How Clolar Works

Before doctors tested Clolar in patients, scientists first tried to determine how it works by doing in vitro (test tube) experiments in the laboratory. What the scientists learned was that Clolar works in two ways.

1. Clolar interferes with the development of new leukemia cells

Once Clolar enters the cell, it goes to work by blocking two enzymes that cells need to reproduce. Leukemia cells, like other cells, reproduce by duplicating their DNA and then dividing, forming two new cells. By blocking the enzymes ribonucleotide reductase (RnR), Clolar interferes with the production of building blocks that are needed to make new DNA. By blocking the enzyme DNA polymerase, Clolar interferes with the duplication of DNA. By blocking these enzymes, Clolar helps stop leukemia cells from dividing, and therefore limits the development of new leukemia cells.

2. Clolar encourages leukemia cell to die

Clolar also disturbs another important part of the cell, the mitochondrial membrane, causing certain substances to be released, which leads to the death of the leukemia cell.

At this time, we do not know the clinical significance of these actions.

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How Clolar is Used

Clolar is a type of medication to treat children, ages 1 to 21 with a type of leukemia called relapsed or refractory acute lymphoblastic leukemia (ALL), after at least 2 other treatment attempts have failed. Clolar can reduce the number of leukemia cells in the blood. At this time we do not know if Clolar will help a child with ALL live longer or cure him or her of the cancer.

Important Safety Information for Patients

Serious side effects

Clolar can cause serious side effects that include:

• Systemic inflammatory response syndrome (SIRS)/capillary leak syndrome (CLS). Signs include fast breathing, fast heartbeat, low blood pressure, and difficulty breathing. These signs should be reported to the physician right away, as SIRS and CLS can be life-threatening if not treated right way. If your child experiences clinically significant signs of SIRS or CLS, your physician should stop Clolar immediately and consider giving your child steroids, diuretics, and albumin. When your child has stabilized, Clolar can be continued, usually at a lower dose.
• Bone marrow suppression and infection. Clolar can stop your child’s bone marrow from making enough red blood cells, white blood cells, and platelets. Serious side effects can result from this, and include severe infection (sepsis), bleeding, and anemia.
• Effects on pregnancy and breastfeeding. Females should not become pregnant or breastfeed during treatment with Clolar because Clolar may harm the baby.

Other side effects

The most common side effects with Clolar are stomach problems (including vomiting, diarrhea, and nausea), and effects on blood cells (including low red and white blood cells count, low platelet count, fever, and infection). A fast heartbeat has been noted in some patients taking Clolar. Clolar can also affect the liver and kidneys. For these reasons, your child’s healthcare professional will do blood tests to monitor his or her blood cells, kidney function, and liver function.

Treatment with Clolar quickly reduces the number of leukemia cells in your child’s blood. For this reason, your doctor should monitor your child for signs and symptoms of tumor lysis syndrome (TLS), as well as signs and symptoms of cytokine release, which can develop into SIRS, CLS, and organ problems. Your doctor is encouraged to give continuous IV fluids throughout the five days of Clolar treatment to reduce certain side effects. Your doctor may also prescribe allopurinol to reduce the build-up of uric acid that occurs with TLS. Your doctor should stop the Clolar treatment if your child develops low blood pressure for any reason during the five days of treatment.

Please speak with your healthcare professional if you have questions about Clolar. Also, please see full prescribing information.