Effects of CYP2C19 and CYP2C9 polymorphisms on the efficacy and plasma concentration of lacosamide in pediatric patients with epilepsy in China.

To evaluate the effects of cytochrome P450 family 2 subfamily C member 9 (CYP2C9) and cytochrome P450 family 2 subfamily C member 19 (CYP2C19) polymorphisms on the plasma concentrations, efficacy, and safety of lacosamide (LCM) among pediatric patients with epilepsy. This prospective study was conducted at two institutions. It included 215 pediatric patients with epilepsy who were under LCM. LCM plasma concentrations were quantified using validated ultra-performance liquid chromatography. CYP2C9 and CYP2C19 polymorphisms were analyzed in all pediatric patients in our hospital's Institute of Clinical Pharmacy research laboratory through polymerase chain reaction, agarose gel electrophoresis detection, gel recovery, and other steps. Seizure frequencies were recorded 3, 6, and 12 months after initiating LCM therapy and compared with the baseline monthly frequency. Clinical information, including efficacy, toxicity, and concomitant drugs, was collected. A total of 158 pediatric patients (73.5%) responded to LCM therapy. Of them, 77 patients reported adverse events while under LCM. The LCM plasma concentration was linearly correlated with its daily dose (r = 0.26, p < 0.001). Patients with adverse events reported higher LCM plasma concentrations (7.9 ± 4.0 µg/mL) than patients without adverse events (6.8 ± 3.0 µg/mL; p < 0.05). The poor metabolizer (PM) group demonstrated the highest concentration-to-dose ratio (1.7 ± 0.7 μg·mL^-1·kg·mg^-1) than the extensive metabolizer, intermediate metabolizer, and ultra-rapid metabolizer groups (0.8 ± 0.4, 1.0 ± 0.5, and 0.8 ± 0.4 μg·mL^-1·kg·mg^-1, respectively). The PM group comprised the highest proportion of patients with effective LCM (9/11, 81.8%) and adverse events (7/11, 63.6%).

Conclusion: LCM plasma concentrations were strongly associated with its clinical efficacy and toxicity. CYP2C19 polymorphisms affect the plasma concentration and treatment efficacy in pediatric patients with epilepsy. CYP2C19 PMs with two no-function alleles are likely to have higher LCM plasma concentrations.

What is known: • LCM is metabolized by CYP2C19, CYP2C9, and CYP3A4 into pharmacologically inactive O-desmethyl-lacosamide; it primarily undergoes renal elimination. • Plasma LCM concentrations in patients treated with the recommended dose vary widely between and within individuals variability.

What is new: • CYP2C19 polymorphisms affect the plasma concentration and treatment efficacy in Chinese pediatric patients with epilepsy. • CYP2C19 PMs with two no-function alleles are likely to have higher plasma LCM concentrations.