Patent not enforceable – Inequitable Conduct

Patent not enforceable - Inequitable Conduct

This case relates to an infringement case in US for infringement of Apotex’s US6767556  patent for moexipril tablets for hypertension by UCB’s accused UCB’s Univasc® and Uniretic® products. The district court observed that due to inequitable conduct the said patent is not enforceable. The case was escalated by Apotex to Federal circuit which upholds the District court decision. The reasons for court decision have been described herein in the article.

Patent not enforceable - Inequitable Conduct

Inequitable Conduct

Habit of charging inequitable conduct in almost in every major patent case has become an absolute plague. In a prosecution system and during litigation the patent validity depends upon the quality of information available to examiner during the prosecution of the respective patent application. It is essential for the patent applicant to disclose the entire relevant prior art. The federal circuit has emphasized on this by stating that the highest standards of honesty and candor on the part of patent applicants in presenting all the prior art facts to the office are thus essential elements for an effective working patent system. In US the duty to disclose the relevant prior art information is enforced during patent litigation through the defense of inequitable conduct. When successfully asserted this defense prevents a patent owner who knowingly withholds the relevant information from enforcing his or her patent and can be revoked.
Recently Federal circuit upholds inequitable conduct defense against Apotex patent. Apotex’s patent US6767556 pertains to a method of making tablets of moexipril, which is an ACE inhibitor used to treat hypertension.


The indecent claim is:
A process of making a solid pharmaceutical composition comprising moexipril magnesium, said process comprising the step of reacting moexipril or an acid addition salt thereof with an alkaline magnesium compound in a controlled manner in the presence of a sufficient amount of solvent for a predetermined amount of time so as to convert greater than 80% of the moexipril or moexipril acid addition salt to moexipril magnesium.

According to federal court  – moexipril is “susceptible to degradation and instability.” The ’556 patent addresses this problem by “making moexipril tablets consisting mostly of moexipril magnesium obtained by reacting moexipril or its acid addition salts with an alkaline magnesium compound.” According to the patent, “the reaction cannot be accomplished in dry form and must be carried out in the presence of a solvent ” using “wet granulation” methodology that “has been known in the pharmaceutical industry since at least the 1980s.”

The Apotex had filed an infringement against accused UCB’s Univasc® and Uniretic® products, which were prior art to the ’556 patent. Other prior art included U.S. Patent 4,743,450 which was listed in the Orange Book for the UCB products and discloses a process that “involves the wet granulation of moexipril hydrochloride and magnesium oxide.” The ’450 patent had cited a 1990 article by Gu et al. that discussed the mechanism by which alkaline stabilization of moexipril might occur.
During prosecution of ‘556 patent inventor Dr. Sherman who is chairman of Apotex, distinguished the prior art by asserting that the prior art taught the use of an alkaline compound stabilizer in the final, solid product, while the claimed methods in ‘556 taught reacting moexipril with an alkaline magnesium compound to form moexipril magnesium.
As per inventor of ‘556 the prior art ‘450 teaches the stabilization of the solid moexipril by adding an alkaline stabilizer and characterizes Gu as being “consistent with” the ’450 patent and teaching. As per inventor of ‘456 only the small portion of outer surface of the granules may get converted into magnesium salt and in no way teaches the formation of a magnesium salt. The applicant asserted and emphasized these alleged differences throughout prosecution.

The applicant submitted an expert Declaration attesting that a “stabilizer” (as disclosed in the prior art ’450 patent) would remain unreacted to perform its intended function. Thus, a person of ordinary skill in the art “would … not expect a reaction to occur between the moexipril molecule and the alkaline stabilizer disclosed in the ’450 patent.”

The Examiner’s Reasons for claim allowance indicate that the patent was allowed on the basis of that alleged distinction. The Examiner got convinced that that the prior art does not disclose nor suggest a process of making a pharmaceutical composition comprising moexipril magnesium formed by a reaction step comprising the reacting moexipril or an acid addition salt thereof with an alkaline magnesium compound so as to convert greater than 80% of the moexipril or moexipril acid addition salt to moexipril magnesium. Instead, the prior art teaches that only a portion of may be converted to the alkaline salt and that the stable product results entirely or primarily not from conversion to alkaline salts, but from stabilization of the moexipril hydrochloride by the presence of the alkaline stabilizing compound in the final product.

The US court observed that the ’556 patent “is unenforceable due to Dr. Sherman’s inequitable conduct . The court found that Dr. Sherman was aware that Univasc was made according to his claimed process, concealed this knowledge from the PTO, and misrepresented the nature of Univasc and the prior art through his counsel’s arguments and that Dr. Sherman withheld relevant prior art and submitted results of experiments that he never conducted.

For example, shortly after the patent application was filed, “two Apotex scientists … produced a detailed mass spectrometry report on Univasc and concluded that moexipril in Univasc is ‘mainly present’ as moexipril magnesium,” but that information never was disclosed to the Patent Office. On the other hand, the patent included examples written in the past tense.
The court found that the misinformation and withheld information was “but-for” material and, in the alternative, that Dr. Sherman had engaged in “egregious misconduct during prosecution.” With regard to intent, the court found that “the single most reasonable inference that could be drawn from the evidence was that Dr. Sherman intended to deceive the PTO.”

The Federal Circuit decision was authored by Judge Reyna and joined by Judges Wallach and Hughes.

An IPR expert for patents in respect of technology landscaping, patent-ability analysis, patent application drafting and prosecution in all global jurisdictions, infringement analysis, freedom to operate opinion, patent invalidation, pre grant and post grant opposition etc.  He can be reached at Charanjit.sehgal (at) Hand Phone +919594993301


This site uses Akismet to reduce spam. Learn how your comment data is processed.