The Pfizer rapamune product uses a special technology to increase bioavailability. Generally you don’t want to split sirolimus pills because it will ruin the protective covering and thereby destroy the barrier that increases bioavailability. Rapamune is more complex… so I’m not absolutely sure, but out of caution I’d avoid splitting rapamune: Rapamycin and NanoCrystal Formulations
Related reading: Which pills can be split and in what dose and which cannot be split