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There are several ways. One is to turn the main Vdd voltage on and off. Another is to apply a gate bias that shuts off the drain current.
You should also consider disconnecting the input signal line to reduce the amount of transmitted signal power going to it which can either damage it immediately or do small damages that add up over time.
One standard way is to have a PIN diode in series with the line and one in shunt.
I know of one case where the input signal disconnecting was not complete and the amplifier would stop operating after about a hundred hours. A previous design with one series and two shunt (spaced a quarter wave apart) work well enough to not have any field failures.