About Jakafi®

What is Jakafi?

Jakafi (JAK-ah-fye) is a prescription medicine available as a pill. It is the only medicine approved by the Food and Drug Administration (FDA) to treat intermediate or high-risk myelofibrosis (MF). This drug, ruxolitinib, has been used to treat more than 9,800 patients with MF worldwide.

Jakafi is used to treat people with intermediate or high-risk MF, including primary MF, post–polycythemia vera (PV) MF, and post–essential thrombocythemia (ET) MF.

It is estimated that 80% of people diagnosed with MF have intermediate or high-risk MF.

Learn about the clinical trials for Jakafi

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How does Jakafi work?

Myelofibrosis is a complex condition, and researchers are still trying to discover its exact cause. Researchers now think one cause is that JAK proteins, which communicate within blood cells, send too many signals. When JAKs send too many signals, they cause the body to make the wrong number of blood cells. This chain of events is called overactive JAK signaling.

JAK signaling may become overactive in many ways. One way is by a JAK mutation. A mutation is a small change in the DNA that causes proteins to act differently than normally intended. All people with myelofibrosis are believed to have overactive JAK signaling even if they do not have a JAK mutation.

Jakafi works by targeting JAKs, which control the production of blood cells. In doing so, Jakafi reduces overactive JAK signaling.

What are some possible benefits of Jakafi?

Jakafi has been shown to reduce spleen size and improve the core symptoms of MF in appropriate patients.

How does Jakafi affect spleen size?

Enlarged spleen

Many people with MF have enlarged spleens, which can cause symptoms such as abdominal discomfort, pain under the left ribs, and an early feeling of fullness. In people with intermediate or high-risk MF, Jakafi may significantly reduce spleen size.

In a clinical trial, Jakafi reduced the size of the spleen by a set goal of at least 35% in 42% of people with MF when measured after 6 months of treatment. In contrast, less than 1% of people taking a placebo (sugar pill) reached that goal.

Also in this trial, 99% of people on Jakafi had some response to therapy. This means that they had a reduction in spleen size even if it was less than the 35% goal achieved by some patients.

How does Jakafi affect symptoms?

In that same clinical trial, Jakafi was also said to work if people reached a goal of 50% or greater improvement in their Total Symptom Score, or TSS, after 6 months of treatment. The researchers found that 46% of the people taking Jakafi reached this goal, compared with only 5% of people taking placebo. In fact, 80% of the patients taking Jakafi had some level of symptom improvement—even if it was less than 50%—while most of the people taking placebo actually saw their symptoms worsen.

The symptoms included in the TSS were:
  • Abdominal discomfort
  • Itching
  • Early feeling of fullness
  • Night sweats
  • Pain under the left ribs
  • Bone/muscle pain
Although every person taking Jakafi may not experience the same results, Jakafi may help reduce these core symptoms and the size of the spleen.

What long-term data for Jakafi are available?

In key clinical trials for Jakafi, patients were followed for up to 3 years. One of the things the researchers looked at was the probability that patients with Jakafi or other myelofibrosis treatments would be alive at 1, 2, and 3 years of treatment.

Every person is unique. How your myelofibrosis progresses and how you will respond to Jakafi depends on your individual circumstances. Talk to your doctor about how patients responded to Jakafi in the key clinical trials, and ask about the potential long-term effects of Jakafi treatment.

Is Jakafi a long-term treatment?

Myelofibrosis is a chronic disease that progresses—or gets worse—over time. By taking Jakafi as prescribed by your doctor, you may be able to continue receiving the benefits of this medicine. Once treatment with Jakafi stops, the spleen is expected to get bigger again, and symptoms are expected to return. The symptoms may return in as little as a week.

Your doctor may allow up to 6 months to see if Jakafi is working to reduce the size of your spleen and to improve your symptoms. If you do not have a reduction in spleen size or an improvement in your symptoms after 6 months of treatment, your doctor may have you stop taking Jakafi.

What are possible side effects of Jakafi?

Jakafi can cause serious side effects, including:

Low blood counts: Jakafi may cause your platelet, red blood cell, or white blood cell counts to be lowered. If you develop bleeding, stop taking Jakafi and call your healthcare provider. Your healthcare provider will perform blood tests to check your blood counts before you start Jakafi and regularly during your treatment. Your healthcare provider may change your dose of Jakafi or stop your treatment based on the results of your blood tests. Tell your healthcare provider right away if you experience unusual bleeding, bruising, fatigue, shortness of breath, or a fever.

Infection: You may be at risk for developing a serious infection while taking Jakafi. Tell your healthcare provider if you develop symptoms such as chills, nausea, vomiting, aches, weakness, fever, or painful skin rash or blisters.

The most common side effects of Jakafi include dizziness and headache.

These are not all the possible side effects of Jakafi. Ask your healthcare provider or pharmacist for more information. Tell your healthcare provider about any side effect that bothers you or that does not go away.

Before taking Jakafi, tell your healthcare provider about all the medications, vitamins, and herbal supplements you are taking and all your medical conditions, including if you have an infection, have or had liver or kidney problems, are on dialysis, or have any other medical condition. Take Jakafi exactly as your healthcare provider tells you. Do not change or stop taking Jakafi without first talking to your healthcare provider. Do not drink grapefruit juice while taking Jakafi.

Women should not take Jakafi while pregnant or planning to become pregnant, or if breast-feeding.

Please see the Full Prescribing Information, which includes a more complete discussion of the risks associated with Jakafi.