Considerations for Working with In Vivo Gene Therapies

A collection of common questions and answers around key considerations for working with in vivo gene therapies including storage, preparation, administration, waste disposal, spills, and exposure to gene therapies.

GTNSteering-jenkins

Chris Jenkins

PRINCIPAL PARTNER AND CHIEF GENE THERAPY BIOSAFETY OFFICER AT CLINICAL BIOSAFETY SERVICES

Dr. Chris Jenkins is the Principal Partner and Chief Gene Therapy Biosafety Officer at Clinical Biosafety Services, a regulatory firm specializing in administering institutional biosafety committees for biosafety risk assessment review of gene transfer trials at academic medical centers, hospital systems, and clinics. He has worked for over 10 years in the fields of human protection, gene therapy, and biosafety compliance in academic, private research, and clinical settings.

This module provides answers to questions on working with gene therapies. Additional insights on each question are provided by Dr. Chris Jenkins.

General

Should there be a formal training process developed for staff who are preparing, handling, and dispensing gene therapies?

It is recommended that gene therapies are treated as biohazards 1,2 The U.S. Pharmacopeia (USP) General Chapter <800> provides standards for the safe handling of hazardous drugs to minimize the risk of exposure to healthcare personnel, patients, and the environment 3. It states that all personnel handling hazardous drugs must be appropriately trained before handling the agent 4 It is recommended that training is specific to each discipline (e.g. pharmacists and nurses) and that it covers topics such as the molecular biological principles behind gene therapy, decontamination, and local requirements and regulations 1,5 Of note, the National Institute for Occupational Safety and Health (NIOSH) is a research agency focused on the study of worker safety and health 6. NIOSH maintains a hazardous drugs list, but does not formally classify current U.S. Food and Drug Administration (FDA)- licensed gene therapy products, as they fall outside the scope of the hazardous drugs list 1,7

What facility designs and equipment should hospital pharmacies start incorporating to handle new gene therapies in the pipeline?

It is recommended that each institution develops its own
procedures and evaluates gene therapy products individually1. The risk group and biosafety level of each viral vector should be taken into consideration, along with the potential risk associated with the transgene 1

Additional Insights from Chris Jenkins

Many centers we have worked with require biosafety cabinets, which protect the individuals, the environment, as well as the biological product. Many pharmacies have moved toward utilizing Class II Type B2 cabinets with all air filtered through high-efficiency particulate air (HEPA) filters, which allows for both biological and chemical reagents such as chemotherapies. Pharmacies have been getting ready to update their IV rooms from USP 797 to USP 800*. Clean benches should not be used as they blow clean air at the product but do not protect an individual at the bench.

Storage

How should gene therapies be stored?

European Association of Hospital Pharmacists Guidance on the Handling of Gene Medicines (2007) recommends that gene therapy products should be stored in a suitable cabinet at room temperature or in a fridge or freezer, as indicated by the product label5 Where –20°C or –70°C storage is required, gene medicines should be stored in a secure freezer that is temperature monitored and alarmed. Each gene medicine should be stored on a separate shelf within the secure freezer5 Gene therapy storage areas should be labeled appropriately, warning employees of the risk group and possible hazard 2,12

Additional Insights from Chris Jenkins

Gene therapy products should be handled under aseptic conditions during storage, handling, preparation, and dispensing. Personnel should wear appropriate personal protective equipment (lab coats, gloves, etc.). Gene therapy products should be contained within a designated isolated storage area that is labeled appropriately (i.e. with a biohazard symbol) to alert employees to the risk group and possible hazard. This guidance is based on aggregated storage guidance provided in the package inserts of U.S. Food and Drug Administration-approved gene therapies.

Preparations

What biosafety level is associated with AAV-based gene therapies?

National Institutes of Health (NIH) Guidelines for Research Involving Recombinant or Synthetic Nucleic Acid Molecules (2019) classify adeno-associated viruses (AAVs) (all serotypes) and recombinant or synthetic AAV constructs as Risk Group 1, which comprises agents “that are not associated with disease in healthy adult humans” 13 – This includes AAV constructs in which the transgene does not encode either a potentially tumorigenic gene product or a toxin molecule and is produced in the absence of a helper virus – If the transgene is toxic or oncogenic, the risk group of the transgene should be considered 1 Risk Group 1 microorganisms are considered to present “no or low individual and community risk” and are unlikely to cause human or animal disease 14,15

Additional Insights from Chris Jenkins

AAV vectors have a well-characterized safety profile from preclinical and clinical studies. The seroprevalence in the human population increases as we age 16,17 ; however, AAVs have not been associated with human illness, and are considered to be Risk Group 1.

Where should AAV-based gene therapies be prepared?

Centers for Disease Control and Prevention (CDC) guidelines do not require the use of a biosafety cabinet (BSC) for working with Risk Group 1 microorganisms that can be handled at Biosafety Level 1 14 However, it is recommended that gene therapies should be prepared using a Class II BSC to ensure product sterility and personnel safety 1 – Appropriate biosafety devices for gene therapy preparation include pharmaceutical-grade isolators or Class II Type B laminar flow BSCs that comply with US CDC criteria and European standards (NSF49, EN 12469:2000) 2,5,18,

Additional Insights from Chris Jenkins

At the time of publication of this training material, in North America, there is currently no NIH, U.S. Food and Drug Administration (FDA), or CDC-specific guidance on handling procedures for gene therapy regarding the minimization of potential exposure risk for healthcare personnel.

What safety precautions should be taken during the preparation of AAV-based gene therapies?

Safety precautions for the preparation of AAV-based gene therapies should be similar to those for the preparation of cytotoxic agents: All equipment should be brought to the preparation area, and the preparation area and equipment should be disinfected with 70% alcohol5,9 Where there are multiple BSCs in the laboratory, it is recommended that only one is used at a time in order to prevent cross-contamination 5 Personnel should wear appropriate protective clothing (gloves, lab coats, eye protection) and should handle gene therapies using a double-glove technique 2,5 Standard microbiological practices should be adopted for preparation of the material 12 – Spill kit should include: product information leaflet, disposable gowns/arm covers, gloves, masks, aprons, goggles, disposable shoe covers, disinfectant sachets, absorbent paper towels, disposable forceps, biohazard incineration bags, emergency contact number, and a copy of the spillage procedure 5

Additional Insights from Chris Jenkins

At the time of publication of this training material, in North America, there is currently no NIH, FDA, or CDC-specific guidance on handling procedures for gene therapy regarding the minimization of potential exposure risk for healthcare personnel.

What is the difference between a Class II Type A2 and a Class II Type B2 BSC?

Class II Type A2 BSCs pump high-efficiency particulate air (HEPA)-filtered air into the interior working area, creating a safe space for the user in front of the cabinet and an uncontaminated space inside to protect the materials they are working with. However, this type of cabinet will only exhaust contaminated air (and can only be used for small quantities of volatile chemicals or radionuclides) if it is linked to a functional canopy connection14,19

In contrast, Class II Type B2 BSCs pump HEPA-filtered air inside the cabinet and also exhausts contaminated air outside the laboratory via a HEPA filter

(or another air-cleaning device, depending on the type of work being performed), further protecting the user and the materials they are working with. This type of cabinet exhausts as much as 1200 cubic feet/minute of conditioned room air making it expensive to operate14,19

Additional Insights from Chris Jenkins

Ideally, a Class II Type B2 BSC that is compliant with NSF49 standards* should be used for the preparation of gene therapies, and we are seeing a lot of pharmacies move toward using this type of BSC. In Class II Type B2 BSCs, all air is filtered through a HEPA filter and is completely exhausted out of the building. This allows the cabinet to switch between being used for biologics and then, after decontamination, chemotherapy.

Should a BSC have an exhaust to the outside?

Yes, the BSC used for preparation of gene medicines should have an exhaust to the outside, rather than recirculating air back into the room, in order to protect the user and the gene medicine that they are working with from contamination1,5

All air entering a Class II Type B2 BSC is filtered through a HEPA filter (and sometimes also a carbon filter) to ensure environmental protection before being completely exhausted outside the building14

Additional Insights from Chris Jenkins

There has been a lot of discussion recently about having dedicated air flow BSCs in pharmacies that exhaust air out of the buildings. Ideally, a Class II Type B2 BSC that is compliant with NSF49 standards* should be used for the preparation of gene therapies.

How should a BSC be disinfected/decontaminated prior to and after preparation?

PRIOR TO PREPARATION OF THE GENE THERAPY:
The BSC should be switched on 15 minutes before use to ensure correct air flow, and the preparation area should be disinfected with 70% alcohol5
Use of a log book can ensure that appropriate sanitization is achieved5

AFTER PREPARATION OF THE GENE THERAPY:
The BSC should be left running for a sufficient time post-use (15–60 minutes) to allow the eradication of any aerosols, and the device should then be decontaminated2,5

Disposable equipment and materials used for preparation and administration should be handled as biohazardous waste; non-disposable items must be disinfected or autoclaved5

The biosafety cabinet should be decontaminated monthly to ensure cleanliness2

Additional Insights from Chris Jenkins
Before and after preparation of the agent, the BSC should be decontaminated with an Environmental Protection Agency-listed disinfectant that is appropriate for the agent (e.g. 10% bleach with the appropriate contact time). Many personnel also wear two pairs of gloves where they take off the first pair inside the cabinet and remove the second pair after they exit the facility.

Integrating biologics into the workflow of standard pharmacies that are operating 24 hours per day can be a challenge in terms of disinfecting and decontaminating the BSC, preparing it for an AAV product, preparing the product, and then decontaminating the cabinet ready for chemotherapy agents.

Is a closed-system transfer device recommended for preparation of gene therapies?

The National Institute for Occupational Safety and Health (NIOSH) recommends the use of closed-system transfer devices (CSTDs) when transferring hazardous drugs from primary packaging to dosing equipment, as they limit the potential for generating aerosols and exposing staff to sharps20,21

NIOSH has not yet formally classified gene therapies as hazardous drugs, as they fall outside the scope of the hazardous drugs list7

It is recommended that institutions assess gene therapies individually in order to adopt their own procedures1

Additional Insights from Chris JenkinsSince a CSTD is a drug-transfer device that mechanically prohibits the transfer of environmental contaminants into the system and the escape of the hazardous drug or vapor concentrations outside the system, this reduces exposure to individuals preparing the product. However, one issue is that a lot of the gene therapy vials may be too small for these devices. In addition, manufacturers and institutions may not have done enough testing on all the different plastics and materials that these CSTDs are composed of, so there may be compatibility issues. As a pharmacist, you may want to ask the manufacturer of the gene therapy regarding the use of a particular CSTD.

Do you recommend having a separate preparation space for gene therapies and chemotherapies?

It is recommended that institutions develop their own procedures and evaluate gene therapies on an individual basis, taking into account the viral vector’s risk group and biosafety level1

Additional Insights from Chris Jenkins
Ideally a Class II Type B2 BSC that is compliant with NSF49 standards* should be used for the preparation of gene therapies, and we are seeing a lot of pharmacies move toward the use of this type of BSC. In Class II Type B2 BSCs, all air is filtered through a HEPA filter that is completely exhausted out of the building. This allows the cabinet to switch between being used for biologics, and then after being decontaminated, to be used for chemotherapy.

Administration

What safety considerations and protective measures are required for nurses when administering gene therapies to patients?

It is recommended that all healthcare personnel who handle gene therapies receive training, which includes topics such as gene therapy molecular biology principles and precautions specific to the viral vector that they are handling1,2,4,12
Appropriate personal protective equipment must be worn5,22:

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

Additional Insights from Chris Jenkins
The eye protection and mask can come off once the infusion is underway, and also so as not to alarm the patient and their families.

Waste Disposal

What are the recommendations or options for the waste stream of gene therapy-contaminated materials?

Gene therapy materials are considered hazardous; contaminated materials (e.g. vials, syringes, tubings, needles, gloves, and personal protective equipment) should be disposed2,12,20

  • To be stored in appropriately labeled, puncture-resistant containers prior to disposal
  • To be bagged in the yellow chemotherapy waste container for timely incineration at a regulated medical waste facility

Additional Insights from Chris Jenkins
Waste stream is dependent on the city, state, and country of each institution. In pharmacies, biologics get autoclaved or heat pressurized, but chemotherapeutic agents get incinerated, which is a higher level of inactivation.
Therefore, biologics and chemotherapeutic compounds are sometimes just merged together in a yellow chemotherapy waste container for ease and space considerations This way, both the biologics and chemotherapy waste are compliant but incinerated at a higher level

How should adeno-associated virus (AAV)-contaminated equipment be decontaminated?

Non-disposable items used to dispense and administer gene therapies should be cleaned with a disinfectant that has proven virucidal activity, e.g. an oxidizing/sterilizing agent5 such as:

An Environmental Protection Agency (EPA)-registered disinfectant23 1000 ppm chlorine (using a 10% bleach solution)5,12 1–2% Virkon5 6% hydrogen peroxide5

Additional Insights from Chris Jenkins
Contaminated equipment can be decontaminated using an EPA- registered disinfectant, following the appropriate contact time as defined by the label of the disinfectant. Typical examples are a 1:10 bleach dilution followed by water to prevent pitting on stainless steel, or a quaternary ammonium compound. PDI Sani-Cloth® wipes are also widely used by pharmacies.

Should leftover gene therapy be inactivated prior to disposal, and if so, how?

European Association of Hospital Pharmacists guidelines indicate that disposable material, personal protective equipment, and sharps should be inactivated prior to incineration5

National Institutes of Health (NIH) and Centers for Disease Control and Prevention Biosafety in Microbiological and Biomedical Laboratories (CDC BMBL) guidelines recommend inactivating any culture fluids, stocks, and other potentially infectious Biosafety Level 2 materials before disposal13,14

Additional Insights from Chris Jenkins
Yes. Both the NIH and CDC BMBL guidelines require all potentially infectious materials to be decontaminated prior to disposal. They are typically inactivated by quaternary ammonium compound disinfectants. This can vary across treatments, so the approved prescribing information should be referred to for more information.

How should items (furniture, bedding, surfaces, etc.) in the infusion bay/treatment area be handled post- infusion?

Although there is currently a lack of formal guidance around the handling of gene therapies, in a Phase 1 gene therapy clinical trial, surfaces and furniture of treatment rooms were decontaminated on a daily basis and immediately after soiling by patient bodily fluids1,24

Non-disposable items should be cleaned with a disinfectant that has proven virucidal activity, e.g. an oxidizing/sterilizing agent such as 1000 ppm chlorine, 1–2% Virkon, or 6% hydrogen peroxide5

Laundry for inpatient/day-case patients should be treated according to the institution’s defined procedures for blood- or body fluid-soiled laundry, unless there are data to show that the patient is not shedding viruses5

In patients who exhibit vector shedding, disposable laundry is preferred5

Additional Insights from Chris Jenkins
Pillows and blankets used during administration of AAV-based gene therapy should be disinfected if obviously contaminated, but the routes of exposure for shedding are significantly higher in stool, which, for some gene therapies in infants, is the most likely route of contamination.

Spills

What is the procedure for managing a spill?

Any spills must be contained and cleaned immediately by qualified personnel with appropriate personal protective equipment4

Spill kits containing all essential materials must be readily available4

The appropriate procedure for the cleaning depends on the location of the spill – whether it is outside the biosafety cabinet (BSC) or inside the BSC (see figure)5

Additional Insights from Chris Jenkins
For any significant volume spills, lay down towels working from the outside of the spill inward, and then place on top to soak, followed by disinfection and removal – this is the preferred practice.

Occupational Exposure to Gene Therapies

Is there a risk to healthcare professionals (HCPs) regarding the development of antibodies to the vector if exposed during preparation/administration?

Theoretically, there is a risk of seroconversion by being in contact with patients receiving any gene therapy1

  • Seroconversion adversely impacts the therapeutic effects of a gene therapy, and may also limit the possibility of being treated with gene therapy in future

However, the clinical evidence is insufficient to understand whether limited exposure to a non-integrating viral vector causes seroconversion25

It is recommended that HCPs are trained regarding a potential seroconversion through handling and administration of gene therapy1

  • Training should be conducted in a product-specific manner in order to create awareness of potential hazards and risks, and how they could be minimized in routine clinical practice

Additional Insights from Chris Jenkins
Natural history studies show that adeno-associated viruses (AAVs) are prevalent in the community. Safe working practices and minimizing contact time with the product will minimize potential exposures.

Would you recommend that HCPs who come into contact with AAV-based gene therapy monitor their own anti-AAV antibody titers over time (i.e. get a baseline value then monitor)? If yes, how frequently should one measure anti-AAV antibody titers?

Theoretically, there is a risk of seroconversion by being in contact with patients receiving any gene therapy1

  • Seroconversion adversely impacts the therapeutic effects of a gene therapy, and may also limit the possibility of being treated with gene therapy in future
    However, the clinical evidence is insufficient to understand whether limited exposure to a non-integrating viral vector causes seroconversion25
    Natural exposure to AAV is also widespread in the general population, as demonstrated by the relatively high prevalence of neutralizing anti-AAV antibodies to various serotypes in healthy adults26

Additional Insights from Chris Jenkins
No, it is not recommended that HCPs monitor their anti-AAV antibody titer following contact. The available research suggests that people are exposed to AAV in their environment (not just in clinical settings) and can develop anti-AAV antibodies as a result of this exposure. The prevalence increases the older one gets (eventually rising to as high as 60% in some populations aged ≥50 years).

Should medical staff who are breastfeeding or pregnant avoid handling or administering gene therapies?

There are no available data regarding the risk of AAV-based vectors to women who are pregnant or breastfeeding1,25

In general, handling or administering gene therapy requires contained use and aseptic principles to protect HCPs, patients, and the environment

  • Handling of gene therapy products should be carefully monitored, particularly among female medical staff who are pregnant or breastfeeding

Additional Insights from Chris Jenkins
This is an institution-based decision. Some institutions feel comfortable with their working practices and procedures for their staff. Other institutions choose to make it mandatory that only male pharmacists handle gene therapies, and stipulate that female pharmacists should avoid contact. While this is not necessary and the data and literature do not suggest this to be an issue, it is the institution’s choice.

References

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