long-acting SSA therapy, there was also a rapid conversion of telotristat ethyl to its active metabolite. A high variability (% CV range of 18% to 99%) in telotristat ethyl and its active metabolite parameters was observed within the overall PK. The mean PK parameters for telotristat ethyl and the active metabolite appeared unchanged between week 24 and week 48, suggesting the achievement of steady-state conditions at or prior to week 24.
Food effect
In a food effect study administration of telotristat ethyl 500 mg with a high-fat meal resulted in higher exposure to the parent compound (Cmax, AUC0-tlast, and AUC0-∞ being 112%, 272%, and 264% higher, respectively compared with the fasted state) and its active metabolite (Cmax, AUC0-tlast, and AUC0-∞, 47%, 32%, and 33% higher, respectively compared with the fasted state).
Distribution
Both telotristat ethyl and its active metabolite are > 99% bound to human plasma proteins.
Biotransformation
After oral administration, telotristat ethyl undergoes hydrolysis via carboxylesterases to its active and major metabolite. The only metabolite of telotristat (active metabolite) representing consistently > 10% of total plasma drug-related material was its oxidative decarboxylated deaminated metabolite, LP-951757. Systemic exposure to LP-951757 was about 35% of the systemic exposure to telotristat (active metabolite) in the mass balance study. LP-951757 was pharmacologically inactive at TPH1 in vitro.
Interactions
Cytochromes
CYP2B6
In vitro telotristat (active metabolite) caused a concentration dependent increase in CYP2B6 mRNA levels (>2-fold increase and > 20% of the positive control, with a maximum observed effect similar to the positive control), suggesting possible CYP2B6 induction (see section 4.5).
CYP3A4
Telotristat ethyl and its active metabolite were not shown to be inducers of CYP3A4 at systemically relevant concentrations, based on in vitro findings. The potential of telotristat ethyl as an inducer of CYP3A4 was not assessed at concentrations expectable at the intestinal level, due to its low solubility in vitro.
In vitro, telotristat ethyl inhibited CYP3A4, suggesting a potential interaction with CYP3A4 substrates.
In an in vivo clinical drug-drug interaction (DDI) study with midazolam (a sensitive CYP3A4 substrate), following administration of multiple doses of telotristat ethyl, the systemic exposure to concomitant midazolam was significantly decreased (see section 4.5). When 3 mg midazolam was coadministered orally after 5-day treatment with telotristat ethyl 500 mg tid (twice the recommended dose), the mean Cmax, and AUC0-inf for midazolam were decreased by 25%, and 48%, respectively, compared with administration of midazolam alone. The mean Cmax, and AUC0-inf for the active metabolite, 1'-hydroxymidazolam, were also decreased by 34%, and 48%, respectively.
Other CYPs
Based on in vitro findings, no clinically relevant interaction is expected with other cytochromes P450.
Carboxylesterases
In vitro loperamide (CES2 inhibitor) had a moderate effect on the metabolism of telotristat ethyl, reducing the formation of telotristat by <30% (see section 4.5).
In vitro, telotristat ethyl inhibited CES2 with an IC50 approximately of 6.4 μM.
Transporters
P-glycoprotein (P-gp) and Multi-drug Resistance associated Protein 2 (MRP-2)
In vitro telotristat ethyl inhibited P-gp, but its active metabolite did not at the cl |
