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30 November 2020
Claim mining is a technique by which a later inventor can work around the claimed patented invention. Knowingly or unknowingly, inventors look for a successful prior art or a prior patent and work on the difficulties left unresolved by the prior inventor(s).The difficulties in any patented invention are reflected by the way the claim limitations are cleverly drafted. When any later inventor looks for a solution in the same field, he sees to it that he avoids the prior disclosure and clearly distinguishes the invention from the prior art.
The difficulty of enforceability of broad claims make it rather easy for the drafter of claims to cleverly bring out any limitations so anticipated. However, it leaves a possible gap for a later inventor to capture the patent during the marketing of the product. It is understood that literal infringement does not occur in the case of the marketed product for infringement purposes if it falls outside the claims. This type of working around the claimed patented invention for the purpose of marketing is visible and prevalent in the United States in particular, where generic pharmaceutical companies are permitted to apply for Food & Drug Administration approvals before the expiry of the target patent. Where patent claims are based on the physical form of the compound or special properties which link thereto, the generics companies normally venture to market the product not covered by the targeted patented claims. Enforcement of such claims are fraught with difficulties where the patentee surrender the broad claims to avoid patentability rejections and settle for self-imposed limitations.
To illustrate this point let us look at the proceeding in Bayer AG v. Elan Pharmaceutical Research Corp. [212 F.3d 1241]. Relating to US Patent No. 5,264,446 on sustained release of nifedipine owned by Bayer AG and Bayer Corporation. This patent claimed a pharmaceutical composition that contains nifedipine crystals of a defined specific surface area (SSA). Claim 1, which Bayer asserted against Elan, recites the broadest SSA range: “1. A solid pharmaceutical composition comprising as the active ingredient an effective amount of nifedipine crystals with a specific surface area of 1.0 to 4 m2/g, in admixture with a solid diluent, to result in a sustained release of nifedipine.”
Elan, on the other hand, asserted that their composition only covered nifedipine crystals of a SSA of 5 m2/g or greater. Elan submitted to FDA that it intended to measure the SSA of its nifedipine no more than five business days before tablet manufacture and that it would discard any nifedipine having a SSA of less than 5 m2/g.
Interestingly, during prosecution, Bayer had surrendered claim coverage to nifedipine crystals beyond the range of 1.0 to 4 m2/g SSA. Bayer’s amendment changing Claims 1, 2, and 3 from a SSA range of 1.0 to 6 m2/g to 1.0 to 4 m2/g and Bayer’s general arguments for patentability clearly established this.
The court concluded that Bayer’s amendment to a SSA range of 1.0 to 4 m2/g was an attempt to overcome an obviousness rejection and that Bayer had made statements that constituted a “clear and unmistakable surrender” of subject matter outside of the claimed range of 1.0 to 4 m2/g.
In view of these facts court held: “We believe that the specification in Elan’s ANDA mandates a finding of no literal infringement. Elan’s specification indicates that ‘the specific surface area of the micronized nifedipine is to be 5 m2/g or greater,’ and that this SSA ‘will be reflected in certification of analysis provided by Elan’s supplier (AWD).’ Elan further defines its specification by noting that it is ‘Elan’s intention to measure specific surface area on the micronized Nifedipine material prior to use (within 5 working days prior to blend manufacture) to ensure that the 5 m2/g specification for specific surface area is met. Material not meeting this specification will not be used for manufacture.’
The court continued: “Thus, according to Elan’s ANDA specification, nifedipine used in its drug cannot have a SSA of less than 5 m2/g within five working days prior to manufacturing. Significantly, Bayer does not allege that within five working days, the nifedipine’s SSA will decrease from 5 m2/g to a literally infringing size of 4 m2/g or less. Therefore, under the ANDA specification, Elan cannot literally infringe the ‘446 patent.”
In an earlier case, Pharmacia & Upjohn Co. v. Mylan Pharmaceuticals [170 F.3d at 1376-79], that was relating to certain pharmaceutical formulations of the anti-diabetic drug glyburide where Upjohn alleged that Mylan’s commercial manufacture and sale of two of the accused products constituted infringement of Upjohn’s US Patent No. 4,916,163. During the proceedings, Upjohn acknowledged that Mylan has not literally infringed the ‘163 patent and relied on the doctrine of equivalents to assert the infringement.
Interestingly, in this case also, the patentee argued that the use of spray-dried lactose was “a critical feature” of the claimed invention and that using lactose that was not spray-dried resulted in a pharmaceutical powder that was not readily processed.
In view of that, the court concluded that the patentee had relinquished claim coverage to any type of lactose that was not spray-dried. The court held that the commercial manufacture, use and sale of Mylan’s micronized glyburide products do not infringe on the ‘163 patent, since these products do not contain spray-dried lactose as required by the ‘163 patent claims.
A patent claim of a compound by reciting its chemical structure is the most desirable type of claim. Such claim is considered a claim to the chemical per se, and it is easy for a court to construe such claims. It is generally believed and understood that such a claim would be literally infringed by any physical form of the chemical. Such claims are preferred for new chemical entities. Working around such a claim is rather difficult and fraught with application of the doctrine of equivalence by the courts.
However, the trend of patenting activity has now shifted to improvements of old products rather than looking for new entities. In the race to get more patents, the patentee seeks to get patents for every possible physical form of a compound that may also be important to the properties of disclosed and claimed chemical compositions. However, this tactic leaves sufficient space for the claim miners to work around the invention and capture the market space left open. If sufficient care is not taken during claim drafting and prosecution, claim miners can take advantage and market the product before expiry of the patent.
