As anticipated, the pharmaceutical firm Roche will retest its Huntington’s disease gene silencing drug, tominersen, by enrolling a more limited group of volunteers for a new clinical trial, which should start in early 2023.
Roche announced the new trial, GENERATION HD2, on September 18 at a meeting of the European Huntington’s Disease Network (EHDN) in Bologna, Italy. Roche also issued a letter to the HD community.
Roche halted the GENERATION HD1 trial of tominersen in March 2021 because of lack of efficacy against HD symptoms.
However, after months analyzing the GENERATION HD1 data, Roche reported in January that tominersen might benefit younger patients with less advanced symptoms. The new 16-month study, GENERATION HD2, will verify efficacy in that group.
GENERATION HD1 enrolled clinical trial volunteers ranging in age from 25-65 and included people with more advanced disease.
GENERATION HD2 will limit participation to people aged 25-50 who have “prodromal (very early subtle signs of HD) or early manifest HD,” the Roche letter stated.
“I am very excited about this new trial,” Jody Corey-Bloom, M.D., Ph.D., wrote me in a September 19 e-mail.
Dr. Corey-Bloom directs the Huntington’s Disease Society of America (HDSA) Center of Excellence at the University of California San Diego, a site for GENERATION HD1 and again for GENERATION HD2.
“A lot of thought has gone into the new trial,” Dr Corey-Bloom observed. “I think this is a very well-planned trial!”
Roche world headquarters in Basel, Switzerland (photo by Norman Oder)
Key adjustments in dosing
According to the Roche statement, GENERATION HD2 aims to sign up approximately 360 participants in approximately fifteen countries (Argentina, Austria, Australia, Canada, Denmark, France, Germany, Italy, New Zealand, Poland, Portugal, Spain, Switzerland, the United Kingdom, and the United States). Additional locations might be added.
The study will have three cohorts. One third will receive placebo, one third 60 mg of tominersen, and one third 100 mg. To ensure the objectivity of the trial, neither the participant nor study team will know what the participant receives.
In contrast with GENERATION HD1, the new trial also will administer lower doses of tominersen. In GENERATION HD1, all volunteers receiving the drug took 120 mg. In GENERATION HD2, participants taking the drug will get either 60 mg or 100 mg.
Another key difference involves the frequency of dosing. GENERATION HD1 administered the drug every two or four months, whereas the new study will dose at only four months.
These adjustments are a major goal of the study: to determine whether lower or less frequent dosing can be beneficial. Such lower dosing or less frequent dosing potentially avoids some of the problems seen in GENERATION HD1. In that trial, the higher dose did not benefit volunteers (click here and here to read more).
As in the first trial, in GENERATION HD2 tominersen will be administered via lumbar puncture (spinal tap).
Renewed but cautious hope for preventing HD
The Roche letter reported that GENERATION HD1 and all other related tominersen studies have closed.
“These studies comprised the first-ever Phase III [efficacy] clinical program to test the huntingtin-lowering hypothesis,” the letter noted, referring to tominersen’s mechanism of lowering the amount the huntingtin protein involved in HD. “Additionally, it was because of the HD community’s commitment to research that the trials recruited faster than anticipated, and thus generated data faster than anticipated.”
That commitment, the letter observed, “inspires all researchers to continue pursuing potential options for people impacted by the disease.”
Roche will announce additional information about GENERATION HD2 in the coming months.
After the devastating news about tominersen 18 months ago, its potential seemed dead. Now, though enthusiasm about tominersen has perhaps diminished, a new, albeit less ambitious, path perhaps has emerged for the drug.
"Overall, the announcement of the new GENERATION HD2 trial at the EHDN meeting was well received by the audience in Bologna, which was a mix of clinicians, scientists, and families," HDSA CEO Louise Vetter, who attended the meeting, wrote me in an e-mail. "The fact that this trial is clearly a dose-finding study was notable, and it seem representative of the more conservative mood in the HD clinical science right now."
“While the results of GENERATION HD1 were certainly disappointing for everyone, they don’t mean that huntingtin-lowering isn’t a viable therapeutic approach,” Sarah Hernandez, Ph.D., the Director of Research Programs for the HD-focused Hereditary Disease Foundation, wrote me in an e-mail. “Targeting huntingtin directly targets the cause of HD and remains one of the strongest therapeutic hypotheses.”
GENERATION HD1’s results “also don’t mean that HTT lowering won’t eventually work for a broad population of people with HD,” Dr. Hernandez added. “They just mean that tominersen seems to require a more narrow patient group for efficacy. The new GENERATION HD2 trial seeks to define exactly what that patient group is, which could be very significant in moving the field forward.”
My hope is that GENERATION HD2’s aim to treat individuals earlier in the disease could generate valuable insights for a major goal in the science of HD and other neurodegenerative diseases: a therapy to prevent symptoms from appearing in disease gene carriers like me.
