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posted by martyb on Friday April 07 2017, @05:09AM   Printer-friendly
from the receives-glowing-reviews dept.

The first deuterated drug has finally been approved by the FDA. It's Austedo (deutetrabenazine), from Teva, and it targets Huntington's chorea. This is an interesting development on several levels. The idea of adding deuteriums (instead of plain hydrogens) to drug structures had been kicking around for many years, but only in the last 8 or 10 years has serious development been underway on them.

[...] Deuterium is the (fairly well known) "heavy hydrogen" isotope of regular hydrogen, which is heavy because it has another neutron in it. That basically doubles its weight (the single electron in the atom is a roundoff error in that regard), so these two are an isotope pair with a large percentage difference in weight indeed.
[...] The reason this weight difference makes a difference is when a bond breaks between the hydrogen (or deuterium) and another atom. The bond is actually harder to break with the heavier isotope, an effect that can be modeled surprisingly well with springs and fishing weights. This is the "primary kinetic isotope effect", and if that bond-breaking is an important step in some process, you can slow the whole works down by just putting in a D where an H used to be. For drugs, the key is that many of them are metabolized and destroyed when they hit they liver, and this is often done through breaking a C-H bond. So a well placed deuterium (or two, or three) can actually have a significant effect on how long a drug will circulate in the bloodstream, by slowing down the liver's clearance mechanism.

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  • (Score: 3, Informative) by Joe on Friday April 07 2017, @01:35PM

    by Joe (2583) on Friday April 07 2017, @01:35PM (#490206)

    non-deuterated form, tetrabenazine, is not as free of side effects/warnings as one may expect

    I don't know of anyone, who has any knowledge of the subject, that would expect a drug to be free of side effects. As for side effects, some are caused by on-target toxicity (too much inhibition of a therapeutic target) or off-target interactions of the active compounds while others are caused by specific metabolic products of the parental or active compound. Deuteration of a drug has the ability to limit off-target and metabolic based side effects, but not dose toxicity.

    the deuterated form may be or may be not more effective [...] it's likely we're going to see "deuterated aspirin"

    In the case of aspirin, the side effects are caused by the active compound (salicylate) so there is potential to limit off-target toxicity.

    Effectiveness is an entirely different story: deuteration may be used to decrease the off-rate with the target protein (same dose, but more inhibition) or it may limit side effects which could allow for an increased dose (that is better tolerated by the patient).

    - Joe [] []

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