Lonza Admits a 'Bioconjugation Gap' in Its US Network: Mapping ADC Outsourcing Capacity — and a Blank Space on the Tariff Wall

Lonza leadership has confirmed that bioconjugation is a gap in its US capacity network and a potential area of investment. Its ADC footprint is Swiss-centred: multipurpose, high-potency payload-linker suites at Visp are scheduled to begin ramping in 2029, and a second commercial aseptic ADC filling line at Stein is expected to operate in 2030; management says the company is involved in more than half of the commercial ADC products on the market. With ADCs sitting on the Section 232 exemption list but 'origin' logic growing ever more important, the scarcity of US-based ADC conjugation capacity is a blank space worth marking on the global outsourcing map.

According to Pharma Manufacturing, Lonza management has confirmed in recent interviews and analyst calls a fact rarely discussed publicly: bioconjugation capacity is a gap in the company's US network, and a potential area of investment. For a CDMO that holds about 484,000 litres of US large-molecule capacity — roughly 61% of its global total — openly acknowledging the absence of one modality on US soil is itself an informative map.

Visp and Stein: the twin stars in a Swiss valley

Lonza's ADC build-out is European-centred. In September the company announced an expansion of payload-linker capacity at Visp, adding production and purification capabilities for highly potent linkers inside an existing GMP facility, alongside dedicated analytical and process-development laboratories. CEO Jean-Christophe May put it concretely on the July call: 'In Visp, we are building a set of multipurpose, highly potent payload linker suites, which are scheduled to commence ramp up in 2029. We continue to see strong customer demand in this area.' The site is designed for scale-out, allowing additional suites as demand grows.

Drug-product capacity advances at Stein. Three years ago Lonza extended a collaboration with a major biopharma partner and built a dedicated commercial aseptic ADC filling line; in July it announced a second commercial-scale aseptic ADC filling line at the site, expected operational in 2030. The resulting picture: payload-linkers at Visp (2029 ramp), conjugation and drug substance on existing high-potency lines, aseptic fill-finish at Stein (second line 2030) — all of it in Switzerland.

'More than half of commercial ADCs': concentration at the top, and everyone else arming

Vertommen, who leads Lonza's ADC and bioconjugation business, told the publication the company is 'involved in more than half of the commercial products' on the market; May added that Lonza has brought commercial ADCs to market and is one of the few CDMOs with commercial capacity in the modality. Set that against WuXi XDC's disclosed position — a global ADC XDC outsourcing share above 24% and four consecutive World ADC Best CDMO awards — and the shape of the market is clear: two poles, Europe (Lonza's Swiss sites) and China (WuXi XDC, Asymchem and peers).

The Chinese pole is arming fast. Asymchem conceded in an October investor survey that payload-linker capacity is 'very tight' and is accelerating expansion — its Fengxian site's 2,000-litre PL line has completed first delivery, with overseas orders above 50% of its ADC book. WuXi XDC's Singapore XmAb/XBCM3 facility passed GMP release in August with XDP4 following, while Wuxi XDP5/XDP6 fill-finish lines and the Jiangyin payload-linker base are under construction. With both poles expanding, the third option — a non-Chinese, non-Swiss site a Western client might want — looks thin.

The US gap on the tariff map: ADCs are exempt today, but origin never went away

The gap reads differently against the policy map. Section 232 pharmaceutical tariffs exempt ADCs and other high-complexity modalities at a 0% rate — so ADC imports enter the US duty-free today. But exemption is a policy variable, not a law of nature: the list of 19 favoured jurisdictions and the 20% onshoring mechanism both remind drugmakers that 'origin' can be repriced.

That is the subtlety of Lonza's US bioconjugation gap: if ADC's tariff exemption ever tightens, drugmakers will discover there is almost no 'US-based conjugation capacity' to switch to, because global ADC conjugation capacity is concentrated in Switzerland (Lonza) and China (WuXi XDC, Asymchem). Lonza flagging US bioconjugation as a potential investment area is, at bottom, a hedge against that policy tail risk — and in a context where Chinese capacity is repeatedly re-examined through BIOSECURE-style lenses, the distance between Western clients' de-risking wishes and the absence of US conjugation capacity will, for now, be filled by Switzerland.

Editor's view: conjugation is the hardest link to copy

Along the ADC value chain, filling lines are the easiest to replicate and payload-linkers the hardest. High-potency toxin handling, linker chemistry know-how and the interface with antibody conjugation all take years to accumulate. That is why Lonza's new PL suites will not ramp until 2029, why Asymchem calls PL capacity 'very tight', and why WuXi XDC can license its WuXiTecan-2 platform itself (up to USD 885M of potential consideration from Earendil). The scarcity of conjugation capacity is not measured in reactor litres; it is measured in chemistry.

For global biotechs the map carries a blunt message: before 2030, if you need commercial-scale ADC manufacturing and do not build it yourself, the realistic options run through Switzerland and China. The desire to diversify origin is strengthening; the capacity to do so is not.