seronegative gMG treatment beyond IVIG and/or Apheresis

IVIG was a fail for me (tried more than one product) and am currently receiving Apherisis every 3 weeks via an AV Graft in my arm. Doctors predict this will not work for long and are encouraging me to try another treatment. For all the seronegative gMGers what has worked? (not oral meds).
I should mention specialist is concerned about my allergic reactions to meds (2 weeks on Imuran had hives, fever 103+, kidney trouble, etc) as well as what insurance will cover because I'm seroneg