Hematologic malignancies are cancers that affect the blood, bone marrow and lymph nodes and include different forms of leukemia and lymphoma. Current treatments can be effective, but in those patients that do not respond, there are few treatment options. Today, the governing Board of the California Institute for Regenerative Medicine (CIRM) approved investing $4.1 million in a therapy aimed at helping patients who have failed standard therapy.
Dr. Ezra Cohen, at the University of California San Diego, and Oncternal Therapeutics are targeting a protein called ROR1 that is found in B cell malignancies, such as leukemias and lymphomas, and solid tumors such as breast, lung and colon. They are using a molecule called a chimeric antigen receptor (CAR) that can enable a patient’s own T cells, an important part of the immune system, to target and kill their cancer cells. These cells are derived from a related approach with an antibody therapy that targets ROR1-binding medication called Cirmtuzumab, also created with CIRM support. This CAR-T product is designed to recognize and kill cancer stem cells that express ROR1.
This is a late-stage preclinical project so the goal is to show they can produce enough high-quality cells to treat patients, as well as complete other regulatory measures needed for them to apply to the US Food and Drug Administration (FDA) for permission to test the therapy in a clinical trial in people.
If given the go-ahead by the FDA the therapy will target patients with chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL) and acute lymphoblastic leukemia (ALL).
“CAR-T cell therapies represent a transformational advance in the treatment of hematologic malignancies,” says Dr. Maria T. Millan, CIRM’s President and CEO. “This approach addresses the need to develop new therapies for patients whose cancers are resistant to standard chemotherapies, who have few therapeutic options and a very poor chance or recovery.”
Dr. Theodore Nowicki, physician in the division of pediatric hematology/oncology at UCLA. Photo courtesy of Milo Mitchell/UCLA Jonsson Comprehensive Cancer Center
The
governing Board of the California Institute for Regenerative Medicine (CIRM) awarded
two grants totaling $11.15 million to carry out two new clinical trials. These latest additions bring the total number
of CIRM funded clinical trials to 53.
$6.56 Million was awarded to Rocket Pharmaceuticals, Inc. to conduct a clinical trial for
treatment of infants with Leukocyte Adhesion Deficiency-I (LAD-I)
LAD-I is a rare pediatric disease caused a mutation in a specific gene that
affects the body’s ability to combat infections. As a result, infants with
severe LAD-I are often affected immediately after birth. During infancy, they
suffer from recurrent life-threatening bacterial and fungal infections that
respond poorly to antibiotics and require frequent hospitalizations. Those that survive infancy experience
recurrent severe infections, with mortality rates for severe LAD-I at 60-75%
prior to the age of two and survival very rare beyond the age of five.
Rocket Pharmaceuticals, Inc. will test a treatment that uses a patient’s own blood stem cells and inserts a functional version of the gene. These modified stem cells are then reintroduced back into the patient that would give rise to functional immune cells, thereby enabling the body to combat infections.
The award is in
the form of a CLIN2 grant, with the goal of conducting a clinical trial to
assess the safety and effectiveness of this treatment in patients with LAD-I.
This project
utilizes a gene therapy approach, similar to that of three other clinical
trials funded by CIRM and conducted at UCLA by Dr. Don Kohn, for X-linked
Chronic Granulomatous Disease, an inherited immune deficiency “bubble baby”
disease known as ADA-SCID, and Sickle Cell Disease.
An additional $4.59 million was awarded to Dr.
Theodore Nowicki at UCLA to conduct a clinical trial for treatment of patients
with sarcomas and other advanced solid tumors. In 2018 alone, an
estimated 13,040 people were diagnosed with soft tissue sarcoma (STS) in the
United States, with approximately 5,150 deaths.
Standard of care treatment for sarcomas typically consists of surgery,
radiation, and chemotherapy, but patients with late stage or recurring tumor
growth have few options.
Dr. Nowicki and his team will genetically modify peripheral blood stem cells (PBSCs) and peripheral blood monocular cells (PBMCs) to target these solid tumors. The gene modified stem cells, which have the ability to self-renew, provide the potential for a durable effect.
This award is
also in the form of a CLIN2 grant, with the goal of conducting a clinical trial
to assess the safety of this rare solid tumor treatment.
This project will add to CIRM’s portfolio in stem cell approaches for difficult to treat cancers. A previously funded a clinical trial at UCLA uses this same approach to treat patients with multiple myeloma. CIRM has also previously funded two clinical trials using different approaches to target other types of solid tumors, one of which was conducted at Stanford and the other at UCLA. Lastly, two additional CIRM funded trials conducted by City of Hope and Poseida Therapeutics, Inc. used modified T cells to treat brain cancer and multiple myeloma, respectively.
“CIRM has funded 23 clinical stage programs utilizing cell and gene medicine approaches” says Maria T. Millan, M.D., the President and CEO of CIRM. “The addition of these two programs, one in immunodeficiency and the other for the treatment of malignancy, broaden the scope of unmet medical need we can impact with cell and gene therapeutic approaches.”
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.
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:
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.”
In 2004, when 59 percent of California voters approved the creation of CIRM, our state embarked on an unprecedented experiment: providing concentrated funding to a new, promising area of research. The goal: accelerate the process of getting therapies to patients, especially those with unmet medical needs.
Having 10 potential treatments expected to be approved for clinical trials by the end of this year is no small feat. Indeed, it is viewed by many in the industry as a clear acceleration of the normal pace of discovery. Here are our first 10 treatments to be approved for testing in patients.
HIV/AIDS. The company Calimmune is genetically modifying patients’ own blood-forming stem cells so that they can produce immune cells—the ones normally destroyed by the virus—that cannot be infected by the virus. It is hoped this will allow the patients to clear their systems of the virus, effectively curing the disease.
Spinal cord injury patient advocate Katie Sharify is optimistic about the clinical trial led by Asterias Biotherapeutics.
Spinal Cord Injury. The company Asterias Biotherapeutics uses cells derived from embryonic stem cells to heal the spinal cord at the site of injury. They mature the stem cells into cells called oligodendrocyte precursor cells that are injected at the site of injury where it is hoped they can repair the insulating layer, called myelin, that normally protects the nerves in the spinal cord.
Heart Disease. The company Capricor is using donor cells derived from heart stem cells to treat patients developing heart failure after a heart attack. In early studies the cells appear to reduce scar tissue, promote blood vessel growth and improve heart function.
Solid Tumors. A team at the University of California, Los Angeles, has developed a drug that seeks out and destroys cancer stem cells, which are considered by many to be the reason cancers resist treatment and recur. It is believed that eliminating the cancer stem cells may lead to long-term cures.
Leukemia. A team at the University of California, San Diego, is using a protein called an antibody to target cancer stem cells. The antibody senses and attaches to a protein on the surface of cancer stem cells. That disables the protein, which slows the growth of the leukemia and makes it more vulnerable to other anti-cancer drugs.
Sickle Cell Anemia. A team at the University of California, Los Angeles, is genetically modifying a patient’s own blood stem cells so they will produce a correct version of hemoglobin, the oxygen carrying protein that is mutated in these patients, which causes an abnormal sickle-like shape to the red blood cells. These misshapen cells lead to dangerous blood clots and debilitating pain The genetically modified stem cells will be given back to the patient to create a new sickle cell-free blood supply.
Solid Tumors. A team at Stanford University is using a molecule known as an antibody to target cancer stem cells. This antibody can recognize a protein the cancer stem cells carry on their cell surface. The cancer cells use that protein to evade the component of our immune system that routinely destroys tumors. By disabling this protein the team hopes to empower the body’s own immune system to attack and destroy the cancer stem cells.
Diabetes. The company Viacyte is growing cells in a permeable pouch that when implanted under the skin can sense blood sugar and produce the levels of insulin needed to eliminate the symptoms of diabetes. They start with embryonic stem cells, mature them part way to becoming pancreas tissues and insert them into the permeable pouch. When transplanted in the patient, the cells fully develop into the cells needed for proper metabolism of sugar and restore it to a healthy level.
HIV/AIDS. A team at The City of Hope is genetically modifying patients’ own blood-forming stem cells so that they can produce immune cells—the ones normally destroyed by the virus—that cannot be infected by the virus. It is hoped this will allow the patients to clear their systems of the virus, effectively curing the disease
Blindness. A team at the University of Southern California is using cells derived from embryonic stem cell and a scaffold to replace cells damaged in Age-related Macular Degeneration (AMD), the leading cause of blindness in the elderly. The therapy starts with embryonic stem cells that have been matured into a type of cell lost in AMD and places them on a single layer synthetic scaffold. This sheet of cells is inserted surgically into the back of the eye to replace the damaged cells that are needed to maintain healthy photoreceptors in the retina.
The Stem Cellar 