Lomitapide

Lomitapide directly binds and inhibits microsomal triglyceride transfer protein (MTP), which resides in the lumen of the endoplasmic reticulum, thereby preventing the assembly of apo B-containing lipoproteins in enterocytes and hepatocytes. This inhibits the synthesis of chylomicrons and VLDL. The inhibition of the synthesis of VLDL leads to reduced levels of plasma LDL-C.

Effects on QT Interval

At a concentration 23 times the C_max of the maximum recommended dose, lomitapide does not prolong QTc to any clinically relevant extent.

Absorption

Upon oral administration of a single 60-mg dose, the lomitapide t_max is around 6 hours in healthy volunteers. The absolute bioavailability of lomitapide is approximately 7%. Lomitapide pharmacokinetics is approximately dose-proportional for oral single doses from 10-100 mg.

Distribution

The mean lomitapide volume of distribution at steady state is 985-1292 liters. Lomitapide is 99.8% plasma-protein bound.

Metabolism

Lomitapide is metabolized extensively by the liver. The metabolic pathways include oxidation, oxidative N-dealkylation, glucuronide conjugation, and piperidine ring opening. Cytochrome P450 (CYP) 3A4 metabolizes lomitapide to its major metabolites, M1 and M3, as detected in plasma. The oxidative N-dealkylation pathway breaks the lomitapide molecule into M1 and M3. M1 is the moiety that retains the piperidine ring, whereas M3 retains the rest of the lomitapide molecule in vitro. CYPs 1A2, 2B6, 2C8, and 2C19 may metabolize lomitapide to a small extent to M1. M1 and M3 do not inhibit activity of microsomal triglyceride transfer protein in vitro.

Excretion

In a mass-balance study, a mean of 59.5% and 33.4% of the dose was excreted in the urine and feces, respectively. In another mass-balance study, a mean of 52.9% and 35.1% of the dose was excreted in the urine and feces, respectively. Lomitapide was not detectable in urine samples. M1 is the major urinary metabolite. Lomitapide is the major component in the feces. The mean lomitapide terminal half-life is 39.7 hours.

Specific Populations

Hepatic Impairment

A single-dose, open-label study was conducted to evaluate the pharmacokinetics of 60 mg lomitapide in healthy volunteers with normal hepatic function compared with patients with mild (Child-Pugh A) and moderate (Child-Pugh B) hepatic impairment. In patients with moderate hepatic impairment, lomitapide AUC and C_max were 164% and 361% higher, respectively, compared with healthy volunteers. In patients with mild hepatic impairment, lomitapide AUC and C_max were 47% and 4% higher, respectively, compared with healthy volunteers. Lomitapide has not been studied in patients with severe hepatic impairment (Child-Pugh score 10-15).

Renal Impairment

A single-dose, open-label study was conducted to evaluate the pharmacokinetics of 60 mg lomitapide in patients with end-stage renal disease receiving hemodialysis compared with healthy volunteers with normal renal function. Healthy volunteers had estimated creatinine clearance >80 mL/min by the Cockcroft-Gault equation. Compared with healthy volunteers, lomitapide AUC_0-inf and C_max were 40% and 50% higher, respectively, in patients with end-stage renal disease receiving hemodialysis. Effects of mild, moderate, and severe renal impairment as well as end-stage renal disease not yet on dialysis on lomitapide exposure have not been studied.

Drug Interactions

In vitro Assessment of Drug Interactions

Lomitapide does not induce CYPs 1A2, 3A4, or 2B6. Lomitapide inhibits CYP3A4. Lomitapide does not inhibit CYPs 1A2, 2B6, 2C9, 2C19, 2D6, or 2E1. M1 and M3 do not induce CYPs 1A2, 3A4, or 2B6. M1 and M3 do not inhibit CYPs 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, or 3A4. Lomitapide is not a P-gp substrate. Lomitapide inhibits P-gp but does not inhibit breast cancer resistance protein (BCRP).

Effects of other Drugs on Lomitapide

Table 6 summarizes the effect of coadministered drugs on lomitapide AUC and C_max.

Table 6. Effect of Coadministered Drugs on Lomitapide Systemic Exposure:

BID = twice daily; QD = once daily
^↑ = increase

Effect of Lomitapide on other Drugs

Table 7 summarizes the effects of lomitapide on the AUC and C_max of coadministered drugs.

Table 7. Effect of Lomitapide on the Systemic Exposure of Coadministered Drugs:

QD = once daily; INR = international normalized ratio; ↑ = increase; ↓ = decrease
* Limit simvastatin dosage to 20 mg daily (or 40 mg daily for patients who have previously tolerated simvastatin 80 mg daily for at least one year without evidence of muscle toxicity). Refer to the simvastatin prescribing information for additional dosing recommendations.
^† Patients taking warfarin should undergo regular monitoring of the INR, especially after any changes in lomitapide dosage.