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'Auspex' of Chemistry: $25M for Phase III in Huntington's

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By Randy Osborne
Staff Writer

Is it possible, by tweaking the only molecule approved for movement disorders in Huntington's disease, to come up with a new chemical entity that's safer and dosed less often, thanks to a much longer half-life?

All in deuterium, according to Auspex Pharmaceuticals Inc.

The La Jolla, Calif.-based company's new $25 million from a Series D venture round will finance Phase III experiments with SD-809, an analogue of tetrabenazine (Xenazine, Prestwick Pharmaceutical Inc.), the vesicular monoamine transporter 2 inhibitor approved by the FDA in 2008.

By replacing carbon-hydrogen bonds with carbon-deuterium bonds, Auspex "doesn't change the shape of the molecule at all, or its binding properties, but can have, in certain cases, a dramatic effect on its rate of metabolism," said Lawrence Fritz, president and CEO. That means SD-809 may be dosed twice rather than three times per day, with less risk of drug-drug interaction and less likelihood of efficacy variations from patient to patient, he said.

"Medicinal chemists over the decades had used all kinds of atoms to change the properties of molecules, but everybody had overlooked deuterium," Fritz said. Hydrogen with another neutron in the nucleus, deuterium has "nothing spooky about it," he said. "It's not radioactive, and it's naturally occurring."

Set for the first half of next year, the Phase III trial could be relatively small and move along briskly. Fritz declined to provide details of the trial, but noted that tetrabenazine was granted marketing clearance on the strength of a study that enrolled fewer than 100 patients.

"The drug also acts very quickly," he said. "In other central nervous system diseases, you [may] have to treat for a year before you have a chance to see an effect."

Auspex owns all of SD-809, which was invented by the company. "Whether we will commercialize it ourselves, we have to decide down the road," Fritz told BioWorld Today.

"There's a relatively small number of movement-disorder specialists who are the main physicians for Huntington's patients in the U.S.," which makes it reasonable for Auspex to "aspire to be a commercial player," though Fritz said the firm "may at some point link up with a company that's already commercial."

The first label to be sought for SD-809: movement disorders, also called chorea, in Huntington's – same as tetrabenazine – but the analogue may also work in Tourette syndrome and tardive dyskinesia, like tetrabenazine.

Partnering seems more certain, regarding the rest of Auspex's drug candidates. "We have a substantial pipeline, and we're not going to have the resources to develop all of those ourselves," Fritz said.

Behind SD-809 are SD-900, a JAK kinase inhibitor for autoimmune diseases, and SD-560, for fibrotic diseases. The former, for rheumatoid arthritis, is an analogue of New York-based Pfizer Inc.'s late-stage oral JAK inhibitor tofacibinib, taken twice daily. Auspex hopes to devise a once-daily dose with a wider therapeutic window.

SD-560 is an analogue of pirfenidone (Esbriet, InterMune Inc.) for idiopathic pulmonary fibrosis. It's approved in Europe, Canada, Norway and Iceland, but must be taken three times daily, and then gets limited efficacy and with significant side effects. Auspex aims for a compound with better safety and compliance.

The latest financing was led by Panorama Capital, with existing investors Thomas, McNerney & Partners, CMEA Capital and Sloan Biotech Fund also taking part.

In other financing news:

• Genoa Pharmaceuticals Inc., of San Diego, raised $1.2 million to advance its lead program, GP-101 (aerosol pirfenidone) for idiopathic pulmonary fibrosis. The cash will allow us to advance GP-101 to "a key inflection point for prospective partners and investors by early 2013," the company said.