Late last week, the US pharmaceutical company, Amylyx, released the news that their treatment, RELYVRIO, had failed its Phase 3 clinical trial.

RELYVRIO was approved in 2022 in the U.S. and Canada based mainly on data from a Phase 2 study called CENTAUR (NCT03127514). It tested the therapy against a placebo in 137 adults with recently-diagnosed, rapidly progressing MND. There was a strong advocacy public campaign supporting Relyvrio from a number of community organisations which likely aided in the treatment being approved based on only Phase 2 data, which is extremely unusual.

The Phase 3 clinical trial called Phoenix, tested RELYVRIO (formerly known as AMX0035) in over 600 participants and looked at a number of measures including ALSFRS-R, survival and respiratory function over 48 weeks. Unfortunately, none of these measures have shown any difference between participants receiving the treatment versus a placebo.

Amylyx have not yet stated whether they will withdraw RELYVRIO from the US and Canada.

There was a lot of optimism around the potential of RELYVRIO to add to the treatment options for MND so it is incredibly disappointing to see this trial fail. It should be noted that Amylyx committed to running this well-designed Phase 3 trial even after approval in the US. Although not the outcome we wanted, the trial design was such that we did get a definitive answer. We also thank the many participants and their carers for making these large trials possible.

We now await the full data from the trial to see what else can be learnt. This outcome certainly suggest that well-designed Phase 3 trials are our best hope of ensuring we have robust effective treatments available for MND going forward. The wisdom of approving treatments based on Phase 2 data, even if the data looks positive, must be considered carefully.