Serono spinout raises €29M for phase 2 Parkinson’s trials

Fountain on Lake Geneva
Prexton's home city, Geneva, Switzerland

Prexton Therapeutics has raised €29 million ($31 million) to take its Parkinson’s disease candidate through two phase 2 trials. The Series B positions the Merck Serono spinout to build on last year’s phase 1 success by testing the mGluR4 positive allosteric modulator in larger efficacy studies.

New investors Forbion and Seroba Life Sciences co-led the round. Existing backers Merck Ventures, Ysios Capital and Sunstone Capital also chipped in money, resulting in Prexton pulling in €31 million to fund the next steps in the development of its lead candidate, Foliglurax. Prexton has attracted such support on the strength of data suggesting Foliglurax can better the ever-waning efficacy of Parkinson’s drugs that target dopaminergic pathways and address levodopa-induced dyskinesia.

Geneva, Switzerland-based Prexton will use the Series B funds to run two phase 2 clinical trials, one in the U.S. and another in Europe. Forbion Partner Marco Boorsma sees the approach setting Prexton on both EMA and FDA’s regulatory paths, "which is attractive for a potential acquirer."

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The trials will look at two different primary endpoints. One study will look mainly at Parkinsonian symptoms, while the other will focus more on levodopa-induced dyskinesia. The dual approach gives Prexton a chance to see how Foliglurax controls symptoms of Parkinson’s itself and its impact on a side effect of long-term dopamine therapy.

The Series B comes two years after Prexton raised €8.7 million in a round led by Ysios and Sunstone, and five years after Merck Serono put up €2.1 million in seed funding to get Prexton started. Boorsma described Prexton’s progress to date as both time efficient and capital efficient.

Prexton used the seed money to rescue Domain Therapeutics’ mGluR4 program when it got caught up in the shuttering of Merck Serono’s Geneva, Switzerland facility. And then turned the Series A cash into phase 1 data showing Foliglurax is safe and well tolerated at doses higher than those needed to improve outcomes in animal models.

Buoyed by these data and the backing of Forbion and Seroba—which unveiled a €100 million fund last week—Prexton CEO Francois Conquet is now set to get a crack at putting his belief in the potential of mGluR receptors to the test. Conquet has a long-standing interest in the group of targets, which he worked on during a 10-year stint at GlaxoSmithKline and when he founded and ran Addex Pharmaceuticals.

Progress in the field has stuttered—Merck abandoned Addex’s mGluR4 Parkinson’s drug in 2011—but Conquet remains convinced by the science. In Parkinson’s, the appeal lies in the potential of mGluR4 modulators to control symptoms without relying on dopaminergic pathways. Dopamine-producing nerve cells die as Parkinson’s disease progresses, making these pathways poorly suited for long-term symptom control. The mGluR4 receptor is free from these problems and, as such, could be the secret to keeping Parkinson’s patients well for longer.

Working with Forbion

Forbion took a look at Prexton when it was putting together its Series A, but ultimately decided it was a little too early to get involved. Events since then have persuaded Forbion to come on board for the Series B.

“The company has really developed very well. They have phase 1 data that looks really good, nice safety profile, very nice pharmacokinetics. And they have a really extensive ... preclinical nonhuman primate data pack,” Boorsma said.

These data persuaded Forbion to make Prexton its first biotech CNS investment—it has previously backed a medtech CNS player—because the VC shop sees them as going some way to mitigating the dangers of developing drugs in the field.

"[There's] higher translational risk. But we thought for Prexton and for Parkinson’s disease it is certainly balanced. The preclinical models translate pretty nicely, historically at least, into clinical benefit,” Boorsma said.

Boorsma and his colleagues are providing more than just money to Prexton. The Dutch VC shop is helping out by putting Prexton in touch with trial sites and experts, as it does for the rest of its portfolio. And it is working with Prexton to establish an outpost of the Swiss biotech in the Netherlands. Oss is currently the most likely location because of its history in biopharma.

“At the old Organon site there's a lot of skilled workers,” Boorsma said. Oss-based Organon was bought by Schering-Plough in 2007. Setting up in Oss will allow Prexton to tap into this resource, while also benefiting from the non-dilutive grants, comparatively low labor costs and flexible legal framework of the Netherlands. The R&D functions Prexton has built up in Geneva will remain in the city, but new functions could find a home in the Netherlands.

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