There is a Phase 3 placebo-controlled clinical trial to evaluate the efficacy of sodium oligomannate (GV-971) in the treatment of mild to moderate Alzheimer's disease (AD).
Why can sodium oligomannate (GV-971) improve cognition in people with Alzheimer's disease? What is the mechanism of this drug in AD?
From Wikipedia, albeit not the best source for this sort of thing:
The mechanism by which sodium oligomannate may function is unclear and several possibilities have been proposed,[6] including amyloid beta disaggregation,[7] mediation of inflammatory responses to amyloid plaques,[8] protein binding inside neurons,[9] and alteration of intestinal bacteria.[10]
The page also mentions:
It was conditionally approved in China by the National Medical Products Administration in 2019 for mild to moderate AD to improve cognitive function.[1] However, the clinical data supporting its potential benefits have been received skeptically elsewhere[2][3][4] and are considered insufficient for approval in other countries.
Importantly, it's not necessary to know a drug's mechanism to get it approved, only to show that it is safe and effective. The mechanism for antidepressants, for example, is still not known, for any of them, we just know that they work better than a placebo. We also know what receptors in the brain they affect and the local mechanisms there, but without a better scientific understanding of depression it's not currently possible to understand which combination of those molecular effects give the behavioral effects.
Similarly, Alzheimer's disease is not understood mechanistically, so it's very plausible to develop drugs for it without knowing the mechanism. For this drug, it seems like both the mechanism and efficacy are not known to the standards expected by regulators in the US and EU for approval.
The proposed list of mechanisms mentioned on the Wikipedia page sound a bit to me like a collection of all the different theories of mechanisms for Alzheimers' disease itself, which is still poorly understood.
