We want to choose ADG904 OR ADG918 for
nA level optical current in APD application, the Output is TIA amp.
1. ADG904 OR ADG918, which is more suitable for this application(Ibias and Ibias with temperature)
2. TIA products in ADI solution
3. recommendedSignal chain an APM
ADG904 is SP4T switch and ADG918 is SPDT switch. They both has leakage of 0.1uA but you are looking for nA leakage so I think your requirement has ruled out both of these switches.
You can try ADG1204, its 4:1. it has sub nA leakage typical.
Can you please tell me what's your RF requirement and also power supply requirement.