Chirality as a Patent Protection Policy—An Example with Citalopram

Abstract

ABSTRACTThe aim of this study was to analyze the patent protection policy of Citalopram as an example for protection of a biologically active chiral structure. A three-step search methodology of patent expiration date, EPO database was performed, and an expanded search was done via the INPADOC patent family system. The patents found were systematized according to the main International Patent Classification (IPC) class, C07 subclasses, and were analyzed by patent claim.Our search methodology revealed 189 patents for citalopram issued during 1990–2010. The patents from IPC class A61K are divided among patents for composition (31%), salts and crystallization forms (38%), and combinations (31%). The patents from class C07 are almost equally allocated among subclasses C07C (acyclic or carbocyclic compounds—49 patents) and C07D (heterocyclic compounds—59 patents), with 5 additional patents from class C07B (general methods of organic chemistry). By C07 IPC subclass the distribution of issued patents is mainly for C07D (heterocyclic compounds) that correspond to the main active biological structure. By type of claim the patents for methods (n = 29) and processes (n = 20) are almost equally represented. There are only two patents for composition—for pharmaceutical composition containing citalopram and for the crystalline base of citalopram, whereas the patents for methods for preparation were nine.Our study showed that the number of patents from class C07, which protect the substance, is almost double compared with other classes. The chiral structure of citalopram might also explain the fact that the patents within class C07 are more than those in class A61K. It is evident that the companies prefer to protect both the main structure and the chiral enantiomers.