March 16th, 2026

Dear Huntington’s Disease Community,

We are delighted to share an update on the development of votoplam (formerly PTC518). Last month we shared the news that the votoplam Phase 3 clinical trial, INVEST-HD, has been posted on ClinicalTrials.gov. Further progress to initiate the study has been made since then:

• We have activated our first sites for the study. This means that the study is now open for participant enrollment at these hospitals/centers.

• To date, we have activated two sites in North America (one each in USA and Canada) and more sites will follow in these countries as well as in well as in more countries.

• The study aims to recruit about 770 study participants from over 30 countries worldwide.

• The list of participating study sites will be updated regularly on ClinicalTrials.gov over the coming weeks and months, as sites come on board.

About the INVEST-HD study

INVEST-HD is a global pivotal Phase 3 clinical trial designed to evaluate the safety and efficacy of votoplam, an investigational oral medicine for Huntington’s disease. The aim of the study is to see whether votoplam can slow the progression of Huntington’s disease in people in the early stages of the condition.

The study builds on findings from earlier research, including the Phase 2 PIVOT-HD study. While current treatments can help manage symptoms of HD, there remains a high unmet need for therapies that could slow the progression of the disease. As with all clinical studies, participant safety is a top priority, and their health will be carefully monitored throughout the duration of this study.

You can view the INVEST-HD study (NCT7326709) information here: Study Details | NCT07326709 | A Study to Investigate the Efficacy, Safety and Tolerability of Votoplam in Participants With Huntington's Disease | ClinicalTrials.gov. Please note that updating the information on this platform may take some time.

Novartis remains committed to transparency, collaboration with the HD community, and sharing updates as the development continues. We encourage anyone who is interested to review the study information posted on ClinicalTrials.gov and to speak to their healthcare provider.

Kind regards, Votoplam Clinical Development Team at Novartis