Tuesday, 10 November 2009

T 1618/06 - Description of Prior Art vs. Disclosure of the Invention

In this decision the Board goes to great lengths to reconstruct the invention from bits and pieces contained in the priority document (D12), both in its description of the prior art and in the summary of the invention.

In order to better understand the subtleties of the reasoning, one has to know that the summary of the invention starts on page 2, paragraph 4 of D12. The preceding parts of the description deal with prior art and its disadvantages.

The [opponents] argued that claim 1 did not enjoy the priority of document D12 because the impurities mentioned in this claim were only disclosed in document D12 with respect to the prior art cited therein. [IX]

[…] It was under dispute whether or not the following feature of present claim 1 enjoyed the priority of D12: The removal of the impurity of formula II.

Hence it has to be assessed whether or not D12 teaches the person skilled in the art (i) to remove impurities from a crude mixture or a crude salt of citalopram, and, in the affirmative, (ii) whether or not these impurities comprise those of formula II as defined in present claim 1. [3.1]

The part of D12 disclosing the invention claimed therein starts with the fourth paragraph on page 2 (“It has now been found that …”). The second sentence of this paragraph states that the invention provides “ … a very good and efficient purification of citalopram …”. The starting material used in this purification process is crude salt or crude mixture of citalopram. Hence, D12 discloses a process removing impurities from a crude mixture or a crude salt of citalopram. [3.1.1]

It remains to be determined whether or not D12 discloses directly and unambiguously that the impurities to be removed comprise those of formula II as defined in present claim 1.

The process disclosed in D12 is to purify citalopram or its salt. This means that the impurities are present in the crude starting material. This starting material “ … may be obtained directly from the synthesis of the compound according to any of the above mentioned processes …”. The “above mentioned processes” are those summarised in the first and second paragraphs on page 2, including the “Exchange of 5-halogen with cyano …” (p. 2, l. 1-2). The impurities present in the reaction mixtures obtained in these processes comprise “… the intermediates mentioned above …” (third paragraph of page 2), namely the 5-halogen compound as far as the process comprising the exchange of 5-halogen by a cyano group is concerned. Consequently, the chemical formula of this impurity differs from the formula of citalopram as depicted on page 1 of D12 only in that the cyano group in the 5-position is replaced by a halogen atom; that means that it is identical with formula II depicted in present claim 1.

Hence, D12 discloses a process by which impurities of formula II as defined in present claim 1 are removed from a crude mixture or a crude salt of citalopram.

It is not relevant that part of this disclosure is based on the description of the prior art, as D12 directly refers to said prior art in the paragraphs setting out the invention claimed therein. [3.1.2]

Admittedly, this decision is not very exciting in itself but it shows that the Boards sometimes accept the argument that some features of the invention are disclosed in the part of description dedicated to prior art. As the established case law applies the same criterion (… directly and unambiguously …) to A 87 and A 123, this could sometimes be helpful to rescue an application, in particular if the drafter had foreseen references to the prior art section in the summary of the invention.

To read the whole decision, click here.

To download document D12, click here.