolidinones. Bioorg. Med. Chem. 13(12), 4113-4123.
4- Phillips OA, Udo EE, Abdel-Hamid ME and Varghese R, 2013. Synthesis and antibacterial activities of N-substituted-glycinyl 1H-1,2,3-triazolyl oxazolidinones. Europ. J. Med. Chem. 66:246-257.
5- Mares P, Kubova H (2006). Electrical stimulation induced models of seizures. In: Pitkanen A, Schartzkroin PA and Moshe SL, editors. Models of seizures and epilepsy. New York: Elsevier Academic Press. pp. 153-159.

Acknowledgements: This study was supported by a grant from Kuwait University Research Sector (PP02/19). Research Sector Project Unit - College of Science Grant GS01/01, GS01/03 and GS01/05. Animals were supplied by the Animal Resources Center, HSC, Kuwait University.


Figure 1: The chemical structure of two oxazolidinone compounds PH192 and PH166


Figure 2: Plasma and brain tissue concentrations of PH166 after IP administration of 100 mg/kg (expressed as mean±SD) at different time points.


Figure 3: The number of rats protected from the electrically induced seizures after pretreatment with 100 mg/kg of PH166.