The Food and Drug Administration (FDA) has requested that pharmaceutical companies Regeneron and Sanofi assess a cholesterol-combatting medication for possible neurocognitive side effects. 

Called alirocumab, the drug essentially works by blocking a protein that retains LDL cholesterol in the bloodstream. LDL cholesterol, or low-density lipoprotein, is colloquially known as the bad stuff - the cholesterol that can build up on the interior of arterial walls. If it combines with other substances, the build up can become increasingly inflexible, ultimately thinning the passage of the arteries with a plaque-like substance called atherosclerosis. In the event of clots forming, the narrowed arteries could then be blocked, leading to a stroke or heart attack. 

Alirocumab is one of a new crop of drugs called PCSK9 inhibitors, and, while promising, the jury's still out on whether or not it comes saddled with neurocognitive side effects that may prove dangerous. Regeneron and Sanofi are not the only developers of this type of drug: Pfizer and Amgen are also in the process of synthesizing similar, competitor drugs. Pfizer revealed that they had not been asked to provide details of neurocognitive effects. "At this stage of our bococizumab development program, we are not aware of any neurocognitive safety signals," the company advised. 

Regeneron and Sanofi expressed some surprise at the FDA's knowledge of side effects in statins - used to curb LDL levels - which have been noted in the past as potentially being the catalyst for memory loss, impaired concentration, and paranoia. Interestingly, the FDA has expressed an interest in approving PCSK9 inhibitors based solely on the ability to reduce cholesterol, without the need to demonstrate evidence that they subsequently reduce the chance of heart attacks and strokes. However, this allowance would be trumped by presence of neurocognitive risk, if deemed present. Sanofi and Regeneron have noted that active risk could delay or even terminate the development of alirocumab. 

"While we continue to believe the PCSK9 class has multi-billion dollar potential, we note that increased speculation on adverse events may increase the probability that the FDA could require outcomes data prior to full approval," said JP Morgan analyst Geoff Meacham in a research note.