Investors add $119m to TauRx' kitty as tau drug filing nears

Investors in TauRx Pharma have exercised warrants worth around $119 million, adding to the biotech's financial resources as it prepares regulatory filings for tau-targeting Alzheimer's drug hydromethylthionine mesylate (HMTM) on the back of its recently-reported LUCIDITY trial.

The cash injection from the UK and Singapore-based biotech's existing shareholders adds to $64 million raised in 2021 via an earlier rights issue, and comes a couple of weeks before the company is due to present its LUCIDITY data on full at the Clinical Trials on Alzheimer's Disease (CTAD) conference in San Francisco on 30 November.

TauRx chief executive Glenn Corr said in a statement that the latest funding was triggered by the results of the trial, which pointed to improvements in cognition in patients with early to mild/moderate Alzheimer's and a slower rate in brain atrophy – although, notably, the study was compromised by an issue with its control group.

Specifically, the control arm received a low dose of related compound called MTC that was designed to provide the same change to the colour of urine as HMTM, so the subjects would not know they were not receiving the test drug.

However, blood levels of a metabolite thought to be responsible for HMTM's effects were higher than expected, exceeding the threshold needed to produce a clinical effect, so a direct comparison between the two arms was impossible.

As a result, the company has argued that it is not technically possible to carry out a truly blinded clinical trial of HMTM, and its efficacy analysis hinges on comparisons with baseline cognition levels.

Top-line results from LUCIDITY were reported last month, and TauRx has since said it intends to press ahead with regulatory filings for HMTM in the UK, US, and Canada based on the data, even though the jury is out on whether its data will be strong enough to secure approvals.

TauRx' current investors seem to be optimistic the data will be, given the desperate need for new Alzheimer's therapies.

"This represents a firm commitment to our mission – 'To discover, develop, and commercialise innovative products for the diagnosis and treatment of neurodegenerative diseases caused by protein aggregation'," said Corr.

"Beyond funding regulatory submissions in the UK, US, and Canada, this investment will also advance development plans for regulatory approval in China," he added.

Tau is a protein that is found in cells of the central nervous system and is involved in the assembly and stabilisation of neuronal microtubules – channels used to transport substances to different parts of the nerve cell.

In AD, the protein goes haywire, forming tangles that have been linked to cell damage and neuronal death. Tau tangles are one of the characteristic hallmarks of Alzheimer's visible in the brain, along with amyloid plaques.

TauRx was an early proponent of the notion that tau protein could be a legitimate drug target in Alzheimer's, since it was taken up by a lot of larger companies, including Roche/UCB, Johnson & Johnson/AC Immune, and Eisai, amongst others.