Ultomiris (ravulizumab) is a medication approved to treat four rare but serious conditions: paroxysmal nocturnal hemoglobinuria (PNH), atypical hemolytic uremic syndrome (aHUS), generalized myasthenia gravis (gMG), and neuromyelitis optica spectrum disorder (NMOSD). All four involve a part of the immune system called the complement system attacking the body’s own cells. Ultomiris works by blocking that process, and it’s given as an intravenous infusion once every eight weeks after an initial loading dose.
How Ultomiris Works
Your immune system includes a chain reaction called the complement cascade, which normally helps destroy bacteria and damaged cells. In certain diseases, this cascade misfires and attacks healthy tissue. Ultomiris is an engineered antibody that latches onto a specific protein in that cascade, called C5, and prevents it from splitting into fragments that would otherwise punch holes in cell membranes or trigger inflammation. By stopping this one step, the drug halts the downstream damage without shutting down the entire immune system.
Ultomiris is a longer-acting version of an older drug called Soliris (eculizumab), which targets the same protein but requires infusions every two weeks. The engineering changes in Ultomiris allow it to stay active in the bloodstream roughly four times longer, cutting infusion frequency in half.
Paroxysmal Nocturnal Hemoglobinuria (PNH)
PNH is a rare blood disorder where the complement system destroys red blood cells. This leads to severe anemia, fatigue, blood clots, and episodes of dark-colored urine (especially in the morning, which is where the name comes from). Ultomiris is approved for adults and children as young as one month old with PNH.
In pivotal trials, about 74% of patients who had never been on a complement-blocking drug avoided the need for blood transfusions while on Ultomiris, compared to 66% on the older drug eculizumab. Among patients who switched from eculizumab, the transfusion avoidance rate was even higher: roughly 88% on Ultomiris versus 83% on eculizumab. These results established that Ultomiris is at least as effective as its predecessor while requiring far fewer infusion visits.
Atypical Hemolytic Uremic Syndrome (aHUS)
In aHUS, the complement system attacks the lining of small blood vessels, causing tiny clots to form throughout the body. This damages the kidneys, destroys red blood cells, and depletes platelets. Without treatment, it can lead to kidney failure. Ultomiris is approved for aHUS in adults and children one month and older, though it is not used for the more common form of hemolytic uremic syndrome caused by Shiga toxin-producing E. coli infections.
In a study of 56 adults with aHUS, about 54% achieved a complete response within 26 weeks, meaning their blood counts normalized and kidney function improved by at least 25%. Children responded even better: in one pediatric group, nearly 78% of treatment-naive patients had a complete response in the same timeframe. For many patients, stopping the complement attack early enough can prevent permanent kidney damage.
Generalized Myasthenia Gravis (gMG)
Myasthenia gravis causes muscle weakness because antibodies block the signals between nerves and muscles. In the generalized form, this weakness can affect the arms, legs, and muscles used for breathing and swallowing. Ultomiris is approved for adults whose disease is driven by a specific type of antibody called anti-acetylcholine receptor (AChR) antibodies, which accounts for roughly 80 to 85% of gMG cases.
The complement system plays a direct role in this form of gMG: anti-AChR antibodies recruit complement proteins to the junction where nerves meet muscles, and those proteins destroy the receptors needed for muscle contraction. By blocking C5, Ultomiris interrupts that destruction and allows the muscle receptors to recover over time. Patients in clinical trials experienced meaningful improvements in daily activities like gripping objects, chewing, and climbing stairs.
Neuromyelitis Optica Spectrum Disorder (NMOSD)
NMOSD is a rare autoimmune condition that attacks the optic nerves and spinal cord, causing episodes of vision loss, paralysis, and severe pain. Most cases are driven by antibodies against a protein called aquaporin-4, found on cells that support nerve function. These antibodies trigger complement-mediated damage, making the disease a natural target for C5 inhibitors like Ultomiris.
In a clinical trial with a median treatment duration of about 73 weeks, patients on Ultomiris experienced zero confirmed relapses, representing a 98.6% reduction in relapse risk compared to placebo. For a disease where a single relapse can cause permanent blindness or paralysis, that level of protection is significant. Ultomiris is approved only for adults with NMOSD who test positive for anti-aquaporin-4 antibodies.
What Getting Ultomiris Looks Like
Ultomiris is given through an IV infusion. The first dose is a larger loading dose, followed two weeks later by maintenance infusions every eight weeks. The amount infused depends on body weight, with maintenance doses ranging from 3,000 mg for people under 132 pounds to 3,600 mg for those over 220 pounds. A newer, more concentrated formulation has reduced infusion times to roughly 25 to 75 minutes depending on weight, down from one to three hours with the original formulation.
Patients already on Soliris can switch to Ultomiris by receiving their loading dose at the time their next Soliris infusion would have been scheduled, then moving to the every-eight-week maintenance cycle two weeks later. The transition is straightforward and doesn’t require a washout period.
Important Safety Considerations
Because Ultomiris blocks part of the immune system’s ability to fight bacteria, it carries a boxed warning about a heightened risk of serious meningococcal infections. These infections, caused by the bacterium Neisseria meningitidis, can become life-threatening within hours. Patients must receive meningococcal vaccines at least two weeks before their first Ultomiris infusion. The drug is only available through a restricted safety program called REMS, which requires prescribers to enroll and ensure patients understand the infection risk and vaccination requirements.
Even with vaccination, the risk isn’t zero. Patients are typically advised to watch for signs like sudden fever, headache with stiff neck, or a spreading rash, and to seek emergency care immediately if these develop. This monitoring continues for as long as someone takes the drug and for a period after stopping it, since the medication can remain active in the body for weeks after the last dose.