Dashed Dreams and New Hope: A Quest to Cure Thymic Deficiency

By Kelly Shepard, PhD., CIRM’s Associate Director, Discovery & Translation

CIRM has previously blogged about advances in treating certain forms of  “bubble baby” disease”, where a person is born with a defect in their blood forming stem cells that results in a deficient immune system, rendering them vulnerable to lethal infections by all manner of bacteria, virus or germ.

If a suitable donor can be found, or if the patient’s own defective cells can be corrected through gene therapy approaches, it is now possible to treat or cure such disorders through a bone marrow transplant. In this procedure, healthy blood stem cells are infused into the patient, taking up residence in his or her bone marrow and dividing to give rise to functioning immune cells such as T cells and B cells.

Unfortunately, there is another type of “bubble baby” disease that cannot be treated by providing healthy blood stem cells, because the defective immune system is caused by a different culprit altogether- a missing or dysfunctional thymus.

Created for the National Cancer Institute, http://www.cancer.gov

T Cells Go to School

What is a thymus?  Most of us give little thought to this leaf-shaped organ, which is large and important in our early childhoods, but becomes small and inconspicuous as we age. This transformation belies the critical role a thymus plays in the development of our adaptive immune systems, which takes place in our youth: to prepare our bodies to fight infections for the rest of our lives.

One might think of the thymus as a “school”, where immature T cells go to “learn” how to recognize and attack foreign antigens (surface markers), such as those found on microorganisms or tissues from other individuals. The thymus also “teaches” our immune system to distinguish “self” from “other” by eliminating any T cells that attack our own tissues. Without this critical function, our immune system could inadvertently turn against us, causing serious autoimmune disorders such as ulcerative colitis and myasthenia gravis.

Many children with a severely deficient or absent thymus, referred to as athymia, have inherited a chromosome that is missing a key stretch of genes on a region called 22q11. Doctors believe perhaps 1/2000-1/4000 babies are born with some type of deletion in this region, which leads to a variable spectrum of disorders called 22q11 syndrome that can affect just about any part of the body, and can even cause learning disabilities and mental illness.

Individuals with one form of 22q11, called DiGeorge Syndrome, are particularly affected in the heart, thymus, and parathyroid glands. In the United States, about 20 infants are born per year with the “complete” and most severe form of DiGeorge Syndrome, who lack a thymus altogether, and have severely depressed numbers of T cells for fighting infections. Without medical intervention, this condition is usually fatal by 24 months of age.

Optimism and Setback                                                                  

Although there are no therapies approved by the Food and Drug Administration (FDA) for pediatric athymia, Dr. Mary Louise Markert at Duke University and Enzyvant, Inc. have been pioneering an experimental approach to treat children with complete DiGeorge syndrome.

In this procedure, discarded thymic tissues are collected from infants undergoing cardiac surgery, where some of the thymus needs to be removed in order for the surgeon to gain access to the heart. These tissues are processed to remove potentially harmful donor T cells and then transplanted into the thigh of an athymic DiGeorge patient.

Results from early clinical trials seemed promising, with more than 70% of patients surviving, including several who are now ten years post-transplant. Based on those results, in June of 2019 Enzyvant applied to the FDA for a Biologics License Application (BLA), which is needed to be able to sell the therapy in the US. Unfortunately, only a few months later, Enzyvant announced that the FDA had declined to approve the BLA due to manufacturing concerns.

While it may be possible to address these issues in time, the need to step back to the drawing board was a devastating blow to the DiGeorge Community, who have waited decades for a promising treatment to emerge on the horizon.

New Opportunities

Despite the setback, there is reason to hope. In early 2019, CIRM granted a “Quest” Award to team of investigators at Stanford University to develop a novel stem cell based approach for treating thymic deficiency. Co-led by Katja Weinacht, a pediatric hematologist/oncologist, and Vittorio Sebastiano, a stem cell expert and developmental biologist, the team’s strategy is to coax induced pluripotent stem cells (iPS) in the laboratory to differentiate into thymic tissue, which could then be transplanted into patients using the route pioneered by Duke and Enzyvant.

Katja Weinacht: Photo courtesy Stanford Children’s Health

The beauty of this new approach is that pluripotent stem cells are essentially immortal in culture, providing an inexhaustible supply of fresh thymic cells for transplant, thereby allowing greater control over the quality and consistency of donor tissues. A second major advantage is the possibility of using pluripotent cells from the patient him/herself as the source, which should be perfectly immune-matched and alleviate the risk of rejection and autoimmunity that comes with use of donated tissues.

Vittorio Sebastiano: Photo courtesy Stanford

Sounds easy, so what are the challenges? As with many regenerative medicine approaches, the key is getting a pluripotent stem cell to differentiate into the right type of cells in the lab, which is a very different environment than what cells experience naturally when they develop in the context of an embryo and womb, where many cells are interacting and providing complex, instructive cues to one another. The precise factors and timing all need to be worked out and in most cases, this is done with an incomplete knowledge of human development.

A second challenge relates to using cells from DiGeorge patients to produce thymic tissue, which are missing several genes on their 22nd chromosome and will likely require sophisticated genetic engineering to restore this ability.

Fortunately, Drs. Weinacht and Sebastiano are up to the challenge, and have already made progress in differentiating human induced pluripotent stem cells (iPS) into thymic lineage intermediates that appear to be expressing the right proteins at the right time. They plan to combine these cells with engineered materials to create a three-dimensional (3D) tissue that more closely resembles an authentic organ, and which can be tested for functionality in athymic mice.

There is more work to be done, but these advances, along with continued technological improvements and renewed efforts from Enzyvant, could forge a path to the clinic and  lead to a brighter future for patients suffering from congenital athymia and other forms of thymic dysfunction.

 

Join us December 12th for our Facebook Live Event – Ask the Stem Cell Experts

Several weeks ago, we asked all of you to submit questions related to stem cell research in order to get them answered by experts in the field right here in our office.

Your responses have been remarkable and we have gotten some really great questions we are excited to answer in live time. These questions ranged from the impact stem cell research has had on various disease areas to differentiating legitimate clinical trials from sham treatments being offered by predatory stem cell clinics.

For those of you that might have missed the previous announcement, this is all happening in a special Facebook Live “Ask the Stem Cell Team” event on Thursday, December 12th from 10.30am to 11.30am PDT. Just tune in to our Facebook page at that date and time listed for a live video streaming!

We will do our best to answer all the questions that were submitted to us. Additionally, for those who did not get a chance to email us, you can also submit questions in the comments section of the Facebook live event in real time. If we do not get to your question, don’t worry! We will answer it in a blog at a later date.

As a preview of this event, we wanted to showcase some of the questions submitted to us that will be answered in live time. You’ll have to wait until next week to get the answers so be sure to tune in!

Question

1. What are the obstacles to using partial cellular reprogramming to return people’s entire bodies to a youthful state?

2. What’s going on with Stanford’s stem cell trials for stroke?

3. I am a stroke survivor; will stem cell treatment able to restore my motor skills?

4. Could stem cells help hemorrhagic stroke patients as well?

5. Can stem cells possibly help with my vision issues?

6. Is there any stem cell therapy for optical nerve damage?

7. When will jCyte publish their Phase IIb clinical trial results?

8. What advances have been made using stem cells for the treatment of Type 2 Diabetes?

9. Is there any news on clinical trials for spinal cord injury?

10. Now that the Brainstorm ALS trial is finished looking for new patients, do you have any idea how it’s going and when can we expect to see results?

11. Are there treatments for Autism or Fragile X Syndrome using stem cells?

12. What is happening with Parkinson’s research?

13. Any plans for Huntington’s?

14. What practical measures are being taken to address unethical practitioners whose bad surgeries are giving stem cell advances a bad reputation and are making forward research difficult?

15. I’m curious if adipose stem cell being used at clinics at various places in the country is helpful or beneficial?

16. Do stem cells have benefits for patients going through chemotherapy and radiation therapy?

17. Is it possible to use a technique developed to fight one disease to also fight another?

18. Is there any concern that CIRM’s lack of support in basic research will hamper the amount of new approaches that can reach clinical stages?

19. What is the future of the use of CRISPR/Cas9 in clinical trials in California and globally?

20. Explain the differences between gene therapy and stem cell therapy?

21. Currently, how can the outcome of CIRM stem cell medicine projects and clinical trials be soundly interpreted when their stem cell-specific doses are not known?

22. Is there any research on using stem cells to increase the length of long bones in people?

Researchers create a better way to grow blood stem cells

UCLA’s Dr. Hanna Mikkola and Vincenzo Calvanese, lead scientists on the study. Photo courtesy UCLA

Blood stem cells are a vital part of us. They create all the other kinds of blood cells in our body and are used in bone marrow transplants to help people battling leukemia or other blood cancers. The problem is growing these blood stem cells outside the body has always proved challenging. Up till now.

Researchers at UCLA, with CIRM funding, have identified a protein that seems to play a key role in helping blood stem cells renew themselves in the lab. Why is this important? Because being able to create a big supply of these cells could help researchers develop new approaches to treating a wide array of life-threatening diseases.

One of the most important elements that a stem cell has is its ability to self-renew itself over long periods of time. The problem with blood stem cells has been that when they are removed from the body they quickly lose their ability to self-renew and die off.

To discover why this is the case the team at the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA analyzed blood stem cells to see which genes turn on and off as those cells turn into other kinds of blood cells – red, white and platelets. They identified one gene, called MLLT3, which seemed to play a key role in helping blood stem cells self-renew.

To test this finding, the researchers took blood stem cells and, in the lab, inserted copies of the MLLT3 gene into them. The modified cells were then able to self-renew at least 12 times; a number far greater than in the past.

Dr. Hanna Mikkola, a senior author of the study says this finding could help advance the field:

“If we think about the amount of blood stem cells needed to treat a patient, that’s a significant number. But we’re not just focusing on quantity; we also need to ensure that the lab-created blood stem cells can continue to function properly by making all blood cell types when transplanted.”

Happily, that seemed to be the case. When they subjected the MLLT3-enhanced blood stem cells to further analysis they found that they appeared to self-renew at a safe rate and didn’t multiply too much or mutate in ways that could lead to leukemia or other blood cancers.

The next steps are to find more efficient and effective ways of keeping the MLLT3 gene active in blood stem cells, so they can develop ways of using this finding in a clinical setting with patients.

Their findings are published in the journal Nature.

Breaking bad news to stem cell researchers

It’s never easy to tell someone that they are too late, that they missed the deadline. It’s particularly hard when you know that the person you are telling that to has spent years working on a project and now needs money to take it to the next level. But in science, as in life, it’s always better to tell people what they need to know rather than what they would like to hear.

And so, we have posted a notice on our website for researchers thinking about applying for funding that, except in a very few cases, they are too late, that there is no money available for new projects, whether it’s Discovery, Translational or Clinical.

Here’s that notice:

CIRM anticipates that the budget allocation of funds for new awards under the CIRM clinical program (CLIN1, CLIN2 and CLIN3) may be depleted within the next two to three months. CIRM will accept applications for the monthly deadline on June 28, 2019 but will suspend application submissions after that date until further notice. All applicants should note that the review of submitted applications may be halted at any point in the process if funds are depleted prior to completion of the 3-month review cycle. CIRM will notify applicants of such an occurrence. Therefore, submission and acceptance of an application to CIRM does not guarantee the availability of funds or completion of a review cycle.

The submission of applications for the CIRM/NHLBI Cure Sickle Cell Initiative (CLIN1 SCD, CLIN2 SCD) are unaffected and application submissions for this program will remain open.

We do, of course, have enough money set aside to continue funding all the projects our Board has already approved, but we don’t have money for new projects (except for some sickle cell disease projects).

In truth our funding has lasted a lot longer than anyone anticipated. When Proposition 71 was approved the plan was to give CIRM $300 million a year for ten years. That was back in 2004. So what happened?

Well, in the early years stem cell science was still very much in its infancy with most of the work being done at a basic or Discovery level. Those typically don’t require very large sums so we were able to fund many projects without hitting our $300m target. As the field progressed, however, more and more projects were at the clinical trial stage and those need multiple millions of dollars to be completed. So, the money went out faster.

To date we have funded 55 clinical trials and our early support has helped more than a dozen other projects get into clinical trials. This includes everything from cancer and stroke, to vision loss and diabetes. It’s a good start, but we feel there is so much more to do.

Followers of news about CIRM know there is talk about a possible ballot initiative next year that would provide another $5.5 billion in funding for us to help complete the mission we have started.

Over the years we have built a pipeline of promising projects and without continued support many of those projects face a difficult future. Funding at the federal level is under threat and without CIRM there will be a limited number of funding alternatives for them to turn to.

Telling researchers we don’t have any money to support their work is hard. Telling patients we don’t have any money to support work that could lead to new treatments for them, that’s hardest of all.

The stem cell conference where even the smartest people learn something

A packed house for the opening keynote address at ISSCR 2019

At first glance, a scientific conference is not the place you would think about going to learn about how to run a political or any other kind of campaign. But then the ISSCR Annual Meeting is not your average conference. And that’s why CIRM is there and has been going to these events for as long as we have been around.

For those who don’t know, ISSCR is the International Society for Stem Cell Research. It’s the global industry representative for the field of stem cell research. It’s where all the leading figures in the field get together every year to chart the progress in research.

But it’s more than just the science that gets discussed. One of the panels kicking off this year’s conference was on ‘Why is it Important to Communicate with Policy Makers, the Media and the Public?” It was a wide-ranging discussion on the importance of learning the best ways for the scientific community to explain what it is they do, why they do it, and why people should care.

Sean Morrison

Sean Morrison, a former President of ISSCR, talked about his experience trying to pass a bill in Michigan that would enable scientists to do embryonic stem cell research. At the time CIRM was spending millions of dollars funding scientists in California to create new lines of embryonic stem cells; in Michigan anyone doing the same could be sent to prison for a year. He said the opposition ran a fear-based campaign, lying about the impact the bill would have, that it would enable scientists to create half man-half cow creatures (no, really) or human clones. Learning to counter those without descending to their level was challenging, but ultimately Morrison was successful in overcoming opposition and getting the bill passed.

Sally Temple

Sally Temple, of the Neural Stem Cell Institute, talked about testifying to a Congressional committee about the importance of fetal tissue research and faced a barrage of hostile questions that misrepresented the science and distorted her views. In contrast Republicans on the committee had invited a group that opposed all fetal tissue research and fed them a bunch of softball questions; the answers the group gave not only had no scientific validity, they were just plain wrong. Fortunately, Temple says she had done a lot of preparation (including watching two hours Congressional hearings on C-SPAN to understand how these hearings worked) and had her answers ready. Even so she said one of the big lessons she stressed is the need to listen to what others are saying and respond in ways that address their fears and don’t just dismiss them.

Other presenters talked about their struggles with different issues and different audiences but similar experiences; how do you communicate clearly and effectively. The answer is actually pretty simple. You talk to people in a way they understand with language they understand. Not with dense scientific jargon. Not with reams of data. Just by telling simple stories that illustrate what you did and who it helped or might help.

The power of ISSCR is that it can bring together a roomful of brilliant scientists from all over the world who want to learn about these things, who want to be better communicators. They know that much of the money for scientific research comes from governments or state agencies, that this is public money, and that if the public is going to continue to support this research it needs to know how that money is being spent.

That’s a message CIRM has been promoting for years. We know that communicating with the public is not an option, it’s a responsibility. That’s why, at a time when the very notion of science sometimes seems to be under attack, and the idea of public funding for that science is certainly under threat, having meetings like this that brings researchers together and gives them access to new tools is vital. The tools they can “get” at ISSCR are ones they might never learn in the lab, but they are tools that might just mean they get the money needed to do the work they want to.

CIRM Board Approves New Clinical Trial for Rare Childhood Disease

Today the governing Board of the California Institute for Regenerative Medicine (CIRM) approved a grant of almost $12 million to Dr. Stephanie Cherqui at the University of California, San Diego (UCSD) to conduct a clinical trial for treatment of cystinosis.

This award brings the total number of CIRM funded clinical trials to 55. 

Cystinosis is a rare disease that primarily affects children and young adults, and leads to premature death, usually in early adulthood.  Patients inherit defective copies of a gene called CTNS, which results in abnormal accumulation of an amino acid called cystine in all cells of the body.  This buildup of cystine can lead to multi-organ failure, with some of earliest and most pronounced effects on the kidneys, eyes, thyroid, muscle, and pancreas.  Many patients suffer end-stage kidney failure and severe vision defects in childhood, and as they get older, they are at increased risk for heart disease, diabetes, bone defects, and neuromuscular defects.  There is currently a drug treatment for cystinosis, but it only delays the progression of the disease, has severe side effects and is expensive.

Dr. Cherqui’s clinical trial will use a gene therapy approach to modify a patient’s own blood stem cells with a functional version of the defective CTNS gene. Based on pre-clinical data, the approach is to reintroduce the corrected stem cells into the patient to give rise to blood cells that will reduce cystine buildup in affected tissues.  

Because this is the first time this approach has been tested in patients, the primary goal of the clinical trial is to see if the treatment is safe.  In addition, patients will be monitored for improvements in the symptoms of their disease.  This award is in collaboration with the University of California, Los Angeles which will handle the manufacturing of the therapy.

CIRM has also funded the preclinical work for this study, which involved completing the testing needed to apply to the Food and Drug Administration (FDA) for permission to start a clinical trial in people.

“CIRM has funded 24 clinical stage programs utilizing cell and gene medicine approaches to date,” says Maria T. Millan, M.D., the President and CEO of CIRM.  “This project continues to broaden the scope of unmet medical need we can impact with these types of approaches.”

Stanford study successful in transplant of mismatched stem cells, tissue in mice

Dr. Irv Weissman at Stanford University

A transplant can be a lifesaving procedure for many people across the United States. In fact, according to the Health Resources & Services Administration, 36,528 transplants were performed in 2018. However, as of January 2019, the number of men, women, and children on the national transplant waiting list is over 113,000, with 20 people dying each day waiting for a transplant and a new person being added to the list every 10 minutes.

Before considering a transplant, there needs to be an immunological match between the donated tissue and/or blood stem cells and the recipient. To put it simply, a “match” indicates that the donor’s cells will not be marked by the recipient’s immune cells as foreign and begin to attack it, a process known as graft-versus-host disease. Unfortunately, these matches can be challenging to find, particularly for some ethnic minorities. Often times, immunosuppression drugs are also needed in order to prevent the foreign cells from being attacked by the body’s immune system. Additionally, chemotherapy and radiation are often needed as well.

Fortunately, a CIRM-funded study at Stanford has shown some promising results towards addressing the issue of matching donor cells and recipient. Dr. Irv Weissman and his colleagues at Stanford have found a way to prepare mice for a transplant of blood stem cells, even when donor and recipient are an immunological mismatch. Their method involved using a combination of six specific antibodies and does not require ongoing immunosuppression.

The combination of antibodies did this by eliminating several types of immune cells in the animals’ bone marrow, which allowed blood stem cells to engraft and begin producing blood and immune cells without the need for continued immunosuppression. The blood stem cells used were haploidentical, which, to put it simply, is what naturally occurs between parent and child, or between about half of all siblings. 

Additional experiments also showed that the mice treated with the six antibodies could also accept completely mismatched purified blood stem cells, such as those that might be obtained from an embryonic stem cell line. 

The results established in this mouse model could one day lay the foundation necessary to utilize this approach in humans after conducting clinical trials. The idea would be that a patient that needs a transplanted organ could first undergo a safe, gentle transplant with blood stem cells derived in the laboratory from embryonic stem cells. The same embryonic stem cells could also then be used to generate an organ that would be fully accepted by the recipient without requiring the need for long-term treatment with drugs to suppress the immune system. 

In a news release, Dr. Weissman is quoted as saying,

“With support by the California Institute for Regenerative Medicine, we’ve been able to make important advances in human embryonic stem cell research. In the past, these stem cell transplants have required a complete match to avoid rejection and reduce the chance of graft-versus-host disease. But in a family with four siblings the odds of having a sibling who matches the patient this closely are only one in four. Now we’ve shown in mice that a ‘half match,’ which occurs between parents and children or in two of every four siblings, works without the need for radiation, chemotherapy or ongoing immunosuppression. This may open up the possibility of transplant for nearly everyone who needs it. Additionally, the immune tolerance we’re able to induce should in the future allow the co-transplantation of [blood] stem cells and tissues, such as insulin-producing cells or even organs generated from the same embryonic stem cell line.”

The full results to this study were published in Cell Stem Cell.

Blood-brain barrier chip created with stem cells expands potential for personalized medicine

An Organ-Chip used in the study to create a blood-brain barrier (BBB).

The brain is a complex part of the human body that allows for the formation of thoughts and consciousness. In many ways it is the essence of who we are as individuals. Because of its importance, our bodies have developed various layers of protection around this vital organ, one of which is called the blood-brain barrier (BBB).

The BBB is a thin border of various cell types around the brain that regulate what can enter the brain tissue through the bloodstream. Its primary purpose is to prevent toxins and other unwanted substances from entering the brain and damaging it. Unfortunately this barrier can also prevent helpful medications, designed to fix problems, from reaching the brain.

Several brain disorders, such as Amyotrophic Lateral Sclerosis (ALS – also known as Lou Gehrig’s disease), Parkinson’s Disease (PD), and Huntington’s Disease (HD) have been linked to defective BBBs that keep out critical biomolecules needed for healthy brain activity.

In a CIRM-funded study, a team at Cedars-Sinai Medical Center created a BBB through the use of stem cells and an Organ-Chip made from induced pluripotent stem cells (iPSCs). These are a specific type of stem cells that can turn into any type of cell in the body and can be generated from a person’s own cells. In this study, iPSCs were created from adult blood samples and used to make the neurons and other supporting cells that make up the BBB. These cells were then placed inside an Organ-Chip which recreates the environment that cells normally experience within the human body.

Inside the 3-D Organ-Chip, the cells were able to form a BBB that functions as it does in the body, with the ability to block entry of certain drugs. Most notably, when the BBB was generated from cell samples of patients with HD, the BBB malfunctioned in the same way that it does in patients with the disease.

These findings expand the potential for personalized medicine for various brain disorders linked to problems in the BBB. In a press release, Dr. Clive Svendsen, director of the Cedars-Sinai Board of Governors Regenerative Medicine Institute and senior author of the study, was quoted as saying,

“The study’s findings open a promising pathway for precision medicine. The possibility of using a patient-specific, multicellular model of a blood barrier on a chip represents a new standard for developing predictive, personalized medicine.”

The full results of the study were published in the scientific journal Cell Stem Cell.

CIRM-funded clinical trial shows encouraging results for patients with chronic lymphocytic leukemia & mantle cell lymphoma

Illustration courtesy of Oncternal Therapeutics

I often joke that my job here at CIRM is to be the official translator for the stem cell agency. I have to translate complex science into everyday English that people without a science background – that includes me – can understand.

Think I’m joking? Try making sense of this.

See what I mean. If you are a scientist this is not only perfectly clear, it’s also quite exciting. But for the rest of us……..

Actually, it is really quite exciting news. It’s about a CIRM-funded clinical trial being run by Oncternal Therapeutics to treat people with chronic lymphocytic leukemia (CLL), a kind of cancer where our body makes too many white blood cells. The study is using a combination therapy of Cirmtuzumab (a monoclonal antibody named after us because we helped fund its development) and ibrutinib, a conventional therapy used to treat cancers like CLL.

Cirmtuzumab recognizes and then attaches itself to a protein on the surface of cancer stem cells that the cancer needs to survive and spread. This attachment disables the protein (called ROR1) which slows the growth of the leukemia and makes it more vulnerable to anti-cancer drugs like ibrutinib.

In this Phase 1/2 clinical trial 12 patients were given the combination therapy for 24 weeks or more, making them eligible to determine how effective, or ineffective, the therapy is:

  • 11 of the 12 patients had either a partial response – meaning a reduction in the amount of detectable cancer – or a complete response to the treatment – meaning no detectable cancer.
  • None of the patients saw their cancer spread or grow
  • Three of the patients completed a year of treatment and they all showed signs of a complete response including no enlarged lymph nodes and white blood cell counts in the normal range.  

The combination therapy is also being used to treat people with Mantle Cell Lymphoma (MCL), a rare but fast-growing form of blood cancer. The results from this group, while preliminary, are also encouraging. One patient, who had experienced a relapse following a bone marrow transplant, experienced a complete response after three months of cirmtuzumab and ibrutinib.  

The data on the clinical trial was presented at a poster session (that’s the poster at the top of this blog) at the annual meeting of the American Society of Clinical Oncology.

In a news release Dr. James Breitmeyer, the President & CEO of Oncternal, said the results are very encouraging:  

“These data presented today, taken together with an earlier Phase 1 study of cirmtuzumab as a monotherapy in relapsed/refractory CLL, give us increased confidence in the potential for cirmtuzumab as a treatment for patients with ROR1-expressing lymphoid malignancies, particularly in combination with ibrutinib as a potential treatment for patients with CLL and MCL. We believe that the data also help to validate the importance of ROR1 as a therapeutic target,”

CIRM funded clinical trial shows promising results for patients with blood cancers

An illustration of a macrophage, a vital part of the immune system, engulfing and destroying a cancer cell. Antibody 5F9 blocks a “don’t eat me” signal emitted from cancer cells.
Courtesy of Forty Seven, Inc.

Myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) are both types of blood cancers that can be difficult to treat. CIRM is funding Forty Seven, Inc. to conduct a clinical trial to treat patients with these blood cancers with an antibody called 5F9. CIRM has also given multiple awards prior to the clinical trial to help in developing the antibody.

Cancer cells express a signal known as CD47, which sends a “don’t eat me” message to macrophages, which are white blood cells that are part of the immune system designed to “eat” and destroy unhealthy cells. The antibody works by blocking the signal, enabling the body’s own immune system to detect and destroy the cancer cells.

In a press release, Forty Seven, Inc. announced early clinical results from their CIRM funded trial using the antibody to treat patients with AML and MDS. Some patients received just the antibody while others received the antibody in combination with azacitidine, a chemotherapy drug used to treat these cancers.

Here is a synopsis of the trial:

  • 35 patients treated in a Phase 1 clinical trial have been evaluated for a response assessment to-date.
  • 10 of these have MDS or AML and only received the 5F9 antibody.
  • 11 of these have higher-risk MDS and received the 5F9 antibody along with the chemotherapy drug azacitidine.
  • 14 of these have untreated AML and received the 5F9 antibody along with the chemotherapy drug azacitidine.

For the 11 patients with higher-risk MDS treated with the antibody and chemotherapy, they found that:

  • All 11 patients achieved an objective response rate (ORR), meaning that there was a reduction in tumor burden of a predefined amount.
  • Six of these patients achieved a complete response (CR), indicating a disappearance of all signs of cancer in response to treatment.

For the 14 patients with untreated AML treated with the antibody and chemotherapy, they found that:

  • Nine of these patients achieved an ORR.
  • Five of these nine patients achieved a CR.
  • Two of these nine patients achieved a morphologic leukemia-free state (MLFS), indicating the disappearance of all cells with formal and structural characteristics of leukemia, accompanied by bone marrow recovery, in response to treatment. 
  • The remaining five patients achieved stable disease (SD), meaning that the tumor is neither growing nor shrinking.

The results also showed that:

  • There was no evidence of increased toxicities when the antibody was used alongside the chemotherapy drugs, demonstrating tolerance and safety of the treatment.
  • No responding MDS or AML patient has relapsed or progressed on the antibody in combination with chemotherapy, with a median follow-up of 3.8 months.
  • The median time to response was rapid at 1.9 months.
  • Several patients have experienced deepening responses over time resulting in complete remissions. 

Based on the favorable results observed in this clinical trial to-date, expansion cohorts have been initiated, meaning that additional patients will be enrolled in a phase I trial. This will include patients with both higher-risk MDS and untreated AML as well as using the antibody in combination with chemotherapy.

In the press release, Dr. David Sallman, an investigator in the clinical trial, is quoted as saying,

“These new data for 5F9 show encouraging clinical activity in a broad population of patients with MDS and AML, who may be unfit for existing therapeutic options or at higher-risk for developing rapidly-advancing disease. Despite an evolving treatment landscape, physicians continue to seek new therapies for MDS and AML that can be used safely in combination with standard-of-care to help patients more rapidly achieve durable responses. To that end, I am excited to see meaningful clinical activity in a majority of patients treated with 5F9 in combination with azacitidine, with a median time to response of under two months and no relapses or progressions among responding patients.”