Dr. Maximilian Hoerner, head of optogenetics at Prolific Machines, discusses how light can be used to enable dynamic gene expression.
Prolific Machines
Novel therapeutic modalities are expanding what is possible in medicine, offering greater efficacy, precision and adaptability for diseases that were previously untreatable or poorly served by existing therapies. As a result, biotherapeutic pipelines have become increasingly filled with a wide range of complex biologics such as multispecifics, Fc fusions, cytokines, viral vectors, and molecules with tightly constrained glycan profiles. These modalities place far more complex and varied demands on production host cells than traditional antibodies. Meanwhile, the industry continues to rely on traditional expression architectures, but expanding screening campaigns, layering on more analytics, and refining clone selection is no longer sufficient to get these novel modalities to the clinic. With recent research suggesting that the next-generation biologics market is projected to reach $251 billion by 2033, the industry must confront a fundamental mismatch between product complexity and the static gene expression systems used to manufacture them.
Conventional biomanufacturing has simply not kept pace with the complexity of next-generation biotherapeutics. Dynamic, light-controlled gene expression offers an alternative approach, providing the flexibility required to meet the varied demands of these new modalities.
Optogenetics as a dynamic control layer
Traditional cell line development (CLD) relies on constitutive promoters that drive static, unchanging expression levels throughout the culture. As production is always on, cells must divide and manufacture protein simultaneously, with both competing for the same cellular resources. While this model worked for monoclonal antibodies, it is poorly suited for next‑generation biologics that are either toxic or more burdensome to produce, inevitably increasing the trade-off between higher specific productivity and cell growth.
Optogenetics is a biological control technology that uses light‑responsive proteins to regulate cellular behaviour. These proteins originate from natural photoreceptors found in organisms that use them to sense and respond to specific colours of light in their environment. By connecting these proteins to the cellular machinery, light-inducible gene-expression systems can be engineered. By integrating such expression systems into CHO or HEK cells, the expression of target genes can be tuned to any desired level by changing the amount of illumination. If the light is turned off, expression will cease, meaning the expression is fully reversible. This makes the technology fundamentally different from existing biomanufacturing techniques and promises to be a genuine breakthrough for the industry.
The optogenetic gene expression system consists of two parts: a light-inducible transactivator and its corresponding light-inducible promoter. First, the transactivator is stably integrated into the host to establish an optogenetic chassis cell line, which only needs to be generated once. Developers can then integrate their gene of interest using familiar CLD workflows, with one key modification: the constitutive promoter in the expression vector is replaced by the light-inducible promoter.
Lightening the load
Optogenetic control introduces several capabilities that are difficult to achieve using conventional expression systems. As expression timing can be precisely controlled, production can begin only once cells have reached optimal density. Expression strength can be tuned by adjusting light intensity or illumination patterns, and because light can be applied and removed repeatedly, gene expression can be modulated dynamically throughout the process.
By avoiding the metabolic burden of protein production during CLD, which typically penalises the highest-producing clones, optogenetic systems enable recovery of those high producers. In the uninduced state, clones can proliferate efficiently; once induced, they shift their resources from growth toward protein production.
The scalability question
A key question for any emerging bioprocess technology is whether it can scale, and Prolific Machines has made that a central focus of its platform development. Rather than requiring bespoke vessels or specialised infrastructure, the company has engineered modular illumination systems designed to retrofit directly into standard incubators and bioreactors. This approach keeps adoption friction low while ensuring that light delivery can be controlled with the precision needed for optogenetic expression.
Indeed, scalability depends on understanding the role of light within the system. In this application, light is a signal, rather than an energy source. Because the photoreceptors remain active for 30–60 minutes after stimulation, the cells do not need continuous or uniform exposure. Standard mixing dynamics are sufficient to ensure that each cell receives the same average light dose over time, enabling homogeneous and consistent activation by only illuminating a fraction of the total culture volume. Prolific Machines has run optogenetically-controlled processes at 50 L and 200 L, validating both performance and control at a scale that is commonly accepted to be representative of commercial scale. Detailed modelling and analysis based on these data give additional confidence that the same principles extend to commercial volumes all the way up to 20,000 L.
Applications of dynamic expression
The most intuitive application of dynamic gene expression is the ability to fully separate the growth and production phases. Under noninduced, dark conditions, cells expand rapidly without the metabolic burden of protein synthesis. Once the culture reaches the desired density, illumination initiates maximum production on demand. This approach has already demonstrated strong performance at small scale. In one of Prolific’s recent intensified fedbatch studies at 250 mL, monoclonal antibody titers reached 21 g/L. With ongoing improvements in clone performance, process design and light optimisation, Prolific expects to push titers into the 25 g/L range.
Dynamic expression is particularly valuable for proteins that impose a heavy burden on host cells. Cytokines, viral proteins required for viral vector production, and certain multispecifics are difficult to express constitutively because they cause stress or are toxic to the production host. By restricting expression to defined windows, it is possible to increase yields and reduce cytotoxicity across multiple programmes. Temporal control of viral protein expression has also improved titers in early viral vector applications.
The ability to modulate expression levels further offers a new route to stoichiometric control for multispecifics. Instead of designing and screening large numbers of genetic constructs, Prolific places some chains under constitutive promoters and others under colour‑specific optogenetic control. This allows developers to tune chain ratios directly with light and adjust relative expression profiles during scale‑up if a clone’s behaviour shifts, ensuring optimal stoichiometry is maintained. This approach can shorten development timelines, reduce downstream burden and salvage otherwise problematic candidates.
Looking ahead, dynamic expression opens the door to precise control of post‑translational modifications. By regulating the expression of glycosylation enzymes rather than the therapeutic protein itself, the team has demonstrated the ability to tune galactosylation and sialylation levels of a monoclonal antibody as a direct function of light dose. This capability could reshape how manufacturers achieve and maintain critical quality attributes across complex biologics, as well as reducing biosimilar development costs.
Conclusion
As the complexity of modern biologics increases and the variety of modalities grows, the limitations of static expression systems have become impossible to ignore. Optogenetics introduces a dynamic expression architecture that aligns production with cellular capacity, reduces metabolic burden, and enables capabilities such as tuneable stoichiometry and real-time modulation of post-translational modifications that were previously out of reach.