Who will fund it (it would be *very* expensive) when they have no hope of recouping the expenses? Consider: We have a likely candidate for a male birth control pill. It's considered quite safe, infertility (while taking it) is a known side effect. All that needs testing is whether it's reliable enough to be used for birth control. Unfortunately, there's a big headache with that--it does *not* stop sperm production so you can't test by having men jack off in a test tube and do a sperm count. Thus testing will be expensive. It's been known about for quite a while and nobody has funded it.
Clinical trials are expensive, and rapamycin can't be patented. My guess is that, some time in the future, a pharma company will produce and patent an analogue, and then there will be trials.
Human trials of this will likely never happen. At least not publicly.