Over the past decade, chimeric antigen receptor (CAR) T cell therapy has emerged as one of the most transformative innovations in cancer treatment, harnessing the immune system’s power to target and eliminate malignant cells. By redirecting patient-derived T cells to recognize specific antigens, CAR T therapies have achieved remarkable success in hematologic malignancies, particularly in refractory disease.
Ex vivo is not a model pharma likes. It’s technically and clinically proven. However, it’s a pain to administer.
—Adam Inche, Lentitek
However, the current ex vivo model remains a major logistical and financial barrier. Leukapheresis, viral transduction, and expansion under good manufacturing practices (GMP) often span several weeks and approach half a million dollars per patient, limiting scalability and global accessibility.
“Ex vivo is not a model pharma likes,” Adam Inche, CEO and founder of Lentitek, said at the Advanced Therapies conference. “It’s technically and clinically proven. However, it’s a pain to administer.”
Even allogeneic therapies, which promise off-the-shelf scalability, face hurdles. The FDA approval of Ryoncil, an allogeneic mesenchymal stem cell (MSC) therapy for pediatric acute graft-versus-host disease (GvHD), demonstrated the potential of off-the-shelf approaches. However, larger batches still raise consistency challenges and require advanced bioprocessing techniques, and issues such as host rejection, limited persistence, and GvHD remain.
In response, companies are turning to in vivo CAR T approaches, which deliver genetic instructions directly into circulating lymphocytes, effectively turning the body itself into a bioreactor. This approach promises faster manufacturing timelines, lower costs, standardized dosing, and broader patient access — particularly for those with rapidly progressing disease.
At last week’s Advanced Therapies conference, DDN attended a series of talks and discussions highlighting the technical innovations, clinical strategies, and regulatory considerations driving the shift from ex vivo to in vivo and off-the-shelf cell therapies.
The promise — and perils — of in vivo therapies
In vivo solves many of the issues of cell therapy, but now you have all of the issues of gene therapy — accurate dosing, immunogenicity, off-target effects, and organ deposition.
—David Peritt, Lupagen
In vivo CAR T therapies represent a potential paradigm shift, eliminating the cumbersome ex vivo manufacturing step and enabling more rapid, distributable immunotherapy. However, these advantages come with new scientific and clinical challenges.
As David Peritt, Chief Scientific Officer, and cofounder of Lupagen, explained, “In vivo solves many of the issues of cell therapy, but now you have all of the issues of gene therapy — accurate dosing, immunogenicity, off-target effects, and organ deposition.” Unlike ex vivo CAR-T, where the final cell product can be characterized before infusion, in vivo therapies rely on vectors to find and modify the right cells in the body. Ensuring precise targeting, controlling the duration and level of CAR expression, and minimizing immune responses are critical hurdles that must be addressed to achieve safe and durable therapeutic responses.
Vector design has become a central focus for companies pursuing in vivo CAR T. VIVEbiotech, for instance, specializes in lentiviral vectors and is now supporting 14 in vivo programs. Natalia Elizalde, Chief Business Officer at VIVEbiotech, told DDN that the company began developing in vivo lentiviral programs in 2018, but momentum over the last two to three years has accelerated significantly. “Lentiviral vector production has been demonstrated to be very efficient, so the cost of goods is low,” she said. “This has been key for in vivo CAR T, alongside the fact that there are now ongoing clinical trials demonstrating safety.”
“Our lentiviral vectors are not only highly productive in terms of titer; we also work with modified serotypes to more efficiently target specific cell types for in vivo applications,” Elizalde said. “By using modified cell lines, we can decorate the lentiviral vector in a way that helps it evade the immune system, improving the chances of successful delivery to the desired cells.”
Meanwhile, Lentitek is addressing specific limitations of current lentiviral systems. Inche highlighted that existing vectors often suffer from incorrect splicing, resulting in incomplete viral particles or premature activation of the CAR gene in the production cells, reducing the quality, potency, and safety of the therapy. To solve this, Lentitek has developed a promoter that sits upstream of the viral genome, stabilizing the genetic material and preventing these splicing errors.
Lentitek has now partnered with both ViroCell and Annogen, combining splicing-resistant lentiviral vector manufacturing with GMP-scale production and highly T cell-specific promoter design to improve the safety, consistency, and scalability of CAR T therapies.
A twist on in vivo delivery
While companies like VIVEbiotech and Lentitek are focused on refining viral vectors for direct in vivo delivery, Lupagen is taking a hybrid approach that combines the speed of in vivo CAR-T with the control of ex vivo engineering. A key challenge with in vivo therapies is achieving precise targeting and consistent CAR expression without triggering unwanted immune responses or off-target effects. Traditional in vivo administration relies on the vector finding and modifying the right cells inside the body, which can be difficult to control and raises safety concerns, particularly with systemic dosing.
Lupagen’s Xynvivo System addresses this by temporarily routing a patient’s peripheral blood cells outside the body in a closed-loop, bedside procedure. The immune cells are incubated with the viral vector or nanoparticle carrying the CAR gene for 20-30 minutes, allowing accurate delivery to the target cells. Unbound particles are removed before reinfusion, reducing exposure to non-target tissues and lowering the risk of immune reactions.
“This approach enables highly controlled dosing, lower immunogenicity, and improved safety compared with systemic administration of viral vectors,” Peritt said. The platform also enables repeat dosing and avoids the need for lymphodepleting chemotherapy, making it safer and more accessible for a broader patient population. By leveraging procedures already familiar to clinicians, such as dialysis-like extracorporeal setups, Lupagen aims to accelerate adoption while mitigating many of the risks traditionally associated with systemic gene therapy.
Looking ahead
These examples represent just a handful of the hundreds of talks and discussions at the Advanced Therapies conference, highlighting the breadth and pace of innovation in cell and gene therapy. As Miguel Forte, current President of the International Society for Cell & Gene Therapy, described the current landscape, it resembles a “three-body problem” of autologous, in vivo, and allogeneic therapies: “We know where the three are now, but we don’t know where they will be in the future.”
For companies navigating this rapidly evolving field, success will require more than scientific ingenuity. It will also demand careful alignment of development priorities, regulatory planning, manufacturing strategy, and patient access considerations. Whether through refined viral vectors, hybrid extracorporeal approaches, or off-the-shelf allogeneic platforms, the innovations emerging today are setting the stage for a new era in CAR-T and gene therapies — one in which treatments can be safer, faster, and more broadly accessible than ever before.
