Synthetic Triglyceride Shows Potential in Huntington Disease

Richard Mark Kirkner

September 23, 2021

The synthetic medium-chain triglyceride triheptanoin has shown potential to restore brain energy and decrease caudate atrophy in Huntington disease, and improved motor function for up to a year, according to data presented at the International Congress of Parkinson's Disease and Movement Disorders.

Dr Fanny Mochel

Reporting results of TRIHEP3 and an extension study, Fanny Mochel, MD, PhD, of Sorbonne University in Paris and the Paris Brain Institute, said in an interview that her group is the only one investigating triheptanoin to target caudate atrophy in Huntington's disease. The Food and Drug Administration last year approved triheptanoin for the treatment of long-chain fatty acid oxidation disorders.

"The main findings are two observations: that patients were clinically stable based on their gradation of total motor score (TMS) on UHDRS (Unified Huntington's Disease Rating Scale) after 1 year," Mochel said in an interview. "The other is that we observed a reduction of the caudate atrophy progression that we usually see over 1 year by about 50%."

TRIHEP3 randomized 100 patients with early stage Huntington disease to triheptanoin 1g/kg daily and placebo. It followed on previous research in which the group used 31-phosphorus brain MR spectroscopy to demonstrate triheptanoin restored a normal brain energetic profile in patients with Huntington's disease. TRIHEP3 was a 6-month randomized controlled trial at two centers, followed by a 6-month open-label phase. After that, 42 patients opted to participate in the 1-year extension study.

TRIHEP3 found no difference in caudate boundary shift integral (cBSI) at 6 months — the primary endpoint. But in the extension study, TMS tended to stabilize in patients treated for 1 year (0.6 ± 5.1), compared with those treated for 6 months (2.5 ± 4.5; P = .072).

Using a placebo control group from an external study of patients with Huntington's disease with what Mochel described as "identical clinical characteristics," she said the research confirmed TMS clinical stability in treated patients at 1 year (2.6 ± 4.6 vs 0.6 ± 5.1; P = .057) and found significantly lower caudate atrophy (–3% vs –6.7%, compared with baseline; P < .001).

Mochel also noted that Diffusion Tensor Imaging and Fixed-based analyses (FBA) showed fewer alterations in fiber metrics at 24 months in patients treated from baseline. FBA also showed improved fiber trophicity at 24 months in both groups.

"The First Good News"

Mochel noted that the Huntington's disease community had been shaken in the spring by the failure of three trials of gene-targeting therapies for Huntington's disease. Roche halted a phase 3 study of its antisense oligonucleotide (ASO) tominersen, and Wave Life Sciences scuttled two ASO programs in phase 1/2 trials.

"Triheptanoin is not going to cure Huntington's disease; it's a disease with many components, but it does work on the energy aspects and that seems to stabilize patients over the time of observation," Mochel said. "That's the first good news."

She also noted that side effects were mainly gastrointestinal in nature, and they typically resolved with dietary management.

Dr N. Ahmad Aziz

As a target in Huntington disease, the caudate nucleus is highly desirable, and caudate atrophy has been shown to occur even before the onset of motor symptoms, said N. Ahmad Aziz, MD, PhD, a neurologist and epidemiologist at the German Center for Neurodegenerative Diseases at the University of Bonn (Germany). "In this light, the findings of the trial conducted by Mochel and colleagues, which suggest that triheptanoin intake may slow down the rate of caudate atrophy in patients with early-stage Huntington's disease, are highly promising," Aziz said in an interview.

However, he noted that the improvement in caudate atrophy was only a secondary endpoint in the extension study. "Nevertheless, given triheptanoin's biologically plausible mechanism of action — ie, provision of substrates to the Krebs cycle and at least partial restoration of the well-documented defective mitochondrial function in Huntington's disease — combined with its apparently relatively mild side-effect profile and good tolerability, I think that the preliminary findings of this trial are very promising and justify a larger phase 3 trial," Aziz said.

Mochel said that the findings are prompting the investigators to consider just that.

Mochel has received consulting fees from and conducted investigator‐sponsored studies supported by Ultragenyx Pharmaceuticals. Aziz has disclosed no relevant financial relationships.

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