Development of kallikrein-related peptidase 6 inhibitors to treat multiple sclerosis – RESTORE

Multiple sclerosis (MS) is the most common neurological disorder and the leading cause of non-traumatic disability in young adults. MS affects 2.5 million people worldwide, including more than 100,000 in France. It is associated with an inflammatory reaction of the central nervous system (CNS) that results in the degradation of the myelin sheath surrounding CNS axons (diffuse demyelination). Clinically, MS is characterized by severe motor, sensory and cognitive disorders and there is currently no effective curative treatment for MS and other related demyelinating inflammatory diseases. Clinical research milestones in particular for the development of therapies with compounds capable of treating inflammation and demyelination for a more complete healthcare management of patients. One of the molecular mechanism, which has been poorly explored for the development of new therapeutic strategies in MS, is the demyelination associated with the overexpression of kallikrein 6 (KLK6), a major CNS serine protease. Indeed, KLK6 protein levels are upregulated in the cerebrospinal fluid of patients with MS. Excessive KLK6 activity would lead to cleavage of MBP and PLP proteins, preventing myelin regeneration and favoring demyelination. In line with this hypothesis, recombinant anti-KLK6 antibodies significantly delay onset and severity of clinical signs of the EAE mouse model of MS. Therefore, KLK6 and its proteolytic network constitute major players of the "degradome" associated with MS. Altered activities of these proteases are associated with several neuropathological features in the CNS, including demyelination, inflammation, neurodegeneration and disturbance of the BBB. In this context, the development of KLK6 inhibitors and of its associated proteolytic network appears as an innovative therapeutic avenue.

Over the past decade, high expectations have been raised on the development of remyelinating compounds, which could prevent neurodegeneration and thus disease progression in MS. These regenerative strategies have been primarily focused on endogenous remyelination mechanisms, but still require the identification of specific druggable targets. Therefore, our research project represents an unique opportunity for the development of compounds that can overcome MS disease course, through a targeted therapy for remyelination and neuroinflammation.

This multi-disciplinary project RESTORE grounds on strong and promising preliminary results with solid initial hits and on a consortium of three highly complementary and skilled partners. We aim to design second-generation of selective inhibitors selective of KLK6 and its proteolytic network, using both in silico and medicinal chemistry approaches, and evaluating and optimizing their specificity. To date, selective KLK6 inhibitors have not been identified. These hit compounds will be next evaluated: (i) in vitro to determine their inhibitory properties, their mechanisms of action, their selectivity spectrum on a large panel of serine proteases; and (ii) on cellular models to determine their pro-myelinating and anti-inflammatory properties. (iii) The therapeutic value of lead compounds will be then assessed in two mouse models of demyelination (EAE and LPC) that share some pathological features with MS. Lastly, mechanistic studies will performed in cellular models with KLK6 and PAR1 deficiency. The ultimate goals of our project are the identification and the preclinical validation of potent KLK6 inhibitors with combined anti-inflammatory and neuro-regenerative properties for further clinical development in MS and myelin-related diseases.