Nature Medicine has an update on the deuterated drug landscape. There are several compounds in the clinic, and the time to the first marketed deuterium-containing drug is surely counting down.
But, as mentioned at the end of that piece, another countdown that also must be ticking away is the one to the first lawsuit. There are several places where one could be fought out. The deuterated-drug landscape was the subject of a vigorous early land rush, and there are surely overlapping claims out there which will have to be sorted out if (when) the money starts to flow from the idea. And there's the whole problem of obviousness, a key patent-killer. The tricky thing is, standards of what is obvious to one skilled in the art change over time. They have to change; the art changes. (I'll risk some more gritted teeth among the readership by breaking into Latin again: Tempora mutantur, nos et mutamur in illis.
We've already seen this with respect to single enantiomers - it's now considered obvious to resolve a racemic mixture, an to expect that the two isomers will have different activities as pharmaceuticals. At what point will it be considered obvious that deuteration can improve the pharmacokinetics? If that does ever happen, it'll take longer, because deuteration is not as simple a process as resolution of a racemate. Itt can be difficlut (and, well, non-obvious) to figure out where to put the deuteriums for maximum effect, and how many need to be added. Adding them is not always so easy, either, which brings up questions of enablement and reduction to practice. You need to teach toward the compounds you want to claim, and for deuteration, that's going to mean getting pretty specific.
There's another consideration that I hadn't been aware of until this weekend. I had the chance to talk with a patent attorney at a social gathering (not everyone's idea of a big Saturday night, admittedly, but I enjoyed the whole affair). He was explaining to me a consequence of the Supreme Court's recent ruling on obviousness, the 2007 KSR v. Teleflex decision. Apparently, one of the major effects of that ruling was the idea that if there are a limited number of known options for an inventor to choose from, that can take the whole thing into the realm of the obvious. The actual language is that when ". . .there is a design need or market pressure to solve a problem and there are a finite number of identified, predictable solutions, a person of ordinary skill has good reason to pursue the known options within his or her technical grasp. . .the fact that a combination was obvious to try might show that it was obvious under § 103". You can see the PTO itself trying to come to grips with KSR here, and it seems to be very heavily cited indeed by examiners (and in subsequent court cases).
Naturally, as with legal matters, the big question becomes exactly what a limited number of options might mean. How many, exactly, is that? In the case of a racemate, you have two (only two, always two), and it's certainly reasonable to expect them to be different in vivo. So that would come under the KSR principle, I'd say, and it's not just me. But what if there are a limited number of places that a deuterium can be added to a molecule? At what point does deuterating them become, well, just one of those things that a person skilled in the art would know to try?
Expect a court case on this eventually, when some serious money starts to be made in the area. This is going to be fought out case by case, and it's going to take quite a while.