RA Capital doubles down on Siddhartha Mukherjee's vision for a new cell engineering approach, leading Vor's $110M Series B
Vor Biopharma is muscling up.

CEO Robert Ang, who was reluctant to divulge the headcount when discussing his move from Neon Therapeutics to Vor last August, readily offered that the team has grown from 6 to 50 in less than a year. The biotech is moving to a larger office on Cambridge Parkway Drive in weeks, giving it more space to complete the IND-enabling work and manufacturing scale-up — conducted by a CDMO partner — in preparation for clinical trials planned for the first half of 2021.
It’s also hauled in $110 million from its Series B, led by RA Capital Management and featuring new investors like Fidelity Management & Research Company, Pagliuca Family Office and Alexandria Venture Investments. 5AM Ventures, which co-led the $42 million Series A with RA Capital, also joined alongside old-timers PureTech Health, Johnson & Johnson Innovation — JJDC and Osage University Partners.
“Vor has an elegant approach to engineering hematopoietic stem cells that we believe is amongst the most promising innovations in oncology,” Joshua Resnick, managing director at RA Capital, said in a statement.

Pioneered by Columbia oncologist Siddhartha Mukherjee (who has chronicled the promise and price of the first generation of CAR-T therapies), the approach flips traditional cell therapy on its head. Rather than engineering immune cells to attack cancerous ones, or targeting tumor cells, Vor is tinkering with the healthy cells.
By editing out targets that are present in both healthy and malignant cells, the reasoning goes, scientists can unleash the full power of targeted therapies without having to worry about side effects.
They are starting out with CD33 for acute myeloid leukemia, but the new cash will fund some new research into other undisclosed targets.
Also known as Siglec-3, the protein is a common target for existing treatments like Pfizer’s antibody-drug conjugate Mylotarg. Large genomic databases suggest there are individuals who have lived their whole lives without ever expressing the CD33, Ang said, and researchers have shown that knocking it out in mice and human cells in vitro doesn’t seem to impact functionality.
The real test, of course, will have to be in the clinic.
“We hope to see that it’s entirely biologically redundant and safe,” Ang told Endpoints News.
On top of that — proving not only that they can edit the hematopoietic stem cells without inducing malignancy, but also retain their reproducibility — Vor is also aiming to test how their program, VOR33, may complement Mylotarg or a CD33-targeted CAR-T therapy, which would be a “novel novel treatment combination.”
Vor has had a chance to discuss these and other concerns with FDA regulators back in January, Ang added.
The trial would also be a test for the manufacturing process Vor has developed, packing everything from extraction to reinfusion in 48 hours.
“We’re doing it not just because we can do it, but also because I think it’s best for patients that we do it,” Ang said. Not only is there an urgency in the clinic, but less manipulation also means better chance of engraftment and healthier cells. “What that also does is it gives us hopefully flexibility further down the track to think about how it could, more importantly, roll us out on a late development or commercial basis.”
It could mean a regional model or on-site manufacturing; either way, it’s a decentralized future that Vor is now preparing for.