Canara

'Canara is a Federation planet located near the Romulan Neutral Zone.

When a third of the Romulan population died of disease in 2267, the Romulan fleet risked crossing the Neutral Zone and conquering the planet which has the only known cure for the disease.

The invasion was stopped by Captain James T. Kirk and the USS Enterprise (NCC-1701) who makes an agreement with the Romulans to give them the cure.

(TOS novel: Web of the Romulans).