Negative Results with TPI 287 in CBS and PSP

A local support group member whose loved one was involved in this TPI 287 trial at UCSF contacted me a couple of weeks ago to say that she had learned that the trial was not successful.  I haven’t been able to find any independently-written article [see updated below!] on the study results (and, of course, shows nothing) but there is this pharmaceutical company press release.

The TPI 287 study was discussed by Adam Boxer, MD, UCSF at our recent PSP/CBD conference.  This was a phase 1 study, which has a safety focus.  Researchers are also trying to learn something about efficacy during these studies but that’s not the main point.  In the study, 14 patients with PSP and 30 patients with CBS were included.  32 received the drug and 12 received the placebo.

This seems to be the crux of the problem — “Interestingly, patients treated with TPI 287 performed worse on the [Clinical Dementia Rating] assessment vs. placebo after 12 weeks.”

Update:  A member of our email list forwarded me that independent write-up I was looking for on TPI 287; it’s on Alzforum. Just as the group member said, the trial had negative results. In addition to the worsening in the dementia rating scale (mentioned earlier today), there was also a worsening of falls in CBD and PSP patients. The study was also conducted of the same compound, TPI 287, in Alzheimer’s Disease. The experimental drug was not safe in AD patients at high doses. An excerpt from the Alzforum summary is below.

Excerpt from
At Least We Know These Don’t Work: Negative Trials at CTAD
15 Dec 2017

Adam Boxer, University of California, San Francisco, presented his center’s Phase 1 trial of TP1 287. Also known as abeotaxane, this small-molecule taxol derivative stabilizes microtubules. TPI 287 accumulates in the brain, and has been tested primarily to treat central nervous system tumors. Its application to tauopathies grew out of work showing beneficial effects of the microtubule stabilizer epothilone D in tau transgenic mice (Zhang et al., 2012). Testing of epothilone D in AD patients started in 2012 but was discontinued for lack of efficacy.

Boxer’s group examined the safety and tolerability of TP1 287 in 44 people with the primary four-repeat tauopathies cortical basal degeneration (CBD) or progressive supranuclear palsy (PSP), and in 33 people with AD. Participants received abeotaxane by intravenous infusion once every three weeks for nine weeks, with an option for open-label extension up to three months.

In recruiting for the CBD cohort, Boxer screened with amyloid PET to exclude people with AD and to limit the treatment group to people with pure tau pathology. Of 55 diagnosed with CBD, Boxer excluded seven based on positive amyloid scans. He also used CSF biomarkers to confirm diagnoses: AD patients had lower Aβ42 and higher total tau and phospho-tau levels than CBD/PSP group members, who showed elevations in neurofilament and a higher neurofilament light (NfL)/phospho-tau ratio than the AD group.

Participants received tailored doses of 2, 6.3, or 20 mg/meter2 TPI 287, or placebo.

AD patients tolerated the treatment poorly. Boxer told the CTAD audience that he had to stop the high-dose arm because two participants suffered anaphylactoid hypersensitivity reactions, most likely to the diluent for the active compound. In all, seven people in the AD group discontinued treatment. Curiously, the CBD/PSP group tolerated the drug well, even at the highest dose. They suffered no hypersensitivity reactions, and most participants stuck with the trial even through the open-label extension. However, in CBD and PSP patients, the drug caused more falls, a serious concern.

On the exploratory cognitive endpoints, the researchers saw a hint of stabilization of MMSE scores in the AD group, but no change in the ADAS-Cog, and the CBD/PSP cohort had a dose-related worsening on the Clinical Dementia Rating-Sum of Boxes at three months.

Boxer has no future plans for the drug, except to complete the analyses of pharmacokinetics and MRIs. He told Alzforum that investigators learned a lot from the trial. “It shows the importance of testing potential treatments in different tauopathies,” he said. “Animal models don’t tell the whole story, and we have to look at different conditions in humans,” he said.