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Strimvelis is the first ex-vivo stem cell gene therapy to treat patients with a very rare disease called ADA-SCID (Severe Combined Immunodeficiency due to Adenosine Deaminase deficiency). ADA-SCID is estimated to occur in approximately 15 patients per year in Europe.


The treatment is personalized for each patient; hematopoietic stem cell (HSCs) are extracted from the patient and purified so that only CD34-expressing cells remain. Those cells are cultured with cytokines and growth factors and then transduced with a gammaretrovirus containing the human adenosine deaminase gene and then reinfused into the patient. These cells take root in the person's bone marrow, replicating and creating cells that mature and create normally functioning adenosine deaminase protein, resolving the problem.[1][2][3] As of April 2016, the transduced cells had a shelf life of about six hours.[4]

Prior to extraction, the person is treated with granulocyte colony-stimulating factor in order to increase the number of stem cells and improve the harvest; after that but prior to reinfusion, the person is treated with busulfan or melphalan to kill as many of the person's existing HSCs to increase the chances of the new cells' survival.[2][3]

Side effects[edit]

The most common side effects in clinical trials were pyrexia, increased liver enzyme levels, anemia, neutropenia, hemolytic anaemia, aplastic anaemia and thrombocytopenia.[1]


The treatment was developed at San Raffaele Telethon Institute for Gene Therapy and developed by GlaxoSmithKline (GSK) through a 2010 collaboration with Fondazione Telethon and Ospedale San Raffaele. GSK, working with the biotechnology company MolMed S.p.A, developed a manufacturing process that was previously only suitable for clinical trials into one demonstrated to be robust and suitable for commercial supply.[citation needed]

In April 2016, a committee at the European Medicines Agency recommended marketing approval for its use in children with adenosine deaminase deficiency, for whom no matched HSC donor is available, on the basis of a clinical trial that produced a 100% survival rate; the median follow-up time was 7 years after the treatment was administered.[1] 75% of people who received the treatment needed no further enzyme replacement therapy.[5] Efforts had begun 14 years before. The total number of children treated was reported as 22[6] and 18.[7] Around 80% of patients have no matched donor.[8] Strimvelis was approved [9] by the European Commission on 27 May 2016.

As of 2016, the only site approved to manufacture the treatment was MolMed.[4]

In 2017 GSK announced it was looking to sell off Strimvelis,[10] and in March 2018 GSK sold Strimvelis to Orchard Therapeutics Ltd.; as of that time there had been only five sales of the product.[11]

Society and culture[edit]

The condition affects about 14 people per year in Europe and 12 in the U.S.[12]

The price for the treatment was set at €594k, 2 times the annual cost of enzyme replacement therapy injections.[13] enzyme replacement therapy for ADA requires weekly injections and costs about $4.25 million for one patient over 10 years.[8]


  1. ^ a b c EMA Strimvelis Page accessed April 13, 2016
  2. ^ a b Candotti F. Gene transfer into hematopoietic stem cells as treatment for primary immunodeficiency diseases. Int J Hematol. 2014 Apr;99(4):383-92. Review. PMID 24488786
  3. ^ a b Touzot F, et al Gene therapy for inherited immunodeficiency. Expert Opin Biol Ther. 2014 Jun;14(6):789-98. doi: 10.1517/14712598.2014.895811. Epub 2014 Mar 8. Review. PMID 24823313
  4. ^ a b Ben Adams for FierceBiotech Apr 4, 2016 Strimvelis to be the start of a whole new gene therapy platform for GSK and partners
  5. ^ Booth C et al. Treating Immunodeficiency through HSC Gene Therapy. Trends Mol Med. 2016 Apr;22(4):317-27. PMID 26993219
  6. ^ Denise Roland for the Wall Street Journal. April 1, 2016 Glaxo’s Potential Cure for “Bubble Boy Disease” One Step Closer
  7. ^ Andrew Ward for the Financial Times. April 1, 2016 GSK to allow staggered payments for EMA-approved gene therapy
  8. ^ a b Ketaki Gokhale for Bloomberg News. April 1, 2016 Glaxo's `Bubble Boy' Gene Therapy Wins EU Drug Agency Nod
  9. ^ "StrimvelisTM receives European marketing authorisation to treat very rare disease, ADA-SCID - GSK".
  10. ^ "GSK gives up on rare diseases as gene therapy gets two customers". Reuters. July 26, 2017.
  11. ^ Paton, James (March 6, 2018). "Tiny U.K. Biotech Takes On Glaxo's $730,000 Gene Therapy". Bloomberg.
  12. ^ Regalado, Antonio (May 6, 2016). "Gene Therapy's First Out-and-Out Cure Is Here". MIT Technology Review. Retrieved 2016-05-12.
  13. ^ "Does the EU price of Strimvelis create a new 'glass ceiling'? - groupH - Inspiration". Retrieved 2017-02-26.