If the urine hasn't liquified the leather, you can reduce the odor in hopes of eliminating it. We've done it before. Here's how we did it....
1. Remove the cushions and soak in a large tank or tub of OSR. Rinse with an acid based cleaner.
2. Apply Urine Stain Remover to the leather and let soak. Rinse heavy with water, and apply CTi's X-cide or similar product. Let dry.
3. Once dry, check for residual odors, and repeat. Once satisfactory results appear, apply leather conditioner (Leather Vital and Protection Cream), and reinstall cushions.
Let me impress on you. This is a salvage operation! The Customer must know that you can't guarantee perfect results, or a guarantee. Especially if the cat is still with them! In our case, we were successful, and the Customer was very pleased. I told them this project will be charged by the hour and materials needed. I told them stains where the urine was may be permanent, but the odor is one thing we can reduce or eliminate. The gamble was theirs and they took it!