At San Diego’s Auspex Pharmaceuticals, CEO Larry Fritz is overseeing a drug development program based on a fairly simple premise: If an FDA-approved small molecule drug is susceptible to metabolic enzymes in the body that break down its hydrogen bonds, wouldn’t substituting some deuterium atoms make those bonds stronger and longer-lasting?
Deuterium is a stable and naturally occurring hydrogen isotope with a nucleus that is twice the mass of ordinary hydrogen. Fritz says replacing some hydrogen atoms with deuterium does not change the shape or electronic structure of a molecule. But as he put it in a recent phone call, “A few well-placed deuterium atoms can make a big difference.”
How big of a difference?
While the scientific basis for substituting deuterium has been generally established, Fritz says the pharmacokinetic effects have to be determined on a case-by-case basis.
Nevertheless, Auspex has enough confidence in the potential of its deuterium-based drug portfolio that the company has raised $25 million in a Series D round to help fund late-stage trials of its lead drug candidate. In a statement today, Auspex says the financing was led by Panorama Capital, and was joined by existing investors Thomas, McNerney & Partners, CMEA Capital, and Sloan Biotech Fund.
The company’s lead drug compound, SD-809, is a deuterium-based analog of tetrabenazine (Xenazine), a drug the FDA approved four years ago for treating the involuntary movements, or “chorea,” associated with Huntington’s disease, Tourette syndrome, and tardive dyskinesia.
Tetrabenazine is not a cure, but helps to control hyperkinetic movements by
