01:119:150 Lecture Notes - Lecture 9: Investigational New Drug, Crispr, T Cell
27 Apr 2019
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Lecture IX: Gene Therapy
Gene Therapy
●Gene therapy - any procedure intended to treat or alleviate disease by genetically modifying the
cells of a patient
○What kind of cell?
○Is it heritable?
●Two general types
○Somatic cell or non-heritable gene therapy
■Found throughout the body
■Not reproductive cells
■Treat disease symptoms
■Not a cure in a heritable sense
○Germ-line or heritable gene therapy
■Cells that are being treated are either gamete cells or cells so early in life that they
impact every cell in the body - cell of the zygote or very early embryo
Somatic Cell Gene Therapy
●In vivo gene therapy
○Genetic material is transferred directly into cells within a patient
●Ex vivo gene therapy
○Cells are removed from the patient
○Genetic material inserted into them
○Then transplant the modified cells back into the patient
Human Gene Therapy Trials
●FDA (Center for Biologics Evaluation and Research)
○Investigational New Drug
○3-phase clinical trial process
●Must receive approval at both the local (institution) and national (FDA and NIH) level
○Gene must be cloned and well characterized
○Effective delivery method
○*Disease must not be treatable by other methods
○Preliminary experiences using animal models and human cells must be done
*2 gene therapy products are currently available
●Kymriah - used to treat acute lymphoblastic leukemia
○Very rare disease
○Cancer of the bone marrow
○White blood cells grow abnormally
○Cell-based gene therapy - remove the cells and sent to Morristown, NJ where they add a gene
into the cells
■Directs immune cells to kill cancer cells
○Threatening side effects
○$475,000 - one-time infusion of the immune cells
Severe Combined Immunodeficiency (SCID)
●SCID - patient has neither cell-mediated immune response nor is able to make antibodies
○B cells, T cells
●25% of SCID cases are due to an autosomal recessive mutation in the ADA gene
●First therapeutic use of gene therapy in humans occurred in 1990 as a treatment for SCID
*T cells - white blood cells
●Took blood sample
●Carrier molecule - vector
○Viral vector
Protocol
●Clone working ADA gene into a retroviral vector (mouse leukemia virus)
●Transfect the ADA vector into cultured T lymphocytes from the patient
●Identify the ADA + T cells and expand them in culture
●Reimplant cells in the patient
●Results - working immune system, but died after 6 months - only as long as the T cells lived
●Short-term treatment
●Aiuti et al. (2009)
○Used bone marrow because they are constantly regrowing themselves
○Permanent solution
SCID-X1
●SCID-X1 - X-linked recessive form of SCID involving the gene encoding the gamma c cytokine
receptor
●Cavazzanna-Calva et. al (2000)
○Removed bone marrow cells from 2 patients
○Transduced using retroviral vector with working copy of yc gene
○Put cells expressing yc gene back in patients
○10 months later both boys still had immune function
●Only seen in boys
●Hacein-bey-Abina et al. (April 19, 2002)
○Follow-up of early study
○5 boys (age 1 month-11 months) with X-linked SCID were treated with ex vivo gene
therapy
○Immune system continued to look nearly normal after up to 30 months of follow-up
●Oct. 2002 Fischer and Cavazzana-Calvo reported that one of the boys they treated developed “a
blood disorder resembling leukemia”
●Jan. 2003 a 2nd case reported
●Fall 2004 one child died
●Jan. 2005 3rd case reported (and then a 4th)
●Mar. 2005 US advisory panel decided that when 2 X-SCID trials in US resume they should only treat
children for whom bone marrow transplant failed
●Hacin-Bey-Abina et al. (Oct 2003): vector inserted into or near an oncogene (LMO-2) implicated in
childhood leukeumia
●Too much mRNA → too much protein → too much growth → cancer
Ornithine Transcarbamylase (OTC) Deficiency
●X-linked recessive, affected individuals cannot process nitrogen properly leading to an
accumulation of ammonia in the blood
Document Summary
Gene therapy - any procedure intended to treat or alleviate disease by genetically modifying the cells of a patient. Not a cure in a heritable sense. Cells that are being treated are either gamete cells or cells so early in life that they impact every cell in the body - cell of the zygote or very early embryo. Genetic material is transferred directly into cells within a patient. Then transplant the modified cells back into the patient. Fda (center for biologics evaluation and research) Must receive approval at both the local (institution) and national (fda and nih) level. Gene must be cloned and well characterized. *disease must not be treatable by other methods. Preliminary experiences using animal models and human cells must be done. Kymriah - used to treat acute lymphoblastic leukemia. Cell-based gene therapy - remove the cells and sent to morristown, nj where they add a gene into the cells. Directs immune cells to kill cancer cells.
