For which reason can a patent application be considered non-patentable?

A patent application can be considered non-patentable when the invention is deemed to be a mere obvious variation of what is already known in the field. Patentability requires that an invention must be novel and non-obvious. If the invention does not demonstrate a sufficient level of ingenuity over prior art or merely represents an obvious modification of an existing invention, it fails to meet the criteria for patentability.

This principle is rooted in patent law, which is designed to prevent the issuance of patents on inventions that are not significantly different from what is already publicly known. Therefore, if an examiner determines that the differences between the claimed invention and prior art are obvious to a person having ordinary skill in the relevant technical field, the application may be rejected for lack of non-obviousness.

In contrast, while a prior patent held by the applicant (such as in the first option) might raise issues regarding double patenting but does not by itself make the application non-patentable. The lack of a working prototype is not a requirement for patentability in itself, as many inventions can be patented based on their descriptions and claims. Lastly, an application being filed more than one year ago is not inherently a reason for non-patentability, as the time