Only one DMT on offer for PPMS: Ocrelizumab. In UK, to qualify you need to be showing active lesions on a MRI which is unfair for those with “smouldering MS” where disease progresses but doesn’t show up on MRI. Elsewhere in the world, it is dispensed according to symptoms without the active lesions rider.
Ocrelizumab doesn’t cure, nor stop disease progression but in 70% of cases there is a report of a slowing of the rate of progression. Slim pickings unfortunately, though there are some clinical trials of so-called BTK inhibitors which are getting good results, though for some (me included), they can cause liver toxicity so have to be withdrawn. Do some searching for them as well as Smouldering MS.