In U.S. patent law, the Doctrine of Equivalents allows a patent owner to claim infringement by a product or process that is outside the scope of the patent claims but close enough to be considered an equivalent. The courts use two alternative tests to determine whether the doctrine should be applied. One is the function-way-result (FWR) test, which states that to be considered an equivalent, the accused product or process must perform substantially the same function in substantially the same way to obtain the same result as the product or process actually covered by the patent’s claims. The other is the insubstantial differences test, in which the accused product or process can be considered an equivalent if the difference between it and the claimed invention is insubstantial. Regardless of which test is applied, the criteria to qualify as an equivalent are difficult for chemical inventions to meet.
The recent case of Mylan Institutional LLC et al. v. Aurobindo Pharma Ltd. et al. shows why. The case centered on a series of patents obtained by Apicore US LLC based on Apicore’s process for manufacturing Isosulfan Blue. One of the issues in the case was whether the substitution of one oxidizing agent for another was still an infringement if the patent claim was...
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