In 2015, a Japanese-origin Santen Pharmaceutical Co., Ltd. (hereafter Santen) obtained a patent right (KR101536885) for a remedy for dry eyes (product name: DIQUAS (registered trademark) ophthalmic solution 3%) from the Korean Intellectual Property Office (hereafter KIPO). Two years later, Sam Chun Dang Pharm (hereafter Sam Chun Dang) and other well-known pharmaceutical companies, such as Chong Kun Dang pharmaceutical (hereafter Chong Kun Dang), Kukje pharma (hereafter Kukje), Samil pharmaceutical (hereafter Samil) and Intro Biopharma, filed an opposition proceeding over the patent in order to revoke their patent right. In particular, as of 31 May 2017, when Hanmi Pharmaceutical (hereafter Hanmi) filed an opposition action, the Intellectual Property Trial and Appeal Board (hereafter IPTAB) partially invalidated the claims (from claim 1 to claim 8), and Hanmi again challenged the rest of the claims before the Patent Court, thereby invalidating the claim 9, 10 and 11. Finally, the IPTAB concluded the case in February this year by maintaining its first instance ruling.
Claims at issue:
KR 101536885 (B9): DIQUAFOSOL-CONTAINING EYE DROP
Claim 9) A method for producing an aqueous ophthalmic solution comprising diquafosol or a salt thereof at a concentration of 3% (w/v) and for use in application to corneal epithelium disorder found in a dry-eye patient, comprising the step of mixing diquafosol or a salt thereof and a chelating agent in an amount that causes a final concentration of the chelating agent in the aqueous ophthalmic solution to be 0.001 to 1% (w/v), to obtain an aqueous solution in which formation of insoluble precipitates is inhibited.
Claim 10) The method according to claim 9, further comprising the step of filtering the obtained aqueous solution through a filtration sterilization filter having a pore size of 0.1 to 0.5 μm.
Claim 11) A method for inhibiting formation of insoluble precipitates in an aqueous ophthalmic solution comprising diquafosol or a salt thereof at a concentration of 3% (w/v), and for use in application to corneal epithelium disorder found in a dry-eye patient, by adding a chelating agent at a concentration of 0.001 to 1% (w/v) to the aqueous ophthalmic solution, where a chelating agent is edetate or a salt thereof.
As mentioned before, the domestic pharma-corporations filed several opposition trials against Santen before the IPTAB, where the following ruling in the first instance filed by Hanmi was made on the basis that the claims at issue complied to the description requirements in accordance with Articles 42 paragraph(3)1 and paragraph(4)1 of Korean Patent Act.
“It is difficult to mention that the amended claims are not supported by the description of the invention and do not reproduce the effects of the revised claims from 9 to 11 in this case merely because the effect of inhibiting the formation of insoluble precipitates in an aqueous ophthalmic solution that does not contain benzalkonium chloride in the amended description is not clearly written, and the request of plaintiff, a lack of the description sufficiency, cannot be accepted from the statement of the evidence 6 in which only the insoluble precipitates resulted from belzalkonium chloride are not supported by the amended description of the invention (darts-387-410-F-ko).”
Accordingly, Hanmi appealed to the patent court for the remaining claims to be revoked, where the court decided to reverse the decision on claim 9 to 11 due to lack of inventive step as follows.
“The amended invention in claim 9, 10 and 11 shall be invalidated as the inventive step of the skilled person can easily derive by combining the prior art 1 and 2 with the well-known technology, thereby not satisfying the inventive step (darts-358-208-H-ko).”
Finally, the IPTAB concluded the case, eventually retaining the initial ruling from the first instance filed by Hanmi (darts-208-945-I-ko).
Meanwhile, the parallel invalidity proceedings filed by Sam Chun Dang, Kukje, Samil, Intro Biopharma and Chong Kun Dang, were ruled in favor of the appellants, primarily focusing on the inventive step insufficiency of the whole claim before the IPTAB and the patent court.
This lawsuit is noteworthy as it was the first time for South Korean pharmaceutical companies to succeed over a foreign pharmaceutical company in respect to patent opposition trials. Until now, many national conglomerates producing and selling an ophthalmic solution have challenged Santen’s patent, however, Korean authorities usually had been ruling in favor of the original firm, resulting in maintaining the patent.
In the meantime, apart from the patent opposition actions, Santen filed a divisional patent application in July. Yet, Chong Kun Dang was able to acquire generic exclusivity to sell a Diquabell, a generic of DIQUAS, even before their divisional application. Nonetheless, they are middle of challenging Santen’s remaining subject-matters as well.
In conclusion, the divisional patent application has not yet been completely invalidated for the use of DIQUAS, but it should be pointed out that Chong Kun Dang is manufacturing a generic product and domestic pharmaceutical companies have taken a lead by invalidating Santen’s initial patent. Next, attention will be paid to the validity of the remaining patent, and it is expected for South Korean pharmaceuticals to play a bigger role in the ophthalmic solution generic market.
 The claims have been amended on 29th June 2018.
 Patent Act
Article 42(3)1: to clearly detail the invention in such manner that any person with ordinary knowledge in the technical field of the relevant invention can easily practice the invention;
Article 42(4)1: the invention shall be supported by the description;