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Legal Issue 2. |
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IP Issue Update |
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Patent Covering Method of Use for Viagra Confirmed Invalid by the Korean Supreme Court |
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| On April 23, 2015, the Korean Supreme Court upheld a High Court decision confirming the invalidation of KR Patent Reg. No. 10-0262926 ("KR'926"), a patent covering a method of use for Viagra, Pfizer's global blockbuster drug for treatment of erectile dysfunction. The composition of matter patent covering Viagra, KR Patent Reg. No. 10-0078931, was filed on June 19, 1991 (claiming priority to GB 9013750 filed on June 20, 1990) and expired on May 18, 2012 with a patent term extension of 10 months and 28 days. The original invalidation action against KR'926 was initiated by CJ, Hanmi Pharmaceutical and six other Korean pharmaceutical companies. |
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Background Facts |
| "Viagra" is the trade name for "sildenafil," which was initially developed for treating high blood pressure but was unexpectedly found to be effective for treating erectile dysfunction. Viagra's positive effects on erectile dysfunction were only discovered after Viagra was developed as a vasodilator, and the method of use patent application was filed in Great Britain on June 9, 1993, almost 3 years after the filing date of the composition of matter patent. The method of use patent KR'926 issued from KR Appln. No. 10-1999-7001541 filed on February 20, 1999, which was a divisional application of KR Appln. No.10-1995-7005553 filed on December 8, 1995 and claiming priority to PCT/EP94/01580 filed on May 13, 1994 and GB 9311920 filed on June 9, 1993. |
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| The specification of KR'926 identifies sildenafil as one of nine compounds used for erectile dysfunction treatment. However, the specification of KR'926 did not disclose any in vitro pharmacological data or experimental results specifically directed to sildenafil. In particular, the specification of KR'926 identified nine chemical compounds including sildenafil as "[e]specially preferred individual compounds" at pp.7-4 - 7-5 as follows: |
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| The compounds of the invention have been tested in vitro and found to be potent and selective inhibitors of the cGMP-specific PDEV [in reference to the predominant PDE in human corpus cavernosum tissue] |
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| Thus relaxation of the corpus cavernosum tissue and consequent penile erection is presumably mediated by elevation of cGMP levels in the said tissue, by virtue of the PDE inhibitory profile of the compounds of the invention. |
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| In man, certain especially preferred compounds have been tested orally in both single dose and multiple dose volunteer studies. Moreover, patient studies conducted thus far have confirmed that one of the especially preferred compounds induces penile erection in impotent males. |
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| All parties argued extensively over whether such a disclosure could be acknowledged as a test example or a concrete description that could replace the test example. |
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Decision |
| The Korean Supreme Court stated that a method of use invention of a pharmaceutical product requires disclosure of pharmaceutical efficacy. If there are no special circumstances, such as pharmaceutical efficacy clearly known before the patent application, the description requirement could be satisfied by disclosing test examples showing pharmaceutical efficacy data for a specific compound or by providing a concrete description that could replace the aforementioned test example. |
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| Furthermore, where the method of use invention requires disclosure of pharmaceutical efficacy and where there is neither pharmaceutical efficacy data for a specific substance nor a concrete description in the specification, a supplementing revision would not be permitted for violating the scope of such a description. The decision confirmed the precedent that an insufficient description cannot be corrected without losing the claim for priority to the originally filed documents. |
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| Ultimately, the Court held that it was unable to find sufficient support for a method of treatment for erectile dysfunction when examining the originally filed specification, because the specification lacked information typically required for medical treatment, e.g., dosage range, administration method, scope of the target group, evaluations of the erections, and medical state of patients before and after erection. In addition, the Court held that it is unclear from the specification whether the one especially preferred compound identified as inducing penile erection in the in vitro test is actually sildenafil. Thus, the Court held that there was neither pharmaceutical efficacy data for a specific compound nor a concrete description. |
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Lessons and Implications |
| This case clearly illustrates the importance of the sufficient written description requirement. The Korean Supreme Court views patent specifications as scientific and technical documents that must support the full scope of the claims, including claims directed to a method of use or a method of treatment. As a result of the court decision, all pharmaceutical companies are now free to supply generic versions of Viagra. In particular, generic drug manufacturers may now use the sufficient written description requirement as another potent legal basis for invalidation in patent challenges. Such patent challenges have dramatically increased after the March 2015 effective date of the Korean Drug Approval – Patent Linkage System, which is the Korean version of the US Hatch-Waxman Act. The Korean Drug Approval – Patent Linkage System provides the incentive of generic exclusivity to the first company that invalidates a listed patent or receives a determination that its generic product is outside the scope of a listed patent, also known as negative patent scope trials. |
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