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'''<sup>90</sup>Yttrium-Ibritumomab''' is an [[antineoplastic agent]] indicated for [[non-Hodgkin’s lymphom]]a. <sup>90</sup>Y-Ibritumomab Tiuxetan, a [[monoclonal antibody]], is currently unavailable in generic form due to its patented brand name, '''Zevalin'''.<ref name=ref1>{{citation
 |author = Bioegn IDEC
 | title = Zevalin (Ibritumomab Tiuxetan)| journal =  Medilexicon | date =2002 Feb.   | url = http://www.medilexicon.com/drugs/zevalin.php/
}}</ref> In February of 2002, Zevalin became the first ‘[[radioimmunotherapeutic]]’ pharmaceutical product to exist under FDA approval Zevalin is specifically indicated for previously untreated follicular non-Hodgkin’s lymphoma (NHL) as well as relapsed or refractory [[B-cell]] NHL.

{| class="wikitable"
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! Ibritumomab Tiuxetan
! Metabolism
! Product Information
|-
| {{Image|IbritumomabTiuxetan.jpg|right|250px|Image Caption}}
| CD 20 Receptor
| CAS Number: 174722-31-7
|-
| IUPAC Name: Ibritumomab Tiuxetan<br />Brand Name: Zevalin<br />Generic: <sup>90</sup>Y-Ibritumomab Tiuxetan/<br /><sup>111</sup>In-Ibritumomab Tiuxetan
| row 2, cell 2
| row 2, cell 3
|}

==Mechanism of Action'''==
Zevalin is given in two stages: Ibritumomab Tiuxetan is first paired with elemental <sup>111</sup>[[Indium]], followed by co-administration with radioactive <sup>90</sup>[[Yttrium]]. Ibritumomab Tiuxetan, the monoclonal antibody, is therefore coupled with a radioactively [[cytotoxic]] agent capable of directly targeting cancer cells<ref>2</ref>. Once in the body, Ibritumomab Tiuxetan then binds with the [[CD20 receptor]] of B-cells, inducing [[apoptosis]], or cell death, thereby reducing the growth of cancerous cells<ref>2</ref>. The role of <sup>111</sup>Indium in Zevalin is to function as a tracer, determining whether the drug has been delivered to the correct tissues<ref>2</ref>. After correct distribution is confirmed, <sup>90</sup>Yttrium provides specificity for cancer cells, exposing them to radioactive [[beta emission]]<ref>1,2</ref>. <br /><br />

==Dosage and Administration==
Zevalin is a seven-day [[chemotherapy]] treatment. All treatments fall under the following FDA guidelines and scheduling<ref>3</ref>: 
===Relapsed or Refractory B-cell NHL===
'''Day 1:''' The patient receives 250mg/m<sup>2</sup> [[Rituximab]] intravenously. This is a common drug of chemotherapy. After four hours, the patient receives 5mCi <sup>111</sup>In-Ibritumomab Tiuxetan over 10 minutes<ref>3</ref>.<br />
'''Days 2-6:''' The patient receives a resting period in which medical imaging confirms or denies proper distribution, or [[biodistribution]], of the drug<ref>3</ref>.<br />
'''Day 7:''' The patient again receives 250mg/m<sup>2</sup> Rituximab intravenously. After fours hours, the patient receives radioactive <sup>90</sup>Y-Ibritumomab Tiuxetan, substituting <sup>90</sup>Yttrium for <sup>111</sup>Indium<ref>3</ref>. <br /><br />
Dosing for <sup>90</sup>Y-Ibritumomab Tiuxetan is based upon patient blood counts: [[Platelet]] levels of 100,000-149,000/m<sup>3</sup> call for 0.3 mCi/kg over ten minutes, while counts of 150,000/m<sup>3</sup> or more require 0.4 mCi/kg over ten minutes<ref>3</ref>. The maximum dose of Zevalin is 32 mCi. For previously untreated NHL, however, platelet counts must be a minimum of 150,000/m<sup>3</sup> and treatment must begin within six to twelve weeks following the final dose of the patient’s previous chemotherapy<ref>3</ref>. <sup>90</sup>Y-Ibritumomab Tiuxetan is therefore infused at 0.4mCi/kg over ten minutes<ref>3</ref>. Zevalin may also be adjusted to an eight or nine-day therapy given patient response: A physician may decide to administer <sup>90</sup>Y-Ibritumomab Tiuxetan on days seven, eight, or nine<ref>3</ref>. Varying pre-medications are concomitantly administered and FDA required.

==Medical Imaging==
[[Radioactive imaging]] of Zevalin is required to be taken within 48 to 72 hours of administering its radioactive component<ref>3</ref>. A great advantage of Zevalin therapy includes the ability to use this imaging to trace the drug throughout the [[lymphatic system]]. This is essential to determining proper biodistribution. After taking body images, or [[scintigrams]], the following equation is used to determine radioactive exposure to varying tissues:<br />

F<sub>SPECT</sub> = (A<sub>STD</sub>/A<sub>O</sub>) x (C<sub>TUM</sub>/C<sub>STD</sub>)<br />

Where A<sub>O</sub> is the <sup>111</sup>Indium activity and A<sub>STD</sub> its standard deviation, and C<sub>TUM</sub> are the tumor SPECT counts and C<sub>STD</sub> their standard deviations<ref>6</ref>. This equation determines the fractional activity of particular components of the body and lymphatic system, such as the fraction of <sup>111</sup>In-Ibritumomab in a tumor versus the total activity of <sup>111</sup>In-Ibritumomab as a whole throughout the body. Multiple studies have determined total body [[absorption]] of Zevalin to be both safe and effective<ref>6</ref>.  The effective dose of a drug indicates the drug dose required to achieve a minimum 50% response in all patients. Medical imaging is therefore important to confirm not only drug delivery to the correct tissues, but also whether or not radioactive exposure achieves toxic effects. Indications of improper distribution or unsafe exposure require alteration of the dose, or discontinuation of the therapy itself.<br /><br />

==Clinical Efficacy==
Two main studies contributed to Zevalin's FDA approval, and have ultimately provided substantial support for the use of Zevalin in NHL. In the first study, an overall 74% response occurred in which 15% of patients attained a complete response to the treatment<ref>1</ref>. In the second study, comparable outcomes were achieved: An overall 80% response occurred in which 16% of patients attained a complete response<ref>1</ref>.  Zevalin also displayed a greater [[efficacy]] than Rituximab alone, in which only a 56% response rate occurred<ref>7</ref>. Event-free survival rates ranged from 8.5 to 28 months longer with Zevalin therapy than with patients’ most recently prior chemotherapeutic treatment<ref>8</ref>. An average of 67% tumor shrinkage occurred<ref>9</ref>. Clinical trials have further supported this data with overall responses ranging from 61.5% to 86%<ref>9</ref>. In conclusion, throughout FDA approval, clinical trials, and drug phase testing, Zevalin was determined to have clinical efficacy, in which it<br /><br />
a) Provided higher overall and complete response rates than previous chemotherapy treatments, <br />
b) Induced greater tumor shrinkage in solid cancer forms, and<br />
c) Lengthened event-free survival rates following administration.

==Contraindications==
Zevalin should not be used while pregnant or breastfeeding, as it may cause damage to the unborn fetus or infant<ref>3</ref>. Zevalin should not be combined with [[anticoagulants]] (ie. [[Warfarin]], [[Aspirin]], [[Heparin]]) as they will thin the blood and may cause excessive bleeding, a serious and potentially fatal adverse event<ref>11</ref>. 80% of fatal therapies occurred within the first Rituximab infusion. Zevalin should not be given to patients with greater than 25% damaged [[lymphatic marrow]]<ref>3</ref>.

==Side Effects==
Common side effects include [[thrombocytopenia]] and [[neutropenia]], or low red blood cell and white blood cell counts, respectively<ref>3,12,13</ref>. Thrombocytopenia of all grades clinically occurs in 62-95% of patients while neutropenia of all grades occurs in 45-77% of patients<ref>12,13</ref>.  Joint pain, infection, and fatigue are also prominent. Mild side effects include dizziness, [[hypoxia]], [[anorexia]], and [[gastrointestinal]] effects (ie. nausea, vomiting, diarrhea, abdominal pain)<ref>3</ref>. Severe adverse events include extreme [[hematological toxicity]], immune system infection due to vulnerability, heart attack, uncommon [[dermatological]] effects, and overexposure to radiation<ref>3</ref>.

==Expense==

A single dose of Zevalin costs ranges $22,000 to $24,000 in a hospital setting, making it the most expensive single-dose drug on the market<ref>4</ref>. This treatment, however, comprises a full therapy (seven to nine days), whereas most chemotherapy regimens consist of multiple drugs on varying days. A typical chemotherapy regimen costs a patient on average between $20,000 and $30,000, making Zevalin a somewhat middle-of-the-road regimen in terms of chemotherapy financial expense<ref>4,5</ref>.

==References==

1. Biogen IDEC (2002 Feb.), "Zevalin (Ibritumomab Tiuxetan)", Medilexicon
2. Elsevier. Clinical Pharmacology. Zevalin: Monograph. 2010 [cited Sept. 29]. Available from: http://http://clinicalpharmacology.com/Forms/drugoptions.aspx?cpnum=2573&n=Zevalin. <br />
3. Micromedex. Ibritumomab Tiuxetan. [serial on the Internet]. 2010 Feb. 8 [cited 2010, Sept. 29];22. Available from: http://www.thomsonhc.com/hcs/librarian/ND_T/HCS/ND_PR/Main/CS/426746/DUPLICATIONSHIELDSYNC/421FFD/ND_PG/PRIH/ND_B/HCS/SBK/2/ND_P/Main/PFActionId/hcs.common.RetrieveDocumentCommon/DocId/2224/ContentSetId/31#secN1006A<br />
4. Timmerman, L. Biogen Radiation Drug, a Single Shot, Halts Lymphoma [serial on the Internet]. 2007 Dec. 9 [cited 2010 Oct. 25];1, Available from: http://www.bloomberg.com/apps/news?pid=newsarchive&sid=ahnHMD8ehySY<br />
6. Erwin, W, et. al. Estimation of Yttrium-90 Zevalin Tumor-Absorbed Dose in Ocular Adnexal Lymphoma Using Quantitative Indium-111 Zevalin Radionuclide Imaging. [serial on the Internet]. 2009 Sept. [cited 2010, Sept. 29];6. Available from: http://ovidsp.tx.ovid.com/. <br />
7. Pacilio, M, et. al. A Theoretical Dose-Escalation Study Based on Biological Effective Dose in Radioimmunotherapy With 90Y-Ibritumomab Tiuxetan (Zevalin). [serial on the Internet]. 2010 Jan. 13 [cited 2010, Oct. 7];13. Available from: http://www.ncbi.nlm.nih.gov/pubmed/
20069297/.<br />
8. Cicone, F, et. al. Follicular Lymphoma at Relapse After Rituximab Containing Regimens: Comparison of Time to Event Intervals Prior to and After 90Y-Ibritumomab-Tiuxetan. [serial on the Internet]. 2010 Aug. 6 [cited 2010 Sept. 29];8. Available from: http://www.wileyonlinelibrary.com. <br />
9. Wang, M, et al. Phase II Study of Yttrium-90–Ibritumomab Tiuxetan in Patients With Relapsed or Refractory Mantle Cell Lymphoma. [serial on the Internet]. 2009 Nov. 1 [cited 2010 Sept. 29];6. Available from: http://www.jco.ascopubs.org. <br />
10. Ferrucci, P, et. al. High Activity 90Y-Ibritumomab Tiuxetan (Zevalinâ) With Peripheral Blood Progenitor Cells Support in Patients With Refractory/Resistant B-cell Non-Hodgkin Lymphomas. [serial on the Internet]. 2007, Aug. 1 [cited 2010 Sept. 29];10. Available from: http://www.onlinelibrary.wiley.com. <br />
11. West, S, et. al. Cutaneous Surgeons Cannot Predict Blood-Thinner Status by Intraoperative Visual Inspectio. [serial on the Internet]. 2001 Aug. 30 [cited Oct. 7]6. Available from: http://www.ncbi.nlm.nih.gov/pubmed/12087237/.<br />
12. Borghaei, H, et. al. Safety and Efficacy of Radioimmunotherapy with Yttrium 90 Ibritumomab Tiuxetan (Zevalin). [serial on the Internet]. 2004 Jan. [cited 2010, Oct. 7];7. Available from: http://www.ncbi.nlm.nih.gov/pubmed/14762738/.<br />
13. Costantini, D, et. al. 111In-Labeled Trastuzumab (Herceptin) Modiﬁed with Nuclear Localization Sequences (NLS): An Auger Electron-Emitting Radiotherapeutic Agent for HER2/neu-Ampliﬁed Breast Cancer. [serial on the Internet]. 2007 May 15 [cited 2010, Oct. 7];12. Available from: http://jnm.snmjournals.org/cgi/content/abstract/48/8/1357/.<br />


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