Irv Weissman

How a CIRM scholar helped create a life-saving COVID vaccine

/ Kevin McCormack / 1 Comment

Dr. Derrick Rossi might be the most famous man whose name you don’t recognize. Dr. Rossi is the co-founder of Moderna. Yes, that Moderna. The COVID-19 vaccine Moderna. The vaccine that in clinical trials proved to be around 95 percent effective against the coronavirus.

Dr. Rossi also has another claim to fame. He is a former CIRM scholar. He did some of his early research, with our support, in the lab of Stanford’s Dr. Irv Weissman.

So how do you go from a lowly post doc doing research in what, at the time, was considered a rather obscure scientific field, to creating a company that has become the focus of the hopes of millions of people around the world?  Well, join us on Wednesday, January 27th at 9am (PST) to find out.

CIRM’s President and CEO, Dr. Maria Millan, will hold a live conversation with Dr. Rossi and we want you to be part of it. You can join us to listen in, and even post questions for Dr. Rossi to answer. Think of the name dropping credentials you’ll get when say to your friends; “Well, I asked Dr. Rossi about that and he told me…..”

Being part of the conversation is as simple as clicking on this link:

After registering, you will receive a confirmation email containing information about joining the webinar.

We look forward to seeing you there.

Meet the people who are changing the future

/ Kevin McCormack / 2 Comments
Kristin MacDonald

Every so often you hear a story and your first reaction is “oh, I have to share this with someone, anyone, everyone.” That’s what happened to me the other day.

I was talking with Kristin MacDonald, an amazing woman, a fierce patient advocate and someone who took part in a CIRM-funded clinical trial to treat retinitis pigmentosa (RP). The disease had destroyed Kristin’s vision and she was hoping the therapy, pioneered by jCyte, would help her. Kristin, being a bit of a pioneer herself, was the first person to test the therapy in the U.S.

Anyway, Kristin was doing a Zoom presentation and wanted to look her best so she asked a friend to come over and do her hair and makeup. The woman she asked, was Rosie Barrero, another patient in that RP clinical trial. Not so very long ago Rosie was legally blind. Now, here she was helping do her friend’s hair and makeup. And doing it beautifully too.

That’s when you know the treatment works. At least for Rosie.

There are many other stories to be heard – from patients and patient advocates, from researchers who develop therapies to the doctors who deliver them. – at our CIRM 2020 Grantee Meeting on next Monday September 14th Tuesday & September 15th.

It’s two full days of presentations and discussions on everything from heart disease and cancer, to COVID-19, Alzheimer’s, Parkinson’s and spina bifida. Here’s a link to the Eventbrite page where you can find out more about the event and also register to be part of it.

Like pretty much everything these days it’s a virtual event so you’ll be able to join in from the comfort of your kitchen, living room, even the backyard.

And it’s free!

You can join us for all two days or just one session on one day. The choice is yours. And feel free to tell your friends or anyone else you think might be interested.

We hope to see you there.

Stem Cell All-Stars, All For You

/ Kevin McCormack / Leave a comment

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Dr. Larry Goldstein, UC San Diego

It’s not often you get a chance to hear some of the brightest minds around talk about their stem cell research and what it could mean for you, me and everyone else. That’s why we’re delighted to be bringing some of the sharpest tools in the stem cell shed together in one – virtual – place for our CIRM 2020 Grantee Meeting.

The event is Monday September 14th and Tuesday September 15th. It’s open to anyone who wants to attend and, of course, it’s all being held online so you can watch from the comfort of your own living room, or garden, or wherever you like. And, of course, it’s free.

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Dr. Daniela Bota, UC Irvine

The list of speakers is a Who’s Who of researchers that CIRM has funded and who also happen to be among the leaders in the field. Not surprising as California is a global center for regenerative medicine. And you will of course be able to post questions for them to answer.

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Dr. Deepak Srivastava, Gladstone Institutes

The key speakers include:

Larry Goldstein: the founder and director of the UCSD Stem Cell Program talking about Alzheimer’s research

Irv Weissman: Stanford University talking about anti-cancer therapies

Daniela Bota: UC Irvine talking about COVID-19 research

Deepak Srivastava: Gladsone Institutes, talking about heart stem cells

Other topics include the latest stem cell approaches to COVID-19, spinal cord injury, blindness, Parkinson’s disease, immune disorders, spina bifida and other pediatric disorders.

You can choose one topic or come both days for all the sessions. To see the agenda for each day click here. Just one side note, this is still a work in progress so some of the sessions have not been finalized yet.

And when you are ready to register go to our Eventbrite page. It’s simple, it’s fast and it will guarantee you’ll be able to be part of this event.

We look forward to seeing you there.

Big time validation for early support

/ Kevin McCormack / Leave a comment

It’s not every day that a company and a concept that you helped support from the very beginning gets snapped up for $4.9 billion. But that’s what is happening with Forty Seven Inc. and their anti-cancer therapies. Gilead, another California company by the way, has announced it is buying Forty Seven Inc. for almost $5 billion.

The deal gives Gilead access to Forty Seven’s lead antibody therapy, magrolimab, which switches off CD47, a kind of “do not eat me” signal that cancer cells use to evade the immune system.

CIRM has supported this program from its very earliest stages, back in 2013, when it was a promising idea in need of funding. Last year we blogged about the progress it has made from a hopeful concept to an exciting therapy.

When Forty Seven Inc. went public in 2018, Dr. Irv Weissman, one of the founders of the company, attributed a lot of their success to CIRM’s support.

Dr. Irv Weissman

“The story of the funding of this work all of the way to its commercialization and the clinical trials reported in the New England Journal of Medicine is simply this: CIRM funding of a competitive grant took a mouse discovery of the CD47 ‘don’t eat me’ signal through all preclinical work to and through a phase 1 IND with the FDA. Our National Institutes of Health (NIH) did not fund any part of the clinical trial or preclinical run up to the trial, so it is fortunate for those patients and those that will follow, if the treatment continues its success in larger trials, that California voters took the state’s right action to fund research not funded by the federal government.”

Dr. Maria Millan, CIRM’s President & CEO, says the deal is a perfect example of CIRM’s value to the field of regenerative medicine and our ability to work with our grantees to make them as successful as possible.

“To say this is incredible would be an understatement! Words cannot describe how excited we are that this novel approach to battling currently untreatable malignancies has the prospect of making it to patients in need and this is a major step. Speaking on behalf of CIRM, we are very honored to have been a partner with Forty Seven Inc. from the very beginning.

CIRM Senior Science Officer, Dr. Ingrid Caras, was part of the team that helped a group of academic scientists take their work out of the lab and into the real world.

“I had the pleasure of working with and helping the Stanford team since CIRM provided the initial funding to translate the idea of developing CD47 blockade as a therapeutic approach. This was a team of superb scientists who we were fortunate to work closely with them to navigate the Regulatory environment and develop a therapeutic product. We were able to provide guidance as well as funding and assist in the ultimate success of this project.”

Forty Seven Inc. is far from the only example of this kind of support and collaboration. We have always seen ourselves as far more than just a funding agency. Money is important, absolutely. But so too is bringing the experience and expertise of our team to help academic scientists take a promising idea and turn it into a successful therapy.

After all that’s what our mission is, doing all we can to accelerate stem cell therapies to patients with unmet medical needs. And after a deal like this, Forty Seven Inc. is definitely accelerating its work.

Saying goodbye to a good friend and a stem cell pioneer: Karl Trede

/ Kevin McCormack / 2 Comments

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Sometimes even courage and determination are not enough. Karl Trede had courage and determination in droves as he fought a 12 year battle against cancer. He recently lost that battle. But he remains an inspiration for all who knew him.

I got to know Karl for our 2016 Annual Report. Karl had been diagnosed with throat cancer in 2006. He underwent surgery to remove his vocal cords and the cancer seemed to be in remission. But then it returned, this time having spread to his lungs. His doctors said they had pretty much run out of options but would Karl consider trying something new, something no one else had tried before; stem cells.

Karl told me he didn’t hesitate.

“I said “sure”. I don’t believe I knew at the time that I was going to be the first one but I thought I’d give it a whirl. It was an experience for me. It was eye opening. I wasn’t real concerned about being the first, I figured I was going to have to go someday so I guess if I was the first person and something really went wrong then they’d definitely learn something. So, to me, that was kind of worth my time.”

Happily nothing went wrong and the team behind the therapy (Forty Seven Inc.) definitely learned something, they learned a lot about the correct dosage for patients; invaluable information in treating future patients.

Karl’s cancer was held at bay and he was able to do the one thing that brought him more pleasure than anything else; spend time with his family, his wife Vita, their four sons and their families. He doted on his grand kids and got to see them grow, and they got to know him.

Recently the cancer returned and this time there was no holding it at bay. To the end Karl remained cheerful and positive.

KARL poster

In our office is a huge poster of Karl with the words “Every Moment Counts” at the bottom. It’s a reminder to us why we come to work every day, why the people at Forty Seven Inc. and all the other researchers we support work so hard for years and years; to try and give people like Karl a few extra moments with his family.

At the top of the poster the word “Courage” is emblazoned across it. Karl has a huge smile on his face. Karl was certainly courageous, a stem cell pioneer willing to try something no one else ever had. He was also very modest.

Here is Karl speaking to our governing Board in December 2016

When I spoke to him in 2016, despite all he had gone through in his fight against cancer, he said he had no regrets:

“I consider myself very fortunate. I’m a lucky guy.”

Those of us who got to spend just a little time with Karl know that we were the lucky ones.

Our hearts go out to his family and friends for their loss.

 

 

Early CIRM support helps stem cell pioneer develop promising new therapy for cancer

/ Kevin McCormack / Leave a comment

Irv Weissman

Irv Weissman, Ph.D., Photo: courtesy Stanford University

When you get praise from someone who has been elected to the National Academy of Sciences and has been named California Scientist of the Year you know you must be doing something right.

That’s how we felt the other day when Irv Weissman, Director of the Stanford Institute of Stem Cell Biology and Regenerative Medicine, issued a statement about how important the support of CIRM was in advancing his research.

The context was the recent initial public offering (IPO) of Forty Seven Inc.. a company co-founded by Dr. Weissman. That IPO followed news that two Phase 2 clinical trials being run by Forty Seven Inc. were demonstrating promising results against hard-to-treat cancers.

Dr. Weissman says the therapies used a combination of two monoclonal antibodies, 5F9 from Forty Seven Inc. and Rituximab (an already FDA-approved treatment for cancer and rheumatoid arthritis) which:

“Led to about a 50% overall remission rate when used on patients who had relapsed, multi-site disease refractory to rituximab-plus-chemotherapy. Most of those patients have shown a complete remission, although it’s too early to tell if this is complete for life.”

5F9 attacks a molecule called CD47 that appears on the surface of cancer cells. Dr. Weissman calls CD47 a “don’t eat me signal” that protects the cancer against the body’s own immune system. By blocking the action of CD47, 5F9 strips away that “don’t eat me signal” leaving the cancer vulnerable to the patient’s immune system. We have blogged about this work here and here.

The news from these trials is encouraging. But what was gratifying about Dr. Weissman’s statement is his generosity in sharing credit for the work with CIRM.

Here is what he wrote:

“What is unusual about Forty Seven is that not only the discovery, but its entire preclinical development and testing of toxicity, etc. as well as filing two Investigational New Drug [IND] applications to the Food and Drug Administration (FDA) in the US and to the MHRA in the UK, as well as much of the Phase 1 trials were carried out by a Stanford team led by two of the discoverers, Ravi Majeti and Irving Weissman at Stanford, and not at a company.

The major support came from the California Institute of Regenerative Medicine [CIRM], funded by Proposition 71, as well as the Ludwig Cancer Research Foundation at the Ludwig Center for Cancer Stem Cell Research at Stanford. CIRM will share in downstream royalties coming to Stanford as part of the agreement for funding this development.

This part of the state initiative, Proposition 71, is highly innovative and allows the discoverers of a field to guide its early phases rather than licensing it to a biotech or a pharmaceutical company before the value and safety of the discovery are sufficiently mature to be known. Most therapies at early-stage biotechs are lost in what is called the ‘valley of death’, wherein funding is very difficult to raise; many times the failure can be attributed to losing the expertise of the discoverers of the field.”

Dr. Weissman also had praise for CIRM’s funding model which requires companies that produce successful, profitable therapies – thanks to CIRM support – to return a portion of those profits to California. Most other funding agencies don’t have those requirements.

“US federal funds, from agencies such as the National Institutes of Health (NIH) similarly support discovery but cannot fund more than a few projects to, and through, early phase clinical trials. And, under the Bayh-Dole Act, the universities keep all of the equity and royalties derived from licensing discoveries. In that model no money flows back to the agency (or the public), and nearly a decade of level or less than level funding (at the national level) has severely reduced academic research. So this experiment of funding (the NIH or the CIRM model) is now entering into the phase that the public will find out which model is best for bringing new discoveries and new companies to the US and its research and clinical trials community.”

We have been funding Dr. Weissman’s work since 2006. In fact, he was one of the first recipients of CIRM funding.  It’s starting to look like a very good investment indeed.

 

The story behind the book about the Stem Cell Agency

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Don Reed at his book launch: Photo by Todd Dubnicoff

WHY I WROTE “CALIFORNIA CURES”  By Don C. Reed

It was Wednesday, June 13th, 2018, the launch day for my new book, “CALIFORNIA CURES: How the California Stem Cell Research Program is Fighting Your Incurable Disease!”

As I stood in front of the audience of scientists, CIRM staff members, patient advocates, I thought to myself, “these are the kind of people who built the California stem cell program.” Wheelchair warriors Karen Miner and Susan Rotchy, sitting in the front row, typified the determination and resolve typical of those who fought to get the program off the ground. Now I was about to ask them to do it one more time.

My first book about CIRM was “STEM CELL BATTLES: Proposition 71 and Beyond. It told the story of  how we got started: the initial struggles—and a hopeful look into the future.

Imagine being in a boat on the open sea and there was a patch of green on the horizon. You could be reasonably certain those were the tops of coconut trees, and that there was an island attached—but all you could see was a patch of green.

Today we can see the island. We are not on shore yet, but it is real.

“CALIFORNIA CURES” shows what is real and achieved: the progress the scientists have made– and why we absolutely must continue.

For instance, in the third row were three little girls, their parents and grandparents.

One of them was Evangelina “Evie” Vaccaro, age 5. She was alive today because of CIRM, who had funded the research and the doctor who saved her.

Don Reed and Evie and Alysia

Don Reed, Alysia Vaccaro and daughter Evie: Photo by Yimy Villa

Evie was born with Severe Combined Immunodeficiency (SCID) commonly called the “bubble baby” disease. It meant she could never go outside because her immune system could not protect her.  Her mom and dad had to wear hospital masks to get near her, even just to give her a hug.

But Dr. Donald Kohn of UCLA operated on the tiny girl, taking out some of her bone marrow, repairing the genetic defect that caused SCID, then putting the bone marrow back.

Today, “Evie” glowed with health, and was cheerfully oblivious to the fuss she raised.

I was actually a little intimidated by her, this tiny girl who so embodied the hopes and dreams of millions. What a delight to hear her mother Alysia speak, explaining  how she helped Evie understand her situation:  she had “unicorn blood” which could help other little children feel better too.

This was CIRM in action, fighting to save lives and ease suffering.

If people really knew what is happening at CIRM, they would absolutely have to support it. That’s why I write, to get the message out in bite-size chunks.

You might know the federal statistics—133 million children, women and men with one or more chronic diseases—at a cost of $2.9 trillion dollars last year.

But not enough people know California’s battle to defeat those diseases.

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Adrienne Shapiro at the book launch: Photo by Todd Dubnicoff

Champion patient advocate Adrienne Shapiro was with us, sharing a little of the stress a parent feels if her child has sickle cell anemia, and the science which gives us hope:  the CIRM-funded doctor who cured Evie is working on sickle cell now.

Because of CIRM, newly paralyzed people now have a realistic chance to recover function: a stem cell therapy begun long ago (pride compels me to mention it was started by the Roman Reed Spinal Cord Injury Research Act, named after my son), is using stem cells to re-insulate damaged nerves in the spine.  Six people were recently given the stem cell treatment pioneered by Hans Keirstead, (currently running for Congress!)  and all six experienced some level of recovery, in a few cases regaining some use of their arms hands.

Are you old enough to remember the late Annette Funicello and Richard Pryor?  These great entertainers were stricken by multiple sclerosis, a slow paralysis.  A cure did not come in time for them. But the international cooperation between California’s Craig Wallace and Australia’s Claude Bernard may help others: by  re-insulating MS-damaged nerves like what was done with spinal cord injury.

My brother David shattered his leg in a motorcycle accident. He endured multiple operations, had steel rods and plates inserted into his leg. Tomorrow’s accident recovery may be easier.  At Cedars-Sinai, Drs. Dan Gazit and Hyun Bae are working to use stem cells to regrow the needed bone.

My wife suffers arthritis in her knees. Her pain is so great she tries to make only one trip a day down and up the stairs of our home.  The cushion of cartilage in her knees is worn out, so it is bone on bone—but what if that living cushion could be restored? Dr. Denis Evseenko of UCLA is attempting just that.

As I spoke, on the wall behind me was a picture of a beautiful woman, Rosie Barrero, who had been left blind by retinitis pigmentosa. Rosie lost her sight when her twin children were born—and regained it when they were teenagers—seeing them for the first time, thanks to Dr. Henry Klassen, another scientist funded by CIRM.

What about cancer? That miserable condition has killed several of my family, and I was recently diagnosed with prostate cancer myself. I had everything available– surgery, radiation, hormone shots which felt like harpoons—hopefully I am fine, but who knows for sure?

Irv Weissman, the friendly bear genius of Stanford, may have the answer to cancer.  He recognized there were cancer stem cells involved. Nobody believed him for a while, but it is now increasingly accepted that these cancer stem cells have a coating of protein which makes them invisible to the body’s defenses. The Weissman procedure may peel off that “cloak of invisibility” so the immune system can find and kill them all—and thereby cure their owner.

What will happen when CIRM’s funding runs out next year?

If we do nothing, the greatest source of stem cell research funding will be gone. We need to renew CIRM. Patients all around the world are depending on us.

The California stem cell program was begun and led by Robert N. “Bob” Klein. He not only led the campaign, was its chief writer and number one donor, but he was also the first Chair of the Board, serving without pay for the first six years. It was an incredible burden; he worked beyond exhaustion routinely.

Would he be willing to try it again, this time to renew the funding of a successful program? When I asked him, he said:

“If California polls support the continuing efforts of CIRM—then I am fully committed to a 2020 initiative to renew the California Institute for Regenerative Medicine (CIRM).”

Shakespeare said it best in his famous “to be or not to be” speech, asking if it is “nobler …to endure the slings and arrows of outrageous fortune, or to take arms against a sea of troubles—and by opposing, end them”.

Should we passively endure chronic disease and disability—or fight for cures?

California’s answer was the stem cell program CIRM—and continuing CIRM is the reason I wrote this book.

Don C. Reed is the author of “CALIFORNIA CURES: How the California Stem Cell Program is Fighting Your Incurable Disease!”, from World Scientific Publishing, Inc., publisher of the late Professor Stephen Hawking.

For more information, visit the author’s website: www.stemcellbattles.com

 

Seeing is believing. Proof a CIRM-funded therapy is making a difference

/ Kevin McCormack / Leave a comment

ThelmaScreenShotFB

Thelma, participant in the CAMELLIA clinical trial

You have almost certainly never heard of Thelma, or met her, or know anything about her. She’s a lady living in England who, if it wasn’t for a CIRM-funded therapy, might not be living at all. She’s proof that what we do, is helping people.

Thelma is featured in a video about a treatment for acute myeloid leukemia, one of the most severe forms of blood cancer. Thelma took part in a clinical trial, called CAMELLIA, at Oxford Cancer Centre in Oxford, UK. The clinical trial uses a therapy that blocks a protein called CD47 that is found on the surface of cancer cells, including cancer stem cells which can evade traditional therapies. The video was shot to thank the charity Bloodwise for raising the funds to pay for the trial.

Prof. Paresh Vyas of Oxford University, who was part of the clinical trial team that treated Thelma, says patients with this condition face long odds.

“Patients with acute myeloid leukemia have the most aggressive blood cancer. We really haven’t had good treatments for this condition for the last 40 years.”

While this video was shot in England, featuring English nurses and doctors and patients, the therapy itself was developed here in California, first at Stanford University under the guidance of Irv Weissman and, more recently, at Forty Seven Inc. That company is now about to test their approach in a CIRM-funded clinical trial here in the US.

This is an example of how CIRM doesn’t just fund research, we invest in it. We help support it at every stage, from the earliest research through to clinical trials. Without our early support this work may not have made it this far.

The Forty Seven Inc. therapy uses the patient’s own immune system to help fight back against cancer stem cells. It’s looking very promising. But you don’t have to take our word for it. Take Thelma’s.

Stem Cell RoundUp: CIRM Clinical Trial Updates & Mapping Human Brain

/ Todd Dubnicoff / Leave a comment

It was a very CIRMy news week on both the clinical trial and discovery research fronts. Here are some the highlights:

Stanford cancer-fighting spinout to Genentech: ‘Don’t eat me’ – San Francisco Business Times

Ron Leuty, of the San Francisco Business Times, reported this week on not one, but two news releases from CIRM grantee Forty Seven, Inc. The company, which originated from discoveries made in the Stanford University lab of Irv Weissman, partnered with Genentech and Merck KGaA to launch clinical trials testing their drug, Hu5F9-G4, in combination with cancer immunotherapies. The drug is a protein antibody that blocks a “don’t eat me” signal that cancer stem cells hijack into order to evade destruction by a cancer patient’s immune system.

Genentech will sponsor two clinical trials using its FDA-approved cancer drug, atezolizumab (TECENTRIQ®), in combination with Forty Seven, Inc’s product in patients with acute myeloid leukemia (AML) and bladder cancer. CIRM has invested $5 million in another Phase 1 trial testing Hu5F9-G4 in AML patients. Merck KGaA will test a combination treatment of its drug avelumab, or Bavencio, with Forty-Seven’s Hu5F9-G4 in ovarian cancer patients.

In total, CIRM has awarded Forty Seven $40.5 million in funding to support the development of their Hu5F9-G4 therapy product.

Novel regenerative drug for osteoarthritis entering clinical trials – The Scripps Research Institute

The California Institute for Biomedical Research (Calibr), a nonprofit affiliate of The Scripps Research Institute, announced on Tuesday that its CIRM-funded trial for the treatment of osteoarthritis will start treating patients in March. The trial is testing a drug called KA34 which prompts adult stem cells in joints to specialize into cartilage-producing cells. It’s hoped that therapy will regenerate the cartilage that’s lost in OA, a degenerative joint disease that causes the cartilage that cushions joints to break down, leading to debilitating pain, stiffness and swelling. This news is particularly gratifying for CIRM because we helped fund the early, preclinical stage research that led to the US Food and Drug Administration’s go-ahead for this current trial which is supported by a $8.4 million investment from CIRM.

And finally, for our Cool Stem Cell Image of the Week….

Genetic ‘switches’ behind human brain evolution – Science Daily

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This artsy scientific imagery was produced by UCLA researcher Luis del la Torre-Ubieta, the first author of a CIRM-funded studied published this week in the journal, Cell. The image shows slices of the mouse (bottom middle), macaque monkey (center middle), and human (top middle) brain to scale.

The dramatic differences in brain size highlights what sets us humans apart from those animals: our very large cerebral cortex, a region of the brain responsible for thinking and complex communication. Torre-Ubieta and colleagues in Dr. Daniel Geschwind’s laboratory for the first time mapped out the genetic on/off switches that regulate the growth of our brains. Their results reveal, among other things, that psychiatric disorders like schizophrenia, depression and Attention-Deficit/Hyperactivity Disorder (ADHD) have their origins in gene activity occurring in the very earliest stages of brain development in the fetus. The swirling strings running diagonally across the brain slices in the image depict DNA structures, called chromatin, that play a direct role in the genetic on/off switches.

Second “Don’t Eat Me” Signal Identified in Cancer Cells, Points to New Immunotherapies

/ Todd Dubnicoff / 1 Comment

When the immune system comes up as a topic in everyday conversation, it’s usually related to fighting off a cold or flu. While our immune cells certainly do detect and neutralize invading bacteria and viruses, they also play a critical role in killing abnormal, cancerous cells from within our bodies.

“Don’t Eat Me” Signal 101
A white blood cell called a macrophage (macro = “big”; phage = “eater”) is part of the so-called innate immune system and acts as a first line of defense by patrolling our organs and gobbling up infected as well as cancerous cells (see macrophages in action in the cool video below).

Unfortunately, cancer cells possess the ability to cloak themselves and escape a macrophage’s engulfing grasp. Nearly all cancer cells carry a protein called CD47 on their surface. When CD47 binds to a protein called SIRPalpha on the surface of macrophages, a “don’t eat me” signal is triggered and the macrophage ignores the cancer cell.

Stanford researcher Irv Weissman and his team discovered this “don’t eat me” signal several years ago and showed that adding an antibody protein that binds tightly to CD47 interferes with the CD47/SIRPalpha signal. As a result, the anti-CD47 antibody deactivates the cancer cell’s “don’t eat me” signal and restores the macrophage’s ability to detect and kill the cancer cells.

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CD47 protein on surface of cancer cells triggers “don’t eat me signal” which can be blocked with anti-CD47 antibody. Image: Acrobiosystems

Because CD47 is found on the surface of most cancer cells, this anti-CD47 antibody represents an exciting new strategy for targeting cancer stem cells – the cells thought to maintain cancer growth and cause tumor relapse – in a wide variety of cancers. In fact, CIRM has provided funding for three clinical trials, one sponsored by Stanford University and two by Forty-Seven Inc. (a company that was spun out of Stanford), that are testing anti-CD47 therapy for the treatment of the blood cancer acute myeloid leukemia (AML), as well as colon cancer and other solid tumors.

“Reaching Clinical Trials” does not equal “The Research is Done”
Although these clinical trials are underway, the Weissman team continues to seek new insights related to blocking the CD47 “don’t eat me” signal. They observed that although anti-CD47 led to increased macrophage-induced killing of most cancer cell samples tested, some were resistant to anti-CD47 and remained cloaked from macrophages. And even the cancer cells that did respond to the antibody varied widely in the amount of increased killing by macrophages.

These results suggested that alternate processes may exist that allow some cancers to evade macrophages even when the CD47 “don’t eat me” signal is blocked. In a report published this week in Nature Immunology, the researchers report the identification of a second, independent “don’t eat me” signal, which may lead to more precise methods to disarm a cancer’s evasiveness.

To track down this alternate “don’t eat me” signal, they looked for, but didn’t find, correlations between specific types of cancer cells and the cancer’s resistance to anti-CD47 treatment.  So instead they analyzed surface proteins found on the various cancer cell samples and found that cancer cells that had high levels of MHC (Major Histocompatibility Complex) class I proteins were more likely to be resistant to anti-CD47 antibodies.

A Second “Don’t Eat Me” Signal
MHC class I proteins help another arm of the immune system, the adaptive immune response, detect what’s going inside a cell. They are found on nearly all cells and display, at the cell surface, bits of proteins sampled from inside the cell. If cells of the adaptive immune response, such as T or B cells, recognize one of those protein bits as abnormal or foreign, efficient killing mechanisms are kicked into high gear to destroy those cells.

But in the case of cancers cells, the MHC class I protein are harnessed as a “don’t eat me” signal by binding to a protein called LILRB1 on macrophages. When either the MHC class I proteins or LILRB1 were blocked, the “don’t eat me” signal was lifted and restored the macrophages’ ability to kill the cancer cells both in petri dish samples as well as in mice that carried human cancers.

Graduate student and co-lead author Amira Barkal described in a press release the impact of blocking both “don’t eat me” signals at the same time:

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Amira Barkal

“Simultaneously blocking both these pathways in mice resulted in the infiltration of the tumor with many types of immune cells and significantly promoted tumor clearance, resulting in smaller tumors overall. We are excited about the possibility of a double- or perhaps even triple-pronged therapy in humans in which we combine multiple blockades to cancer growth.”

The Big Picture for Cancer Immunotherapies
Because MHC protein class I proteins play an important role in stimulating immune cells called T cells to kill cancer cells as part of the adaptive immune response, the level of MHC protein on an individual patient’s cancer cells could serve as an indicator, or “biomarker”, for what type of cancer therapy to pursue.  The big picture implications of this idea are captured in the press release:

“Understanding the balance between adaptive and innate immunity is important in cancer immunotherapy. For example, it’s not uncommon for human cancer cells to reduce the levels of MHC class 1 on their surfaces to escape destruction by T cells. People with these types of tumors may be poor candidates for cancer immunotherapies meant to stimulate T cell activity against the cancer. But these cells may then be particularly vulnerable to anti-CD47 treatment, the researchers believe. Conversely, cancer cells with robust MHC class 1 on their surfaces may be less susceptible to anti-CD47.”