Update on PROOF-HD clinical trial – a letter from Prilenia

Dear Huntington’s Disease Community,

We are reaching out to provide an important update about the topline results from our Phase 3 study, PROOF-HD. For those who aren’t familiar with the study, the objective was to evaluate the efficacy and safety of the investigational drug pridopidine (a 45 mg oral capsule taken twice daily) in patients with early-stage manifest Huntington’s disease (HD).

The study did not meet its primary endpoint, change from baseline compared to placebo at 65 weeks, as measured by the Unified Huntington Disease Rating Scale-Total Functional Capacity score (TFC) or the key secondary endpoint measured by the Composite Unified Huntington’s Disease Rating Scale (cUHDRS).

However, there are encouraging signals based on our initial review of the data. Analyses that excluded patients on neuroleptics (also known as antipsychotics) and chorea medications showed meaningful clinical benefits of pridopidine as compared to placebo on disease progression, motor, and cognitive outcome measures. Because the results could be different for patients taking these neuroleptic and chorea medications, we designed the study to look at these data sets (pre-specified).

Pridopidine was well-tolerated with no serious treatment-related adverse events, with a safety profile similar to placebo and consistent with previous clinical studies. We have just started analyzing the trial data, and we plan to update the HD community after we complete our full analysis, including presentations at future advocacy and medical conferences.

To learn more about the results of the PROOF-HD study, please read our press release here.

Our commitment to the HD community continues and we are examining potential ways to advance pridopidine in HD. We are working closely with patient advocacy organizations to share these preliminary PROOF-HD results with you, including two webinars planned for early May so the HD community can learn more and ask questions.

We would like to thank all study participants and their families, along with the broader HD community, for their collaboration on the PROOF-HD study. We appreciate your dedication and commitment to the study and are confident that the results will help advance HD research.


Seth Rotberg, Senior Manager of Patient Advocacy and Engagement
On behalf of the team at Prilenia






For further reading:

PROOF-HD update – response from European Huntington Association

PROOF-HD update – analysis by HD Buzz

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