What to Know About Imaavy for Warm Autoimmune Hemolytic Anemia (wAIHA)

Written by WebMD Editorial Contributors
Medically Reviewed by Patricia Weiser, PharmD on September 07, 2026

Warm autoimmune hemolytic anemia (wAIHA) is a rare condition in which your immune system mistakenly makes antibodies that attach to your own red blood cells, causing them to be destroyed. When red blood cells are destroyed faster than your body can replace them, this can lead to anemia and cause tiredness, weakness, shortness of breath, and other symptoms. The word "warm" refers to the fact that these antibodies are most active at normal body temperature.

In 2026, the FDA approved Imaavy (nipocalimab-aahu) as a treatment for wAIHA. Imaavy is approved for treating wAIHA in adults and children aged 12 years or older who are currently being treated or have previously been treated with corticosteroids.

Keep reading to learn how Imaavy works, how it is given, how it was studied, and what benefits were seen.

In wAIHA, the immune system produces a type of antibody called immunoglobulin G (IgG). These IgG antibodies are "autoantibodies," meaning they target the body's own cells. In this case, they attach to red blood cells and mark them for destruction. Lowering the level of these autoantibodies is one way to stop red blood cells from being destroyed.

Imaavy is a lab-made antibody called a neonatal Fc receptor (FcRn) blocker. Normally, the FcRn helps protect IgG antibodies from being broken down, which keeps IgG levels in the blood high. By blocking the FcRn, Imaavy lowers the overall amount of IgG in the blood, including the autoantibodies that attack red blood cells and drive wAIHA. With fewer of these autoantibodies present, fewer red blood cells are destroyed, which can help raise hemoglobin (the protein in red blood cells that carries oxygen). Imaavy does not cure wAIHA, but it may help manage the anemia it causes.

Imaavy is given into a vein through an IV line. Your health care provider will prescribe your dose based on your body weight, and it is prepared and given to you by a health care provider.

For wAIHA, you receive a starting dose of Imaavy as an infusion lasting at least 30 minutes. Four weeks later, you receive your next dose as an infusion lasting at least 15 minutes. After that, you continue to receive a dose every four weeks.

A few things to know about receiving Imaavy:

  • Your health care provider will likely monitor you for reactions during each infusion and for at least 30 minutes afterward. If you have a reaction, your provider may slow down the infusion, give you medicine before your infusion, or stop the infusion in case of a severe reaction.
  • Your health care provider may delay a dose or stop treatment if you develop an infection or certain side effects. If you miss a scheduled infusion, you should receive your next dose as soon as possible.
  • Certain vaccines, known as "live vaccines," are not recommended while you are being treated with Imaavy. Your health care provider may want you to be up to date on age-appropriate vaccines before you start.

A clinical trial known as the wAIHA Study was done to test Imaavy for the treatment of wAIHA. Participants were randomly assigned to receive either Imaavy or a placebo (an inactive infusion with no medicine in it). Neither the participants nor the study investigators knew which one each person was receiving during the study. This design, with a placebo comparison group, helps show whether the effects seen are truly due to the medicine.

To join the study, people needed a diagnosis of wAIHA for at least three months and had to be currently receiving, or have previously received, treatment for it. They also needed a hemoglobin level below 10 grams per deciliter (g/dL) — a sign that their red blood cells were being destroyed (hemolysis) — and a positive direct antiglobulin test (DAT), which detects antibodies attached to red blood cells.

To see how well Imaavy worked, the study compared results of people who received Imaavy every four weeks vs. those who received placebo during a 24-week period. People were allowed to continue their stable existing wAIHA treatment during the study.

Here are some details about the 77 participants at the start of the study:

  • The median age was 59 years, meaning about half were younger and half were older, and ages ranged from 24 to 86 years.
  • About 53% were women, and the rest were men.
  • About 47% were White, 34% were Asian, 1% were Black or African American, and 18% were another race or did not report race.
  • About 5% were Hispanic or Latino, 87% were not Hispanic or Latino, and 8% did not report ethnicity.
  • The median time since diagnosis was two years, ranging from less than a year up to 16 years.
  • Most participants (more than 85%) were also taking corticosteroids.
  • About 25% of participants were taking other immunosuppressant medicines.

Imaavy's effectiveness was based on how many people had a lasting increase in hemoglobin, called a "durable hemoglobin response." This was defined as reaching a hemoglobin level of at least 10 g/dL along with an increase of at least 2 g/dL from where they started. This improvement had to be maintained for at least three visits in a row (a minimum of 28 days, with the improvement starting by Week 16). All of this had to happen without needing extra treatment to control their wAIHA (rescue therapy).

The number of participants that achieved a durable hemoglobin response in the study was: 

  • Imaavy: 9 out of 38 (about 24%)
  • Placebo: 3 out of 39 (about 8%)

This difference was statistically significant, meaning it was unlikely to be due to chance alone. Overall, hemoglobin levels tended to improve more with Imaavy than with placebo over the course of the study.

The study also looked at fatigue (tiredness) using a patient questionnaire called FACIT-Fatigue, where higher scores mean less fatigue. On average, people in the Imaavy group reported an improvement in their fatigue scores over 24 weeks, while those in the placebo group did not.

Here are a few things to keep in mind about these results:

  • Imaavy does not cure wAIHA. 
  • Not everyone who took it achieved a durable hemoglobin response.
  • Most participants did not reach that specific goal, even though hemoglobin levels overall tended to improve.

Your own results may be different from those seen in the study. Your health care provider can help decide whether Imaavy is an option for you and explain what to expect.

In the study, average hemoglobin levels in the Imaavy group began to rise within the first few weeks of treatment. However, the durable hemoglobin response measured in the study required that improvement to be sustained through week 16. So, it can take a few months to know whether treatment is working.

Response time can vary from person to person. Your health care provider will monitor you with blood tests during treatment and let you know how well Imaavy is working for you.

Imaavy is made by Janssen, a Johnson & Johnson company, which offers patient support and resources. Programs like these may help some people with costs and coverage, based on eligibility. To learn what support may be available and whether you qualify, visit the drugmaker's website or call 800-526-7736. Your care team may also be able to connect you with other financial-assistance resources.

Imaavy is not right for everyone. To help decide whether it is an option for you, your health care provider will consider your diagnosis, the treatments you have already tried, and your overall health.

Imaavy is FDA-approved for adults and children aged 12 years or older with wAIHA who are currently being treated or have previously been treated with corticosteroids. In other words, it is generally considered when corticosteroids have already been part of your treatment.

You should not receive Imaavy if you have had a serious allergic reaction to nipocalimab-aahu (the active ingredient in Imaavy) or to any of its other ingredients.

Before starting Imaavy, tell your health care provider about all of your medical conditions, including if you:

Also, tell your provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements, because Imaavy can affect the way some medicines work.

Your health care provider can help you weigh the potential benefits and risks and decide whether Imaavy is a good fit for you.

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