Prilenia Therapeutics is seeking regulatory approval for pridopidine in treating Huntington's disease (HD), but a critical look at the drug's clinical trial history reveals a complex picture of unmet endpoints and controversial interpretations. While the EMA has accepted Prilenia's application for marketing authorization review, it's crucial to examine the underlying data and messaging surrounding pridopidine's efficacy.
A History of Unmet Endpoints
Pridopidine has been evaluated in numerous clinical trials, including MermaiHD, HART, PRIDE-HD, and PROOF-HD. Initially investigated for its potential to regulate movements associated with HD, the focus shifted to modifying the disease course. However, across these trials, pridopidine has consistently failed to meet its primary endpoints.
In the PROOF-HD trial, the primary endpoint was Total Functional Capacity (TFC), a measure of day-to-day functioning. The trial did not demonstrate any improvement in TFC for patients taking pridopidine. Similarly, the trial failed to meet its secondary endpoint, the composite Unified Huntington’s Disease Rating Scale (cUHDRS), an overall assessment of HD severity.
Controversial Interpretations and Subgroup Analysis
Despite these negative results, Prilenia has emphasized findings from a subgroup analysis of the PROOF-HD trial, focusing on individuals not taking dopamine-altering drugs (neuroleptics). This subgroup of 79 patients showed some benefits on cUHDRS and a measure of cognition, but not on TFC.
This approach has raised concerns about downplaying the overall negative results and potentially influencing treatment decisions. As stated by HDBuzz, there are worries that "people from HD families could end up with a much more favorable impression than is warranted of pridopidine being the first disease-slowing drug for HD. Unfortunately, all the evidence so far does not support that hope."
The Role of Neuroleptics
The potential interaction between pridopidine and neuroleptics is a critical consideration. Neuroleptics are commonly prescribed to manage HD symptoms such as aggression, impulsivity, and paranoia. The company supported a non-peer-reviewed poster summary that claimed to show links between neuroleptic treatment and the progression of HD. This raises concerns about the conclusions HD families might draw and the potential for people to stop taking medicines that are protecting themselves and others from harm.
EMA Application: A Routine Step
Prilenia's announcement that the EMA has accepted its application for marketing authorization review has been met with caution. While this is a necessary step in the regulatory process, it does not guarantee approval. As HDBuzz notes, "Getting applications accepted for consideration is a process that every approved drug goes through. But it’s also a process that every refused drug goes through."
Seeking Truth and Balanced Reporting
Given the history of unmet endpoints and the controversial interpretations of subgroup analyses, it is essential to maintain a critical perspective on pridopidine's potential. While hope for effective HD treatments is vital, it must be grounded in truth and balanced reporting of clinical trial results. The HD community deserves clear, unbiased information to make informed decisions about their care.
