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Vor Biopharma says first patient given its gene editing therapy for leukemia is in remission

The Cambridge biotech company’s trial of the experimental treatment had faced a long delay.

A scientist at Vor Biopharma's Cambridge headquarters, where the firm is developing gene edited cell therapies for cancer.Vor Biopharma/Genevieve de Manio Photography

A Cambridge biotech company using CRISPR gene editing to develop therapies for blood cancers said that its experimental treatment for acute myeloid leukemia proved safe in the first recipient, who is currently in remission.

The preliminary results, announced Wednesday morning, were a long time coming for the 7-year-old company. The clinical trial of the therapy was delayed due to the COVID-19 pandemic, and the firm faced difficulties finding volunteers willing to participate.

The first-of-its-kind treatment regimen begins with chemotherapy to wipe out a person’s blood cancer and bone marrow. The patient then receives an infusion of new bone marrow cells that Vor’s scientists tweak with CRISPR gene editing to make them invisible to a potent cancer drug. That drug, Mylotarg, sold by Pfizer, is then given repeatedly to a patient while they are in remission to, hopefully, obliterate any remaining blood cancer and potentially prevent relapse.


Vor said its gene edited cells successfully engrafted in the first patient with no adverse events related to the treatment. “While it’s only one patient and we need to repeat this, we couldn’t have asked for a better outcome,” Vor president and chief executive Dr. Robert Ang said in an interview.

The 140-person company was founded in late 2015 based on research from the Pulitzer Prize winning author and cancer biologist Dr. Siddhartha Mukherjee, who envisioned that gene editing could be used to simultaneously empower a patient’s immune cells to seek-and-destroy blood cancers while sparing their healthy blood and immune cells.

While Vor has yet to fully realize that vision, any evidence that CRISPR gene editing works as intended, without safety concerns, is a boon to the growing field.

The revolutionary gene editing technique, which is barely a decade old, allows scientists to make precise changes to DNA. Dozens of companies are employing various forms of CRISPR to develop treatments for a bevy of conditions, including blindness, cancer, heart disease, muscular dystrophy, and more. A treatment for sickle cell disease developed by Boston-based Crispr Therapeutics and Vertex Pharmaceuticals could become the first commercial CRISPR therapy if approved by regulators next year.


While many companies are using CRISPR to turn off genes linked to disease, Vor uses CRISPR to make bone marrow transplants resistant to Mylotarg. The drug targets and kills any cells that display a protein called CD33 on their surface — which includes healthy blood and immune cells made from bone marrow, as well as cancer cells in leukemia.

By using CRISPR to prevent bone marrow cells from making CD33, doctors may be able to more safely treat patients with Mylotarg while they are still in remission, with the goal of preventing relapse, Ang said.

Scientists aren’t entirely sure what CD33 does, so Vor’s first test was focused on making sure it was safe to remove. The first patient received the gene edited bone marrow transplant in September and the first dose of Mylotarg in November, and was still in remission 60 days post transplant.

“The cells engrafted just like regular stem cells. There was nothing surprising,” Ang said, adding that it “was a great relief to everyone.”

Vor is also designing CAR-T cell therapies that hunt down any cells that make CD33. That therapy could potentially replace Mylotarg when paired with its edited bone marrow transplant — a treatment Vor calls trem-cel. One study of this approach is ongoing and another could begin next year.


At market close on Tuesday, Vor’s stock had fallen 91 percent since its peak in Feb. 2021, just weeks after its initial public offering.

In its most recent earnings call with investors, Vor said it had $136.1 million on hand at the end of September, enough to fund the company into the first quarter of 2024.

On Wednesday, the company said it would raise $115.8 million from an underwritten offering and a private placement of its stock. Ang said the money would fund Vor for an additional year and help it meet additional milestones with trem-cel and its CAR-T therapies.

Ryan Cross can be reached at ryan.cross@globe.com. Follow him on Twitter @RLCscienceboss.