The Kaiser Health group has done a survey of over 1,200 patient advocacy groups, including the MS Society and quite a few of its chapters, to find out how much of their funding comes from Big Pharma.
https://khn.org/patient-advocacy/#
The National MS Society got only a small proportion of its revenue from the pharmaceutical companies but it's still a considerable sum--over $549,000. Some of the regional chapters received little or no funding from the drug companies.
If my arithmetic is right, the National MS Society gets 0.4% of its revenue from the drug companies.