Clinical drug candidates are often claimed in a patent as a pharmaceutical composition or formulation with a specified concentration range of the drug or an excipient; as being purified within certain temperature or pH ranges; or in a method of treating a disease by administering the drug at a certain dosage range. For a claim to be patentable over any prior disclosure, the claim must be novel and nonobvious. But how would a drug developer know that the claimed ranges are patentable over a prior disclosure of overlapping or broader ranges?
As discussed below, the patentability of ranges depends in part on whether the claimed range is critical to the operability of the invention and whether the claimed range was not known to be a result-effective variable.
- Overlapping Ranges
Teachings in the prior art: When prior art discloses a range that is partially or slightly overlapping, courts have held that the prior disclosure may anticipate the claimed range.
How to rebut: A showing that the claimed range is critical to the operability of the claimed invention can overcome a novelty rejection. For example, that an invention would operate differently across a broader range disclosed in the prior art may establish that the claimed range is critical to the invention.
- Specific point in a range
Teachings in the prior art: When prior art discloses a range rather than a specific point recited in a claim, then the prior art does not anticipate unless the range disclosed in the prior art overlaps with the specific point and one would conclude that there is no reasonable difference in how the invention operates over the range.
How to rebut: A showing that the prior art’s disclosure did not specifically disclose a narrower range including the specific point, and that the range or the point would be critical for the operability of the claimed invention.
Presumption of obviousness based on the teachings in prior art: When the ranges of a claimed composition overlap the ranges disclosed in a prior art reference, there is a presumption of obviousness.
Obviousness is presumed even if the overlap between the claimed range and the range described in the prior art is slight. However, a prior art need not describe an overlapping range; obviousness exists when the claimed range and the prior art range do not overlap but are close enough such that one skilled in the art would have expected the ranges to have the same properties.
How to rebut: Nonobviousness of a claimed range can be shown by one of the following:
- The claimed range or a specific point within the range is critical or special to the operability of the claimed invention: A showing that the claimed range produces a new and unexpected result, which is different in kind and not merely in degree from the results of the prior art might establish criticality of the claimed range. And if the claim recites ranges of multiple variables, then evidence that the variables interacted in an unpredictable or unexpected way could help establish that the combination would be nonobvious. For example, a demonstration that there was no expectation for a specific dose of a drug administered in combination with a specific dose of another drug would be safe or effective could help establish criticality of the claimed range.
- The claimed range was not suggested to be a result-effective variable: Where the ranges of a claim are disclosed in a prior art reference, discovery of optimum or workable ranges by routine experimentation is not patentable. However, those skilled in the art must have recognized that the optimization of the range might achieve a desired result (such a variable is known in patent law as “result-effective variable”). Thus, if the prior art failed to suggest that a desired result/outcome of the invention would be affected by varying a claimed element within the range recited in the claim, then the claimed range is not a result-effective variable, i.e., the claim would be nonobvious.
- The claimed range is not the product of discovery of an optimum or workable range after routine optimization of broad or overlapping ranges described in the prior art: If the prior art capped the range of the non-overlapping range, one may argue that the claimed dose or range is nonobvious. In such instances, one may argue that the prior art would not have motivated a skilled person to optimize a claimed element within the recited range; and thus, the claimed range was not the product of discovery of an optimum or workable range after routine optimization.
- The prior art teaches away from the claimed range: The surest way to overcome a challenge that a claimed range is obvious would be if the prior art teaches away or the facts support that a skilled person would have been discouraged from using the dose as claimed. For example, a showing that a skilled person would have interpreted from the prior art that the claimed range would not be operable could support that the claimed range is nonobvious.
Shovon Ashraf, Ph.D.