Monthly Archives: June 2015
Amy Price and I wrote this blog post on being patient reviewers for The BMJ.
A 2013 front page New York Times article by Gina Kolata on PCSK9 inhibitors was inaccurate. Here is Kolata’ lede:
She was a 32-year-old aerobics instructor from a Dallas suburb — healthy, college educated, with two young children. Nothing out of the ordinary, except one thing.
Her cholesterol was astoundingly low. Her low-density lipoprotein, or LDL, the form that promotes heart disease, was 14, a level unheard-of in healthy adults, whose normal level is over 100.
The reason was a rare gene mutation she had inherited from both her mother and her father. Only one other person, a young, healthy Zimbabwean woman whose LDL cholesterol was 15, has ever been found with the same double dose of the mutation.
Here is an excerpt from the FDA clinical review of Sanofi/Regeneron’s PCSK9 inhibitor alirocumab:
We are aware of three cases of individuals homozygous (or compound heterozygous) for loss-of-function PCSK9 alleles with very low LDL-C concentrations that have been reported in the literature:
1. a 21-year-old African woman with an LDL-C of 15 mg/dL; no further information about this patient was provided, except that she was identified for genotyping at a postnatal clinic,
2. a 32-year-old African American woman with an LDL-C of 14 mg/dL; she is an apparently healthy, normotensive, fertile, college-educated individual with normal liver and renal function tests, and
3. a 49-year-old French white man who was found to have extremely low LDL-C (7 mg/dL) on admission for rapid-onset of an insulin-requiring diabetes mellitus of unknown etiology; LDL-C not during acute illness was reported to be 16 mg/dL. This patient was shown to have moderate liver steatosis on abdominal ultrasound with normal hepatic enzymes and liver function tests. He had no reported history of diarrhea, eye, or neurological abnormalities related to any vitamin deficiency. His mother was deceased at age 66 from dementia, whereas his father was healthy at age 79. His grandparents died at the ages of 79, 87, 91, and 94 years.
At this time there are too few cases to provide conclusive data about loss-of-function PCSK9 polymorphisms and the risk of human disease, although given the association of statins with diabetes risk, the development of diabetes in the 49-year-old man discussed above is of interest. (See Dr. Roberts’ safety review for further discussion of alirocumab and glycemic parameters).
The third case is the one missed by Kolata. It was published in Arteriosclerosis, Thrombosis, and Vascular Biology, an American Heart Association journal, in 2009, and could have been found with a PubMed search. The case is interesting in that it conflicts with one of the oft-repeated but inaccurate narratives with respect to PCSK9 inhibitors, the idea that all known persons with extremely low LDL due to having two PCSK9 loss-of-function mutations are completely healthy. I agree with the FDA reviewer that there are too few such cases to provide conclusive data about loss-of-function PCSK9 polymorphisms that result in extremely low LDL levels and the risk of disease. (The issue of whether alirocumab increases blood glucose and the risk of developing diabetes is also discussed extensively in the review, with the reviewer concluding that the evidence is inconclusive at this point.)