UCSD - University of California - San Diego

08/05/2026 | Press release | Distributed by Public on 08/05/2026 16:14

Rebecsinib Clinical Trial Means New Options for Blood Cancer

Published Date

August 05, 2026

Article Content

Key Takeaways

  • A clinical trial of rebecsinib, an experimental anti-cancer drug, is underway at UC San Diego for patients with two types of blood cancer.
  • The investigational therapy holds potential for treating the more than 20 types of cancer that involve the ADAR1 gene.

A clinical trial of rebecsinib - a first-in-class investigational drug that inhibits the ADAR1 gene involved in the proliferation of more than 20 cancers - is underway at UC San Diego.

The first patient was treated July 6, according to principal investigator James Mangan, MD, PhD, professor of medicine at UC San Diego School of Medicine and a hematologist and oncologist at UC San Diego Health. He called the drug "promising."

"This trial has great science behind it," Mangan said. "It uses a totally novel mechanism and really is for patients who have a desperate, unmet need."

The Phase 1 clinical trial, sponsored by Aspera Biomedicines, is open to adults 18 years of age and older who have secondary acute myeloid leukemia (AML) that has either recurred or not responded to treatment. It's also open to patients with higher-risk myelofibrosis. Both are rare blood cancers for which few treatment options exist initially - and no good options if they return.

For AML and myelofibrosis patients, the rebecsinib clinical trial means hope, Mangan said: "If this works, it's a good option for those who don't otherwise have targeted agents available to them."

UC San Diego Sanford Stem Cell Institute Director Catriona Jamieson, MD, PhD, a hematologist and researcher who discovered the drug, said she is "thrilled to take it from bench - and a bench on the International Space Station (ISS), no less - to the bedside of patients who need it most."

"Rebecsinib shows all the promise in the world not only to halt the progression of multiple cancers, but to shrink them, as well as prevent their spread to multiple sites in the body," she added.

One of the First Drugs Tested in Space

The U.S. Food and Drug Administration green-lit rebecsinib for clinical trial in March of last year, making it the first and only ADAR1 inhibitor with an investigational new drug application.

It's one of the very first drugs studied in the cosmos. Jamieson, who is also a professor of medicine at UC San Diego School of Medicine and chief of its Division of Regenerative Medicine, has sent multiple research payloads to the ISS, testing the drug on various types of highly lethal cancers with ADAR1 involvement like ovarian cancer, metastatic breast cancer, AML and glioblastoma multiforme - experiments made possible by millions in grants from NASA's In-Space Production Applications program.

In fact, in the summer of 2024, Jamieson received the prestigious ISS National Laboratory Compelling Results Award in Biology and Medicine for her discovery that the drug blocks the activation of ADAR1 in cancer - in space.

"Seeing Dr. Jamieson's cancer stem cell research launch on SpaceX CRS-34 - mere weeks before the first patient received rebecsinib in clinical trial - was nothing short of extraordinary," said donor Rebecca Moores, whose funding of Jamieson's lab made possible the drug's development. "Hope is literally on the horizon for patients with blood cancer - and, hopefully, soon, those with other types of cancer as well."

Scientists are still learning about the distinctive properties of space that threaten human health, including microgravity and galactic cosmic radiation. Such conditions create a uniquely stressful environment that mimics an accelerated version of aging and disease progression on Earth. Depending on the experiment, one month in microgravity can give researchers a preview of a few years, if not more than a decade, of maturation on Earth. This allows them to quickly see how a patient's cells might age or how a medical condition like cancer might manifest in extended time. It also gives them a quick preview of how a drug might work long-term on a patient's cells, whether a tumor or a miniature organ created from stem cells.

A member of the lab of Catriona Jamieson, MD, PhD, prepares a vial of investigational new drug rebecsinib ahead of the launch of Axiom 4 in July 2025. The drug - which inhibits the gene ADAR1, implicated in the growth of more than 20 cancers - is now available via clinical trial at UC San Diego for patients 18 years of age and older who have secondary acute myeloid leukemia (AML) that has either recurred or not responded to treatment, or higher-risk myelofibrosis.

The landmark NASA Twins Study of 2015-2016 found that space can affect the immune system, gut bacteria, body weight, serum metabolites, immune system, gene expression and cognition of astronauts, among other health factors. Jameison's research found that space also activates ADAR1, which, in turn, produces ADAR1p150, a protein that promotes tumor growth by hiding cancer from the immune system.

"Space gives Dr. Jamieson a tremendous chance to see a lot of changes in stem cell DNA in a short period of time," Mangan said.

Rebecsinib, he added, could be "a therapeutic mechanism to restore stem cell function after space travel" for astronauts. "If that's true, it could also be very applicable to an analogous situation that occurs not in a two-week space journey, but over the course of 60 years of life as a human being, over which we accumulate similar stresses to, and mutations in, stem cells."

'Every Patient Needs Hope'

Rebecsinib's June clinical trial launch is only the beginning. The trial may eventually expand to other ADAR1-involved cancers, including lymphoma, glioblastoma multiforme and metastatic breast cancer.

Among those hopeful for the impact of rebecsinib is patient advocate Andrew Schorr, 75, who has lived with myelofibrosis and chronic lymphocytic leukemia (CLL), another blood cancer, for decades.

His myelofibrosis is relatively stable at the moment, he said. If that were to change, however, rebecsinib "might be another option - and I would be grateful."

Schorr is no stranger to clinical trials. He has participated in two over the years - one for CLL and another for deep vein thrombosis - and has covered many over his career as a medical journalist.

"Every patient needs hope for what could be their next treatment, because these drugs peter out," he said. "Cancer finds a way around them. They're not as effective over time, as your disease progresses. You're always left wondering what the next option is. The fact that there could be a next option gives me a lot of hope."

Patient advocate Sandra Dillon, 50, was diagnosed with an aggressive form of myelofibrosis in 2006. She spent 13 years taking fedratinib, an anticancer medication used to treat intermediate or high risk myelofibrosis - a drug that Jamieson played a prominent role in reviving when the FDA placed it on clinical hold.

Those were magical years, Dillon said, full of hiking and traveling with her husband and enjoying normal life.

"The side effects I experienced were so minimal that it was like taking Advil for a headache," she said. "That's how not-a-thing it was in my life. Fedratinib really fought back the disease in an amazing way. You wouldn't have believed I was sick at the time."

More recently, however, her disease "broke out of its chains and started getting really, really bad," Dillon said. She had hoped to participate in the rebecsinib clinical trial but wasn't able to wait. She underwent a bone marrow transplant last fall, before the clinical trial was underway.

The transplant process "has been an incredibly difficult experience," she said. "If you could just take a pill, it would be a far better solution. When I think about rebecsinib, I think of it as that next stage - if one medication stops working, there are other options that could be effective for this very rare blood disease."

A New Model for Drug Development?

Schorr is excited to witness rebecsinib's story arc, having watched other cancer drugs, like the blockbuster Keytruda, rise to greatness over the years.

"It meets an unmet need and will hopefully extend lives," Schorr said of rebecsinib. It could play an even more significant role in cancer medicine, he added, if it serves as proof of concept for expediting the path to clinical trial by gathering data in outer space.

"Could this be an example of a new model for drug development?" he mused. "And could rebecsinib be helpful for other conditions?"

Schorr isn't alone in his optimism. Mangan said cancer centers "across the U.S. are very excited about opening this trial."

And so is he.

"I'm just really enthusiastic about the science behind this drug," he said. "To take it from a basic science paper published in Cell Stem Cell in 2023 to first-in-human Phase I clinical trial in just three years is a tremendous effort. Dr. Jamieson has a proven track record of bringing drugs successfully from bench to clinic, and ultimately to FDA approval, for patients."

Still in recovery, Dillon hopes to soon experience life as a "straight-up healthy person" for the first time in 20 years.

In case her transplant fails, however, "it's a huge relief knowing that rebecsinib exists," she said. "Give Dr. Jamieson another five years and she'll create a million more drugs. It's great to know that someone like her is on my side."

Read more news about: School of Medicine, Health Sciences, UC San Diego Health, Sanford Stem Cell Institute, Health Innovation, Space

UCSD - University of California - San Diego published this content on August 05, 2026, and is solely responsible for the information contained herein. Distributed via Public Technologies (PUBT), unedited and unaltered, on August 05, 2026 at 22:14 UTC. If you believe the information included in the content is inaccurate or outdated and requires editing or removal, please contact us at [email protected]