(Reuters) – Eton Pharmaceuticals Inc said on Friday that the U.S. Food and Drug Administration declined to approve its treatment for conjunctivitis, sending its shares tumbling nearly 20 percent in extended trading.

No concerns were raised about the clinical data in the application, and the company expects to respond to the FDA’s complete response letter shortly, Eton said, without providing more detail.

Eton also said it does not expect any additional clinical work would be required for the approval of the treatment.

“We believe the issues cited in the complete response letter can be addressed in the coming months,” Chief Executive Officer Sean Brynjelsen said.

The company sold the U.S. rights to its EM-100 eye drop for treating itching associated with allergic conjunctivitis to Bausch Health Companies Inc in February.

(Reporting by Aakash Jagadeesh Babu in Bengaluru; Editing by Anil D’Silva)