|Source||Humanized (from mouse)|
|Legal status||℞-only (US)|
|Mol. mass||151–153 kDa|
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Gemtuzumab ozogamicin (marketed by Wyeth as Mylotarg) is a drug-linked monoclonal antibody (an antibody-drug conjugate) that was used to treat acute myelogenous leukemia from 2000-2010. It was withdrawn from market in June 2010 when a clinical trial showed the drug increased patient death and added no benefit over conventional cancer therapies.
Gemtuzumab is a monoclonal antibody to CD33 linked to a cytotoxic agent from the class of calicheamicins. CD33 is expressed in most leukemic blast cells but also in normal hematopoietic cells, the intensity diminishing with maturation of stem cells. In the United States, it was approved under an accelerated-approval process by the FDA in 2000 for use in patients over the age of 60 with relapsed acute myelogenous leukemia (AML); or those who are not considered candidates for standard chemotherapy.
Within the first year after approval, the FDA required a black box warning be added to Gemtuzumab packaging. The drug was noted to increase the risk of veno-occlusive disease in the absence of bone marrow transplantation. Later the onset of VOD was shown to occur at increased frequency in Gemtuzumab patients even following bone marrow transplantation. The drug was discussed in a 2008 JAMA article, which criticized the inadequacy of postmarketing surveillance of biologic agents.
Common side effects of administration included shivering, fever, nausea and vomiting. Serious side effects included severe myelosuppression (suppressed activity of bone marrow, which is involved in formation of various blood cells [found in 98% of patients]), disorder of the respiratory system, tumor lysis syndrome, Type III hypersensitivity, venous occlusion, and death.
A randomized phase 3 comparative controlled trial (SWOG S0106) was initiated in 2004 by Wyeth in accordance with the FDA accelerated-approval process. The study was stopped prior to completion due to worrisome outcomes. Among the patients evaluated, fatal toxicity rate was significantly higher in the gemtuzumab combination therapy group vs the standard therapy group. Mortality was 5.7% with gemtuzumab and 1.4% without the agent (16/283 = 5.7% vs 4/281 = 1.4%; P = .01).
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