When someone is diagnosed with a blood cancer like myelofibrosis, one of the first questions they often ask about treatment is: “Is it chemotherapy?” One of the newer medicines for this condition is VONJO (generic name: pacritinib). But is VONJO a type of chemotherapy? Let’s explore what this medicine is, how it works, and how it differs from traditional chemotherapy.
What Is VONJO?
VONJO is a prescription medication approved by the U.S. Food and Drug Administration (FDA) in 2022 for adults with intermediate- or high-risk myelofibrosis — a rare type of bone marrow cancer.
Myelofibrosis happens when scar tissue builds up inside the bone marrow, preventing it from making healthy blood cells. This can cause low blood counts, anemia, fatigue, and an enlarged spleen.
VONJO is specifically approved for patients whose platelet count is below 50,000 per microliter, which is a group that often cannot tolerate standard myelofibrosis drugs.
So, Is VONJO a Chemotherapy Drug?
No — VONJO is not considered traditional chemotherapy.
Chemotherapy, in the classic sense, refers to cytotoxic drugs that kill rapidly dividing cells throughout the body. These drugs attack both cancerous and healthy cells, which often leads to widespread side effects like hair loss, nausea, and immune suppression.
VONJO, on the other hand, belongs to a newer class of medicines called targeted therapies — specifically, it is a kinase inhibitor. Instead of killing all rapidly dividing cells, VONJO targets specific enzymes involved in the disease process.
How VONJO Works
VONJO is a JAK2/IRAK1 inhibitor, meaning it blocks specific proteins called kinases that drive abnormal blood cell production and inflammation in myelofibrosis.
By blocking these pathways, VONJO helps:
- Reduce spleen size (which often becomes enlarged due to abnormal blood cell buildup)
- Improve symptoms such as fatigue, night sweats, and bone pain
- Stabilize blood counts in patients who have very low platelets
This precise mechanism of action is what makes VONJO a targeted therapy, not a chemotherapy drug.
How Is VONJO Different from Chemotherapy?
FeatureChemotherapyVONJO (Pacritinib)
Type of Drug: Cytotoxic (kills rapidly dividing cells), Targeted therapy (kinase inhibitor)
Mode of Action: Damages DNA and stops all cell division. Blocks specific enzymes (JAK2, IRAK1)
Effect on Healthy Cells Affects healthy and cancer cells alike. Mostly affects diseased pathways.
Common Side Effects: Hair loss, nausea, fatigue, and infections. Diarrhea, nausea, anemia, swelling
Form: Often given intravenously, Oral capsule (taken by mouth)
As you can see, VONJO’s approach is far more targeted and generally causes fewer systemic side effects than traditional chemotherapy.
Who Is VONJO For?
VONJO is approved for:
- Adults with intermediate- or high-risk myelofibrosis
- Patients with severe thrombocytopenia (platelet count < 50,000/μL)
- Individuals who may not tolerate or respond to other JAK inhibitors like ruxolitinib or fedratinib
Because patients with very low platelets have limited treatment options, VONJO provides an important alternative that can be used safely even in those cases.
What Are the Side Effects of VONJO?
Like all medications, VONJO can cause side effects. The most common include:
- Diarrhea
- Nausea and vomiting
- Anemia (low red blood cell count)
- Low platelet count
- Swelling in the legs or ankles
More serious side effects may include bleeding, infections, and heart rhythm changes (QT prolongation). Doctors usually monitor patients closely with blood tests and heart checks during treatment.
Why It’s Not Called “Chemotherapy”
Even though myelofibrosis is a type of cancer, not every cancer treatment is chemotherapy.
The term “chemotherapy” traditionally refers to older drugs that destroy cells directly. Over the last two decades, modern cancer treatments have evolved to include targeted therapies, immunotherapies, and biologic drugs.
VONJO belongs to this newer generation of precision medicine — it doesn’t attack all dividing cells, but instead blocks the specific proteins that fuel the disease.
Final Thoughts
So, is VONJO chemotherapy?
No — VONJO is a targeted kinase inhibitor, not a traditional chemotherapy drug. It works by blocking abnormal cell signaling pathways in myelofibrosis rather than killing cells indiscriminately.
For patients with very low platelet counts who have limited options, VONJO represents a major step forward in treatment. While it is not without side effects, it offers a more tailored and often better-tolerated approach than older cancer drugs.
As always, anyone considering VONJO should talk with their healthcare provider about whether it’s the right treatment for their specific situation.