Merck & Co has decided to terminate a study of its experimental cholesterol combination treatment, MK-0524A, less than a month after US regulators issued a not approvable letter for the drug.

The firm is discontinuing ACHIEVE, an imaging study evaluating MK-0524A (extended-release niacin/laropiprant) in patients with heterozygous familial hypercholesterolemia at the recommendation of the trial’s steering committee. That decision was based on a review and evaluation of scientific data from recent carotid intima-media thickness studies and follows the Committee’s recommendation (made on March 29) to put patient enrollment on hold.

Merck insisted that the decision to discontinue the study is not related to the US Food and Drug Administration’s rejection of MK-0524A, and preliminary data did not suggest any safety concerns. John Kastelein, chair of the ACHIEVE steering committee, said it was clear from the review of pooled data from recently-completed studies of other medicines that the people being studied in ACHIEVE “was no longer the correct population to test the primary study hypothesis of IMT progression”.

Merck added that it remains committed to the development of MK-0524A and, as such, “all other ongoing clinical studies, including the 20,000-patient outcomes study known as HPS2-THRIVE, continue unchanged”. The drug, which lowers ‘bad’ low-density lipoprotein cholesterol and triglyceride levels, and also increases cardioprotective ‘good’ high-density lipoprotein cholesterol levels, recently received a positive recommendation from European regulators.