Anti-neutrophil cytoplasmic antibody positive vasculitis is a group of rare autoimmune diseases that cause inflammation and damage to small blood vessels throughout the body. Treatment focuses on controlling inflammation, preventing organ damage, and helping patients achieve periods of remission where symptoms are under control. While standard medications have been used for decades, newer therapies tested in clinical trials offer hope for better outcomes with fewer side effects.

Managing a Complex Disease: Goals and Approaches

The main goal of treating anti-neutrophil cytoplasmic antibody positive vasculitis—also called ANCA-associated vasculitis or AAV—is to control the inflammation that damages blood vessels before it causes permanent harm to vital organs. This inflammation can affect many parts of the body, including the kidneys, lungs, sinuses, nerves, and skin. Without treatment, the disease can lead to serious complications such as kidney failure, lung bleeding, or nerve damage.^[1]

Treatment strategies depend on several factors. The severity of the disease plays a major role—some patients have mild symptoms affecting only one or two organs, while others have severe, life-threatening involvement of multiple organs. The specific type of vasculitis also matters, as there are three main forms: granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). Additionally, whether a patient is newly diagnosed or experiencing a relapse—when the disease returns after a period of control—influences treatment decisions.^[2]

Doctors typically divide treatment into two phases. The first phase, called induction therapy, aims to quickly bring the disease under control and stop active inflammation. This phase usually lasts several months and uses stronger medications. The second phase, maintenance therapy, focuses on keeping the disease in remission for as long as possible while using lower doses of medications to reduce side effects. This phase can last for years, as ANCA-associated vasculitis has a tendency to come back even after successful initial treatment.^[7]

Beyond approved medications, researchers are actively studying new treatments in clinical trials. These studies test whether experimental drugs can work better than existing options, cause fewer side effects, or help patients who don’t respond well to standard treatments. Clinical trials have already led to important improvements in how doctors treat ANCA-associated vasculitis, and ongoing research continues to explore innovative approaches.^[10]

Standard Treatment: The Foundation of Care

For decades, the cornerstone of treating ANCA-associated vasculitis has been a combination of medications that suppress the immune system. These drugs work by calming down the overactive immune response that causes blood vessel inflammation. The two main classes of medications used in standard treatment are corticosteroids (also called glucocorticoids) and immunosuppressive drugs.^[7]

Corticosteroids: Quick but Powerful

Corticosteroids, such as prednisone or methylprednisolone, are almost always used when ANCA-associated vasculitis is first diagnosed or when it flares up. These medications reduce inflammation very quickly and effectively. Doctors typically start with high doses to rapidly control the active disease, then gradually reduce the dose over several months. The goal is to use the lowest dose possible for the shortest time needed, because corticosteroids can cause significant side effects when used long-term.^[7]

In recent years, treatment guidelines have shifted toward using lower doses of corticosteroids and reducing them more quickly than in the past. Studies have shown that a rapidly reducing schedule of steroids—starting high but tapering down faster—can be just as effective at controlling the disease while causing fewer serious infections and other complications. In some cases, doctors aim to stop corticosteroids completely within six months of starting treatment.^[7]

Common side effects of corticosteroids include weight gain, increased blood sugar levels (which can lead to diabetes), weakened bones (osteoporosis), high blood pressure, mood changes, difficulty sleeping, and increased risk of infections. Because of these problems, doctors carefully monitor patients taking corticosteroids and may prescribe additional medications to protect bone health or control blood pressure.^[12]

Cyclophosphamide: A Traditional Workhorse

Cyclophosphamide is a powerful immunosuppressive drug that has been used for many years to treat severe ANCA-associated vasculitis. It works by interfering with immune cells that contribute to blood vessel inflammation. Cyclophosphamide is particularly effective for patients with severe kidney involvement or lung bleeding. Doctors usually give it either as daily pills or as intravenous infusions every few weeks for several months during the induction phase.^[8]

While cyclophosphamide is effective, it carries significant risks. Side effects can include bladder problems (including an increased risk of bladder cancer with long-term use), reduced fertility (particularly concerning for younger patients who may want to have children), increased susceptibility to infections, nausea, hair loss, and lower blood cell counts. Because of these concerns, doctors have developed protocols that use cyclophosphamide for the shortest time necessary and at the lowest effective dose. Patients who receive cyclophosphamide need regular blood tests to monitor for complications.^[8]

Rituximab: A Newer Standard Option

Rituximab has become an important alternative to cyclophosphamide for treating ANCA-associated vasculitis. This medication targets and depletes B cells, a type of white blood cell that plays a role in producing the abnormal antibodies that attack blood vessels. Rituximab is given as an intravenous infusion, typically in two to four doses over several weeks initially, then at regular intervals to maintain remission.^[7]

Clinical trials have shown that rituximab works as well as cyclophosphamide for bringing ANCA-associated vasculitis under control, and it may be even more effective for preventing relapses, especially in patients with granulomatosis with polyangiitis or those who have antibodies against a protein called PR3. Rituximab is now considered the preferred treatment for patients who have had a previous relapse of their disease. It also may be preferred for younger patients concerned about fertility, as it doesn’t carry the same risks to reproductive health as cyclophosphamide.^[8]

Side effects of rituximab include infusion reactions (such as fever, chills, or rash during or shortly after the infusion), increased risk of infections, and progressive depletion of antibodies over time, which can leave patients more vulnerable to certain infections. Patients receiving rituximab need monitoring of their immunoglobulin levels and may require preventive measures against infections, such as vaccinations before starting treatment or prophylactic antibiotics.^[11]

Maintenance Therapy: Keeping the Disease in Check

After the initial treatment brings the vasculitis under control—a state called remission—patients need ongoing treatment to prevent the disease from coming back. Several medications are used for maintenance therapy. Rituximab has emerged as the most effective option, with studies showing it prevents relapses better than older alternatives. Doctors typically give rituximab infusions every six months for at least two to four years during the maintenance phase.^[7]

Other medications used for maintenance include azathioprine and methotrexate. These are older immunosuppressive drugs taken as daily pills. Azathioprine works by interfering with DNA production in immune cells, while methotrexate blocks certain enzymes needed for cell growth. Both drugs help keep the immune system in check but are generally less effective at preventing relapses compared to rituximab. Side effects can include liver problems, nausea, increased infection risk, and lower blood cell counts. Patients taking these medications need regular blood tests to monitor liver function and blood counts.^[9]

Another maintenance option is mycophenolate mofetil, which inhibits a specific pathway that immune cells need to multiply. This drug may be used in patients who cannot tolerate or don’t respond well to other maintenance medications. The choice of maintenance therapy depends on the individual patient’s situation, including which organs are affected, whether they’ve had relapses before, their tolerance of different medications, and their personal preferences.^[9]

Special Procedures: Plasma Exchange

For patients with very severe kidney involvement or bleeding in the lungs, doctors may recommend a procedure called plasma exchange (also known as plasmapheresis). This treatment involves removing blood from the patient, separating out the liquid portion (plasma) that contains harmful antibodies, and returning the blood cells with fresh plasma or a plasma substitute. The goal is to rapidly remove circulating antibodies that are attacking blood vessels.^[7]

While plasma exchange was widely used in the past, recent large studies have shown mixed results about its benefits. A major trial called PEXIVAS found that plasma exchange didn’t improve the combined outcome of death or end-stage kidney disease. However, a careful analysis of multiple studies suggested that plasma exchange might help reduce the risk of kidney failure in patients who have very severe kidney damage at the start—specifically those with a serum creatinine level above 300 micromoles per liter. Because of these findings, plasma exchange is now typically reserved for selected patients with the most severe disease rather than being used routinely.^[7]

Duration of Treatment

The total duration of treatment varies considerably among patients. The initial induction phase typically lasts three to six months. If the disease responds well, doctors transition to maintenance therapy, which usually continues for at least two to four years. Some patients may need even longer treatment if they have factors that increase their risk of relapse, such as specific types of antibodies or a history of previous relapses. The decision about when to stop maintenance therapy involves weighing the risk of relapse against the risks of long-term immunosuppression, including infections and low antibody levels.^[9]

Throughout treatment, patients require regular monitoring. This includes blood tests to check kidney function, look for signs of disease activity, measure antibody levels, and watch for medication side effects. Urine tests help detect early signs of kidney involvement. Doctors also monitor for infections and other complications. The frequency of monitoring is highest when the disease is active or when starting new medications, then becomes less frequent during stable remission.^[11]

Treatment in Clinical Trials: New Horizons

While standard treatments have dramatically improved outcomes for patients with ANCA-associated vasculitis compared to decades ago, there’s still room for improvement. Many patients experience disease relapses, treatment side effects can be significant, and some patients don’t respond well to existing medications. This has driven researchers to develop and test new therapies that might work better or cause fewer problems.^[10]

Avacopan: Targeting the Complement System

One of the most promising drugs to emerge from recent clinical trials is avacopan, a medication that works differently from traditional immunosuppressants. Avacopan blocks a specific part of the immune system called the complement system, which plays a role in the inflammation that damages blood vessels in ANCA-associated vasculitis. Specifically, avacopan inhibits the C5a receptor, preventing a particular complement protein from activating inflammatory cells.^[7]

The major advantage of avacopan is that it allows doctors to reduce or eliminate corticosteroids while still effectively controlling the vasculitis. In a Phase III clinical trial called ADVOCATE, patients who received avacopan along with standard immunosuppressive therapy were able to use much lower doses of corticosteroids than patients who received traditional high-dose steroid therapy. Importantly, disease control was just as good or slightly better with avacopan, and patients experienced fewer steroid-related side effects.^[11]

Avacopan is taken as pills twice daily. Side effects can include nausea, headache, and in some cases, liver enzyme elevations that require monitoring. The drug has been approved in several countries for treating severe active ANCA-associated vasculitis. Current guidelines recommend considering avacopan early in treatment, particularly for patients who are at high risk for steroid-related complications or who have had serious problems with steroids in the past.^[7]

Mepolizumab: For Eosinophilic Granulomatosis with Polyangiitis

Mepolizumab represents an important advance specifically for patients with eosinophilic granulomatosis with polyangiitis (EGPA), one of the three main types of ANCA-associated vasculitis. EGPA differs from the other types because it involves high numbers of eosinophils, a type of white blood cell, and often causes asthma. Mepolizumab works by blocking interleukin-5, a chemical signal that promotes the growth and survival of eosinophils.^[7]

Clinical trials have shown that mepolizumab helps EGPA patients achieve and maintain remission while allowing them to reduce their dose of corticosteroids. The medication is given as an injection under the skin once every four weeks. By specifically targeting the mechanism that drives eosinophil-related inflammation, mepolizumab addresses a key feature of EGPA that standard immunosuppressants don’t target as directly. This drug has been approved for treating EGPA in several countries and represents the first therapy specifically developed for this form of vasculitis.^[7]

Other Emerging Therapies Under Investigation

Researchers continue to explore additional new treatments in ongoing clinical trials. Some of these approaches target different parts of the immune system or use novel mechanisms to reduce inflammation and prevent blood vessel damage. While these therapies are still being studied and haven’t yet been approved for routine use, they offer hope for future improvements in treatment.^[10]

One area of investigation involves refining the use of existing drugs. Studies are looking at different dosing schedules for rituximab, exploring whether giving the drug based on monitoring of B cell counts or antibody levels works better than giving it at fixed time intervals. Other trials are testing whether certain combinations of medications might work better than current standard combinations, or whether some patients can safely stop maintenance therapy earlier than the current two-to-four-year recommendation.^[10]

Research is also focused on identifying biomarkers—measurable indicators in blood or other samples that could help predict which patients are at highest risk for relapses or serious organ damage. If doctors could identify these high-risk patients early, they might be able to adjust treatment more precisely, using more intensive therapy for those who need it while sparing others from unnecessary medication exposure.^[10]

Understanding Clinical Trial Phases

Clinical trials testing new treatments for ANCA-associated vasculitis typically progress through several phases. Phase I trials are small studies, often with 20 to 80 participants, that primarily test whether a new drug is safe and help determine appropriate doses. These trials may enroll patients with various types of vasculitis or even other autoimmune diseases to gather initial safety information.^[10]

Phase II trials are larger studies that begin to test whether the new treatment actually works to control the disease. These trials typically involve 100 to 300 patients and carefully measure disease activity, looking at whether patients achieve remission, whether their symptoms improve, and what side effects occur. Phase II trials help researchers understand the optimal dose and schedule for the new medication.^[10]

Phase III trials are the largest and most definitive studies, often involving several hundred to over a thousand patients. These trials directly compare the new treatment to the current standard treatment to determine whether the new approach is at least as good as or better than what doctors already use. Phase III trials provide the evidence needed for regulatory agencies to approve a new medication for use in treating ANCA-associated vasculitis. The trials that led to approval of rituximab, avacopan, and mepolizumab were all Phase III studies.^[10]

Participating in Clinical Trials

Clinical trials for ANCA-associated vasculitis are conducted at medical centers around the world, including locations in the United States, Europe, and other regions. Eligibility to participate depends on many factors, including the specific type of vasculitis a patient has, how severe their disease is, what treatments they’ve received before, and other health conditions they may have. Each trial has specific inclusion and exclusion criteria designed to ensure patient safety and generate meaningful results.^[10]

Patients interested in clinical trials should discuss this option with their doctors. Participation in a trial means receiving careful monitoring and potentially gaining access to new treatments before they become widely available. However, it also means accepting some uncertainty, as experimental treatments haven’t been studied as extensively as approved medications. Clinical trial participants make an important contribution to advancing medical knowledge that will help future patients with ANCA-associated vasculitis.^[10]

Most common treatment methods

• Corticosteroids (Glucocorticoids)
  • Medications like prednisone and methylprednisolone that rapidly reduce inflammation throughout the body
  • Used at high doses initially, then tapered down over several months
  • Current guidelines recommend rapidly reducing regimens to minimize side effects
  • Side effects include weight gain, diabetes risk, bone weakening, high blood pressure, and increased infection risk
• Cyclophosphamide
  • A traditional immunosuppressive medication that interferes with immune cell function
  • Particularly effective for severe kidney disease or lung bleeding
  • Given as daily pills or periodic intravenous infusions
  • Carries risks including bladder problems, reduced fertility, infections, and blood cell count changes
• Rituximab
  • A newer treatment that depletes B cells, which produce harmful antibodies
  • Works as well as cyclophosphamide for initial disease control
  • More effective than older drugs at preventing relapses, especially in GPA
  • Preferred for patients with previous relapses and for maintenance therapy
  • Given as intravenous infusions initially and then at regular intervals
  • Can cause progressive antibody depletion requiring infection monitoring
• Azathioprine and Methotrexate
  • Older immunosuppressive medications used for maintenance therapy
  • Taken as daily pills to keep the disease in remission
  • Less effective than rituximab at preventing relapses
  • Require regular blood tests to monitor for liver problems and low blood counts
• Mycophenolate Mofetil
  • An alternative immunosuppressive drug for maintenance therapy
  • Inhibits a specific pathway needed for immune cell multiplication
  • Used in patients who cannot tolerate other maintenance medications
• Avacopan
  • A newer medication that blocks the C5a receptor, part of the complement system
  • Allows significant reduction or elimination of corticosteroids
  • Shown in Phase III trials to control disease as effectively as high-dose steroids
  • Taken as pills twice daily
  • May cause nausea, headache, or liver enzyme elevations
• Mepolizumab
  • Specifically for eosinophilic granulomatosis with polyangiitis (EGPA)
  • Blocks interleukin-5 to reduce eosinophil numbers and activity
  • Helps achieve remission and reduce corticosteroid doses in EGPA patients
  • Given as a monthly injection under the skin
• Plasma Exchange
  • A procedure that removes harmful antibodies from blood
  • May help prevent kidney failure in patients with very severe kidney damage
  • Typically reserved for selected patients rather than used routinely
  • Involves multiple sessions over one to two weeks