Physiological Steps Doctrine

35 Pages Posted: 15 Mar 2009

See all articles by Andrew W. Torrance

Andrew W. Torrance

University of Kansas School of Law; MIT Sloan School of Management

Date Written: March 13, 2009


In vivo conversion is a process, often metabolic in nature, wherein one substance, usually a chemical compound, is altered significantly by physiological pathways in the body into one or more different substances. For example, when a patient ingests a therapeutic drug, that drug is often converted by the natural physiology of the digestive system into one or more chemically different metabolites. The end products of in vivo conversion sometimes possess therapeutic efficacy. Many patent applications have claimed such therapeutic metabolites, either as compositions per se or as parts of methods of treatment. Although the USPTO has granted patent claims to such products generated by in vivo conversion of ingested drugs, and courts have noted the eligibility of such products as patentable subject matter, never has a United States court of final appeal upheld such a patent claim as valid, enforceable, and infringed. The unanimity of results in cases involving patent infringement triggered by in vivo conversion is striking. In fact, its very improbability suggests a common underlying explanation for why in vivo conversion does not ever seem to trigger patent infringement. Explanations based on inherency or a lack of evidence provide a satisfactory explanation for only a minority of in vivo cases. The Physiological Steps Doctrine, which suggests that products and processes of in vivo conversion are unpatentable subject matter under U.S. patent law, offers an explanation that spans all in vivo conversion cases. Though the rationales offered to explain the results in a number of in vivo conversion cases are suggestive, there are several advantages for a more explicit recognition of the Physiological Steps Doctrine. Consistent with much international, European, and U.S. patent law, the Physiological Steps Doctrine provides a theoretical underpinning to explain the results in cases involving products and processes of in vivo conversion. This theoretical underpinning not only has explanatory power for interpreting previous case law but is also useful in predicting the outcome of future in vivo conversion cases. In addition, the Physiological Steps Doctrine increases the understanding of where inventions involving human beings, and the biological products and processes thereof, fit within the spectrum of patentable subject matter.

Keywords: Patent, pharmaceutical, drug, biotechnology, in vivo conversion, prodrug, statutory subject matter, patentability, patentable subject matter, mental steps doctrine, physiological steps doctrine, abbreviated new drug application, ANDA, generic drug, inherency, evidence

JEL Classification: K00, K10, K11, K19, K20, K23, K29, K30, K32, K39, K40, K41, K42, K49

Suggested Citation

Torrance, Andrew W., Physiological Steps Doctrine (March 13, 2009). Berkeley Technology Law Journal, Vol. 23, pp. 1471-1505, 2008, Available at SSRN:

Andrew W. Torrance (Contact Author)

University of Kansas School of Law ( email )

Green Hall
1535 W. 15th Street
Lawrence, KS 66045-7577
United States

MIT Sloan School of Management ( email )

100 Main Street
Cambridge, MA 02142
United States

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