Handling Gene Therapy in Clinical Settings

In recombinant viral vectors, non-essential viral genes can be replaced by the therapeutic gene of interest and modified to be replication incompetent1

As part of the delivery vector, there is a viral capsid that can trigger various components of our immune system2,3

Because gene therapies utilize viral vectors, they are to be considered biohazardous materials and must be handled using proper procedures4,5

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Defining Risk and Biosafety of Gene Therapy and Infectious Agents

To minimize the potential risk of exposure to infectious agents, basic biological risk and containment criteria have been established for their handling1–4

  • Infectious agents are classified into risk groups
    that describe the relative hazard posed by the
    agent used for laboratory research5
  • The risk group to which an infectious agent is assigned is used to determine the appropriate biosafety level – a set of procedures and laboratory containment for the handling of the agent4,5

Risk Group 1

Agents that are not associated with disease in healthy adult humans1

Represent no or little individual and community risk2

Risk Group 1

Examples: Bacillus subtilis; AAV (all serotypes); recombinant or synthetic AAV constructs*1

Risk Group 2

Agents that are associated with human disease that is rarely serious and for which preventive or therapeutic interventions are often available1

Represent moderate individual risk but low community risk2

Risk Group 2

Examples:
Salmonella; Staphylococcus aureus; Penicillium marneffei; Toxoplasma; all human adenoviruses; hepatitis A, B, C, D, and E viruses; herpes zoster; all human papilloma viruses1

Risk Group 3

Agents that are associated with serious or lethal human disease for which preventive or therapeutic interventions may be available1

Risk Group 3

Examples: Coxiella burnetii *; Rickettsia akari; West Nile virus; yellow fever virus; SARS-CoV; monkeypox virus; transmissible spongiform encephalopathies agents; HIV types 1 and 21

Risk Group 4

Agents that are likely to cause serious or lethal human disease for which preventive or therapeutic interventions are not usually available1

High individual and community risk2

Risk Group 4

Examples:
Lassa virus; herpes B or monkey B virus; Ebola virus; undefined hemorrhagic fever agents and viruses1

Biosafety Levels

Biosafety is the application of safety precautions that reduce the risk of exposure in the laboratory to a potentially infectious microbe and limit contamination of the work environment1

There are four biosafety levels designated by the CDC that include BSL-1, BSL-2, BSL-3, and BSL-41,2

Each level has specific containment controls for laboratory practices, safety equipment, and facility construction1

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Biosafety Level 4

Criteria for inclusion1

Dangerous/exotic agents* that pose individual risk of aerosol-transmitted infections; agents that have a close antigenic relationship to a BSL-4 agent; agents that have unknown risk of transmission

Laboratory practices1

BSL-3 practices plus:

Decontamination of all material on exit from facility

Entrance through change room and shower on exit

Safety equipment1

BSL-3 equipment plus:

Class III BSCs or

Partial containment equipment with full-body, air-supplied,
positive pressure suit

Facilities1

Separate building or isolated zone

Dedicated supply and exhaust, vacuum, and decontamination systems

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Biosafety Level 3

Criteria for inclusion1

Indigenous or exotic agents that may cause serious or potentially lethal disease through the inhalation route of exposure

Laboratory practices1

BSL-2 practices plus

Controlled access to laboratory

Decontamination of all waste and laboratory clothing

Safety equipment1

BSL-2 equipment plus

PPE includes protective laboratory clothing, gloves, face, eye and respiratory protection

BSC or other physical containment devices for all open manipulation of agents

Facilities1

Self-closing, double-door access; sealed windows and penetrations

Entry through airlock or anteroom

Hand-washing sink near exit

Exhausted air not recirculated

Available autoclave

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Biosafety Level 2

Criteria for inclusion1

Agents of moderate hazard associated with human disease that can be transmitted via percutaneous injury, ingestion, or mucous membrane exposure

Laboratory practices1

BSL-1 practices plus

Limited access to laboratory

Biohazard warning signs

Safety equipment1

BSL-1 equipment plus

PPE includes laboratory coat, gloves, face and eye protection

BSC for procedures that may cause exposure to aerosol or splashes

Facilities1

Self-closing doors

Sink for hand washing

Readily available eye-wash station

Available autoclave

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Biosafety Level 1 


Criteria for inclusion1

Agents not known to consistently cause disease in healthy adults

Laboratory practices1

Standard microbiological practices

Safety equipment1

No primary barriers required

PPE includes laboratory coat and gloves

Facilities1

Doors for access control

Benches or tables able to support loads and use, and easy to clean

Sink for hand washing

Risk Groups and Biosafety Levels for 
Gene Therapy Vectors

Human gene transfer vectors are, at a minimal, categorized into Risk Group 1 and Risk Group 21

  • Most modern vectors are incapable of or restricted in their replication in vivo and thus considered to be non-pathogenic Risk Group 1 agents, which supports their use under BSL-1 procedures1,2
  • Despite this classification, many institutional biosafety committees require adherence to BSL-2 containment and procedures due to the unknown effects of accidental exposure and potential for generation of replication-competent vectors1
  • BSL-2 procedures are designed to prevent physical contact with cultures, offer staff prophylactic measures including vaccinations, and establish methods for treatingindividuals who have been exposed to the agent1

Risk Groups for Common Viral Vectors

Adeno-associated viral vector 1 1
Avipoxvirus 1 1
Modified vaccinia virus 1 1
Adenoviral vector 2 1
Herpes viral vector (HSV-1) 2 1
Lentiviral vector 3 2
Retrovirus vector 3 (MoMLV; for animals) 2 (for animals); ≤2 (for human)

Risk Identification for Gene Therapy Products

Risk identification tools may be useful in determining appropriate safe handling procedures1

  • Given the heterogeneity of gene therapy products with regards to their integrating and hazardous properties, it is recommended that each gene therapy undergo assessment of risk based on specific viral vector and transgene properties1
  • For gene therapy products that have the capability to replicate, integrate into the genome, or contain a toxic transgene, more detailed risk evaluations are recommended by an institutional committee to determine safe handling procedures1

Decision Tree for Handling of Gene Therapy Products1

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Examples of Potential Opportunities of Exposure 
in Clinical Settings

Unintended exposure to hazardous agents can occur via dermal and mucosal absorption, inhalation, injection, and ingestion1

Activity Potential opportunity of exposure
Receipt Contacting residues on drug containers, individual dosage units, or work surfaces
Compounding and other manipulations Constituting or reconstituting powdered or lyophilized agent
Expelling air or agent from syringes
Contacting residue present on PPE or other garments
Decontaminating work surfaces
Administration
Generating aerosols during administration of agent
Priming an IV administration set
Patient care activities
Handling bodily fluids or body fluid-contaminated materials
Spills Generation, management, and disposal of spills
Transport Moving agent within a healthcare setting
Waste Collection and disposal of hazardous and contaminated waste

Biosafety Procedures for Hazardous Drugs in Clinical Setting

All personnel handling hazardous drugs must be appropriately trained before handling the agent1

Storage1

Must be stored to prevent spillage or breakage

Refrigerated agents must be stored in a dedicated refrigerator

Administration1

Must be administered safely using protective medical devices and techniques

Appropriate PPE must be worn

Disposal1

Equipment (including tubing and needles) and packaging materials must be disposed appropriately, after administration

All areas and equipment should be thoroughly decontaminated, deactivated, and cleaned

Spill Control1

In the event of a spill, the spill must be contained and cleaned immediately only by qualified personnel with appropriate PPE

Spill kits containing all essential materials must be readily available

Biosafety Procedures for Gene Therapy

Each clinical laboratory using human gene transfer vectors must be properly equipped with the following1:

Personal protective equipment

  • Gloves
  • Eye protection
  • Face (surgical) masks
  • Lab coats

Laboratory facilities

  • Sink, eye-wash station, drench shower
  • Fume hood
  • Biosafety cabinets
  • Sharps disposal
  • Access to an autoclave
  • Doors marked with biohazard signs

Guidance on Handling of Gene Therapy Products

Although gene therapies may be considered biohazardous materials, they can be administered with minimal risk if proper procedures are followed1

Receipt and Storage1

  • All gene therapy shipments must be properly inspected and opened in the pharmacy preparation room wearing appropriate PPE
  • Must be stored at a suitable temperature, according to product information
  • Gene therapy storage areas should be labeled to alert employees of possible hazard

Preparation1

  • Preparer should always wear chemotherapy gloves (or two pairs of surgical gloves) and a closed front surgical-type gown with knit cuffs
  • All dose preparations must be done in a designated Class II* laminar flow biological safety cabinet

Cleaning and Disposal1

  • The biosafety cabinet must be disinfected before and after completing all gene therapy drug preparations
  • Protective clothing must always be worn
  • All disposable material should be placed in a gene therapy-specific biohazard container

Appropriate Use of Personal Protective Equipment 
for Handling Gene Therapies

Within a pharmaceutical environment, the potential routes of exposure must be considered when evaluating the necessary personal protective equipment (PPE)1

  • Potential routes of exposure include accidental skin puncture, ingestion, direct contact with the skin or mucous membrane, or inhalation from an aerosol1
  • For the handling of biological products, gowns, head covers, masks, shoe covers, and gloves are required1
  • Goggles should be considered when splashes or sprays
    are anticipated1
  • When compounding Risk Group ≥3 agents, a respirator is required1

Summary/Module Recap

  • Basic biological risk and containment criteria have been established for the handling of infectious agents to minimize the potential risk of exposure to them1–4
  • Infectious agents are classified into risk groups that determine the appropriate biosafety level in which the agent is to be handled4,5
  • Medical institutions should ensure that they have plans in place to allow for the safe handling of infectious agents with minimal chance of exposure and mechanisms of quick response if such exposure occurs4