Yes with Merck involved I’m sure there is strategy we aren’t privy to. They wouldn’t waste their time on a drug that was losing protection shortly after any potential approval. Marketing exclusivity can be used as a potential strategy. There are a number of ways to extend protection.
“The Guidelines acknowledge that combination products can satisfy the inventive step standard, at least when a synergistic effect can be demonstrated. In fact, there are good policy rationales supporting the availability of patent protection for inventive combination products, particularly, but not exclusively, when the combination results in a synergistic effect. Patents provide an incentive for innovators to discover combination products that provide improved therapeutic outcome compared to either individual active ingredient. Perhaps even more significantly, patents (along with test data protection) provide an incentive to fund the expensive human clinical trials necessary to verify and validate the clinical benefits.”
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