How does Juxtapid (lomitapide) work in the body?
Juxtapid (lomitapide) is an inhibitor of microsomal triglyceride transfer protein (MTP). By blocking MTP in the liver (and to some extent the intestine), lomitapide prevents triglycerides from being packaged into apolipoprotein B–containing lipoproteins. This reduces the formation and secretion of very-low-density lipoprotein (VLDL) and other apoB-containing lipoproteins, which lowers circulating LDL cholesterol.
What does blocking MTP change about LDL and apoB?
Because VLDL is a major precursor of LDL, reducing VLDL production leads to lower LDL levels. The drug also decreases apoB-containing lipoproteins more broadly, since apoB is required for assembly and export of these particles from cells.
Where does Juxtapid mainly act (liver vs. intestine)?
MTP is expressed in both the liver and the intestinal epithelium. Lomitapide inhibits MTP activity in these tissues, which contributes to reduced secretion of apoB-containing lipoproteins from both sites.
Why is this mechanism useful for people with familial hypercholesterolemia?
In disorders where LDL cholesterol is high largely due to increased apoB-containing lipoprotein production or impaired clearance, lowering VLDL/apolipoprotein B secretion can reduce LDL even when other pathways are not fully effective. Juxtapid is used in settings such as homozygous familial hypercholesterolemia where the goal is to drive LDL down by cutting off apoB lipoprotein production.
What to expect mechanistically (and what it doesn’t do)
This mechanism targets the production side of lipoproteins (apoB-containing particle assembly/secretion). It does not directly increase LDL receptor numbers or directly inhibit intestinal cholesterol absorption; it reduces the supply of apoB lipoproteins leaving cells, which then leads to lower plasma LDL.
Related patient questions: does the mechanism explain the key safety monitoring?
The same pathway inhibition that reduces lipoprotein secretion can also lead to increased lipid accumulation in cells (particularly in the liver), which is why Juxtapid is associated with monitoring for hepatic fat and liver injury risk in clinical use.