Tositumomab
{{Short description|Pharmaceutical drug}}
{{Drugbox
| Verifiedfields = changed
| verifiedrevid = 470611959
| type = mab
| mab_type = mab
| source = o
| target = CD20
| tradename = Bexxar
| Drugs.com = {{drugs.com|monograph|tositumomab}}
| MedlinePlus = a609013
| pregnancy_AU =
| pregnancy_US =
| legal_AU =
| legal_UK =
| legal_US =
| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
| ChemSpiderID = none
| CAS_number_Ref = {{cascite|changed|CAS}}
| CAS_number = 208921-02-2
| ATC_prefix = V10
| ATC_suffix = XA53
| ATC_supplemental = (sequential regimen with 131I form)
| DrugBank_Ref = {{drugbankcite|correct|drugbank}}
| DrugBank = DB00081
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 0343IGH41U
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = D08622
| ChEMBL_Ref = {{ebicite|changed|EBI}}
| ChEMBL = 1201604
| C=6416 | H=9874 | N=1688 | O=1987 | S=44
}}
Tositumomab is a murine monoclonal antibody which targets the CD20 antigen produced in mammalian cell.{{cite web |title=BEXXAR drug label |url=https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/125011s0126lbl.pdf |website=FDA |publisher=GlaxoSmithKline |access-date=18 January 2016 |date=August 2012}} It was combined with iodine-131 to produce a radiopharmaceutical for unsealed source radiotherapy, Iodine-131 Tositumomab (branded as Bexxar), for the treatment of non-Hodgkins lymphoma. It is classified as a IgG2a lambda antibody.{{cite web |title=Guide to Antibody structure and isotypes |url=https://www.abcam.com/protocols/antibody-structure-and-isotypes |website=Abcam |access-date=25 July 2020}}
The drug combination was developed by Corixa which was purchased by GlaxoSmithKline in 2005.{{Cite news |last=Mozee |first=Carla |date=29 April 2005 |title=Glaxo to acquire Corixa for $300 million |language=en-US |work=MarketWatch |url=https://www.marketwatch.com/story/corixa-agrees-to-glaxo-acquisition-for-300-million}} It was sold for about $25,000 for one round of treatment.{{cite journal | vauthors = Srinivasan A, Mukherji SK | title = Tositumomab and iodine I 131 tositumomab (Bexaar) | journal = AJNR. American Journal of Neuroradiology | volume = 32 | issue = 4 | pages = 637–8 | date = April 2011 | pmid = 21436340 | doi = 10.3174/ajnr.A2593 | pmc = 7965875 | doi-access = free }} Bexxar competed with Zevalin,{{cite journal |last1=Davies |first1=A J |title=Radioimmunotherapy for B-cell lymphoma: Y90 ibritumomab tiuxetan and I131 tositumomab |journal=Oncogene |date=28 May 2007 |volume=26 |issue=25 |pages=3614–3628 |doi=10.1038/sj.onc.1210378 |pmid=17530015|doi-access=free}} until the former's discontinuation in 2014.{{Cite news |last=Timmerman |first=Luke |date=26 August 2013 |title=Why Good Drugs Sometimes Fail: The Bexxar Story |work=Xconomy |url=http://www.xconomy.com/national/2013/08/26/why-good-drugs-sometimes-fail-in-the-market-the-bexxar-story/}}
Clinical use
A personalized regimen using Bexxar was approved for the treatment of relapsed or chemotherapy/rituxan-refractory Non-Hodgkin lymphoma in 2003.{{Cite news |date=1 July 2003 |title=Corixa and Glaxo's Cancer Drug Wins F.D.A. Approval |language=en-US |work=The New York Times |url=https://www.nytimes.com/2003/07/01/business/company-news-corixa-and-glaxo-s-cancer-drug-wins-fda-approval.html |issn=0362-4331}}New York Times. July 1, 2003 [https://www.nytimes.com/2003/07/01/business/company-news-corixa-and-glaxo-s-cancer-drug-wins-fda-approval.html Company News: Corixa and Glaxo's Cancer Drug Wins FDA Approval]{{Cite web |date=2 July 2003 |title=Tositumomab - Product Approval Information - Licensing Action |url=https://www.accessdata.fda.gov/drugsatfda_docs/appletter/2003/tosicor062703L.htm |website=FDA/Center for Drug Evaluation and Research}}
The radioactive dose was adjusted for each patient in order to maximize the radiation delivered to the tumor and minimize the exposure of other organs.{{Cite web |title=Tositumomab product description |url=https://www.fda.gov/ohrms/dockets/ac/02/briefing/3916B1_02_D-FDA%20-%20Product%20Description.htm |archive-url=https://web.archive.org/web/20180127032045/https://www.fda.gov/ohrms/dockets/ac/02/briefing/3916B1_02_D-FDA%20-%20Product%20Description.htm |archive-date=27 January 2018 |access-date=25 July 2020 |website=Food and Drug Administration}}{{rp|14–15}} Bexxar combined separate administration of unlabelled and iodine-labelled (i.e. covalently bonded to 131I) tositumomab. A first dose of labelled antibody was given once, and whole-body radiation was measured with a gamma camera over seven days. Analysis of that imaging data allowed an optimal dose of labelled antibody to be calculated, which was then administered once a day, for up to seven days.{{rp|14–15}} Each time the labelled antibody was administered, it was always preceded by unlabelled (non-radioactive) antibody. Early clinical trials had shown that total body residence times of radioactivity were longer in people who first received unlabelled antibody, so that a lower dose of labelled antibody was needed to deliver the required total dose of radiation; additionally labelled antibody targeted tumors better in people pre-treated with unlabelled antibody.{{rp|21}}
Availability
=United States=
Following a first investigational new drug application in 1989 and biologics license application in 2000, Bexxar was approved by the FDA in 2003.{{cite web |title=Briefing Information Iodine I-131 Tositumomab |url=https://www.fda.gov/ohrms/dockets/ac/02/briefing/3916b1.htm |website=Food and Drug Administration |access-date=25 July 2020 |archive-url=https://web.archive.org/web/20180125201355/https://www.fda.gov/ohrms/dockets/ac/02/briefing/3916b1.htm |archive-date=25 January 2018 |date=17 December 2002}} Sale of Bexxar was discontinued and marketing approval was withdrawn in February 2014 due to a decline in usage (fewer than 75 patients in 2012). One possible explanation for the lack of demand, despite a claimed 70% response rate, was that oncologists could not sell it directly to patients but had to refer patients to third party specialist centers, however a "muddled clinical trials strategy", supply chain issues, reimbursement problems, and emergence of non-radioactive competitors has also been blamed.{{Cite web |date=23 October 2013 |title=GlaxoSmithKline LLC; Withdrawal of Approval of the Indication for Treatment of Patients With Relapsed or Refractory, Low Grade, Follicular, or Transformed CD20 Positive Non-Hodgkin's Lymphoma Who Have Not Received Prior Rituximab; BEXXAR |url=https://www.federalregister.gov/documents/2013/10/23/2013-24840/glaxosmithkline-llc-withdrawal-of-approval-of-the-indication-for-treatment-of-patients-with-relapsed |website=Federal Register}} ({{Federal Register|78|63226}})
=Europe=
The European Medicines Agency granted tositumomab and 131I-tositumomab orphan drug status, for the treatment of follicular lymphoma, to Amersham plc in 2003. This was withdrawn in October 2015 at the request of the new owner, GlaxoSmithKline.{{cite web |title=EU/3/03/137 |url=https://www.ema.europa.eu/en/medicines/human/orphan-designations/eu303137 |website=European Medicines Agency |access-date=25 July 2020 |language=en |date=17 September 2018}}{{cite web |title=EU/3/03/136 |url=https://www.ema.europa.eu/en/medicines/human/orphan-designations/eu303136 |website=European Medicines Agency |access-date=25 July 2020 |language=en |date=17 September 2018}}
References
{{Reflist}}
{{Extracellular chemotherapeutic agents}}
{{Monoclonals for tumors}}
{{Therapeutic radiopharmaceuticals}}