Cell & Gene Therapy Manufacturing

01Modality overview and development process

Cell and gene therapies modify or replace cells and genetic material rather than delivering a conventional drug. The category splits along two axes that dominate every sourcing decision: autologous vs allogeneic cell therapy (a patient's own cells vs a donor-derived, banked source) and in vivo vs ex vivo gene delivery. Most programmes depend on viral vectors — AAV for in vivo gene therapy and lentivirus for ex vivo cell engineering such as CAR-T. Chain of identity and chain of custody — keeping each patient-specific product traceable end to end — is a manufacturing and IT requirement unique to this modality.

02Manufacturing workflow and key technologies

• Viral vector production — AAV by transient transfection of HEK293 (adherent or, increasingly, suspension) or stable producer cell lines; lentivirus typically by transient transfection of HEK293T. Suspension scale-up is the key capability separating clinical-only from commercial-ready vector suppliers.
• Cell processing (autologous) — apheresis coordination → activation → transduction → expansion → formulation → cryopreservation, with closed, automated systems increasingly mandatory at commercial scale.
• Plasmid DNA supply — high-quality plasmid is the upstream raw material for transfection; integrated plasmid + vector capability removes a critical supply interface.
• Analytics — vector genome titre, full/empty capsid ratio, potency, identity, and replication-competent virus (RCL/RCA) testing. Potency assay development is a recurring critical-path item.
• Fill-finish & cold chain — cryopreservation, controlled-rate freezing, and validated −150 °C to −196 °C logistics.

03Development vs. commercial manufacturing requirements

The autologous model is fundamentally scale-out, not scale-up: each batch is a single patient, so commercial readiness is about parallelising many small, identical, closed processes with flawless chain of identity — not building bigger reactors. The allogeneic and in-vivo gene-therapy models are true scale-up problems: a master cell bank or a high-yield suspension AAV process feeds many doses, and the economics reward yield and full-capsid ratio. Matching the CDMO's operating model to your therapy's model is the first filter — a great autologous CDMO may be the wrong partner for a suspension-AAV programme.

04Critical supplier selection criteria

• Vector platform & scale — AAV and/or lentivirus, adherent vs suspension, and demonstrated yield at the scale you need.
• Plasmid integration — in-house or tightly partnered plasmid supply to control a key raw material.
• Full/empty capsid capability — analytical and purification capability to control empty-capsid burden (a major efficacy and safety lever for AAV).
• Potency assay support — willingness and capability to co-develop a fit-for-purpose potency assay early.
• Cryo & cold chain — controlled-rate freezing, storage, and validated distribution.
• Capacity availability — historically the binding constraint; confirm real slots, not pipeline intentions.
• Regulatory experience — IND-enabling and, ideally, BLA/MAA experience with comparability across process changes.

05Regulatory and quality considerations by region

CGT products are regulated by the FDA's CBER (Office of Therapeutic Products) and, in Europe, as ATMPs under the EMA's Committee for Advanced Therapies (CAT). Expectations are still evolving, which raises the premium on a CDMO that engages regulators fluently. Comparability is uniquely hard here: process changes can alter the product in ways that are difficult to characterise, so locking the process early and planning comparability up front is critical. Replication-competent virus (RCL/RCA) testing, vector-integration assessment, and robust potency assays are standard agency focal points. Accelerated pathways (FDA RMAT, EMA PRIME) can compress timelines but intensify CMC scrutiny.

06Common manufacturing challenges and how to mitigate them

• Low vector yield & high empty-capsid ratio — mitigate with producer cell lines, optimised transfection, and purification (e.g. gradient/AEX) tuned for full/empty separation.
• Transfection scalability — move from adherent to suspension early if commercial volumes are foreseeable.
• Potency assay development — start early; an undefined potency assay blocks comparability and filings.
• Comparability across process changes — freeze the process before pivotal material; agree a comparability protocol with the CDMO.
• Cold-chain & chain-of-identity failures — validated logistics and an auditable COI/COC system.
• Capacity constraint — reserve capacity contractually and consider a vector-specialist + cell-processing split.

07Global supplier landscape and manufacturing hubs

CGT capacity is concentrated in the US and Western Europe, with notable specialist clusters in Spain (Viralgen), the UK (ViroCell Biologics), Japan (Takara Bio), and the US (National Resilience, VGXI, Genezen Labs). CDMO Hub lists 93 CDMOs offering cell & gene therapy and 75 with viral-vector capability.

08Capacity trends and market outlook

For most of the last decade, viral-vector capacity was the industry's tightest bottleneck, with multi-year waitlists. A wave of investment has since added capacity, but it is unevenly distributed: suspension-AAV at commercial scale remains scarce, while clinical-scale adherent capacity is more available. The market is shifting toward (1) suspension and producer-cell-line processes for AAV yield, (2) a gradual allogeneic ("off-the-shelf") tilt to escape autologous unit economics, and (3) consolidation as larger players acquire specialists. For sourcing teams, the headline is that capacity exists but the right capacity — at your vector, scale, and timeline — still requires early reservation.

09Typical development and scale-up timelines

10Questions to ask when evaluating potential CDMOs

• Is your operating model (scale-out autologous vs scale-up allogeneic / suspension AAV) the right match for our therapy?
• What vector yields and full/empty capsid ratios have you achieved at our target scale?
• Do you supply plasmid in-house, and how do you control that raw material?
• Will you co-develop a potency assay early, and what is your comparability approach across process changes?
• What is your actual available capacity and reservation mechanism — and your chain-of-identity / cold-chain validation?

11Recommended outsourcing strategy by development stage