Multiple sclerosis (MS) is a central nervous system autoimmune disease that targets and destroys the myelin sheath that surrounds axons as well as the axons themselves.
The most common form of MS is relapsing-remitting MS, where symptoms can appear for days or weeks, then resolve spontaneously. In secondary progressive MS, pre-existing neurological deficits worsen over time due to the cumulative damage to the axon and myelin sheath. Primary progressive MS affects 15% of MS patients, where there are gradually worsening symptoms from the start, with no relapses. MS can start between 10 to 80 years of age, but onset is typically between 20 and 40 years, the mean being 32 years of age.
Symptoms are broad as the disease can target any area in the central nervous system, such as the brain and spinal cord. Brain lesions, namely in the cerebrum, are the most common, but manifest relatively few symptoms. As the cerebral lesions are clinically silent, they are usually identified via MRI. Spinal cord lesions will have the patient present with sensory or motor dysfunction. Hemiparesis or paraparesis may occur depending on the level and areas within the spinal cord affected. Relapsing MS is filled with periods where symptoms initially manifest over days, then worsen over weeks, then subside over weeks and months. Progressive MS is most commonly seen as an advancing myelopathy that presents gradually with asymmetric leg weakness, ataxia, and spasticity.
Diagnosis is crucial at the early stages of MS, so that appropriate therapies can be implemented to reduce the impact of the disease. However, there are no pathognomonic findings in MS. Instead, a diagnosis is made after weighing evidence in support of or against MS as the entity. An MRI may be helpful when showing typical lesions, but a diagnosis of MS cannot depend on MRI alone.
The cause of MS remains unknown, although it is likely that the impetus may be multifactorial. There is no cure for MS, but technological advances have allowed for the development of disease-modifying therapies (DMTs) that slow the progression of the disease. Current DMTs are preventive and focus on the early inflammatory phase of the disease by aiming to inhibit disease activity. Treatment at the early stage is crucial in that cumulative and irreversible tissue damage will reduce the benefit of DMTs.
MS therapies are expensive, costing nearly $50,000 annually. The market is sizable, even when only considering the American market, where 400,000 are suffering from MS. This results in a market size of approximately $20 billion. There is a need for therapies that can be used in relapsing and progressive MS, especially since progressive MS is much more difficult to treat.