The drug firm's scrip tanked 14.10 per cent to settle the day at Rs 684.65 on the BSE. During the day, the stock lost 17.74 per cent to Rs 655.55.
At the NSE, Natco's stock plunged 14.34 per cent to close the trade at Rs 684.
On the volume front, 4.67 lakh shares of the company changed hands on the BSE, while over 14 lakh shares were traded at the NSE during the day.
Last year, US Court of Appeals for the Federal Circuit reversed a district court's earlier finding related to Teva's US Patent for the drug.
The Appeals Court's ruling allowed the Indian drug maker along with its marketing partner to launch the generic Copaxone in May 2014, subject to FDA approval.
"...That the US Supreme Court agreed to hear appeal in a patent fight on Copaxone. The company continues to believe that Teva's 808 patent is invalid for indefiniteness," Natco said in a statement.
