Encoding a New Era in Gene Therapy: Why We Invested in Stylus Medicine

At Tachyon, we invest in emerging platforms that shift paradigms — and Stylus represents a major step toward scalable, programmable in vivo gene insertion therapies. Our investment in Stylus Medicine’s Series A reflects our conviction that in vivo CAR-T therapy in oncology, as well as gene insertion therapy in genetic diseases, are reaching an inflection point — and that Stylus is among the few companies uniquely positioned to turn this vision into clinical reality.

A growing number of teams across biotech are now racing to bring CAR-T therapies inside the body, aiming to simplify manufacturing, lower costs, and dramatically expand access. Stylus stands out not because they’re alone in this ambition, but because of how they’re executing it.

Their approach uses lipid nanoparticles (LNPs) to deliver large serine recombinases (LSRs) and single stranded nanoplasmids up to 13kb into cells – enabling complex constructs with multiple genes and regulatory elements.

Importantly, it’s an effective approach to in vivo CAR-T therapy — one that combines precise gene insertion, large-payload delivery, and a clean, non-viral format to address both the biological and logistical challenges of scaling this modality.

The shift to in vivo

Over the last decade, the success of ex vivo CAR-T therapies has delivered breakthrough outcomes in hematological cancers and established a new therapeutic paradigm. But while these therapies have proven curative for some, the process remains burdensome: patient cells must be harvested, genetically modified in a facility, expanded over several weeks, and then reinfused into the patient’s body following lymphodepleting chemotherapy.

This model works, but it doesn’t scale. Less than 20% of eligible patients ever receive CAR-T today. High costs, logistical complexity, and the need for bespoke manufacturing have kept access limited to major academic centers and late-line settings.

Stylus represents the next leap forward: in vivo CAR-T.

In vivo CAR-T changes that equation by eliminating the need to modify cells outside the body. Instead, gene editing components are delivered systemically — directly into the patient — using lipid nanoparticles (LNPs). If successful, the result is a one-time, off-the-shelf infusion that reprograms a patient’s immune cells internally, with fewer steps, less toxicity, and broader accessibility.

This approach is:

• Faster — potentially moving from biopsy to treatment in days, not weeks
  
  
• Scalable — a single batch of therapy can treat many patients
  
  
• Less invasive — no apheresis, no lymphodepletion, no hospital stay

This means treatment timelines can shrink from weeks to hours — and more importantly, access is no longer limited to patients who can tolerate intensive procedures or specialized care.

The implications mirror what mRNA did for vaccines: a foundational shift, not an incremental gain.

Why Stylus stands out

Among the emerging class of in vivo players, Stylus brings three critical advantages that we believe will define the winners in this next wave:

1. Site-Specificity

Stylus uses large serine recombinases (LSRs) —  a class of enzymes capable of high-precision gene integration without genome cuts. This contrasts with CRISPR or lentiviral systems, which often rely on random integration or introduce double-stranded breaks that can lead to unintended consequences.

2. Payload Size

Stylus can insert large, complex genetic payloads — including multiple genes and regulatory elements — from a single vector. This enables next-gen products designed to overcome tumor microenvironment resistance, address antigen escape, and enhance persistence — all from a single infusion.

3. Preserved DNA Integrity

Most editing technologies create double-stranded breaks (DSBs) in the genome — a cellular red flag that can lead to p53 activation, DNA toxicity, or genomic instability. Stylus’ approach avoids DSBs entirely. Their engineered LNPs deliver mRNA and DNA in a way that preserves DNA integrity, reduces innate immune activation, and minimizes toxicity — thanks in part to their proprietary single-stranded DNA plasmids, which dramatically lowers cytokine induction.

Together, these features offer a level of precision, safety, and modularity that we believe is foundational to in vivo cell therapy becoming a true platform — not just a scientific possibility.

A Platform, Not a Product

Stylus isn’t chasing the current CAR-T market — it’s expanding the entire gene therapy landscape. By enabling safe, site-specific delivery of large, complex payloads into diverse cell types, the platform opens the door not only to in vivo immunotherapy, but also to programmable interventions for a broader array of diseases — addressing conditions from hemophilia to muscular dystrophy — with precision, modularity, and the potential for redosing.

Stylus’ platform could power a broad pipeline of applications, including:

• Redosable, off-the-shelf immunotherapies
  
  
• Durable, non-viral treatments for genetic liver diseases
  
  
• In vivo reprogramming of immune cells for autoimmune and fibrotic disorders

Backing the Team Shaping What’s Next

At the helm of Stylus Medicine is Emile Nuwaysir, Ph.D., a seasoned biotech leader with a track record of building and scaling companies at the intersection of cellular and genetic medicine. Prior to Stylus, Emile served as CEO of BlueRock Therapeutics, where he helped develop a pipeline of first-in-class cell therapies and oversaw the company’s acquisition by Bayer. He also previously served as president and COO of Cellular Dynamics International, guiding the company from inception through IPO and its eventual acquisition by Fujifilm.

The scientific founder behind Stylus’ platform is Patrick Hsu, Ph.D., a widely recognized leader in genome engineering. Patrick’s foundational work in CRISPR-based tools has earned him recognition as an MIT Technology Review Innovator Under 35 and a Forbes 30 Under 30 honoree in Science. As an assistant professor of bioengineering at UC Berkeley and co-founder of the Arc Institute, his research continues to shape the future of programmable therapeutics.

We’re proud to join a world-class syndicate of co-investors — including RA Capital, Khosla Ventures, and ARCH. 

Biology, Rewritten Like Software

Stylus exemplifies the evolution of biology as a computational system, where modular payloads can be inserted, expressed, and adapted like software — without viral vectors, without double-stranded breaks, and without centralized manufacturing. We’re excited to support their mission to make genomic medicine faster, safer, and radically more accessible.