According to BioSpace, biotechnology company Argenx recently announced positive results from their Phase III ADAPT clinical trial. The company, who seeks to find breakthroughs in immunology and translate them to meet unmet patient needs, was exploring efgartigimod as a potential treatment for myasthenia gravis (MG).

Myasthenia Gravis (MG)

Myasthenia gravis (MG) is an autoimmune neuromuscular disorder whose name stands for “grave muscle weakness.” Like other autoimmune disorders, the body mistakenly attacks itself. Normally, your immune system reacts to foreign invaders like germs, bacteria, or viruses. But in myasthenia gravis, the body begin to attack certain proteins in the body that play a role in nerve and muscle communication. As a result, the brain and muscles can’t communicate properly, leading to muscle weakness and poor muscle response.

There are multiple forms of myasthenia gravis:

• Congenital. Also known as congenital myasthenia syndrome, congenital MG is the rarest form of the disorder. It is not autoimmune but genetic, where RAPSN, CHAT, DOK7, COLQ, or CHRNE gene mutations (rather than immune response) inhibit the proteins. Symptoms begin in infancy and last a lifetime. There are only an estimated 600 cases ever diagnosed. Contrastingly, the autoimmune form affects around 20 out of every 100,000 people.
• Transient neonatal. Transient neonatal myasthenia gravis begins in infancy. However, symptoms may end within a few weeks of birth.
• Juvenile. Juvenile myasthenia gravis is more common in females than males. It generally begins in adolescence. While symptoms can last a lifetime, those with this form may experience periods of remission.

Symptoms of myasthenia gravis grow worse with activity. But only 10% of patients ever experience life-threatening respiratory complications. For most people, treatment helps reduce symptoms and improve quality of life. Symptoms include:

• Double vision or blurred vision
• Slurred speech
• Arm, leg, eye, mouth, and throat muscle weakness
• Drooping eyelids
• Changes in gait (how you walk)
• Shortness of breath
• Fatigue
• Trouble swallowing, chewing, or eating

If you or someone you know has MG and is experiencing extreme difficulty with breathing, please contact your doctor immediately. Learn more about myasthenia gravis here.

Argenx Trial

Efgartigimod

According to Argenx, efgartigimod is:

a first-in-class investigational antibody fragment to target the neonatal Fc receptor (FcRn). Efgartigimod is being evaluated for the treatment of patients with severe autoimmune diseases with confirmed presence of pathogenic immunoglobulin G, IgG autoantibodies, where a severe unmet medical need exists.

Basically, the therapy is meant to reduce levels of IgG antibodies, which interrupt the brain-muscle communication. The company is also looking at efgartigimod as a potential treatment for:

• Primary immune thrombocytopenia – currently in a Phase III trial
• Chronic inflammatory demyelinating polyneuropathy – currently in a Phase II trial
• Pemphigus vulgaris – currently in a Phase II trial

Other treatments for myasthenia gravis include corticosteroids, non-steroidal immunosuppressants, acetylcholinesterase inhibitors, and therapies like Alexion’s Soliris. Additionally, there are other companies working to create FcRn inhibitors:

• Momenta Pharmaceuticals: nipocalimab
• UCB: rozanolix-izumab
• Alexion: ALXN1830
• Immunovant: IMVT-1401

However, Argenx believes that efgartigimod is one of the safest and most effective options for treatment.

Phase III Results for Myasthenia Gravis

The Phase III ADAPT trial enrolled 167 adults with generalized myasthenia gravis (gMG) from Japan, Europe, and North America. Prior to the trial, all participants were already taking some form of treatment. The trial was:

• Double-blind: this means that neither the researchers or those participating knew which group is the control group and which is actually receiving the treatment.
• Randomized: participants are randomly allocated to groups receiving different treatments.
• Placebo-controlled: participants are either given the therapy (efgartigimod) or a placebo, an inactive treatment.
• Multi-center: the trial is conducted at more than one clinic or medical center.

Patients received either a placebo or efgartigimod for 26 weeks (just about 6 months). With a 1:1 study At the end of the trial, patients could choose to also participate in the open-label extension ADAPT Plus. Open-label means that healthcare providers and participants are both aware of what group is receiving what treatment.

The primary endpoint (or goal) for this trial was to see how many people improved their Myasthenia Gravis Activities of Daily Living (MG-ADL) score by at least 2 points for 4 consecutive weeks. According to an article in the Annals of the New York Academy of Science, the MG-ADL score:

is an eight-item patient-reported scale developed to assess MG symptoms and their effects on daily activities.

The Myasthenia Gravis Foundation of America notes in their resources for professionals that a 2 point increase indicates clinical improvement. So, the trial results show that:

• 67.7% of patients who received efgartigimod achieved the primary endpoint.
• 29.7% of patients who received a placebo achieved the primary endpoint.

Thus, 38% more patients achieved the endpoint when on efgartigimod. Additionally, the data shows that the treatment was also safe and well-tolerated.

Next Steps

Says CMO Wim Parys:

“Efgartigimod [helped patients achieve] minimal or no symptoms after treatment. In addition, we saw responses that lasted beyond 8 or 12 weeks, supporting our plans to offer individualized dosing schedules.”

By the end of 2020, Argenx will submit a Biologics License Application to the FDA. In short, this means they are applying to manufacture and sell efgartigimod. Their goal is for their therapy to treat patients by 2021.