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19 December 2014EuropeSimon Kremer and Rachel Jones

Repurposed drugs: second time lucky

The drug discovery and development path for a new chemical entity (NCE) can take ten to 15 years and cost between $1 billion and $2 billion. ‘Repurposing’ is the practice of finding novel therapeutic indications for existing drugs. Typically the selected drug will have already been shown to be safe in patients, thereby significantly reducing the time it takes to bring the drug to market.

Indeed, it has been reported that repurposed agents are more than twice as likely across all disease indications to make it to market compared to NCEs. Furthermore, price support for a repurposed drug is in principle no different from that for an NCE, being likewise dependent on its substitutability and its clinical and economic advantages.

Policy makers, being aware of these benefits, have made efforts to encourage repurposing—for example the US National Institutes of Health has programmes aimed at utilising existing, partially developed therapeutic candidates in new disease indications. In the UK an ‘off-patent’ drugs bill was recently proposed, with one of its aims being to give generic drug makers new marketable indications for their products.

However, even if the repurposed drug in question is off-patent, bringing it to market is still a considerable challenge, and such an investment requires a clear exclusivity strategy. Unfortunately, clarity is something that is lacking when considering obtaining and enforcing patents in this field.

Patents—history and formats

In order to protect repurposed innovations, ‘second medical use’ patents are available in most territories, although notable exceptions exist including in India. The precise wording of such claims is a matter of national laws, but a bewildering array of formats is used. For example, in Europe two claim formats have been permissible:

  • Swiss form claim—Use of substance X in the manufacture of a medicament for the treatment of condition Y; and
     
  • EPC 2000 form claim—Substance X for use in the treatment of condition Y.

The Swiss form claim was first permitted in the landmark G5/83 decision by the European Patent Office’s (EPO) Enlarged Board of Appeal (EBA), which found that such claims could be granted “for a specified new and inventive therapeutic application, even in a case in which the process of manufacture as such does not differ from known processes using the same active ingredient”. As elsewhere, the patentability of Swiss form claims at the EPO is predicated critically on the new “purpose” (or “repurpose”) of the known medicament.

The EPC 2000 form claim was introduced in 2007, and was intended to match as closely as possible the scope of protection provided by a Swiss-type claim. Later the EBA decided that Swiss-type claims were in effect redundant in view of the new law, and would no longer be permitted in new applications. However, the very fact that the claims available to applicants are worded differently leads to uncertainty about their scope.

The UK courts have, to date, treated Swiss form claims as process claims, whereas EPC 2000 claims are purpose-related product claims. Although in some respects the difference may be academic, for example because the product obtained directly from the process claimed under the Swiss form claim may be protected in the same way as the product claimed under the equivalent EPC 2000 claim, in other contexts there may be key differences.

For example it is questionable whether the Swiss form claim actually requires that the recited drug be present in the final medicament (as is believed to be the case for the EPC 2000 form) or whether it could merely be present during the manufacture.

"The complex relationship between the claims has also led, arguably, to confusing practice at the EPO regarding applicants pursuing protection for both types of claim."

The latter argument was rejected in one UK case, based on particular facts, but certainly remains arguable. The complex relationship between the claims has also led, arguably, to confusing practice at the EPO regarding applicants pursuing protection for both types of claim. In one recent decision the EPO prohibited both types in the same application as the board of appeal was not persuaded that the claims were treated differently by national courts, whereas other appeal boards have said that the applicant had a legitimate interest in pursuing both types of claims, accepting that the protection offered was not identical.

Patentability

Irrespective of the format of the claim, a first hurdle for obtaining a patent for a new medical use for a substance is that the new use must be supported by evidence (in the application) that the substance is effective for the specified use. In some territories, such as the EPO, the burden is not a high one. Rudimentary tests may suffice and full, detailed and rigorous testing of the drug for the proposed condition is not necessary as long as the teaching is plausible. By contrast, in China, at least historically, examiners have required that the applications as filed provide more complete evidence of efficacy.

A second hurdle for applicants is to establish novelty and inventiveness over the previous use. For known drugs, there will usually be a considerable literature or history of testing in a therapeutic context. Again, the EPO and UK courts have frequently adopted a pro-patentee approach when assessing novelty. An earlier medical use should not anticipate a different, later one because, unlike other areas of patent law, the doctrine of inherency does not apply. Nevertheless there is a squeeze between these two requirements.

In claims to medical uses, “for” is typically taken to mean not just “suitable and intended for” but also that it imbues a requirement for a level of therapeutic efficacy. The effect of this is that such claims are generally regarded as novel over a mere proposal to administer the drug to patients in the manner claimed, because a mere proposal does not disclose that the treatment is efficacious.

However, the disclosure requirements placed on the application itself, and the potentially anticipatory prior art, should be a seamless fit—it cannot be argued that experimental data provides support for a claimed use but the same data does not anticipate it.

Enforcement

Obtaining claims of one type or another is only the first challenge for applicants in this area. An arguably greater difficulty arises in seeking to enforce them to protect the new market created by the approval of the known therapeutic for the new use. Purpose or intention can be a challenging concept when applied to a product or even an act, but it is nevertheless the defining technical feature of any form of second medical use claim.

The supply chain from manufacture (of the drug substance) to distribution, labelling, prescription and final use is likely to involve multiple parties, possibly in multiple jurisdictions, which may have disparate knowledge or intention regarding the final purpose of the medicament.

Where a drug is produced or marketed by a party with label instructions that describe a patented use, or is clearly adapted for that patented use (perhaps in terms of dosage or administration route), it may not be difficult in practice to identify infringement.

However a particular challenge arises in ‘cross-label’ use, whereby a medicament has regulatory approval for both a non-patented and a patented indication, and a generic version is marketed for the non-patented indication but then ultimately used for the patented indication.

To make matters worse, off-label (including cross-label) use may be officially sanctioned by authorities. For example the websites of the UK Medicines and Healthcare Products Regulatory Agency and the National Health Service provide guidance to doctors regarding off-label prescribing, with little or no reference to patents or IP. The French National Assembly recently backed a bill to let doctors use drugs off label even where alternative drugs are approved. The US Food and Drug Administration does not prohibit physicians from prescribing drugs for off-label uses, including patented uses.

Patentees are unlikely to wish to sue doctors and patients, and it may be challenging to show direct infringement by any party higher in the supply chain. In the absence of evidence of constructive or actual knowledge or intention by these other parties, for example based on sales volumes or promotional literature, a court may simply find the ‘skinny’ label is decisive that the medicament was not ‘intended for’ the claimed medical use.

In such cases it may be possible for the patentee to show ‘indirect’ infringement. Here it would be necessary to show that a party in the supply chain “knew”, or it would have been “obvious to a reasonable person in the circumstances”, that the products were to be used in an infringing manner. The developing case law in the UK around indirect (or ‘contributory’ infringement) has been surprisingly pro-patentee, allowing that even the knowledge or suspicion of probable infringement may be sufficient to find liability.

Nevertheless difficulties remain when applying this to second medical use claims, particularly Swiss claims where the infringing act itself would seem to be focused on the manufacture, rather than final use. In these cases it may be necessary to look at the possibility of ‘joint tortfeasorship’ and seek to demonstrate that multiple parties in the chain were acting in a concerted fashion or common design to infringe the claims. But again, this can provide evidentiary difficulties for patentees.

Another legal strategy for patentees trying to identify infringement in a supply chain is to show inducement of infringement, for example by suppliers seeking to influence health providers. However in the UK there is no tort in merely facilitating an infringing act and the evidentiary burden to demonstrating induction or procurement of such an act is likely to be high.

Interestingly the recent US Supreme Court decision of Limelight Networks, Inc v Akamai held that there can be no liability for induced infringement when there has been no direct infringement. Since the final healthcare providers in the chain may benefit from statutory defences to infringement, or may not in any case perform all the required steps in a medical use claim, there are likely to be some considerable challenges for patentees seeking to demonstrate inducement in the context of medical use claims.

Drug repurposing will be increasingly important for finding new cures in years to come, so it is very important that exclusivity strategies, including patent strategies, exist to provide incentives for companies to innovate in this area. If society is to benefit from

new treatments for diseases based on existing drugs, it will be in everyone’s interests that greater clarity and uniformity are brought to this complex and inconsistent area of patent law.

Simon Kremer is a partner at Mewburn Ellis. He can be contacted at: simon.kremer@mewburn.com

Rachel Jones is a patent attorney at Mewburn Ellis. She can be contacted at: rachel.jones@mewburn.com