The more important (only relevant IMHO) question is how do we increase therapeutic dosing (WITH proper biomarkers), without side effects. But letâs leave that for a separate thread.
Dr B is a constant proponent for âas much as you can take without side effectsâ, ergo, typical high AUC for optimal drug therapy. The seminal cancer/rapamycin study used weekly dosing with target AUC maximization. Most patients on rapamycin for cancer/transplants are on daily with target trough blood (indirectly AUC) levels. The rapamycin/mice studies, the mice are subjected to typically daily very high rapamycin blood levels (but they have vastly higher metabolism, and drug elimination), have significantly reduced mTOR, and extended lifespan. The higher the dose (higher AUC), the higher the lifespan extension.
Current human translation for longevity is a complete unknown.
As for the dosing strategy, you can generate an infinite number of dose/time/AUC curves for rapamycin, staying just under toxic (dose limiting side effects) concentrations, but above a minimum. Most all of the studies Iâve read on humans (cancer/transplant), itâs either daily (one study of weekly). In mice, vast majority are daily.
We know in a single human study, rapamycin does cross the BBB, and the higher the peripheral dose, the higher the brain concentration of rapamycin (2, 5, or 10mg daily). So this may be one rationale for a higher dose spread over a longer period (to get a short peak burst, but you dampen AUC, and lessen side effects). But I would argue for human lifespan extension, for the greatest mTOR inhibition (the main target pathway), we would want the highest AUC just below toxic, and that is more likely (ie mathematically) via lower dose but increased dosing frequency. All things being equal.
Dr Green on his 12mg two days in a row, followed by longer period, is just another iteration at dose/time/peak experimentation.
Pharmacodynamic-Guided Modified Continuous Reassessment MethodâBased, Dose-Finding Study of Rapamycin in Adult Patients With Solid Tumors