Background: PET scans are useful for assessing amyloid and tau deposits in
persons being evaluated for participation in clinical trials. The
most widely used tau PET ligands are Flortaucipir and MK6240.
We compared tau PET positivity rates for these two ligands in
an interim analysis of the Bio-Hermes-002 study which included
persons who were cognitively normal (CN), had clinical Mild
Cognitive Impairment (MCI) or mild Alzheimer’s disease (AD);
all had amyloid PET scans with Florbetapir.

Methods: As of May 2026, 878 of the planned 1000 participants have been
enrolled at 25 sites in the US, Canada, and the UK.
• By NIH/ADRDA clinical criteria, 292 were CN, 322 were MCI
and 264 had mild AD.
• In addition to the amyloid and tau PET scans, demographic
data, clinical history, cognitive assessment with the MMSE,
and other scales were completed with the participant.
• Flortaucipir and MK6240 were used for 237 and 641
participants, respectively. All scans were centrally read by
trained neuroradiologists as positive or negative according to
the manufacturer’s instructions.

Results: • Age increased and MMSE scores decreased going from CN to
MCI to mild AD as seen in Table 1. Age and MMSE were nearly
identical for groups given each of the two tau PET ligands.
• There was a highly significant association of tau PET positivity
with amyloid PET positivity , χ2 = 277.40 (1, N = , p < .001).
• There was also a highly significant association of tau PET
positivity and amyloid PET positivity when comparing within
the CN, χ2 = 24.50 (1, N = 292 , p < .001) , MCI, χ2 = 87.89
(1, N = 322 , p < .001) , and AD groups, χ2 = 96.02 (1, N = 264, p < .001).
• There was no significant difference between the tau PET ligands
in the rate of tau PET positivity for the CN, χ2 = 1.09
(1, N = 292 , p = .30), MCI, χ2 = .31 (1, N = 326, p = .58), or the
AD groups, χ2 = .15 (1, N = 264 , p = .70).

Conclusion: The Tau PET positivity rates were comparable for
Flortaucipir and MK6240 across CN, MCI and
Mild AD participants and for both amyloid positive
and negative participants. Detailed regional and
quantitative analyses are underway and may reveal
differences between ligands.