Momenta Pharmaceuticals and Sandoz claimed that Amphastar's testing of its generic enoxaparin sodium blood thinner infringed their patent, but on 21 July the US District Court for the District of Massachusetts jury found it invalid for lack of enablement and adequate written description.
The pharmaceutical companies demanded more than $900 million in damages when they filed the patent infringement suit in 2011.
After the two-week trial, the jury also found that Momenta and Sandoz had waived their ability to enforce the patent against Amphastar due to their inequitable conduct before the US Pharmacopeial Convention.
Craig Wheeler, president and CEO of Momenta, said the company is considering launching an appeal.
“We are disappointed in the jury's verdict and believe the facts and the law do not support these findings. We are considering all available legal options to overturn the verdict, including post-trial motions and appeals,” said Wheeler.
“We continue to believe in the importance of investing in innovative techniques for bringing products to market and protecting those innovations from unauthorised use.”
Amphastar CEO Dr Jack Zhang said: “We have always believed that the facts and the law do not support the plaintiffs’ baseless allegations and we are very pleased that justice has prevailed. We remain proud of our technology for product development and will continue to execute on our mission of developing and manufacturing life-saving drugs for the benefit of patients.”