Looking for advice on brother who won't leave his room

Hi, I'm looking for advice for my brother, he's 16, 17 in November. He has been diagnosed with mild autism and social anxiety. He hasn't been to school for most of his life and in recent years barely leaves his room, he doesn't bathe, he has no friends and sits in the dark playing computer games all night and sleeps all day. He has had involvement with cahms, seen psychiatrists and doctors to no avail. He has now got problems with his legs from sitting for hours and never leaving the house to exercise, My mum and I have tried everything to try get him out his room but he just ignores us or gets angry. We both feel heartbroken and I feel the older he gets the worse it's going to be, he seems to be stuck in a online world. we have often thought about cutting the electrics but his computer is his life line and where his only friends are. Has anyone had any experience with something similar? He's also just been turned down pip even after an appeal, which is very scary as he can't even leave the house so how they expect him to work is beyond me! I just feel scared for his future as me and my mum are the only people he has got.