The ‘Figure It Out Later’ Tax: What Downstream Processing Really Costs Biotech Startups

The early-stage biotech playbook: move fast on the biology. Prove the mechanism. Worry about manufacturing later.

It makes sense. The molecule is the thesis. Engineering is solvable with money.

But “solvable with money” is exactly right — and the amounts are larger than most founding teams expect.

Downstream Is Where the Money Goes

Manufacturing costs in biotech are dominated by downstream processing. Not upstream. Upstream — growing cells, running fermentation — is capital-intensive but relatively efficient. Downstream, the sequence of separation steps that takes crude broth to purified product, is where most of the operating cost lives.

Industry data puts downstream at 50–80% of total manufacturing cost for biologics.

For a drug with $500/g manufacturing cost, that’s $250–400/g tied up in the purification train. At any meaningful scale, that’s not an afterthought. It’s the number.

Where it goes specifically

• Resin Chromatography resin: Protein A resin costs $8,000–$15,000 per liter. A commercial-scale column holds 500 L of resin. Resin replacement is a recurring line item.
• Membrane Membrane replacement: UF membranes have a finite number of cycles. At high throughput, replacement is budgeted annually.
• Buffers Buffers and reagents: Ion exchange processes use large volumes of salt solutions. At 10,000 L fermentation scale, buffer costs are non-trivial.
• Yield Yield losses: Every purification step loses product. Three steps at 85% yield = 61% total recovery. 39% of every batch ends up in the waste stream.
• Failure Failure investigations: When a purification step underperforms at scale (it will, at least once), the cost isn’t just the failed batch — it’s the investigation and process development work to fix it.

The Tech Transfer Problem

CMOs are essential for startups without manufacturing infrastructure. What most founders underestimate: the cost of tech transfer — getting a CMO to run your process reliably.

Tech transfer requires:

• Detailed process documentation (batch records, process descriptions, specifications)
• A defined, reproducible process
• Multiple engineering runs to qualify the CMO’s equipment and operators
• Process validation runs to prove the CMO can hit your spec consistently

If your process is underspecified when you walk in the door, you’re paying for process development at CMO day rates.

Why Bench Scale Doesn’t Predict Commercial Scale

The separation steps that work at bench scale don’t always behave the same at pilot or commercial scale. Predictable reasons:

• Column aspect ratios change A 1 cm × 10 cm bench column scales to a 30 cm × 30 cm pilot column. Binding capacity per liter often drops.
• Mixing is harder at scale A pH adjustment that takes 30 seconds in a beaker takes 20 minutes in a 2,000 L tank. If your process has a short hold step, it may not be feasible at scale.
• Feed composition drifts Optimize downstream for a specific feed, then upstream changes media or conditions — your separation performance shifts with it. Robust processes are designed with feed variation in mind.
• Cleaning validation is harder than expected Regulatory agencies require evidence that cleaning procedures actually clean. Exotic solvents or unusual pH ranges make cleaning validation a project in itself.

What $50K in Process Development Buys

A focused 3–6 month program before your first CMO engagement:

• 1 Feed characterization — what’s actually in your broth, at what concentrations
• 2 Separation technology screening — which unit operations give you useful selectivity
• 3 Prototype flowsheet — 2–4 step train with defined operating parameters
• 4 Robustness check — what happens when key parameters drift ±20%
• 5 First-pass mass balance and yield projections

Cost: roughly $50–150K at a CRO.

That’s a return most startups should find compelling.

The Calculation Worth Making Now

Take your target dose. Multiply by the number of patients in Phase 1. Add a batch failure buffer. That’s the material you need before your first clinical read-out.

Price it at current CMO rates:

If that number is material to your runway, your purification process is a financial risk that deserves engineering attention now.

untangle.bio lets you drag-and-drop unit operations, wire up feed composition, and immediately see yield, purity, and cost estimates at each step. It won’t replace a process engineer. But it will help a founding team ask the right questions before the expensive conversations start.