* Says Merck drops Atherosclerosis treatment development
* Treatment failed to meet primary efficacy objective
* Arena shares down
NEW YORK, Dec 23 - Arena Pharmaceuticals Inc (ARNA.O) said on Wednesday that Merck & Co Inc (MRK.N) will discontinue development of an atherosclerosis treatment that the two companies were jointly collaborating on.
The news sent Arena's shares down 6.1 percent to $3.56 in trading after the closing bell.
Merck's decision to pull out from developing MK-1903 came after a mid-stage clinical trial that evaluated the treatment for safety, tolerability and potential efficacy in patients with dyslipidemia failed to meet the primary objective for efficacy, Arena said in a statement. (Reporting by Dhanya Skariachan; editing by Andre Grenon)