Choosing a viral vector cdmo on process rather than on capacity: how viral vector manufacturing, aav viral vector manufacturing, viral vector production, aav vector production and viral vector process development divide between what you own and what the partner owns, what viral vector development, viral vector characterization and aav characterization must deliver before a batch means anything, why aav titer and lentivirus titer are three different numbers until the method is named, where an aav cdmo and a plasmid cdmo are different suppliers with different slots, what aav vs lentivirus and lentivirus vs aav actually trade in payload, persistence and manufacture, what gmp lentivirus production, lentiviral vector production, lentivirus vector production, lentivirus manufacturing and lentivirus production cost at each grade, what lentiviral particles, a lentiviral vector, a lentiviral system, a lentiviral expression vector, an expression plasmid, a lentiviral plasmid, lentiviral plasmids, lentiviral packaging plasmids, aav plasmids, an aav plasmid, aav packaging plasmids and lentivirus packaging commit the process to, how a gene delivery system and gene delivery route change the specification entirely, and what viral vector manufacturing companies should tell you before a slot is booked

Running the selection

1. Decide what you are buying: a platform or a pair of hands. A platform partner runs their established process and gives you speed and predictability, at the cost of process ownership and sometimes of the ability to move. A contract manufacturer running your process gives you control and portability, at the cost of time and of doing the development yourself. Both are valid. Confusing them is not.
2. Pin down every titre method by name. Genome titre, capsid or particle titre and infectious or transducing titre measure different things and differ by large factors. Two partners quoting a titre without naming the method are not quoting the same number. Insist on the method, the standard used and the acceptance range.
3. Ask about empty and partial capsids explicitly. For adeno associated vectors the fraction of capsids carrying no genome or a partial one drives the dose and the safety profile, and separating them is a real unit operation with a real yield cost. A process that does not address it is quoting a number that will not survive the first regulatory conversation.
4. Review the analytical package, not just the process. Identity, potency, purity, residual host protein and nucleic acid, residual plasmid, replication competent vector testing and sterility. Ask which methods are established at the partner, which are transferred and which are subcontracted, because subcontracted methods dominate turnaround.
5. Model scale honestly against the intended dose. Work backwards from doses required, dose level and the vector needed per dose to the batch size that programme implies, then ask whether the partner has run that scale on that platform. Scale up in vector manufacture is not linear and a partner's largest demonstrated batch matters more than their installed volume.
6. Negotiate failure before success. What happens if a batch fails release, who pays, how quickly a reslot is available, and what data you receive from a failed run. These terms are far easier to agree before a campaign than during one.

Why titre disagreements are the central problem

Every commercial conversation about vector runs on a titre, and titre is the least standardised number in the field. Genome titre depends on the assay design, the standard and even the primer position. Infectious titre depends on the cell line, the multiplicity and the readout. A partner reporting a favourable number may simply be reporting a different measurement.

The practical defence is to name the method in the contract, require the standard to be described, and have a sample measured by an independent laboratory at least once. That single cross check has saved more programmes than any amount of capacity planning.

What process development should leave behind

A transferable process description, defined critical parameters with ranges, in process controls, an analytical package with method descriptions, and the data that justifies each choice. If what you receive is a batch record and a certificate, you bought manufacturing rather than development and should not expect to move.

Agree the deliverable list at the proposal stage and attach it to the statement of work. Development deliverables that were assumed rather than specified are routinely not produced.

Containment, approvals and the calendar

Vector work carries containment requirements and institutional approvals on both sides, and material movement across borders adds permits. These are administrative rather than technical, and they are the most common reason a slot is missed.

Start the approvals when the partner is selected, not when the campaign is scheduled. The technical readiness is rarely the binding constraint.

Common questions

Should a programme use a suspension or an adherent process?

Suspension scales predictably and is the default for anything heading past early clinical work. Adherent processes remain common at small scale and for legacy comparability, but moving from adherent to suspension later is a process change with comparability consequences, so decide early.

Which titre number should a contract be written against?

The one the dose is calculated from, stated with its method. For gene therapy that is usually a genome titre with a defined standard, accompanied by an infectivity ratio. A contract against an unnamed titre is a contract against nothing.

How early should analytical development start?

Before manufacturing, not alongside it. Methods that are not ready when a batch is released force retrospective testing on retained samples, which delays everything and occasionally cannot be done at all.

Can a process be moved between partners?

Only if it was written down in a form that transfers, and only if you own it. Platform processes are usually not portable, which is a reasonable trade to make knowingly and a painful one to discover.

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