** Shares of Merck MRK.N fall 1.2% to $127.79 premarket, AbbVie ABBV.N shares marginally down at $252.71

** A U.S. House committee has launched investigations into Merck and AbbVie over their clinical trials in China, including sites in Xinjiang and Chinese military-affiliated hospitals, Reuters reports citing letters

** Lawmakers ask the companies to provide details on trial oversight, patient protections, data security and due diligence by July 17

** Merck says patient safety and ethical integrity are priorities of its clinical research program and that it follows all global guidelines; AbbVie declines to comment

** Committee says there is no evidence of wrongdoing, but warns that trials in China may pose ethical concerns and risks of sensitive biotechnology knowledge reaching the Chinese military

** As of last close, MRK up 22.9%, ABBV up 11.3% YTD