Use of Rituxan to treat autoimune disease (Devic's Disease/NMOSD))

I am presently in my third round of Rituxan (2 infusions 2 weeks apart, every 6 months) to treat Neuromyelitis Optica Spectrum Disorder, previously known as Devic's Disease. After almost a year and a half, my overall symptoms (numbing/tingling in lower extremities, foot drop in right foot, muscle/joint stiffness, uneven gait, balance problems, bowel/urinary issues) have continued to worsen. I now have to use walking poles/walker to get around - both in and out of the house. I had my car recently modified from traditional foot controls to hand controls so I can continue to drive. I consulted with my neurologist last month about getting off Rituxan in May when my 3rd round is completed and trying something different. I was told there is nothing to replace Rituxan (three relatively new drugs are now being used, including at the Mayo Clinic, to treat neuromyelitis optica spectrum disorder) without trying other medications with serious side effects and high expenses that would not be covered by most insurances). My neurologist also said there is no cure for my disease, only the possibility of managing current symptoms at the status quo level with Rituxan. I realize I will have to deal with this life-altering disease for the rest of my life ( I am 73 years old), but I am convinced that there can be medications out there that can prevent my current symptoms from getting any worse. Any suggestions or plan of action would be greatly appreciated. Thank you.