Is it possible to extend a 90 day business visa (m)?

Hello,
I had an invitation letter from the inviting company in Shanghai for about 150 days but I only received a M type for 90 days with single entry. It's my first time I received an entry permit for PRC. Is it possible to extend this M type for another 60 days (at least) and when would you recommend to apply for it? Do I have to leave PRC after the 90 days to renew the M type?

Thanks in advance!