This case is focused on polymorphs, and specifically the standards for inventiveness applicable to new crystalline forms of a known drug.  A recent decision from the Korean Supreme Court revised the inventiveness assessment for polymorph inventions to account for difficulty in deriving the constitutional elements of the claimed crystalline form, contrary to previous practice.

An invention claiming a compound of a specific crystalline form different from a known compound is referred to as a “crystalline form invention” or “polymorph invention.”  It is widely known in the pharmaceutical compound field that a single compound may have multiple crystalline forms with different pharmaceutical characteristics, such as solubility and stability.

This case started with the Korean Intellectual Property Office’s final rejection of a patent application claiming a new crystalline form of a known macrolide compound.  The Patent Court affirmed the final rejection with the reasoning that a person skilled in the art would routinely investigate a pharmaceutical compound’s crystalline polymorphism for formulation design and optimization.  If a polymorph invention differs from a previously known compound only with respect to its crystalline structure, inventiveness should be recognized only if the polymorph exhibits qualitatively different or quantitatively remarkable effects compared to the previously known compound.  The Patent Court’s decision was in line with the existing inventiveness standards for polymorph inventions, where inventiveness is recognized only if a surprising technical effect is identified, and denied the inventiveness of the claimed crystalline form invention based on prior art that merely disclosed the general compound itself, without any reference to crystalline forms.  However, the Supreme Court reversed the Patent Court’s decision (Supreme Court Decision 2018Hu10923, March 31, 2022).

The Supreme Court ruled that even if the so-called “polymorphism screening” (which examines whether a certain compound has multiple crystalline forms) is a test ordinarily conducted in the field of pharmaceutical compounds, whether a specific crystalline form easily could have been constructed is still a separate issue that must be reviewed and determined on a case-by-case basis.  The Supreme Court concluded that “technical difficulty in deriving the constitutional elements” of a crystalline form invention could not be denied solely because polymorphism screening is ordinarily conducted.

Specifically, the Supreme Court identified the following factors that should be considered in determining “constitutional difficulty”:

• Whether multiple crystalline forms of the prior art compound were known or expected;

• Whether the prior art disclosed any teaching, suggestion or motivation to develop the crystalline form of the claimed invention;

• Whether the crystalline form of the claimed invention was within the scope of crystalline forms that would have been readily screened via conventional polymorphism screening of the prior art compound; and

• Whether the crystalline form of the claimed invention had unforeseen advantages over the prior art compound.

The Supreme Court reviewed the above factors in the subject case, and determined that: (i) the compound of the prior art did not specify whether it was a crystalline or amorphous form, (ii) there was no disclosure showing the existence of other polymorphs of the prior art compound, and (iii) the crystalline forms of the prior art compound and the claimed invention had different process variables such as starting material, solvent, temperature, time, etc.  As a result, the Supreme Court concluded that it would not have been obvious from the prior art that the claimed crystalline easily could have been derived, and recognized the inventiveness of the claimed invention based on its “constitutional difficulty.”

This decision is significant because the Supreme Court went against established practice regarding the inventiveness of polymorph inventions to recognize inventiveness based on the difficulty that would have existed in deriving the constitutional elements of the claimed crystalline form, regardless of its effects.  This is a major change from existing practice where the inventiveness of crystalline form inventions largely depended on whether the invention produced “remarkable effects” over the prior art, and should substantially expand the scope of crystalline form inventions that can be patented in the future.

In addition to the Supreme Court’s decision in Case No. 2019Hu10609 (rendered on April 8, 2021) that similarly broadened the inventiveness of selective inventions, this decision is expected to significantly expand the scope of patent protection for pharmaceutical products in Korea.