But ask that question today — and something has shifted.

We now see alternative host platforms with real clinical and regulatory data behind them. Not papers. Not proofs of concept. Actual data. Approved products. Phase 1b clinical trials. Regulatory meetings with FDA, EMA, and PMDA.

Moss has Phase 1b data for an enzyme replacement therapy — and the EMA waived human viral testing requirements, a regulatory advantage CHO will never have.

Plant pharming had a fully approved COVID-19 vaccine from Health Canada in 2022.

Insect cells are already behind Flublok, Cervarix, and Nuvaxovid.

Cell-free protein synthesis has ADC candidates in clinical trials — and it’s the only system that can site-specifically incorporate non-natural amino acids, which is exactly what next-generation ADCs require.

So: is CHO still the host of choice?

The answer is: it depends on what you’re making. And that is a far more interesting answer than the one we had ten years ago.

Introduction

I want to start with a question I’ve been sitting with for a while.

Over the past two and a half years, we’ve hosted some extraordinary scientists on this show — people building biologic manufacturing platforms from scratch, using organisms nobody thought belonged anywhere near a GMP facility. Moss. Microalgae. Silkworms. Plants. Cyanobacteria.

Every conversation was compelling. Every guest made a strong case. And every time, I walked away impressed by the science — but also carrying a nagging question: when you put all side by side and cross-reference them against the published evidence, what does the real picture look like?

That’s what this episode is about.

No guest today. No platform advocacy. Just the data, the patterns, and my assessment of where each platform actually stands — and where it doesn’t.

In Part 1, I’ll walk you through what each platform claims to offer, and where the evidence supports or complicates those claims. In Part 2, we tackle the big question head-on: will any of these replace CHO?

Why CHO Still Wins — and Why That Makes the Exceptions Interesting

Before we talk alternatives, a rigorous look at the baseline is worth it.

Chinese hamster ovary cells are the gold standard for glycosylated monoclonal antibodies, and they earned that position. Fed-batch titers routinely reach five to ten grams per liter. The glycosylation machinery is well-characterized and predictable. Regulatory agencies have cleared hundreds of CHO-derived mAbs — which means the risk profile is known, the review process is familiar, and the questions are well-understood on both sides. And every major CDMO on the planet has CHO capacity, giving you vendor optionality at every stage from early development to commercial production.

That combination — high productivity, regulatory familiarity, ubiquitous infrastructure — is hard to displace. And I don’t think it’s going to be displaced for the products where it already excels.

So the relevant question is not whether CHO loses. For standard glycosylated mAbs with conventional Fc function, CHO doesn’t lose. The relevant question is: where does CHO leave a gap?

There are three places to look. Cost structure — if a platform can produce the same molecule at significantly lower capital expenditure or cost of goods. Speed — if it can take you from gene sequence to first protein in weeks rather than months. And intrinsic product quality — if a platform naturally delivers a glycan profile or post-translational modification that CHO would require extensive engineering to match.

Every platform wins somewhere. The goal of the next 30 minutes is to figure out where.

Five Platforms, Five Key Takeaways

Let me take you through each platform — what the guest claimed, and what I think is the empirical signal from the published data.

Platform 1: Moss — Episodes 163 and 164, with Andreas Schaaf from Eleva

The claim Andreas made — and that Eleva has built their entire company around — is that moss offers human-like glycosylation without any animal-derived components. No BSE or TSE risk. That’s not a small thing. It simplifies regulatory submissions and eliminates a whole category of safety concern from your development dossier.

But here’s the regulatory outcome that I keep coming back to: the European Medicines Agency waived human viral testing requirements for moss-derived biologics. I want you to think about what that actually means in practice. Viral clearance studies are expensive. They require external testing labs, validated assays, and significant timeline. Skipping that step is not a routine accommodation — it’s a meaningful competitive advantage on both cost and timeline for a human injectable product.

The second point: moss produces afucosylated glycans natively. You don’t engineer it. That’s just how the organism processes proteins. For oncology antibodies where the therapeutic mechanism depends on ADCC — antibody-dependent cellular cytotoxicity — afucosylation directly enhances potency. CHO can be engineered to produce afucosylated mAbs, but that means knocking out the fucosyltransferase gene, validating clone stability through extended culture, and accepting added regulatory complexity. Moss gives you that profile from the start.

💡Honest takeaway: for a standard Fc-intact mAb where fucosylation level doesn’t drive efficacy, CHO remains the better choice. But for an oncology antibody where ADCC is the mechanism for otherwise unproduceable proteins — moss can be your platform of choice.

Platform 2: Microalgae — Episodes 141 and 142, with Muriel Bardor from AlgaBiologics

The sustainability story here is compelling, and I don’t want to dismiss it. Photosynthetic biomanufacturing using CO2 as a carbon source is carbon-negative by definition. Muriel’s team has demonstrated roughly 70 percent cost reduction per unit reactor volume, and the oligomannose glycan profile these cells produce is actually favorable for ADCC through enhanced NK cell binding.

Now here’s the part I have to be direct about. The yield gap between microalgae and CHO is approximately 1,000-fold. CHO produces grams per liter. Microalgae produce milligrams per liter. I want to say that again — it’s not a rounding error, it is the defining technical challenge of this platform, and it has not been solved yet.

As of early 2025, there is no microalgae-produced injectable in clinical trials. AlgaBiologics submitted a pre-IND dossier to the French ANSM and projected first-in-human trials for 2026. That is progress — real, trackable progress. But a 1,000-fold yield gap means you need roughly 1,000 times the reactor volume to produce the same amount of product. That largely erases the cost advantage, at least at current productivity levels.

💡Honest takeaway: watch this platform over a five-to-ten-year horizon. The sustainability thesis is credible. The yield problem is not yet solved.

Platform 3: Molecular Pharming — Episodes 235 and 236, with Waranyoo Phoolcharoen from Baiya Phytopharm

This is the platform I keep coming back to when people ask about pandemic preparedness, and for good reason. The core capability is transient expression in Nicotiana benthamiana — a tobacco-related plant. The number that matters: three to four weeks from gene sequence to first protein. That timeline is not matched by any other platform for complex biologics. Not even close.

The techno-economic data backs up competitive cost of goods — between $100 and $150 per gram for VLP-based vaccines, which is competitive with CHO for this product class.

And then there’s Covifenz. Medicago’s plant-derived COVID-19 vaccine received full regulatory approval from Health Canada in 2022. Full approval. Phase III-positive. Plant-manufactured. What happened next is what people cite to dismiss the platform — the product was discontinued because Medicago’s parent company had tobacco industry ownership ties that triggered political opposition in key markets.

The vaccine worked. The regulatory process worked. The manufacturing worked. What failed was a corporate ownership structure that created non-technical political risk. Those are completely separable things. Dismissing the platform based on what happened at Medicago is like dismissing CHO-based manufacturing because a CHO company had a bad quality event. The platform’s technical track record is intact.

And the manufacturing scale is real: Baiya Phytopharm operates a cGMP facility in Bangkok with capacity to produce up to five million COVID-19 vaccine doses per month — demonstrating that plant-based biomanufacturing is not a lab-scale curiosity but an operational production system.

💡Honest takeaway: for VLP vaccines and pandemic rapid-response, plant pharming is the fastest path from sequence to dose, with real regulatory precedent behind it.

Platform 4: Silkworms — Episodes 217 and 218, with Masafumi Osawa from KAICO

This is the platform that surprised me most the first time I really looked at it. One silkworm pupa is functionally equivalent to 100 to 1,000 milliliters of conventional insect cell culture volume. The upstream infrastructure cost is a fraction of a stainless steel bioreactor. There’s no bioreactor at all — the production model is a living organism.

KAICO has PMDA alignment for a Phase I clinical trial of a norovirus VLP vaccine produced in silkworms. A veterinary VLP vaccine is already registered and commercially used in Vietnam. That is real traction.

Here’s the challenge: batch consistency in a living multicellular organism is a QA problem with no established regulatory precedent for human injectables. Every other system we’ve discussed — CHO, moss, insect cells, plants — operates through clonal cell populations or tightly controlled plant growth conditions. Silkworm pupae are individual organisms with organism-to-organism biological variability. Managing that variability to meet the batch release specifications required for a human injectable is scientifically unsolved territory at commercial scale.

💡Honest takeaway: the clearest near-term path is veterinary vaccines and oral delivery formats where variability tolerances are wider. The PMDA Phase I alignment is the signal to watch — that is meaningful regulatory progress. The step to human injectables is real and not yet complete.

Platform 5: Cyanobacteria — Episodes 229 and 230, with Tim Corcoran from Deep Blue BioTech

Carbon-negative photosynthetic manufacturing. Secretion-capable strains. Potentially very low cost of goods as a long-term proposition. I think these claims are credible as a vision.

And there is real progress worth noting. Tim Corcoran’s work at Deep Blue Biotech makes a compelling case for where the platform is heading. The ocean-derived cyanobacterial strain they work with — discovered around 2020 — is more robust and faster-growing than most previously characterized strains. The molecular biology toolkit has matured considerably: CRISPR-based editing, improved genome annotation, and transformation methods now make the R&D process feasible within reasonable timelines. The direct secretion of the target molecule into the culture medium — no cell lysis required — reduces cost of goods by an estimated 25–35% compared to conventional intracellular production. Photobioreactors scale out rather than up: because they are modular glass tube arrays, a 10,000-litre installation behaves similarly to a 100-litre lab system, which is a meaningful engineering advantage. And the yields are tracking ahead of early projections — Tim described multiples of what they initially thought achievable, which changes the economic calculus for commodity-scale applications like biofuels. The near-term commercial focus is high-value specialty ingredients — hyaluronic acid for personal care at roughly $2,000 per kilogram — precisely to fund the platform’s development toward lower-margin, higher-volume products.

Here’s the current reality: no cyanobacteria-produced injectable has entered human clinical trials. There are cyanobacterial strains that produce genuine toxins — cyanotoxins — and managing that contamination risk requires rigorous strain characterization and clearance validation that doesn’t yet exist as an established regulatory framework for injectables. The strongest near-term applications are biomaterials and potentially oral delivery drugs.

💡Honest takeaway: this is the most distant from clinical reality of the five. That makes it a long-term watch, not a near-term manufacturing decision.

Closing Observation

Step back and look at all five together, and one pattern becomes very clear.

None of them is a universal CHO replacement. Not one. Each wins in a specific product category or a specific manufacturing context. And the platforms that have made the most regulatory progress — moss, plant pharming, insect cells — all found their niche first, then built regulatory precedent around it.

They didn’t try to compete with CHO on CHO’s own terms. Moss didn’t try to match CHO titers for standard mAbs. Plant pharming didn’t try to compete at commercial antibody scale. They found where CHO leaves a gap, and they built in that gap.

Which brings me to the question I want you to carry into Part 2.

Is “will it replace CHO” even the right question to be asking?

I don’t think it is. And in Part 2, I’ll give you the question I think is worth asking instead — and a framework for actually answering it.