Capstan: The Story of the Open Minds Behind the Acquisition
of an In Vivo CAR‑T Pioneer

By Nandita Shangari, Andrew Levin, and Peter Kolchinsky

FINANCE | BIOTECH

Photo by Oliver Roos on Unsplash

August 19, 2025

When Capstan Therapeutics agreed to be acquired by AbbVie for a record-breaking price of $2.1B upfront, it had just started its Phase 1 study in healthy volunteers, was well-capitalized, and was on a mission to put a range of autoimmune diseases into deep remission and maybe even cure them. Some people will wonder about the significance of this deal and what lessons it may have for their own ventures. We can share our insights. We’ve been on the Capstan journey since the beginning and are incredibly proud of the team and its work. This is a story worth hearing.

Prologue 

Imagine if you could transiently reprogram a patient’s own T cells – within their own body – to reset the immune system to suppress or even cure autoimmune disease or unleash those T cells against cancer. This wasn’t just a scientific thought experiment – it was the founding vision of Capstan Therapeutics.

Born from the rich scientific ecosystem at the University of Pennsylvania, Capstan set out to turn this ambitious idea into reality. The company was built on the findings of pioneering scientists whose collective work reshaped the landscape of modern medicine. Among them were Haig Aghajanian, John Epstein, Carl June, Bruce Levine, Drew Weissman, Hamideh Parhiz, Ellen Puré, and Steve Albelda – a constellation of minds who helped bring to life CAR‑T therapies, mRNA technologies, and lipid nanoparticle (LNP) delivery systems. 

It was Haig Aghajanian’s vision that helped catalyze collaboration among Penn’s most distinguished scientific leaders, shaping a multidisciplinary foundation for what should hopefully become a pioneering therapeutic approach.

In the beginning…

Before there was Capstan, there was TeeFib, founded in 2020 to develop in vivo CAR‑T for cardiac fibrosis. Christian Homsy became TeeFib’s first CEO (having previously been at Celyad), recruited Adrian Bot from Gilead/​Kite to be TeeFib’s CSO and Haig joined the company leaving academia. 

They initially struggled to raise funds, which we would largely attribute to the choice of indication. To this day, we still don’t know whether CAR‑T can help with fibrosis; that indication is further down in Capstan’s pipeline and not a primary driver of the current syndicate’s confidence in the company.

After six months of trying to raise, Christian reached out to the Novartis Venture Fund (NVF), recognizing Novartis’s deep experience in cell therapy through its work on Kymriah, the first FDA-approved CAR‑T therapy. That connection proved pivotal. Nandita Shangari (then at NVF, now Managing Director at RA Capital) and Michal Silverberg (Managing Director, NVF) immediately saw the potential of the TeeFib platform. Nandita, having served on the global Kymriah project team, had worked with Carl June and Bruce Levine and witnessed firsthand the immense manufacturing and supply chain challenges that burdened ex vivo cell therapies. 

What TeeFib was proposing – a targeted in vivo approach using LNP/​mRNA delivery to transiently engineer immune cells inside the body – was truly different. It was essentially off-the-shelf autologous CAR‑T with no turnaround time (i.e., off the shelf!) and a low cost of goods. Though the proposed indication was fibrosis, Nandita saw this as a variable to be pressure tested, not a reason to say ​“no”.

Together with Erez Chimovits and Roy Amariglio (Partner and Principal at OrbiMed, respectively), they partnered with the founders and management to reimagine the company. They decided that the company should pivot from fibrosis to oncology – where clinical development paths were better understood – and refocused the company on CD19, a validated target in B‑cell malignancies (TeeFib had been focused on a Fibrosis Activating Factor [FAP]). NVF/​OrbiMed gave TeeFib a term sheet for a seed financing.

At about that time, Andrew Levin, Partner at RA Capital, and Michael Rosenzweig, an Executive-in-Residence at Raven (RA Capital’s incubator) were also exploring the frontier of in vivo immune cell reprogramming. Their interest had been sharpened by their recent success with Tidal Therapeutics, a company also built around targeted mRNA delivery, which was acquired by Sanofi for its potential to transform cell therapy from an ex vivo to an in vivo process, in a deal led by RA Capital partner Josh Resnick.

When Andrew learned of the TeeFib financing from Michal and Nandita, he proposed that RA Capital not only invest but also embed its relevant operational expertise into the company. Michael Rosenzweig, with a track record in immuno-oncology drug development and a deep understanding of the scientific terrain, was the perfect fit, becoming the company’s Chief Development Officer to guide its early programs forward.

As the venture continued to take shape, CSO Adrian Bot brought Vida Ventures to the table; he had previously worked on CAR‑T with Arie Belldegrun, Helen Kim, and Rajul Jain at Kite Pharma. At the time, Vida was actively seeking to make a strategic investment in the emerging field of in vivo cell reprogramming, and Capstan’s approach aligned perfectly with their vision.

In November 2021, Vida joined NVF, OrbiMed, RA Capital, and Polaris Partners in the seed round, providing the foundation for the company’s formal launch. This was the moment the company officially changed the name from TeeFib to Capstan Therapeutics. TeeFib no longer made sense since the company wasn’t focused on fibrosis, and Capstan was suggestive of capstone, a crowning achievement, which is what it felt like to truly launch the company after so many people had poured passion and thought into its creation over the course of 2021.

The company’s first major hire post-financing was Priya Karmali, who joined as Chief Technology Officer. This was no ordinary hire – Priya brought deep expertise in CMC (i.e., manufacturing), which was essential for Capstan’s ambitious goals. Note to all companies who are developing complex therapeutics: CMC matters a lot and not just to you! If you rush to prove a mechanism with some barely-GMP skunk mix, you’ll eventually face major delays switching to commercial-grade manufacturing, and therefore such proof-of-concept data aren’t as valuable (especially to an acquirer). 

Around this time, Nandita joined RA Capital. Because of her pivotal role in Capstan’s formation, it made sense for Nandita to remain on the board, so Andrew transferred RA Capital’s board seat to her, staying involved informally as part of RA Capital’s Capstan support team (note: all our companies have entire teams of people focused on their success – in the case of Capstan, shout out to Jonathan Pritz, Craig Randall, Laura Stoppel, Derek DiRocco, and Breanna O’Reilly).

All the while that TeeFib was being reshaped into Capstan, Haig’s write-up of his tLNP work was winding through peer review and, shortly after the seed round closed, the paper finally came out in Science. Michael Baran (Partner, Pfizer Ventures) saw the paper and approached the syndicate to see if Pfizer could invest in the company. 

The biotech markets were already in decline by this point and it was clear that developing the Capstan technology would require considerable capital.

The company launched its Series A financing round in 2022, just six months after raising their Series Seed, with Pfizer Ventures stepping up to lead and putting forward the initial term sheet. This catalyzed interest from an impressive roster of strategic and financial investors. Leaps by Bayer, Eli Lilly and Company, Bristol Myers Squibb, and Alexandria Venture Investments all joined the syndicate, recognizing both the scientific strength of the technology and the high-value clinical applications it could unlock. 

Between the Series Seed and Series A, the company raised $165M and was now ready to pivot to serious execution. At this critical juncture, industry veteran Laura Shawver was recruited to be CEO. A seasoned operator, Laura had previously led biotech ventures such as SynthorX and Silverback Therapeutics – both centered on highly novel technologies and familiar to RA Capital and OrbiMed. 

While her prior companies had been focused on oncology, Laura would soon find herself leading the company’s final key pivot to autoimmune disease. That pivot was prompted by the publication in November 2022 of Georg Schett’s groundbreaking demonstration that anti-CD19 autologous CAR‑T treatment of patients with lupus could lead to deep and durable remissions. 

Without that insight, Capstan might very well have continued to focus on oncology as its lead programs. 

Economists call the application of one technological insight to another ​“scientific spillover”. The Apollo project gave us not only footprints on the moon but arguably more useful things like microwave ovens and Velcro shoes: that is scientific spillover. And the impact of the Schett study on Capstan’s focus was an exemplar of biomedical scientific spillover.

But that pivot wasn’t a given. To have that impact, the data needed to fall on fertile, open minds. At Capstan, every day was an opportunity to do better based on new information, and the Schett data were nothing if not radically new information. We can’t say enough about the joys of working with open-minded people. 

A Fork in the Road

By the fourth quarter of 2023, over a year after the Series A and with inflation fears sending biotech indices back to their lows of 2022, Capstan Therapeutics faced a challenging financing climate. The broader biotech sector was deep in the throes of what many dubbed a ​“nuclear winter” and, with later-stage companies trading at deep discounts, early-stage companies were especially out of favor. At this point, Capstan didn’t need to raise additional funds, but it also wasn’t clear that it would be able to raise when it eventually had to. 

Yet, even in this climate, Capstan stood apart because of its strategic options.

Pharmaceutical companies were closely tracking Capstan’s progress, particularly their NHP data from the lead program CPTX2309, a targeted CD19 CAR‑T therapy delivered via mRNA-LNP. The preclinical results were compelling and generated a flurry of strategic interest. Capstan received multiple term sheets from major pharmas seeking collaboration or licensing agreements for CPTX2309. Some of these offers carried upfront and milestone payments that would have been precedent-setting for a preclinical program.

This strategic attention ignited intense debate within Capstan’s syndicate. Accepting a deal could de-risk the company’s path but might also cede upside too early. We hadn’t come this far to partner our lead, and yet, capital was tight. Unless the company could count on investors to keep fueling its work, a partnership would be prudent. 

Believing strongly in both the team and platform, RA Capital took a bold stance (given market conditions, it felt really bold to us). Rather than standing by while Capstan opted for a partnership, we stepped forward with a term sheet, offering to lead a $125M Series B with a $50M commitment. It didn’t hurt that we had just received a large influx of cash from the acquisitions of several of our portfolio companies. With that fresh cash in hand, we wanted to let Capstan stay independent and build value at least through early clinical data. With the Series B financing, Capstan would be equipped to execute a healthy volunteer Phase I study, initiate early Phase II testing, and continue strengthening its CMC capabilities. We figured that just showing that CPTX2309 could safely knock down B cells in healthy volunteers would be a major milestone and a ​“hero-zero” value inflection. 

The strategy resonated with the syndicate and new investors Forbion, Mubadala Capital, Sofinnova Investments, JJDC and Perceptive Advisors. Despite the broader market malaise, Capstan’s oversubscribed $175M Series B became one of the most notable financings of the year and allowed Laura to decline the considerable partnering interest Capstan had for its lead program. 

While securing capital (Series B was announced in March 2024), Capstan also built out the clinical team. The company made two pivotal hires from RA Capital’s Raven healthcare incubator team: in January 2024, Dr. Ramin Farzaneh-Far joined as Chief Medical Officer to help position Capstan’s clinical strategy with investors and potential pharma partners; in April 2025, Angela Pontius joined as Vice President of Clinical Operations to oversee Phase 1 and 2 clinical ops and logistics and to be the company’s liaison with autoimmune patients and advocacy organizations. Both were founding members of Raven’s Blackbird team (we try to name everything in Raven after birds), which is focused on clinical trial acceleration, and offered exactly the expertise that Capstan needed. With so many competing programs creating a gigantic autoimmune trial traffic jam, Capstan couldn’t afford to merge onto the same highway as everyone else.

Together, Ramin and Angela designed and initiated a clinical development strategy tailored to the novel nature of Capstan’s platform. Their leadership proved essential in translating Capstan’s preclinical promise into human proof-of-concept, setting the stage for a potential new class of immune cell-modifying therapeutics.

In May 2025, the company started its Phase 1 trial in Australia, becoming a clinical-stage company. We could tell you a whole other story about deliberations over where to do the study, but suffice to say that the FDA does not have a reassuring track record when it comes to expediently authorizing first-in-human trials of novel technologies. 

We held our breath on the day the first patient was dosed, which is scientifically proven to help with drug development. This was a highly anticipated moment for the company – years in the planning. In NHPs, the effect on B cells was rapid. What would happen in people?!!! 

We’re going to probably let you down by admitting that we can’t tell you anything more about the clinical program or the M&A process just yet. More will eventually be disclosed. 

The ultimate goal 

What we hope that you take from this story is an appreciation of how Capstan wasn’t born ​“Capstan”: it was shaped from an early idea by many people, entrepreneurs and investors alike, and built on the learnings of many parts of the biotech ecosystem. Brilliant individuals who could have insisted that their way was the right way instead kept an open mind, invited others to the table, and engaged in candid debates about every single variable. 

Those of us who have been involved in the Capstan journey will remain on the Capstan journey. This is not the end for any of us. The acquisition is a financial event and a strategic transfer to AbbVie of a technology that will continue to evolve and progress. Our goal is to see it treat and maybe even cure patients suffering from a range of autoimmune diseases and maybe even other kinds of indications that were further down in Capstan’s pipeline. It’s seeing medicines actually make a difference for patients – which is to say all of us and the people we care about – that drives us in our careers and gives meaning to our work.

Towards that end, we didn’t need to sell Capstan; the company had a clear vision, an exceptional team, and was very well capitalized to make progress for quite some time. Even in difficult markets, we think it would have been able to raise additional capital if the data merited continued development. 

The choice to sell was bittersweet for us but ultimately felt right from all angles. Key to our decision was that AbbVie is a very capable drug development organization. They are among the very best in the world at developing and commercializing autoimmune medicines. To refuse their offer did not seem like it would have been in the best interests of patients. 

Capstan’s acquisition price is likely a record-breaker, but it’s not a one-off for us. Within the last two years, when looking at early-stage M&A by upfront payment, RA Capital was one of the largest shareholders of and helped to create and shape three of the top four (Table 1) – Aliada, Mariana, and Capstan – putting in not only seed capital but contributing venture partners to the operating teams and serving on the boards.

Some think of M&A as an exit, but it’s also a beginning, because capital flows through an ecosystem, like carbon. Just as we routed cash from acquisitions in 4Q23 into Capstan’s Series B to help them avert a premature partnership, we are excited to redeploy the dollars from Capstan’s sale into other companies whose technologies may also revolutionize medicine. Hopefully we’ll have a chance to tell you about those someday.

And if you want to develop a new technology and are looking for open-minded partners to get elbow-deep in it with you to build a company, let’s chat.

Table 1: Private early-stage biopharma acquisitions since 2022

Table 1: This is a list of private, early-stage companies that have been acquired since 2022, ranked by size of the upfront payment. Companies in which RA Capital was involved are shaded green. These are not all the cases of private M&A but only those companies that Centerview deemed to have occurred prior to proof-of-concept (POC) data. POC can be subjective. Sometimes dosing a few subjects can yield instructive data. Generally, these are all companies that did not complete a Phase 2 study yet and so can at least all be called early-stage. Source: Centerview Partners