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CTGTAC March 4, 2005, Topic II Update: Retrovirus Vector-Mediated Insertional Tumorigenesis Carolyn A. Wilson, Ph.D. PowerPoint Presentation
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CTGTAC March 4, 2005, Topic II Update: Retrovirus Vector-Mediated Insertional Tumorigenesis Carolyn A. Wilson, Ph.D. DCGT/OCTGT. Update. Review, Retroviral Insertional Mutagenesis Review and Brief Update: X-SCID Gene Therapy Clinical Trial in France FDA Responses (then and now)

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slide1

CTGTAC March 4, 2005, Topic II Update: Retrovirus Vector-Mediated Insertional TumorigenesisCarolyn A. Wilson, Ph.D.DCGT/OCTGT

update
Update
  • Review, Retroviral Insertional Mutagenesis
  • Review and Brief Update: X-SCID Gene Therapy Clinical Trial in France
    • FDA Responses (then and now)
  • BRMAC, February, 2003
    • Recommendations and Actions
  • Detailed Update: X-SCID Gene Therapy Clinical Trial in France
  • Today’s Presentations and Questions
gammaretroviral mediated endogenous gene activation

Psi (Internal Promotor) Transgene

LTR

LTR

LTR

LTR

LTR

U3 R U5

U3

Read-through

Transcription

Dysregulated

Gene Expression

Distal Gene

Activation

Tumorigenesis

Gammaretroviral-Mediated Endogenous Gene Activation

Gene Disruption

events leading to brmac 2003
Events Leading to BRMAC, 2003

11 children with X-linked SCID treated in France with autologous CD34+ cells modified ex vivo by retroviral vector encoding gamma-c (c) cDNA.

  • 10/11, Clinical and laboratory evidence of engraftment and benefit
  • 2/10 children with engraftment developed leukemia

Cavazzana-Calvo, M., et al. 2000. Science 288:669-72.

Hacein-Bey-Abina, et al. 2002. New England Journal of Medicine 346:1185-1193.

Hacein-Bey-Abina, S., et al. 2003. N Engl J Med 348:255-6; Science 302:415.

slide5

LMO-2 Associated Clonal T-Cell Proliferation in Two Patients After Gene Therapy for SCID-X1Hacein-Bey-Abina, S., et al, 2003, Science 302:415

Retroviral Vector:

1) Integrated into LMO-2

2) Resulted in Transcriptional

Activation of LMO-2 locus

slide6

January 13, 2003 Letter to Retroviral Vector Sponsors

All sponsors were asked to provide risk/benefit analysis.

CBER evaluated each response.

new developments in x scid gene therapy clinical trial in france
New developments in X-SCID Gene Therapy Clinical Trial in France
  • Resumed treating patients, May 2004 with following changes (1 patient treated to date):
    • Maximum cell dose of 10 x 106c(+) CD34+/kg
    • Absence of family history of childhood cancer
    • Absence of cytogenetic abnormality
    • Presence of at least one infectious episode (i.e., pneumopathy, herpes infection, BCG infection, etc)
    • >6 months of age
  • P4: Relapse leukemia, died October, 2004
  • P5, Status: Complete remission, after completion of chemotherapy
  • P10: presented with T cell lymphoproliferation
fda response
FDA Response
  • Three INDs placed on Clinical Hold
    • X-SCID (2); ADA-SCID (1)
    • Revise Informed Consent
    • Notify IRB
  • All sponsors that use retroviral vector:
    • Informed of new events
  • Notified IRBs
recommendations actions

RecommendationsActions

BRMAC Meeting February, 2003

recommendations for x scid il 7 and jak 3 deficiencies
Recommendations for X-SCID, IL-7 and JAK-3 deficiencies
  • Unanimous Vote in Favor:
    • Only allow use of gene therapy in children with these conditions when there are no alternative therapies available
protocol changes for x scid us inds consistent with february 2003 brmac
Protocol Changes for X-SCID US INDs, Consistent with February 2003, BRMAC

Shown with permission from Drs. Malech and Weinberg

ada scid spectrum of viewpoints
ADA-SCID: Spectrum of Viewpoints
  • No fundamental biological difference in ADA-SCID to render outcome different than X-SCID
  • Transgene (gamma-c) not having effect
  • Cell dose lower in ADA-SCID
  • X-SCID transgene product, gamma-c, has potential to be oncogenic via constitutive activation
  • ADA-SCID transgene product simply metabolic
    • “apples and oranges”, more potential for gamma-c to be “second hit”
recommendations for ada scid no consensus
Recommendations for ADA-SCID – No consensus
  • Remove Clinical Hold
  • Use Gene Therapy only in children who fail PEG-ADA or fail BMT
    • Only for those with no alternative therapy
  • Children on PEG-ADA have disadvantage for GT, lose in vivo selection
    • Remove PEG-ADA to provide selective advantage
protocol changes for ada scid us ind consistent with february 2003 brmac
Protocol Changes for ADA-SCID US IND, Consistent with February 2003, BRMAC

Shown with permission from Dr. Kohn

recommendations all other protocols using ex vivo retroviral vector transduction of hsc
Recommendations: All other Protocols Using Ex vivo Retroviral Vector Transduction of HSC
  • Significant risk with any HSC therapy when adequate numbers of transduced cells are infused.
    • Important consideration in risk/benefit analysis
    • Ask sponsors to analyze probability for their trial
  • Risk not the same with other trials as with X-SCID
  • Suitable when no alternative effective therapy; failure of standard therapy
all other retroviral vectors transducing hsc consensus vote
All other Retroviral Vectors: Transducing HSCConsensus, Vote
  • Reevaluate trials on hold
    • Risk/benefit of GT vs. existing alternative therapies
    • Case-by-case
    • Appropriate informed consent documents
  • 18 yes
  • 1 no
    • Encouraged FDA to request an analysis from sponsors of the probability of a similar adverse event occurring in their individual trial.
fda implementation
FDA Implementation
  • Evaluation of each sponsor’s responses to January, 2003 letter, all indications
    • Informed consent revisions
    • Threshold for clonality analysis
    • Risk/benefit analysis
slide18

3 SCID (new hold)

6 no response

1 continue hold

Administrative and IND Status of 28 INDs

Placed on Hold, January, 2003

Number of INDs

other brmac recommendations vector safety
Other BRMAC Recommendations: VECTOR SAFETY
  • Advise investigators to develop vectors with improved safety.
  • Important issues identified
    • Suicide vectors
    • Insulator elements
    • Cell dose
    • Number of integration sites
fda actions vector safety
FDA Actions: VECTOR SAFETY
  • National Toxicology Program, Collaborative Study: FDA, NIH, Chris Baum, David Emery
  • Systematic approach to study effect of various parameters on risk of vector-mediated tumorigenesis:
    • Delete U3 from LTR (SIN)
    • Insert Insulator element in LTR
    • Modulate MOI used for vector transduction
    • Include both gammaretrovirus and lentivirus vectors
    • Mouse model established by Chris Baum
    • Analyze in study of sufficient size to give 90% CI in negative result
other related fda action
Other Related FDA Action
  • Workshop on Long-term Follow-up of Participants in Human Gene Transfer Research
    • June, 2004
    • Cosponsors: FDA, ASGT, BIO, PhRMA
    • Workshop Summary, www.asgt.org
other brmac recommendations
Other BRMAC Recommendations
  • FDA shouldn’t extrapolate an AE from one trial to others with same vector, target cell.
    • FDA did not place non-SCID INDs on hold after news of third child with leukemia in French X-SCID trial
  • Develop committee to determine number of integrants that would provide reduced risk
    • FDA committee to develop statistical approach and risk assessment
      • Carolyn Wilson and Dan Takefman, DCGT
      • Steve Anderson, Associate Director for Risk Assessment, Office of Biostatistics and Epidemiology
computer model assumptions estimation of number of vector integrations in lmo 2 2 loci
Computer Model Assumptions:Estimation of Number of Vector Integrations in LMO-2 ( 2 loci)

*Based on Wu, et al, 2003, Science 300:1749

results of simulation modeling
Results of Simulation Modeling

Number Vector Integrations in LMO-2 per 106 cells

Probability that in a treatment of 106 cells, one or more cells with

vector integration in LMO-2 engrafts

update p10
Update P10*
  • Treated at 8 months of age
    • 11 x 106 CD34+c(+) cells/kg
  • No clonal expansion seen at previous time point tested (2 months earlier)
  • Approximately 33 months post-transplant, presented with T cell lymphoproliferation
    • CD4 and CD8 positive
    • Gamma-c positive
    • Vector clonality and integration site under investigation
      • No LMO-2 integrants were detected in earlier time points; No high expression of LMO-2 protein
  • Complete remission with first line treatment, steroids

* Data By Permission, Jean-Hughes Trouvin, AFSSAPS, and Alain Fischer

comparison of patients with leukemias
Comparison of Patients with Leukemias

*Hacein-Bey-Abina, S., et al, 2003, Science 302:415

# Data By Permission, Jean-Hughes Trouvin, Afssaps, and Alain Fischer

status of other patients
Status of Other Patients

*BCG vaccination, slenomegaly; c+ cells in spleen

# Data By Permission, Jean-Hughes Trouvin, Afssaps, and Alain Fischer

regulatory status of x scid clinical trial in france
Regulatory Status of X-SCID Clinical Trial in France
  • On clinical hold, request of investigators

“…a risk of insertional mutagenesis is clearly identified today with the combination type of vector/nature of the transgene. This risk warrants the necessity of reconsideration on the protocol and method used for the SCID-X1 gene transfer….the use of safer designed vectors is to be envisaged in an attempt to reducing the insertional mutagenesis risk.”

-AFSSAPS

summary results from immune reconstitution of 132 scid patients
Summary Results from Immune Reconstitution of 132 SCID Patients

Buckley, RH, 2004, Annu. Rev. Immunol. 22:625

  • 117 Haploidentical; 15 HLA-identical
  • 102 survivors (62 on IVIG)
    • 96 >1 year
    • 68 >5 years
    • 37 >10 years
  • 30 deaths
    • 24 from viral infections
    • 2 from Candida sepsis
    • 1 each, mitochondrial defect, nephrotic syndrome (subsequent to chemotherapy for mis-diagnosed malignancy); pulmonary hypertension

No hematologic malignancies

role of c transgene product
Role of c Transgene Product?

AGAINST:

  • Hacein-Bey-Abina, S., et al, 2003
    • No over-expression of c in leukemic cells of P4, P5
    • No sequence changes in c transgene and entire retroviral vector in leukemic cells of P4, P5
    • No constitutive activation of JAK-3
  • No observed hematologic malignancies in other gene therapy clinical trials in X-SCID

FOR:

  • Dave, U., et al, 2004, Science 303:333
    • Identification of leukemia with insertion in both c and LMO-2
other gene therapy clinical trials in x scid
Other Gene Therapy Clinical Trials in X-SCID
  • Gaspar, et al, 2004, The Lancet 364:2181
  • Weinberg (by permission), no children treated
  • Malech (by permission), 2 children treated
unique characteristics of french x scid gene therapy clinical trial
Unique Characteristics of French X-SCID Gene Therapy Clinical Trial
  • Media Additives During Ex vivo culture and transduction:
    • Fetal calf serum
    • Higher concentration IL-3
    • PEG-MGDF vs. TPO
  • Transduction Conditions
    • Shortest prestimulation period
    • Use of amphotropic MLV envelope on retroviral vector pseudotype
  • Longest time to follow-up (5 years)

Significance??

topic ii speakers
Topic II: Speakers

Relevant Data from Animal Models:

  • Dr. Cynthia Dunbar
  • Dr. Utpal Dave
  • Dr. Christopher Baum

Update from Human Experience, ADA-SCID

  • Dr. Donald Kohn
question 1
Question 1

What incidence of leukemia in clinical trials using retroviral vector-mediated gene therapy for treatment of X-SCID meet the following?

“Human subjects are or would be exposed to an unreasonable and significant risk of illness or injury.”

question 2
Question 2

How to reduce the risk to subjects?

Dose

Vector Design

question 3
Question 3

Risk/benefit considerations:

  • InADA-SCID relative to X-SCID.
  • In other clinical indications.
question 4
Question 4

Limit on vector copy number per cell for cells transduced ex vivo with lentivirus vector?