In a mid-November 2022 press release from biopharmaceutical company CANbridge Pharmaceuticals, Inc. (“CANbridge”), the company shared that its therapeutic option CAN106, which binds to and neutralizes C5 in the complement system, has earned Orphan Drug designation from the FDA. The designation was granted for the treatment of patients with myasthenia gravis (MG). 

CANbridge explains that CAN106 is:

a long-acting, recombinant human monoclonal antibody that [targets] C5. C5 inhibition is a validated mechanism of action in numerous hematologic, renal, and neurologic diseases, with development potential for the treatment of multiple complement-mediated disorders.

Outside of myasthenia gravis, CANbridge is also developing CAN106 as a potential therapeutic option for those living with paroxysmal nocturnal hemoglobinuria (PNH). So far, studies have shown that CAN106 is safe, well-tolerated, and has favorable pharmacokinetics and pharmacodynamics. 

What is Orphan Drug Designation?

Orphan Drug designation is granted by the FDA to drugs or biologics that are intended to treat, diagnose, or prevent rare diseases or rare conditions. In the United States, a rare condition is one affecting fewer than 200,000 people. This designation comes with a variety of incentives for drug developers, including:

• Fee waivers
• Tax credits
• Increased regulatory assistance
• Seven years of market exclusivity upon drug approval

An Overview of Myasthenia Gravis (MG) 

Myasthenia gravis, though rare, is the most common autoimmune neuromuscular disorder. Its name translates to “grave muscle weakness,” which correlates to the condition’s main symptoms: varying degrees of fatigue and weakness in voluntarily controlled muscle groups. These symptoms often worsen with activity but can improve with rest. Although MG is considered to be an autoimmune disorder, there is a form called congenital myasthenia gravis which is inherited; this form results from RAPSN, DOK7, CHAT, COLQ, or CHRNE mutations. 

In around 10% of cases, those with myasthenia gravis can develop life-threatening respiratory complications. However, this is fairly uncommon, with 90% of people avoiding these complications. Regardless, MG is considered a progressive condition, and at this time no cures exist. Symptoms onset depends on the specific subtype. For example, congenital myasthenia gravis begins in infancy; transient neonatal in infancy, though it ends later; and juvenile in adolescence. 

Symptoms associated with MG can, but do not always, include:

• Muscle weakness in the arms, legs, eyes, mouth, and throat
• Impaired speech
• Fatigue
• Shortness of breath
• Difficulty making certain facial expressions
• Changes in gait 
• Drooping eyelids
• Difficulty chewing or swallowing
• Blurred or double vision
• Slurred speech