Zip so why can't Amphastar start at the same place Sanofi does and end at the same place too would that violate Sanofi patents?
It is very different to take a recipe and make a product than to take that product, reverse-engineer it and prove it is the same. IF in the process of reverse-engineering and proof of sameness Amphastar/TEVA used the MNTA patented process then it could lead to blocking the launch* or a court ordered royalty for the use of the patent.
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* Of course, negotiated settlements are also possible.