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Monoclonal antibody
TypeWhole antibody
SourceHumanized (from mouse)
Clinical data
Trade namesRaptiva
Routes of
ATC code
CAS Number
  • none
Chemical and physical data
Melting point66 °C (151 °F)
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Efalizumab (brand name Raptiva, Genentech, Merck Serono) is a formerly available medication designed to treat autoimmune diseases, originally marketed to treat psoriasis. As implied by the suffix -zumab, it is a recombinant humanized monoclonal antibody administered once weekly by subcutaneous injection. Efalizumab binds to the CD11a[1] subunit of lymphocyte function-associated antigen 1 and acts as an immunosuppressant by inhibiting lymphocyte activation and cell migration out of blood vessels into tissues. Efalizumab was associated with fatal brain infections and was withdrawn from the market in 2009.[2]

Known side effects include bacterial sepsis, viral meningitis, invasive fungal disease and progressive multifocal leukoencephalopathy (PML), a brain infection caused by reactivation of latent JC virus infection.[3][4] Four cases of PML were reported in plaque psoriasis patients, an incidence of approximately one in 500 treated patients.[2]

Due to the risk of PML, the European Medicines Agency (EMA) and the Food and Drug Administration (FDA) recommend suspension from the market in the European Union and the United States, respectively.[5] In April 2009, Genentech Inc. announced a phased voluntary withdrawal of Raptiva from the U.S. market.[2][6]


  1. ^ Li S, Wang H, Peng B, Zhang M, Zhang D, Hou S, et al. (March 2009). "Efalizumab binding to the LFA-1 alphaL I domain blocks ICAM-1 binding via steric hindrance". Proceedings of the National Academy of Sciences of the United States of America. 106 (11): 4349–54. Bibcode:2009PNAS..106.4349L. doi:10.1073/pnas.0810844106. PMC 2657446. PMID 19258452.
  2. ^ a b c Major EO (2010). "Progressive multifocal leukoencephalopathy in patients on immunomodulatory therapies". Annual Review of Medicine. 61 (1): 35–47. doi:10.1146/annurev.med.080708.082655. PMID 19719397.
  3. ^ "Efalizumab FDA Warning". 16 October 2008. Retrieved 7 December 2008.
  4. ^ Berger JR, Houff SA, Major EO (2009). "Monoclonal antibodies and progressive multifocal leukoencephalopathy". mAbs. 1 (6): 583–9. doi:10.4161/mabs.1.6.9884. PMC 2791316. PMID 20073129.
  5. ^ "EMEA press release regarding suspension" (PDF). Archived from the original (PDF) on 26 December 2009. Retrieved 20 February 2009.
  6. ^ "Genentech Announces Voluntary Withdrawal of Raptiva from the U.S. Market" (Press release). Genentech, Inc. 8 April 2009. Archived from the original on 28 May 2011. Retrieved 9 April 2009.