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Elitek^® is indicated for the initial management of plasma uric acid levels in pediatric and adult patients with leukemia, lymphoma, and solid tumor malignancies who are receiving anti-cancer therapy expected to result in tumor lysis and subsequent elevation of plasma uric acid. ELITEK is indicated only for a single course of treatment.

Tumor Lysis Syndrome (TLS)

Tumor lysis syndrome, also known as TLS, is a potentially fatal metabolic complication resulting from the rapid destruction of malignant cells by cancer treatment and the release of intracellular contents into extracellular space. Signs of tumor lysis syndrome may include²²:

• Hyperuricemia²² - the single most common finding in TLS²⁷
  • Hyperuricemia (abnormal elevation of serum uric acid levels) is the single most common abnormality seen in patients with TLS who develop severe metabolic abnormalities.
  • Destroyed tumor cells release their intracellular contents, inducing electrolytes, nucleic acids, proteins, and their metabolites into the circulation at a more rapid rate than the kidneys are able to remove them, leading to metabolic abnormalities.^4,5,8,22,28 The purines released undergo accelerated catabolism, resulting in increased uric acid,²⁹ which is soluble at physiologic pH (7.4). At acidic pH, uric acid crystals can form and deposit in the kidneys, joints, and other soft tissues. When uric acid crystals form in the renal tubules and collecting ducts, where the normal urine pH is around 5.0, obstruction, inflammation, and/or damage to the kidney tissues may occur.³⁰ When uric acid crystals deposit in the joints, in the context of TLS they can cause joint pain and inflammation.³⁰
• Hyperkalemia - which can result in life-threatening arrhythmias and cardiac arrest^7,22,28
• Hyperphosphatemia - along with hyperuricemia, one of the 2 characteristic signs of TLS. The presence of hyperphosphatemia heralds the potential for acute renal failure²²
• Hypocalcemia - a secondary sign of TLS associated with severe muscle cramping, tetany, and cardiac
  arrhythmias²²

Tumor lysis syndrome may be classified as Laboratory TLS (LTLS) or Clinical TLS (CTLS).⁴

LTLS is defined as laboratory results with 2 or more abnormal readings during the 3-day period prior to or up to 7 days after chemotherapy initiation^3,4*.

CTLS is the presence of LTLS and one or more of the following criteria:^3†

• Creatinine: X > 1.5 ULN
• Cardiac arrhythmias/sudden death
• Seizure

*Assessment assumes hydration (± alkalinization) and uric-acid-lowering agent will be given.
^†Not directly or probably attributable to therapeutic agent

Incidence of Tumor Lysis Syndrome^3,6,7

• Overall incidence of Tumor Lysis Syndrome is not know but has been reported to be as high as 40% in patient with high-grade non-Hodgkin lymphomas
• Tumor Lysis Syndrome is seen primarily in acute lymphoblastic leukemias and high-grade (stage III and IV) non-Hodgkin lymphomas
• Tumor Lysis Syndrome has also been observed in other malignancies including solid tumors with high proliferative rates and sensitivity to chemotherapy

Some agents used to treat leukemia or lymphoma have been associated with the development of hyperuricemia and/or Tumor Lysis Syndrome^9-21†

^†This is not a comprehensive list of agents.

Anaphylaxis: ELITEK can cause severe hypersensitivity reactions including anaphylaxis. Immediately and permanently discontinue ELITEK in patients who experience a serious hypersensitivity reaction.

Hemolysis: Do not administer ELITEK to patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Immediately and permanently discontinue ELITEK in patients developing hemolysis. Screen patients at higher risk for G6PD deficiency (e.g., patients of African or Mediterranean ancestry) prior to starting ELITEK.

Methemoglobinemia: ELITEK can result in methemoglobinemia in some patients. Immediately and permanently discontinue ELITEK in patients developing methemoglobinemia.

Interference with Uric Acid Measurements: ELITEK enzymatically degrades uric acid in blood samples left at room temperature. Collect blood samples in pre-chilled tubes containing heparin and immediately immerse and maintain sample in an ice water bath. Assay plasma samples within 4 hours of collection.