Beyond-compendial water in 1 mL vials - for plasmid dilution in clinical CAR-T cell manufacturing
A developer of CAR-T cell therapies needed water of the highest attainable quality to dilute a plasmid before electroporating human T cells - one critical, small-volume step in the manufacture of clinical trial material for an early-phase (Phase 1) study with fewer than 100 patients. PAN-Celltech supplied WFI Beyond, custom-filled into 1 mL vials sized to a single manufacturing run, so the water could go into use without delaying the clinical timeline.
This story is published with the customer anonymised. It describes a real PAN-Celltech engagement; the customer's name is withheld.
Water that goes straight into the cell product
In one step of a CAR-T manufacturing process, a plasmid is diluted in water and then introduced into human T cells by electroporation. The water therefore comes into direct contact with both the genetic material and the patient's cells - and whatever it carries goes with them into the final cell product, which cannot be depyrogenated or purified afterwards. For a step like this, water quality is not a general-purity question; it is a product-safety one.
Highest-quality water, in very small volumes, urgently
The customer manufactures CAR-T cell products for an early-phase clinical programme (Phase 1). The brief was clear: water of the highest available quality - free of nucleases that could degrade the plasmid, with minimal endotoxin, sterile, and documented to a level a clinical programme can rely on.
At the same time, only a very limited volume is needed per manufacturing run, and as a Phase 1 study the programme is expected to treat fewer than 100 patients. Standard bottle or bag formats would have meant opening a large container for a fraction of a millilitre and discarding the rest - and it was needed quickly, before the gap reached the clinical timeline.
WFI Beyond, custom-filled into 1 mL vials
WFI Beyond met the requirement - and on the attributes that matter most for gene therapy, exceeded it. The water is specified far beyond the Ph. Eur. monograph: endotoxin more than 50× below the limit, nuclease-free, sterile, animal-component-free, with all 24 ICH Q3D elemental impurities specified and quantified on every lot.
For handling, PAN-Celltech filled the water customer-specifically into 1 mL vials - the customer's initial requirement was 100 vials, in line with the expected size of the Phase 1 study. Each vial is a single, ready-to-use unit for one manufacturing run: opened once, used for the plasmid dilution, discarded. No partial use of larger containers, no repeated opening, no carry-over between runs.
What “highest quality” meant - and what WFI Beyond delivers
For diluting a plasmid that goes straight into human T cells, the critical water attributes are absence of nucleases, ultra-low endotoxin and sterility. The WFI Beyond specification sets each of them well past the compendial floor:
| Attribute | Ph. Eur. 0169 limit | WFI Beyond specification | Why it matters for plasmid dilution & electroporation |
|---|---|---|---|
| Endotoxin | ≤ 0.25 EU/mL | < 0.005 EU/mL | Endotoxin carried into the T-cell product cannot be removed afterwards |
| Nuclease activity | not in monograph | RNase & DNase: none detected | Protects plasmid DNA integrity before electroporation |
| Sterility | – | sterile · single-use | Ex vivo cell culture follows - no margin for contamination |
| Total organic carbon | ≤ 0.5 mg/L | ≤ 0.05 mg/L | General purity marker |
| Conductivity (20 °C) | ≤ 1.1 µS/cm | ≤ 0.2 µS/cm | Adds no uncontrolled ions to the electroporation mix |
| Elemental impurities | not in monograph | 24 ICH Q3D elements specified & quantified (ICP-MS) | Documented impurity profile for the dossier |
| Animal origin | – | animal-component-free | TSE/BSE question answered up front |
| Regulatory | – | FDA Type IV (excipient) DMF MF044505 | Referenceable via Letter of Authorization |
Values are the published WFI Beyond Standard specification; elemental impurities to ICH Q3D(R2), 24 elements by ICP-MS. Each delivered lot is released against the specification and reported on its Certificate of Analysis. See The WFI Beyond Standard for the full specification.
From enquiry to delivery in about eight weeks
Five days from enquiry to specification match, a custom fill less than four weeks later - and release after full QC testing.
- 110 Aug 2026 · Urgent enquiryWater for plasmid dilution in CAR-T manufacturing; initial request for 100 × 1 mL vials.
- 215 Aug 2026 · Specification matchCustomer requirements mapped against the WFI Beyond Standard.
- 38 Sep 2026 · Custom 1 mL fillCustomer-specific vial format filled aseptically by PAN-Celltech.
- 46 Oct 2026 · Release & deliveryLot released with Certificate of Analysis after a QC testing period of at least 4-5 weeks.
- •After delivery · In usePlasmid dilution prior to electroporation of human T cells.
A requirement met - and on key attributes exceeded
The customer received water that matches the most demanding requirements of a CAR-T manufacturing step - in a format designed around the way the water is actually used. One vial per run means the supply scales exactly with the number of patients treated, without waste from oversized containers. Because the specification, Certificate of Analysis and DMF were already in place, the water could be qualified on existing documentation and deployed in the manufacture of clinical trial material, keeping the programme on schedule.
For an early-phase CAR-T study with fewer than 100 patients, the plasmid dilution uses less than a millilitre per run - but it touches the genetic material and the patient's cells directly. Getting this input right, in the right size, removes a variable at exactly the stage where deviations are most costly.
Why it works
- 1A defined standard, not a claimWFI Beyond is specified beyond the monograph on endotoxin, nucleases, TOC and elemental impurities - and proven lot by lot on the CoA.
- 2The format follows the applicationFrom 1 L bags to 1000 L - or, as here, custom 1 mL fills: one vial per CAR-T manufacturing run.
- 3Documentation ready for the clinicCoA per lot, BSE/TSE & ICH Q3 declaration and a filed FDA Type IV (excipient) DMF reduce the qualification effort.
- 4Scale without re-qualifyingThe same qualified water moves with the programme from Phase 1 into later phases and larger formats.
Frequently asked questions
Why does water quality matter so much in CAR-T manufacturing?
Because in this step the water dilutes a plasmid that is then electroporated into human T cells. Whatever the water carries - endotoxin, nucleases, non-sterility - goes with it into the final cell product, which cannot be depyrogenated or purified afterwards. Endotoxin control, nuclease-free water and sterility are therefore product-safety attributes, not general-purity ones.
Why fill Water for Injection into 1 mL vials?
Because only a fraction of a millilitre is used per manufacturing run. One ready-to-use vial per run means no opening of a large container for a tiny volume, no repeated opening and no carry-over between runs - and the supply scales exactly with the number of patients. WFI Beyond is available from 1 mL custom fills up to 1000 L, so the format can follow the application.
Can we reference the documentation in a clinical submission?
Yes. Each lot ships with a Certificate of Analysis reporting appearance, conductivity, TOC, endotoxin, RNase/DNase activity, sterility and all 24 ICH Q3D(R2) elemental impurities by ICP-MS. WFI Beyond is backed by a filed FDA Type IV (excipient) Drug Master File (MF044505), which you cross-reference through a Letter of Authorization, together with a signed BSE/TSE and ICH Q3 declaration (non-animal origin, out of scope of EMA/410/01 Rev. 3).
Keep reading
- Technical paper TP-04: WFI Beyond - beyond compendial
- In-Depth Edition D02: The WFI Beyond Standard
- Overview: The Open Downstream
- Service: Customized Solutions - PAN Complete
- ← All case studies