The Patentability of Enantiomers

Alphapharm Pty Ltd v H Lundbeck A/S [2008] FCA 559

http://www.austlii.edu.au/cgi-bin/sinodisp/au/cases/cth/FCA/2008/559.html?query=^alphapharm

In a lengthy decision by Justice Lindgren (214 pages), his Honour has provided an assessment of whether enantiomers are patentable as at 1988. The following paragraphs regarding obviousness are illustrative.

“[381] In Astra, the High Court described (at [53]) the reformulation of the
“Cripps question” by Graham J in Olin at 187-188. Their Honours stated
that that approach should be accepted. Adapting that test to the
circumstances of the present product claims, I would state the test as follows:

Would the hypothetical addressee or team as at 14 June 1988, equipped with the
Australian Citalopram Patent and possessed of the common general knowledge
within the field at that time, adopt as a matter of routine the aim of obtaining
the (+)-enantiomer of citalopram in the expectation that it might well produce a
useful alternative to, or a better drug than, citalopram?

While I think that the hypothetical addressee or team in 1988 would have recognised the possibility of an advantage in obtaining the enantiomers because of the possibility of the therapeutic benefits of the racemate being found to reside in one of them, I do not think that the goal of obtaining the enantiomers would have been adopted as a matter of routine, as is required for the Australian test of obviousness to be satisfied.”

The following paragraphs provides context in which the Cripps question was
assessed:

“[224] There was some dispute over whether the common general knowledge in relation to (e) included knowledge that one enantiomer may in fact have antagonistic effect, with the result that the therapeutically active enantiomer, once it was isolated, would have greater beneficial effect than the racemate. Professor Day said that this was part of common general knowledge in 1988, but Professor Montgomery disagreed. The preponderance of the evidence is that the general understanding was that at the most, all of the therapeutic benefits of the racemate could reside in one enantiomer, and that the other enantiomer was mere “ballast”. While some skilled addressees may have known of the possibility of antagonistic effect from the other enantiomer, I am not persuaded that this knowledge was part of common general knowledge in 1988.

…

[394] While I accept that it was part of the common general knowledge that one enantiomer might possess all of the pharmacological activity of the racemate, as previously noted I am not persuaded that it was part of common general knowledge that obtaining the enantiomers might offer more than the same therapeutic effects for half the dosage.

…

[416] While accepting that there is no way of predicting the ease or success of resolution, Professor Banwell stated that “there are methods for resolution available at modest cost that would be worth trying”. Professor Banwell’s evidence went only so far as saying that the relevant addressee would explore the possibility of resolution, with an expectation that the two enantiomers might have differing behaviours in biological systems. He did not go so far as to say that the skilled addressee would be led directly to desire to obtain the enantiomers in the expectation that one would or might well be more effective than the racemate.”