Scientists, clinicians, and other investigators are discovering new uses for drugs previously known for different medical indications. Such “drug repurposing” (also called drug repositioning, profiling, or re-tasking) has great potential for providing clinicians with new therapeutic tools to combat diseases for which there are limited or no treatments available.[1]
Despite these implications, commercialization of repurposed drugs has little chance for success without patent protection that can attract funding and promise a reasonable return on investment. Investors such as angels, venture capitalists, and others (e.g., research institutions, interest groups, etc.) are reluctant to pour capital into companies focused on repurposing drugs that are known chemical compounds for two main reasons. First, repurposed drugs are typically only patentable using method of treatment (MOT) claims (e.g., “a method of treating disease X, comprising administering a therapeutically effective amount of drug Y”) rather than composition of matter claims (e.g., “a composition, comprising drug Y”) because, although the MOT is presumably new, the repurposed drugs themselves are not. Second, MOT patents are less valued because they can potentially be more difficult to police for infringement (when it occurs, and who is the culprit), and infringement can be harder to prove. Yet, contrary to the conventional wisdom that MOT patents are second-tier to composition patents, companies are repurposing drugs, protecting them with MOT patents, and realizing significant successes for their efforts.
Some of the world’s most successful drugs were actually discovered through repurposing efforts and are or were at least originally protected only by MOT patents. For example, minoxidil (marketed as Rogaine®[2]) was first developed as a vasodilator, but it was repurposed to treat hair loss and generated over $700 million in sales for Upjohn by patent expiry in 1996[3]. Similarly, sildenafil (marketed as Viagra®[4]) was originally developed to treat angina, but it was repurposed to treat erectile dysfunction. Viagra reached global sales over $2.05 billion in 2013.[5] Atomoxetine[6] (marketed as Strattera®) was originally indicated as a therapeutic for Parkinson’s disease, but it was repurposed to treat attention deficit hyperactivity disorder (ADHD), with sales reaching upwards of $855 million in 2016.[7] Similarly, rituximab was primarily intended to treat different types of cancers, but it was repurposed to treat rheumatoid arthritis (marketed as Retuxan®[8]) with sales topping $7 billion in 2014.[9] A more recent example is dextromethorphan (marketed as Nuedexta®) by Avanir Pharmaceuticals for the treatment of pseudobulbar affect.[10] Dextromethorphan is one of the two active ingredients in Nuedexta, and also happens to be one of the primary ingredients of the age old cough-suppressant Robitussin®. Nuedexta is protected by three MOT patents[11] and has brought in hundreds of millions of dollars leading “Otsuka Holdings of Japan to purchase Avanir in 2014 for $3.5 billion.”[12]
Hoping to follow in the footsteps of these giants, new companies like Biovista, Recursion Pharmaceuticals (Recursion), Roivant Sciences (Roivant), and others are focused on repurposing known drugs as a business model. For example, Biovista applies a “systematic discovery Artificial Intelligence platform to develop [a] pipeline of repositioned drug candidates in disease areas such as neurodegenerative diseases, epilepsy, oncology and orphan diseases.”[13] Biovista currently boasts their own patent portfolio which includes multiple patents and applications whose first and broadest claim is a novel method of treatment.[14] Similarly, Recursion is successfully using machine-learning drug discovery to predict the safety of chemical entities.[15] As of 2019, Recursion “secured $121 million in new financing for its artificial intelligence programs.”[16] Roivant is particularly interesting as it is a parent company that creates new subsidiaries around the drugs it aims to repurpose.[17] Although some of Roivant’s subsidiaries are more successful than others[18], in 2017, the company raised over a billion dollars in funding from SoftBank.[19] Clearly, there is a multifaceted market for repurposed drugs protected by MOT patents. So why are these companies successful when their IP is based on seemingly problematic MOT patents?
To answer this question, first consider the following limitations for MOT patents: (1) they have a more limited claim scope than composition patents; (2) they can be more difficult to enforce in an infringement action; and (3) a patent is not a right to practice, but only a right to exclude, as such, an enforceable composition patent on the repurposed drug itself can block the new MOT patent holder from practicing the method. Each of these issues is discussed below.
First, a MOT patent does not have the same scope as a composition patent on the same compound.[20] As scholars explain:
[Product claims covering the compound] have always been the premium form of patent protection in the chemical industry. … A claim to the compound, per se, dominates every method of making that compound and every single use of that compound, every single mixture of different components that includes that compound, and every end use composition inclusive of the compound.[21]
Despite this, the more limited claim scope for a MOT patent is not necessarily problematic. New methods of treatment with a repurposed drug for a particular disease create exclusive and new markets for the repurposed drug. The fact that others may be using the same chemical compound for different reasons is not particularly relevant, because those uses would not be competing for the repurposed drug company’s exclusive market share protected by the MOT patent. The primary use of the compound that matters is for the new treatment of a disease, and a MOT patent protects precisely that.
Second, unlike a patent on an apparatus or a compound, method claims consist of one or more steps to be performed. To impose liability for direct patent infringement[22], a plaintiff must prove that the defendant(s) performed every step articulated in the claim.[23] Thus, depending upon how a MOT claim is written, a patient could be performing one or more steps necessary to constitute an act of direct infringement (e.g., obtaining a drug X and/or administering the drug X). However, suing patients for patent infringement is commercially untenable.[24] Despite this limitation, there are options for MOT patent enforcement.
One option is the possibility of suing the prescribing physician, the pharmacist who provided the repurposed drug in the appropriate dosage, or some other actor under a divided infringement theory[25] and/or under an induced infringement theory.[26] Although Congress, under 35 U.S.C § 287(c), carved out certain immunity for physicians from patent infringement while performing “medical activities,” “[the] defense does not cover the practice of a patented use of a composition of matter ….”[27] So, it is possible to enforce a MOT patent against a physician as an induced infringer; but again, it may not make good business sense to do so, unless there is a large number of infringing physicians, which could suggest a central actor. An ideal target for enforcing a MOT patent would be a rival...
