Duchenne muscular dystrophy (DMD) is a disease that causes progressive muscle weakness, loss of skeletal and heart muscle tissue, degeneration, and eventual death. Muscle weakness is usually noticeable by 3 or 4 years, and early signs may include delayed ability to sit, stand, or walk and difficulties learning to speak. DMD is caused by mutations in the DMD gene. It is inherited in an X-linked recessive pattern; therefore, it primarily affects males, with a prevalence of approximately 1 in 3,500 boys. However, it may also occur in people who do not have a family history of DMD. While there is no known cure for DMD, there are treatments that can help control symptoms. Corticosteroids, such as prednisone and deflazacort (Emflaza), can help muscle strength and delay the progression of certain types of muscular dystrophy. However, prolonged use has substantial side effects. The recently approved FDA drugs for DMD, Viltepso, Vyondys 53, and Exondys 51, are antisense oligonucleotides, each designed to treat a specific confirmed mutation of the DMD gene. Consequently, less than one-quarter of DMD patients may respond to these treatments, and studies are ongoing to demonstrate their clinical benefit 1,2.

Therefore, there is a need for an effective treatment for the clinical pathologies of DMD. Many of the DMD pathologies are caused by dysregulation of the extracellular matrix (ECM), mostly collagen, which leads to restricted muscle repair and regeneration, enhancement of inflammation and exacerbation of disease progression.

LOX is naturally synthesized and secreted as a 50-kDa inactive proenzyme, which is processed by proteolytic cleavage to a functional 32-kDa enzyme (LOX) and an 18-kDa prodomain (LPD). A stable form of the lysyl oxidase prodomain was fused to an Fc antibody fragment (Fc-LPD) to generate a specific and stable inhibitor for LOX. Fc-LPD is expressed in dimer formation, creating a minimized antibody-like inhibitor. Fc-LPD affinity and stability measurements were performed against LOX, determining the binding affinity (EC50= 274nM) and dissociation constant (Kd=32nM). Preliminary in vivo studies in a DMD mouse model system showed improvement in functional tests, such as rotarod running and hanging tests as well as inhibition of fibrosis accumulation and promotion of normal collagen organization (Figure 1).