In vivo cell and gene therapy has moved rapidly from an exciting scientific proposition to one of the most closely watched areas in advanced therapies. But has the field truly reached an inflection point – and, if it has, just how quickly can it move from breakthrough data to meaningful clinical momentum?
That question sat at the heart of a lively panel discussion at Advanced Therapies Europe 2026, where experts explored the clinical progress fuelling enthusiasm for in vivo approaches, alongside the scientific and safety challenges that could determine the speed of the next wave.
From scientific promise to clinical proof
Perhaps the biggest change over the past few years has been the emergence of clinical data showing that in vivo approaches can deliver meaningful efficacy.
As Stefanos Theoharis observed, some of the first clinical results have been stronger than many in the industry expected. Early efficacy, combined with safety profiles that in some cases appear manageable, has helped give the field significant momentum.
That momentum has not gone unnoticed by investors and large pharmaceutical companies. A wave of deals and growing strategic interest has created what the panel described as something close to a “gold rush”, as companies seek exposure to a technology that could fundamentally change how advanced therapies are delivered.
For Margot Pont, however, commercial enthusiasm alone does not mean the technology has reached maturity.
The attraction is clear. Ex vivo cell therapies have demonstrated remarkable biological potential, but the model of manufacturing an individual therapy for an individual patient creates complexity, cost and access challenges. If treatment can instead be generated directly inside the patient, the implications for scalability and accessibility could be significant.
Yet the clinical dataset remains relatively young. The next stage will require moving beyond impressive individual results towards reproducibility across patients, programmes and indications.
Safety will define the pace
One message came through particularly strongly: enthusiasm cannot run ahead of the evidence.
Maria Eugenia Alonso Ferrero highlighted the importance of understanding the safety implications of introducing gene-modifying technologies directly into patients. Questions around specificity, immune responses, vector behaviour and potential unintended effects become particularly important when therapies cannot simply be withdrawn once administered.
Long-term follow-up will therefore remain essential.
The advanced therapy sector already understands that some treatment-related effects may only emerge years later. In vivo approaches add another layer to that challenge, making it critical to understand where vectors travel, which cells they reach, how strongly those cells are activated and whether unintended genetic changes could occur.
The panel’s message was not that these challenges should slow innovation for its own sake. Instead, emerging patient data needs to be studied systematically so that every programme helps inform the design of the next.
As Theoharis put it, the field is not yet at the point where it can say, “It works – what else do we need to do?” There is still a great deal to learn.
Where could in vivo make the biggest impact?
Oncology and haematology are likely to remain important proving grounds. They offer an established scientific foundation for cell and gene therapies and, crucially, a benefit-risk equation that can support experimentation with new treatment approaches.
But the longer-term opportunity could be much wider.
Autoimmune disease represents an especially compelling possibility. The ability to use a scalable in vivo platform across larger patient populations could dramatically expand the reach of advanced therapies. At the same time, the tolerance for risk changes when moving from patients with advanced cancer into chronic or potentially manageable diseases.
That means success in oncology cannot simply be replicated elsewhere without adjustment. Delivery, specificity and safety thresholds will become even more demanding as indications broaden.
Evolution, not a modality war
Ultimately, the rise of in vivo therapy does not necessarily signal the decline of ex vivo approaches.
Instead, the emerging landscape is likely to be one of coexistence. Different diseases, patient populations and biological targets will demand different solutions. The question for developers, investors and pharma companies will increasingly be not which modality “wins”, but where each platform creates the greatest clinical and commercial value.
The in vivo inflection is real – but its trajectory will depend on evidence.
Early results have shown enough promise to transform expectations. The next challenge is converting that promise into repeatable efficacy, well-understood safety and therapies capable of reaching far larger patient populations.
The wave is building. How far and how fast it travels will be determined by what the industry learns from the patients being treated today.
)