Trial site staff shortages, sluggish patient recruitment force Addex to scrap phase 3 Parkinson's study

Addex Therapeutics waited more than a decade for the chance to learn whether dipraglurant is effective in dyskinesia associated with Parkinson’s disease (PD-LID), suffering delay after delay as it tried to get a late-phase trial started. After all that, the phase 2b/3 study has crashed out before delivering data because “COVID-19 related patient concerns about participation in clinical studies as well as staffing shortages and turnover within study sites” made enrollment intolerably slow. 

Geneva-based Addex began the phase 2b/3 clinical trial of its metabotropic glutamate receptor subtype 5 negative allosteric modulator one year ago, having seen COVID-19 thwart its attempt to get the study up and running in March 2020. The plan was to enroll around 140 patients at 50 or so sites in the U.S. 

As the months went by, the target for the readout of top-line results slipped from the fourth quarter of 2022 to the first half of 2023, but Addex gave no indication the study was in jeopardy. Three weeks ago, Tim Dyer, CEO of the Swiss biotech, said the phase 2b/3 study remained “on track to report data in the first half of 2023.” Now, Addex has given up on the trial altogether. 

“We took this decision because it was not feasible to continue the study at such a slow recruitment rate in the current environment. I’d like to emphasize that it was not dipraglurant related and we continue to believe in the potential of this compound as a treatment for PD-LID,” Dyer said in a statement Friday.

The action is the second hit of a double whammy for Addex’s pipeline. Late last month, the company revealed a phase 2a clinical trial designed to spearhead the expansion of dipraglurant into muscle spasm disorders had delivered “inconclusive” data. The setback left Addex looking to the Parkinson’s study and a fourth quarter readout on its Johnson & Johnson-partnered epilepsy drug for stock-boosting news. 

Stopping the Parkinson’s program reverts Addex back into a preclinical biotech. The plan now is to push the preclinical portfolio toward the clinic while “pursuing strategic collaborations for selected programs.” In its financial risk warnings, Addex cautioned that the failure to develop its most advanced assets “could have a material adverse effect on [its] business, financial condition, results of operations and prospects.”

The termination of the Parkinson’s study caps off a development story defined by delays. Addex posted phase 2a data on dipraglurant in March 2012. Back then, the company planned to partner up to advance the asset in PD-LID and use its internal resources to study it in a rare muscle spasm. The following year, Addex slashed its headcount to focus on dipraglurant in rare diseases, only to restart work in Parkinson’s in 2014. Talks with the FDA about a phase 3 trial began in 2015, but the start date kept slipping. 

Shares in Addex fell 35% to 0.35 Swiss francs ($0.36) in early trading in Switzerland.