Hydroxychloroquine in Primary Progressive Multiple Sclerosis

In patients with primary progressive multiple sclerosis (PPMS) there is ongoing slow and continuous loss of nerve cells, which causes damage to the brain and spinal cord. This ultimately becomes noticeable as slowly and continuously worsening disability. While the cause of this ongoing damage is unknown, it appears that at least part of the damage may be caused by cells in the brain called "microglia" (a type of immune cell that reside in the brain and spinal cord). These microglial cells can have beneficial roles, for instance when they clear away debris, but they can also cause damage to brain cells. In PPMS, microglial cells are often found to be in a state of activation, and it is currently believed that this constant activation of microglial cells is likely an important cause of the ongoing damage to brain cells. Current treatments for MS only work in relapsing-remitting MS, and can prevent relapses, but so far there are no treatments that effectively target PPMS. Therapies for PPMS are needed. The investigators believe that treatments that target and reduce the activation of microglial cells may be a useful treatment strategy. Hydroxychloroquine (HCQ) is a medication that has been shown to decrease the activity of human microglia in laboratory experiments. Animal experiments have also shown that treatment with HCQ can reduce the disease activity of an animal model of MS. HCQ, therefore, may also reduce the activity of microglia in people with PPMS, and hopefully prevent or slow down the progression of disability in PPMS. HCQ is currently approved in Canada to treat malaria and the rheumatic diseases Systemic Lupus Erythematodes (SLE) and Rheumatoid Arthritis (RA). HCQ is available as a tablet that is usually taken two times per day. Doses up to 600mg per are used in clinical practice, but the investigators estimate that a dose of only 400mg daily, given as two doses of 200mg, will be sufficient to decrease the activity of microglia in patients with PPMS. HCQ is usually well tolerated. Following a MinMax Simon-2-stage design, the study will require 35 patients with complete 18 month follow-up. Presuming 20% drop-out, the investigators anticipate recruiting up to 42 patients. The trial will be conducted as follows: patients will continuously enter into the study until 35 patients have completed 18 months of follow-up with at least 75% adherence which will be measured by study drug count.