Tasimelteon

Risk Summary

Available postmarketing case reports with tasimelteon use in pregnant women are not sufficient to evaluate drug-associated risk of major birth defects, miscarriage or adverse maternal or fetal outcomes. In pregnant rats, no embryofetal developmental toxicity was observed at exposures of 50 mg/kg/day, or up to 24 times higher than the human exposure at the maximum recommended human dose (MRHD) (see Data).

The estimated background risk of major birth defects and miscarriage for the indicated populations are unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively.

Data

Animal Data

In pregnant rats administered tasimelteon at oral doses of 5, 50, or 500 mg/kg/day during the period of organogenesis, there were no effects on embryofetal development. The highest dose tested is approximately 240 times the MRHD of 20 mg/day, based on mg/m² body surface area.

In pregnant rabbits administered tasimelteon at oral doses of 5, 30, or 200 mg/kg/day during the period of organogenesis, embryolethality and embryofetal toxicity (reduced fetal body weight and delayed ossification) were observed at the highest dose tested. The highest dose is approximately 200 times the MRHD.

Oral administration of tasimelteon at 50, 150, or 450 mg/kg/day to rats throughout organogenesis resulted in persistent reductions in body weight, delayed sexual maturation, and physical development, and neurobehavioral impairment in offspring at the highest dose tested which is approximately 220 times the MRHD based on mg/m² body surface area. Reduced body weight in offspring was also observed at the mid-dose. The no effect dose (NOEL), (50 mg/kg/day) is approximately 25 times the MRHD based on mg/m² body surface area.

Risk Summary

There are no data on the presence of tasimelteon or its metabolites in human or animal milk, the effects on the breastfed infant, or the effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for tasimelteon and any potential adverse effects on the breastfed infant from tasimelteon or from the underlying maternal condition.

Carcinogenesis

Tasimelteon was administered orally for up to two years to mice (30, 100, and 300 mg/kg/day) and rats (20, 100, and 250 mg/kg/day). No evidence of carcinogenic potential was observed in mice; the highest dose tested is approximately 75 times the maximum recommended human dose (MRHD) of 20 mg/day, based on a mg/m² body surface area. In rats, the incidence of liver tumors was increased in males (adenoma and carcinoma) and females (adenoma) at 100 and 250 mg/kg/day; the incidence of tumors of the uterus (endometrial adenocarcinoma) and uterus and cervix (squamous cell carcinoma) were increased at 250 mg/kg/day. There was no increase in tumors at the lowest dose tested in rats, which is approximately 10 times the MRHD based on a mg/m² body surface area.

Mutagenesis

Tasimelteon was negative in an in vitro bacterial reverse mutation (Ames) assay, an in vitro cytogenetics assay in primary human lymphocytes, and an in vivo micronucleus assay in rats.

Impairment of Fertility

When male and female rats were given tasimelteon at oral doses of 5, 50, or 500 mg/kg/day prior to and throughout mating and continuing in females to gestation day 7, estrus cycle disruption and decreased fertility were observed at all but the lowest dose tested. The no-effect dose for effects on female reproduction (5 mg/kg/day) is approximately 2 times the MRHD based on a mg/m² body surface area.

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice.

A total of 1346 subjects were treated with at least one dose of tasimelteon, of which 139 were treated for >26 weeks and 93 were treated for >1 year.

A 26-week, parallel-arm placebo-controlled study (Study 1) evaluated tasimelteon (n=42) compared to placebo (n=42) in patients with Non-24. A randomized-withdrawal, placebo-controlled study of 8 weeks duration (Study 2) also evaluated tasimelteon (n=10), compared to placebo (n=10), in patients with Non-24.

In placebo-controlled studies, 6% of patients exposed to tasimelteon discontinued treatment due to an adverse event, compared with 4% of patients who received placebo.

Table 1 shows the incidence of adverse reactions from Study 1.

Table 1. Adverse Reactions in Study 1:

* Adverse reactions with an incidence >5% and at least twice as high on tasimelteon than on placebo are displayed.