Semorinemab failure tempers tau hopes

The next big approach in Alzheimer’s has been dealt a blow, and there are plenty more tau-targeting contenders.

After repeated failures with anti-amyloid drugs, targeting tau protein was the next big idea in Alzheimer's disease. But a setback with one of tau's first big tests suggests that progress with this mechanism might not come any easier.

News of the failure of Roche and AC Immune’s anti-Tau MAb semorinemab will have set nerves jangling at the likes of Biogen and Lilly – stalwarts of the amyloid years that are now heavily invested in tau. But with few details available on semorinemab’s flop, the host of companies developing tau-targeting agents will have to wait to see if glimmers of hope can be found among the wreckage.

For now, all Roche and AC Immune are saying is that the phase II Tauriel trial in prodromal to mild Alzheimer’s did not meet its primary endpoint, change in the clinical dementia rating-sum of boxes score, with semorinemab showing no benefit over placebo. The companies did not disclose the p value.

The study also missed two secondary endpoints, the ADAS-Cog13 and the ADCS-ADL.

More data should be presented at the CTAD meeting in November, according to Leerink analysts. Attendees will be particularly keen to see tau biomarker data – if semorinemab is shown not to be effective at clearing tau, this could explain the failure, meaning the tau hypothesis might still be in play.

Tau caution

Even if this turns out to be the case, there are reasons to be cautious about other late-stage anti-tau projects. The most advanced, Taurx Pharmaceuticals’ LMTX, has already failed twice in phase III. And Axon Neuroscience’s AADvac1 failed to show a benefit on clinical efficacy endpoints in its phase II trial.

Furthermore Abbvie and Biogen’s anti-tau MAbs, ABBV-8E12 and gosuranemab, failed last year in progressive supranuclear palsy which, like Alzheimer's, is characterised by the build-up of tau in the brain.

There is a question mark over whether antibodies will be effective therapies given that they target extracellular tau, and pathologic tau largely accumulates within neurons. However, extracellular tau could have a role in the spread of pathologic tau between neurons.

AC Immune is taking different approaches with its two other anti-tau projects. The vaccine ACI-35.030 is being developed in collaboration with J&J, while Lilly is partnered on ACI-3024, a small molecule designed to be able to pass through cell membranes to inhibit intracellular tau aggregates.

Semorinemab is not dead yet, with the phase II Lauriet study in moderate Alzheimer’s ongoing. However, hopes are now low, reflected by the fact that AC Immune lost nearly half its value yesterday.

Selected tau-targeting projects in clinical development
Project Company Description Note
Phase III      
LMTX Taurx Pharmaceuticals Tau aggregation inhibitor AD trial to complete Dec 2021
Phase II      
Semorinemab/RG6100 Roche/AC Immune Anti-tau MAb Tauriel in prodromal/mild AD failed; Lauriet in moderate AD ongoing
Tilavonemab/ABBV-8E12 Abbvie Anti-tau MAb Failed in PSP; study in early AD completes Apr 2021
Zagotenemab/LY3303560 Lilly Anti-tau MAb Study in early symptomatic AD completes Aug 2021
Gosuranemab/BIIB092 Biogen/Bristol Myers Squibb Anti-tau MAb Failed in PSP; Tango in early AD completes Mar 2024
Phase I/II      
BIIB080 Biogen/Ionis Pharmaceuticals Tau antisense oligonucleotide RNAi therapeutic Study in mild AD completes May 2022
ACI-35.030 Johnson & Johnson/AC Immune Anti-tau vaccine Study in early AD completes Oct 2022 
Phase I      
BIIB076 Biogen/Eisai Anti-tau MAb Volunteer & AD study completed Mar 2020; no data yet
E2814 Eisai Anti-tau MAb Volunteer study completed Aug 2020
PNT001 Pinteon Therapeutics Anti-tau agent Volunteer study completes Nov 2020
ACI-3024 Lilly/AC Immune Tau aggregation inhibitor Volunteer study data due 2020
Lu AF87908 Lundbeck Anti-tau aggregation MAb Volunteer & AD study completes Mar 2021
BEY2153 Beyondbio Beta-amyloid & tau aggregation inhibitor Volunteer study completes Oct 2021
UCB0107 Roche/UCB Anti-tau MAb PSP trial ongoing, AD deal signed Jul 2020 
Source: EvaulatePharma,

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